2.6 The Structure and Function of the Heart

State the 2 types of valves and their location

atrial-ventricular valves - between atrium and ventricle
semi-lunar valves - between artery and ventricle

State the purpose of valves

to prevent the backflow of blood

When does SL valves open

during ventricular systole
close when arterial pressure exceeds ventricular pressure

Define stroke volume

the volume of blood expelled by each ventricle during systole
stronger the contraction, greater the stroke volume

Define cardiac output

volume of blood pumped through each ventricle per minute
CO = HR x SV

Define cardiac cycle

pattern of systole and diastole shown by the heart during 1 complete cycle

State the average cardiac cycle timing

0.8 second - 75 bpm
0.4 sec diastole
0.1 atrial systole
0.3 ventricular systole

What happens during diastole

blood return to heart in atria, AV open, SL close

What happens during atrial systole

blood pumped from atria to ventricle, AV open, SL close

What happens during ventricular systole

blood pumped from ventricle to arteries, AV close, SL open

What is heard using a stethoscope

opening and closing of AV and SL valves

State location of the sino-atrial node

right atrium wall

What is contained within SAN

auto-rhythmic cells

State purpose of SAN

set the rate at which the heart contract

State the 4 steps to cardiac contraction

1. SAN send a wave of excitation across the atria
2. atria systole
3. impulse travel to atria-ventricular node (AVN) in the centre of the heart then to conducting fibres down the septum and around the ventricular walls
4. ventricular systole

Define electrocardiogram

detection of the electrical activity of the heart

State number of waves on an ECG

P, QRS and T

State purpose of P wave

wave of excitation spreading over atria from pacemaker

State purpose of QRS spike

wave of excitation through the ventricles

State purpose of T wave

electrical recovery at end of ventricular systole

State the nervous system control of the heart

autonomic

State the term that describe the ANS and define it

antagonistic - opposite effect

State the 2 nerves controlling the heart

sympathetic, parasympathetic

State the hormone stimulate by the sympathetic nerves and its purpose

noradrenaline - increase heart rate

State the hormone stimulated by the parasympathetic nerves and its purpose

acetylcholine - decrease heart rate

Where is noradrenaline produced

adrenal glands in kidney

Define blood pressure

force exerted by blood against the walls of the blood vessels

How is BP measured

sphygmomanometer

State units of BP

mmHG (millilitres of mercury)

State average blood pressure

120/80 mmHg

How is the sphygmomanometer used

1. inflatable cuff stops blood flow
2. allowed to deflate, blood begin to flow, systolic pressure detected
3. deflate until no pulse is detected, diastolic pressure detected

State term describing high blood pressure

hypertension

State BP of patients with hypertension

140/90 mmHg

Define hypertension

prolonged elevation of blood pressure when at rest