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CHAPTER 48 NERVOUS SYSTEMS

CHAPTER 48 NERVOUS SYSTEMS. Section B: Vertebrate Nervous Systems. Dr. Hesham Sharaf. Nerve impulses propagate تـُقـَوٍى themselves along an axon. The action potential is repeatedly regenerated along the length of the axon.

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CHAPTER 48 NERVOUS SYSTEMS

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  1. CHAPTER 48 NERVOUS SYSTEMS Section B: Vertebrate Nervous Systems Dr. Hesham Sharaf

  2. Nerve impulses propagate تـُقـَوٍى themselves along an axon • The action potential is repeatedly regenerated along the length of the axon. • An action potential achieved at one region of the membrane is sufficient to depolarize a neighboring region above threshold. Thus triggering a new action potential.The refractory period assures that impulse conduction is unidirectional. Un 7, Ch 48 • Saltatory conduction التوصيل القفاز. • In myelinated neurons only, the unmyelinated regions of the axon depolarize.Thus, the impulse moves faster than in unmyelinated neurons. Dr. Hesham Sharaf Fig. 48.10 & 48.11, Page 1032

  3. Cellular communication There are two types of communication between cells: • Electrical Synapses. • Action potentials travels directly from the presynaptic to the postsynaptic cells viagap junctionsأماكن الإتصال (less common). • Chemical Synapses. • More common than electrical synapses. • Postsynaptic chemically-gated channels exist for ions such as Na+,K+, and Cl-viasynaptic cleft. • Depending on which gates open the postsynaptic neuron can depolarize or hyperpolarize. Read legend of figure 48.12, Page 1033 Un 7 Ch 44 Dr. Hesham Sharaf Fig. 48.12, Page 1033

  4. The same neurotransmitter can produce different effects on different types of cells • Acetylcholine. • Excitatory محفز to skeletal muscle. • Inhibitory مثبط to cardiac muscle. • Secreted by the CNS, PNS, and at vertebrate neuromuscular junctions. • Biogenic Amines. • Epinephrine and norepinephrine. • Can have excitatory or inhibitory effects. • Secreted by the CNS and PNS. • Secreted by the adrenal glands. Nerve impulse Synaptic terminal communication Dr. Hesham Sharaf

  5. Vertebrate nervous systems have central and peripheral components • Central nervous system (CNS). • Brain and spinal cord. • Both contain fluid-filled spaces which contain cerebrospinal fluid (CSF). • The central canal of the spinal cord is continuous with the ventricles of the brain. • White matter is composed of bundles of myelinated axons. • Gray matter consists of unmyelinated axons. • Peripheral nervous system (PNS). • Everything outside the CNS. • Cranial nervesأعصاب الجمجمة (12 pairs): that originate in the brain and innervate the head and upper body. • Spinal nervesأعصاب شوكية (31 pairs): that originate in the spinal cord and innervate the entire body. • Ganglia associated with the cranial and spinal nerves. Dr. Hesham Sharaf

  6. الأعصاب الحسية (الواردة) الأعصاب المحركة (الصادرة) إرادية الذاتى (لا إرادى) السمبثاوى جار السمبثاوى Read, Page 1040 The division of PNS interact in maintaining homeostasis Dr. Hesham Sharaf Uses acetylecholine Uses norepinephrine Fig. 48.17, Page 1041

  7. جار السمبثاوى السمبثاوى • A closer look at the (often antagonistic) divisions of the autonomic nervous system (ANS). Dr. Hesham Sharaf Fig. 48.18, Page 1041

  8. Structure of Brain 1 المخ الأمامى الغدة النخامية 2 المخ الأوسط 3 النخاع المستطيل المخ الخلفى الحبل الشوكى المخيخ Dr. Hesham Sharaf Fig. 48.20, Page 1043

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