Anatomy

1 4. The Autonomic Nervous System I. Introduction compare of the physical and involuntary flighty formations The involuntary nervous organisation ( involuntary nervous system) is involved in maintaining basic homeostatic functions. The autonomic nervous system carries motor commands to the effectors of the cardiovascular, respiratory, digestive, urinary, and reproductive systems. In so doing, it helps maintain tide rip pressure, water and salt balance, dissolved bollocks concentration, etc. The autonomic nervous system carries commands to smooth go acrosss, glands, and the heart. These effectors are innervated by visceral motor neurons (recall that in straitened circumstances(p) muscles are innervated by embodied motor neurons). In the somatic nervous system, motor neuron bodies lift in the profound nervous system and their axons have a bun in the oven all the way to their effectors. In contrast, the autonomic nervous system makes mapping of pairs of mot or neurons. The body of the first motor neuron lies in the CNS, and the body of the second motor neuron lies in an autonomic ganglion (e.g., the sympathetic trunk ganglia). Visceral motor neurons that originate in the CNS are called preganglionic neurons. Axons of preganglionic neurons, which are called preganglionic fibers, synapse with ganglionic neurons in the autonomic ganglia. Axons of the ganglionic neurons, which are called postganglionic fibers, drop dead to effectors.

Preganglionic fibers are turn off and lightly myelinated, and postganglionic fibers are mainly thinner and unmyelinated. How do the conduction velocities of these fibers compa! re with conduction velocities of somatic motor neuron fibers? All somatic motor neurons play out the neurotransmitter acetylcholine (ACh) at their neuromuscular junctions. ACh is always excitatory at the penurious muscle neuromuscular junction. All preganglionic fibers of the autonomic nervous system release ACh. The effect of ACh on the ganglionic neuron is always excitatory. Postganglionic fibers of the parasympathetic division of the ANS also release ACh, but it may be either stimulatory or inhibitory. This...If you want to get a full essay, vow it on our website: OrderCustomPaper.com

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