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1 Structure and Function of the Neurologic System Chapter 14.

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Presentation on theme: "1 Structure and Function of the Neurologic System Chapter 14."— Presentation transcript:

1 1 Structure and Function of the Neurologic System Chapter 14

2 Mosby items and derived items © 2006 by Mosby, Inc. 2 Overview of the Nervous System Central nervous system (CNS) Brain and spinal cord Peripheral nervous system (PNS) Cranial nerves Spinal nerves Pathways Afferent (ascending) Efferent (descending)

3 Mosby items and derived items © 2006 by Mosby, Inc. 3 Overview of the Nervous System Peripheral nervous system (PNS) Somatic nervous system Motor and sensory pathways regulating voluntary motor control of skeletal muscle Autonomic nervous system Motor and sensory pathways regulating the bodys internal environment through involuntary control of organ systems Sympathetic Parasympathetic

4 Mosby items and derived items © 2006 by Mosby, Inc. 4 Cells of the Nervous System Neuron Variable size and structure throughout the nervous system Cellular constituents Microtubules, neurofibrils, Nissl substances, and ribosomes Some neurons like olfactory neurons continue to divide

5 Mosby items and derived items © 2006 by Mosby, Inc. 5 Neuron Three components Cell body (soma) Located mainly in the CNS Densely packed cell bodies in the CNS are nuclei Densely packed cell bodies in the PNS are ganglia Dendrites Receptive portion of the neuron

6 Mosby items and derived items © 2006 by Mosby, Inc. 6 Neuron Axons Carry nerve impulses away from the cell body Axon Hillock Cone-shaped, Nissl-free area, where the axon leaves the cell body Initial segment of the axon Area of the axon having the lowest threshold for stimulation, so the action potentials begin at this point

7 Mosby items and derived items © 2006 by Mosby, Inc. 7 Neuron Axons Myelin Segmented layer of lipid material Insulating substance Formed and maintained by the Schwann cell Endoneurium Delicate layer of connective tissue around each axon Neurilemma Thin membrane between the myelin sheath and the endoneurium

8 Mosby items and derived items © 2006 by Mosby, Inc. 8 Neuron Axons Nodes of Ranvier Regular interruptions of the myelin sheath Saltatory conduction The flow of ions between segments of myelin rather than along the entire length of the axon Divergence Ability of branching axons to influence many neurons Convergence Branches of numerous neurons converging on one or a few neurons

9 Mosby items and derived items © 2006 by Mosby, Inc. 9 Structural Classification of Neurons Based on the number of processes extending from the cell body Unipolar Pseudounipolar Bipolar Multipolar

10 Mosby items and derived items © 2006 by Mosby, Inc. 10 Functional Classification of Neurons Sensory Transmit impulses from sensory receptors to the CNS Associational Transmit impulses from neuron to neuron Motor Transmit impulses from the CNS to an effector organ

11 Mosby items and derived items © 2006 by Mosby, Inc. 11 Neuroglia

12 Mosby items and derived items © 2006 by Mosby, Inc. 12 Neuroglia Nerve glue Support the neurons of the CNS Astrocytes Oligodendroglia (oligodendrocytes) Microglia Ependymal cells

13 Mosby items and derived items © 2006 by Mosby, Inc. 13 Neuroglia

14 Mosby items and derived items © 2006 by Mosby, Inc. 14 Nerve Injury and Regeneration Wallerian degeneration Occurs distal to the cut Swelling appears Neurofilaments hypertrophy Myelin sheath shrinks and disintegrates Axon portion degenerates and disappears

15 Mosby items and derived items © 2006 by Mosby, Inc. 15 Nerve Injury and Regeneration Proximal to the cut Swelling and dispersal of the Nissl substance Cell increases in metabolic activity, protein synthesis, and mitochondrial activity New terminal sprouts project from the proximal segment Process limited to myelinated axons Generally only in the PNS Depends on location, type of injury, the inflammatory response, and scar tissue formation

16 Mosby items and derived items © 2006 by Mosby, Inc. 16 Neuroglia

17 Mosby items and derived items © 2006 by Mosby, Inc. 17 Nerve Impulse Neurons generate and conduct electrical and chemical impulses by selectively changing the electrical portion of their plasma membranes and influencing other nearby neurons by the release of neurotransmitters

18 Mosby items and derived items © 2006 by Mosby, Inc. 18 Synapses Region between adjacent neurons is called a synapse Impulses are transmitted across the synapse by chemical and electrical conduction Presynaptic neurons and postsynaptic neurons Connections between pre- and postsynaptic neurons Axoaxonic Axosomatic Axodendritic Dendrodentritic

