what are the intrinsic and extrinsic factors that regulate heart rate during rest and exercise
- SA node (intrinsic)
- chemical messagers that are circulated through the blood to accelerate the heart before exercise begins and adjust once intensity increases (extrinsic)
what are the components of a normal ECG
- p wave: depolarization of both atria
- qrs complex: depolarization of the left ventricle
- t wave: repolarization of both ventricles
neural control
sympathetic nervous system increases the rate of blood flow and contractility through the AV node, Purkinje fibres and the septum
parasympathetic nervous system decreases the rate through the vagus nerve and the SA node which sets the resting heart rate
what is the central command
area of the brain that takes input from baroreflexes (from arteries near the heart), cardiopulmonary reflexes (in the heart), and exercise pressor reflexes (from the skeletal muscles) and the output is action from other areas of the body (such as inactiviation of certain muscles while others are working harder and need the blood there instead)
chemoreceptor
special nerve cells that sense changes in the chemical composition of the blood, monitor metabolites, and blood gases
mechanoreceptors
respond to mechanical pressure such as touch, or vibration from the external or internal environments
3 factors that affect blood flow resistance
- blood thickness
- length of conducting tube
- blood vessel radius
2 differences in blood flow dynamics to different tissues at exercise onset and during exercise
blood flow through arterioles and capillaries varies slightly as arterioles have smooth muscle which allows for them to dilate to allow for more blood to flow
effects of epinephrine and norepinephrine during sympathetic stimulation
cause frequency and force effects on the heart
norepinphrine acts as a vasoconstrictor
effects of acetycholine during parasympathetic stimulation
acetylcholine slows heart rate after sympathetic activity has occurred
volume of flow in a vessel relates to two factors
- directly to pressure gradient between two ends of the vessels
- inversely to resistance encountered to fluid flow
poiseuilles law
flow = pressure gradient x vessel radius / vessel length x fluid viscosity
- vessel length stays the same, blood viscosity changes very little, radius changes the most
what are the two factors that contribute to reduced blood flow to non-active tissues
- increased SNS outflow
- chemicals stimulate vasoconstriction
vasodilation is mediated by (7)
- temperature
- carbon dioxide
- nitric oxide
- magnesium
- pH
- adenosine
- potassium
what is nitric oxides role in blood flow
signal molecule that dilates vessels and decreases resistance to allow for easier flow to occur
