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MSK > Physiology > Flashcards

Physiology Flashcards

1
Q

Explain what a motor unit is

A

A single alpha motor neuron and the muscle fibres that it innervates

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2
Q

What is a muscle fibre?

How big is it?

A

1 muscle cell

Typically the full length of the muscle

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3
Q

What is the neurotransmitter at the neuromuscular junction?

A

ACh

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4
Q

What 2 things are needed for muscle contraction?

A

Ca2+

ATP

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5
Q

Where does skeletal muscle get its Ca2+ from?

A

SR only

Ca2+ is released from lateral sacs as action potential spreads down transverse (T)-tubules

(look at diagram in notes)

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6
Q

Explain how rigor mortis takes place?

A

Muscles need ATP in order to contract and RELAX

Without ATP muscles continually seize

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7
Q

What is the smallest functional unit in skeletal muscle?

A

Sacromere

Functional unit = ability to carry out full function of cell

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8
Q 
Draw and label a sacromere:
A band
H zone
M line
I band
A

A band - area of actin and myosin that overlaps

H zone - central area of myosin with no overlap of actin

I band - peripheral areas of actin with no myosin underneath

M line - central part of myosin

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9
Q

What has more muscle fibres per motor unit - intricate muscles or large powerful muscles?

A

Intricate muscles - fine movement requires more motor units per muscle fibres

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10
Q

What 2 things is the gradation of muscle contraction dependant on?

A
  • No of motor units stimulated (motor unit recruitment)

- Summation of contractions + length of fibre

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11
Q

Explain how tetanus can become a thing in skeletal muscle

A

In skeletal muscle action potentials are much smaller than contractions
Hence multiple action potentials can occur and enable constant contraction of muscle

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12
Q

What prevents cardiac muscle from becoming tetanised?

A

Long refractory period

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13
Q

What is optimum length of muscle?

A

The optimum overlap of actin and myosin that allows for maximum tetanic tension

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14
Q

What are the 2 types of skeletal muscle contraction - describe them both?

A

Isotonic - length changes and tension stays the same
Isometric - length stays same and tension changes

Met = police = rising tension

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15
Q

How is muscle contraction in sarcomeres communicated to the bones of the body?

A

Via the elastic component of muscle e.g. tendons/connective tissue

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16
Q

What impact does increased load have on velocity of muscle contraction?

A

Increased load decreases velocity of contraction

think if holding something v heavy on fingers it would take more time to scrunch up hand

17
Q

Describe how each of the following types of fibres get their energy:
Type I
Type IIa
Type IIx

A

Type I - slow twitch - aerobic
Type IIa - intermediate-twitch - aerobic and anaerobic
Type IIx - fast twitch - anaerobic

18
Q

What pathways are involved in providing immediate energy to muscle cells and energy in oxygenated and deoxygenated situations

A

Immediate - transfer of creatine phosphate to ADP = ATP
Oxygenated - oxidative phosphorylation
Deoxygenated - glycolysis

19
Q

What is a stretch reflex?

A

Sterotyped response to a specific stimulus

20
Q

Stretching of the muscle results in firing of what kind of neurons

A

Afferent neurons

21
Q

What are muscle spindles also known as and what are the sensory nerve endings found within them called?

Where are they found?

A

Intrafusal fibres - in the belly of the muscle

Annulospiral fibres

22
Q

What motor neurons supply the intrafusal fibres (muscle spindles)?

What is the role?

A

Gamma motor neurons

Maintain sensitivity of intrafusal muscle fibres to stretch

23
Q

What are nociceptors?

What are noxious stimuli?

A

1st order neurons

Afferent neurons activated NORMALLY by noxious stimuli

Thermal, mechanical and chemical

24
Q

What are the 2 types of nociceptors and compare them based on:

  • Speed of transmission
  • Response to what kind of stimuli
  • Myelination
A

A𝛿-fibres

  • Fast/1st
  • Thinly myelinated
  • Mechanical/thermal

C-fibres

  • 2nd/slow
  • no myelination
  • ALL noxious stimuli (polymodal)
25
Q

Describe the pathway of a 1st order neuron

A

From site of noxious stimuli
Travels to soma (cell body) in dorsal root ganglion
Terminates in dorsal horn of spinal cord

26
Q

What neurotransmitters are found between afferent 1st and 2nd order neurons? (in dorsal horn of spinal cord)

A

Peptides and glutamate

27
Q

What are the 2 tracts of 2nd order neurons and what is each responsible for?

Where do they travel?

A 
Spinothalamic tract (STT)
- Perception of pain (intensity and location)
Spinoreticulothalamic tract (SRT)
- autonomic response to pain, arousal, fear etc.

Anterolateral system

28
Q

Where do 2nd order neurons terminate?

A

Thalamus

29
Q

How is pain classified?

A 
Time course
Severity 
Source of pain (visceral/somatic)
Mechanisms 
- Nociceptive
- Inflammatory 
- Pathological
30
Q

What mechanisms of pain are adaptive? What are maladaptive?

A

Adaptive

  • Nociceptive
  • Infammatory

Maladaptive
- Pathological

31
Q

In terms of inflammatory pain what is hyperalgesia and what is allodynia?

What causes inflammatory pain?

A

Hyperalgesia - increased sensitivity to noxious stimuli
Allodynia - increased sensitivity to innocuous (harmless) stimuli

Activation of immune system - increased cytokine production and local inflam

32
Q

What are the 2 types of pathological mechanism, describe them

What analgesics can be used?

A

Neuropathic - damage to neural tissue
Dysfunctional - no identifiable damage/inflam e.g. IBS

Normal analgesics don’t work - ~use anti-depressants

33
Q

What gives skeletal muscle it’s striated appearance?

A

Dark areas = A zone (where myosin and actin overlap)

Light zones = I zone (where actin is without myosin)

34
Q

How does the rapid termination of muscle contraction occur?.

A

ACh is broken down by AChE (acetylcholinesterase) at the end plate membrane

35
Q

How does Ca+ release from the SR lead to muscle contraction?

A

Ca+ binds to troponin on actin which causes tropomyosin to move out of the way and thencross-bridge binding sites are avaliable for myosin to bind to actin and contract

MSK (41 decks)

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