Topic 5 - Circulation Flashcards
What stops the blood back flowing in veins?
Valves at intervals which shut to stop back flow.
Muscles contracting which press against the veins force blood from one valve to another
Which has a thicker wall and why, arteries or veins?
Arteries because they have to withstand higher amounts of pressure when the Heart pumps
What is elastic recoil of arteries?
Arteries are elastic so when blood is pumped once it keeps a reserve until the next pump
What is the name given to the valve found between the left ventricle and left atrium?
Bicuspid valve
Where is the tricuspid valve found?
Inbetween the right atrium and the right ventricle
What are the semilunar valves?
Inbetween the left ventricle and aorta and the right ventricle and pulmonary artery
What does myogenic mean and what’s an example?
Originating from the muscle itself rather than the nervous system
E.g. The hearts rhythm originates from itself at 50bpm
What is sino atrial node?
In the right atrium wall there is the sino atrial node. The cells of SAN depolarise to the point where a wave of excitation similar to a nerve impulse spreads rapidly across the atria causing it to contract (atrial systole)
Why can the SAN impulses not reach the ventricles?
Because inbetween the Atria and ventricles there’s connective tissue therefore the SAN has to active the atrio ventricular node (AVN)
What ensures that blood flows in the right direction from the ventricle to the atria?
The AVN is connected to bundle of his which is connected to purknye tissue to the base of the ventricles. The purknye tissue carries impulses 5 x faster than surrounding muscles making sure the base contracts first in ventricular systole
What is the bundle of his?
Specially modified muscle fibres