19 Mosby items and derived items © 2006 by Mosby, Inc. 19 Synapses

20 Mosby items and derived items © 2006 by Mosby, Inc. 20 Synapses Neurotransmitters >30 substances Excitatory (excitatory postsynaptic potential) Inhibitory (inhibitory postsynaptic potential) Synaptic boutons Synaptic cleft Summation Temporal summation Spatial summation

21 Mosby items and derived items © 2006 by Mosby, Inc. 21 Central Nervous System Forebrain Cerebral hemispheres Midbrain Corpora quadrigemina, tegmentum, and cerebral peduncles Hindbrain Cerebellum, pons, and medulla

22 Mosby items and derived items © 2006 by Mosby, Inc. 22 Central Nervous System Reticular formation Network of connected nuclei that regulate viral reflexes, such as cardiovascular and respiratory function Together with the cerebral cortex is referred to as the reticular activating system

23 Mosby items and derived items © 2006 by Mosby, Inc. 23 Central Nervous System

24 Mosby items and derived items © 2006 by Mosby, Inc. 24 Central Nervous System Forebrain Telencephalon Cerebrum Gyri, sulci, and fissures Gray matter and white matter Cerebral nuclei (basal ganglia)

25 Mosby items and derived items © 2006 by Mosby, Inc. 25 Forebrain

26 Mosby items and derived items © 2006 by Mosby, Inc. 26 Forebrain

27 Mosby items and derived items © 2006 by Mosby, Inc. 27 Central Nervous System Diencephalon Epithalamus Thalamus Hypothalamus Subthalamus

28 Mosby items and derived items © 2006 by Mosby, Inc. 28 Central Nervous System Midbrain Corpora quadrigemina (tectum) Superior and inferior colliculi Tegmentum Red nucleus and substantia nigra Basis pedunculi

29 Mosby items and derived items © 2006 by Mosby, Inc. 29 Central Nervous System Hindbrain (metencephalon) Cerebellum Pons Myelencephalon Medulla oblongata

30 Mosby items and derived items © 2006 by Mosby, Inc. 30 Central Nervous System

31 Mosby items and derived items © 2006 by Mosby, Inc. 31 Spinal Cord Lies within the vertebral canal and is protected by the vertebral column Connects the brain and the body Conducts somatic and autonomic reflexes Provides motor pattern control centers Modulates sensory and motor function

32 Mosby items and derived items © 2006 by Mosby, Inc. 32 Spinal Cord

33 Mosby items and derived items © 2006 by Mosby, Inc. 33 Spinal Cord

34 Mosby items and derived items © 2006 by Mosby, Inc. 34 Spinal Cord

35 Mosby items and derived items © 2006 by Mosby, Inc. 35 Reflex Arc Receptor Afferent (sensory) neuron Efferent neuron Effector

36 Mosby items and derived items © 2006 by Mosby, Inc. 36 Reflex Arc

37 Mosby items and derived items © 2006 by Mosby, Inc. 37 Upper and Lower Motor Neurons Upper motor neurons Efferent pathways primarily relaying information from the cerebrum to the brain stem or spinal cord Synapse with interneurons Lower motor neurons Neurons having direct influence on muscles Cell bodies originate in the gray matter of the spinal cord, but their axons extend into the PNS

38 Mosby items and derived items © 2006 by Mosby, Inc. 38 Neuromuscular Junction

39 Mosby items and derived items © 2006 by Mosby, Inc. 39 Motor Pathways Lateral corticospinal Corticobulbar Basal ganglia Vestibulospinal

40 Mosby items and derived items © 2006 by Mosby, Inc. 40 Sensory Pathways Anterior spinothalamic Lateral spinothalamic

41 Mosby items and derived items © 2006 by Mosby, Inc. 41 Protective Structures Cranium Eight bones Frontal Occipital Temporal (2) Parietal (2) Sphenoid Ethmoid Galea aponeurotica

42 Mosby items and derived items © 2006 by Mosby, Inc. 42 Protective Structures Meninges Protective membranes surrounding the brain and spinal cord Dura mater Arachnoid Pia mater

43 Mosby items and derived items © 2006 by Mosby, Inc. 43 Meninges

44 Mosby items and derived items © 2006 by Mosby, Inc. 44 Protective Structures Cerebrospinal fluid (CSF) and the ventricular system CSF is a clear, colorless fluid similar to blood plasma and interstitial fluid 125 to 150 mL Produced by the choroid plexuses in the lateral, third, and fourth ventricles Reabsorbed through the arachnoid villi

