Heart Flashcards
Give safety precautions that should be followed when dissecting a heart
(5)
Use a sharp scalpel
Wash hands
Wear gloves
Disinfect equipment
Cut away from self/others
Explain how the left atrioventicular valve maintains an unidirectional flow of blood
Pressure in left atrium higher than in left ventricle causing valve to open
When pressure in left ventricle higher than in left atrium valve is closed
Describe the role of the nervous system in an increase in heart rate whilst exercising using chemoreceptors
Chemoreceptors detect rise in CO2
Send impulses to the medulla and the SAN
The impulses are sent by the Sympathetic nervous system
How do humans control heart rate
A wave of excitation spreads out from the SA node over both atria causing them to contract
The wave reaches the AV node
The wave is then conducted down the septum to the apex of the ventricle via the bundle of HIs
And then via the Purkynje fibres
The apex then contracts
Why is there a delay when the heart wave passes through the AVN
Allows time for the atria to pump all its blood into the ventricles
Describe how baroceptors bring out a response to an increase in blood pressure
An increase in blood pressure is detected by baroreceptors in the wall or aorta
Increased number of electrical impulses to medulla oblongta via the parasympathetic nervous system
Impulse sent to SA node which sends impulse to cardiac muscles
Decrease heart rate to decrease blood flow
Name two types of nerves that connect the brain to the SA node
Parasympathetic
Sympathetic
What part of the brain does the para/sympathetic nerves originate
oblongata
Why do we need two seperate nerve connections
One to increase HR
One to decrease HR
Describe features of the Parasympathetic nervous system
Inhibits effectors
Controls actions under resting conditions
Slows down activity
Describe features of the sympathetic nervous system
Stimulates effectors
Controls conditions under stress
What does the sympathetic nerve release
Noradrenaline
What does the parasympathetic nerve release
Acetylcholine
Describe regulation of the heart via the sympathetic nervous system
increases heart rate
by increasing output frequency of SA node
increase blood flow out of cardiac output
Describe regulation of the heart via the parasympathetic nervous system
Release acetylcholine in order to decrease HR
this increase frequency of the AV node
this increase delay at impulse passage
Decrease blood flow out of heart
