Regulation of the ANS

Question 1

What is the overall function of the ANS?

Answer 1

Integrated a variety of incoming sensory input as well as input form higher CNS centers involved in cognition and complex behavioral funcitons.

Question 2

What is the output of the ANS?

Answer 2

Coordinates Endocrine Function, Visceromotor Function, and Somatic Motor Outflow

Question 3

What is the highest level coordinator of the ANS?

Answer 3

The hypothalmus

Question 4

What is the most important brainstem structure controlling the ANS?

Answer 4

Nucleus of the Solitary Tract

Question 5

Nucleus of the Solitary Tract

Where is it located?

Answer 5

Medulla

Question 6

Nucleus of the Solitary Tract

What are its functional divisions?

Answer 6

Caudal nucleus = visceral

Rostral nucleus = gustatory

Question 7

Nucleus of the Solitary Tract

What kind of information does it receive?

Answer 7

General Visceral

Special Visceral (Taste)

Question 8

Nucleus of the Solitary Tract

Where does output project to?

Answer 8

1) Preganglionic neurons in the brainstem and spinal cord (contributes to sensory motor reflexes)
2) Autonomic centers in the reticular formation (contributing to coordination of ANS reflexes including respiration, cardiac refelxes, micturition, etc)
3) Hypothalamus (information going to higher center of ANS control)
4) Amygdala (involved in emotion)

Question 9

Reticular Formation - where is it located and how is it organized?

Answer 9

It is a diffuse and ill defined collection of nuclei that runs the length of the brainstem. These nuclei are interspersed among the more compact and named structures of the brainstem.

Certain regions within it are responsible for certian systems and functions

Question 10

Reticular Formation

What kind of information does it receive?

Answer 10

Sympathetic and Parasympathetic viscerosensory info

Question 11

Reticular Formation

Where does it project to?

Answer 11

Projects to the preganglionic neuron in the SC and the brainstem involved in the ANS reflexes.

Also projects to higher centers aka hypothalamus

Question 12

Visceral Reflexes: Cardiovascular -Baroreceptor Reflex

What is its function?

Answer 12

Serves to maintain our BP within normal ranges in response to sudden postural changes.

Question 13

Visceral Reflexes: Cardiovascular -Baroreceptor Reflex

What are the steps?

Answer 13

1) A person stands up from supine, and gravity causes a downward rush of fluids
2) As a result, baroreceptor discharge decreases, so there is decreased baroreceptor input to the solitary nucleus
3) As a result, solitary nucleus input to the reticular formation vasopressor neurons is decreased
4) Through this pathway, we have a decrease in parasympathetic input and an increase in sympathetic input.
5) This INCREASES, HR, SV, and total peripheral resistance which should bring the BP up

Question 14

Visceral Reflexes: Cardiovascular -Baroreceptor Reflex

What is Orthostatic Hypotension?

Answer 14

A severe drop in BP when a person assumes an upright position due to failure of the baroreceptor reflex.

Question 15

Visceral Reflexes: Urinary Bladder - Micturition

What systems are involved in urination control?

Answer 15

The neural control of bladder function involves the coordination of relevant autonomic, somatic motor, and cognitive faculties that inhibit or promote urination.

Question 16

Visceral Reflexes: Urinary Bladder - Micturition

What happens when the bladder is filling?

Answer 16

Low discharge of mechanoreceptors in the bladder does three things:

1) increases sympathetic outflow to the internal urethral sphincter causing contraction of the internal urethral sphincter
2) Inhibits parasympathetic outflow to the bladder wall (we want the wall relaxed)
3) Sacral somatic motor neurons are sonically active, output keeps the external urethral sphincter contracted

The result is urine STORAGE

Question 17

Visceral Reflexes: Urinary Bladder - Micturition

What happens when the bladder is full?

Answer 17

Discharge of mechanoreceptors in the bladder increases to a threshold level, resulting in:

1) Decreased sympathetic outflow to the internal urethral sphincter causing relaxation of the internal urethral sphincter
2) Increased parasympathetic outflow to the bladder wall causing the bladder wall to contract
3) Causes inhibition of the sacral somatic motor neurons to the external urethral sphincter which relaxes the external urethral sphincter

The result is BLADDER EMPTYING

Question 18

Visceral Reflexes: Autonomic dysreflexia

Answer 18

Characterized by an abrupt onset of excessively high blood pressure due to loss of supraspinal control of the sympathetic and sacral parasympathetic systems.

Face will get flush, BP sky rockets, patient may feel nauseous.

It usually begins with a noxious stimulus that is seemingly innocuous below the level of the SC injury.

The person may bot be able to feel what the stimulus is. They aren’t getting the somatosensory perception, but the firing that is occurring can lead to this condition

Usually happens in patients with SC injury about T6