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What is a muscle fibers plasma membrane?
What does myoglobin store?
Glyosomes are granules of?
Function of the SR?
Store Calcium (Ca2+)
What is continuous with sarcolemma and closely associated with SR?
Thick filament is made of?
- Dark band
- Thick and Thin filaments
- Light band
- no thick filament
- Functional unit of myofibril and skeletal muscle.
- From of Z disc to the next.
Interaction between motor neuron and skeletal muscle cell.
Neurotransmitter released at neuromuscular junction:
- ACh (acytocholine)
- Removed by acetylcholinesterase
AP generation on sarcolemma:
- AP at axon terminal
- CA2+ influx
- ACh exocytosis
- ACh binds to receptor
- Chemical-gated Na+ channels open
- Na+ influx
- Voltage-gated Na+ channels open
- Na+ influx
- threshold potential
- positive feedback
- depolarized to AP
- voltage-gated K+ channels open
Cross bridge cycle
- Ap along T tublue opens ca2+ channels in SR
- Ca2+ enters cytosol and binds to troponin
- Tropomyosin shifts position to expose binding sites
- Myosin head binds to actin
- Power stroke of myosin head causes sliding
What is the function of ATP in the cross bridge cycle?
- ATP allows myosin to detach from actin (rigor mortis w/o ATP)
- Hydrolysis of ATP into ADP and Pi provides energy: low state to high state.
Does cross bridge cycle stop immediate after AP disappears?
Not until Ca2+ return to SR
What is shortened during isotonic contraction?
Dense fibrous connective tissue
Enclose the whole muscle
enclose each fascicle
Enclose each muscle fiber
a neuron and all the muscle cells it controls
when a muscle is stimulated bu can no longer contract due to ionic imbalance and SR damage.
the continuous partial contraction state of muscle
Tension develops but muscle does not change length
Muscle length changes during a contraction
brief period without measurable muscle tension.
The period with active sliding of myosin and actin fibers
When the cross bridge cycle stops
- Low frequency
- before relaxation.
- High frequency
- smooth sustained contraction
How does the muscle respond to increased strength of stimulus?
Recruitment of motor units
How is ATP generated for muscle?
- CP pathway which donates P to ADP
- Anerobic glycolysis which produces lactic acid
- aerobic pathway (cellular respiration; produces most ATP)
- 60% of energy from ATP is wasted as heat.
What affects contraction force in a given muscle?
- Size of muscle fiber
- frequency of stimuli
- optimal length
- aerobic pathway
- slow fatigue
- anaerobic glycolysis
- fast fatigue
A muscle usually has....
Fibers in one motor unit are...
What makes a given muscle contract fast?
- Less load
- recruit MORE muscle fibers
- MORE fast fibers
What makes a given muscle contract for longer duration?
- Less load
- recruit more muscle fibers
- more slow fibers
Why are some muscles more powerful than others?
They contain more muscle fibers.
- No T tubule
- Poor SR
- Ca2+ mainly from outside
- Use less ATP
- Stimulation through varcosities
fixed or immovable point of attachment
attachment on the moveable bone
primarily responsible for producing a specific movement
Oppose or reverse the action of another muscle
aids another muscle by promoting the same movement
stabilizes the origin of another muscle
pectoralis major - latissimus dorsi
transport nutrients from capillaries to neurons
form myelin sheath
form myeline sheath
cover neuron cell body
Structure of a neuron
- Cell body
- Myelin sheath
- Afferent fibers
- Carry signal from sensory receptor to CNS
- Efferent fibers
- carry signal from CNS to effector (muscle and gland)
- Most abundant neuron
- Mostly in CNS
- Conduct between motor and sensory neurons
- plasma membrane polarized
less negative than RMP
more negative than RMP
Effect of inreasing extracellular k+ on RMP
RMP becomes less negative.
- variable magnitude
- chemical-gated channels
- depolarization or hyperpolarization
- dendrite and cell body
- voltage-gated channels
- axon hillock (initiate AP) and axon
Why can myelin sheath electrically insulate axon?
membrane lacks ion channels.
Initiate positive feedack: open voltage-gated Na+ channels
What ion is responsible for the depolarization phase and repolarization phase of AP?
- Depolarization: Voltage-gated Na+ changels open, Na+ moves in
- Repolarization: voltage-gated K+ channels open, K+ moves out
How does neuron respond when a stimulus is given in absolute refractory period?
- Na+ channels inactive
- Produce no AP
Relative refractory period?
- Threshold is elevated
- requires stronger stimulus to generate AP
How is the intensity of stimuli to a neuron coded?
high stimulus > high AP frequency
insulate axon to speed up propagation
Node of Ranvier
- exposed region on axon
- boost AP
AP propagates in one direction due to....
absolute refractory period.
Distance between Nodes of Ranvier> ^ AP propagation speed?
No. distance too long so AP cannot propagate
What is the fate of neurotransmitters in the synaptic cleft?
- Reuptake by astrocytes or axon terminals
- degraded by enzymes in synaptic cleft
- diffuse away from synaptic cleft
How does the neurotransmitter open ion channels in the postsynaptic membrane?
- Direction: receptor is ion channel
- Indirectily: open channels through a 2nd messenger.
How do signals from one neuron pass to another?
- Through synapse
- Axon terminal
- Synaptic cleft
- postsynaptic membrane
So these signals always lead to the generation of AP in the post synaptic cleft?