7.3 Peak performance

Question 1

When exercising adequate O2 supply is maintained by:

Answer 1

• increasing cardia output
• faster rate of breathing
• deeper breathing

Question 2

Aerobic capacity

Answer 2

The ability to take in, transport
and use oxygen. Our aerobic capacity
determines our ability to undertake long periods
of vigorous exercise such as running steadily.

Question 3

V̇

O2, V̇O2(max)

Answer 3

The volume of oxygen a person
consumes per minute. V̇O2(max) is the volume
of oxygen a person consumes per minute at their
maximum rate of aerobic exercise. V̇ O2(max)
depends on the efficiency with which the lungs
and cardiovascular system take up and deliver
oxygen, and the efficiency with which muscles
use oxygen.

Question 4

Cardiac output

Answer 4

The total volume of blood
pumped out of the left ventricle of the heart in
one minute. The cardiac output depends on the
volume of blood pumped out each time the heart
beats (the stroke volume) and the heart rate.
The relationship between cardiac output, stroke volume and heart rate is given by the equation:
cardiac output = stroke volume × heart rate.

Question 5

Stroke volume

Answer 5

The volume of blood pumped out
of the left ventricle each time the ventricle
contracts. The total amount of blood pumped out
of the heart in one minute is the cardiac output.
The relationship between cardiac output, stroke
volume and heart rate is given by the equation:
cardiac output = stroke volume × heart rate.

Question 6

Heart rate

Answer 6

The number of times the heart beats
per minute. Heart rate varies. Differences in
heart rate are caused by many factors and are
controlled by the cardiovascular control centre
in the brain. The total amount of blood pumped
out of the heart in one minute is the cardiac
output. The relationship between cardiac output,
stroke volume and heart rate is given by the
equation: cardiac output = stroke volume × heart
rate.

Question 7

Venous return

Answer 7

The blood returning to the atria of
the heart along the veins. The increase in muscle
action during exercise increases the venous
return. This results in more blood entering the
atria and more forceful contractions of the
ventricle, increasing stroke volume.

Question 8

Myogenic

Answer 8

Muscle which is able to contract
without being stimulated to do so by a nerve.
Heart muscle is myogenic; the sinoatrial node,
a group of specialised muscle fibres within the
heart wall, initiates the heartbeat.

Question 9

Sinoatrial node, Pacemaker, SAN

Answer 9

A small area
of specialised muscle tissue in the wall of the
right atrium of the heart. It generates electrical
impulses. These spread across the surface of the
atria causing them to contract at the same time.
The sinoatrial node is also called the pacemaker.

Question 10

Impulse, Nerve impulse

Answer 10

A wave of electrical
activity which passes along a nerve or over the
surface of a muscle.

Question 11

Atrioventricular node, AVN

Answer 11

A small area of
specialised tissue in the wall of the heart
between the atria and the ventricles. It plays an
important part in coordinating the heartbeat. The
electrical impulse, which spreads over the
surface of the atria from the sinoatrial node, is
delayed briefly here before continuing to the
ventricles. This ensures that the atria have
emptied and ventricles have filled with blood
before they start contracting.

Question 12

Purkyne fibres

Answer 12

A group of specialised muscle
fibres which run between the right and left
ventricles of the heart. They conduct the
electrical impulses which cause the ventricle
muscle to contract.

Question 13

Bundle of His

Answer 13

Specialised fibres of heart muscle
that go from the atrioventricular node to the tip
of the ventricles. They rapidly carry the
electrical impulse that controls the heartbeat to
the tip of the ventricles. This means that when
the ventricles start to contract, they squeeze the
blood upwards and out through the arteries to
the lungs and the rest of the body.

Question 14

Bradycardia

Answer 14

A heart rate of less than 60 ppm.

possible causes include: hypothermia, heart disease, use of medicines or drugs, fit athlete

Question 15

Tachycardia

Answer 15

A heart rate greater than 100bpm
causes: anxiety, fear, fever, exercise, symptom of heart disease, heart failure, use of medicines or drugs, fluid loss, anaemia

Question 16

Electrocardiogram

Answer 16

A graphic record of the
electrical activity of the heart as it contracts and
rests.

Question 17

Polarisation

Answer 17

The formation of an uneven
distribution of ions across a cell surface
membrane making the outside of the membrane
positive and the inside negative.

Question 18

P wave

Answer 18

Depolarisation of the atria that leads to
atrial contraction (atrial systole).

Question 19

PR interval

Answer 19

The time taken for electrical
impulses in the heart to be conducted from the
sinoatrial node across the atria to the
ventricles, through the atrioventricular node.

