Blood Flow

Question 1

what is blood flow and what is it measured in?

Answer 1

The amount of blood flowing through an organ or blood vessel in a given time Measured in (mL/min)

Question 2

Why must blood flow be able to change?

Answer 2

to cater for changes in requirements

Question 3

What are the two factors that affect blood flow?

Answer 3

1) rate of output (cardiac output)

2) amount of blood (arteriole dilation)

Question 4

What is cardiac output?

Answer 4

The amount of blood leaving one of the ventricles every minute

Question 5

What factors effect cardiac output?

Answer 5

• A combination of two factors influence cardiac output
  1) Heart rate- the number of times the heart beats per minute
  2) Stroke Volume- volume of blood forced from a ventricle with each contraction

Question 6

what is the formula for cardiac output?

Answer 6

Cardiac output (mL) = stroke volume (mL) x heart rate (beats/ minute)

Question 7

How is cardiac output regulated?

Answer 7

Nerve Stimulation from the cardiovascular center

In the wall of right atrium= collection of nerve cells called the Sino atrial node (SA node)

Question 8

What is the SA node?

Answer 8

SA node acts as a ‘pacemaker’

Left on its own, gives heart constant heartbeat

Question 9

how does impulses affect SA node?

Answer 9

It begins each cardiac cycle with nerve impulses that spread over both atria= causing contraction
Nerve cells from the Cardiovascular Regulating Center carries impulses to the SA node,
Causing the heart rate to speed up/ slow down

Question 10

What allows arteries to change in diameter?

Answer 10

• The walls of arteries contain smooth muscle and elastic fibers
• When ventricles contract and push blood out of arteries= the walls of the arteries stretch to accommodate the extra blood
• When the ventricles relax, the elastic artery walls recoil
• This elastic recoil keeps the blood moving and maintains the pressure

Question 11

what is vasoconstriction?

Answer 11

a decrease in the diameter of blood vessels, restricting the flow of blood through them

Question 12

can arteries contract?

Answer 12

Not to move blood, but to reduce diameter

Question 13

what is vasodilation?

Answer 13

an increase in diameter of blood vessels, allowing for an increase in the flow of blood

Question 14

Can veins change their diameter?

Answer 14

no, don’t have muscular wall?

Question 15

how is arteriole dilation regulated?

Answer 15

by two things

1) Cardiovascular Regulating Center- controls diameter of arteries
2) Various hormones- as it causes vasoconstriction in most arteries, but in skeletal and heart muscles, it causes vasodilation, e.g. epinephrine

Question 16

why is more blood needed to be pumped when exercising?

Answer 16

to deliver more nutrients and oxygen, and removal of co2 and heat, to maintain activity of muscles

Question 17

How does the body respond to ensuring muscles have extra blood?

Answer 17

1) Nervous system and adrenalin cause constriction of blood vessels to internal organs (such as intestines), and the dilation of blood vessels to and in muscles, so
2) Blood can be directed away from organs that do not need extra and directed to the muscles

Question 18

What happens at the beginning of exercise?

Answer 18

1) Anticipatory response brought about by nervous system
2) Heart rate and stroke volume increase
3) Increase in blood flow to skeletal muscles

Question 19

What happens after continued exercise?

Answer 19

1) Muscle cells continuously require energy
2) Respiration o cells provide energy, though produce large amounts of waste= co2 and lactic acid
3) Wastes act as vasodilators= substances that produce a local widening, or dilation, of the arterioles

Question 20

Why does blood temperature raise during exercise and what does this do?

Answer 20

heat energy released in cell respiration contributing to heart rate

Question 21

What is the effect if only 30% of the bicuspid valve was working properly

Answer 21

Loose pressure
Reduces flow of oxygenated blood
Reduces flow
Reduce cardiac output/ stroke volume

Question 22

Why would a new pacemaker need to be inserted?

Answer 22

Low bp
Irregular heartbeat
Damaged

Question 23

What is the pacemaker controlled by

Answer 23

Central nervous system