Farmasevtika instituti farmakologiya va klinik farmatsiya kafedrasi

Membrane Potentials and Action Potentials in Smooth Muscle 
Membrane Potentials in Smooth Muscle. 
The quantitative voltage of the membrane potential 
of smooth muscle depends on the momentary condition of the muscle. In the normal resting state, the 
intracellular potential is usually about −50 to −60 millivolts, which is about 30 millivolts less negative 
than in skeletal muscle.
Figure 8-5 
A, 
Typical smooth muscle action potential (spike potential) elicited by an 
external stimulus. 
B, 
Repetitive spike potentials, elicited by slow rhythmical electrical waves 
thatoccur spontaneously in the smooth muscle of the intestinal 
wall. 
C, 
Action potential with a plateau, recorded from a smooth mus le fiber of the 
uterus. 
Unit II Membrane Physiology, Nerve, and Muscle 
96 
Effect of Local Tissue Factors and Hormones to Cause Smooth Muscle Contraction 
Without Action Potentials 
Probably half of all smooth muscle contraction is initiated by 
stimulatory factors acting directly on the smooth muscle contractile machinery and without action 
potentials. Two types of non-nervous and nonaction potential stimulating 
factors often involved are (1) local tissue chemical factors and (2) various hormones.
System,_Basic_Functions_of_Synapses,_and_Neurotransmitters'>14.Organization of the Nervous System, Basic Functions of Synapses, and Neurotransmitters

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he nervous system is unique in the vast complexity of thought processes and control actions it 
can perform.It receives each minute literally millions of bits of information from the different sensory 
n rves and sensory organs and then integrates all these to determine responses to be made by the body. 
System
—Sensory Receptors 
Most activities of the nervous system are initiated by sensory experiences that excite 
sensory 
receptors, 
whethervisual receptors in the eyes, auditory receptors in the ears, tactile receptors on the 
surface of the body, the brain, or memories of the experiences can be stored in the brain for minutes, 
weeks, or years and determine bodily reaction s at some future date.