7.3 Peak performance Flashcards
When exercising adequate O2 supply is maintained by:
- increasing cardia output
- faster rate of breathing
- deeper breathing
Aerobic capacity
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.
V̇
O2, V̇O2(max)
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.
Cardiac output
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.
Stroke volume
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.
Heart rate
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.
Venous return
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.
Myogenic
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.
Sinoatrial node, Pacemaker, SAN
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.
Impulse, Nerve impulse
A wave of electrical
activity which passes along a nerve or over the
surface of a muscle.
Atrioventricular node, AVN
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.
Purkyne fibres
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.
Bundle of His
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.
Bradycardia
A heart rate of less than 60 ppm.
possible causes include: hypothermia, heart disease, use of medicines or drugs, fit athlete
Tachycardia
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
Electrocardiogram
A graphic record of the
electrical activity of the heart as it contracts and
rests.
Polarisation
The formation of an uneven
distribution of ions across a cell surface
membrane making the outside of the membrane
positive and the inside negative.
P wave
Depolarisation of the atria that leads to atrial contraction (atrial systole).
PR interval
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.
QRS complex
The wave of depolarisation that
results in contraction of the ventricles
(ventricular systole).
T wave
Repolarisation (recovery) of the
ventricles during the heart’s relaxation phase
(diastole).
Cardiovascular control centre
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.
Autonomic nervous system
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.
Sympathetic nerve
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.
Vagus nerve
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
Parasympathetic nervous system,
Parasympathetic nerve
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.
Negative feedback
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.
Adrenaline
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.
Tidal volume
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.
Vital capacity
The maximum volume of air a
person can inhale and exhale.
Medulla oblongata
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.
Minute ventilation
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.
Slow twitch fibre
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.
Myoglobin
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.
Fast twitch fibre
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.
