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.
Muscles of the iris receive _______________________ innervation, thus exhibit ____________________________________ tone.
both parasympathetic and sympathetic
both sympathetic and parasympathetic tone.
What is the innervation of the constrictor pupillae?
parasympathetic innervation (Edinger Westphal nucleus is part of the Oculomotor complex CNIII)
What is the innervation for the dilatory pupillae?
sympathetic innervation (preganglionic cells located in the lateral horn of spinal cord segments T1-T2)
What does the loss of parasympathetic innervations result in?
dilation of the pupil due to unopposed sympathetic tone
What is Horner’s syndrome?
loss of sympathetic innervation to the face.
What is the expected result in the pupil from Horner’s syndrome?
dilation???
How is urinary Bladder Control (refer to related images) innervated?
balanced sympathetic (T11-L2) and parasympathetic (S1-S2)
The balanced innervation in urinary bladder control, controls what muscle?
control of detrussor muscle and trigone (internal sphincter)
In urinary bladder control, what does the SNS bias result in?
slight relaxation of detrussor muscle and contraction of the trigone for bladder filling.
In urinary bladder control, what does the PSNS bias result in?
contraction of the detrussor muscle and relaxation of the trigone.
What is the affect of cortical control on the urinary bladder control?
it can be facilitated or inhibited
What is micturition (urination) is initiated by?
stretch receptors in the bladder wall (especially trigone area) that enter the cord and then are sent back over PSNS for contraction of detrussor muscle and relaxation of trigone (high PSNS bias).
During filling, there is high ________ bias.
SNS
What leaves the micturition reflex intact? It, however, will no longer have what?
Cord Lesions that leave the sacral levels intact
a descending cortical control.
Autonomic Dysreflexia =
complete transection of the cord at cervical or upper thoracic levels results in an increase in sympathetic outflow due to complete loss of brainstem and cortical control.
What is the result of autonomic dysreflexia?
with either somatic or visceral stimulation that reaches sympathetic regions of the cord, an increase in sympathetic firing occurs, i.e., increase in heart rate, vasoconstriction, that results in a rapid (dangerous) increase in blood pressure.
Headache also associated with this clinical scenario.
Limbic system has a powerful influence on the hypothalamus thus on the autonomic nervous system. This extensive connectional interaction is used for the production of ___________________________. For the generation of emotion, the interface between the amygdala and the ANS is “collected” in the _________________ part of cortex.
social behavior and can color perceptions
orbitofrontal
Hypothalamus – in a sense, serves as the “upper motor neurons of the ANS” - descending information from the hypothalamus, via _________________________ pathways, influence both divisions of the ANS. Lesions of these descending influences may result in ANS disturbances.
reticular formation
What do anterior and ventromedial hypothalamic regions act as?
a parasympathetic activating region
What do posterolateral and ventromedial hypothalamic regions act as?
sympathetic activating regions
What does the ventromedial hypothalamus acts on?
both SNS and PSNS components through separate nuclei
What do lesions of the ventromedial (PNS) regions result in?
vasoconstriction = hyperthermia or an increase in body core temperature and an inability to reduce sympathetic tone
What emotions is the hypothalamus involved in the motor expression of?
rage, fear, aversion
What emotions does the hypothalamus have no role in?
feelings or emotions which accompany these behaviors (rage, fear, aversion)
What are patterns of expression and behavior subject to?
to limbic system influence (where emotions arise), and, in part, to associated changes in visceral system function (ANS)
Rage as a defensive behavior; experimental activation of ________ parts of hypothalamus result in a number of defensive behaviors (hissing and extension of claws - cats) along with a number of ANS components (____________________________________________________)
medial
pupil dilation, increased heart rate and piloerection - hair standing on end
What facilitates the defensive rage behavior (including ANS components)?
(In this instance, the amygdala is helping with the emotional component of the rage behavior, while the hypothalamus is serving to activate the motor (ANS) manifestation of rage.)
Activation of the medial parts of the amygdala sending projections into the septal region and medial hypothalamus via stria terminalis
In humans humans - what will tumors; damage to temporal lobe limbic structures, or seizure foci in amygdala and/or hippocampus may result in?
rage behaviors associated with them that can be elicited by innocuous (not normally disturbing) stimuli.
