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Medicine 1.1 > Muscle Excitation and Contraction > Flashcards

Muscle Excitation and Contraction Flashcards

1
Q

What type of movement and contraction is associated with skeletal muscle?

A
  • Rapid contractions

- Voluntary movement, facial expressions and manipulation of environments

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2
Q

What type of movement and contraction is associated with cardiac muscle?

A
  • Medium speed contractions
  • Involuntary
  • As it contracts it propels blood into the circulation.
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3
Q

What type of movement and contraction is associated with smooth muscle?

A
  • Slow wave like contractions
  • Propels substances along internal passageways
  • Involuntary
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4
Q

How are ions distributed across the membrane?

A
  • There is uneven distribution of major ions in the intracellular and extracellular components.
  • The body is in a state of electrical disequilibrium because active transport of ions across the cell membrane creates an electrical gradient.
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5
Q

What does an electrical gradient give us?

A

Excitability

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6
Q

What creates an electrical gradient?

A

The input of energy to transport ions across a membrane creates an electrical gradient.

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7
Q

What creates a chemical gradient?

A

The active transport positive ions out of the cell creates a chemical gradient.

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8
Q

What is an electrochemical gradient?

A

The combination of an electrical and chemical gradient is an electrochemical gradient

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9
Q

What is the resting membrane potential?

A

The resting membrane potential is the electrical gradient across the cell membrane.

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10
Q

What helps maintain the electrical gradient?

A

The Na/k pump

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11
Q

What is the significance of motor units?

A

They allow all muscle cells of an area to be controlled by one nerve cell.
eg 1:100 back muscles
1:10 finger muscle
1:1 eye muscle

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12
Q

What are myofibrils separated into?

A

Sacromeres

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13
Q

What structures are present in a sacromere?

A
  • Thin actin filament
  • Thick myosin filament
  • Elastin (Titin)
  • Z discs
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14
Q

What zones can a sacromere be separated into?

A
  • I band (with no myosin)
  • A band (myosin filament)
  • H zone (part with no actin)
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15
Q

Which part of the sacromere structure facilitates for muscle shortening?

A

Elastin (titin filament), they are bound to the Z discs

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16
Q

How do myosin molecules get energy to act?

A

Head region has enzyme that uses ATP hydrolysis, this will confer the energy to movement.

17
Q

How are myosin heads spread on the filament?

A

All around 360 degrees and they dont need to work in unison

18
Q

What are tropomyosin and the trponin molecules used for?

A
  • Tropomyosin blocks/inhibits myosin and actin reacting
  • Troponin C is a calcium binding site.
  • Troponin T takes shape change and amplifies it
  • Troponin I pulls tropomyosin molecule away from groove, stopping inhibition.
19
Q

When is the sacromere relaxed and what occurs in it at this point?

A
  • When there is low levels of Ca
  • Means Z lines are far apart
  • Actin and myosin are not interacting
20
Q

When is the sacromere partially contracted and what occurs in it at this point?

A
  • When there is a bit of Ca
  • Z lines are pulled toward centre of sacromere
  • Actin and myosin not changing in length
21
Q

When is the sacromere fully contracted and what occurs in it at this point?

A
  • When there is more/alot of Ca
  • Z lines hit off end of myosin molecules
  • Actin can start to overlap in centre of sacromere
22
Q

When a muscle length is shortened, which of the following sarcomere features would not shorten?

A

A zone (myosin filament)

23
Q

What is the sarcolemma?

A

The sarcolemma is the plasma membrane of the muscle cell

24
Q

What is the t-tubule?

A

The t-tubules are extensions of the sarcolemma and invaginate into the muscle fibre so that release of Ca from the SR reaches all myofibrils.
. Propagates action potentials into the interior of the muscle fibre

25
Q

Summarise muscle excitation

A
  • Nerve impulse reaches neuromuscular junction
  • acetylcholine is released from motor neuron
  • Ach binds to receptors in the muscle membrane allowing Na to enter
  • Sodium influx will generate an action potential in the sarcolemma
26
Q

Summarise muscle contraction

A
  • Action potential travels down T tubule
  • Sarcoplasmic reticulum releases calcium
  • Calcium binds with troponin to move the troponin, tropomyosin complex.
  • Binding sites in the actin filament are exposed
  • Myosin heads attatch to binding sites and create a power stroke
  • ATP detaches myosin heads and energizes them for another contraction
  • When action potential ceases the muscle stops contracting
27
Q

What is muscle tonus?

A

-Tightness of a muscle, when some fibres are always contracted

28
Q

What is the refractory period of a muscle?

A

Brief period of time when muscle will not respond to stimulus

29
Q

What is muscle tetany?

A

Sustained contraction of a muscle as a result of rapid succession of nerve impulses.
Tetanus can be a result of infection due to tetany, lack of movement.

30
Q

What is creatine?

A

A molecule capable of storing ATP eg. creatine phosphate

31
Q

What causes muscle fatigue?

A

Lack of ATP due to lack of O2.

32
Q

What is muscle atrophy and what may cause it?

A
  • Weakening and shrinking of a muscle
  • May be caused by: -immobilization
  • loss of neural stimulation
  • other factors
33
Q

What is muscle hypertrophy?

A

-Enlargement of a muscle
(more capillaries and mitochondria)
-Caused by strenous exercise or steroid hormones

34
Q

What do steroid hormones do ?

A

Stimulate muscle growth and hypertrophy (eg. testosterone)

35
Q

What is isometric contraction?

A
  • Contractions that produce no movement
  • Used in: - standing
  • posture
  • sitting
36
Q

What is isotonic contraction?

A
  • Contractions that produce movement
  • Used in:
  • walking
  • moving any part pf body
  • Concentric/eccentric

Medicine 1.1 (28 decks)

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