Exam 2 Flashcards
What percent of total body weight do skeletal muscles make up
40-50%
What is the origin of the muscle
The end of the muscle attached to bone that does not move
What is the insertion of the muscle
The end of the muscle fixed to a bone that moves during muscular contraction
What is unique about muscle cell organelles
One muscle cells can have mulitiple nuclei
Where are subsarcolemmal (SS) mitochondria loacted
Directly beneath the sarcolemma (cell membrane)
What do subsarcolemmal (SS) mitochondria do
Provide cellular energy needed to mainatain active transport of ions across the sarcolemma (e.g. power the Na/K pump)
Where are intermyofibrillar (IMF) mitochondria located
Near the myofribillar/contractile proteins
What do intermyofibrillar (IMF) mitochondria do
Provide energy for muscle contraction
What do satellite cells in muscle tissues do
Aid in muscle growh and repair by increasing the number of nuclei
Why is retraining easier than training
Because satellite cells take longer to degrade than sarcomeres and they increase the number of nuclei, making it easier to recover
What are 3 functions of skeletal muscle
Force production for locomotion and breathing, force production for postural support, and heat production during cold stress
How do muscles act as endocrine glands
They secrete myokines, IL-6, and promote an anti-inflammatory environment resulting from regular exercise
What do myokines do
Stimulate glucose uptake and fatty acid oxidation, promote blood vessel growth in muscle, and promote liver glucose production and triglyceride breakdown
Is IL-6 pro or anti-inflammatory
It can be both but during exercise it is anti-inflammatory
What are some anti-inflammatory benefits of regular exercise
Reduction in chronic inflammation and reduced risk of heart disease, type 2 diabetes, and certain cancers
Are concentric or eccentric movements associated with muscle fiber injury, soreness, and subsequently growth
Eccentric
What is the motor end plate
The pocket formed around motor neurons by folded sarcolemma
What is the Z line also known as
The Z disk
What is the M line
In the middle of both sides of thick filaments
What is the I band (light zone)
The spacing between myosin (Z line in the middle)
What is the A band (dark zone)
The length of myosin
What is the H zone (middle of A band)
Space between thin filaments that gets reduced during contraction
Which structures of the sarcomere experience decreased width during contraction
H-zone and I-band
What are muscle cramps
Spasmodic, involuntary muscle contractions often associated with prolonged, high intensity exercise
What is the electrolyte depletion and dehydration theory
That water and sodium loss from sweating causes muscle cramps (more likely in a hot environment)
Why is the electrolyte depletion and dehydration theory not well supported
Because there is no differences between cramping in severely dehydrated vs. hydrated individuals or in those with electrolyte imbalances. Also cramping is localized while electrolyte loss and dehydration are not
What is the altered neuromuscular control theory
That abnormal spinal reflex results in increased excitatory activation of muscle spindles and reduced inhibition of the Golgi tendon organ, leading to muscle cramp
What do muscle spindles do
Detect stretch in muscle and cause contraction to resist stretch
What do Golgi tendon organs do
Detect tension in tendons and inhibit alpha motor neurons so that muscles can relax to relieve tension
How can muscle cramping be relieved
Via passive stretching which will activate the Golgi tendon organ or ginger and capsaicin
How do ginger and capsaicin help with muscle cramping
They activate TRP channels that inhibit the signal to the spinal cord so that overactive motor neurons can be inhibited
What is the primary pathway for ATP synthesis in each muscle fiber type
Type I: Aerobic
Type IIa: Combination
Type IIx: Anaerobic
What is the myoglobin content/number of in each muscle fiber type
Type I: High
Type IIa: Intermediate
Type IIx: Low
What are glycogen stores like in each muscle fiber type
Type I: Low
Type IIa: Intermediate
Type IIx: High
What is the speed of contraction in each muscle fiber type
Type I: Slow
Type IIa: Fast
Type IIx: Fastest
What is the maximal force production and power output in each muscle fiber type
