control of heart rate Flashcards
function of autonomic nervous system
controls involuntary activities of internal muscles and glands
what does the sympathetic nervous system do
-stimulates effectors by speeding up activity
-controls effectors when we exercise strenuously / experience powerful emotion
-help cope with stressful situations by heightening awareness and preparing us for activity ( fight or flight)
what does parasympathetic nervous system do
-inhibits effectors to slow down any activity
-controls activities under normal resting condition
-concerned with conserving energy + replenishing the body’s reserves
what are SNS and PNS
antagonistic ( as they oppose each other)
What does myogenic means?
a muscle that can contract/relax without receiving electrical impulses from nerves
sequence of events that controls the basic heart rate
1) sinoatrial node (SAN) acts as a pacemaker > regular waves of electrical excitation across both atria causing simultaneous contraction
2) layer of non-conducting tissue (atrioventricular septum) prevents waves crossing to ventricles > so preventing immediate contraction of ventricles
3) waves of electrical activity reach atrioventricular node (AVN) which delays impulse > allowing atria to fully contract and empty before ventricles contract
4) AVN sends waves of electrical activity down bundles of His, conducting wave between ventricles to apex where branches into purkyne tissue > causing ventricles to contract quickly and simultaneously from bottom of heart upwards
What is the SAN?
(sinoatrial node) is a group of cells/tissues found in the right atrium that can release a wave of electricity/depolarisation which causes contraction
What is the AVN? Where is it located?
Atrio-ventricular node, located in the atria, near the border of the right and left ventricles
What is the bundle of His?
conductive tissue located in the septum and ventricular walls
What are the Purkyne fibres?
conductive tissues that go all the way through the walls of the ventricles
What is the role of the SAN?
to release a wave of depolarisation, causing both atria to contract
What does the AVN do?
release another wave of depolarisation (when the 1st reaches it)
Why cant the electricity from the AVN move straight to the ventricles?
insulating fibres between atria and ventricles
What is the role of the bundle of His?
to carry the wave of depolarisation from the atria through to the purkyne fibres in the walls of the ventricles
What part of the heart contracts first?
apex/tip
