Basics of the Nervous System Chapter 10 Basics of the Nervous System 10-1

Chapter 10 Nervous System I Composed mainly of neural tissue Cell Types of Neural Tissue neurons transmit impulses neuroglial cells assist neurons 10-2

Divisions of the Nervous System Central Nervous System brain spinal cord Peripheral Nervous System peripheral nerves cranial nerves spinal nerves 10-1

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 Somatic – carries information to skeletal muscle Autonomic – carries information to smooth muscle, cardiac muscle, and glands 10-4

Divisions Nervous System 10-5

Functions of Nervous System Sensory Function sensory receptors gather information information is carried to the CNS Motor Function decisions are acted upon impulses are carried to effectors Integrative Function sensory information used to create sensations memory thoughts decisions 10-6

Neuron Structure 10-7

Myelination of Axons White Matter contains myelinated axons (lipid) Gray Matter contains unmyelinated structures 10-8

Classification of Neurons based on shape Multipolar many processes most neurons of CNS Bipolar two processes eyes, ears, nose Unipolar one process ganglia 10-9

Classification of Neurons based on function Sensory Neurons carry impulse to CNS (afferent) most are unipolar some are bipolar Interneurons link neurons/ neuronal pathways multipolar in CNS Motor Neurons carry impulses away from CNS (efferent) multipolar carry impulses to effectors 10-10

Types of Neuroglial Cells provide scaffolding, position neurons, remove ions/neurotransmitters, produce growth factors Schwann Cells PNS myelinating cell Astrocytes CNS scar tissue mop up excess ions, etc induce synapse formation connect neurons to blood vessels Oligodendrocytes CNS myelinating cell Ependyma CNS ciliated line central canal of spinal cord line ventricles of brain Microglia CNS phagocytic cell (immune) 10-11

Types of Neuroglial Cells 10-12

Regeneration of A Nerve Axon 10-13

Resting Membrane Potential Before stimulation, nerve must be in its resting potential Active transport keeps sodium (Na+) ions out and potassium (K+) ions inside cell inside is negative relative to the outside (because of other ions); negative inside/positive outside polarized membrane due to distribution of ions Na+/K+ pump 10-14

Potential Changes at rest membrane is polarized (- in) threshold stimulus reached (causes action potential) sodium channels open and membrane depolarizes (Na rushes in) Creates momentary hyperpolarization (+ in) potassium channels open and membrane repolarizes (K rushes out) (- in) Na is now in and K is now out whole process takes 1/1000 of a second 10-15

Action Potentials An action potential in one region stimulates an action potential in the adjacent region Action potential travels down axon (one way) 10-18

Action Potentials/Nerve Impulse caused by various stimuli chemicals temperature changes mechanical forces occur on dendrites, cell bodies, and axons all-or-none refractory period absolute - time when threshold stimulus does not start another action potential relative – time when stronger threshold stimulus can start another action potential 10-17

Saltatory Conduction Action potential occurs only at nodes, jumps from node to node Myelin and diameter of fiber determine speed of potential. Thick/myelinated fiber- 120 meters/sec ; thin/unmyelinated- 0.5 meters/sec 10-20

The Synapse Nerve impulses pass from neuron to neuron at synapses – space between neurons 10-21

Synaptic Transmission Neurotransmitters are released when impulse reaches synaptic knob 10-22

Neurotransmitters 10-25

Impulse Processing Neuronal Pools groups of interneurons that make synaptic connections with each other interneurons work together to perform a common function each pool receives input from other neurons each pool generates output to other neurons 10-26

Convergence neuron receives input from several neurons incoming impulses represent information from different types of sensory receptors allows nervous system to collect, process, and respond to information makes it possible for a neuron to sum impulses from different sources 10-27

Divergence one neuron sends impulses to several neurons can amplify an impulse impulse from a single neuron in CNS may be amplified to activate enough motor units needed for muscle contraction 10-28