TOPIC THREE

COORDINATION

Concept of Coordination.

Coordination is the working together of the various organs of an organism in a systematic manner so as to produce @ proper response to the stimuli. Without coordination the body becomes disorderly and it may fail to function properly The Ways in Which Coordination is Brought About The coordination in simple multicellular animals takes place through nervous systemonly The control and coordination in higher animals called vertebrates (including humanbeings) takes

place through nervous system as well as hormonal system called endocrinesystem. Coordination in plants is under the control of hormones. Al the living organisms (plants and animals) respond and react to changes in the environment around them. ‘The changes in the environment to which the organisms respond and react are called stimuli (singular: stimulus). The living organisms show response to stimuli such as light, heat, cold, sound, smell, taste, touch, pressure, pain,water, and force of gravity, ete. The ability to

perceive, interpret and respond to stimuli is called iritability or sensitivity There are two types of stimuli: external and intemal, Extemal stimuli are associated with the surrounding environment such as wind temperature, light, pressure, toueh, water and gravity Internal stimuli occur within the organism, for example, a decrease or an increase in the amount of water and glucose in the blood, When an organism detects a stimulus, it initiates a response. A response is a

behavioural,physiological or muscular activity initiated by a stimulus. For example, if a man touches a very hot utensil accidentally, he quickly pulls his hand away from the hot utensil Heere,heat is the stimulus and the man reacts (responds) by moving his hand away from the hot utensil Similarly, when the sun is bright, we close our eyes. In this ease, light isthe stimulus and we react by closing our eyes. Likewise, when the amount of water in the blood drops, the

pituitary gland secretes an anti-iuretic hormone (ADE) which stimulates the reabsorption of water in the kidneys Multicellular organisms detect stimuli through sense organs called receptors. A receptor is & sense organ (¢-g. eye) or sensory nerve ending (e.g. im the skin or internal organ) which receives stimuli and sets nervous impulses. Impulses are electrical transmissions or chemical stimuli that are sent from the receptor to the coordinating system in the organism. The organs that respond to

the stimuli are ealled effectors. A coordinator is an organ (e.g. the brain and spinal cord) that receives messages ffom the receptors.translates them and sends the information back to on effector for action An effector is a muscle or gland which receives impulses from nerves, brain or spinal cord and responds to them. Response is the end-action, such as a muscle contracting to cause the movement of the arm ‘The diagram below illustrates the five components of

coordination in mammals, Nervous Coordination in Human , Neurons ‘The Structure of Motor Sensory and Relay Neurons Neurones Neurones are nerve cells. They earry information as tiny electrical signals, A neuroneconsists of a cell body (with a nucleus and eytoplasm), dendrites that earry electricatimpulses to the cell, and a Tong axon thet carries the impulses away from the cell. Theaxon of one neurone and the dendrites of the next neurone do not actually touch eachother, The gap between neurones is

called the synapse Structure and functions of neurones The diagram below shows @ typical neurone: in this ease, a motor neurone. It has tinybranches at each end (dendrites) and a long fibre (axon) that carries the signals or nervousimpulses. The axon is surrounded by 2 fatty layer known as the myelin sheath. Thishelps to protect the neurone and allow impulses to travel faster. ‘The sheath 1s produces bySchawan cells. The mycln sheath has

nodes (Nodes of Ranvier) that speed uptransmission of nervous impulses. The cell body consists of eytoplasm enclosing thenucleus. There are also other organelles in the eytoplasm such as mitochondria thatsupply energy to for metabolic functions.

Synapses Where two neurones meet, there isa tiny gap called 2 synapse. Signals cross this gapusing ‘chemicals (neurotransmitters) released by a neurone. When the chemical diffusesacross the gap it makes the next neurone transmit an electrical signal. The transmission ofnervous impulses across synapses occurs thus: 1, Anelectrical impulse travels along an axon, 2 This triggers the nerveending of a neuron to release chemical messengers

calledneurotransmniters

• These chemicals diffuse across the synapse (the gap) and bind with receptarmolecules on the

membrane of the next neuron.

• The receptor molecules on the second neuron bind only to the specific chemicalsreleased from

the first neuron. This stimulates the second neuron to transmit theeleetrical impulse cytoplasm anne dendrite nuiclews Node of Ranvier Shawnn cell axon y a nerve ending myelin sheath soma (cell body)

Structure of neurone

There are three types of neuroncs namely motor neurone, sensory neurone and relay(or A motor neurone is a nerve cell that transmits impulses from the central nervous system(CNS) to.

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Central Nervous System (CNS)

The Nervous System

The human brain is a specialized organ that is ultimately responsible for all thought sensory information or speak and understand language can be damaged as well The cerebrum is the largest portion of the brain, and contains tools which are responsiblefor most of the brain's function. It is divided into four sections: the temporal lobe, theoccipital lobe, parietal lobe and frontal lobe.

Parietal Lobe: Located in the cerebral hemisphere, this lobe focuses on comprehension. Visual functions, language, reading, internal stimuli, tactile sensation and sensorycomprehension are monitored here Temporal Lobe: The temporal lobe controls visual and auditory memories. It ineludesareas that help manage some speech and hearing capabilities, behavioural elements, andlanguage. It is located in the cerebral hemisphere

Occipital Lobe: the occipital lobe is located in the cerebral hemisphere in the back of thehead. It helps to control vision Cerebellum This is commonly referred to as "the little brainl, The cerebellum controls essential bodyfimetions such as balance, posture and coordination, allowing humans to move properlyand maintain their posture Limbie system The limbie system contains glands which help relay emotions: Many hormonal responsesthat the

body generates are initiated in this area. The limbic system includes theamygdala, hippocampus, hypothalarnus and thalamus Amygdala: The amygdala hetps the body responds to emotions, memories and fear.

Hippocampus: This portion of the brain is used for leaming memory, specificallyconverting temporary memories into permanent memories which can be stored within thebrain Hypothalamus; The hypothalamus region of the brain controls mood, thirst, hunger andtemperature, It also contains glands which control the hormonal processes throughout thebody.

