Chapter 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

10.1: Introduction Cell types in neural tissue: Neurons Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell types in neural tissue: Neurons Neuroglial cells (also known as neuroglia, glia, and glial cells) Dendrites Cell body Nuclei of neuroglia Axon © Ed Reschke

Divisions of the Nervous System Central Nervous System (CNS) Brain Spinal cord Peripheral Nervous System (PNS) Cranial nerves Spinal nerves

Divisions of Peripheral Nervous System Sensory Division Picks up sensory information and delivers it to the CNS Motor Division Carries information to muscles and glands Divisions of the Motor Division: Somatic – carries information to skeletal muscle Autonomic – carries information to smooth muscle, cardiac muscle, and glands

Divisions Nervous System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central Nervous System (brain and spinal cord) Peripheral Nervous System (cranial and spinal nerves) Brain Cranial nerves Sensory division Sensory receptors Spinal cord Spinal nerves Motor division Somatic Nervous System Skeletal muscle Autonomic Nervous System Smooth muscle Cardiac muscle Glands (a) (b)

10.2: General Functions of the Nervous System The three general functions of the nervous system: Receiving stimuli = sensory function Deciding about stimuli = integrative function Reacting to stimuli = motor function

Functions of Nervous System Sensory Function Sensory receptors gather information Information is carried to the CNS Integrative Function Sensory information used to create: Sensations Memory Thoughts Decisions Motor Function Decisions are acted upon Impulses are carried to effectors

10.3: Description of Cells of the Nervous System Neurons vary in size and shape They may differ in length and size of their axons and dendrites Neurons share certain features: Dendrites A cell body An axon

Neuron Structure Chromatophilic substance (Nissl bodies) Dendrites Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chromatophilic substance (Nissl bodies) Dendrites Cell body Nucleus Nucleolus Neurofibrils Axonal hillock Impulse Axon Synaptic knob of axon terminal Nodes of Ranvier Myelin (cut) Schwann cell Nucleus of Schwann cell Axon Portion of a collateral

Myelination of Axons White Matter Contains myelinated axons Considered fiber tracts Gray Matter Contains unmyelinated structures Cell bodies, dendrites Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dendrite Unmyelinated region of axon Myelinated region of axon Node of Ranvier Axon Neuron cell body Neuron nucleus (a) Enveloping Schwann cell Schwann cell nucleus Longitudinal groove Unmyelinated axon (c)

10.4: Classification of Neurons and Neuroglia Neurons vary in function They can be sensory, motor, or integrative neurons Neurons vary in size and shape, and in the number of axons and dendrites that they may have Due to structural differences, neurons can be classified into three (3) major groups: Bipolar neurons Unipolar neurons Multipolar neurons

Classification of Neurons: Structural Differences Bipolar neurons Two processes Eyes, ears, nose Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dendrites Unipolar neurons One process Ganglia of PNS Sensory Peripheral process Axon Multipolar neurons 99% of neurons Many processes Most neurons of CNS Direction of impulse Central process Axon Axon (a) Multipolar (b) Bipolar (c) Unipolar

Classification of Neurons: Functional Differences Sensory Neurons Afferent Carry impulse to CNS Most are unipolar Some are bipolar Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central nervous system Peripheral nervous system Cell body Dendrites Sensory receptor Interneurons Link neurons Aka association neurons or internuncial neurons Multipolar Located in CNS Cell body Axon (central process) Axon (peripheral process) Sensory (afferent) neuron Interneurons Motor (efferent) neuron Axon Effector (muscle or gland) Axon Motor Neurons Multipolar Carry impulses away from CNS Carry impulses to effectors Axon terminal

Types of Neuroglial Cells in the PNS 1) Schwann Cells Produce myelin found on peripheral myelinated neurons Speed up neurotransmission 2) Satellite Cells Support clusters of neuron cell bodies (ganglia)

Types of Neuroglial Cells in the CNS 1) Microglia CNS Phagocytic cell 3) Oligodendrocytes CNS Myelinating cell 2) Astrocytes CNS Scar tissue Mop up excess ions, etc. Induce synapse formation Connect neurons to blood vessels Part of Blood Brain Barrier 4) Ependyma or ependymal CNS Ciliated Line central canal of spinal cord Line ventricles of brain

Types of Neuroglial Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fluid-filled cavity of the brain or spinal cord Neuron Ependymal cell Oligodendrocyte Astrocyte Microglial cell Axon Myelin sheath (cut) Capillary Node of Ranvier

Regeneration of A Nerve Axon Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Motor neuron cell body Skeletal muscle fiber Changes over time Site of injury Schwann cells Axon (a) Distal portion of axon degenerates (b) Proximal end of injured axon regenerates into tube of sheath cells (c) Schwann cells degenerate (d) Schwann cells proliferate (e) Former connection reestablished

10.5: The Synapse Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nerve impulses pass from neuron to neuron at synapses, moving from a pre-synaptic neuron to a post-synaptic neuron. Synaptic cleft Impulse Dendrites Axon of presynaptic neuron Axon hillock of Postsynaptic neuron Axon of presynaptic neuron Cell body of postsynaptic neuron Impulse Impulse

Synaptic Transmission Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Direction of nerve impulse Neurotransmitters are released when impulse reaches synaptic knob Synaptic vesicles Axon Presynaptic neuron Ca+2 Ca+2 Synaptic knob Cell body or dendrite of postsynaptic neuron Mitochondrion Synaptic vesicle Ca+2 Vesicle releasing neurotransmitter Axon membrane Neurotransmitter Synaptic cleft Polarized membrane Depolarized membrane (a)