45 Mosby items and derived items © 2006 by Mosby, Inc. 45 Protective Structures Vertebral column 33 vertebrae 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 4 fused coccygeal Intervertebral disks Nucleus pulposus

46 Mosby items and derived items © 2006 by Mosby, Inc. 46 Vertebral Column

47 Mosby items and derived items © 2006 by Mosby, Inc. 47 Vertebral Column

48 Mosby items and derived items © 2006 by Mosby, Inc. 48 Blood Supply to the Brain 800 to 1000 mL per minute CO 2 is the primary regulator for CNS blood flow Internal carotid and vertebral arteries Arterial circle (circle of Willis)

49 Mosby items and derived items © 2006 by Mosby, Inc. 49 Blood Supply to the Brain

50 Mosby items and derived items © 2006 by Mosby, Inc. 50 Blood Supply to the Brain

51 Mosby items and derived items © 2006 by Mosby, Inc. 51 Blood Supply to the Brain

52 Mosby items and derived items © 2006 by Mosby, Inc. 52 Blood Supply to the Brain

53 Mosby items and derived items © 2006 by Mosby, Inc. 53 Blood Supply to the Spinal Cord Vertebral arteries Anterior spinal arteries Posterior spinal arteries Aorta

54 Mosby items and derived items © 2006 by Mosby, Inc. 54 Blood Supply to the Spinal Cord

55 Mosby items and derived items © 2006 by Mosby, Inc. 55 Peripheral Nervous System 31 pairs of spinal nerves Names correlate with the vertebral level from which they exit Mixed nerves Arise from the anterior and posterior horn cells of the spinal cord 12 pairs of cranial nerves Sensory, motor, and mixed

56 Mosby items and derived items © 2006 by Mosby, Inc. 56 Peripheral Nervous System Fascicles Bundles of myelinated axons in the PNS Rami Plexuses Brachial plexus Lumbar plexus Sacral plexus Dermatomes

57 Mosby items and derived items © 2006 by Mosby, Inc. 57 Peripheral Nervous System

58 Mosby items and derived items © 2006 by Mosby, Inc. 58 Autonomic Nervous System Located in both the CNS and PNS Coordinates and maintains a steady state among the visceral (internal) organs Neurons Preganglionic (myelinated) Postganglionic (unmyelinated) Two divisions Sympathetic Parasympathetic

59 Mosby items and derived items © 2006 by Mosby, Inc. 59 Sympathetic Nervous System Mobilizes energy stores in times of need Fight or flight response Receives innervation from cell bodies located from the first thoracic through the second lumbar Thoracolumbar division Sympathetic (paravertebral) ganglia

60 Mosby items and derived items © 2006 by Mosby, Inc. 60 Sympathetic Nervous System

61 Mosby items and derived items © 2006 by Mosby, Inc. 61 Parasympathetic Nervous System Functions to conserve and restore energy Rest or repose response Receives innervation from cell bodies located in the cranial nerve nuclei and sacral region of the spinal cord Craniosacral division Preganglionic neurons travel to ganglia close to the organs they innervate

62 Mosby items and derived items © 2006 by Mosby, Inc. 62 Parasympathetic Nervous System

63 Mosby items and derived items © 2006 by Mosby, Inc. 63 Neurotransmitters and Neuroreceptors of the ANS Sympathetic preganglionic fibers Acetylcholine and cholinergic receptors Sympathetic postganglionic fibers Norepinephrine and adrenergic receptors Parasympathetic pre- and postganglionic fibers Acetylcholine and cholinergic receptors

64 Mosby items and derived items © 2006 by Mosby, Inc. 64 Neurotransmitters and Neuroreceptors of the ANS

65 Mosby items and derived items © 2006 by Mosby, Inc. 65 Aging and the Nervous System Decrease in the number of neurons Decreased brain weight and size Senile plaques Neurofibrillary tangles Slowing of neurologic responses

66 Mosby items and derived items © 2006 by Mosby, Inc. 66 Tests of Nervous System Function Skull and spine roentgenograms Computed tomography Magnetic resonance imaging Magnetic resonance angiography Positron emission tomography scan Brain scan Cerebral angiography

67 Mosby items and derived items © 2006 by Mosby, Inc. 67 Tests of Nervous System Function Myelography Echoencephalography (ultrasound) Electroencephalography Evoked potentials Cerebrospinal fluid analysis


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