Type I: Moderate
Type IIa: High
Type IIx: Highest
What is the rate of fatigue of each muscle fiber type
Type I: Slow
Type IIa: Intermediate
Type IIx: Fast
What is the type of motor unit innervating each muscle type
Type I: Slow (S)
Type IIa: Fast Fatigue Resistant (FR)
Type IIx: Fast Fatigable (FF)
What is the recruitment order of each muscle type
Type I first, then IIa, then IIx
What type of activities are type I fibers best suited for
Endurance
What type of activities are type IIa and IIx fibers best suited for
Power-type
Which muscle type can generate the most power
Type IIb but it isn’t really expressed in humans despite mRNA expression during intense exercise
What are the characteristics of type I fibers
They are slow twitch and slow-oxidative
What are the characteristics of type IIa fibers
They are intermediate and fast-oxidative fibers
What are the characteristics of type Iix fibers
They are fast-twitch, fast-glycolytic fibers
How do muscle fiber types generate different speeds
Based on what isoform of ATPase they have and how quickly they can release Ca++ from the SR
Why do larger muscle fibers produce more force than smaller muscle fibers
Because they contain more actin and myosin
How does force production vary between men and women
Men are significantly stronger than women in terms of absolute and relative force production despite no apparent sex or age differences in fiber distribution perhaps because men have significantly skeletal muscle mass
What is the equation for power generated by a muscle fiber
Force * Shortening velocity
How does muscle fiber efficiency (lower amount of ATP to generate force) vary between muscel fiber types
Type I: Low
Type IIa: Moderate
Type IIx: High
What percent of variation in VO2max can be explained by percentage of type I fibers between individuals
40%
What are the smallest and largest motor neurons
Type S is smallest and type FF is largest
What is the size principle
Progressive recruitment of motor units starts with smallest units and then progresses to larger and larger motor neurons
What are the 4 phases of a muscle twitch
Stimulus, latent period, contraction, and relaxation
Why is force production in muscles additive with increased stimulus frequency
Because not all of the Ca++ is sequestered back to the SR, increasing it’s availability once more is released
What is DOMS
Delayed onset muscle soreness
What causes DOMS
Microscopic tears in muscle fibers or connective tissue (more likely during eccentric exercise)
What are the 7 steps in DOMS
1) Strenous exercise causes structural damage to muscle fibers
2) Membrane damage
3) Ca++ leaks out of SR
4) Immune-induced apoptosis compounds initial damage by activating proteases
5) Inflammatory response happening throughout
6) Edema and pain
7) Satellite cells repair damages
What are consequences of DOMS
E-C coupling failure, contractile protein loss (due to immune system), and physical disruption
Why can creatine kinase (CK) and myoglobin levels spike ~ 4 days after exercise
Due to rupture of muscles where they once resided
Why do subsequent bouts of exercise not cause the same response as DOMS
Because of adaptation in nervous system, connective tissue, and cells themselves
What are 3 purposes of the cardiorespiratory system
To transport O2 and nutrients to tissues, remove CO2 wastes from tissues, and regulate body temperature
How does blood flow change during exercise
Cardiac output increases and blood flow is redirected from inactive organs to active muscle (thermoregulation)
Where is the Tricuspid valve
It is separating the right atrium from the right ventricle
Where is the mitral valve
It is separating the left atrium from the left ventricle
Where is the pulmonary semilunar valve
It separates the right ventricle from the pulmonary artery
Where is the aortic semilunar valve
It is separating the left ventricle from the aorta
Which side of the heart pumps oxygenated blood
The left side
What is hematocrit
The percentage of blood composed of packed RBCs
What is average hematocrit of college-aged individuals
42% for males and 38% for females
What effect would a change in hematocrit have
It would change blood viscosity and flow
What is the equation for blood flow
Blood flow = Change in pressure / Resistance (viscosity, length, and r^4)
