control of heart beat and heart rate

Question 1

the cardiac muscle (the heart) is …?

Answer 1

myogenic

Question 2

what does myogenic mean?

Answer 2

myogenic means that the cardiac muscles can contract and relax without receiving external signals from the NS

Question 3

what does the cardiac muscle create?

Answer 3

the cardiac muscle can create its own action potentials.

Question 4

what is the role of the sinoatrial node (SAN) in creating a heart beat?

Answer 4

The sinoatrial node generates electrical impulses that cause the cardiac muscles to contract, controlling the process of the heart beat.

Question 5

where does the process of the heart beat start?

1

Answer 5

the process starts in the sinoatrial node (SAN) in the wall of the right atrium.

Question 6

the SAN is like a what … and how is the SAN like this?

2

Answer 6

The SAN is like a pacemaker - it sets the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls. This causes the right and left atria to contract at the same time.

Question 7

A layer of non-conducting tissue prevents what ?

3

Answer 7

A layer of non-conducting tissue prevents the wave of electrical activity from passing to the ventricles.

Question 8

wave of electrical activity passes from …

4

Answer 8

wave of electrical activity passes from SAN to atrioventricular node (AVN).

Question 9

the atrioventricular node passes the wave of electrical activity to the …

Before this happens there is a what?

(5)

Answer 9

the atrioventricular node passes the wave of electrical activity to the bundle of His.

Before this happens there is a slight delay which ensures the atria have emptied before the ventricles contract.

Question 10

what is the bundle of His?

6

Answer 10

they bundle of His is a group of muscle fibres which conducts the wave of electrical activity along the septum to the apex (bottom) of the heart. The bundle of His branches out into Purkyne tissue which runs along the underside of each ventricle

Question 11

what does the Purkyne tissue do?

Answer 11

The Purkyne tissue carries the waves of electrical activity into the muscular walls of both ventricles causing them to contract simultaneously, from the bottom up pumping blood out of the heart.

Question 12

what receptors are used to detect internal stimuli (changes in blood) which could result in changes to the heart rate?

Answer 12

chemoreceptors

pressure receptors

Question 13

what is the internal stimuli in the process of controlling heart rate?

Answer 13

the internal stimuli is the change in blood.

Question 14

when a stimuli has been detected, what happens?

Answer 14

chemoreceptors or baroreceptors send impulses along sensory neurones to the medulla oblongata which contains the cardio-regulatrory centre.

Question 15

what does the cardio-regulatory centre do?

Answer 15

the cardio-regulatory centre in the medulla oblongata acts as the co-ordinator and signals a response via the autonomic nervous system

Question 16

the set of motor neurones used to send impulses to the effectors depends on what?

Answer 16

the set of motor neurones used to send impulses to the effectors depends on whether the heart rate needs to increase or decrease.

Question 17

what happens if the heart rate needs to increase?

Answer 17

if the heart rate needs to increase, then the medulla sends impulses along the sympathetic neurones (fight or flight)

Question 18

what happens if the heart rate needs to decrease?

Answer 18

if the heart rate needs top decrease, then the medulla sends impulses along the parasympathetic neurones ( rest and digest).