30 - Exercise Physiology I Flashcards
the essence of exercise is ________ not _____
physical activity NOT intent
activity characterized by recurrent and substantial body movement
dynamic exercise
muscle generates constant tension while changing length
isotonic contraction
activity characterized by muscular contraction without substantial body movement
static exercise
muscle generates tension without a change in length
isometric contraction
concentric v. eccentric isotonic contraction
concentric - shortening muscle
eccentric - lengthening muscle
blood flow to exercising muscle increases _______ to exercise intensity
in proportion to
________ blood flow are reduced to the greatest extent
splanchnic and renal
skeletal muscle pump
contracting muscles squeeze the veins and push blood back to the heart
respiratory pump
during inspiration, pressure drops and increases venous return (gradient)
opposite with expiration
thinly myelinated
sensitive to mechanical deformation
group III muscle afferent
unmyelinated
metabolic byproducts associated with muscle contraction
group IV muscle afferents
afferent projections synapse in the ______ and exert significant influence on __ and ____ respiratory function
nucleus of solitary tract
autonomic and respiratory function
sympathetic n. activity _______ progressively with increasing exercise intensity —>
increases
–> increased arterial pressure, direct blood flow away from low-metabolically active tissue, venous return, and neurohumoral activation
two phases of blood flow response to exercise
- Initial increase: mechanical compression induced vasodilation and muscle pump
- steady state exercise: vasodialtion in arterioles induced by metabolic substances (adenosine, K+, CO2, H+)
_______ portion of the vascular tree most sensitive to metabolic vasodilators
terminal arterioles
- dilation of the terminal arterioles leads to recruitment of additional capillary networks
___________: decreasing affinity of Hgb for O2 and ___ shifting the oxyhemoglobin dissociation curve
Bohr effect
right shift
–> more oxygen can be off-loaded at the muscle
cardiovascular responses to exercise = _ preload _ contractility _ HR _ vascular resistance _ SV _ CO _ BP
all increase except vascular resistance
Increases in ventilation are well-matched to metabolic demands during ________ exercise. During ______, ventialtion and PaCO2 become uncoupled.
submaximal ; high intensity
–> CO2 levels decline in high intensity exercise
What mechanisms work to match ventilation and CO2 production? 1. Co2 flow to lung sensed with receptors 2. Central Command for conscious control 3. Mechano/metaboreceptors blocking III/IV afferents to reduce respiration
in isometric exercises, BP ________ than in isotonic exercise
increases much more
why? 1. m. contraction compresses arteries, increasing resistance
Also observe… higher levels of central command and increased intra-abdmonal and intra-thoracic pressure
Phases of Valsava Maneuver
I: increase intra-throacic pressure and compress aorta, veins, and heart. Reflex decrease in HR.
II: falling aortic pressure secondary to reduced CO. Reflex increase in HR.
III (done w/ maneuver): decreased compression of aorta.
IV: increased preload/cardiac filling/CO
anticipate the metabolic demand associated with exercise and prevent significant perturbation to blood gas homeostasis and tissue oxygen supply
feed-forward mechanisms
as exercise continues to increase in duration and intensity, _________ is thought to play a greater role
sympathetic activation
what is though to account for the majority of early ehart rate response to exercise?
withdrawl of vagal tone
