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This 31 page Class Notes was uploaded by Corina Johnson on Tuesday February 23, 2016. The Class Notes belongs to 10584 at University of Houston taught by Dr. Lawrence Williams in Spring 2016. Since its upload, it has received 22 views. For similar materials see General Biology in Biology at University of Houston.
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Date Created: 02/23/16
NERVOUS SYSTEM FUNCTION: high speed communication system for coordinating and controlling activity of the body. HISTOLOGY: GLIAL CELLS: support and protection. Example: Schwann cell NEURONS: functional unit of the system; they conduct impulses. NEURON STRUCTURE and FUNCTION • STRUCTURE: cell body, dendrite, axon. • FUNCTION: must examine resting and action states of the neuron. • Resting conditions of a neuron NEURON: resting state • High concentration of Na+ (sodium ions) outside the cell. • High concentration of K+ (potassium ions) inside the cell. • Leakage of Na+ and K+ corrected by a Na/K pump. • Leakage of K+ draws negatively charged organic molecules to the cell membrane. • An electrical potential is established across the cell membrane. NEURON: action state • Cell membrane is stimulated, Na+ gates open, and the membrane becomes permeable to Na+. Na+ rush into the cell. • Electrical potential of membrane reverses (this is the impulse). • Impulse continues down the neuron in the direction of the axon. • Immediately after the impulse passes, the cell membrane begins recovery: Na+ gates close, Na/K pumps restore resting state concentrations of Na+ and K+. Graphical representation of neuron function (fig. 28.04) TYPES OF IMPULSES • CONTINUOUS IMPULSE. • SALTATORIAL IMPULSES. TYPES OF NEURONS • MOTOR (efferent): carry impulses away from the central nervous system (CNS, brain and spinal cord). • SENSORY (afferent): carry impulses to the CNS. • ASSOCIATION (interneurons): interconnecting neurons for sensory and motor neurons. Speed of impulses • TYPE A FIBERS, large diameter: – SALTATORY IMPULSES WITH SHORT REFRACTORY PERIOD. – 130 M/S – LARGE SENSORY NERVES FOR TOUCH, PRESSURE, TEMPERATURE, AND POSTISION OF JOINTS AND MOTOR NEURONS THAT RESPOND TO SUCH INFORMATION. SURVIVAL CURCUITS. Speed of impulses • TYPE B FIBERS; mid size diameter – SALTATORY IMPULSES, SHORT REFRACTORY PERIOD. – 10 M/S – SOME SKIN AND VISCERA SENSORY TO BRAIN AND SPINAL CORD, AND MOTOR FIBERS FOR SMOOTH MUSCLE AND GLANDS OF THE VISCERA. Speed of impulses • TYPE C FIBERS; smallest diameter: – CONTINUOUS IMPULSES. – 0.5 M/S – GENERALLY SAME CURCUITS AS TYPE B FIBERS, BUT OF LESSER IMPORTANCE. How do neurons communicate? The space between communicating travel from a pre-synaptic neuron to as post-synaptic neuron. Two neurons that communicate are said to “synapse.” Communication across the synaptic cleft is chemical called neurotranmittors. INTERNEURONAL COMMUNICATION INTERNEURONAL COMMUNICATION INTERNEURONAL COMMUNICATION Variation in synaptic communication • EXCITATORY POST-SYNAPTIC POTENTIAL (EPSP). The post-synaptic neuron is hypo-polarized or slightly depolarized. • INHIBITORY POST-SYNAPTIC POTENTIAL (IPSP). The post-synaptic neuron is hyper- polarized or over-polarized. TYPES OF CURCUITS • Simple; reflexes. • Divergent; control of a muscle. • Convergent; 1) certainty of communication or 2) communication from different sources. • Reverberating; short-term memory. • Alternating after-shock; mathematical function. Nervous System Organization CENTRAL NS Brain Spinal cord PERIPHERAL NS Afferent (sensory) Efferent (motor) Somatic (skeletal muscle) Autonomic (smooth muscle, viscera, glands). Has two antagonistic systems. Sympathetic (fight or flight); norepinephrin Parasympathetic (rest or response); acetylcholine.
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