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MNSR > Lecture 8 > Flashcards

Lecture 8 Flashcards

1
Q

Muscle?

A

Tissue with the ability to contract and relax

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2
Q

Tendon?

A

Tough band of fibrous connective tissue that connects muscle to bone

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3
Q

Ligament?

A

Attaches bone to bone

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4
Q

How many skeletal muscles are there in the human body?

A

Approximately 650

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5
Q

How many surface (anatomical) muscles are there in the human body?

A

Over 150

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6
Q

Are muscles attached to 2 different bones of the skeleton?

A

Yes, one attachment is fixed and called the origin and the other called the insertion is drawn towards the origin

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7
Q

Muscles tend to work in groups or sets, so how are they arranged in antagonistic pairs?

A
  • Flexor closes a joint

- Extensor opens a joint

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8
Q

Epimysium?

A

A loose connective tissue sheath that is bound to each muscle

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9
Q

Muscle composition?

A
  • Each muscle is composed of bundles of fascicles
  • Each fascicle is composed of many muscle fibers
  • Each fiber is composed of smaller fibers called myofibers
  • The myofibers contain the contractile apparatus – the sarcomere
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10
Q

What are three muscle types?

A

Skeletal muscle:
- Attached to bones

Cardiac muscle:
- Walls of the myocardium

Smooth muscle:
- Organs

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11
Q

Striated Muscle?

A
  • Voluntary muscle i.e. under direct nervous control

- Low endurance muscle

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12
Q

What is the structure of the muscle fibres in striated muscles?

A
  • Hexagonal
  • Nuclei on outside (peripheral)
  • Fibres generally have the same size
  • Polynucleated
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13
Q

How are muscle biopsies done?

A

Wide-bore Needle inserted into muscle, and a small ‘tube’ of muscle removed

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14
Q

Cardiac muscle?

A
  • Only in the heart
  • A type of striated muscle but related to smooth muscle
  • Involuntary muscle
  • High endurance muscle
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15
Q

What is the structure of the muscle fibres in cardiac muscles?

A
  • Intercalated discs (gap junctions)
  • 1- 2 nuclei per cell
  • Centrally placed nuclei
  • Innervated by the pace maker
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16
Q

Smooth Muscle?

A
  • Lines the digestive tract, bronchus and blood vessels
  • Involuntary muscle i.e. not under direct nervous control
  • High endurance muscle
17
Q

What is the structure of the muscle fibres in smooth muscles?

A
  • 1 centrally placed nucleus per cell
  • No striations
  • Sustained contraction
18
Q

What is a motor unit?

A

The functional unit of skeletal muscle is the motor unit (MU)

19
Q

What is a motor unit composed of?

A
  • A single motor neuron

- The group of muscle fibres innervated by it

20
Q

Why must some motor neurons innervate more than one fibre?

A

Bc there are considerably more muscle fibres than there are motor neurons

21
Q

What does the number of muscle fibres per motor unit vary according to?

A
  • The fineness of the control required

- Fewer muscle fibres per motor unit leads to increased dexterity and vice versa

22
Q

Neuromuscular Junction (NMJ)?

A
  • Also known as the motor endplate
  • The connection between the muscle fibre and its motor neuron
  • The membranes of the nerve and muscle cells come into close contact
  • One NMJ per fibre
23
Q

What happens when muscle fibre is stimulated at the NMJ?

A

It contracts; this is an “all-or-nothing” response

24
Q

When is there maximal contraction?

A

When all MUs are firing tog

25
Q

What are the two ways that muscles contract?

A
  1. Isometric contraction
    ‘same length’
  2. Isotonic contraction
    ‘same tension’
26
Q

Isometric contraction?

A
  • The length of the muscle does not change
  • The tension on the muscle increases
  • Muscle contracts but doesn’t shorten
27
Q

Isotonic Contraction?

A
  • The muscle length changes

- The tension remains constant

28
Q

Two types of Isotonic contraction?

A

Concentric – Muscle shortens

Eccentric – Muscle lengthens

29
Q

Concentric Isotonic Contraction?

A
  • Force generated by the muscle is greater than the load to be lifted
  • Muscle shortens in length
30
Q

Eccentric Isotonic Contraction?

A
  • Force generated by the muscle is less than the load applied to it
  • Muscle lengthens as it contracts
31
Q

When/why do Eccentric Isotonic Contractions happen?

A
  • Also occur to slow joint movement
  • Muscles undergoing heavy eccentric loading suffer greater damage when overloaded leading to greater muscle necrosis
  • Principle behind body building
  • Muscles are approximately 10% stronger during eccentric contractions than during concentric contractions
32
Q

Three phases to muscle contraction?

A
  • Latent period (0.005 sec) between the stimulus and first visible reaction
  • Contraction period (0.04 sec) when the muscle shortens
  • Relaxation period (0.05 sec) the muscle returns to its original length
  • After initial stimulation there is a short period during which muscle will not respond to further stimulus called the Refractory period (0.002 sec)
33
Q

How does summation happen (general)?

A
  • Muscle can respond to a second stimulation while still contracting
  • Stimulation at frequency shorter than the twitch time results in the second stimulus being superimposed on the first
  • This results in a greater shortening of the muscle (summation)
34
Q

What are two different ways in which summation can occur?

A
  1. By increasing the number of motor units involved - called multiple motor unit summation (recruitment)
  2. By increasing the rate of contraction of individual motor units - called wave summation
  • In practice both these occur together during contraction helped by the asynchronous firing of the motor units
35
Q

Tetanization?

A
  • As the impulse frequency increases the twitches become superimposed upon one another in wave summation (10 pulses/sec)
  • Eventually increasing stimulus causes the successive contractions to fuse together in a state of maximal contraction called tetanus (>40 pulses/sec)
  • Upon tetanization further increased stimulation will only result in very slight shortening
36
Q

Is the action equal at both the insertion and the origin?

A

Yes

37
Q

What is one thing that muscles don’t do?

A

Push, they can only contract

38
Q

What does the muscle or its nerve respond with when it is stimulated by a single electric shock?

A

A quick twitch

MNSR (12 decks)

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