Lecutre 12- Venous Blood Flow And The Heart

Question 1

Almost 2/3rds of blood in the body at any one time is found where?

Answer 1

Venous system

Question 2

The great change in pressure between the veins and arteries is needed to…

Answer 2

Provide a floe

Question 3

Veins vs arteries high vs low pressure

Answer 3

Veins:
- high volume
- low pressure

Arteries
- low volume
- high pressure

Question 4

What is compliance

Answer 4

• the extent to which a vessel allows deformation in response to an applied force

Question 5

Vein vs artery - compliance

Answer 5

Artery:
- rigid
- thick wall - thick tunica layer

Vein
- thin wall
- compliment T

Question 6

Equation for compliance

Answer 6

^V/^P

• how much does it descend or expand when pressure increases

Question 7

Venous vs arterial compliance

Answer 7

Question 8

What does the graph look like if its a large change in pressure comnpared to a large change in volume

Answer 8

Question 9

What happens when arterial puncture

Answer 9

• loss of arterial blood
• life-threatening fall in arterial pressure

Question 10

Response to arterial puncter and loss of arterial blood

Answer 10

• venocontriction
• pushes blood into the atrial system from the distensible veins and lack of tunica media
• blood transfusion from venous to arterial system
• if blood in arteries isn’t restored - volume decreases and then so does mean arterial pressure

Question 11

What high compliance in veins results in:

Answer 11

• venous volume is larger then arterial volume
• while supine (laying down), venous evaluate is uniform form head to toe
• in the upright position, venous volume below the heart increases; whereas venous volume above the heart decreases
• extream venous pooling the the legs and feet

Question 12

How venous valine counteract venous pooling

Answer 12

Question 13

How tone of surrounding tissue also counteracts venous pooling

Answer 13

• particularly in the case of skeletal muscle, because it can alter its tensile state
• resting muscle tone varies between individuals
• muscle tone acts to stiffen the veins - makes them less compliant and prone to pooling
• some preppie prone to fainting have low muscke tine and excessive venous pooling

Question 14

How skeletal muscle contractions increase venous return to the heart

Answer 14

Question 15

How skeletal muscle acts as a pump to affect venous return to the heart

Answer 15

Muscle contractions increase venous blood flow

Question 16

Starlings law of the heart:

Answer 16

The more stretched muscle fibres are before contraction, the stronger the contraction will be

Question 17

Cellular mechanism of cardiac control

Answer 17

• Ca2+ levels go up, and more Ca2+ is released from the sarcoplasmic reticulum (SR)
• Myosin binds to actin to form cross-bridges.
• Myosin pulls on actin to shorten the sarcomere and generate force
• Every myocyte activated during each heart beat……

Question 18

Increasing venous return means…

Answer 18

Increased stroke volume

Question 19

What are veins?

Answer 19

Thin-walled vessels that have high compliance compared to arteries

Question 20

Blood can pool in veins, what mechanisms counter this?

Answer 20

• venous valves
• surrounding tissue tone

Question 21

Starling Lae of the heart tells us that the _____ the __________ stretch prior to ________, the ________ a ______ and greater _____ ______ we will have

Answer 21

Starlings law of the heart tells us that the mire the walls of the heart stretch prior to contraction, the stronger a contraction and greater stroke volume we will have

Question 22

Venous return directly effects

Answer 22

The stroke volume and performance of the heart