ANS Flashcards
What is the primary function of the autonomic nervous system (ANS)?
homeostasis
The ANS acts to maintain the internal environment within the limits compatible with life. The ANS responds to both internal and external changes and makes the approprate homeostatic adjustments. The ANS is controlled by the ___________________ and through it is coordinated with the ________, __________, and __________ systems.
hypothalamus
CNS, endocrine and immune systems.
The “final common pathway” of the ANS is a bit different than the somatic motor system in that it has:
a “two neuron chain” lower motor neuron organization
This “two neuron chain” lower motor neuron organization consists what?
A preganglionic neuron with a cell body located within the CNS and a
Postganglionic neuron with a cell body located in a peripheral ganglion.
Where do axons of preganglionic neurons synapse?
Where do axons of postganglionic neurons synapse?
on postganglionic neurons.
on ANS target tissues: smooth muscle, cardiac muscle, glands.
What are the two major divisions of the ANS?
- sympathetic (thoracolumbar)
2. parasympathetic (craniosacral)
What is the sympathetic nervous system organized with?
- preganglionic cell bodies
2. postganglionic cell bodies
Where are the preganglionic cell bodies of the sympathetic nervous system located?
in the intermediolateral cell column (lateral horn) of spinal cord levels T1-L2 (thoracolumbar)
What neurotransmitters are associated with the preganglionic cell bodies of the SNS?
acetylcholine (nicotinic)
Describe the preganglionic cell bodies of the SNS:
they are short myelinated axons, directed toward peripheral sympathetic chain ganglion
Where are the postganglionic cell bodies (paravertebral ganglion) of the SNS located?
parallel to the spinal cord along a paravertebral chain associated with the ventral roots of spinal nerves T1-L2 and also located in the cervical region and as prevertebral ganglion
Describe the postganglionic cell bodies of the SNS:
long unmyelinated axons travel as components peripheral nerves to target organs
Which are myelinated, postganglionic or preganglionic cell bodies of the CNS?
preganglionic
Which neurotransmitters are associated with the postganglionic cell bodies of the SNS?
norepinephrine
What structure receives preganglionic innervation and then is activated to release norepinephrine hormonally?
adrenal medulla
Where are the preganglionic cell bodies of the parasympathetic nervous system located?
located in nuclei associated with cranial nerves III, VII, IX, X and in the intermediolateral cell column of spinal cord levels S2-S4 (craniosacral)
Describe the preganglionic cell bodies of the PNS:
long myelinated axons directed toward peripheral ganglion
What is the neurotransmitter associated with the preganglionic PNS cell bodies?
acetylcholine (nicotinic)
Where are the postganglionic cell bodies of the PNS located?
located near the target organ or within the wall of the target organ
Describe the postganglionic cell bodies or the PNS:
short unmyelinated axons
Which neurotransmitter is associated with the postganglionic cell bodies of the PNS?
acteylcholine (muscarinic)
The preganglionic axon can synapse on more than one postganglionic cell body resulting in ______________, or several preganglionic axons can synapse on a single postganglionic cell body resulting in ________________. The sympathetic nervous system exhibits a greater degree of ________________, which accounts for ______________ effect of sympathetic activity.
divergence
convergence
divergence
mass action
As a “final common pathway” the innervation of smooth muscles, cardiac muscles and glands establishes and maintains what?
“tone”.
Smooth muscles of capillary beds are controlled by sympathetic “tone”. Capillary beds of the peripheral vascular system receive __________________ innervation. Thus, an increase or decrease in sympathetic activity changing the “tone” of precapillary sphincters results in _______________________________
no parasympathetic
changes of flow through capillary beds.
