Normal heart beat
- Created by: katie
- Created on: 23-03-13 15:01
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- Normal heart beat
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Heart muscle is myogenic
- It can contract without any nerve stimulation.
-
The stimulus to contract originates in the sinoatrial node (SAN)
- Which controls the rate of beating / acts as pacemaker
- It is situated in the wall of the right auricle / atrium
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Electrical impulse from the SAN causes the two auricles / atria to
contract
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Thin layer of connective tissue prevents the stimulus spreading to the
ventricles
-
At the bottom of the wall separating the two auricles / atria is the
atrioventricular node AVN
-
This delays the impulse (about 0.1 sec) before passing it on to the
ventricles
-
The impulse is sent to the tip/apex of the ventricles
-
Along bundle branches (Bundle of His)
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And is conveyed upwards along the branching Purkinje fibres
- Causing a wave of ventricular contraction starting from the lowermost part of the ventricle
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And is conveyed upwards along the branching Purkinje fibres
-
Along bundle branches (Bundle of His)
-
The impulse is sent to the tip/apex of the ventricles
-
This delays the impulse (about 0.1 sec) before passing it on to the
ventricles
-
At the bottom of the wall separating the two auricles / atria is the
atrioventricular node AVN
-
Thin layer of connective tissue prevents the stimulus spreading to the
ventricles
-
The SAN may be stimulated by various factors to change its pacing
- One example – hormones (adrenalin), exercise, body temperature, etc. (allow: ref. autonomic nervous system)
-
Heart muscle is myogenic
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