Question 20

QRS complex

Answer 20

The wave of depolarisation that
results in contraction of the ventricles
(ventricular systole).

Question 21

T wave

Answer 21

Repolarisation (recovery) of the
ventricles during the heart’s relaxation phase
(diastole).

Question 22

Cardiovascular control centre

Answer 22

An area situated
in the brain which is responsible for controlling
the heart rate. The cardiovascular control centre
receives stimuli resulting from the accumulation
of carbon dioxide and lactate in the blood. It sends impulses
via branches of the autonomic nervous system
to the sinoatrial node in the heart, causing the
heart rate either to slow down or to speed up.

Question 23

Autonomic nervous system

Answer 23

The part of the
nervous system that is not under conscious
control. The nerves of the autonomic nervous
system stimulate muscles and glands. The
autonomic nervous system is made of up of two
parts. The sympathetic system plays an
important part in controlling the body’s reactions
to stress. The parasympathetic is more
important when the body is at rest. The somatic
nervous system is under conscious control.

Question 24

Sympathetic nerve

Answer 24

One of the nerves that goes
from the brain to the organs of the body and
which prepares the body for action, controlling
the functions of organs during times of stress.
For example, sympathetic nerves are involved in
increasing heart rate and blood pressure.

Question 25

Vagus nerve

Answer 25

The vagus nerve is a
parasympathetic nerve. It leads from the
cardiovascular control centre in the brain to
the sinoatrial node in the heart. Nerve impulses
passing along this nerve slow the heart beat

Question 26

Parasympathetic nervous system,

Parasympathetic nerve

Answer 26

The part of the
autonomic nervous system (the nervous system
which you have no control over) that is
important when the body is at rest. Stimulation of the parasympathetic nerves reduces heart and
breathing rate but increases muscle action
associated with digestion. The vagus nerve is a
parasympathetic nerve. It leads from the
cardiovascular control centre in the brain to
the sinoatrial node in the heart. Nerve impulses
passing along this nerve slow the heart beat.

Question 27

Negative feedback

Answer 27

Many substances and systems
in living organisms have a set level. This is true
of the concentration of glucose in the blood and
of body temperature. Negative feedback is the
process whereby a departure from this set level
sets in motion changes which return it to the
original level.

Question 28

Adrenaline

Answer 28

A hormone produced by the adrenal
glands at times of stress such as when we are
angry or frightened. It has a range of effects on
the body. These include increasing the stroke
volume and rate of beating of the heart, dilating
blood vessels supplying muscles, and
stimulating the conversion of glycogen to
glucose. Scientists have shown that there are
links between stress, adrenaline and an
increased risk of heart disease.

Question 29

Tidal volume

Answer 29

Tidal volume is the average
volume of one breath. Multiplying the tidal
volume by the breathing rate gives the volume
of air taken into the lungs in one minute, the
minute ventilation. Minute ventilation is
calculated from tidal volume and breathing rate
using the equation: minute ventilation = tidal
volume × breathing rate.

Question 30

Vital capacity

Answer 30

The maximum volume of air a

person can inhale and exhale.

Question 31

Medulla oblongata

Answer 31

Part of the hindbrain or brain
stem which is responsible for controlling body
processes that we do not consciously have to
control. These include heart rate, breathing and
blood pressure.

Question 32

Minute ventilation

Answer 32

The volume of air taken into
the lungs in one minute. Minute ventilation is
calculated from tidal volume and breathing
rate using the equation: minute ventilation =
tidal volume × breathing rate.

Question 33

Slow twitch fibre

Answer 33

A muscle fibre that produces
slow, sustained contractions. The long periods of
exercise of which they are capable necessitates
respiring aerobically. Associated with this, they
have a large number of mitochondria and also
contain a lot of the pigment myoglobin. These
features give them their distinctive dark red
colour.

Question 34

Myoglobin

Answer 34

An oxygen-storing pigment found in
the muscle of many animals. It is saturated with
oxygen at relatively low oxygen concentrations
(low partial pressures) and is able to hold onto
this oxygen, only releasing it when the amount
of oxygen in the surroundings falls to a very low
level. Slow twitch fibres are muscle fibres
which contain a lot of myoglobin. This results in
their dark red colour.

Question 35

Fast twitch fibre

Answer 35

A muscle fibre that produces
rapid powerful contractions. Fast twitch fibres
have few mitochondria and little myoglobin.
This makes them light-coloured in appearance.
Contraction of fast twitch fibres relies on
anaerobic respiration and therefore results in a
rapid build-up of lactate and a correspondingly
rapid onset of fatigue.