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Science for Medicine > Muscles 2 > Flashcards

Muscles 2 Flashcards

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1
Q

What is used to supply the energy for muscle contraction?

A

ATP is used for muscle contraction

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2
Q

What is the process of the hydrolysis of ATP to energise X bridges?

A
  1. ATP binds to myosin
  2. Dissociates bridges bond to actin
  3. New cycle may begin
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3
Q

What does ATP also do in muscles?

A

ATP powers Ca2+-ATPase in the sarcoplasmic reticulum:

  1. Ca2+ pumped back into sarcoplasmic reticulum
  2. Contraction ends
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4
Q

What is the sarcoplasmic reticulum?

A

The sarcoplasmic reticulum is similar to the endoplasmic reticulum, it is found in muscle cells and stores Ca2+

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5
Q

What does repeated muscle stimulation result in?

A

Repeated muscle stimulation results in fatigue

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6
Q

What can a fatigued muscle do after it has been rested?

A

After a fatigued muscle has been rested it can be stimulated again

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7
Q

What does fatigue depend on?

A

Fatigue depends on:

Fibre type

Length of contraction

Fitness of individual

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8
Q

What is the purpose of muscle fatigue?

A

Fatigue prevents muscles from using vast amounts of ATP

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9
Q

What would happen if fatigue never occured and the muscle used vast amounts of ATP?

A

If they muscle used vast amounts of ATP then it would not be able to activated new X bridges due to a lack of ATP

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10
Q

What is the difference in perform between a muscle that is pre and post fatigue?

A

After fatigue a muscle cannot maintain tension for as long as before

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11
Q

What is fatigue caused by during high intensity, short duration exercise?

A

During high intensity, short duration exercise fatigue is caused by:

Conduction failure due to high [K+] causing depolarisation

Increasing [lactic acid] acidifies protein

[ADP] and [Pi] inhibits X bridge cycle

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12
Q

What is fatigue caused by during low intensity, long duration exercise?

A

During low intesity, long duration exercise fatigue is caused by:

Low muscle glycogen

Low blood glucose

Dehydration

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13
Q

What is central command fatigue?

A

Central command fatigue is where the cerebral cortex cannot excite motor neurons

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14
Q

What are skeletal muscles characterised based on?

A

Skeletal muscles are characterised based on:

Fast or slow shortening

Oxidative or glycolytic ATP forming pathways used

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15
Q

Which of fast and slow shortening muscles has more ATPase present?

A

Fast shortening muscles have more ATPase present

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16
Q

What are some properties of oxidative fibres?

A

Some properties of oxidative fibres are:

High mitochondria

High vasodilation to deliver more oxygen and nutrients

Contains myoglobin to increase oxygen delivery

Red with low diameters

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17
Q

What are some properties of glycolytic fibres?

A

Properties of glycolytic fibres are:

Few mitochondria

Increase glycolytic enzymes and glycogen

Lower blood supply

White with larger diameters

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18
Q

What are the 3 types of muscle fibres?

A

The 3 types of muscle fibres are:

Slow oxidative (I), resist fatigue

Fast oxidative (IIa), intermediate fatigue

Fast glycolytic (IIb), fatigue quickly

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19
Q

What type of muscle fibres do most muscles contain?

A

Most muscle fibres contain a mix of all 3 muscle fibres (slow oxidative, fast oxidative and fast glycolytic)

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20
Q

What is recruitment?

A

Recruitment is increasing the number of active muscle units

21
Q

In what order are the 3 muscle fibre types activated during recruitment as load increases?

A

During recruitment as load increases:

Slow oxidative is activated first

Fast oxidative second

Fast glycolytic last

22
Q

What does neural control of muscle fibres depend on?

A

Neural control of muscle fibres depends on:

Frequency of APs to motor units

Recruitment of motor units

23
Q

What is denervation atrophy?

A

Denervation atrophy is the destruction of the nerve/NMJ

24
Q

What is disuse atrophy?

A

Disuse atrophy is a decrease in muscle mass due to not being used

25
Q

What does disuse and denervation atrophy cause?

A

Disuse and denervation atrophy causes a decrease in muscle mass

26
Q

What is hypertrophy?

