6.1.3 Control of heart rate Flashcards
What does the heart muscle being myogenic mean?
This means that the contractions of the heart muscle are initiated from within the heart muscle itself, not the nervous system
What is the role of the autonomic nervous system
To speed up or slow down the heart rate
Preparing the body for action
What is the parasympathetic nervous system involved in?
Generally involved in returning the body to normal to conserve energy and replenishing resources, slow heart rate
What is the sympathetic nervous system involved in?
Generally involved in preparing the body for action, increase heart rate
How is the cardiac cycle is controlled by SAN and AVN?
- SAN initiates heartbeat
- Electrical impulses from SAN spread across the atria walls, causing contraction
- AVN delays impulses
- Allowing atria to empty before ventricles contract
- AVN sends impulses down Purkyne fibres in bundle of His
- Causing ventricles to contract from apex upwards (ventricular systole). Blood is squeezed into the arteries
What happens during exercise when the blood pH decreases?
- Chemoreceptors (near carotic arteries) detect the decrease in pH of the blood
- Send electrical impulses to sensory neurone towards the relay neurone in the medulla oblongata
- So send more nerve impulses pass the SAN to the sympathetic neurone to increase heart rate
- Therefore gets rid of CO2, so pH increases to the same point
- Negative feedback
What are baroreceptors?
Located in the swelling of the carotid artery called the carotid sinus, and in the walls of the heart
What is the medulla oblongata?
Region of the brain that can modify heart rate
What happens when there is low blood pressure?
More frequent impulses to medulla/cardiovascular control centre
- More frequent impulses sent to SAN along sympathetic neurones - more frequent impulses sent from SAN - cardiac muscle contracts more frequently so heart rate INCREASES
