The functional Anatomy of the Nervous System. DR. OKSANA PETRICHKO Department of Human Anatomy

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1 The functional Anatomy of the Nervous System DR. OKSANA PETRICHKO Department of Human Anatomy

2 Coordination and Regulation of Body Systems Nervous system. Conducts nerve impulses maintaining homeostasis (electrochemical). Endocrine system. Serves as messaging system maintaining homeostasis (chemical).

3 Nervous & Endocrine Systems

4 Main Functions of the Nervous System Connect the organism to the environments Coordinate with all processes of the body Adapt organism to the environments Specific features of the human nervous system distinguish man from the animals (social life and speech)

5 Divisions of the NS CNS Central Nervous System Brain & spinal cord PNS Peripheral Nervous System Cranial nerves (12 pairs) Spinal nerves (31 pairs) Nervous plexus Nerves

6 Divisions of the NS Somatic Nervous System Visceral (Autonomic) Nervous System Sympathetic Parasympathetic

7 Somatic Nervous System Somatic Sensitive General somatic sense (touch, pain, pressure, vibration) Proprioceptive sense (skin, body wall, limbsmuscles & joints) Special somatic senses (hearing, equilibrium, vision, smell) Somatic Motor Skeletal muscle

8 Visceral (Autonomic) Nervous System Visceral sense General visceral: stretch, pain, temperature, chemical changes, irritation in viscera, nausea, hunger Special visceral: taste Visceral motor (ANS) Smooth muscle Cardiac muscle Glands

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12 Nervous tissue Neurons unipolar neuron pseudounipolar neuron bipolar neuron multipolar neuron Supporting cells (neuroglia)

13 Neuron - - The functional and structural unit of the nervous system Specialized to conduct information from one part of the body to another Cell body (soma) One or more specialized, slender processes (axons/dendrites) An input region (dendrites/soma) A conducting component (axon) A secretory (output) region (axon terminal)

14 Dendrites Usually numerous Branched Sends signals to soma The ends of the dendrites form receptors

15 Axons 1 per soma Initial segment from axon hillock Transmits AP away from soma No Nissl bodies (no protein synthesis) Neurofilaments Axonal transport Axon collaterals Terminal branches Axon terminals

16 Neuron

17 1. unipolar neuron bipolar neuron 3. pseudounipolar neuron neuron a. axon multipolar d. dendrite

18 Neuron classification by shape

19 CNS Neuroglia Outnumber neurons by about 10 to 1 (the guy on the right had an inordinate amount of them). 6 types of supporting cells 1. 4 are found in the CNS: Astrocytes Star-shaped, abundant, and versatile Guide the migration of developing neurons Act as K+ and NT buffers Involved in the formation of the blood brain barrier Function in nutrient transfer

20 CNS Neuroglia 2. Microglia 3. Specialized immune cells that act as the macrophages of the CNS Ependymal Cells Low columnar epithelial-esque cells that line the ventricles of the brain and the central canal of the spinal cord Some are ciliated which facilitates the movement of cerebrospinal fluid

21 CNS Neuroglia 4. Oligodendrocytes Produce the myelin sheath which provides the electrical insulation for certain neurons in the CNS

22 PNS Neuroglia 2 types of glia in the PNS 1. Satellite cells Surround clusters of neuronal cell bodies in the PNS Unknown function 2. Schwann cells Form myelin sheaths around the larger nerve fibers in the PNS. Vital to neuronal regeneration

23 Myelin sheaths Wrapping of PM around axon Phospholipid bilayers form insulation Gaps between Schwann cells are nodes of Ranvier Allow faster propagation of AP Saltatory conduction

24 Nerve Bundle of axons in the PNS Endoneurium around each axon Loose CT Perineurium CT around a bundle of axons Epineurium CT around a nerve

25 Interneurons / association neurons Located in CNS >99% of all neurons ~ all multipolar Integration of information

26 SYNAPSE SYNAPSE Ÿ Presynaptic Portion: Synaptic Button - synaptic vesicle - mitochondria - presynaptic membrane: tubulin Ÿ Synaptic Cleft nm Ÿ Postsynaptic Portion - postsynaptic membrane: actin, fodrin, spectrin - mitochondria

27 SYNAPSE SYNAPSE

28 SYNAPSE

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30 Synapses Presynaptic neuron Postsynaptic neuron

31 Synapses Axodendritic synapses Axosomatic synapses Axoaxonic synapses

32 Synapse structure Presynaptic element Axon terminal Synaptic vesicles Neurotransmitters Mitochondria Synaptic cleft Postsynaptic elements NT receptors May generate AP

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34 Reflex arcs Reflex = rapid motor response to a stimulus Unlearned Unpremeditated Involuntary Can involve all muscle types and/or glands

35 Knee-jerk stretch reflex Monosynaptic reflex arc Tap patellar tendon Stretch quadriceps femoris Stimulate stretch receptor AP to motor neuron Contract quadriceps femoris Knee extends 12.18a

