human phys exam 3

true or false: the A band length of a sarcomere will not change length during a contraction

false

true or false: the contractile protein myosin is important for the cross-bridge binding site to attach to during skeletal muscle contraction 

false 

the relaxation phase of skeletal muscle occurs due to ion movement by which of the following

increased reuptake by Ca+-ATP pump

the neural control over endocrine function occurs due to the input of the ___ to the ___

hypothalamus; posterior pituitary

acetylcholine will bind to ___ receptors in a region of cell bodies clustered together. it will bind to ___ receptors at an effector tissue

nicotinic; muscarinic

the ___ does not shorten during a skeletal muscle contraction

A-band

true or false: the biding of ATP to the crossbridge allows for the powerstroke to occur 

false 

true or false: the velocity of contraction in muscle is directly related to the force applied that opposes contraction

true

true or false: the latent period is a period in which there is a small amount of force generated, but not enough to be measured

false

from biggest to smallest, what are the components of the muscle

muscle belly, fascicle, muscle cell/fiber, myofibril, myofilament

during contraction, which part of the sarcomere is going to disappear or shorten

I band and H zone

during contractions, which part of the sarcomere is going to stay the same length

A band

from a neurological standpoint, if i wanted to lift a heavier weight what do i need to do 

activate more motor units (activates more fibers) 

if someone lacked ATPase in their muscles, wha would be the effect

they could not hydrolyze ATP to reorient the myosin head back to a position where it can perform the power stroke

T or F: myosin heads attach and pull on the actin as fast as they can and whenever they want

False, they need ATP and Ca2+ present

what would be the effect of a medication that binds to a troponin and turns off their receptors

Ca2+ would not be able to bind leading to no binding of the myosin head on the actin

a medication that binds nicotinic receptors at the muscle would do what 

prevent ACh from binding, resulting in no AP sent down the muscle 

if i were to cut a hole in the sarcoplasmic reticulum, what could happen

Ca2+ would flood into the muscle and may cause unwanted muscle contraction

the heart rate is normally initiated where

SA node

approximate value of a normal hematocrit

45

phase of the cardiac cycle when all 4 heart valves are closed and ventricular pressure is building but not yet high enough to open a valve

isovolumetric contraction

type of neuron that stimulates the contraction of skeletal muscle fibers 

motor neurons 

comparing type I and type IIx fibers

type IIx have a higher capacity for lactic acid production

protein that calcium binds to in smooth muscle to trigger contraction

T or F: during a quad extension, each motor unit that innervates the quads contains a large number of fibers

true

• course and powerful movements require motor units with many fibers

in large motor units each neuron controls many fibers 

the purpose is to generate high force, not fine movement 

muscle contraction requires large amounts of ATP during the first 10 seconds of a sprint, how are muscles meeting their ATP demand

through creatine phosphate donating a phosphate to ADP, making ATP

when ATP levels drop, phosphagen system releases ___ to catalyze the resythesises of ATP with creatine phosphate

creatine kinase

if someone wanted to burn the least amount of fat during an exercise, what kind of exercise would they perform

high intensity

low intensity: primary fuel

fat

high intensity: primary fuel

carbohydrates

which athlete would have the most mitochondria in their muscles?

marathon runner

slow-oxidative fibers 

• type 1 fibers 

• slow-twitch fibers 

endurance and continuous, low intensity activity 

• they produce ATP primarily through aerobic metabolism in the mitochondria 

T or F: when performing an explosive movement such as sprinting, we are only activating the motor units that contain fast-glycolytic fibers

false

• muscle fiber recruitment always starts with type 1 fibers and then moves to type 2 if needed

explain how myosin ATPase activity can influence fiber type

myosin ATPase activity determines how quickly a muscle fiber can contract. the more ATPase activity, the faster the myosin head is reoriented and can reattach to actin

high myosin ATPase activity = 

fast contraction

low myosin ATPase activity =

slow contraction

at mile 20 of a marathon, the runner feels like they can no longer keep running. at the muscular level why would the runner feel this way

internal acidity

• decrease in pH interferes with enzymes and Ca binding = slower and weaker contractions

glycogen depletion

• ATP availability drops = myosin heads can’t detach

reduced SR calcium release

• less Ca = fewer actin-myosin cross bridges

K+ accumulation

• decrease in membrane excitability = poor signal transmission

central fatigue

• decrease in motor neuron output = reduced muscle activation

what kind of neuron is sensing muscle stretch? is this pathway voluntary or involuntary?

an afferent neuron sends signals of stretch to the spinal cord from the muscle spindle an alpha motor neuron than sends a signal to the extrafusal muscle to contract this is involuntary

what would be the effect of inactivating myosin light chain kinase (MLCK) in smooth muscle

MLCK would not be able to phosphorylate myosin and result in myosin not being able to move tropomyosin if tropomyosin is not moved, the myosin head cannot bind to actin

how do golgi tendon organs prevent muscle damage 

sends inhibitory signal to the agonist muscle and an excitatory signal to the antagonist muscle

• example, during a bicep curl the agonist is the bicep and the the antagonist is the triceps 

if someone wanted to stop muscle contraction from a neurological standpoint, what would they do

block nicotinic receptors so the muscle cannot be excited by ACh

when someone lifts heavy weights, their muscles are going to hypertrophy. this is going to increase the cross-sectional area of their muscles. what does this cause? why?

allow that person to create more muscle tension

• this is because they now have more actin and myosin cross-bridges forming when their muscles are contracted

if an athlete is very explosive, what type of fibers may they contain a lot of 

fast glycolytic

what is the role of erythropoietin (EPO)? what could be a side effect of too much EPO?

EPO stimulates the bone marrow to produce RBCs. too much EPO can increase RBC concentration too much, leading to potential blood clots

where does most of the calcium come from during smooth muscle contraction

extracellular through voltage gated Ca channels

what allows the heart to contract as 1 functional unit

gap junctions, an AP that occurs anywhere in myocardium can stimulate all of the myocardium

what muscle fiber contains the least amount of mitochondria

fast glycolytic

what allows an AP to reach voltage gated Ca deep in muscle tissue

t-tubules

T or F: cardiac muscle requires myosin light chain kinase to phosphorylate myosin chains and move tropomyosin 

false 

• this is necessary in smooth muscle 

why do platelets not stick together during normal function

prostacyclin and nitric oxide prevent aggravation and cause vasodilation

someone is performing a max squat and as they are slowly standing up, they get stuck and cannot finish the lift. then suddenly it feels like their muscles give out and they fail the lift. what may have caused this

golgi tendons

what percentage of blood is RBCs? what may increase this number 

45%, dehydration or in athletes that train in altitude 

what would be the result if someone could not produce fibrinogen

they could not produce fibrin and ultimately not from blood clots

if someone took a medication that binds to nicotinic receptors, what would this medication do

relax skeletal muscle

what would be the effect of an enzyme that dephophorylated myosin heads

prevent contraction of smooth muscle

how does hypertrophy improve muscle contraction 

increases the cross-sectional area, which allows for more cross-bridges to be formed