control of heart rate

Question 1

explain what is meant by a myogenic heartbeat

Answer 1

the heart generates its own contractions and beats on it own

Question 2

despite being myogenic, what can be changed in response to changes in the environment

Answer 2

the rate of the heartbeat

Question 3

which nervous system and where in the brain controls the rate of heartbeat

which hormones can change it

Answer 3

-by nerve impulses from the autonomic nervous system and the medulla oblongata (cardiovascular centre)

by hormones such as adrenaline

Question 4

explain how and the effect of the sympathetic nervous system on the heart rate

Answer 4

-action potentials sent along sympathetic nerve (the accelerans nerve)
-releases noradrenaline at SAN
-stimulates effector (cardiac muscle)
-speeds up activity
-increases heart rate and stroke volume

Question 5

explain how and the effect of the parasympathetic nervous system on the heart rate

Answer 5

-action potentials sent along parasympathetic nerve (vagus nerve)
-release acetylcholine at SAN
-inhibits effector (cardiac muscle)
-slows down activity
-decreases heart rate and stroke volume

Question 6

what factors affect heart rate

Answer 6

-blood pressure
-co2 levels/ carbonic acid/ pH
e.g exercise

Question 7

what are the receptors that detect pH of blood and stretch and thus send signals which determine whether sympathetic or parasympathetic centres are stimulated?

Answer 7

-chemoreceptors= in walls of carotid arteries, aorta and medulla detect changes in pH of blood as a result of changing co2 conc

-stretch receptors/ baroreceptors= in walls of carotid sinus detect stretch as a result of increasing blood pressure
-also in muscles include imprtance of warming up before exercise

Question 8

explain what happens when co2 conc in blood is low vs high

Answer 8

low:
-cardioacceleratory centre in nedulla/ sympathetic nervous system releases noradrenaline= increased heartbeat rate, increased stroke volume, increased forced contraction

high:
-cardioinhibitory centre in medulla/ parasympathetic nervous system releases acetylecholine= decreases heartbeat reate, decreased stroke volume, decreased force of contraction

Question 9

explain what happens when blood pressure is high vs low

Answer 9

blood pressure detected by receptors in walls of aorta and carotid arteries
low:
-cardioacceleratory centre/ sympathetic nervous system releases noradrenaline= increased heartbeat rate, increased stroke volume, increased forced contraction

high:
-cardioinhibitory centre in medulla/ parasympathetic nervous system releases acetylecholine= decreases heartbeat reate, decreased stroke volume, decreased force of contraction