Cardiovascular Control

Question 1

How is blood flow regulated?

Answer 1

It is regulated so that the minimum amount of blood required to meet metabolic demands is delivered to each tissue

Question 2

Why doesn’t the heart deliver excess blood to each tissue so there is a reserve?

Answer 2

CO would increase dramatically and thus the work of the heart would be increased

Question 3

What determines the amount of blood a tissue receives?

Answer 3

It depends on the tissue’s metabolic activity

Question 4

What regulates tissue blood flow?

Answer 4

Resistance regulates tissue blood flow

Question 5

What are the two local mechanisms to control blood flow?

Answer 5

Myogenic

Metabolic

Question 6

What is the mechanism of myogenic local control of blood flow?

Answer 6

The smooth muscle in the vessels sense a stretch that activates Ca channel opening causing a depolarization and contraction of the smooth muscle (can be overridden by metabolic response)

Question 7

What type of vessel typically exhibits the Myogenic local response?

Answer 7

Arterioles has the largest amount of smooth muscle in comparison to other vessels in the body

Question 8

What are the two metabolic mechanisms that control local blood flow?

Answer 8

O2 Lack theory

Vasodilator Theory

Question 9

What is the difference between the two metabolic mechanisms that control local blood flow?

Answer 9

The vasodilatory theory senses excess waste products and increases blood flow accordingly and the O2 lack theory senses a deficit of nutrients and oxygen and increases blood flow accordingly

Question 10

What vasodilating products arise from metabolism?

Answer 10

Adenosine
CO2
H+
K+
Histamine

Question 11

Intermittent contraction of pre capillary sphincters and metarterioles

Answer 11

Vasomotion

Question 12

What two organ systems autoregulation overrides a neural response?

Answer 12

Brain

Kidneys

Question 13

In what three scenarios could angiogenesis occur?

Answer 13

Exercise
Disease
Altitude changes

Question 14

What cytokine stimulates angiogenesis?

Answer 14

VEGF

Question 15

What two factors make up Humoral control of blood flow?

Answer 15

Hormones

Ions

Question 16

What ions are released by the skeletal muscle during high metabolic activity thus increasing O2 to the tissues?

Answer 16

K+
H+
Mg
All of these are vasodilator which increases the blood flow to tissues in need, an appropriate homeostatic response

Question 17

What three factors can neural control of blood flow affect?

Answer 17

Distribution of blood flow
Heart pumping function
TPR

Question 18

What is the neural pathway to effect the control of blood flow?

Answer 18

Sensory afferent to NTS, the NTS talks to the vasomotor cortex which sends an efferent signal back to the effector (think autonomic nervous system)

Question 19

What part of the autonomic nervous system innervates the vasculature?

Answer 19

Sympathetic nervous system

Question 20

What three reflex mechanisms are used to maintain arterial pressures?

Answer 20

Baroreceptors
Chemoreceptors
CNS ischemic response

Question 21

What four areas make up the vasomotor center?

Answer 21

Vasoconstrictor area
Vasodilator area
Lateral VMC (cardiac function)
NTS

Question 22

What carries afferent information to the NTS from the baroreceptors and chemoreceptors?

Answer 22

Vagus nerve

Glossopharyngeal nerve

Question 23

How can emotional stress trigger an increase in blood pressure and heart rate?

Answer 23

The vasomotor center can be inhibited or excited by areas in the brain such as the hypothalamus, cerebral cortex, motor cortex and hippocampus (limbic system)

Question 24

What type of fibers carry an inhibitory signal to the heart and what types of fibers carry an acceleratory signal to the heart?

Answer 24

Inhibit: Vagus nerve
Accelerate: sympathetic nerve fibers

Question 25

Why can't the PSNS effect inotropy of the heart?

Answer 25

The PSNS only innervates the nodal regions of the heart, there is no muscle innervation, only the SNS innervates both the nodes and the muscle of the heart

Question 26

What part of the vasculature does the SNS not innervate?

Answer 26

The capillaries, metarterioles and precapillary sphincters

Question 27

In what way does the PSNS indirectly affect circulation?

Answer 27

PSNS has vagal input on the heart, profound bradycardia can significantly impact circulation

Question 28

What is the most rapid mechanism for blood pressure control?

Answer 28

The autonomic nervous system responses

Question 29

If n increase in pressure is sensed by the baroreceptor, what is the response?

Answer 29

Baroreceptor sensed an increase in pressure, sends more afferent messages as pressure increases to NTS via cranial nerves X and IX, the NTS fires to the vasodilator center which then sends an inhibitory signal to the vasoconstrictor center of the vasomotor center. By inhibiting the vasoconstrictor system the SNS backs off and the vessels are able to dilate and accommodate to the high pressures

Question 30

Why don't baroreceptors contribute to long term blood pressure control?

Answer 30

The baroreceptors reset after a small time period

Question 31

What is the neural mechanism for increasing the heart rate after sensing an increase in volume by the atrial receptors?

Answer 31

Increased firing to the NTS by mechanoreceptors in the atria and large veins via cranial nerves, NTS communicates with the cardioaccelerator center which increase SNS

Question 32

What is the intrinsic mechanism for increasing the heart rate after sensing an increase in volume by the atrial receptors?

Answer 32

A stretched SA node influences pacemaker cells of the heart (ion channel conductance) by increasing the action potential frequency

Question 33

How is ANP stimulated when there is an increase in circulating volume?

Answer 33

Stretch of the cardiomyocytes release stored granules of ANP which circulate to the kidneys and promote the loss of sodium in the urine