Cardiovascular System - Regulation of Blood Flow and Arterial Pressure

Question 1

Microcirculation - capillary vessels

Answer 1

• thin-walled vessels composed of single layer of endothelial cells
• blood delivered to the capillary beds via the arterioles
• capillaries merge into venules which carry blood from tissues to veins
• site of exchange of nutrients, fluid, waste products in the tissues

Question 2

main types of capillaries (3)

Answer 2

1. continuous
2. fenestrated
3. discontinuous

Question 3

capillary exchange mechanisms (2)

Answer 3

1. diffusion
2. bulk flow of fluid
3. transcytosis
   (all passive)

Question 4

starling equation for solute flux**

Answer 4

add to formula sheet

Question 5

oncotic pressure

Answer 5

opposing force to hydrostatic pressure

Question 6

net driving force for fluid movement

Answer 6

net pressure gradient determined by the sum of the individual hydrostatic and oncotic pressures

Question 7

balance of Starling forces across capillaries in the legs and lungs

Answer 7

• legs: pressure decrease as distance from arteriolar end increases (~40-20mmHg)
• lungs: same as legs (~32-29 mmHg)

Question 8

net filtration pressure in most organs

Answer 8

drives a net fluid flow out of the capillaries

Question 9

lymphatic system’s functions (3)

Answer 9

1. preservation of circulatory volume
2. absorption of nutrients
3. defines against bacterial and viral invasion

Question 10

caliber of arteriole controls perfusion of tissue (vasoconstriction and vasodilation)

Answer 10

vasoconstriction: decreases capillary pressure
vasodilation: increases capillary pressure

Question 11

capillary pressure determined by pre- and post- capillary resistances**

Answer 11

add to formula sheet

Question 12

mechanisms that regulate blood flow (2)

Answer 12

1. intrinsic (local) control

2. extrinsic (systemic) control

Question 13

intrinsic (local) control

1. myogenic response
2. endothelial secretions
3. metabolic products
4. paracrine secretions

Answer 13

1. contractile response to stretch
2. generally dilate arterioles: NO and prostacyclin = vasodilation, endothelia = vasoconstriction
3. generally vasodilator (ie CO2)
4. histamine (increases permeability), bradykinin, prostaglandins = vasodilation
   thromboxane, serotonin = vasoconstriction

Question 14

extrinsic (systemic) control

1. neural
2. hormonal

Answer 14

1. • sympathetic NS, predominantly controls the vascular system, effects depend on receptors on the vascular smooth muscle
2. • vasopressin (ADH-antidiuretic hormone) = constricts blood vessels
   • angiotensin II = constricts blood vessels and stimulates the release of ADH and aldosterone
   • epinephrine = constricts blood vessels
   • atrial natriuretic peptid (ANP) = vasodilation (opposes the RAA system)

Question 15

what level must mean arterial pressure remain at?

Answer 15

high, constant level of 100mmHg

Question 16

Ohm’s law and hemodynamics (arterial pressure)

Answer 16

arterial pressure drives flow, but also arises from flow

Question 17

regulation of arterial pressure involves (3) distinct processes

Answer 17

1. cardiac contractility
2. vascular smooth muscle contractility
3. blood volume in the vasculature

Question 18

regulation of arterial pressure is controlled by (3)

Answer 18

1. neurogenic mechanisms (fast response)
2. hormonal mechanisms (intermediate)
3. intrinsic mechanisms (slow)

Question 19

baroreceptors (mechanoreceptors)

Answer 19

• located in carotid sinus and aortic arch

- sense blood pressure and stretch

Question 20

baroreceptor reflex

Answer 20

• regulates heart and vasculature to stability blood pressure
• receptors, sensory pathway, integration centre, motor pathway, effector