What is pressure proportional too in hemodynamics
The difference between MAP and right atrial pressure
What are the characteristics of diastole
Pressure in the ventricles is low while pressure in the atria is high, causing mitral and tricuspid valves to open and fill the ventricles with blood
What are the characteristics of systole
Pressure in the ventricles rises until it forces aortic and pulmonary (semilunar) valves open to eject blood into pulmonary and systemic circulation
How does the ratio of diastole compare to systole at rest vs. during exercise
At rest, diastole is longer than systole (2/3 : 1/3) but at exercise both is shorter and they are about equal
What is end diastolic volume (EDV) also known as
Pre-load
What is after load
Average aortic BP/MAP that the ventricles must pump against to eject blood
What nerve does the parasympathetic nervous system use to innervate the heart
The vagus nerve
What nerves does the sympathetic nervous system use to innervate the heart
The sympathetic cardiac nerve and cardiac accelerator nerves
How does the PSNS slow down HR
By releasing ACh onto muscarinic cholinergic (mAch) receptors to block calcium from coming into autorhythmic cells and effectively inhibiting the SA and AV nodes
How does the SNS speed up HR
It releases catecholamines that stimulate b1-ADR on autorhythmic cells which use cAMP pathway to open Funny channels and T-type calcium channels to excite SA and AV nodes
What causes the increase in HR during exercise
Initially it is due to parasympathetic withdrawal (1st 40% intensity), then due to increased SNS outflow
How can a change in body temperature influence HR during exercise
Vasodilation to periphery to cool down the body can decrease BP that body tries to overcome by increasing HR
What is heart rate variability (HRV)
The variation in time between heart beats (measured at R-R time interval) with wide variation indicating “healthy” balance between SNS and PNS
Why does low HRV indicate an imabalance in autonomic regulation
It means there is more influence from the SNS because the SNS controls HR
What diseases are known to decrease HRV
Depression, hypertension, heart disease (including myocardial infarction), and physical inactivity
What is the Frank-Starling mechanism
Greater EDV results in a more forceful contraction (because more blood comes around to the heart and stretches ventricles) which is dependent on venous return
What 3 things increase venous return
Venoconstriction via SNS, skeletal muscle pump, and respiratory muscle pump
How does the skeletal muscle pump work
Veins have one way valves that prevent backflow so rhythmic muscle contractions increases pressure in the section to push blood up and towards the heart
How does the respiratory pump work
Changes in thoracic pressure pull blood towards the heart
What two factors affect the filling time of the ventricles
Heart rate and body position (takes longer when standing than laying down)
Howa are afterload and end-systolic volume (ESV) related
They are directly related (decreasing afterload decreases ESV which increases SV)
How is stroke volume regulated
EDV, afterload, and strength of ventricular contractility (inotropy)
How are inotropy and ESV related
They are inversely related (increases in contractility decrease ESV because you’re squeezing everything out)
How much greater is oxygen demand in the muscles during exercises compared to rest
15-25x
What two ways can O2 delivery be increased
Increased Q or redistribution of blood flow
Do changes in VO2max result from increased HR or SV
Initially (40-60%), changes result from boht HR and SV, but above that results from increased HR
What is the calculation for max HR
208 - 0.7*age
What happens to SV in untrained subjects as a result of exercise
Due to high HR, fill time decreases, leading to decreased EDV and thus decreased SV
What percent of Q goes to muscle during rest vs exercise
At rest, 15-20%, then increases so 80-85% during maximal exercise
How is muscle blood flow primarily mediated during exercise
By local factors (autoregulation) like metabolites (e.g. NO, prostaglandins, ATP, adenosine, and endothelium-derived hyperpolarization factors) which promote vasodilation to increase flow to working muscles
What is the Fick Eqation