Thalaimus: The thalamus is located in the centre ofthe brain. It helps to conirol theattention span, sensing pain and monitors input that moves in snd out ofthe brain to keeptrack of the sensations the body is Feeling Brain stem All basic life functions originate in the beain stem, including heartbeat, blood pressureand breathing. In humans, this area contains the medulla, midbrain and pons Midbrain: This part of the brain helps regulate body movement, vision and hearing

Pans: The pons interprets information that is used in sensory analysis or motor control The pons also éreates the level of consciousness necessary for sleep. Medulla: The medulla or medulla oblongata is an essential portion of the brain sternwhich maintains vital body Functions such as the hear rate and breathing.

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& we he: 4a mA \ eee he a i The Structure ofthe Spinal Cord and Brain Spinal cord Signals arising in the motor areas of the brain travel back down thecord and leave in the motor

• The spinal cord also acts as 2 minor coordinating centre responsible for some simplereflexes like

the withdrawal reflex The intermediate neurones carrying impulses to and from specific receptors and effectorsare srouped together in spinal tracts The diagram shows vatious sections ofthe spinal cord and the functions of each section

Peripheral Nervous System (PNS)

The Meaning of Peripheral Nervous System

The peripheral nervous system is made up of @ network of nerves linking various parts ofthe body to the brain and spinal cord. It ineludes the cranial nerves, spinal nerves andtheir roots and branches, peripheral nerves, and neuromuscular junctions.

The peripheral nervous system (PNS) has two components: the somatic nervous systemand the autonomic nervous system, The PNS consists of all of the nerves that lie outsidethe brain and spinal cord.

The Components of the Peripheral Nervous System and Their Functions The somatic nervous system is made up of nerves that connect to voluntary skeletalmuscles and to sensory receptors. It is composed of afferent nerves that carryinformation to the central nervous system (spinal cord) and efferent nerves that carryneural impulses away from the central nervous system. This system is responsible for theinvohintary control of the skeletal muscles,

bones and sense organs The autonomic nervous system is further subdivided into sympathetic andparasympathetie nervous system.

• The sympathetic nervous system activates the fight or fight’ response under suddenor stressful

cireurmstances, for instances by raising the heart rate and dilating thepupils action, and the other repairing the body afterward.

Reflex Action

‘ordinates the response. But sometimes a very quick response 1s needed, one thatdocs not need the The reflex action is a rapid, involuntary response to a certain stimulus. The route that isfollowed sive frig ot Hoe Without thinking ej, The sam below shows escaped fete

eran SO \ z r ent Pra an ae )}) @ } foes stoi LA rT min y vonnril oot” — ~ Reflex action of a hand being withdrawn from the a flame 1 receptor detects a stimulus ~ change in the environment

• sensory neurone sends signal 1o relay neurone
• motor neurone sends signal to effector
• effector produces a response

The above provess appears to be a long one but, in realty, the process takes a very short time: I happens within seconds, The way the iris in our eye adjusts the size ofthe pupil in response to bright or dim light is also a reflex action. It happens without our thinking and beyond our control The Neuronic Path of a Reflex Action A reflex action can either be simple or conditioned reflex Simple reflex section AAn example ofa simple reflex found in humans is the pupil reflex, where the pupil of theeye gets

larger in dim light and smaller in bright light.The eye needs to control the amount of light entering it in different light conditions. Indim conditions, more light is allowed to enter so that a clear image can be formed on theretina. In bright conditions, less light is allowed to enter so that the retina is not damaged.

Conditioned reflex action A conditioned reflex is some action or feeling that is earned in response to a specific situation or stimulus A Russian scientist called Pavlov trained dogs to expect food whenever he rang a bell. The dogs eventually produced saliva when they heard the bell ring, The dog salivates naturally when given food. Pavlov rung a bell every time the dogs were to be given food After much repetition the

dogs salivated when they heard the bell ringing, even when there was no food. This is an

example of conditioned reflex

The dogs were conditioned to salivate when the bell rang. A ringing bell does not normally cause salivation in dogs. However, when the ringing bell becomes a secondary stimulus, it does cause salivation, even though the dog will not be able to eat the bell as food This is now called a conditioned reflex. In a conditioned reflex the final response(salivation) hos no direct connection with the stimulus (ringing bell).

vAnother example of @ conditioned (learned) reflex is when the driver eomes across ahurdle on the road such as a ditch or a pedestrian, In such circumstances, the first thingthe driver will do is to move his leg towards the brake pedal to apply the brakes. He haslearned to do this aetion for s0 long that he finds himself applying the brake in any ofsuch circumstances, The Difference between Simple Reflex and Conditioned Reflex Action

Differences between conditioned reflex action and simple reflex action Conditioned reflex Simple reflex 1 ttinvolves more than one stimuli Requires only one stimulus 2 Involves the brain Mostly involve the spinal cord 3 Itis an immediate action (no time to learn) Itis an immediate action (no time to learn) 4 tis acquired in one's life Itis inborn Modifying a reflex response In some cireumstances the brain can modify a reflex response. It does this by sending zn impulse

along @ motor ncuron of the reflex are, ‘his enables us, for example, to hold a hot dinner plate when normally we would drop it

Sense Organs

The Meaning of a Sense Organ Sense organs are organs of the body that detect and respond to changes in the environment (stimuli so as to survive

Types of Sense Organs and Their Relative Position

There are five sense organs in our body: eyes,ears, nose, tongue and skin. We receive a variety of information from the cavironmentaround us through the sense organs. The sense organs contain receptors. A receptor is acell (or 2 group of cells) in a sense organ which is sensitive to a particular type ofstimulus (or a particular type of change in the environment) such as light sound, smelljaste, heat, pressure, ete, The different sense organs contain receptors. for

detectingdifferent stimuli The eyes have light receptors (which can detect light), ears have sound receptors (whichcan detect sound), nose has smell receptors (which can detect smell), tongue has tastereceptors (which can detect taste) whereas skin has receptors for detecting touch, pressure, heat (or cold) and pai, ete.

