Control Of Heart Rate Flashcards
What does the autonomic nervous system control
The involuntary activities of the internal muscles and glands
What does the autonomic nervous system divide into
Sympathetic Nervous system
Parasympathetic nervous system
What does the sympathetic nervous system do
Stimulates effectors and so speed up any activity.
It controls effectors when we exercise strenuously or experience powerful emotions
It helps us cope with stressful situations by heightening our awareness and preparing us for activity
What does the parasympathetic nervous system do
Inhibits effectors and slows down any activity
It controls activities under normal resting conditions
It is concerned with conserving energy and replenishing the body’s reserves
What does it mean when you say that the sympathetic and parasympathetic nervous systems are antagonistic
If one system contracts a muscle, then the other relaxes it
Describe the sequence of events that controls the heart rate
Process starts in wall of RA
A wave of electrical excitation spreads out from the SA node across both atria causing them to contract,
A layer of non conductive collagen tissue prevents the wave crossing to the ventricles
These waves of electrical activity are passed from the SA node to the AV node
After a short delay, the AV node conveys a wave of electrical excitation onto the bundle of his
The bundle of his conducts the wave through the atrioventricular septum to the base of the ventricles, where the bundles branches into smaller fibres of purkyne tissue
The wave of excitation released from the purkyne tissue, causing the ventricles to contract quickly at the same time, from the bottom of the heart upwards
What two centres does the medulla oblongata have that are concerned with heart rate
A centre that increases heart rate - which is linked to the SAnode by the sympathetic nervous system
A centre that decreases heart rate, which is linked to the SAnode by the parasympathetic nervous system
Where are chemoreceptors found
In the wall of the carotid arteries
What makes them sensitive to pH in the blood
Results from changes in co2 concentration, in solution co2 forms an acid and therefore lowers pH
Describe the process of control by chemoreceptors
Increase muscular activity
More co2 produced by tissues from increased respiration
Blood pH is lowered
Chemoreceptors in the carotid arteries increase frequency of impulses in the medulla oblongata
Centre in the medulla oblongata that speeds heart rate, increase frequency of impulses to the SA node via the sympathetic nervous system
SA node increase heart rate
Increase blood flow removes carbon dioxide faster
Carbon dioxide concentration returns to normal, and carotid arteries and aorta reduce frequency of nerve impulses to the medulla oblongata
Medulla oblongata reduces frequency of impulses to the SA node, which therefore leads to a reduction in the heart rate
What do pressure receptors do when blood pressure is higher then normal
They transmit more nervous impulses to the centre in the medulla oblongata they decreases heart rate.
This centre sends impulses via the parasympathetic nervous system to the SA node or the heart rate, which leads to a decrease in the rate at which the heart beats
What do pressure receptors do when blood pressure is lower then normal
They transmit more nervous impulses to the centre in the medulla oblongata that increases heart rate.
This centre sends impulses via the sympathetic nervous system to the SA node, which increases the rate at which the heart beats