VO2 = Q x a-vO2 difference
How does arteriovenous difference change during exercise
It increases due to higher O2 uptake in tissues (used for oxidative ATP production)
What impact do emotions have on the circulatory response to exercise
In emotionally charged environement, BP and HR increase due to SNS activity which can increase pre-exercise HR and BP but doens’t impact peak HR or BP during exercise
What is the circulatory response at the onset of exercise
Rapid increase in HR, SV, and Q until a plateau is reached in submaximal (below lactate threshold) exercise
What is the circulatory response to graded exercise
HR and Q increase linearly with increasing work rate until they plateau at 100% VO2 max, and MAP increases linearly (sBP increases while dBP remains pretty constant)
What is the circulatory response to arm vs leg exercise
At same VO2, arm work results in higehr BP (due to vasoconstriction of large inactive muscle mass), and HR (SNS stimulation)
What 3 things does the recovery of HR and BP between bouts of intermittent exercise depend on
Fitness level, temp and humidity, and duration and intensity
What is the circulatory response to prolonged exercise
Q is stable, gradual decrease in SV (due to dehydration and reduced plasma V), and gradual increase in HR especially in heat (because of cardiovascular drift)
What is the circulatory response to recovery
Decrease in HR, SV, and Q towards resting depending on duration and intensity of exercise and training of the subject
What is pulmonary respiration
Exchange of O2 and CO2 in the lungs resulting from ventilation (breathing)
What is circulatory respiration
O2 utilization and CO2 production by the tissues
What are the 2 purposes of the respiratory system during exercise
Gas exchange between the environment and the body and regulation of acid-base balance
How does ventilation (movement of air) occur
Via bulk flow (movement of molecules due to pressure difference)
What is the pressure difference during inspiration
Negative Presssure (Intrapulmonary pressure < Atmospheric pressure due to diaphragm pushing downward and lifting ribs outward)
What is the pressure difference during expiration
Positive pressure (Intrapulmonary pressure > Atmospheric pressure due to diaphragm relaxing and pulling ribs down)
What is pulmonary ventilation/minute ventilation (Ve)
The amount of air moved in or out of the lungs per min (L/min)
What is tidal volume (Vt)
The amount of air moved per breath (L/breath)
What is the equation for minute ventilation
Ve = Vt * f
What is the anatomical dead space during pulmonary ventilation
The space from the bottom of the trachea to the top of the nasopharynx where no gas exchange is occuring (why hyperventilation is inefficient)
What is the average pulmonary ventilation at rest vs during max exercise
Rest = 7.5 L/min
Max exercise = 120-175 L/min
What is average breathing frequency at rest vs during max exercise
Rest = 15 breaths/min
Max exercise = 40-50 breaths/min
What is average tidal volume at rest vs during max exercise
Rest = 0.5 L/breath
Max exercise = 3-3.5 L/breath
What changes in breathing pattern occur during exercise
In the beginning there are changes in both frequency and tidal volume, but in more extreme changes (e.g between 70% - 100% intensity), almost all changes result from frequency
How is ventilation at rest controlled
Via somatic motor neurons in the spinal cord and the respiratory control center in the medulla oblongata
What are the 2 inputs to the respiratory control center
Neural input from motor cortex and skeletal muscle mechanoreceptors (muscle spindles, Golgi tendon organs, and joint pressure receptors), and humoral chemoreceptors
Where are central chemoreceptors located
In the medulla
What do central chemoreceptors detect
Changes in PCO2 and H+ concentration in CSF
Where are peripheral chemoreceptors located
Aortic and carotid bodies
What do peripheral chemoreceptors detect
Changes in PO2, PCO2, H+, and K+ in the blood
Does the respiratory control center respond to changes in PCO2 or PO2 first
Usually PCO2 (why holding one’s breath makes them need to breathe), but changes to PO2 if at elevation
What primarily controls ventilation during submaximal exercise
Neural input
What primarily controls ventilation during maximal exercise
Humoral input
