Integration of Cardiovascular mechanisms

Question 1

What is the heart?

Answer 1

A pump

Question 2

What are the arteries?

Answer 2

passageways of blood from the heart to tissues

Question 3

What are the arterioles?

Answer 3

main site of systemic vascular resistance

Question 4

What are the capillaries?

Answer 4

site of exchange of gas, water and nutrients between blood and tissues

Question 5

What are veins?

Answer 5

capitance vessels - contain most of rhe blood volume during rest

Question 6

What controls systemic vascular resistance?

Answer 6

smooth muscle cells (through changes in the radius of arterioles)

Question 7

Resistance to blood flow is increased by??

Answer 7

1. smaller radius of blood vessel
2. higher blood viscosity
3. longer blood vessels

Question 8

What comprises the Extrinsic control of SVR?

Answer 8

Nerves - baroreceptor reflex

Hormones - adrenaline

Question 9

How does the baroreceptor reflex control SVR?

Answer 9

vasomotor tone is caused by tonic discharge of sympathetic nerves.
higher sympathetic discharge = lower vasomotor tone = vasoconstriction
and reverse

Question 10

How does adrenaline control SVR?

Answer 10

acts on alpha receptors and causes vasoconstriction
acts on beta receptors and causes vasodilation
angiotensin 2 = vasoconstriction
antiduiretic hormone = vasoconstriction

Question 11

What comprises the Intrinsic control of SVR?

Answer 11

Chemical factors - local metabolic changes and locak humoral agents
Physical factors - temperature, sheer stress, myogenic responses to stretch

Question 12

How do local metabolic changes (chemical factors) control SVR?

Answer 12

Cause vasodilation & metabolic hyperaemia:
decreased PO2, inrceased PCO2, increased [H+}, increased extracellular, increased osmolarity of ECF and adenosine release
Opposite caused vasoconstriction

Question 13

Can intrinsic mechanisms override extrinsic mechanisms?

Answer 13

YES

Question 14

How do local humoral agents (chemical factors) control SVR?

Answer 14

Chemicals released in response to tissue injury or inflammation.
Causing vasodilation: histamine, bradykinin, nitric oxide
Causing vasoconstriction: serotonin, leukotrines, thromboxane A, endothelia

Question 15

How do physical factors control SVR?

Answer 15

Temperature: hot = vasodilation cold = vasoconstriction
Sheer stress: dilation of arterioles causes sheer stress n arterioles upstream whcih causes them to dilate and increase blood flow
Myogenic response to stretch:
increase MAP = resistance vessels constrict to limit flow
decrease MAP = resistance vessels dilate to increase flow

Question 16

What factors increase venous return?

Answer 16

1. increased blood volume

2. exercise

Question 17

How does the skeletal muscle pump work to increase venous return?

Answer 17

• large veins in limbs lie between skeletal muscles so contraction of the muscle aids venous return
• one way valves allow blood to only move forward to the heart

Question 18

What are the consequences of increased VENOmotor tone?

Answer 18

increased venous return
increased stroke volume
increased MAP

Question 19

What are the consequences of increased VASOmotor tone?

Answer 19

increased systemic vascular resistance

increased MAP

Question 20

What is the acute CVS response to exercise?

Answer 20

1. increased sympathetic activity
2. increased heart rate and stroke volume
3. increased cardiac output