What does it mean that cardiac muscle is myogenic?
It initiates electrical activity without stimulation by a nerve.
AQA A-Level Biology - (7402) · 3.6.1.3
Revise AQA A-Level Biology - (7402) specification point 3.6.1.3, Control of heart rate (A-level only), with free active-recall flashcards. Flip through the set or review every question and answer below.
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What does it mean that cardiac muscle is myogenic?
It initiates electrical activity without stimulation by a nerve.
What is the role of the sinoatrial node (SAN) in the heart?
It acts as the pacemaker, generating waves of electrical activity that spread across the atria and cause them to contract.
What prevents excitation from passing directly from the atria to the ventricular muscle?
Non-conducting tissue between the atria and ventricles.
Why does the atrioventricular node (AVN) delay transmission of excitation?
To allow atrial contraction to finish before the ventricles contract.
What route does excitation take through the ventricles after leaving the AVN?
It travels down the bundle of His in Purkyne tissue towards the apex, then spreads through the ventricular walls.
In which direction do the ventricles contract, and what does this help achieve?
From the apex upwards, helping to force blood out of the heart.
Where are the chemoreceptors involved in heart-rate control, and what do they detect?
In the carotid arteries and aorta; they detect changes in blood chemistry, including the fall in pH associated with increased carbon dioxide.
How can increased carbon dioxide affect heart rate, and what does this help achieve?
It can increase heart rate, helping transport carbon dioxide to the lungs.
Where are the pressure receptors involved in heart-rate control, and what do they detect?
In the walls of the carotid arteries and aorta; they detect changes in blood pressure.
How do pressure-receptor signalling and heart rate respond to a rise versus a fall in blood pressure?
These responses oppose the original pressure change.
Where is the cardiovascular centre that controls heart rate?
In the medulla oblongata.
How does the cardiovascular centre send signals to the heart?
It sends impulses along autonomic nerves.
How does sympathetic stimulation affect heart rate?
It increases the rate at which the sinoatrial node generates excitation, increasing heart rate.
How does parasympathetic stimulation affect heart rate?
It decreases the rate at which the sinoatrial node generates excitation, lowering heart rate.
What is the effector in autonomic heart-rate responses?
The heart.