Cardiovascular system 9 Flashcards
What are the characteristics of veins
High volume
Low pressure
What are the characteristics of arteries
Low volume
High pressure
What is compliance
How easily something distends, distorts or deforms
how bendy/stretchy
Are veins and arteries compliant
Veins are compliant - thinner walls
Arteries are not compliant - more rigid structure
What happens to veins when more blood in pumped into them
Their volume keeps increasing to accommodate for the increase in volume
What is venoconstriction
The ability for veins to transfer blood to arteries when needed
When is venoconstriction needed and how does it work
When blood pressure drops in arteries (due to cut etc.). Can occur as veins store/pool blood and this can be transferred to the arteries to make up for the lost blood
How can the ability to pool in veins be dangerous
If you stand from a laying down position gravity to push blood downwards and it will pool below your heart and decrease above
What are the two ways our veins control pooling
Valves
‘tone’ - surrounding tissue
How do valves help to control pooling
One way valves close when blood tries to move backwards. Forms individual pockets and causes a smooth column of blood
How does surrounding muscle help to control pooling
Tissue (often muscle) surrounds veins, supporting their walls - muscle is not compliant.
How does skeletal muscle affect venous return to the heart
When we tense our muscles it squeezes our veins, pushing the blood in both directions. the valves above the tension open and the ones below close. Allowing the blood to be pushed more rapidly back to the heart.
What is startling’s law of the heart
The more blood in the ventricles, the more stretched the muscle fibres, the stronger the contraction will be and the more blood pumped out. (increased SV)
Why does staling’s law work
The more you stretch the contractile fibres (actin & myosin) the larger their max contraction and therefore the larger the max force they can produce
How do we get more blood pumped during exercise
Our muscles squeeze more blood back into our heat (venous return) which increases the volume in the ventricles. This increases the possible force of contraction and the amount of blood being pumped back out to our body
