DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Central Nervous System CRT04101 · Anatomy, Physiology and Pathology START READING NOTES Study Central Nervous System using the sections below. Use the topic navigation to continue through Anatomy, Physiology and Pathology. Contents of This Topic Nervous System Somatic Nervous System Nerve tissue is made up of nerve cells called neurons or nerve fibres Synapse. Synape and synaptic transmission With respect to the skeletal muscles, this inhibition prevents excessive contraction and is important for coordination. Types of neurons Motor neurons Central nervous system (CNS) is a part of nervous system which is made up of brain and spinal cord Central Nervous System The Brain Pons Hypothalamus Thalamus Basal ganglia Meninges AUTONOMIC NERVOUS SYSTEM Sympathetic division Keypoints Common disorders of Nervous system Parkinson’s disease Alzheimer’s disease Neuroleptic disorders are mixtures of symptoms, especially anxiety and depressive ones. Multiple sclerosis Schizophrenia Hydrocephalus Neural tube defects CENTRAL NERVOUS SYSTEM Nervous System Refers to the part of the body that coordinates its voluntary and involuntary actions and transmits signals between different parts It is the system that conducts stimuli from sensory receptors to the brain and spinal cord and that conducts impulses back to other parts of the body. Autonomic Nervous System The part of the nervous system that regulates the involuntary activity of the heart, intestines, and glands, including digestion, respiration, perspiration, metabolism, and blood-pressure modulation. Somatic Nervous System The part of the peripheral nervous system that transmits signals from the central nervous system to skeletal muscle and from receptors of external stimuli, thereby mediating sight, hearing and touch. Nerves are bundles of axons in the peripheral nervous system (PNS) that act as information highways to carry signals between the brain and spinal cord and the rest of the body. The Central Nervous System Brain Spinal cord Peripheral Nervous system is divided into: Autonomic nervous system Peripheral nervous system Nerve tissue is made up of nerve cells called neurons or nerve fibres All neurons have the same physical parts. The cell body contains the nucleus and is essential for the continued life of the neuron. Dendrites are processes (extensions) that transmit impulses toward the cell body. The one axon of a neuron transmits impulses away from the cell body. It is the cell membrane of the dendrites, cell body, and axon that carries the electrical nerve impulse. Axons and dendrites are collectively called Schwann cells in the peripheral nervous system and are covered by a membrane called myelin sheath. Node of Ranvier is the spaces between adjacent Schwann cells or segments of myelin sheath. Neurolema are the nuclei and cytoplasm of Schwann cells. Synapse. It is the small gap or space between the axon of one neuron and the dendrites/cell body of the next neuron. The synaptic knob of presynaptic axon contains chemical neurotransmitters that are released to the synapse on the arrival of an impulse. Synapses ensure one way impulse transmission The neurotransmitter diffuses across the synapse, combines with specific receptor sites on the cell membrane of the postsynaptic neuron, and there generates an electrical impulse that is, in turn, carried by this neuron’s axon to the next synapse. Example of neurotransmitter is acetylcholine found at the neuromuscular junction. Synape and synaptic transmission The neurotransmitter diffuses across the synapse, combines with specific receptor sites on the cell membrane of the postsynaptic neuron, and there generates an electrical impulse that is, in turn, carried by this neuron’s axon to the next synapse, and so forth. A chemical inactivator at the cell body or dendrite of the postsynaptic neuron quickly inactivates the neurotransmitter. This prevents unwanted, continuous impulses, unless a new impulse from the first neuron releases more neurotransmitter. Many synapses are termed excitatory, because the neurotransmitter causes the postsynaptic neuron to depolarize (become more negative outside as Na+ ions enter the cell) and transmit an electrical impulse to another neuron, muscle cell, or gland. Some synapses, however, are inhibitory, meaning that the neurotransmitter causes the postsynaptic neuron to hyperpolarize (become even more positive outside as K+ions leave the cell or Cl- ions enter the cell) and therefore not transmit an electrical impulse. Such inhibitory synapses are important, for example, for slowing the heart rate, and for balancing the excitatory impulses transmitted to skeletal muscles. With respect to the skeletal muscles, this inhibition prevents excessive contraction and is important for coordination. An example of a neurotransmitter is acetylcholine, which is found at neuromuscular junctions, in the CNS, and in much of the peripheral nervous system. Acetylcholine usually makes a postsynaptic membrane more permeable to Na+ ions, which brings about depolarization of the postsynaptic neuron. Cholinesterase is the inactivator of acetylcholine. There are many other neurotransmitters, especially in the central nervous system. These include dopamine, GABA, norepinephrine, glutamate, and serotonin. Each of these neurotransmitters has its own chemical inactivator. Some neurotransmitters are reabsorbed into the neurons that secreted them; this process is called reuptake and also terminates the effect of the transmitter. Types of neurons Neurons are classified in to three groups which are : 1.Sensory (afferent) neuron, 2.Motor (efferent) neuron 3.Interneuron. Sensory neurons Carry impulses from receptors to the central nervous system. Receptors detect external or internal changes and send the information to the CNS in the form of impulses by way of the afferent neurons. The central nervous system interprets these impulses as a sensation. Motor neurons Carry impulses from the central nervous system to effectors. The two types of effectors are muscles and glands. In response to impulses, muscles contract or relax and glands secrete. Interneurons They are found entirely within the central nervous system. They are arranged so as to carry only sensory or motor impulses, or to integrate these functions. Some interneurons in the brain are concerned with thinking, learning, and memory. Central nervous system (CNS) is a part of nervous system which is made up of brain and spinal cord The Spinal cord The spinal cord transmits impulses to and from the brain and is the integrating centre for the