How does blood flow to the lung during upright resting conditions
Most blood flows to the base of the lung due to gravity
How does blood flow to the lung during upright exercise
Blood flow increases to the top (apex) of the lung
What is PO2 and PCO2 in the alveoli/arteries
PO2 = 104 mmHg
PCO2 = 40 mmHg
What is PO2 and PCO2 in the tissues/veins
PO2 = 40 mmHg
PCO2 = 46 mmHg
What kind of blood flows through the pulmonary artery
Mixed venous blood
What kind of blood flows through the pulmonary vein
Oxygenated blood
What does the ventilaition/perfusion ratio (V/Q) indicate
Matching blood flow to ventilation (ideal is 1 or more if blood flow is high)
What causes exercise-induced asthma (bronchoconstriction)
Contraction of smooth muscles around the airways (brochospasms) and mucus in the airways during or after exercise causing labored breathing (dyspnea) and wheezing
If V/Q is < 1, what local control occurs
Pulmonary arterioles constrict to reduce perfusion to match reduced ventilation
If V/Q is > 1, what local control occurs
Pulmonary arterioles dilate to increase perfusion to match increased ventilation
How is V/Q impacted by exercise
Low/moderate intensity improves V/Q while high intensity results in slight V/Q inequality
What is pulmonary capillary transit time
Essentially there needs to be enough time for O2 binding sites to be saturated, so if blood flow increases too much, there will not be enough time to saturate these sites
How does O2 travel in the blood
99% travels bound to Hb, the other 1% is just dissolved in plasma
What 3 factors influence the amount of O2 that can be transported per unit volume of blood
[Hb], arterial oxygen saturation, and amount of O2 dissolved in plasma (minor contribution)
What is the PO2 in the mitochondria of muscles
About 1-3
Why does decreased pH favor O2 offloading to tissues
Because H+ ions bind hemoglobin, reducing it’s O2 transport capacity
Why does increased temp favor O2 offloading to tissues
Because increased temp affects protein folding and weakens the bond between O2 and hemoglobin
Is 2-3 DPG a major cause of rightward shift during exercise
No, it is only really a main factor during altitude exposure
Why do RBCs undergo glycolysis and make so much 2-3 DPG
Because they have no mitochondria to undergo aerobic ATP production
What is resting temp and pH in the body
37°C and pH of 7.4
How is the a-v O2 difference affected by exercise
It increases because the muscles are using more O2, decreasing the venous O2
What do myoglobin do when the muscle is at rest
They act almost as an O2 reserve because they are close to saturated
How do myoglobin influence O2 debt (EPOC)
After exercising stops, myglobin O2 must be replenished and this O2 consumption above resting values contributes to EPOC
How is CO2 transported in the blood
10% dissolved in plasma, 20% bound to hemoglobin (forms carbaminohemoglobin), and 70% as bicarb (HCO3-)
How does CO2 primarily get from tissues into the blood
It is transported into RBCs where it combines with water to form carbonic acid that then dissociates further into bicarbonate and H+ (H+ combines with the hemoglobin), and the bicarb is transported into the plasma using the chloride shift
How is CO2 primarily transported from the blood into the lung
Bicarb enters RBCs using chloride shift, then combines with H+ to form carbonic acid, then dissociates into CO2 and H20 where CO2 simply diffuses out into the alveoli
Why does ventilation increase during exercise
Muscles undergo lots of aerobic ATP production, producing CO2 and H+, the lungs remove H+ by increasing ventilation to remove CO2 and force the bicarb reaction left
What are the characteristics of ventilation and partial pressures of gases at the onset of submaximal, steady state exercise
PO2 and PCO2 are relatively unchanged while ventilation initially increases rapidly but then rises slowly until steady state
What are the characteristics of ventilation and partial pressures of gases during prolonged exercise in a hot environment
There is little change in PCO2 and ventilation tends to drift upward because increased blood temp affects respiratory control center (breathing frequency increases but tidal volume doesn’t change which is why gas exchange of CO2 doesn’t change)
