Human Phys 5.3

Question 1

What are chemoreceptors sensitive to?

Answer 1

Oxygen lack

CO2 excess

H+ ion excess

Question 2

Where are peripheral chemoreceptors located?

Answer 2

In carotid bodies near the carotid bifurcation and on the arch of the aorta

Question 3

What does activation of chemosensitive receptors result in?

Answer 3

Excitation of the vasomotor center

Question 4

When are chemoreceptors stimulated?

Answer 4

When partial oxygen falls below 60 mmHg

Question 5

What is the CNS ischemic response activated in response to?

Answer 5

Cerebral ischemia

Question 6

What does reduced cerebral blood flow cause?

Answer 6

CO2 build up which stimulates vasomotor center and increases arterial pressure

Question 7

What is one of the most powerful activators of the sympathetic vasoconstrictor system?

Answer 7

CNS ischemic response

Question 8

What does a prolonged CNS ischemia have?

Answer 8

A depressant effect on the vasomotor center

Question 9

Cushing reaction steps

Answer 9

Increased cerebrospinal fluid pressure

Compression of cerebral arteries

Decreased blood flow

Cushing reaction leads to increased BP

Blood flow is restored

Question 10

What do low pressure baroreceptors in atria and pulmonary arteries do?

Answer 10

Minimize arterial pressure changes in response to changes in blood volume

Question 11

What does increase in blood volume activate?

Answer 11

Low pressure baroreceptors which in turn lower arterial pressure

Question 12

How does activation of low pressure baroreceptors enhance Na+ and water excretion?

Answer 12

Decreasing rate of antidiuretic hormone

Increasing glomerular filtration rate

Decreasing Na+ reabsorption

Question 13

Increase in blood volume causes what?

Answer 13

Increase in atrial stretch

Increased natriuretic peptide and decreased renal sympathetic activity

Increased sodium and water excretion

Question 14

Bainbridge reflex

Answer 14

Increase in atrial pressure causes increase in HR by 75% which increases CO to push out more blood and lower pressure (15% due to mechanical stretch on sinus node)

Question 15

What does the bainbridge reflex help prevent?

Answer 15

Damming of blood in veins, atrial, and pulmonary circulation

Question 16

What is the bainbridge reflex response to high pressure receptors?

Answer 16

Decreased HR

Question 17

What is the bainbridge reflex response to low pressure receptors?

Answer 17

Increase HR

Increase CO

Increase renal perfusion

Increased Na+ and water excretion

Question 18

What do stretch receptors in the atria transmit signals to in the bainbridge reflex?

Answer 18

Medulla via vagal afferents and sympathetic efferents signals are transmitted back to increase HR and contractility

Question 19

How do intravenous infusions increase HR?

Answer 19

Through bainbridge reflex

Question 20

How does the intravenous infusions decrease HR?

Answer 20

Baroreceptors

Question 21

What do baroreceptors and chemoreceptors also stimulate?

Answer 21

Abdominal muscles

Question 22

What does abdominal muscles contracting help increase?

Answer 22

Venous return and CO

Question 23

What does inspiration lead to?

Answer 23

HR acceleration

Question 24

What does expiration lead to?

Answer 24

HR deceleration (due to activity of vagal fibers increasing)

Question 25

What does spillover from inspiratory centers stimulate?

Answer 25

Vasomotor center

Question 26

What does decreased intrathoracic pressure lead to?

Answer 26

Increased venous return

Question 27

What does relieving stretch on high pressure arterial receptors cause in the baroreceptor reflex?

Answer 27

Tachycardia

Question 28

What does stretching low pressure atrial receptors cause in the bainbridge reflex?

Answer 28

Tachycardia