Blood Flow Flashcards
what is blood flow and what is it measured in?
The amount of blood flowing through an organ or blood vessel in a given time Measured in (mL/min)
Why must blood flow be able to change?
to cater for changes in requirements
What are the two factors that affect blood flow?
1) rate of output (cardiac output)
2) amount of blood (arteriole dilation)
What is cardiac output?
The amount of blood leaving one of the ventricles every minute
What factors effect cardiac output?
- 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
what is the formula for cardiac output?
Cardiac output (mL) = stroke volume (mL) x heart rate (beats/ minute)
How is cardiac output regulated?
Nerve Stimulation from the cardiovascular center
In the wall of right atrium= collection of nerve cells called the Sino atrial node (SA node)
What is the SA node?
SA node acts as a ‘pacemaker’
Left on its own, gives heart constant heartbeat
how does impulses affect SA node?
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
What allows arteries to change in diameter?
- 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
what is vasoconstriction?
a decrease in the diameter of blood vessels, restricting the flow of blood through them
can arteries contract?
Not to move blood, but to reduce diameter
what is vasodilation?
an increase in diameter of blood vessels, allowing for an increase in the flow of blood
Can veins change their diameter?
no, don’t have muscular wall?
how is arteriole dilation regulated?
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
why is more blood needed to be pumped when exercising?
to deliver more nutrients and oxygen, and removal of co2 and heat, to maintain activity of muscles
How does the body respond to ensuring muscles have extra blood?
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
What happens at the beginning of exercise?
1) Anticipatory response brought about by nervous system
2) Heart rate and stroke volume increase
3) Increase in blood flow to skeletal muscles
What happens after continued exercise?
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
Why does blood temperature raise during exercise and what does this do?
heat energy released in cell respiration contributing to heart rate
What is the effect if only 30% of the bicuspid valve was working properly
Loose pressure
Reduces flow of oxygenated blood
Reduces flow
Reduce cardiac output/ stroke volume
Why would a new pacemaker need to be inserted?
Low bp
Irregular heartbeat
Damaged
What is the pacemaker controlled by
Central nervous system
