cardiovascular systems Flashcards
components of cv systems
heart
arteries and arterioles
veins and venules
capillaries
purpose of cv system
control blood transport around body
- transport o2 and nutrients to tissues
- removal CO2 from tissues
- transport hormones
regulation body temperature
support immune function
cardiac cycle
diastole
- relaxation phase: pressure in ventricles low
- filling with blood from atria
-> atria pressure > ventricular pressure
-> AV valves open
- 75% blood enters in relaxation
systole
- pressure in ventricles rises
- blood ejected in pulmonary and systemic circulation
-> ventricular pressure > aortic pressure
-> SL valves open
heart sounds
- ‘lub’ = closing of AV valves
- ‘dub’ = closing of SL valves
P wave
- firing of SA node
-stimulates depolarization of atria
QRS complex
- ventricular depolarisation
- hides atrial repolarisation
T wave
- ventricular repolarisation
measure electrical activity of heart
electrocardigogram
- composite record of electrical events
heart rate
frequency of heart beat per min (bpm)
resting values
- ~70 bpm (untrained)
-~ 50 bpm (trained)
-> with 1 beat send more blood to muscles
bradycardia (slow heart rate)
- resting < 60 bpm
tachycardia
- resting > 100 bpm
stroke volume (sv)
amount of blood pumped per heart beat (ml)
stroke volume = end diastolic volume (before contraction) - end systolic volume (after contraction)
resting untrained values
- female = 50 ml
-male = 70 ml
resting trained values
- female = 80ml
- male = 110 ml
cardiac muscle and neural control
cardiac control centre
- cardioaccelerator centre (CAC) at SNS
- cardioinhibitory centre (CIC) at PNS
ejection fraction (EF)
proportion of blood pumped out of the left ventricle with each beat (%)
average 60% at rest
EF(%) =(stroke volume/ end diastolic volume) x 100
cardiac output (Q)
total volume of blood flow from the heart per minute (L/min)
untrained
- female = 3.5 L/min
- male = 4.9 L/min
trained
-female = 4.0 L/min
- males = 5.5 L/min
Q= heart rate x stroke volume
blood pressure
force exerted by blood against the arterial walls during cardiac cycle (mmHg)
systolic blood pressure
- force exerted during ventricular systole
- highest pressure within the vascular system
- changes the most during the day
diastolic blood pressure
- force exerted during ventricular diastole
- lowest pressure within the vascular system
during exercise
- systolic increases
-> beat harder and faster as need to pump more blood to the muscles
-diastolic decreases
blood pressure expressed as ration SBP/DBP
vessel resistance
vessel length x viscosity /(vessel radius)^4
vessel flow
pressure gradient/ vessel resistance
blood flow
pressure gradient x (vessel radius)^4 / vessel length x viscosity
vessel radius had greatest impact
vessel length is constant
slight variation in viscosity
doubling the diameter
- 16 x flow rate increase
halving the diameter
- 16 x flow rate decrease
blood pressure determinants
blood volume
stroke volume
peripheral resistance
blood viscosity
heart rate
vasoconstriction
radius decrease
resistance to flow increases
vasodilation
radius increase
resistance to flow decreases
cardiac muscle
intrinsic heart rate
- internal rhythm set ~ 100 bpm
- resting HR about 70 bpm
- decrease with age
-> neural influence controlled by medulla oblongata can override rhythm
neural control
- cardioaccelerator centre at SNS
-> part of sympathetic nervous system
-> connected with sinus node and AV node
-> cardio inhibitory centre at PNS
parasympathetic nervous: vasodilation
activation of vagus nerves (CN10)
neurons release acetylcholine
inhibits SA and AV discharge delaying the rate of sinus discharge
decrease HR
sympathetic nervous system: vasoconstriction
activate sympathetic cardiac accelerator
nerves release epinephrine (adrenaline) and norepinephrine (noradrenaline) from adrenergic fibres
positive chronotropic and inotropic effects through beta-adrenergic reactions
increase HR
increase ventricular contractility
cardiovascular control centre receptors
baroreceptors: located in the carotid sinus and in the aortic arch. they sense pressure changes by responding to change in the tension of the arterial wall
peripheral chemoreceptors: regulate respiratory activity and chemical environment of arterial blood (PO2, PCO2 and pH) within appropriate physiological ranges
mechanoreceptors/proprioreceptors: respond to changes in muscle length or tension
metaboreceptors: found in skeletal muscle respond to increased metabolic products and stimulate an increase in blood circulation in response to exercise
regulation of stroke volume
- end diastolic volume
- volume of blood in ventricles at end of diastole
-> alters the ventricular preload
- Frank Starling mechanism
-> normal, excessive fatigue, improved adaptation
-> greater EDV results in more forceful contraction - average aortic blood pressure
- pressure the heart must pump against to eject blood
-> alters ventricular afterload
- vasodilation
-> radius of vessel increases
-> resistance decreases
-> blood flow increases - strength of ventricular contraction
- alters the contraction
- increased SNS activity
end diastolic volume and venous return
venoconstriction vis SNS
skeletal muscle pump
-rhythmic skeletal muscle contraction force blood in extremities to heart
- prevention of back flow with veins
-> respiratory pump
-changes in thoracic pressures compress veins
