control of heart rate

Question 1

Describe the myogenic stimulation of the heart and transmission of a
subsequent wave of electrical activity

Answer 1

*Sinoatrial node (SAN) acts as pacemaker → releases regular waves of electrical activity across atria
○causes atria to contract simultaneously
*Non-conducting tissue between atria / ventricles prevents impulse passing directly to ventricles
- prevents immediate contraction of ventricles
*Waves of electrical activity reach atrioventricular node (AVN) delays impulse
-allows atria to fully contract and empty before ventricles contract
*AVN sends wave of electrical activity to bundle of His, conducting wave between ventricles to apex where it branches into Purkyne tissue
-ventricles contract simultaneously from the base up

Question 2

Where are chemoreceptors and pressure receptors located?

Answer 2

aorta and carotid arteries

Question 3

Describe the roles of chemoreceptors, pressure receptors, the autonomic
nervous system and effectors in controlling heart rate

Answer 3

*baroreceptors detect [fall / rise] in blood
PRESSURE and / or chemoreceptors detect
blood [rise / fall] in blood CO2 conc/ blood pH
* impulses sent to medulla / cardiac
control centre
*send more frequent impulses to
SAN along [para/sympathetic] neurones
*so [more / less] frequent impulses sent
from SAN and to / from AVN
*so cardiac muscle contracts [more / less]
frequently
*so heart rate [increases / decreases]