Q2-CB13/Control of Blood Pressure

Question 1

arterial blood pressure is the driving force of ________-

Answer 1

tissue perfusion

Question 2

What are the consequences of blood pressure being too low?

Answer 2

• tissues not properly perfused
• varying degrees of severity depending on the extent and duration
• poor renal perfusion leads to drop in filtration and acute kidney injury

– poor brain perfusion leads to unconsciousness and death

Question 3

What are the consequences of blood pressure being too high?

Answer 3

• pathological damage occurs in many tissues

– retinopathy (damage to the capillaries in the eye)

– nephropathy (damage to the nephrons in the kidney)

– remodelling of the cardiovascular system (both heart and vasculature)

Question 4

Blood flow is _________ to electrical current

Answer 4

analogous, comparable

Question 5

Flow varies _______ with pressure and ________ with resistance

Answer 5

proportionally, inversly

Question 6

What is mean arterial pressure?

Answer 6

the product of the volume of blood in circulation and the resistance to flow

(mean arterial pressure = cardiac output x total peripheral resistance)

Question 7

What happens to pressure across the system?

Answer 7

it drops

Question 8

Blood pressure is monitored and mediated via the _______________

Answer 8

baroreceptor reflex

Question 9

Where are the sensory affernts in the baroreceptor reflex?

Answer 9

they are the baroreceptors themselves, they are located in the walls of the aortic arch and carotid sinus

Question 10

Where are the central relays located in the baroreceptor reflex?

Answer 10

cardiavascular centers of the brain stem, medulla oblongata

Question 11

where are the effector efferents in the baroceptor reflex?

Answer 11

they are innervating the heart and blood vessels

Question 12

Question 13

What to baroreceptors sense?

Answer 13

they sense the rate of rise in pressure and the magnitude of pressure

rate = dynamic sensitivity

magnitude = static sensitivity

Question 14

What happens to baroreceptor firing rate as arterial pressure increases?

Answer 14

baroceptor firing rate increases as well

Question 15

What are the 2 classifications of baroreceptors?

Answer 15

A fibers and C fibers

Question 16

What are A fibers?

Answer 16

A fiber baroreceptors are fewer and fast conducting (large diameter, myelinated nerves)

– low threshold (30 - 90 mmHg) so activated at normal pressures

Question 17

What are C (cardiopulmonary) fibers?

Answer 17

C fiber baroreceptors are

• more abundant and slow conducting (small diameter, unmyelinated nerves)

– high threshold (70-140 mm Hg) so only ~25% activated at normal pressure

– number activated increases as pressure rises

Question 18

Where can arterial baroreceptors be found?

Answer 18

walls of aortic arch and wall of carotid sinus

Question 19

In the aortic arch, the nerve endings join up to the form the ________

Answer 19

vagus, tenth (X) cranial nerve

Question 20

In the carotid sinus, nerve endings join together to form the _________

Answer 20

glossopharyngeal, ninth (IX) cranial nerve

Question 21

both the cranial nerves involved in the baroreceptor reflex (vagus and glossopharyngeal) travel to where?

Answer 21

the brainstem

Question 22

what info do the cranial nerves involved in the baroreceptor reflex carry to the brainstem?

Answer 22

the stretch they sense in the arteries

Question 23

where do the vagus and glossopharyngeal nerves synpase at?

Answer 23

the nucleus tractus solitarius in the medulla oblongata of the brainstem

Question 24

after the info travels to the nucleus tractus solitarius, where does it go?

Answer 24

to the cardiovascular centers

Question 25

What are the cardiovascular centers responsible for?

Answer 25

they are responsible for autonomic control of the cardiac and vascular function

Question 26

how do cardiovascular centers control cardiac and vascular function?

Answer 26

the coordinate the sympathetic and parasympathetic branches of the ANS

Question 27

What are the 2 cardiovascular control centers?

Answer 27

the vasomotor control center and the cardiac control center

Question 28

how does the vasomotor control center work?

Answer 28

it controls the diameter of blood vessels by stimulating sympathetic nerve fibers to cause vasocontriction

Question 29

What are the two divisions of the cardiac control center?

Answer 29

cardiac accelerator (inc. heart rate and cardiac contractility) through the sympathetic outflow tract and cardiac decelerator (dec. heart rate and cardiac contractility) through parasympathetic outflow tract

Question 30

What happens regarding the baroreceptor reflex when blood pressure increases?

Answer 30

When blood pulses through the carotid sinus and aortic arch, the arterial walls get stretched out. in response, baroreceptors fire more impulses to cardiovascular centers via the cranial IX and X nerves.

Since blood pressure has increased, the frequency of nerve impulses has increased as well.

to bring the pressure back down to normal, cardiovascular centers inhibit sympathetic NS and stimulate parasympathetic NS.

(vasomotor center decreases vasocontrictive effect of sympathetic NS.)

arterioles dilate, decreasing total peripheral arterial resistance (TPR). veins also decrease constriction allowing blood to pool in them rather than returning to the heart.

decreased venous return means less preload (less diastolic filling of the heart). This also decreases cardiac output.

cardiac accelerator is inhibited and cardiac decelerator is activated.

Question 31

What happens regarding the baroreceptor reflex when blood pressure decreases?

Answer 31

the decreased pressure causes the walls in the aortic arch and carotid sinus to become less stretched, and the baroreceptors start firing less frequently.

The glossopharyngeal and vagus nerve carry that decreased signal to the cardiovascular centers of the brainstem.

To bring the pressure back up to normal, these centers stimulate the sympathetic and inhibit the parasympathetic NS.

Specifically, the vasomotor center increases the vasoconstrictive effect of the sympathetic NS. The arterioles narrow, increasing total peripheral arterial resistance. Veins are constricted which returns more blood to the heart, rather than allowing it to pool.

Increased venous return means increased preload which means increased cardiac output.

also, the cardiac accelerator center is stimulated, increasing the sympathetic effect on the heart, increasing the heart rate and contractility. While the cardiac decelerator center is deactivated, reducing the parasympathetic effects on the heart, which again speeds up the heart rate.

Question 32

What are the other types of baroreceptors?

Answer 32

cardiopulmonary baroreceptors

Question 33

Where are cardiopulmonary baroreceptors found?

Answer 33

rt atrium and ventricle, pulmonary arteries and veins

Question 34

What are chemoreceptors and where are they found?

Answer 34

they can induce changes in blood pressure and they are found in carotid bodies