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Bmsc207 > Muscle 2 > Flashcards

Muscle 2 Flashcards

1
Q

what shortens during contraction

A

sarcomere

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2
Q

what happens with actin and myosin as a contraction takes place in a sarcomere

A

actin and myosin slide past each other, but don’t change length

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3
Q

which zones and bands shorten during contraction? which stay constant?

A

H zone and I band shorten
A band remains constant

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4
Q

what is the force generated by a contracting skeletal muscle referred to as ?

A

muscle tension

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5
Q

what is the order of initiation of skeletal muscle contraction? (3)

A

events in the CNS (brain responds to voluntary movement)

neuromuscular junction (synaptic contact between somatic motor neuron and individual muscle fibre)

excitation- contaction coupling (an action potential In skeletal muscle fibre results in an increase in intracellular (sarcoplasmic) Ca2+)

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6
Q

what is the output system towards skeletal muscle

A

primary motor cortex

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7
Q

what is the corticospinal tract

A

descending tract (ventral and interior)

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8
Q

what is an upper motor neuron (what does it travel through)

A

brain to brainstem or spinal cord

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9
Q

where does an alpha motor neuron travel? what is unique about it

A

it goes from the spinal cord to muscle and it can be very long

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10
Q

what is an alpha motor neuron

A

it is a lower neuron that goes from the spinal cord to muscle

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11
Q

what is a single motor neuron and all the muscle fibres it activates known as

A

motor unit

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12
Q

what is the area where the motor neuron makes synaptic contact with the muscle fibre known as

A

the neuromuscular junction

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13
Q

how does one motor unit contract

A

all parts of it contract together

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14
Q

what happens to muscle fibres if their motor unit becomes active

A

they all respond simultaneously

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15
Q

what are the 3 components of a neuromuscular junction

A
  1. presynaptic motor neuron filled with synaptic vesicles
  2. the synaptic cleft
  3. the postsynaptic membrane of the skeletal muscle fibre
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16
Q

what is the motor end plate ?

A

the region of sarcolemma at the end of the neuromuscular junction

17
Q

what do junctional folds do

A

increase surface area on sarcolemma

18
Q

what do motor neuron vesicles contain

A

acetylcholine

19
Q

what does the muscle fibre sarcolemma contain (motor end plate)

A

nicotinic acetylcholine receptors

20
Q

what causes voltage gated Ca2+ channels to open

A

an action potential arriving at the axon terminal

21
Q

what is acetylcholine metabolized by? (Broken down)

A

acetylcholinesterase

22
Q

what is required for nicotinic ACh receptors to open

A

two acetylcholine molecules bound to it

23
Q

What is a neuromuscular junction?

A

Synapse of a lower motor neuron to a muscle fibre

24
Q

What kind of receptors does the muscle sarcolemma contain

A

Nicotine acetylcholine receptors

25
Q

What is a monovalent cation channel? What is it permeable to?

A

It is a ligand gated ion channel
Permeable to NA and K

26
Q

What does Na entry through nicotinic ACh receptors generate? What does the response generated do?

A

An excitatory end plate potential

It spreads to adjacent voltage gated Na channels and initiates un action potential

27
Q

What does myasthenia gravis mean?

A

Severe weakness of muscle

28
Q

True or false: a single muscle fibre can be controlled by multiple alpha motor neurons

A

False

29
Q

Where do action potentials start from and go to in muscle?

A

From the sarcolemma to the interior of muscle fibres along the transverse tubules

30
Q

What is the specialized calcium storing organelle in muscles?

A

Sarcoplasmic reticulum

31
Q

What triggers contraction in all muscle types?

A

A rise in intracellular calcium

32
Q

Where do t-tubules surround a sarcomere?

A

A and I band junctions

33
Q

What is a DHP receptor?

A

L-type Ca channel → voltage sensitive

34
Q

What is a ryanodine receptor? (RyR)

A

Ca release channel on sarcoplasmic reticulum

35
Q

What initiates an action potential in t tubules?

A

Entry of Na through acetylcholine receptors

36
Q

What type of gate is a ryanodine receptor

A

Mechanical, it is opened by the DHP

37
Q

Where are DHP receptors located

A

T-Tubules

38
Q

Where are DHP receptors located

A

T-Tubules

Bmsc207 (27 decks)

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