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NAS > Week 3 > Flashcards

Week 3 Flashcards

1
Q

What does syncytium mean

A

A multinucleate mass of cytoplasm resulting from fusion of cells
In skeletal muscles

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2
Q

What are intercalated discs

A

Join adjacent cardiac muscle cells together

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3
Q

What shape are smooth muscle nuclei

A

Spindle shaped

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4
Q

What is the sarcolemma

A

The plasma membrane of the muscle cell

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5
Q

What’s a myofibril

A

A chain of sarcomeres

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6
Q

What’s a myofilament

A

Contain the actin and myosin myofilaments

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7
Q

What is a sarcomere

A

The contractile unit

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8
Q

What is a triad

A

A special internal membrane system that controls muscle contraction by regulating calcium release

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9
Q

How does the skeletal muscle triad work

A

The sarcoplasmic reticulum Ca2+ channel protein lines up with the Ca2+ channel protein in the t-tubular system
Depolarisation of the t-tubular system causes opening of the SR calcium channels
Calcium which is held in the SR lumen by calsequestrin (calcium binding protein) can then be released into the muscle cytoplasm (cytosol/sarcoplasm)

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10
Q

What are the 3 major types of skeletal muscle fibres

A

Red fibres
Intermediate red
White

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11
Q

What are red fibres

A

Contract slowly, do not fatigue quickly, low glucose metabolism
Red colour from high levels of myoglobin
Maintenance of posture e.g. back muscles

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12
Q

What are intermediate red fibres

A

A combination of red and white fibre characteristics
Contract quickly intermediate rate of fatigue and glucose metabolism
Seen in big leg muscles

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13
Q

What are white fibres

A

Responsible for rapid contraction
Contract quickly and fatigue quickly, high glucose metabolism (including anaerobic)
Little myoglobin content
Seen in muscles that move the eye

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14
Q

Why is the motor system of the body important

A

Set muscle (or motor) tone of the body
Bring about voluntary movements

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15
Q

What is a motor unit

A

Defined as a somatic efferent plus all the muscle fibres it supplies
The combination of an individual motor neuron and all off the muscle fibres it innervates

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16
Q

What does a motor unit comprise of

A

1 a-motoneurone
All extrafusal muscle fibres it supplies
Extra-ocular muscles and quadriceps

17
Q

What are structural components of the motor system

A

Motoneurones
Skeletal muscles
The neuromuscular junction

18
Q

From what part of the nervous system do motoneurones originate

A

Efferent systems
Somatic motor efferent (or upper motoneurones)
A-motoneurone (or lower neurones)

19
Q

Why are skeletal muscles important

A

Movement
Posture
Heat generation
Stability of joints

20
Q

What is a myocyte

A

The single cell of muscle

21
Q

What is a fascicle

A

A group of myocytes
Fasciculi collect to form a muscle

22
Q

What is the endomysium

A

The connective tissue sheath enveloping a myocyte

23
Q

What is the perimysium

A

The tissue sheath enveloping a fascicle

24
Q

What is the epimysium

A

The tissue sheath enveloping all fascicles of a muscle and its neurovascular bundle

25
Q

What is a tendon

A

An organised tough band of fibrous connective tissue mass that forms a point of confluence of contraction by single myocytes of a muscle
Brings together single contractions of myofibrils hence myocytes to produce combined actions at a single point

26
Q

How are skeletal muscles classified

A

According to architecture of their fascicles

27
Q

What are common assemblies of fascicles

A

Convergent muscle
Strap muscle
Circular muscle (also known as sphincteric muscle)
Fusiform muscles
Pennated muscles - unipennate, bipennate, multipennate

28
Q

What are the two types of motoneurone

A

Upper motoneurone
Lower motoneurone

29
Q

What is the lower motoneurone responsible for

A

Transmitting the signal from the upper motor neurone to the effector muscle to perform a movement
Three main types- somatic motor neurons, special visceral efferent (branchial) motor neurons, general visceral motor neurons

30
Q

What are upper motor neurones responsible for

A

They’re first order neurons which are responsible for carrying the electrical impulses that initiate and modulate movement

31
Q

Characteristics of muscle fibres of motor unit

A

Have the same physiological profile- contraction speeds, susceptibility to fatigue
Have the same histochemical profile- myosin fibre typing, enzyme expression profile, metabolic profile

32
Q

The characteristics of the motor unit allow for

A

Uniform development of force throughout muscle
The nervous system to regulate the rate and speed of contraction of movements it may choose
Muscle contraction to be distributed throughout the muscle

33
Q

Muscle fibres can be classified into 3 categories according to

A

How quickly they develop force
How long they take to relax

34
Q

What are the 3 broad types of muscle fibres

A

Fast twitch type FF
Intermediate twitch type FR
Slow twitch type S

35
Q

What is a neuromuscular junction

A

A specialised synapse
Between a motor neuron and a muscle cell
Tuned for rapid reliable neurotransmission

36
Q

Role of Ca2+ in excitation-contraction coupling

A

Calcium conc. higher inside than out
Action potential in presynaptic terminal
Depolarisation opens voltage-gated Ca2+ channels
Ca2+ enters presynaptic terminal
Fusion of vesicles with presynaptic membrane
Acetylcholine ACh released (exocytosis)

37
Q

Ca2+ induced vesicle fusion

A

Calcium entry into presynaptic terminal triggers vesicle fusion
Ca2+ sensor in synaptotagmin
Change in conformation on Ca2+ binding triggers vesicle fusion
Exact mechanism is unclear

38
Q

How are skeletal muscles classified

A

By the architecture of their fascicles

39
Q

Motor unit characteristics

A

The motoneuron determines the characteristics of the muscle it innervates
Same muscle type as neurone connected

NAS (12 decks)

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