Autonomic Nervous System 2

Question 1

interaction of sympathetic and parasympathetic NS

Answer 1

Interaction of sympathetic and parasympathetic systems (often with somatic input) is common if not the norm

Question 2

Storage phase - Urinary bladder

Answer 2

Storage Phase:
Internal urethral sphincter remains tense and the detrusor
muscle (smooth muscle wall of the bladder) is relaxed by
sympathetic nerves (*)

Question 3

Voiding or Urination Phase:

Answer 3

Voiding or Urination Phase:
Sensory information from the distension of the bladder
(not shown) is transferred to the brainstem (pontine
micturition centre) causing reflex activation of
sacral parasympathetic preganglionic neurons (*)
leading to contraction of the detrusor muscle
AND
descending input to Onuf’s Nucleus in the ventral horn of the
sacral spinal cord and, via the somatic pudendal nerve, relaxation
of the external urethral sphincter and urination

Question 4

Coordinated control of bodily functions by sympathetic and parasympathetic pathways
Male sexual function - parasympathetic NS

Answer 4

parasympathetic input relaxes / vasodilates blood vessels in the corpora cavernosa of the penis leading to erection

Question 5

Role of Sympathetic NS in Male sexual function

Answer 5

sympathetic activation causes contraction of the epididymis expulsion of sperm into the vas deferens
in combination with recruitment of the somatic system which causes contraction of muscles in the penis, sympathetic input is responsible for ejaculation

Question 6

Two ways of how symp and parasymp NS input

Answer 6

Mixture of sympathetic and parasympathetic inputs to common ganglia different post ganglionic neuron
OR
even mixtures of sympathetic and parasympathetic inputs to the same ganglionic neuron - a coalescence of sympathetic and parasympathetic

Question 7

The ANS is a loop with……

Answer 7

The ANS is a loop with output (motor) and feedback (sensory) pathways as well as controller (descending) input

Question 8

Higher brain centers in ANS loop

Answer 8

inputs from higher brain centres the impact on these loops of autonomic function, and they arise from higher areas of the cerebral cortex or the limbic system

Question 9

Autonomic controllers in ANS loop

Answer 9

There are autonomic nervous system brainstem controllers that will impinge on these preganglionic neurons that are present in the, in the middle or the spinal cord and these autonomic controllers are present in brainstem but also in hypothalamus

Question 10

Sensory reflex

Answer 10

there is a reflex or sensory reflex, and all these different levels where information sensory information is derived from these target tissues and fit back into different levels of the autonomic nervous system to integrate function in some sort of homeostatic or feedback loop

Question 11

Diet induced thermogenesis – post prandial thermogenesis and the control of body weight

Answer 11

Diet induced thermogenesis postprandial thermogenesis and the control of body weight.
the stimulation of food or nutrients that are detected in specialized sites in the brain in the hypothalamus and then information is transferred via the sympathetic nervous system to specialized tissues and peripheral brown adipose tissue, in response to food intake and a response to increase caloric intake.
There is activation of these specialized brown fat adipocytes.
There are a number of intracellular processes, which essentially dis-regulate the normal production of ATP, you’ll appreciate .your states that ATP was responsible for the generation of energy for cellular work, but in this case there is an uncoupling or dysregulation of that process.
So instead of producing ATP, there is the production of heat. And so adipose tissue brown adipose tissue burns energy, rather than its counterpart of white adipose tissue, which is responsible for storing energy so is not it simply that is the basis of postprandial thermogenesis or burning of energy.

Question 12

Role of bioreceptor reflex

Answer 12

• The baroreceptor reflex is one of the body’s homeostatic mechanisms that helps to maintain blood pressure at nearly constant levels
• The baroreceptor reflex provides a rapid negative feedback loop in which an elevated blood pressure reflexively causes the heart rate to decrease and also causes blood pressure to decrease conversely
• Decreased blood pressure decreases baroreflex activation and causes heart rate to increase to restore blood pressure levels.

Question 13

Heart rate is controlled by

Answer 13

Sympathetic and parasympathetic

Question 14

Force of contraction is controlled by

Answer 14

Sympathetic

Question 15

Contraction of Blood vessels

Answer 15

Sympathetic

Question 16

Dilation of Blood vessels

Answer 16

Parasympathetic

Question 17

Parasympathetic effect on heart rate

Answer 17

TheParasympathetic pathway, acting via the Vagus (Xth Cranial) Nerve, slows down theheart rate

Question 18

Sympathetic NS effect on heart rate + force of cardiac muscle contraction

Answer 18

TheSympathetic pathwayincreasesheart rateand the rate of relaxation of heart muscle (i.e., faster contraction and faster relaxation)
Additionally, theSympathetic pathwayincreases theforce of cardiac muscle contraction

Question 19

Parasympathetic effect on cardiac muscle contraction

Answer 19

TheParasympathetic pathwayhas no effect onforce of contractionof the ventricles (the lower, larger chambers of the heart from which blood is ejected to the lungs and body) but has relatively strong effects on force of contraction of the atria (the upper, smaller chambers of the heart which receive blood from the lungs and body, and move it to the ventricles).

Question 20

Where are the receptors for baroreceptor reflex is located at ?

Answer 20

receptors to both blood pressure and blood chemistry are present in the carotid sinus and aortic arch

Question 21

Where the information from the receptors is relayed at ?

Answer 21

information from these receptors is then relayed via the IX and X cranial nerves to the nucleus tractus solitarius (NTS), the major recipient site in the medulla for sensory input from peripheral organs and tissues

Information is then relayed via the CVLM (“depressor centre”) to the RVLM (“Pressor centre”), then to SPNs in the thoracolumbar spinal cord

Information is also relayed from the NTS to parasympathetic preganglionic neurons in the nucleus ambiguous and dorsal motor nucleus of the vagus (DMN-X

Question 22

Response to decreased blood pressure

Answer 22

baroreceptor firing decreases which cause the
- Cardiac inhibitor center activity decreases
- Cardiac accelerator center activity increases
- vasomotor center activity increases
which results in
- increased cardiac output
- increased vasoconstriction
which
increase the blood pressure
which
restores homeostasis

Question 23

Response to increased blood pressure

Answer 23

Baroreceptor firing increases which cause the
- Cardiac inhibitor activity to increase
- Cardiac accelerator activity to decrease
- vasomotor center activity to decrease
which results in
- decreased cardiac output and vasodilation to increase which
decrease the blood pressure and restore homeostasis

Question 24

Do higher control center play role in baroreceptor reflex

Answer 24

Autonomic loop reflexes with input from “higher brain” centres -baroreceptor reflex (maintain homeostatic control of blood pressure
paraventricular nucleus and lateral hypothalamus

Question 25

Opposing actions of Sympathetic and Parasympathetic Systems

Answer 25

• Thus a decrease in sympathetic activity and an increase in parasympathetic activity will lead to:
• a decrease in heart rate AND
• a reduction in the force of contraction of the heart both of which, together with the effects on peripheral blood vessels exerted by sympatheticpathways, will work to reduce BP