The Structure of Fach Sense Organ

The human eye The eye is the organ for vision. The eye is one of the most complex parts of the body: The different parts of the eye allow the eye to take in light and perceive objects around usin the proper colour, detail and depth. This allows people to make more informeddecisions about their environment. Ifa portion of the eye becomes damaged, you may nothe able to see effectively You may even lose your vision completely Parts of the eye and their functions here are several

physical and chemical elements that make up the eye. The table belowshows different parts of the human eye and their functions Eye part Description and function(s)Comea ‘The comea is the ‘outer, transparent covering of the eye. This layerproteeis the eye fiom elements that could cause damage to the innerparts of the eye, The cornea also helps to focus light on the retina at theback of the eye Sclera The sclera is commonly referred to as the "“white* of the eye. It protectsthe eye

and maintains the shape of the eye ball.Pupil The pupil appears as a black dot in the middle of the eye. This blackarea is actually a hole that takes in light to enable the eye focus on theobjects: aqueous vitreous humnete humour el sclera ed ” laf \ choroid cornea Yer \ retina , to: \ pupil {tens ee ee : oe ee (Garter te mada . AS ‘ iris NAG blind spot « optic nerve suspensory \SX ~ ligaments x Per ciliary body Internal structure of the Inman eve

Byepart ——_‘Deseription and function(s) from clements that could cause damage to the inner parts of the eye. The cornea also helps to focus light on the retina atthe baek of the eye The sclera is commonly referted to as the "white" of the eye. It protects the eye and Selera ‘maintains the shape of the eve ball ‘The pupil appears as a black dot in the middle of the eye. This black area is actually Pupil a hole that takes in light to enable the eye focus on the objects in front of it The

pupil, thus, controls the amount of light that enters the eye. ‘The iris contains the pigment which gives the eye its colour. It has radial and cireular ‘muscles that control the size of the pupil by dilation and contraction. This allows the Iris eye to take in more or less light depending on how bright it is around. The ins allows more light into the eye when the environment is dark and allows less light into the eye when the environment is bright

Gaijin This is a membrane that covers the comea. It is thin and transparent so as to allow “onjunetiva . light to enter the eye It is tough and protects the eye from mechanical damage These glands are Iocated on the outer comer oF each eye. They produce tears which Lacrimal help moisten the eye when it becomes dry, and flush out particles which irritate the glands eve. As tears flush out potentially dangerous irritants, it becomes easier to focus

properly ‘This is a transparent structure filled with a jelly-like substance. The lens focuses light into the retina, It is held in place by the suspensory ligaments attached to the Lens ciliary muscles, which allow the lens to change shape depending on the amount of light entering the eye. Through the eiliary muscles, the lens becomes thicker to focus fon nearby objects and thinner to facus on distant objects , Retina is the sensory tissue that lines the inner layer of the eye. It is the layer of the

Retina eye where images are formed, and itis connected to the optic nerve that transmits the images to the brain to be interpreted. The retina is made up millions of photoreceptors known as reds and canes Ciliary body, also called ciliary muscles, is ring-shaped tissue which holds and Ciliary body controls the movement of the eye lens, and thus, it helps to control the shape of the Jens The ciliary body contains glandular cells which secrete the aqueous humour

The suspensory ligaments attach the lens to the ciliary muscles. When the ciliary muscles contract, they pull the suspensory ligaments and the lens gets Jong and thin SMepEROTY sg siGosnmoide ray of ight Foe stant objec: Whin the eiiary miles relay, Memes, ere i ese teton on the sespensory Bgaentyand ae lens. becninesimare spherical in shape. This enables the accommodation of light rays from near objects.

The choroid lies between the retina and the sclera, which provides blood supply to Choroid the eye. Just like any other portion of the body, the blocd supply gives nutrition to the various parts ofthe eye ‘The vitreous humour is the gel located inthe back ofthe eye which helps it hold its Vuecous shape, This gel takes in nutrients from the ciliary body, aqueous humour and the retinal vessels so the eye can remain healthy, The gel in the vitceous humour is

humour transparent to allow light get tothe retina nd also helps maintain the shape of the eyeball The agucous humour is a watery substance tha fills the eye. The aqueous humour ives the front of the eye its shape as well as nourishes the comea and lens. This ane liquid is drained through the Schlemm-canal so that any build-up in the eye can be removed. Ifthe person’s aqueous humour is not draining properly, s/he can develop

slaucoma Optic nerve is a cranial nerve which contains sensory neurones. The neurones Optic nerve transmit impulses fiom the rods and cones of the retin to the brain fr interpretation The optic nerve exits the eye at the blind spot It 1s located at the point where the optic nerve leaves the eye. The blind spot is not Blind spot sensitive to light because it has no rods or cones.

The fovea is the ceniremost part of the macula This tiny area is responsible for our central, sharpest vision. A healthy fovea is important for reading, watching Fovea television, driving, and other activities that require the ability to see detail *Small and highly sensitive part of the retina responsible for detailed central vision, The retina is the very centre of the macula Adaptations of the eye to its functions

The eye is adapted to its functions by possessing the following features:

• Conjunetiva, comea and lens are transparent to allow light to pass through them.
• Selerotic layer is made up of (collagen) fibres, it maintains shape of eyeball/protectsthe eye from

mechanical damage

• Comea is transparent and curved thus refracts light rays and allows light to passthrough,
• Choroid (a layer of. tissue) has black or dark pigments that prevent internalreflections of light in

the eve

• The eye contains blood vessels in the choroids layer that supply oxygen and nutrienisto the eye,

tiving the eye energy to perform its funtion, and removes the metaboliewastes from the eye

• Retina is made of photoreesptors known as rods and cones, which trap light rays toenable the eye

to do its Fanetion of vision,

• Yellow spot (fovea) has the highest concentration of cones for accurate and sharp.central vision
• Optic nerve has sensory neurones for transmission of nerve impulses to the brain

(forintespretation)

• Lens is biconvex and made up of elastic, transparent material which adjusts to focusfar or near

objects and allows light rays to pass through. 10, Suspensory ligaments are fibrous to hold the Lens in place

• The ciliary body contains ciliary muscles which are contractile to for controlling thecurvature

and hence focal length of the lens, It also contains glands that secrete theaqueous and vitreous humours

• The iris is opaque and contractile for controlling the smount of light entering the eye(by

adjusting the size of the pupil) 13, Ocular muscles coordinate eye movement so that both eyes can follow a movingobject together.

