Chapter 8 Nervous System I Cell Types of Neural Tissue neurons neuroglial cells 8-1

Divisions of the Nervous System Central Nervous System brain spinal cord Peripheral Nervous System peripheral nerves cranial nerves spinal nerves 8-2

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 8-3

Functions of Nervous System Sensory Function sensory receptors gather information information is carried to the CNS sensory neurons- afferent Motor Function decisions are acted upon impulses are carried to effectors motor neurons Integrative Function interneurons sensory information used to create sensations memory thoughts decisions 8-4

Neuron Structure 8-5

Myelination of Axons White Matter contains myelinated axons Gray Matter contains unmyelinated structures cell bodies, dendrites 8-6

Classification of Neurons Sensory Neurons afferent carry impulse to CNS Interneurons link neurons in CNS Motor Neurons carry impulses away from CNS carry impulses to effectors 8-7

The Synapse Nerve impulses pass from neuron to neuron at synapses 8-8

Synaptic Transmission Neurotransmitters are released when impulse reaches synaptic knob 8-9

Reflex Arcs Reflexes – automatic, subconscious responses to stimuli 8-10

Brain Functions interprets sensations determines perception stores memory reasoning makes decisions coordinates muscular movements regulates visceral activities determines personality Major Parts cerebrum two cerebellar hemispheres diencephalon brain stem cerebellum 8-11

Brain Stem Three Parts Pons Medulla Oblongata Midbrain 8-12

Pons helps regulate rate and depth of breathing relays nerve impulses to and from medulla oblongata and cerebellum 8-13

Medulla Oblongata enlarged continuation of spinal cord conducts ascending and descending impulses between brain and spinal cord contains cardiac, vasomotor, and respiratory control centers contains various nonvital reflex control centers (coughing, sneezing, vomiting) 8-14

Reticular Formation filters incoming sensory information arouses cerebral cortex into state of wakefulness 8-15

Diencephalon Thalamus gateway for sensory impulses heading to cerebral cortex receives all sensory impulses (except smell) channels impulses to appropriate part of cerebral cortex for interpretation Hypothalamus maintains homeostasis by regulating visceral activities temperature sleep-wake cycles water balance appetite links nervous and endocrine systems 8-16

Cerebellum posterior to pons and medulla oblongata inferior to occipital lobes posterior to pons and medulla oblongata integrates sensory information concerning position of body parts coordinates skeletal muscle activity maintains posture 8-17

Lobes of Cerebrum Frontal Parietal Temporal Occipital 8-18

Structure of Cerebrum cerebral cortex corpus callosum connects hemispheres convolutions bumps or gyri sulci grooves longitudinal fissure separates hemispheres transverse fissure separates cerebrum from cerebellum 8-19

Functions of Cerebrum interpretation initiating voluntary movements storing memory retrieving memory reasoning center for intelligence and personality 8-20

Motor and Sensory Areas Primary Motor Areas frontal lobes control voluntary muscles Cutaneous Sensory Area parietal lobe interprets sensations on skin Visual Area occipital lobe interprets vision Auditory Area temporal lobe interprets hearing 8-21

Hemisphere Dominance In over 90% of population, left hemisphere is dominant Nondominant hemisphere controls nonverbal tasks motor tasks understanding and interpreting musical and visual patterns provides emotional and intuitive thought processes Dominant hemisphere controls speech writing reading verbal skills analytical skills computational skills 8-22

Memory Short Term working memory circuit is stimulated over and over when impulse flow stops, memory disappears Long Term changes structure and function of neurons enhanced synaptic transmission strong emotion, repetition, and building on previous memories stimulate 8-23

Spinal Cord Functions center for spinal reflexes conduit for nerve impulses to and from the brain 8-24

Spinal Cord Structure extends foramen magnum to 2nd lumbar vertebra 8-25

Meninges Meninges membranes surrounding CNS protect CNS three layers dura mater – outer, tough arachnoid mater - weblike pia mater – inner, delicate 8-26

Cerebrospinal Fluid secreted by choroid plexus circulates in ventricles, central canal of spinal cord, and subarachnoid space completely surrounds brain and spinal cord clear liquid nutritive and protective helps maintain stable ion concentrations in CNS 8-27

Peripheral Nervous System Cranial nerves arising from the brain Somatic fibers connecting to the skin and skeletal muscles Autonomic fibers connecting to viscera Spinal nerves arising from the spinal cord Somatic fibers connecting to the skin and skeletal muscles Autonomic fibers connecting to viscera 8-28

Cranial Nerves 8-29

Spinal Nerves mixed nerves 31 pairs 8 cervical (C1 to C8) 12 thoracic (T1 to T12) 5 lumbar (L1 to L5) 5 sacral (S1 to S5) 1 coccygeal (Co) 8-30

Autonomic Nervous System functions without conscious effort controls visceral activities regulates smooth muscle, cardiac muscle, and glands efferent fibers typically lead to ganglia outside CNS Two Divisions sympathetic – prepares body for fight or flight situations parasympathetic – prepares body for resting and digesting activities 8-31