Lecture 12

Question 1

Where is our extra blood stored?

Answer 1

Systemic veins - because we have more blood than we need at any given time

Question 2

a

Answer 2

a

Question 3

Blood volume and pressure in arteries?

Answer 3

High volume and low blood pressure

Question 4

What is compliance?

Answer 4

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

Question 5

How are veins able to hold such high volumes of blood?

Answer 5

Structure… Muscular tunica media in veins is thin which makes it easy to change shape and adapt in different conditions - allows compliance.

Question 6

How is the wall of arteries different to that of veins?

Answer 6

Arteries have thick rigid walls and veins have thin compliant walls.

Question 7

How is compliance meausred?

Answer 7

Volume over pressure

Question 8

How does change in pressure affect volume in arteries?

Answer 8

There is almost no change in volume when pressure increases in arteries, this indicates very low compliance

Question 9

How does change in pressure affect volume in veins?

Answer 9

When pressure is added to the vein, the volume increasing easily making a large change. This indicates good compliance

Question 10

What does it mean that veins have survival value?

Answer 10

they are able to move blood over to the arteries in emergencies

Question 11

What is venoconstriction?

Answer 11

Constriction of a vein

Question 12

What is pooling

Answer 12

Increased pressure in the leg and feet veins, in the upright position venous volume below the heart increases.

Question 13

How do alves counteract pooling?

Answer 13

By creating individual pockets of blood which allow for smooth unidirectional flow

Question 14

How does the tissue surround veins also help to prevent pooling?

Answer 14

Muscle tone - It is actively squeezing on the vein which pushes blood upwards and downwards.

Question 15

How does skeletal muscle help to prevent pooling?

Answer 15

The walls of muscle are not compliant, this supports the vein prevents it from bending out

Question 16

How does muscle contraction increase venous return to the heart?

Answer 16

Valves superior to the contracting muscle open, allowing blood to move toward the heart. As well as valves inferior to the contracting muscle are forced closed, preventing backflow of blood to capillaries

Question 17

Give an example of when skeletal muscle contraction effects venous return to the heart?

Answer 17

During exercise when skeletal muscles are used, breathing and heart rate increases.

Question 18

What is Sterlings Law of the heart?

Answer 18

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

Question 19

what is the relationship between blood volume stroke volume?

Answer 19

The more blood that is packed into the ventricles before it contracts, the stronger the stroke volume will be.

Question 20

What is the cellular mechanism of cardiac contraction?

Answer 20

Calcium levels increase
Myosin binds to actin - forms cross bridge
Myosin pulls on actin to shorten sarcomere and generate force
Every Myocyte is activated during each beat

Question 21

What other way can generate more force?

Answer 21

Stretching the walls of ventricles by increasing blood volume, stretches the cells themselves which will in turn increase stroke volume