Vascular pt 3

Question 1

What effect does decreasing resistance in one organ have on the MAP of the entire system?

Answer 1

A decrease in resistance means a decrease in MAP of the entire system.

MAP must be maintained, therefore it is restored by baroreflexes the elicit vasoconstriction and increased cardiac output.

Question 2

What two primary mechanisms regulate MAP?

Answer 2

Cardiovascular (baroflex): fast, short term response

Renal: slow, long term response

Question 3

Where are baroreceptors found?

What do they respond to?

Answer 3

In the aortic arch and carotid sinus.

They respond to the change in tension of the carotid artery and aortic arch b/c of changes in blood pressure.

Question 4

What is a baroreceptor reflex to an increase and decrease in blood pressure?

Answer 4

(inverse relationship)
Increase elicits a decrease in heart rate and blood pressure
Decrease elicits an increase in heart rate and blood pressure

Question 5

Baroreceptor afferents project to where? And where do they project excitatory activity to?

Answer 5

Solitary Nucleus (NTS) 
- the caudal ventrolateral medulla and the nucleus ambiguus

Question 6

What do the baroreceptors of the caudal ventrolateral medulla inhibit?

Answer 6

the rostral ventrolateral medulla (RVLM)

Question 7

What is the role of the RVLM baroreceptor pathway?

Answer 7

• Acts as a pacemaker for the basal sympathetic activity

- Projects to sympathetic preganglionic neurons in the spinal chord

Question 8

What is the role of the nucleus ambiguus baroreceptors?

Answer 8

The parasympathetic neurons in the vagus nerve (CNX) decelerate the heart rate

Question 9

What is the role of the sympathetic baroreceptor pathway?

Answer 9

Preganglionic and postganglionic neurons go to blood vessels

Question 10

Baroreception is what kind of system?

Answer 10

A negative feedback system

A homeostatic system

Question 11

What affect does an increased MAP have?

Answer 11

• Stimulation of the CVLM neurons, reducing tonic sympathetic activity in the RVLM
• Reduction of HR and MAP
• Stimulation of the parasympathetic neurons in nucleus ambiguus, decreasing HR

Question 12

What is the set operating point?

What determines the set point?

Answer 12

• Where the baroreflex is the most sensitive and produces the max response for a shift in BP
• Determined by sensitivity of RVLM neurons to baroreceptive input

Question 13

How is RVLM sensitivity to BP altered?

Answer 13

• Top down: cerebral input

- Bottom up: sensory input via brain stem centers

Question 14

What are the characteristics of the negative feedback system of baroreceptors?

Answer 14

• Only works when BP has already changed; occurs as a response
• Time delay between disturbance and homeostatic restoration; produces changes in vascular function

Question 15

What are the characteristics of the feedforward control system of baroreceptors?

Answer 15

• Signal associated with disturbance sent to RVLM to anticipate a change in BP; creates a pre-emptive compensatory response to BP
• Reduces changes in the vascular system by stabilizing responses

Question 16

What are the characteristics of CNS baroreflex regulation?

Answer 16

• Long term BP is tightly regulated

- CNS generates a vascular tone (baseline) of BP for specific behavioral or emotional contexts

Question 17

How does the RVLM maintain BP with pacemaker-like cells?

Answer 17

• Continuous activity projected to preganglionic sympathetic neurons
• Bottom up regulation (baroreceptors adjust RVLM to stabilize BP)
• Top down regulation (cerebral cortex and limbic system activity)

Question 18

What do the cerebral cortex and the limbic system affect? What are they responsible for?

Answer 18

• Anticipatory, emotional or cognitive responses to environmental stress/threats (project into the hypothalamus; paraventricular nucleus)
• Responsible for behavior- related adjustments to sympathetic tone (feedforward control of baroreflexes)

Question 19

What does the paraventricular nucleus do?

Answer 19

Regulates ANS control of BP and baroreflex sensitivity

Question 20

What do paraventricular and supraoptic nuclei do?
What does their destruction cause?
Where does the paraventricular nucleus project into?

Answer 20

• Regulate water balance; produce ADH and oxytocin
• Destruction causes diabetes insipidus
• PVN projects into autonomic nuclei of brainstem and spinal cord

Question 21

What does the anterior nucleus do?

What does its destruction result in?

Answer 21

• Thermal regulation via heat dissipation; stimulates PNS

- Destruction causes hypothermia

Question 22

What does the preoptic area contain?

What does it do?

Answer 22

• Contains sexually dimorphic nucleus.

- Regulates release of gonadotrophic hormones

Question 23

What does the suprachiasmatic nucleus do?

Answer 23

Receives input from retina, controls circadian rhythms

Question 24

What does the dorsomedial nucleus stimulation result in?

Answer 24

Obesity and savage behavior

Question 25

What does the posterior nucleus do? | What does its destruction result in?

Answer 25

- Thermal regulation; stimulation of SNS | - Destruction results in inability to thermoregulate

Question 26

What does the stimulation of the lateral nucleus do? | What about its destruction?

Answer 26

- Stimulation induces eating | - Destruction induces starving

Question 27

What does the mammillary body do?

Answer 27

- Recieves input from the hippocampal formation - Projects to anterior nucleus of thalamus - Contains hemorrhagic lesions in Wernicke's encephalopathy

Question 28

What is the ventromedial nucleus? | What does its destruction do?

Answer 28

- Satiety center | - Destruction results in obesity and savage behavior

Question 29

What does the Arcuate nucleus do? | What does it contain?

Answer 29

- Produces hypothalamic releasing factors | - Contains DOPA-ergic neurons that inhibit prolactin release

Question 30

How does the PVN nucleus regulate RVLM and baroreflex sensitivity?

Answer 30

- Specific pathways from PVN to RVLM and spinal cord preganglionics - Subgroup regulates heart, vascular system, and kidney to estabilsh BP and HR baselines of behavioral contexts

Question 31

What is the internal control of the PVN? | What is the result of hypertension in the PVN?

Answer 31

- GABA and NO inhibit RVLM pathways | - Decreased inhibition by GABA and NO permit higher sympathetic activity and BP

Question 32

How does the CNS reset the baroreflex to maintain different levels of BP? What is the affect of changing baroreceptor sensitivity to higher BP levels?

Answer 32

- PVN temporarily enhances sympathetic vasoconstriction or desensitizes baroreceptors to changes in BP - Rightward shift in equilibrium point of baroreception

Question 33

How does exercise increase BP?

Answer 33

- Decreases baroreflex sensitivity | - Anticipatory limbic and PVN during exercise resets the baroreflex equilibrium to the right

Question 34

What is transient orthostatic hypotension?

Answer 34

Sudden downward flow of blood via gravity; causes momentary lightheadedness; ANS responds with a baroreceptor reflex

Question 35

How does aging affect baroreflex capacity?

Answer 35

- Carotid artery stiffness decreases baroreflex sensitivity (reduces response magnitude) - Delayed peak cardiovascular responses to acute carotid baroreceptor loading

Question 36

What does high frequency in power spectral analysis correspond to?

Answer 36

respiratory activity - increased pulmonary circulation during O2 intake, decreased circulation during CO2 release - primarily a result of parasympathetic activity

Question 37

What does low frequency in power spectral analysis correspond to?

Answer 37

(Meyer Waves) - Both HR and BP variability - Related to feedback changes of baroreflexes

Question 38

What is sinus arrhythmia?

Answer 38

- HR increases with inspiration, decreases with expiration