• The eyelid covers an eye and prevents it from mechanical damage and invasion byforeign

bodies

• Eye lashes help to prevent dust and small inseets or particles from entering the eyeby trapping

them on their hairs 16, The presence of aqueous and vitreous humours helps the eye to bend light raysioward retina to process the signal and send impulse to the brain The Functions of Sense Organs and their Adaptive Features Adaptations of the eye to its functions The eye is adapted to its Functions by possessing the following features.

• Conjumetiva, comea and lens are transparent to allow light to pass through thom.
• Sclerotic layer is made up of (collagen) fibres; it maintains shape of eyebal /protectsthe eye from

mechanical damage

• Comea is transparent and curved thus refracts light rays and allows light to passthrough,
• Choroid (a layer of a tissue) has black or dark pigments that prevent internalreflections of light in

the eye.

• The eye contains blood vessels in the choroids layer that supply oxygen and nutrienisto the eye,

ving the eye energy to perform its funtion, and removes the meteboliewastes from the eye

• Retina is made of photoreesptors known as rods and cones. which trap light rays toenable the eye

to do its Function of vision

• Yellow spot (fovea) has the highest concentration of cones for accurate and shasp.central vision
• Optic nerve has sensory neurones for transmission of nerve impulses to the brain

(forinterpretation)

• Lens is biconvex and made up of clastic, transparent material which adjusts to focusfar or near

objects and allows light rays to pass through. 10, Suspensory ligaments are fibrous to hold the lens in place 11… The eiliary body contains eiliary muscles which are contractile to for controlling thecurvature and hence focal length of the lens. It also contains glands that secrete theaqueous and vitreous humours,

• The iis 1s opaque and contrectile for controlling the amount of light entering the eye(by

adjusting the size of the pupil) 13, Ocular muscles coordinate eye movement so that both eyes can follow a movingobject together. 14, The eyelid covers an eye and prevents it from mechanical damage and invasion byforeign bodies

• Eye lashes help to prevent dust and small insects or particles from entering the eyeby trapping

thom on their hatrs.

• The presence of aqueous and vitreous humours helps the eye to bend light raystoward retina to

process the signal and send impulse to the brain The human car The ear is the organ of hearing and maintaining balance and posture. The outer ear protrudes away from the head and is shaped like a cup to direct sound waves toward the tympanic membrane, which transmits vibrations to the inner ear through a series of small bones (ossicles) in the middle ear called the malleus, ineus and stapes. The inner ear, orcochlea. 18a spiral-shaped

chamber covered intemally by nerve fibres that react to the vibrations and transmit impulses to the brain via the auditory nerve. The brain combines the input of our two ears to determine the direction and distance of sounds.

The inner ear has a vestibular system formed by three semicircular canals that area proximately at right angles to each other and which are responsible for the sense of balance and spatial orientation. The inner ear has chambers filled with a viscous uid and small particles (otoiths) containing calcium earbonate. The movement of these particles over small hair cells in the inner ear sends signals to the brain that are interpreted asmotion and acceleration. The figure below

shows the internal structure of themammaltan ca. Adaptations of the mammalian car to its functions The ear is adapted to its functions by possessing the following features

• The outer ear (pinna) is a fap of tissue which collects sound waves and directs theminto the

inner ear via the auditory canal

• The lining of auditory canal contains wax-secreting cells which produce wax. Thewax in the

canal traps dust particles and other foreign bodies and hence protects theinner delicate paris of an ear from mechanical damage or microbial infections

• The ear drum is thin and membranous, a fact that enables i to vibrate when soundvaves hit it

before converting the waves into vibrations and passing them on to theear ossicles in the middle

• ‘The ear ossicles (mallous, ineus and stapes) acts a lever systom which ean moveforward and

backward 1o amplify and transmit vibeations tothe oval window

• The Eustachian tube is hollow, a fact which allows airin and out of the mide ear tocqualize the

pressure between the inside and outside of the ear drum—whichimproves the drum’s ability to vibrate

• The cochlea is coiled to increase the surface area for sound reception It also cariesauditory

nerves which transmit sound impulses to the brain for imterpretationpinnacar drumskull bomesemicciular canalsauditory canaleustachiantubetound — windowcochlesmuditory nervelntemal structure ofthe human earoval window 7, ‘The presence of fluid-filled vestibular apparatus (semi-circular canals, sacculus, andutrculus) in the inner ear ficilitaes balancing of sound when the Quid is displaced The tongue The tongue is an organ responsible for taste. Its the primary organ of taste (gustation), asmuch

of ils upper surface is covered in taste buds, The tongue's upper surface is alsocovered with riumerous lingual papillae. The tongue is sensitive and kept moist by saliva,and 1s rchly supplied with nerves and blood vessels The receptors for taste, called taste buds, are situated chiefly in the tongue, but they arcalso located in the roof of the mouth near the pharynx. They are able to detect four basictastes: salty, sweet, bitter, and sour,

