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Flashcards in Muscles 2 Deck (49):

What is used to supply the energy for muscle contraction?

ATP is used for muscle contraction


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

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


What does ATP also do in muscles?

ATP powers Ca2+-ATPase in the sarcoplasmic reticulum:

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


What is the sarcoplasmic reticulum?

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


What does repeated muscle stimulation result in?

Repeated muscle stimulation results in fatigue


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

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


What does fatigue depend on?

Fatigue depends on:

Fibre type

Length of contraction

Fitness of individual


What is the purpose of muscle fatigue?

Fatigue prevents muscles from using vast amounts of ATP


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

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


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

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


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

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


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

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

Low muscle glycogen

Low blood glucose



What is central command fatigue?

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


What are skeletal muscles characterised based on?

Skeletal muscles are characterised based on:

Fast or slow shortening

Oxidative or glycolytic ATP forming pathways used


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

Fast shortening muscles have more ATPase present



What are some properties of oxidative fibres?

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


What are some properties of glycolytic fibres?

Properties of glycolytic fibres are:

Few mitochondria

Increase glycolytic enzymes and glycogen

Lower blood supply

White with larger diameters


What are the 3 types of muscle fibres?

The 3 types of muscle fibres are:

Slow oxidative (I), resist fatigue

Fast oxidative (IIa), intermediate fatigue

Fast glycolytic (IIb), fatigue quickly


What type of muscle fibres do most muscles contain?

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


What is recruitment?

Recruitment is increasing the number of active muscle units


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

During recruitment as load increases:

Slow oxidative is activated first

Fast oxidative second

Fast glycolytic last


What does neural control of muscle fibres depend on?

Neural control of muscle fibres depends on:

Frequency of APs to motor units

Recruitment of motor units


What is denervation atrophy?

Denervation atrophy is the destruction of the nerve/NMJ


What is disuse atrophy?

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


What does disuse and denervation atrophy cause?

Disuse and denervation atrophy causes a decrease in muscle mass


What is hypertrophy?

Hypertrophy is an increase in muscle mass


What causes hypertrophy?

Exercise causes hypertrophy


What does aerobic exercise do in terms of hypertrophy?

Aerobic exercise:

Increases mitochondria

Increases vascularisation

Increases fibre diameter


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

Anaerobic/strength exercise:

Increases fibre diameter

Increases glycolysis


What determines what types of muscle fibres you have?

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


What are some properties of smooth muscle?

Properties of smooth muscle are:

No striations

Innervated by the ANS

Has X bridges and uses Ca2+

Mononucleate and divides throughout life



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

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


What causes dephosphorylation of X bridges in smooth muscle?

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


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

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


What are sources of Ca2+ in smooth muscle?

Sources of Ca2+ in smooth muscle are:

Sarcoplasmic reticulum

Extracellular from voltage activated Ca2+ channels


Which of skeletal and smooth muscle has more sarcoplasmic retiulum?

Skeletal muscle has more sarcoplasmic reticulum than smooth muscle


How is Ca2+ removed from the cytosol?

Ca2+ is removed from the cytosol by:

Pumping back into the sarcoplasmic reticulum

Pumping out of cell by ATPases


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

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


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

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


Why does smooth muscle have tone?

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


What are factors that effect contractile activity?

Factors that effect contractile activity are:

Sponteneous electrical activity

Autonomic neurotransmitter from varicosites


Local factors (pH, O2, etc)



What are the two smooth muscle types?

The two smooth muscle types are:

Single unit



What are examples of single unit smooth muscle?

Examples of single unit smooth muscles are:


Small blood vessels


What are examples of multiunit smooth muscles?

Examples of multiunit smooth muscles are:


Large arteries


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

Single unit smooth muscle has many cells linked by gap junctions

Multiunit smooth muscle has few or no gap junctions


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

Single unit smooth muscles contract in response to stretching

Multiunit smooth muscles do not responds to stretch


What is multiunit smooth muscles richly innervated by?

Multiunit smooth muscles are richly innervated by the ANS


How do single unit smooth muscles contract?

Single unit smooth muscles contract in sync with each other


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

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