4 - Autonomic Systems Flashcards
What is the function of the autonomic nervous system?What are examples of this function?
Central and peripheral portions of the NS designed to harmonize bodily functions with brain state.
BP, HR, digestion, urination, and thermoregulation.
What are the two polarities of the ANS?
Rest and digest: parasympathetic
Fight or flight: sympathetic
How do the parasympathetic and sympathetics ANS work most often? Give examples.
Most often coordinate together.
Cooling: sweating and skin dilation
Voiding: detrusor and trigone
Fainting: hypotension and bradycardia
How is the autonomic nervous system organized?
Cranial parasympathetic outflow: above T1
Pelvic parasympathetic outflow: S2-S4
Sympathetic outflow: T1-L2
In terms of autonomic function, what are two important spinal levels to consider?
Lesions above T6 result in BP problems such as orthostatic hypotension: splanchnic circulation innervation
Lesions at S1 are above are upper motor neurons involved in bladder/bowel. Lower motor neurons are S2-4.
What is the outflow for the PNS and SNS?
PNS: cranio-sacral
SNS: thoracolumbar
What is the preganglionic pharmacology of the PNS and SNS?
PNS: nicotinic cholinergic
SNS: nicotinic cholinergic
What is the postganglionic pharmacology of the PNS and SNS?
PNS: muscarinic cholinergic
SNS: Noradrenergic
What are the co-released agents in the PNS and SNS?
PNS: vasoactive intestinal peptide, calcitonin gene-related protein (CGRP)
SNS: Neuropeptide Y (NPY), neurotensin
What is the function of the PNS in a non-threatened and a threatened state?
Non-threatened: daily end-organ modulation
Threatened: allows SNS to lead
What is the function of the SNS in a non-threatened and a threatened state?
Non-threatened: coordinate under PNS lead
Threatened: coordinate emergent readiness
Describe the ganglion associated with the PNS and the SNS?
PNS: close to end-organ; not much cross-organ orchestration.
SNS: in sympathetic chain close to sp cd; extensive cross-organ coordination
What are the primary roles of the PNS and SNS?
PNS: neurons synapse on SNS neurons and provide control for PNS over SNS.
SNS: when in concert, yields to PNS; however, many areas innervated by SNS only such as vessels and sweat glands.
Describe the response speed of the PNS and SNS?
PNS: fast <1 second
SNS: slow, several seconds
What is an autonomic disorder?
Defined in adult as a condition in which the patient experiences altered autonomic function that adversely affects health.
What are the two central autonomic control centers?
Hypothalamus and PAG.
They receive input from farther up.
What does every patient that falls have?
An orthostatic BP taken on them (lying, sitting, standing).
What is orthostatic hypotension?
Form of low pressure that occurs when you sit or stand from a lying position.
Can make you feel dizzy, lightheaded, or make you faint.
What symptom is commonly absent in pts with structural autonomic disorders?
Lightheadedness.
What are characteristics of a structural ANS disorder? What are examples of structural ANS disorders?
Think hardware
-Well-defined changes in ANS structure producing disease
Exp: multiple system atrophy, diabetic autonomic neuropathy, baroreflex failure due to neck radiation.
What are characteristics of a functional ANS disorder? What are examples of funcitonal ANS disorders?
Think software
- change in ANS function produces symptoms, but is:
(1) less well-defined and
(2) a link in a pathogenic chain but not primary
Emp: postural tachy syndrome (POTs), IBS, and syncope
What is the function of the baroreflex?
Pressure sensors in the aortic arch, carotid sinus, and sinus node that serve as a way for the brain to monitor and adjust BP.
Why do we develop orthostatic intolerance?
75% of our blood volume is below our heart level, this differs from many other animals.
This makes it difficult to return blood to our heart and get blood to our brain.
What afferent input is involved in thermoregulation? What modulates the set-point control of temperature?
Afferent input: anterior hypothalamus
Setpoint control: VIP, IL-6, IL-2, PGE2
What two things are involved in thermoregulation?
Anterior hypothalamus: cooling
Posterior hypothalamus: warming
What is the ascending control of thermoregulation?
Behavior: moving to a cooler or warmer environment, putting on a sweater
What are the descending controllers of thermoregulation?
lateral horn: skin vessels, sweat glands, brown fat
Anterior horn: motor (shivering)
Brainstem: respiratory rate
Anterior pituitary: thyroid stimulation
What results from a hypothalamic lesion in the suprachiasmatic nucleus? What is the function of this space? What can cause this?
Function: regulates circadian rhythm
Lesion: causes insomnia
Can be caused by Alzheimer’s disease or shift-work
What is the function of the anterior nucleus of the hypothalamus? What results from lesions here? What mediates this?
Function: dissipates heat
Lesion: causes hyperthermia
Endogenous pyrogens such as IL-2 and PGE2 cause fever.
What is the function of the medial hypothalamus? What results from lesions here? What are examples of this?
Regulates feeding behavior (stops overeating).
Lesion causes overeating and obesity.
Prader-willi syndrome, craniopharyngioma.
What can the hypothalamus be thought of? What about the periaqueductal gray?
Hypothalamus: It’s the chief internal environment operating officer
PAG: chief external environment operating officer
What is the function of the PAG?
Implements basic behavioral mode to determine if something is safe or a threat.
Safe: sleep, wake, urination.
Threatening: determine if threat is escapable or inescapable
What is the so-called CFO and COO of the brain? What is their function?
CFO: insula, manages everything (like the dashboard on a 747)
COO: amygdala: provides urgency
What provides input to the PAG?
The hypothalamus, amygdala, the prefrontal and anterior cingulate cortices, anterior insula and orbitofrontal cortex.
What does the PAG receive info to determine? What does it get afferent from?
Whether something is safe or a threat.
Info from nociceptors and visceral afferents.
What parts of the PAG are involved in a controllable treat? What about a non-controllable threat?
Controllable: DL and L
Non-controllable threat: VL
-says you’re going to die and creates complete analgesia, drop in HR and BP, and paralysis.
What changes occur in your body if the threat is determined to be controllable?
HTN and tachy, extracranial vasodilation, and hindlimb and renal vasoconstriction.