Generally, the taste buds close to the tip of the tongue are sensitive to sweet and saltytastes, whereas those in the back of the tongie are sensitive to bitter tastes, The taste budsin the sides of the tongue are sensitive to sour tastes, At the base of each taste bud there isa nerve that sends the sensations to the brain, The Sense of taste functions in coordinationwith the sense of smell The number of taste buds varies substantially from individual to individual, but greatermumbers

increase sensitivity Women, in general, have a greater number of taste budsthan men. As in the case of colour blindness, some people are insensitive to some tastes, eRe. bitter D \ Ba ‘*F \sour Soul coe j sweet and salt Location of taste buds in the human tongue Adaptation of the tongue to its functions (as a sense organ) The tongue is adapted to its functions by possessing the following features

• The tongue has taste buds which help it to respond the stimuli such as sweet, bitlersour and

salty 2 Atthe base of each taste bud there isa nerve that Sends the sensations tothe brain. The hursan nose The nose is the organ responsible for the Sense of small. The cavity of the nose is linedwith mucous membranes that have smell receptors connceted to the olfactory nerve. Thesmells themselves consist of vapours of various substances, The smell receptors interactwith the molecules of these vapours and transmit the sensations to the brain, The smellreceptors are

sensitive to seven types of sensations that can be characterized as camphar,musk, Tower, mint ether, acid, or putrid, The sense of smell s sometimes temporarilylost when a person has cold Dogs have a sense of'smell that is many times moresenstive than man's Frontal // Sinus i i Olfactory Bulb Nasal \s == “ Sinus 7, ~~ 7 S 4g

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The human nose When we want to —smelll food we draw air high up into the nasal cavity where thechemicals come into contact with hairs on the sensory cells, Different chemicalstimulate different sensory calls and nervous impulses are set up which pass along theverves tothe brain to be interpreted When our nose is blocked with cold, our food may become —tastolessl because we nolonger smell it Adaptations of the nose to its funetions

‘The nose is adapted to its functions by possessing the following features:

• There are olfactory nerves, which carry impulse from the nose to the olfactory lobes of the brain

for interpretation, The human nose

• Presence of mucus-seereting cells, which produce mucus that keep the surface of the nose moist
• Presence of hairs in the nose helps the nose to trap dust particles and other foreign bodies. When

the mucus is blown out from the nose, it carries the dust and otherforeign bodies with it, thus preventing the olfactory organs from damage The human skin The skin is the outer covering of the body. In humans, itis the largest organ of theintegumentary system, The skin has multiple layers of ectodermal tissue and guards theunderlying muscles, bones, ligaments and intemal organs. It protects us from microbesand the elements, helps

regulate body temperature; and permits the sensations of touch,heat, and cold The skin has three layers

• The epidermis, the outermost layer of skin, provides a waterproof barrier andercates our skin
• ‘The dermis, beneath the epidermis, contains tough connective tissue, hairfollicles, and sweat
• The deeper subcutaneous layer (Iypodermis) is made of fat and connectivetissue

The skin's colour 1s produced by special cells called melanocytes, which produce thepigment melanin, Melanocytes are located in the epidermis ‘tasty PO my OE re = a Ve a a9 Eiders 7 Ne im a Va t \ y ") Dorrie

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> ‘Layer 8 ‘of Fat i Sweat Fomdo «Gand inod Veweel Tnternal structure of the human skin impulses which are sent to the spinal cord or brain to be interpreted. air—fowest touch pain heat cold Dore receptor receptor receptor receptor 5D) fA apa ES Se an Pte aty A ANC 4) bepidermis Fe aS {dead ces) touch ——ft —as——s—a hair pace oe dermis pio ‘ving cols) gland —— Sensory receptors of the skin

Functions of skin

• Regulation: The skin plays an important role in regulation of body temperature inan organism

thus helping to keep the body temperature constant (endothermic).

• ‘The skin manufuetures vitamin D through exposure to sunlight, Exgosteol in thefuty layer of the

skin converts into Vitamin D under the influence of sunlight

• ‘The skin produces melanin that protects the body fiom ultra violet radiationswhich can cause

skin cancer. 4, The skin acts as sensory organ due tothe presence of various nerve endings.

• Protection: I prevents micro-orginism and other foreign materials from enteringthe body.
• Excretion: Sweat glands produce sweat, which gets rid of excess heat, water, salts some earbon

dioxide and urea

• Storage: Fat isa food store inthe dermis,

Adaptations of the skin to its fianctions (asa sense organ) The human skin is adapted to its sensory functions by having the following features:

• thas the hair erector muscle which controls whether the hair stands erect or liesdown depending

on the temperature of the surrounding.

• Its supplied with nerves which convey impulses to the CNS to be interpreted.
• Presence of blood vessels (in the dermis) which dilate when the body temperature ishigh to

facilitate heat loss by radiation and constrict when the temperature is low toreduce heat loss. The blood vessels also supply nutrients and oxygen to the skin andremove excretory products

• The skin has sweat glands which produce sweat to help cool the body. During a hotday, the

lands produce sweat (through sweat pores). Evaporation of the sweat usesthe body heat and hence helps to cool down the body. Drugs and Drug Abuse in Relation to Nervous Coordination The Meaning of Drugs and Drug Abuse, in Relation to Nervous Coordination Drugs A drug is any chemical substance, natural or synthetic, that has known physiologicaleffects on humans or other animals. Foods are generally excluded from this definition, inspite of their

physiological effects on animal species Most drugs, both useful and harmful, may affect the body (especially the brain), byaltering the nerve celly natural reaction to these chemicals, or hy mimicking the body'snormal compounds Some drugs slow down the passage of stimuli by affecting nerve cell membranes, andothers act like neurotransmitters, pethaps passing stronger or longer-lasting impulses Assuch they may alter the way sensory information is processed, or affect the thinkingprocess

Stimulants are drugs which speed up the action of the brain e.g. caffeine, found in tea andeofee Sedatives are drugs which slow down the action of the brain ¢g. alcohol. Evenone alcoholic drink will have some effect on the brain.

Proper Ways of Handling and Using Drugs Proper use and handling of drugs When using and handling drugs the following precautions must be observed:

• Avoid taking any drug without diagnosing the disease and prescription by the doctor
• Always stay away from peer pressures and drug addicts to avoid eapying their badhabits
• Keep yourself busy with a nomber of activities such as sports and games, readingbooks, ete

Remember _an idle mind is the devil's workshop"!

