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Medicine Sem 1 > Physiology week 14 > Flashcards

Physiology week 14 Flashcards

1
Q

What is the sarcolemma

A

Muscle cell fiber membrane

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2
Q

What is the sarcolemma composed of

A
  • Plasma membrane
    -Outer coat of polysaccharides and collagen fibrils,(which fuses with tendons to connect muscle to bones)
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3
Q

What does muscle fiberes contain

A
  • Thusands of myofibrils
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4
Q

What are myofibrils made up of

A
  • Actin and mysoin filaments
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5
Q

Why does myofibrils have a striated apperance

A
  • Due to alternating light and dark bands
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6
Q

When does the greatest force of attraction occur

A
  • When the actin and mysoin filaments just being to overlap
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7
Q

Where is Titin located

A

In muscle fibers

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8
Q

What is the function of Titin

A
  • Maintain alignment of myosin and actin filaments
    -Act as a spring, helping the sacromere to contract and relax
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9
Q

What does the sarcoplasm surround

A
  • Myofibrils
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10
Q

What does the sarcoplasm contain

A
  • High amounts of potassium,magnesium,phosphate and enzymes
    -And mitochondria , which produce ATP for muscle contraction
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11
Q

What is the function of Sarcoplasmic retciulul

A
  • Surrounds myofibrils
    -Stores,releases and reabsorbs calcium
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12
Q

Explain the mechanism of a mucle contraction starting from an action potential

A

1.Action potential (AP) travels along a motor nerve
2.Nerve releases acetylcholine (ACh) at the neuromuscular junction.
3.ACh binds to receptors, opening ACh-gated cation channels.
4.Sodium (Na⁺) ions enter the muscle fiber, causing local depolarization.
5.Voltage-gated sodium channels open, generating an action potential in the muscle fiber.
6.Action potential spreads along the muscle membrane, reaching deep into the muscle.
7.Sarcoplasmic reticulum releases calcium (Ca²⁺) ions, triggering actin-myosin interaction.
8.Actin and myosin filaments slide past each other, leading to muscle contraction.
9.Calcium is pumped back into the sarcoplasmic reticulum, ending contraction until the next action potential.

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13
Q

What is myosin filaments composed of

A

-myosin molecules

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14
Q

What does each myosin molecule have and their function

A
  • 2 heavy chains which form a double-helix tail and 2 globular heads
    -4 Light chains : which help to regulate myosin head functiojn
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15
Q

What do myosin heads form

A

Crossbridges

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16
Q

Why do cross bridges have two hinges

A
  • For flexibility, allowing head movement
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17
Q

What is the role of ATPase activity in the myosin heads

A
  • Break down ATP to provide energy for contraction
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18
Q

What are Actin Filaments made of

A
  • Actin
    -Tropomyosin
    -Troponin
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19
Q

Explain the structure of Actin backbone in actin filaments

A
  • It is a double stranded F-actin helix made of G actin subunits
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20
Q

What does each G actin in Actin filaments have

A

ADP molecule that serves as an active site for myosin binding

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21
Q

What is the function of Tropomyosin

A
  • Wraps around actin, blocking actin-myosin binding sites
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22
Q

What does troponin complex consits of and functions

A
  • Troponin I: Binds to actin
    -TnT: Binds to tropomyosin
    -TnC: Binds to calcium ions , initiating contraction
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23
Q

The presence of what is required for actin to bind strongly to mysoin

A
  • ATP and magnesium
24
Q

What is the function of troponin-tropomyosin complex in inhibition

A

It blocks mysoin binding sites on actin, preventing contraction

25
Q

Explain the process in which actin filaments are activated( contaction initiation) by clacium ions

A

-Calcium ions bind to troponin C, causing a conformational change.

-This shifts tropomyosin deeper into the actin groove, exposing myosin binding sites.

-This allows myosin cross-bridges to bind, initiating contraction.

26
Q

Explain the walk-along (ratchet) theory

A
  • Myosin heads attach to actin active sites.
    -This causes a power stroke, where myosin tilts and pulls actin.
    -The head then detaches, resets, and binds to a new site, repeating the process.
27
Q

What does having more cross bridges mean..

