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MNSR - MCQ > MNSR 7 - Muscular System: Anatomical Muscles and Muscle Physiology > Flashcards

MNSR 7 - Muscular System: Anatomical Muscles and Muscle Physiology Flashcards

1
Q

What are muscles?

A

Aggregations of cells which convert chemical energy (ATP) into mechanical energy (movement)

Highly adapted cells allowing for force-generation (i.e. contraction)

Specialized adaptations of cellular components (e.g. sarcoplasmic reticulum and contractile proteins)

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2
Q

What are the three muscle types?

A

Skeletal muscle
Attached to bones which form levers- used for bodily movement

Cardiac muscle
Walls of the myocardium - used to pump blood through circulatory system

Smooth muscle
Organs - lines gut and blood vessels - controls diameter of these tubes and in gut helps to propel the digested food

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3
Q

What is the structure of the smooth muscle?

A

Lines the digestive tract, bronchus and blood vessels
* Involuntary muscle i.e. not under direct nervous control
* Lacks the striations of skeletal and cardiac muscle tissue
*1 nucleus per smooth muscle cell
*High endurance muscle

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4
Q

What is the function of smooth muscle?

A

Sustained contractions (e.g. small and large intestine)

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5
Q

Where is cardiac muscle found?

A

Found only in the walls of the heart

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6
Q

What is the structure of cardiac muscle?

A
  • Unevenly striated
    (so similar to skeletal muscle in appearance)
  • Alternating light and dark bands (striations) as seen when examined with a microscope
  • High endurance (high number of mitochondria); contracts throughout the lifespan
  • (1- 2 nuclei per cardiac cell/myocyte (centrally placed)
  • Innervated by the pacemaker
    fused-together cylindrical cells

At border between one cardiac cell and the next are “Intercalated discs”which support synchronized contraction of cardiac tissue. These discs contain: desmosomes and gap junctions.
The fused cardiac cells contract as a unit owing to signals at gap junctions between them

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7
Q

What are the functions of cardiac muscles?

A
  • Contraction is involuntary (like smooth muscle)
  • Contraction and relaxation of the heart is not consciously controlled
  • Contraction of the heart is initiated by a node of tissue called the “pacemaker”
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8
Q

What is the structure of a skeletal muscle?

A
  • So named because most skeletal muscles move bones
  • Called striped or striated due to appearance under light microscope
  • Long cylindrical cells
  • Many nuclei per cell (‘multinucleated’)
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9
Q

What is the function of the skeletal muscle?

A
  • Locomotion, posture; head, limb movements
  • Voluntary muscle i.e. under direct nervous control. e.g. biceps muscle
    often reflex-activated
  • Endurance capacity depends on number of mitochondria.
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10
Q

How is the skeletal muscle often described as?

A

Often described as being of ‘low endurance’ compared to other muscle types.

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11
Q

Each muscle is composed of bundles of…

A

fascicles

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12
Q

Each fascicle is composed of many…

A

muscle fibres

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13
Q

In most anatomical muscles the fibres extend the…

A

entire length of the muscle

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14
Q

Each fibre is composed of _______________ which contain the contractile apparatus – the ____________

A

smaller myofibrils, sarcomere

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15
Q

Muscles have extensive vascular systems that…

A

1) Supply large amounts of oxygen
2) Supply nutrients
3) Carry away wastes

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16
Q

Skeletal muscles are voluntary muscles, controlled by…

A

nerves of the central nervous system (brain and spinal cord)

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17
Q

The connective tissue components include…

A

Epimysium
* The outermost layer

Perimysium
* Surrounds numerous bundles of fascicles
* Separates 10-100 muscle fibers into bundles called fascicles

Endomysium
* Separates individual muscle fibers from one another

Tendon
* Cord that attach a muscle to a bone

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18
Q

How would you describe muscles?

A

Tissue with the ability to contract

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19
Q

How would you describe tendons?

A

Tough band of fibrous connective tissue that connects muscle to bone

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20
Q

How would you explain ligaments?

A

Attaches bone to bone

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21
Q

One attachment is fixed and called the…

A

origin

22
Q

The other called the _________________ is drawn towards the origin.

A

insertion

23
Q

Muscles can only…

A

contract and never push

24
Q

Arranged in

A

antagonistic pairs

25
Q

___________ closes a joint

A

Flexor

26
Q

____________ opens a joint

A

Extensor

27
Q

What does the Biceps Brachii do?

A

Flexes the elbow

28
Q

What does the Triceps Brachii do?

A

Extends the arm

29
Q

What happens during isometric contraction?

A

The length of the muscle does not change
The tension on the muscle increases
I.e. Holding a book steady using an outstretched arm

30
Q

What happens during isotonic contraction?

A

The muscle length changes
The tension remains constant

31
Q

What are the two types of Isotonic contraction?

A

Concentric – Muscle shortens
Eccentric – Muscle lengthens

32
Q

What happens during Concentric Isotonic Contraction?

A

Force generated by the muscle is greater than the load to be lifted
Muscle shortens in length
e.g. Picking a book up off a table

33
Q

What happens during Eccentric Isotonic Contraction?

A

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

34
Q

What happens during Eccentric Isotonic Contraction?

A

Also occur to slow joint movement

Muscles undergoing heavy eccentric loading suffer greater damage when overloaded leading to greater muscle necrosis

Muscles are approximately 10% stronger during eccentric contractions than during concentric contractions

Principle behind body building

35
Q

The functional unit of skeletal muscle is the…

A

motor unit (MU)

36
Q

What is the Motor Unit composed of?

A

A single motor neuron
The group of muscle fibres innervated by it

37
Q

The number of muscle fibres per motor unit varies according to the _________ of the control required.

A

fineness

38
Q

What does the neuromuscular junction (NMJ), aka motor endplate do?

A

It is the connection between the muscle fibre and its motor neuron.
The membranes of the nerve and muscle cells come into close contact.

39
Q

When muscle fibre is stimulated at the NMJ it…

A

contracts.

40
Q

Maximal contraction (of a muscle) is when…

A

all MUs are firing together

41
Q

In practice to ensure that contraction is a smooth non-jerky process, __________________ of the motor units gives a graded response.

A

asynchronous firing

42
Q

A twitch is the…

A

brief contraction of the muscle fibers in a motor unit in response to an action potential.

43
Q

When does the latent period of muscle contraction happen?

A

(0.005 sec) between the stimulus and the first visible reaction

44
Q

When does the contraction period of muscle contraction happen?

A

(0.04 sec) when the muscle shortens

45
Q

When does the relaxtion period of muscle contraction happen?

A

(0.05 sec) the muscle returns to its original length

46
Q

After initial stimulation there is a short period during which muscle will not respond to further stimulus called the…

A

Refractory period

47
Q

Stimulation at frequency is…

A

shorter than the twitch time.

48
Q

When the second stimulus is being superimposed on the first it, results in a greater shortening of the muscle called _____________.

A

summation

49
Q

Summation in whole muscle can occur in two different ways, describe them.

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.

50
Q

As the (nerve) impulse frequency increases, the twitches become superimposed in…

A

wave summation

51
Q

Eventually increasing stimulus causes the successive contractions to fuse together in a state of maximal contraction called…

A

tetanus

52
Q

In _________ further increased stimulation will only result in very slight muscle shortening.

A

tetanization

MNSR - MCQ (5 decks)

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