• Report any case of drug abuse or trafficking to concemed authorities.
• Forma counselling club to advise people especially youths on how to keep off fromdrugs.
• one feels addicted, sthe should seck advice from health officials
• Never take a dose more or less that what has been preseribed by the doctor
• Complete the prescribed dose even afler you start feeling well or after the sympiomsof the

disease has disappeared 9. Keep all drugs out of reach of ehildren and drug addicts, Drug addiction Drug addiction refers to the compulsive and repeated use of increasing amounts of érugswith the appearance of withdrawal symptoms when drux use ceases. While drug use oftenbegins as a way to seek recreation, the addictive properties of the drug make an addicterave for it permanently This compulsion is uncontrollable and may interfere with aperson’s everyday life. Even when the

effects of drugs are damaging to a person's bodyand relationships with friends, family members

and co-workers, the constant need for adrug often overcomes any rational thinking The human body has its own ability to produce some chemicals for its properfinetioning. The continued use of the drug suppresses the body's ability to produce thesechemicals or diminishes its production because these chemical are replaced by the drug The body thus uses the drug as substitute for its own natural chemieals. Since thesechemicals are no longer produced, the body

perceives that it needs the drug for itsfunetioning. Therefore, a person craves for the drug so much that s/he feels eannot livewithout taking it. At this level the drug abuser becomes addicted to the drug. This iscalled drug addiction

Causes and Effects of Drug Addiction

Like many mental health disorders, several causes may contribute to development of drugadkiction and dependence. Some of the causes of drug abuse and addiction include thefollowing:

• Some people take drugs to avoid physical or emotional pain, discomfort, stress boredom, anxiety

and depression

• Some people also take drugs as a way to forget problems and life hardships theyexperience in

life,

• Recreation: Drug users believe that taking drugs make them _feel better" and lively
• Peer pressure leads people to drug so as to create a sense of belonging and fitting inthe peer

group. It's offen said that teens use drugs when their friends do. Using drugsallows these young people to fit in with their peers and blend in with the crowd

• . Desite for new experience and arousal: Some people just take drugs as an_experiment’ to find

out the experience the drug users feel, but badly end upbecoming drug addicts.

• Lack of life and social skills, for example drug resistance skills that would help person leam

how to say no or avoid bad influence. People who are easy to copyhabits from others inrespective of the outcome of the given habit, ean easily get intodrug use.

Effects of drug abuye and addiction

Effects of drug abuse and addiction

Many illegal chemicals have extreme effects on the function of the brain, e.g. some drugscause hallucinations – objects around you may change colour. shape and size, or you maysee and experience things that are not there at all. Such experiences may cause fear,depression, and mental disorders. Mostly, these substances alter one's perception ofreality Drugs produce a variety of short-term effects, but the most common ones includeinereased heart

rate, high blood pressure, dizziness, tremors, mood changes and paranoia In high dosages, the risk for more dangerous effects increases, and the potential for heartattack, stroke, respiratory failure and coma increases, The various effects of drug abuseinclude the following:

• Drugs confuse the mental faculties so that many drug users die in accidents, oroverdose on the

chemicals. Drugs can also induce them do dangerous activities suchas unsafe sex or reckless driving.

• Many drags induce a feeling of dependency (addiction) and are linked with criminalactivity
• Solvent abuse (sniffing glue, lighter fuel, ete.) – on which one can easily overdose -can cause

death by heart failure

• Other substances can incidentally affect the body's "thermostat" – located in thehypothalarnus

(refer to a topic on homeostasis and osmoreaulstion) and cause death following disruption of the body's temperature control and regulation of the body'swater content. Even "legal" chemicals such 2s alcohol (a "social" drug!), haveadverse effects on the body

• They can lead to aggressiveness, erime, violence and divorce
• Sharing of needles used to inject drugs into the bloodstream cause HIV infections andhepatitis

among the addiets. Likewise, because drugs impair one’s judgement, it canlead to unprotected sex and henee become the cause of contracting other sexuallytransmitted diseases like syphilis, gonorrhoea, chlamydia and herpes

• Drugs are very expensive to purchase. Therefore, the addicts spend much of theirmoney on drugs

at the expense of other family needs.

• Many dnug addicts are weak and so they cannot participate in in-come generatingactivities. This

leads to poverty, a fact which can lead to failure to meet one’s basieneeds.

• Drug addiction among women can lead to birth defects which include giving birth tosmall or

premature abies or cause the bahy 10 have withdrawal symptoms, birthdefeets or learning, and behavioural problems, Additionally, illicit drugs may containimpurites that may be harmful to unborn baby

• Medical concerns like depression and anxiety can severely interrupt the addiet'ssocial and

professional life, leading to mood swings, chronic fatigue and a diminishedinterest in former hobbies and important life events Preventive and Control Measures of Drug Abuse Drug abuse is a serious psycho-sociological problem often difficult to be cured, The bestway to avoid these tragedies is to never start taking drugs. However, nowadays specifictreatments are available for different types of mental illness. A regular, prolonged andsincere treatment is

required Social therapy or rehabilitation has got a very significantrole. The following activities ccan be done for the control of drug addiction: 1 Early detection, treatment and rehabilitation of drug addicts can help minimize theproblem,

• Parents should set a warm and friendly atmosphere at home so thatthe drug users canfeel easy fo

cooperate with,

• Motivation of the addicts to make up for detoxification
• ‘The youth should be motivated to get involved in the fight against drug abuse
• Educating the community about the problems of drug addiction
• Enforcement of laws, rules and regulation for the control and supply of drugs
• The school curricula should coniain courses about the drug addiction sand drug abusein detail

(like the topic you are reading now)

• Various effects of drug addiction must be advertised through newspapers, radio television,

magazine, social media, and many other media so as to make the problemknown to as many people as possible.