A
  • A greater contraction force
28
Q

The muscle contraction cycle repeats until

A
  • The z membrane reaches the myosin filaments
    -The muscle load is too great for further contraction
29
Q

Explain the step by step process of ATP driven contraction

A

-ATP binds to myosin head, and ATPase breaks it into ADP + phosphate, storing energy.
-Calcium ions bind to troponin, exposing actin binding sites.
-Myosin head attaches to actin, triggering a power stroke that pulls actin.
-ADP and phosphate are released, and new ATP binds, causing detachment from actin.
-ATP is cleaved again, resetting the myosin head for the next cycle.

30
Q

What is the work equation

A

W=L x D ( work = load x Distance)

31
Q

Name the three Energy sources

A
  • Phosphocreatine
    -Glycolysis
    -Oxidative metabolism
32
Q

Explain how phosphocreatine acts as an energy source

A

Provides instant ATP regeneration by transferring its high-energy phosphate bond

33
Q

Explain how Glycolysis acts as an energy source:
What is dosent require
-What its faster than

A

Breaks down glycogen to Pyruvic acid/lactic acid producing ATP
-oxygen
- produces ATP faster than oxidative metabolism

34
Q

How does Oxidative metabolism act as an energy source

A

Uses oxygen,glycolysis byproducts and foodstuffs(carbs,fat,proteins), to generate ATP

35
Q

Name the types of muscle contraction

A

-Isometric contraction
-Isotonic contraction

36
Q

Explain what happens to the muscles and tension in the 2 types of muscle contraction

A

Isometric: Muscle does not shorten ,but tension increase
Isotonic: Muscle shortens at constant tension , while lifting a load

37
Q

Name the 2 systems used to record muscle contraction

A

-Isometric system
-Isotonic system

38
Q

Explain what the 2 systems measure to record muscle contraction

A

Isometric system: Measures force changes without muscle shortening
Isotonic system: Measures muscle shortening while lifting a load

39
Q

Name the types of muscle fibers

A

Fast and slow muscle fibers

40
Q

Explain slow muscle fibers 4 (characteristics)

A
  • Small
    -Extensive blood supply and many capillaries for oxygen transport
    -Contains large amounts of mitochondria to support oxidative metabolism
  • Contains myoglobin , which stores energy and gives a red colour
41
Q

Explain fast muscle fibers (characteristics) 5

A

-They are large for strong contraction
-Have extensive sarcoplasmic reticulum for rapid calcium release
-High glycolysis enzyme content
-Has less blood supply and mitochondria
-Low myoglobin, which gives the muscle the white colour

42
Q

What does a motor unit consist of

A
  • All muscle fibers innervated by a single motonueron
43
Q

What type of control does small muscles need

A
  • fine control
44
Q

What type of force does large muscles need

A
  • High force
45
Q

What is summation

A
  • Adding individual twitch contractions to increase intensity
46
Q

Name the 2 types of summation

A
  • Multiple Fiber summation
  • Frequency summation
47
Q

When does tetanization occur

A
  • When contraction frequency is high enoughh that twitches fuses into a smooth continous contraction
48
Q

Prolonged contraction leads to fatigue mainly due to:

A

-Depletion of glycogen
-Reduced nerve signal transmission
- Loss of oxygen and nutrients

49
Q

What happens in muscle Hypertrophy

A
  • An increases in muscle mass due to more actin and myosin filaments
50
Q

What does muscle hypertrophy require

A
  • Forceful contractions
51
Q

What happens in muscle atrophy

A
  • Muscle mass decreases due to protein degredation
52
Q

What causes an increased muscle length

A
  • New sacromeres being added at the fiber ends
53
Q

What acauses shortened muscle

A
  • Sacromeres diappearing
54
Q

What is muscle fiber hyperplasia

A
  • Increases in fiber number undere extreme force conditions
55
Q

What happens in muscle denervation

A
  • Loss of nerve supply
56
Q

What is contracture caused by

A

When fibrous tissue continues to shrink, leading to permeanent muscle shortening(contracture)

57
Q

How can debilitating deformities be prevented

A
  • Physical therapy and stretching

Medicine Sem 1 (44 decks)

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