A

Hypertrophy is an increase in muscle mass

27
Q

What causes hypertrophy?

A

Exercise causes hypertrophy

28
Q

What does aerobic exercise do in terms of hypertrophy?

A

Aerobic exercise:

Increases mitochondria

Increases vascularisation

Increases fibre diameter

29
Q

What does anaerobic/strength exercise do in terms of hypertrophy?

A

Anaerobic/strength exercise:

Increases fibre diameter

Increases glycolysis

30
Q

What determines what types of muscle fibres you have?

A

The type of exercise that you do determins that type of muscle fibres that you have

31
Q

What are some properties of smooth muscle?

A

Properties of smooth muscle are:

No striations

Innervated by the ANS

Has X bridges and uses Ca2+

Mononucleate and divides throughout life

32
Q

What is the process of smooth muscle X bridge cycle activation?

A

The process of smooth muscle X bridge cycle activation is:

  1. Increased [Ca2+] which binds to calmodulin
  2. Ca2+-calmodulin binds to myosin light chain kinase
  3. Phosphorylates X bridge with ATP
  4. Phosphorylated X bridges bind to actin filaments
  5. Causes contraction and tension
33
Q

What causes dephosphorylation of X bridges in smooth muscle?

A

Myosin light chain photases causes dephosphorylation of X bridges and the muscle relaxes

34
Q

What does persistant stimulation and increase of [Ca2+] lead to in smooth muscle?

A

Phosphorylated X bridges dephosphorylating when still bound to actin

Decrease rate of ATP splitting

Slows X bridge cycle

Can maintain tension for long time with low ATP consumption

Useful in blood vessels

35
Q

What are sources of Ca2+ in smooth muscle?

A

Sources of Ca2+ in smooth muscle are:

Sarcoplasmic reticulum

Extracellular from voltage activated Ca2+ channels

36
Q

Which of skeletal and smooth muscle has more sarcoplasmic retiulum?

A

Skeletal muscle has more sarcoplasmic reticulum than smooth muscle

37
Q

How is Ca2+ removed from the cytosol?

A

Ca2+ is removed from the cytosol by:

Pumping back into the sarcoplasmic reticulum

Pumping out of cell by ATPases

38
Q

Is the removal of Ca2+ quicker in skeletal or smooth muscle?

A

The removal of Ca2+ is quicker in skeletal muscle than smooth muscle

39
Q

How does the effects of an action potential differ in a skeletal muscle and a smooth muscle in regards to the release of Ca2+?

A

In a skeletal muscle one action potential releases enough Ca2+ to saturate all troponin sites

In smooth muscle only some sites are activated, concentration graded depending on the amount of action potentials

40
Q

Why does smooth muscle have tone?

A

Smooth muscle has tone because the basal level of Ca2+ in the cell causes a constant level of tension

41
Q

What are factors that effect contractile activity?

A

Factors that effect contractile activity are:

Sponteneous electrical activity

Autonomic neurotransmitter from varicosites

Hormones

Local factors (pH, O2, etc)

Stretch

42
Q

What are the two smooth muscle types?

A

The two smooth muscle types are:

Single unit

Multiunit

43
Q

What are examples of single unit smooth muscle?

A

Examples of single unit smooth muscles are:

Uterus

Small blood vessels

44
Q

What are examples of multiunit smooth muscles?

A

Examples of multiunit smooth muscles are:

Airways

Large arteries

45
Q

What is the difference between the gap junctions of a single and a multiunit smooth muscle?

A

Single unit smooth muscle has many cells linked by gap junctions

Multiunit smooth muscle has few or no gap junctions

46
Q

Explain the difference in response to stretch between single unit and multiunit smooth muscles?

A

Single unit smooth muscles contract in response to stretching

Multiunit smooth muscles do not responds to stretch

47
Q

What is multiunit smooth muscles richly innervated by?

A

Multiunit smooth muscles are richly innervated by the ANS

48
Q

How do single unit smooth muscles contract?

A

Single unit smooth muscles contract in sync with each other

49
Q

Why is most smooth muscle in organs a mixture of both single and multiunit smooth muscle?

A

They are a mixture of both to give a variety of properties to suit the function of the organ

Science for Medicine (55 decks)

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