• ‘The experience of drug users can be advertised to the people through media to makethe general

public aware of the effects of drugs so as to discourage those who mightthink of starting taking drugs. Location of the Different Endocrine Glands in the Mammalian Body

THE ENDOCRINE SYSTEM

The endocrine system is a collection of glands that produce hormones which regulatemetabotism, growth and development, tissue function, sexual function, reproduction sleep, and mood, among other functions. ‘The glands are located in various parts of thehuman body. The fumetion of these glands is to release various hormones, and as 2 whole,they are most commonly referred to as the endocrine system. These glands are pituitarygland,

hypothalamus, thymus, pineal gland, testes, ovaries, thyroid, adrenal glands parathyroid and panereas, The location of these glands in the human body is as shown inthe diagrams below Hypothalamus S Crm cad Pituitary gland 7 Parathyroid gland ~~ Thyroid gland is Thymus gland 2 Se re Adrenal gland a4 —Pancreas eS C? “é Ovary SU miae (female) y a Testis (male) The human endocrine system The role of Hormones produced by each Endocrine gland

The hormones released by glands of the endocrine system regulate the funetions of manycells and organs as indicated in the following table Disorders of Hormonal Coordination in Mammals

Causes of endocrine disorders

The causes of endocrine disorders are typically grouped into two categories

• Endocrine disease that results when a gland produces too much or too little of anendocrine

hormone, called 2 hormone imbalance

• Endocrine disease due to the development of lesions (such as nodules of tumours) inthe

endocrine system, which may or may not affect hormone levels, The endoerine’s feedback system helps control the balance of hormones in thebloodstream. If your body has foo much or too little ofa certain honmone, the feedbacksystem signals the proper land or glands to correct the problem. A hormone imbalancemay occur if this Feedback system has trouble keeping the right level of hormones in thebloodstream, or if your body doesn't clear

them out of the bloodstream properly Increased or decreased levels of endocrine hormone may be caused by

• A problem with the endocrine feedback system.
• Disease
• Failure of a gland to stimulate another ghand jo release honmones (for example, aproblem with

the hypothalamus can disrupt hormone production in the pituitarystand)

• A genetic disorder, such as multiple endocrine meoplasia or congenitalhypothyroidism
• infection
• Injury to an endocrine gland
• Tumour of an endocrine gland Most endocrine tumors and nodules (humps) are non-cancerous

They usually do notspread to other parts of the body. However, a tumor or nodule on the gland ‘may interferewith the glands hormone production

Types of endocrine disorders

There are many different types of endocrine disorders, Majority of endocrine disorderscause the endocrine glands to produce too much (hypersecretion) or too low(hyposecretion) of a given hormone from a particular gland Common problems thatresult from oversecretion (hypersecretion) or undersecretion (hyposecretion) of givenhormones fiom given endocrine lands are explained below

PITUITARY GLAND

Hypersecretion of growth hormone Gigantism in chiklren and acromegaly in adults If the pituitary gland produces too much growth hormone, 2 child's bones and body partsmay grow abnormally fast Hyposceretion of growth hormone: Pituitary dwarfism – if the condition occurs duringehildhood, it slows dawn long bone growth Hypersecretion of ADH: Causes mereased reabsorption of water in the kidney tubulesleading to production ofa litle urine but which is more concentrated

Hyposecretion of ADH: Less water is absorbed from the glomeruli filtrate back to thebody. leading to production of large volumes of dilute urine, This is called diuresis and isa symptom of diabetes inspidus

THYROID GLAND

Hyperthyroidism 1, Grave's disease: The most common cause for an overactive thyroid is an autoimmunedisorder called Grave's disease. Grave's disease, considered an autoimmune disease,shows clevated weight loss, nervousness, excessive perspiration, nervousness, highmetabolic rate and rapid, inregular heartbeat

• Exophthalmos: protrusion of the eyeballs caused by oedematous tissue behind theeyes

Hypothyroidism 1, Cretinism (infantile hypothyroidism) – shows stunted growth, thickened facialfeatures, abnormal bone development and mental retardation

• Myxedema – low metabolic rate, lethargy (a condition characterized by exttemefatigue or

drowsiness, or prolonged sleep patterns), weight gain, increase in bodyfluids.

• Goitte -abnormal growth of the thyroid gland.

PARATHYROID GLAND.

Hyperparathyroidism: demineralization of bone resulting in possible bone deformityand fracture, ang stones in the urinary tract Hypoparathyroidism: decreased plasma calcium levels which cam lead to severe muscletetany (a condition characterized by or resulting from uncontrolled musele spasms).

PANCREAS

Hyperinsulinism: The liver is cverstimulated to convert excess glucose to glycogen andfats for storage This leads to low glucose concentration in the blood, a condition calledhypoglycemia This condition results in lack of glucose delivery to the brain causingdisorientation, lunconsciousness and even death (usually the result ofan overdose ofinsulin) Hypoinsulinism: Under-seeretion of isulin causes very litle glucose to be converted toglycogen

and fats, This results in elevated glucose levels in the blood and urine, Thecondition is called hyperglycaemia, and is a symptom of diabetes mellitus. Over time,diabetics experience vascular and neural problems. Secondarily, poor circulation maylead to gangrene, blindness, kidney damage and impotence,

ADRENAL GLAND

Hypersecretion of corticosteroids: Cushing's syndrome – changes in carbohydrate andprotein metabolism resulting in a puffy appearance. Hyposeeretion of glucocorticoids and mineralocorticoids: Addison's disease -symptoms of the disease include fatigue, stomach upset, hypoglycaemia, sodium andpotassium imbalance dehydration, hypotension, and rapid weight loss. Death occurs withlack of treatment, Hypersectetion of adrenaline: hypertension, obesity, headache, inereased heartbeat,weak bones,

hyperglycaemia, nervousness, sweating and early onset of sexualdevelopment. Hyposeeretion of adrenaline: low blood pressure, fatigue, muscular weakness, muselewasting, inability to withstand stress, and increased dark pigmentation of the skin.

