LEC EXAM #3 CHP 9 Flashcards
6 functions of skeletal muscle:
- skeletal movement
- store nutrient reserves
- support soft tissues
- guard openings
- body temperature
- body position
Myoglobin is specific to:
Skeletal and cardiac muscle tissues
Myoglobin binds:
Oxygen
What is a power stroke?
Movement of myosin cross bridges pushes actin towards center of sarcomere
What does the end of a power stroke consist of?
Myosin releases bound actin and grabs another actin molecule
Skeletal muscle stores:
Glycogen
Striations have:
Contractile fibers
When muscle tissues are damaged they release:
Myoglobin into blood and lactate dehydrogenase
Dark line:
Light line:
Myosin
Actin
Myoglobin has a higher affinity for:
O2
Skeletal muscle structure:
Repeating circular bundles
What is tennis elbow?
Makes sheaths flat instead of round
What is stored at the sarcoplasmic reticulum?
Calcium
Z line connects/anchors:
Actin (always thin)
Space where there is ONLY actin:
I band
Space where actin and myosin overlap:
A band
M line anchors:
Myosin (always thick)
Space where there is ONLY myosin:
H band
Sheath like protein that covers binding site:
Tropomyosin
Beaded complex where calcium binds:
Troponin
ATPase is where:
ATP binds to get myosin head activated
What are the steps of contraction?
- AP in t-tubule alters DHP receptor
- DHP receptor causes calcium to bind to troponin
- Moves tropomyosin out of the way for myosin to bind to actin
Why do we need calcium?
To move tropomyosin
Neuromuscular junction:
Regulates force
Axon contains:
Na V.G.C.
The nerve synapses with the skeletal muscle at the:
Motor end plate
Acetylcholesterase:
An enzyme that breaks down acetyl–coa
The holes of the t-tubule take it deep into the:
Skeletal muscle
Relaxation steps:
ATP pulls apart actin and myosin cross bridge
ATP splits into ADP and phosphate
Activates head for power stroke
ADP and phosphate leave
What stops skeletal muscle contraction?
Nerve by nerve impulse shutting off -> no more acetyl-coa
What regulates skeletal muscle?
Somatic nervous system
Relaxation begins in the:
Brain
Relaxation requires:
Contraction requires:
ATP
Calcium and ATP
Rigor mortis:
Stiffness of muscles after death for 72 hours, caused by lack of ATP
TEA:
- Blocks potassium voltage gated channels
- K+ cannot repolarize via K+ v.g.c.
- long drawn out repolarzation-> hyper-excitable (above 55)
Curare:
- Blocks nicotinic cholinergic receptors
- no nerve->nerve conduction
- no nerve-> skeletal muscle conduction
Esterine/physostigmine:
- blocks Acetylcholesterase (AchE)
- Ach stays in synapse
- continued contraction
Organophosphates (never toxins):
- blocks AchE
- causes continuous contraction
Myasthenia gravis:
- autoimmune disease
- antibodies attack nicotinic cholinergic receptors
- no AP/ no skeletal muscle contraction
- use eserine to increase Ach in the synapse
What allows action potentials to go deep into where contractile fibers are? (nerve-> skeletal muscle)
T-tubules
What floods into the area where the contractile fibers are, causing excitement of skeletal muscle?
Calcium
Once calcium floods the area where the contractile fibers are, where the actin and myosin are, what does calcium bind to?
Troponin
Calcium then moves:
Tropomyosin away from the actin
What ion or molecule do we have to have to move tropomyosin?
Calcium
Myosin is now bound to actin, what causes the power stroke/contraction?
- Phosphate leaves
- get power stroke
- then ADP leaves
- stuck here until ATP binds
ATP releases:
crossbridge
ATP will bind if:
Calcium is present
REQUIRED for contraction/power stroke:
ATP and calcium
What ion causes the vesicle to dump into the synapse?
Calcium
Curare does not effect:
nerve -> heart
nerve -> digestive tract
If curare is stuck here, what cannot bind?
Ach
Threshold stimulus:
Strength of stimulus required to cause a twitch
Latent period:
Delay between stimulus and contraction
Twitch:
Single, brief contraction of a muscle fiber after a single threshold stimulus
Relaxation is caused by:
Transport of calcium back into the sarcoplasmic reticulum
What is the “all or none” principle?
At threshold, a fiber will contract its maximum extent
Tension of a single muscle fiber depends on:
- fiber’s resting length at time of stimulation
- frequency of stimulation
- number of pivoting cross bridges
Skeletal muscles are capable of:
graded responses
The force of muscle contraction can increase by:
Summation or recruitment
Refractory period:
time between initial and subsequent stimuli that is required for sarcolemma to repolarize
Summation:
Greater force generated from more frequent stimuli
Tetanic contraction:
- Continuous contraction without relaxation between stimuli
- all motor units of muscle are activated
Fatigue:
Loss of response due to lack of ATP
Motor unit:
Motor neuron + all the fibers it controls
Motor unit rule:
All muscle cells in a motor unit respond maximally, or they don’t respond at all
Each motor neuron on average controls:
150 fibers
Recruitment:
increasing the number of motor units activated/responding
Strength increases as…
the number of motor units increases
2 types of tension production:
- sustained tension
- muscle tone
Sustained tension:
- less than maximum tension
- allows motor units to rest in rotation
- uses a lot of ATP
Muscle tone:
-the normal tension and firmness of a muscle at rest
Increasing muscle tone increases:
metabolic energy used even at rest
We use sustained tension to:
Actively maintain body position without motion (isometric contraction)
CrP (creatine phosphate):
stored in skeletal muscle and used to make ATP for skeletal muscle contraction
When muscle can no longer perform a required activity, they are:
Fatigued
4 results of muscle fatigue:
- depletion of ATP
- damage to sarcolemma and sarcoplasmic reticulum
- low pH
- muscle exhaustion and pain
The time required after exertion for muscles to return to pre-exercise condition:
Recovery period
In recovery period, you have to deal with: (3)
- depletion of metabolic reserves by making more glycogen and ATP via aerobic metabolism-> breath heavy
- repair sarcolemma and sarcoplasmic reticulum
- recover from low pH by processing lactic acid via cori cycle
How does the cori cycle play a role in recovery period? (3)
- removal and recycling of lactic acid by the liver
- liver converts lactic acid to pyruvic acid
- glucose is released to recharge muscle glycogen reserves
Muscle hypertrophy:
muscle growth from heavy training
Muscle atrophy:
effects:
lack of muscle activity
-reduces muscle size, tone, and power
3 effects of muscle hypertrophy:
- increases diameter of muscle fibers
- increases number of myofibrils
- increases mitochondria, glycogen reserves
Muscle fibers break down into:
Proteins
