control of heart rate

Question 1

what controls the regular beating of the heart

Answer 1

Cardiac Muscle Controls the Regular Beating of the Heart

Question 2

the cardiac muscle is myogenic, what does this mean

Answer 2

— it can contract and relax with out receiving signals from nerves.
This pattern of contractions controls the regular heartbeat

Question 3

what is step 1 of controlling the regular beating off the heart

Answer 3

The process starts in the sinoatrial
node (SAN), which is in the wall of
the right atrium.

Question 4

what is step 2 of controlling the regular beating off the heart

Answer 4

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

Question 5

what is step 3 of controlling the regular beating off the heart

Answer 5

This causes the right and left atria

to co n tract at the same time

Question 6

what is step 4 of controlling the regular beating off the heart

Answer 6

A band of non-conducting collagen
tissue prevents the waves of electrical
activity from being passed directly
from the atria to the ventricles

Question 7

what is step 5 of controlling the regular beating off the heart

Answer 7

Instead, these waves of electrical
activity are transferred from the SAN
to the a trio ventricular node (AVN)

Question 8

what is step 6 of controlling the regular beating off the heart

Answer 8

The AVN is responsible for passing the
waves o f electrical activity on to the
bundle o f His. But, there’s a slight delay
before the AVN reacts, to make sure the atria have emptied before the ventricles contract.

Question 9

what is step 7 of controlling the regular beating off the heart

Answer 9

The bundle of His is a group of muscle fibres responsible for conducting the waves of
electrical activity between the ventricles to the apex (bottom) of the heart. The bundle splits
into finer muscle fibres in the right and left ventricle walls, called the Purkyne tissue.

Question 10

what is step 8 of controlling the regular beating off the heart

Answer 10

The Purkyne tissue carries the waves of electrical activity into the muscular walls of the right and left
ventricles, causing them to contract simultaneously, from the bottom up.

Question 11

what does control of the heart involve

Answer 11

the Brain and Autonomic Nervous System

Question 12

what does the sinoatrial node generate

Answer 12

generates electrical impulses that cause the cardiac muscles to contract

Question 13

what is the rate at which the SAN fires controlled by

Answer 13

The rate at which the SAN fires (i.e . heart rate) is unconsciously controlled by a part of the brain
called the medulla oblongata

Question 14

how do animals respond to internal stimuli

Answer 14

Animals need to alter their he art rate to respond to internal stimuli, e.g. to prevent fainting due to low
blood pressure or to make sure the heart rate is high enough to sup ply the body with enough oxygen

Question 15

what are stimuli detected by

Answer 15

Stimuli are detected by pressure receptors and chemical receptors:

Question 16

what are the pressure receptors called

Answer 16

There are pressure receptors called baroreceptors in the aorta and the carotid arteries
(major arteries in the neck). They’re stimulated by high and low blood pressure

Question 17

what are the chemical receptors called

Answer 17

There are chemical receptors called chemoreceptors in the aorta, the
carotid arteries and in the medulla. They monitor the oxygen level in the
blood and also carb o n dioxide and pH (which are indicators of 0 level).

Question 18

what are electrical impulses from receptors sent to

Answer 18

Electrical impulses from receptors are sent to the medulla along sensory neurones.
The medulla processes the information and sends impulses to the SAN along sympathetic or parasympathetic
neurones (which are part of the au to nomic nervous system). There’s more on this on the next page.

Question 19

what receptor detects high blood pressure

Answer 19

Baroreceptors
detect high
blood pressure.

Question 20

what receptor detects low blood pressure

Answer 20

Baroreceptors
detect low
blood pressure

Question 21

what receptor detects High blood
02/low C02
or high pH
levels

Answer 21

Chemoreceptors
detect chemical
changes in the
blood.

Question 22

what receptor detects low blood O2, high CO2 or low pH levels

Answer 22

Chemoreceptors
detect chemical
changes in the
blood

Question 23

what neurone and transmitter responds to high blood presure

Answer 23

Impulses are sent to the medulla, which
sends impulses along parasympathetic
neurones. These secrete acetylcholine
(a neurotransmitter), which binds
to receptors on the SAN.

Question 24

what neurone and transmitter responds to low blood pressure

Answer 24

Impulses are sent to the medulla, which sends
impulses along sympathetic neurones. These
secrete noradrenaline (a neurotransmitter),
which binds to receptors on the SAN

Question 25

what neurone and transmitter responds to high blood O2, low CO2 or high pH levels

Answer 25

Impulses are sent to the medulla, which sends
impulses along parasympathetic neurones.
These secrete ace tylcholine, which binds to
receptors on the SAN

Question 26

what neurone and transmitter responds to low blood o2, high CO2, or low pH levels

Answer 26

Impulses are sent to the medulla, which
sends impulses along sympathetic neurones.
These secrete noradrenaline, which binds to
receptors on the SAN.

Question 27

what effector responds to low blood pressure

Answer 27

Cardiac

muscles

Question 28

what effector responds to high blood pressure

Answer 28

Cardiac

muscles

Question 29

what effector responds to high blood O2, low CO2 or high pH

Answer 29

Cardiac

muscles

Question 30

what effector responds to low blood )2, high CO2, or low Ph levels

Answer 30

Cardiac

muscles

Question 31

what is the response to high blood pressure

Answer 31

Heart rate slows
d own to reduce
blood pressure back
to normal.

Question 32

what is the response to low blood pressure

Answer 32

Heart rate speeds up
to increase blood
pressure back to
normal.

Question 33

what is the response to high blood oxygen, low carbon dioxide or high pH levels

Answer 33

Heart rate decreases
to return 02, CO2
and pH levels back
to normal.

Question 34

what is the response to low blood oxygen, high carbon dioxide or low pH levels

Answer 34

Heart rate increases
to return 02, CO2
and pH levels back
to normal.