Cardiovascular System Flashcards
what are the three layers of the heart wall?
- EPIDCARDIUM
outer protective layer - MYOCARDIUM
muscular middle
layer
can undergo cardiac
hypertrophy - ENDOCARDIUM
thin inner layer
the cardiovascular system is composed of three main parts…
- the heart
- the blood vessels
- the blood
the main functions of the cardiovascular system (3)
- transport of nutrients and removal of waste products
- blood cell production
- thermoregulation
why is the heart known as a double pump system? (3)
- because it has two circuits that are constantly at work
-the pulmonary circuit carries deoxygenated blood to the lungs and oxygenated blood back to the heart
- the systemic circuit carries oxygenated blood to the body tissues and deoxygenated blood back to the heart
the conduction system (4)
SINOATRIAL NODE
- the heart’s natural pacemaker
- sends an electrical signal that tells the heart to beat.
- this signal starts in the upper right part of the heart and allows the atria to fill with blood
ATRIOVENTRICULAR NODE
- after the signal from the SA node causes the atria to contract, the AV node slows the signal down slightly before sending it to the ventricles
- this delay allows the atria to empty fully before the ventricles contract
BUNDLE OF HIS
- the electrical signal travels from the AV node to the bundle of His, which splits into two branches. one for each ventricle.
PURKINJE FIBRES
- spread the electrical signal throughout the ventricles
- this causes them to contract and pump blood out of the heart
how does the SA node generate its own electrical signals? (2)
- it receives messages from the PNS and the SNS to adjust the heart rate, either by increasing it or decreasing it.
- the cells within the SA node are classed as ‘self-excitable’
define heart rate
the number of times at which the heart beats per minute
define bradycardia
a decrease in resting heart rate to below 60 BPM
define stroke volume
the volume of blood pumped out of the left ventricle per beat
what is the average stroke volume at rest?
70 ML
how is stroke volume determined? (3)
-
venous return
- if the venous return increases, stroke volume will also increase -
elasticity of the cardiac fibres
- the degree of the stretch during the diastole phase
- the greater the degree of stretch = greater force of contraction = greater SV -
contractility of the cardiac tissues
- the greater the contraction of cardiac tissues = greater force of contraction = greater SV
define ejection fraction
the percentage of blood pumped out of the left ventricle, per beat
define venous return
the volume of blood returning to the heart via the veins
list the five mechanisms of venous return
- pocket valves
- skeletal muscle pump
- respiratory pump
- smooth muscle
- gravity
pocket valves (3)
- located in the veins
- prevent the backflow of blood
- helps blood move in one direction (towards the heart)
skeletal muscle pump (3)
- during upright posture
- skeletal muscles compress underlying veins and contract them
- this increases blood flow back to the heart