Is the pulmonary system seen as a limitation during submaximal exercise in untrained subjects
No
Does arterial PO2 change during graded exercise in untrained individuals
No, it remains within 10-12 mmHg of it’s resting value
Is the pulmonary system seen as a limitation during maximal exercise in highly trained elite endurance athletes
It can be limiting because of mechanical limitations, respiratory muscle fatigue during prolonged (>120 min) high intensity (90-100%) exercise, causing 40-50% to experience exercise-induced arterial hypoxemia (EIAH)
What causes exercise-induced arterial hypoxemia (EIAH)
Decreased pulmonary capillary transit time and right shift in O2-Hb dissociation curve due to decreased pH that lungs can’t overcome reduces arterial PO2 in highly trained elite endurance athletes during maximal exercise
What 3 factors does H+ production depend on
Exercise intensity, amount of muscle mass involved, and duration of exercise
What are sources of H+ ions in skeletal muscle
ATP breakdown, aerobic metabolism which creats carbonic acid, and anaerobic metabolism which creates lactate
How is CO2 produced in skeletal muscles
It is the end of oxidative phosphorylation (made in Krebs Cycle)
What are 2 main ways increased [H+] can impair performance
It inhibits enzymes in aerobic and anaerobic ATP production (specifically PFK in glycolysis), and it can impair muscle contraction by competing wiht Ca++ for binding sites on troponin
How do buffers maintain acid-base balance
They release H+ when pH is high and accept H+ when pH is low
What is the first line of defence against muscle pH shift during exercise
Cellular buffer systems
What is the second line of defence against muscle pH shift during exercise
Blood buffer systems
What are the 5 cellular buffer systems
Bicarbonate, phosphates, protiens, carnosine (60%), and transport of H+ out of the muscle
What are the 3 blood buffer systems
Bicarbonate, phosphates, and proteins
What is NHE
A sodium/hydrogen exchanger that brings sodium into skeletal muscle with it’s gradient and pushes H+ out
What is MCT
Monocarboxylate transporter that pushes lactate and H+ out of skeletal muscle
Which muscle fibers have higher buffering capacity
Fast (type 2)
How does high intensity exercise training improve muscle buffering capacity
By increasing carnosine and H+ ion transporters (HNE and MCT) in trained muscle fibers
What 6 things cause Tvent
Increasing blood PCO2 and H+ as well as increases in blood K+, rising body temp, elevated blood catecholamines, and possible neural influences
How do we know lactate threshold is separate from ventilatory threshold
McArdle’s pts still experience Tvent
How does graded exercise affect Arterial PO2 in untrained subjects
It doens’t really, PO2a is mainted within 10-12 mmHg of resting value
How does graded exercise affect Arterial PCO2 in untrained subjects
It slightly decreases with maximal exercise
How does graded exercise affect Arterial pH in untrained subjects
It decreases with maximal exercise because bicarb gets saturated and ventilation can’t fully compensate for H+ accumulation
How does graded exercise affect ventilation in untrained subjects
There is a linear increase up to 50-75% VO2 max and then an exponsntial rise (hyperventilation during recovery intervals attenuates performance decrements)
Why might ingesting buffer help with performance in untrained subjects during graded exercise
It can help attenuate drop in arterial pH because while straight bicarb might cause alkalosis, beta-alanine (carnosine precursor) improves the cellular buffer system rather than blood buffering system
How do kidneys regualte acid-base balance during rest
When pH decreases, bicarb excretion is reduced and when pH increases, bicarb excretion is increased
How is lactate removed after exercise
70% of lactic acid (H+ acceptor) is oxidized to pyruvate and used as a substrate by heart and skeletal muscle, 20% is converted to glucose (Cori cycle), and 10% is converted to amino acids
Why is lactic acid removed more rapidly with light exercise in recovery (30-40% VO2max)
Because there is increased blood flow to the liver, etc. without producing too much more lactate
How can lactic acid be removed quicker following exercise without continuing light exercise
Compression wear improves recovery my mimicking skeletal muscle pump
