Cardiovascular System Flashcards
Cardiac conduction system
Heart muscle = myogenic
Beat starts in heart muscles with an electric signal in the sino-atrial node (SAN) spreads through heart as wave of excitation.
SAN -> through walls of atria, causing atrial systole (contracts). Impulse then through atrial ventricular node (AVN), delayed of approx 0.1 seconds to allow full contraction, through bundle of his, into purkinje fibres, through ventricles causing it to contract (ventricle systole)
Factors affecting change in rate of conduction system
Neural control
Sympathetic = beats faster
Parasympathetic = returns to resting level = coordinated by medulla
- chemoreceptors = detects increase in blood CO2 -> cardiac control centre -> sympathetic system -> SAN increases heart rate
- baroreceptors = detects increase in blood pressure -> cardiac control centre -> parasympathetic system -> SAN decreases heart rate
- proprioceptors = detects increase in muscle movement -> cardiac control centre -> sympathetic system -> SAN increases heart rate
Factors affecting change in rate of conduction system
Hormonal control
Adrenaline
Released by sympathetic nerve -> stimulates SAN -> increases cardiac output
Starlings law
(Stretchy heart one)
Think balloon filling
- increased venous return (blood back to heart)
- due to vascular shunt reasons
= increased stretch of heart
= increased ejection fraction
= more blood (O2) to muscles
Heart rate during exercise
Cardiac hypertrophy = bigger + stronger
Bradycardia = a decreased heart rate below 60 -> less oxygen needed
Cardiac output during exercise
Definitions = volume of blood pumped out of ventricles
Cardiac output = stroke x heart rate
- cardiac output increases during exercise due to increase heart rate + stroke volume
Impact of exercise on health
Heart disease
Lack of exercise can cause atherosclerosis which is when arteries harden + narrow + become clogged with fatty deposits
Impact of exercise on health
High blood pressure
Regular heart rate can reduce blood pressure which decreases the risk of a heart attack
Cholesterol levels
LDL (low density lipoproteins) - transport cholesterol into blood = linked to increased risk of heart disease
HDL (high density lipoproteins) - transports excess cholesterol from blood back to liver
Exercise decrease LDL + increases HDL
Stroke
Regular exercise can help to lower blood pressure + maintain a health weight which can reduce risk of stroke
Cardiovascular drift
(Sweating = increased HR)
Tip = mentions warm environment
Def = increased heart rate during steady state exercise
Reasons why this causes heart rate to increase
1 you sweat
2 = decrease in water
3 plasma made of water = less blood
4 = less O2 carrying ability
5 = blood more viscous
Increase heart rate needed to keep up with demand
Blood vessels
Veins = deoxy blood back to heart -> thin muscular walls, valves, wide lumen
Arteries = oxy blood round body -> high pressure, thick, elastic walls, small lumen
Capillaries -> one cell thick, allows diffusion of nutrients
Blood pressure
= force exerted by the blood
Blood flow x resistance
Systolic = when ventricles are contracting
Dystolic = when ventricles are relaxing
Venous return
= return of blood to right side of the heart
- skeletal muscle pump =muscles contract + relax, they change shape
- the respiratory pump = pressure changes in thoracic + abdominal cavities
- pocket valves = blood flow in 1 direction
- gravity
Impact of blood pressure on venous return
Systolic blood pressure decreases = venous return decreases
Systolic blood pressure increases = venous return increases
