exercise physiology midterm 2 Flashcards
satellite cells
- undifferentiated cells that increase the number of nuclei in muscles which promotes growth and strengthening
- training activated
synaptic cleft
the gap between the motor neuron and the muscle cell that the AP crosses
ACh
acetylcholine
- neurotransmitter released to be diffused across synaptic cleft
neuromuscular junction (NMJ)
- when the nerve impulse reaches the endo f the motor nerve it comes to the synaptic cleft
- ACh in released and diffused across the cleft to bind to the recptor site on the mtor and plate
- opens sodium channels on the sarcolemma allowing sodium to diffuse into the muscle fiber
-results in depolarization called the end-plate potential (EPP)
-this is the signal to begin the contractile process
sliding filament thoery
- ATP binds to myosin head
- ATP causes cross bridges to “cock”
- cross bridges attach to myosin head
- bind to actin
- power stoke and slide
force regulations
- type and number of motor units recruited
- initial muscle length (length-tension relationship)
- nature of the neural stimulation (simple twitch, summation, tetanus)
- contractile history
size principle name
Henneman’s principle
Henneman’s size principle
MUs recruit from smallest to largest based on the force required
- first recruited is last to de-recruit
tetanus
sustained muscle contraction
what happens if previous activity is non-fatiguing
force production enhanced
- more sensitive to Ca
- phosphoralation of myosin light chain
skeletal muscle fibre types
- slow oxidative (type I)
- fast oxidative glycolytic (type IIa)
- fast glycolytic (type IIx)
influences of force type distribution
- genetics
-training - hormone concentration
biochemical properties of muscle fibres
- oxidative capacity (# of cappilaries, mitochondria, amount of myoglobin)
- speed of ATP degragation
- absence of contractile proteins
contractile properties of muscle fibres
- maximal force produced
- speed of contraction
- maximum power output
- muscle fibre efficiency
immunohistochemical staining
straining of a muscle biopsy in order to see the amount of fast vs slow twitch fibres in the muscle
immunohistochemical staining colours
- blue = type I fibres
- green = IIa fibres
- Black IIx fibres
- red = dystrophin (protein in sarcolemma)
causes of fatigue
- CV system (O2)
- energy supply system (inadequate ATP)
- neuromuscular system
- thermoregulation
- biochemical (stresses in other systems)
- psychology
-central governor model (prevent catastrophic failure by homeostasis)
central causes of fatigue
- motor cortex (pain)
- spinal cord (impaired recruitment of MN and firing frequency)
peripheral causes of fatigue
- NMJ (impaired neuromuscular transmission)
- impaired conduction of action potentials
- Ca2+ (impaired release
- imparied cross bridge cycling (myosin and actin
- low force/power output
two hypothesis of peripheral fatigue
- accumulation hypothesis (lactic acid, H+, Ca, Pi, etc)
- depletion hypothesis (ACh, glycogen, BG, O2, etc)
accumulation of too much potassium (K)
- can block nerve transmission to T-tubules
purpose of cardiovascular system
- transport O2
- removal of CO2
- regulation of temp
two major adjustments of the CV system during exercise
- increased cardiac output
- redistribution
cardiac output equation
Q = HR x SV
blood flow equation
change in pressure / resistance
resting heart rate (RHR)
- normal (60-8b5pm)
- elite (28-40 bpm)
typical heart rate timing
distole - 0.5 sec
systole - 0.3 sec
elite heart rate timing
distole - 0.13 sec
systole - 0.2 sec
why does heart rate increase with exercise
initially increases abruptly with the withdrawal of PNS
- SNS kicks in and HR continues to rise
max heart rate equations
220 - age
or
208 - (0.7 x age)
heart rate variability
wide variety of HRV is considered healthy
stroke volume
(end dystolic volume - end systolic volume
stroke volume is determined by
- end -diastolic volume
- vascular resistance
- contractibility
frank-starling law
the heart adjusts its stroke colume and cardiac output in response to changes in venous return and end diastolic volume
veinous return
amount of blood returned to the heart
three principles of EDV
- venoconstriction
-muscle pump - respiratory pump