14.5: Control of heart rate Flashcards
The autonomic nervous system
Controls the involuntary activities of internal muscles and glands
Two divisions of the autonomic nervous system
the sympathetic nervous system
the parasympathetic nervous system
The sympathetic nervous system
Acts like an emergency controller which controls effectors and speeds up any activity.
Example of effectors the sympathetic nervous system controls
effectors when we exercise or experience powerful emotions
The parasympathetic nervous system
This inhibits effectors and so slows down any activity, controls activities under normal resting conditions.
Example of the parasympathetic nervous system functions
conserving energy and replenishing the body’s reserves
Relationship between the sympathetic nervous system
and the parasympathetic nervous system
antagonistic (oppose each other)
Muscle of the heart
cardiac muscle
Myogenic
Contraction without external input
Is the cardiac muscle myogenic or neurogenic
myogenic
Sinoatrial node (SAN)
A group of cells within the wall of the right atrium of the heart, where the initial stimulus for contraction originates
SAN aka
pacemaker
SAN has a …
… basic rhythm of circulation it determines for the beat of the heart
In the basic control of heart rate,
what causes both atria to contract?
A wave of electrical excitation spreads out from the sinoatrial node across both atria, causing them contract
In the basic control of heart rate,
what prevents the wave of electrical excitation from crossing to the ventricles?
The atriventricular septum is a layer of non-conductive tissue which prevents the wave from crossing to the ventricles
In the basic control of heart rate,
after causing the atria to contract, where does the wave of electrical excitation go?
the wave of excitation enters a second group of cells called the atrioventricular node (AVN), which lies between the atria.
In the basic control of heart rate,
where does the AVN send a wave of electrical excitation?
the AVN conveys a wave of electrical excitation between the ventricles along a series of specialised muscle fibres called purkyne tissue which collectively make up the bundle of His
In the basic control of heart rate,
what does the bundle of His do once its received the wave of electrical excitation?
the bundle of His conducts the wave through the atrioventricular septum where the bundle of His branches into smaller fibres of the purkyne tissue, then a wave of excitation is released, causing the ventricles to contract from the bottom of the heart upwards.
Whats makes up the bundle of His
the purkyne tissue
What controls changes to the resting heart rate?
the medulla oblongata
Two centres in the medulla oblongata
- a centre that increases heart rate which is linked to the SAN by the sympathetic nervous system
- a centre that decreases heart rate which is linked to the SAN by the parasympathetic nervous system
Where are chemoreceptors found?
In the wall of the cartoid arteries
Cartoid arteries
arteries that serve the brain
What are chemoreceptors sensitive to?
sensitive to changes in pH of the blood which result from changes in CO2 conc.
Where are pressure receptors found
In the walls of the carotid arteries and the aorta
When blood pressure is higher than normal the pressure receptors…
Transmit more nervous impulses to the centre in the medulla oblongata that decreases heart rate.
When blood pressure is lower than normal the pressure receptors…
Transmit Transmit more nervous impulses to the centre in the medulla oblongata that increases heart rate.
