Chapter 9 Notes

Chapter 9 The Nervous System I. Functions of the Nervous System A. Sensory Input- gathering information 1. To monitor changes occurring inside and outside the body B. Integration 1. To process and integrate sensory input and decide if action is needed C. Motor Output 1. A response to integrated stimuli 2. The response activates muscles or glands II. Structural Classifications of the Nervous System A. Central Nervous System (CNS) 1. Brain 2. Spinal Cord B. Peripheral Nervous System (PNS) 1. Nerves outside the brain and spinal cord III. Functional Classification of the PNS A. Sensory (afferent) division 1. Nerve fibers that carry impulses to the CNS B. Motor (efferent) division 1. Nerve fibers that carry impulses away from the CNS 2. Two subdivisions a. Somatic Nervous System = voluntary b. Autonomic Nervous System = involuntary C. Nervous Tissue: support cells (Neuroglia) 1. Astrocytes a. Abundant, star shaped cells b. Brace Neutrons c. Form barrier between capillaries and neutrons d. Control the chemical environment of the brain 2. Microglia a. Spider-like cells b. Dispose of debris 3. Ependymal Cells a. Line cavities of the brain and spinal cord b. Circulate cerebrospinal fluid

4. Oligodendrocytes a. Produce myelin sheath around nerve fibers in CNS 5. Satellite Cells a. Protect neurons cell bodies 6. Schwann Cells a. Form myelin sheath in the PNS D. Neurons (Nervous Tissue) 1. Nerve Cells a. Cells specialized to transmit messages b. Major regions of neurons 1. All body- nucleus and metabolic center of cell 2. Contains a nucleus and a large nucleolus 3. Processes- fibers that extend from the cell body 2. Dendrites a. An extension outside the cell body that conducts impulses toward the cell body 3. Axons a. Conduct impulses away from the cell body b. End in axonal terminals 1. Contains vesicles with neurotransmitters 2. Separated from the next neuron by a gap called a synaptic cleft (a) Synaptic cleft- gap between adjacent neurons (b) Synapse- junction between nerves E. Nerve Fibers Coverings 1. Schwann Cells a. Produce myelin sheaths in jelly-roll like fashion 2. Nodes of Ranvier a. Gaps in myelin sheath along the axon F. Neuron Cell Body Location 1. Most are found in the CNS a. Gray matter-cell bodies and unmyelinated fibers b. Nuclei- clusters of cell bodies within the white matter of the CNS IV. Classification of Neurons A. Sensory (Afferent) neurons 1. Carry impulses from the sensory receptors B. Motor (Efferent) neurons

1. Carry impulses from the CNS C. Interneuron (Association neuron) 1. Connect sensory and motor neurons 2. Found in neutral pathways in the CNS V. Structural Classification of Neurons A. Multipolar Neurons 1. Many extensions from the cell body B. Bipolar Neurons 1. One axon and one dendrite C. Unipolar Neurons 1. Have a short single process leaving the cell body VI. Functional Properties of Neurons A. Irritability 1. The ability to respond to stimuli B. Conductivity 1. Ability to transmit an impulse C. Plasma Membrane at rest is polarized 1. Fewer positives ions are inside the cell than outside the cell VII. Starting a Nerve Impulse A. Depolarization 1. A stimulus depolarizes the neuron’s membrane 2. A depolarized membrane allows sodium (Na+) to flow inside the membrane 3. The exchange of ions initiates an action potential in the neuron B. Action Potential 1. If the action potential (nerve impulse) starts, it is carried over the entire axon 2. Potassium (K) ions rush out of the neuron after sodium ions rush in which repolarizes the membrane 3. The sodium-potassium pump restores the original configuration a. This requires ATP VIII. Nerve Impulse Propagation A. The impulse continues to move toward the cell body B. Impulses travel faster when fibers have a myelin sheath C. Impulses are able to cross the synapse to another nerve 1. Neurotransmitter is released from a nerve’s axonal terminal 2. The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter

3. An action potential is started in the dendrite D. The Reflexes are: 1. Reflex-rapid, predictable, and involuntary responses to stimuli 2. Reflexare- direct route form a sensory neuron to an interneuron to an effector 3. Types of reflexes and regulation a. autonomic reflexes -smooth muscle regulation -heart and blood pressure regulation -regulation of glands -digestive system regulation b. somatic reflexes -activation of skeletal muscle IX. Central Nervous System (CNS) A. CNS develops from the entropic neural tube 1. The neural tube becomes the brain and spinal cord 2. The opening of the neural tube becomes the ventricles a. four chambers within the brain b. filled with cerebrospinal fluid B. Regions of the brain 1. Cerebral hemisphere (Cerebrum) a. paired (left and right) superior parts of the brain b. include more than half of the brain mass c. surface is made of ridges (gyri) and grooves (sulci) d. Lobes of cerebrum -fissures (deep grooves) divide the cerebrum into lobes -surface lobes of the cerebrum -frontal lobe -parietal lobe -occipital lobe -temporal lobe 2. Specialized areas of the cerebrum a. somatic sensory area- receives impulses from the body’s sensory receptors b. primary motor area- sends impulses to skeletal muscles c. Broca’s area- involved in our ability to eat d. Cerebral areas involved in special senses: -gustatory area (taste)

-visual area -auditory area -olfactory area e. interpretation areas of the cerebrum -speech/language region -language comprehension region -general information area 3. Layers of the cerebrum a. gray water -outer layers -composed mostly of neuron cell bodies b. white matter -fiber tracts inside the gray matter -example: corpus callous connects hemispheres c. Basal nuclei -internal islands of gray matter X. Diencephation A. Sits on top of the brain stem B. Enclosed by the cerebral hemispheres C. Made of 3 parts D. Thalamus 1. Surrounds the third ventricle 2. The relay station for sensory impulses 3. Transfers impulses to fine correct part of the cortex for localization and interpretation E. Hypothalamus 1. Under the thalamus 2. Important autonomic nervous system center a. helps regulate body temp. b. controls water balance c. regulates metabolism d. important part of the limbic system (emotions) e. attachment site for the pituitary gland F. Epithalamus 1. Forms the roof of the third ventricle 2. Houses the pineal body (an endocrine gland) 3. Includes the choroids plexus- forms cerebrospinal fluid G. Brain Stem

1. Attaches to the spinal cord 2. Parts of the brain stem a. midbrain b. mostly composed of tracts of nerve fibers c. has two bulging fiber tracts of nerve fibers- cerebral procedures peduncles d. has four rounded protrusions -corpora quadrigemia -reflex centers for vision and hearing H. Pons 1. The bulging center part of the brain stem 2. Mostly composed of fiber tracts 3. Includes nuclei involved in the control of breathing I. Medulla Oblongata 1. The lowest part of the brain stem 2. Merges into the spinal cord 3. Includes important control centers a. heart rate control b. blood pressure regulation c. breathing d. swallowing e. vomiting J. Cerebellum 1. Associated with regulation and coordination of movement, posture, and balance