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Nervous Control of Muscular Movement -- Fill in the blanks style lecture notes with occasional extras about what was especailly important to remember and some further explanations.

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Biomedical Physio & Kines
BPK 142
Paul Lee

1 NERVOUS CONTROL OF MUSCULAR MOVEMENT STRUCTURE AND FUNCTION OF THE NERVOUS SYSTEM Divisions of The Nervous System A. Central Nervous System 1. Brain - newer more sophisticated regions are piled on _____ of older, more primitive regions a) Forebrain (i) ___Cerebrum____ constitutes about 80% of total brain weight - cerebral cortex, basal nuclei (ii) Diencephalon - thalamus, hypothalamus b) Cerebellum c) __Brainstem____ - continuous with the spinal cord - medulla, pons, midbrain 2. Spinal cord - long cylinder of nerve tissue which extends down from the __brainstem__ to the second ___lumbar___ vertebrae. 45 cm long and 2 cm in diameter. - Protected by the vertebral column and associated ligaments and muscles, the spinal meninges and the cerebrospinal fluid. B. Peripheral Nervous System Consists of 12 pairs of __cranial__ nerves and 31 pairs of __spinal__ nerves 1. Afferent division - conveys information from the ___sensors__ in the periphery to the central nervous system (CNS) 2. Efferent division a) _Somatic__ nervous system - nerve fibers innervate _skeletal muscle__ b) _Autonomic__ nervous system - nerve fibers innervate _smooth___ and __cardiac__ muscle and glands (i) sympathetic division [Stress, Fight/Flight – increase activity] 2 (ii) parasympathetic division [Normal functions, opposite of stress response –decrease activity] Neuroglia – comprise about _90%__ of the cells within the CNS. They occupy about __half__ of the volume of the brain. The four major types of glial cells serve as the __connective____ tissue of the CNS and as such help support the neurons both __physically____ and __metabolically_____. It is estimated that there are approximately 100 billion neurons in the brain and one trillion neuroglia. (More Neuroglia than neurons!) Along with the endocrine system, the nervous system regulates and coordinates the various functions of the body. Basic Structure of a Nerve Neuron – a nerve cell. Neurons are specialized to transmit __electrical___ signals. It consists of: 1. Cell body - soma - contains the _nucleus___ 2. Axon - a long fiber that conducts impulses __away__ from the cell body. The term "____nerve fiber____" is generally used in reference to an axon. 3. Dendrite - short projections from the cell body that transmit impulses __toward____ the cell body The main purpose of the neuron is to pass messages (impulses) from one part of the body to another Myelin sheath - a discontinuous sheath around the axon. It is composed mainly of __lipid___ and _______protein__. Nodes of Ranvier - spaces between the segments of myelin sheath  ___saltatory_____ conduction Myelinated nerve fibers have much __faster__ conduction velocities than unmyelinated fibers 3 Synapse – the connection of an axon of one nerve to the cell body or dendrites of another nerve. Neurons can be divided into 3 functional classes: 1. Afferent neurons - carry impulses from the ___sensory___ receptors into spinal cord or brain 2. Efferent neurons - transmit impulses from the CNS out to the ___effector______ organs such as muscles (motor neurons) and glands 4 3. Interneurons - lie entirely within the __CNS__. They account for _99_% of all nerve cells. Each spinal nerve is actually a nerve __trunk___ - it contains hundreds of individual afferent and efferent nerve fibers that are bound together by connective tissue sheaths. The Nerve Impulse Resting membrane potential - due to the __selective___ permeability characteristics of the nerve cell membrane, a potential (voltage) __difference__ exists between the inside and outside of the nerve fiber. A high concentration of positive __sodium___ ions on the outside of the nerve membrane causes it to be electrically ___positive___, while the inside of the nerve is electrically __negative____. Action potential - an appropriate stimulus suddenly causes _sodium__ ions to rush to the inside of the nerve  reversal of polarity. Once the action potential is _started__, it spreads along the entire length of the nerve fiber Nerve to Nerve Synapses Nervous information is relayed across the ____synaptic cleft____ by means of a chemical transmitter substance. Transmitter substances can be either ___excitatory_____ or ___inhibitroy____ in their effects on the post synaptic membrane potential [either creates an action potential or inhibits an action potential] Spatial vs. temporal summation Neuromuscular junction - nerve to __muscle__ synapse. The chemical transmitter substance is ___acetylcholine____. Spinal Cord The spinal cord is enlarged in two regions for innervation of the limbs: 5 a) The __cervical___ enlargement which extends from the C4 through T1 segments of the spinal cord b) The __lumbosacral____ enlargement which extends from the T11 through L1 segments of the spinal cord Plexus – a network of converging and diverging nerve fibers, or blood vessels. The brain and spinal cord are composed of gray matter and white matter. The nerve cell bodies lie in and constitute the _gray__ matter while the interconnecting tracts of nerve fibers (axons) form the __white___ matter. Structure of spinal nerves – 31 pairs of spinal nerves are attached to the spinal cord – _8_ cervical, 12 thoracic, 5 lumbar, 5 sacral _1_coccygeal Each spinal nerve has a __dorsal___ root and a __ventral__ root connected to the spinal cord. The dorsal roots contain __afferent___ (sensory) fibers that carry information from the periphery to the spinal cord and brain. The ventral roots contain ___efferent___ (motor) fibers to the skeletal muscle. The cell bodies of the motor axons making up the __ventral___ roots are located in the ventral gray horns of the spinal cord The cell bodies of the sensory axons making up the __dorsal___ roots are outside of the spinal cord in the spinal __ganglia__. Ganglion – a collection of nerve cell _bodies__ located outside of the CNS. Spinal cord injury – transection of the spinal cord results in loss of all sensatio
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