PHYSIOLOGY OF NERVE AND MUSCLE CELLS

O B J E C T I V E S :
AT THE END OF THE LECTURE YOU SHOULD BE ABLE TO
•Clarify the transport properties of the resting nerve membrane .
•Explain the normal resting membrane potential.
•Describe the structure of a neuron and name its parts and their functions.
•Explain the functional significance of the principal regions of a neuron.
•The human central nervous system (CNS) contains about 1011 (100 billion) neurons.
•It also contains 10–50 times this number of glial cells.
•The neurons are the basic building block of the nervous system.
•Most neurons have the same parts as the typical spinal motor neuron (Figure).
NERVE CELL (NEURON):
i.The cell body (soma) contains the nucleus and is the metabolic center of the neuron.
ii.Neurons have several processes called dendrites that extend outward from the cell body and arborize extensively.
iii.A typical neuron also has a long fibrous axon that originates from a somewhat thickened area of the cell body, the axon hillock;
•The first portion of the axon is called the initial segment.
•The axon divides into presynaptic terminals, each ending in a number of synaptic knobs which are also called terminal buttons or boutons;
•Terminal boutons (contain granules or vesicles in which the synaptic transmitters are stored).
NERVE CELL (NEURON):
•From a functional point of view, neurons generally have four important zones:
(1) a receptor, or dendritic zone,
•where multiple local potential changes generated by synaptic connections are integrated;
(2) a site where propagated APs are generated
•(the initial segment in spinal motor neurons),
•(the initial node of Ranvier in cutaneous sensory neurons);
(3) an axonal process
•that transmits propagated impulses to the nerve endings; and
(4) the nerve endings,
•where APs cause the release of synaptic transmitters.
NERVE CELL (NEURON):