Lecture 7 - Cardiovascular Pt 2

Question 1

What is the Major function of the vascular system?

Answer 1

Maintain homeostatic bp and distribute oxygen and nutrient-rich blood flow to the tissue.

Question 2

What are endothelial cells?

Answer 2

Innermost lining of vessels and heart
highly permeable to allow for nutrient/gas exchange
secretes paracrine factors that cause dilation/constriction
Evoke new capillary growth(angiogenesis)

Question 3

Structure features of Large arteries

Answer 3

• large diameter
• very little smooth muscle
• elastic properties (high compliance) contribute to continuous downstream blood flow

Question 4

Structure of arterioles

Answer 4

Smaller diameter than large arteries
a high proportion of smooth muscle, low proportion of elastic tissue
high resistance to flow
main site for flow regulation(dilation/constriction)

Question 5

Structure of Venules and Veins

Answer 5

Highly elastic
low/no smooth muscle
Do not contribute to blood flow regulation
Represent a pooling site for blood

Question 6

Structure of capillaries

Answer 6

Single endothelial layer to promote gas/fluid/nutrient exchange

Question 7

What is arterial Blood pressure?

Answer 7

Force of blood on the walls of blood vessels

Question 8

What is Systolic Pressure?

Answer 8

Maximal arterial pressure reached during peak ventricular ejection (~120mmHg)

Question 9

What is Diastolic Pressure?

Answer 9

Minimal arterial pressure reached during peak ventricular ejection

Question 10

What is Pulse Pressure?

Answer 10

magnitude of difference between SBP and DBP

Question 11

What is Mean Arterial Pressure? What is the equation?

Answer 11

Average pressure throughout the cardiac cycle (diastole is longer) (~90mmHg)
MAP = DBP +1/3(SBP - DBP)

Question 12

What is the major function of Large Arteries?

Answer 12

Low resistance tubes conducting blood from heart to systemic vasculature
- act as a pressure reservoir to maintain blood flow

Question 13

How are Large Arteries a pressure reservoirs?

Answer 13

• Highly elastic/highly compliant
• expands to accommodate stroke volume
• during diastole, the aorta recoils to drive blood forward throughout arteries
• prevents BP from falling to 0 during diastole; ensures continuous flow to capillaries

Question 14

What is vascular compliance?

Answer 14

Rigid large arteries will not store blood during diastole producing intermittent capillary flow

Question 15

What are the 2 major factors that affect the radius of arterioles?

Answer 15

Local Mechanisms (active hyperemia, flow regulation)
Extrinsic Mechanisms (sympathetic nerve)

Question 16

What is active hyperemia?

Answer 16

Vasodilation causes increase blood flow in muscle during contraction

Question 17

What are the mechanisms of Active Hyperemia?

Answer 17

Decreased O2(consumed for ATP production)
Increased CO2 (byproduct)
Increased H+(from lactic acid)
Increased adenosine (ATP breakdown)
Increased K+ from action potential activity
Nitric Oxide release from endothelium

Question 18

How do sympathetic neurons regulate arteriole radius?

Answer 18

Receive stimuli from sympathetic postganglionic neurons that release norepinephrine
Norepinephrine binds to alpha-adrenergic receptors to cause vasoconstriction
more sympathetic nerve activity = more vasoconstriction

Question 19

What influences capillary blood flow?

Answer 19

Blood flow is influenced by the radius of the arterioles.
capillary blood flow is slow to maximize the time for exchanging
blood flow velocity is dependent on cross-sectional area in capillaries

Question 20

What are the three main regulators of venous pressure

Answer 20

1. Sympathetic Neural veno-constriction
2. Skeletal Muscle Pump
3. Respiratory Pump

Question 21

What is the sympathetic neural veno-constriction regulator do for venous pressure?

Answer 21

Sympathetic nerves also innervate venules to cause constriction
Decreasing radius of veins increases pressure
increasing pressure gradient between peripheral and central veins drives blood back to heart

Question 22

What is the skeletal muscle pump?

Answer 22

Skeletal muscle contraction compresses veins which increases venous pressure, forcing blood back to the heart

Question 23

What is the respiratory Pump? Does inspiration or expiration drive blood back to the heart?

Answer 23

Contraction of the diaphragm muscle changes pressures in the chest to alter venous blood flow
Inspiration drives blood back to heart

Question 24

What is the equation for mean arterial pressure

Answer 24

MAP = cardiac output x Total peripheral resistance

Question 25

What is the impact of TPR on MAP

Answer 25

A change in TPR is achieved mainly by changing radius of arterioles
TPR affects MAP by altering the volume of blood in the arteries

Question 26

What is the arterial baroreceptor reflex?

Answer 26

represents a key negative feedback reflex for regulating MAP via altering cardiac output and total peripheral.
MAP dropping = increase cardiac output
MAP rising = decrease cardiac output

Question 27

What are the different organizations of the Baroreflex?

Answer 27

Afferent pathway - afferent nerves relay info via action potential from baroreceptors to areas in the brainstem and brain
Integrating Centre - medullary cardiovascular centre neurons determine the resting optimal BP and detects deviations
Efferent pathway - parasympathetic neurons and sympathetic neurons
Effectors - Heart, arterioles, veins

Question 28

When does Baroreceptors fire more? Systole or diastole?

Answer 28

Fires more during systole