36 Withdrawal reflex Polysynaptic

37 2 Main Paths Convergence and Divergence

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40 Saltatory Conduction Appear the jump from node to node. Speed of impulses is much faster on myelinated nerves then unmyelinated ones. Speed also increases with increase in diameter. Ex.) 120m/s skeletal muscle.5m/s skin

41 Neuron Communication

42 Developmental Aspects

43 Development

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46 Structure of the Spinal Cord

47 Meninges of the Spinal Cord

48 A Reflex Arc

49 Spinal Cord Reflex

50 Simple Nerve Path

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53 The Spinal Cord The spinal cord extends from the foramen magnum to the level of the 1st or 2nd lumbar vertebrae It is enclosed within the vertebral column

54 The Spinal Cord The spinal cord is a provides a two way conduction pathway to and from the brain It is a major reflex center

55 The Spinal Cord The spinal cord is protected by bone, cerebrospinal fluid, and meninges Dura mater, arachnoid, pia mater

56 The Spinal Cord Between the bony vertebrae and the dural sheath is a large epidural space filled with a soft padding of fat and a network of veins Cerebrospinal fluid fills the subarachnoid space

57 The Spinal Cord Inferiorly, the dural and subarachnoid membranes extend to the level of S2 while the spinal cord ends at L1 Subarachnoid space beyond L1 is an ideal site for a spinal tap

58 The Spinal Cord The spinal cord terminates in a tapering cone shaped structure called the conus medullaris

59 The Spinal Cord A fiberous extension of the pia mater, the filum terminale extends inferiorly from the conus medullaris to attach to the posterior surface of the coccyx

60 The Spinal Cord There are 31 pairs of spinal nerves that arise from the cord by paired roots and exit from the vertebral column via the intervertebral formina Each segment of the spinal cord is defined by a pair of spinal nerves that lie just superior to their corresponding vertebra

61 The Spinal Cord The spinal cord has obvious enlargements where the nerves serving the upper and lower limb arise Cervical enlargement Lumbar enlargement

62 Cross Section of Spinal Cord The spinal cord has two grooves that mark its surface Anterior median fissure / Posterior medial sulcus

63 Gray Matter and Spinal Roots These grooves run the length of the cord and partially divide it into right and left halves Gray matter inside, the white matter outside

64 Gray Matter and Spinal Roots The gray matter consists of a mixture of neuron cell bodies, their unmyelinated processes, and neuroglia (support cells)

65 Gray Matter and Spinal Roots The white matter is composed of myelinated and unmyelinated nerve fibers that represent ascending, descending and transverse pathways

66 Gray Matter and Spinal Roots The gray matter consists of mirror-image lateral gray masses connected by a cross-bar of gray matter called the gray commissure that encloses the central canal

67 Gray Matter and Spinal Roots The two posterior projections of gray matter are the posterior (dorsal) horns; the anterior pair are the anterior (ventral) horns with lateral horns in the lumbar and thoracic portions of the cord

68 Gray Matter and Spinal Roots The anterior horns house nerve cell bodies of the somatic motor neurons These send their axons out via ventral roots of the spinal cord to the skeletal muscles

69 Sectional Anatomy of the Spinal Cord

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71 Gray Matter and Spinal Roots The amount of ventral gray matter present at a given level of the spinal cord reflects the amount of skeletal muscle innervated at that particular level Thus, the anterior horns are the largest in the areas where the innervation for limbs is present Cervical enlargement / arms Lumbar enlargement / legs

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77 Meninges and Ventricles of the Brain

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86 Nerve Plexuses Plexus = braid Nerves supplying the limbs form plexuses when they leave the spinal cord Cervical Brachial Lumbosacral Lumbar Sacral

87 Nerve Plexuses

88 Cervical Plexus Formed by spinal nerves C1 C5 Nerves innervate the neck and shoulder region Phrenic nerve to the diaphragm

89 Cervical Plexus

90 Brachial Plexus Formed T1 by spinal nerves C5 C8 and Nerves innervate the arm and shoulder Radial nerve Ulnar nerve Median nerve (between radial & ulnar nerve)

91 Brachial Plexus Human Anatomy, 3rd edition Prentice Hall, 2001

92 Brachial Plexus Human Anatomy, 3rd edition Prentice Hall, 2001

93 Lumbar Plexus Formed L4. by spinal nerves T12 and L1 Innervates the medial and anterior portions of the thigh and lower abdominal regions Lateral femoral cutaneous nerve

94 Lumbar Plexus Human Anatomy, 3rd edition Prentice Hall, 2001

95 Lumbosacral Plexus Human Anatomy, 3rd edition Prentice Hall, 2001

96 Sacral Plexus Formed by spinal nerves L4 and L5, and S1 and S2 Innervates the posterior portion of the hip, thigh, and leg, and the genital region Sciatic nerve

97 Sacral Plexus

98 Sacral Plexus

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