Topic 6- Heart rate control Flashcards
The control of heart rate is myogenic, define myogenic
heart will beat without any external stimulus
Where is the sinoatrial node (SAN) located?
In the wall of the right atrium
What is the function of the SAN?
initiates a wave of depolarisation that causes the atria to contract
What prevents the depolarisation from spreading straight to the ventricles?
The Annulus fibrosus (a region of non-conducting tissue)
What is the first step in control of the heartbeat? (In context of contraction of atria and ventricles)
1.SAN initiates a wave of depolarisation that causes the atria to contract
What is the second step in control of the heartbeat? (In context of contraction of atria and ventricles)
2.depolarisation is carried to the atrioventricular node (AVN)
What is the third step in control of the heartbeat?
(In context of contraction of atria and ventricles)
- (after slight delay) AVN is stimulated and passes the stimulation along the bundle of His
-Delay means ventricles contract after atria (and not at the same time)
What is the bundle of his?
-a collection of conducting tissue in the septum
-divides into two conducting fibres, called Purkyne tissue
What is the function of the bundle of his?
carries the wave of excitation along purkyne tissue
What is the function of the purkyne tissues/ fourth step in controlling heartbeats? (In context of contraction of atria and ventricles)
nitiate the depolarization of the ventricles from the apex (bottom) of the heart
What is the first step in controlling the heart beat?
ventricles contract and blood is forced out of the pulmonary artery and aorta
What causes the noise of a heartbeat?
Closing of the valves
Describe the first step in controlling heart rate
-Chemo receptors which detect pH (indirectly co2) and pressure receptors in the walls of the carotid arteries and aorta
Describe the second step in controlling heart rate
-Cardiac centre in the medulla (in the brain) recieves impulses from recptors and sends impulse to SAN
Describe the third step in controlling heart rate
-Motor neurone (leads to an effector)
-Two neurones go from the cardiac centre in the brain to the SAN (pacemaker) on the right atrium of the heart
-Impulses along the sympathetic neurone increase heart rate
-Impulses along parasympathetic neurone decreases heart rate
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Why does blood pressure impact heart rate?
An increase in blood pressure causes stretching of the walls of the carotid arteries and aorta stimulating the pressure recptors
Describe what happens when there is an increase in blood pressure
-Pressure receptor in the aorta +carotid aertieries respond by sending more impulses along sensory neurones
-Cardiac centre in the medulla send impulses along the parasympathetic neurone
-SAN decreases heart rate
-Decrease in blood pressure reduces blood pressure
Describe what happens when there is a decrease in blood pressure
-Pressure receptor in the aorta +carotid aertieries respond by sending less impulses along sensory neurones
-Cardiac centre in the medulla send impulses along the sympathetic neurone
-SAN decreases heart rate
Why do CO2 levels impact heart rate?
-Excercise causes an increase in the rate of aerobic respiration
-Product of aerobic respiration= lactic acid
-This produces more CO2 which dissolves in the blood plasma making the blood more acidic
-pH decreases
Describe what happens when there is an increase in CO2 levels
-Pressure receptor in the aorta +carotid aertieries respond by sending more impulses along sensory neurones
-Cardiac centre in the medulla send impulses along the sympathetic neurone
-SAN increases heart rate
-CO2 is taken to the lungs, moves quickly so is removed from blood faster
Describe what happens when there is a decrease in CO2 levels
-Pressure receptor in the aorta +carotid aertieries respond by sending more impulses along sensory neurones
-Cardiac centre in the medulla send impulses along the parasympathetic neurone
-SAN decreases heart rate
-Decrease in blood pressure reduces blood pressure
