Chapter 16 Flashcards
what is the myogenic response? **
a reflex constriction of smooth muscle after an increase of vascular pressure
OR
a dilation of smooth muscle after a decrease of vascular pressure
what is another name for the sinoatrial (SA) node?
heart’s pacemaker
why is there a delay that occurs is sending impulses? *
a 0.10 s delay occurs to allow atria to contract and propel blood into ventricles
is parasympathetic or sympathetic transmission faster at rest? what is the benefit of having faster transmission?
parasympathetic
has greater influence on variability because it can communicate faster
what influences heart rate and variability between heart beats?
the parasympathetic nervous system since acetyl coline has faster transmission than epinephrine and norepinephrine
what is the function of the AV bundle (bundle of His)?
transmits impulse to the purkinje system that penetrates the right and left ventricles
how is the heart’s output of blood and the blood’s distribution regulated?
input from the brain (desire/anticipation) and the peripheral nervous system (meta/mechano-reflex) send signals to the control centre in the ventrolateral medulla
what are baroreceptors? how do they function?
stretch receptors in the arteriole walls
when there is a large stretch, a lot of pressure, baroreceptors signal to delay the next heart beat to reduce the pressure
what does the mechanic reflex control?
force and tension
what are chronotropic effects? *
rate and rhythm of the heart
effects electrical conduction
what are inotropic effects? *
force of contraction
when the sympathetic cardioaccelerator nerves are stimulated, what hormones are released?
epinephrine and norepinephrine
how does heart rate increase at start and during low/moderate intensity exercise? give an example *
inhibition of parasympathetic stimulation
example) anticipation
how does heart rate increase during strenuous exercise? give an example *
additional parasympathetic inhibition
direct activation of sympathetic cardioaccelerator nerves
example) peripheral afferent feedback
how does bradycardia happen?
stimulation of vagus nerve from medulla’s cardioinhibitory centre
what is the function of acetylcholine?
delays the rate of sinus discharge to slow heart rate (depolarization)
which nervous system do endurance runners want to be using?
their vagus/parasympathetic nervous system so they don’t get tired
what has the greatest control over heart rate from rest to moderate exercise?
central command system
does emotional state affect heart rate and blood pressure values? *
central command in cardiovascular regulation explains how emotional state can affect cardiovascular response making it difficult to obtain “true” resting values for heart rate and blood pressure
what are 3 mechanisms that can assess the nature and intensity of exercise and muscle mass activated?
- reflex neural input, size and strength of contraction
- chemical stimulation (CO2 and acidity in muscled)
- feed-forward outflow (DESIRE)
where are baroreceptors located? why?
aortic arch to assess how the heart is doing because blood is going directly to there
carotid sinus because it leads blood to the brain
what are 2 factors that relate to the volume of flow in a blood vessel?
- directly to pressure gradient between two ends of the vessels
- inversely to resistance encountered to fluid flow
what is a stimulus for angiogenesis? *
friction between blood and internal vascular wall creating resistance that affects blood flow
what are 3 factors that determine blood resistance? *
- blood thickness
- length of conducting tube
- blood vessel radius
what are 2 factors that contribute to reduced blood flow to non-active tissues?
- increases sympathetic nervous system outflow (fight or flight)
- local chemicals that stimulate vasoconstriction or enhance effects of vasoconstrictors
what are 3 things that happen when dormant capillaries open during exercise?
- increase in total muscle blood flow (increasing O2 and glucose)
- large blood volume is delivered with minimal increase in blood flow velocity
- increases effective surface for gas and nutrient exchange
what is the function of nitric oxide?
dilates blood vessels and decreases vascular resistance
what stimulates nitric oxide synthesis?
stimuli from chemicals, sheering stress and vessel stretch from increased blood flow through the vessel lumen
what are limitations to exercise for cardiac transplant patients?
adaptations have no meaningful effect on sub maximal or peak VO2