OVARIES

Hypersecretion of oestrogen: Causes decreased sexual desire, heavy menstrual low anclinereased weight in females; Hyposecretion of oestrogen: Causes failure of females to develop some secondarysexual

characteristics, poor development of the reproductive organs, liver, kidney andlungs.

TESTES

Hypetsecretion of testosterone: Causes males to have female features such as enlargedbreasis and a wide pelvis, Hyposecretion of testosterone Causes frilure of males to develop some secondarysexual

characteristics, poor development of the reproductive organs and weak bones andmuscles.

THYMUS

Not responsible for any effects of hypo ar hyper secretion of thymosin

PINEAL

Not responsible for any effects of hypo or hyper secretion of melatonin. Coordination in Plant, Concept of Tropie and Nastic Responses

The Concept of Tropic and Nastie Responses

COORDINATION IN PLANTS

Roth, plants and animals react (or respond) to various stimuli around them. But themethod of reacting to stimuli is not similar in plants and animals, They react to stimuli indifferent ways. For

example, plants bend towards light but animals do not bend wowardslight The animal amoehe

reacts to the presence of food by moving towards the foodpartcte The plants do not have a nervous system and sense organs like eyes, ears, or nose, ete. like the animals, but they can stil sense things. ‘The plants can sense the presence ofstimuli ike light, aravity, chemicals, water, and touch, ete., and respond to them. Theysense these stimuli by using hormones in them.

The stimuli Tike light, gravity, chemicals, water, and touch, etc, are called environmentalchanges. So, we can also say that the plants coordinate their behaviour againstenvironmental changes by using hormones. The hormores in plants do not act the sameway as in animals, The hormones in plants coordinate their behaviour by affecting the growth of a plant And the effect on growth of the plant can result in the movement of a part of the planthike shoot (stem) or

root, ete towards a certain stimulus. Experiments to Investigate the Effects of Tropic and Nastie Responses in Plants Plants receive and respond to a variety of stimuli that are important to their survival in theenvironment. These responses allow the plants to survive, grow, develop and reproduce The movement of plants in the direction of stimulus is known as ‘tropism’. Tropisms aregrowth responses of plants that result in curvatures of plant organs toward or away fromecttain stimult

Tropisms can be positive, in which case the plant will bend toward astimulus, or negative, in which case the plant will bend away from a stimulus The other movements shown by the plants are associated with the growth of the plants.For

example, the shoot system moves towards sunlight and the root system towards earth Thus, the

plants also respond to their environment Important tropisms in plants include phototropism, geotropism, hydrotropism,chemotropism and thigmotropim. Phototropism Phototropism is the tendency for plant organs to bend in response to a directional lightsource For example, light streaming in a window from one direction will often cause thestems of plants placed nearby to bend toward the window, a positive phototropism Most plant shoots are positively phototropie because they tend to grow towards light Most roots

are negatively phototropic because they away from light ght A ——————=— y & \ Plantbends A plant shoot bending towards light The Importance of Tropic and Nastie Responses

Importance of phototropism

Phototropism is important to plants because of it enables the plant leaves to be placedunder direct sunlight to absorb maximutn light so as to carry out photosynthesisetfectively Gcotropism Geotropism is the movement of a part of the plant towards gravity, In most plants, roots grow downward with gravity while shoots grow upward against gravity. Within hours, the shoot of a plant placed on its side will usually bend upward and the roots will bend downward as the plant

reorients its direction of growth in response to gravity Most plant roots grow towards sravity and are said to be positively geotropic. Most shoots grow away from gravity and are said be negatively geotropic: ueotropic wet

PTO Positively

DPE” geotropic

Importance of geotropism

Geotropisms are important to plants because of the following reesons

• {enables the plams to send roots into the ground hence anchoring the plant firmly into the soil
• It enables plant roots to absorb water and mineral salts from the sol.
• Negative geowopism exhibited by the shoot enables the shoot to grow upwards, and in so doing

exposes the plant leaves to maximum sunlight for effective photosynthesis Hydrotropism Hydrotropism is the movement of a plant or part of a plant towards water, Plant rootsnormally grow towards moisture, They are therefore positively hydrotropie. If you plant aplant near a water source such as porous pot or river, the roots will always grow towardswater Water ie 1

Porous Ce }l_ Pea

Pot : po og Seeding Curvature Plant roots growing towards water

Importance of hydrotropisin

It enables the plants to absorb dissolved minerals and water. Water is necessary forvarious

• Photosynthesis
• Numerous physiologieal reaction that take place within pkant cells
• Turgor pressure, which aids in plant support.
• Dissolution of mineral salts

Chemotropism pollen grain pollen tube ovule Carpel Chemotropic response An example of positive and negative chemo-tropism is shown by a plants roots; the rootsgrow tovvards useful minerals displaying positive chemo-tropism, and grow away frombermful acids displaying negative chemo-tropism Chemotropism is the movement or growth of an organism or part of an organism inresponse to a chemical stimulus, During the process of fertilization the movement ofpolien tube towards ovule

Adve to secretion ofa sugary chemical in the ovary is anexample of ehemotropism

Importance of chemotropism

• It enables the plant to absorb mineral salts from the soil when the roots grow towardsbencticial

chemicals such as fertilizers. a survive by avoiding contact with such harm chemical

• Ices the erttiaation process i lowering plats,

Thigmotopism or haptotopism Thigmotropsim refers to non-diretional movements whith tke lave neither towatds nowy i i i TH DE eave Ea iomg BS 6 Mina pica plant when its dave fe tue with Sages or aby bjet.The lenves fold even he Saye a by Hind, Al te spain wnileecnii vette OF many wining plans, such as pea, will bend toward the side receiving a touchstimulus. Continual stimulation can lead 1a the oiling of the tnd sround- an object which een vning plans to gop ajests on

ii i en Sa hs ‘i Lit Mimosa pudica plant responding to touch stimnilus Thigmotropism in climbing plants