Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Primary Physiology > Muscle Physiology > Flashcards

Muscle Physiology Flashcards

1
Q

Functions of muscle

A

Support
Mechanical response to stimuli
Posture and movement
Store of glycogen and glucose
Store of protein
Thermoregulation (shivering)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Types of muscle

A

Skeletal
Cardiac
Smooth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Macroscopic layers of skeletal muscle

A

Surrounding epimysium around belly of muscle
Fascicles made up of bundles of muscle fibres surrounded by perimysium
Individual fibres made of myofibrils surrounded by endomysium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the generic pattern of nerve supply to most muscles

A

Single nerve ending at centre of muscle belly.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the surroundings of an individual muscle cell called
What does it consist of?
Special feature with function

A

Sarcolemma
Lipid bilayer membrane and polysaccharide/collagen outer layer
Deep penetrating invaginations called t tubules allow surface depolarisation to reach deep myofibrils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What’s the general structure of the inside of a muscle cell?

A

Sarcoplasm (specialised cytoplasm)
Myofibrils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is special about contents sarcoplasm

A

Many mitochondria
Sarcoplasmic reticulum - intracellular store of calcium wound around myofibrils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Structure of a skeletal muscle myofibril
Bands/lines (name and parts)

A

Adjacent actin and myosin termed sarcomeres
Terminal z line separating blocks
I band (just actin)
A band (actin and myosin overlapping)
H band (just myosin in middle of adjacent A bands)
M line in middle of H band
Then reflected on other side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where in the banding of a sarcomere are t tubules found

A

2 per sarcomere found at ends of h bands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What holds actin and myosin together in their side by side arrangement

A

Large protein call titin,

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What makes up skeletal muscle thin myofilaments
Layout

A

Two molecules actin
Helical wrap of tropomyosin
Every half turn of tropomyosin is bound troponin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What subgroups make up skeletal muscle troponin

A

I, T, C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What makes up the thick myofilaments of skeletal muscle
Structure
Relationship to sarcomere bands

A

Myosin molecules (each with long tail and 2 short heads) packed together in helical bundle
Each head sticking out between actin chains
Tail region is h line

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Overview of sequential steps of skeletal muscle contraction

A

Nerve action potential - depolarising of end plate and release of acetylcholine
Acetylcholine binds with receptor on muscle causing sarcolemma depolarisation
Depolarisation spreads over muscle and down t tubules
Depolarisation releases calcium from sarcoplasmic reticulum
Calcium binds to troponin C, tropomyosin releases from the actin exposing binding site
Myosin binds to actin repeatedly causing sliding of the fibres and shortening of muscle
Calcium pumped back into sarcoplasmic reticulum, tropomyosin re binds and contraction stops

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the term for the linkage between nerve cell depolarisation and muscle cell contraction

A

Excitation contraction coupling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Anatomy of a neuromuscular junction

A

Flattened unmylinated nerve terminal
Junctions gap
Thickened convoluted folded sarcolemma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Physiological process when action potential reaches nerve end terminal at NMJ until receptor binding.

A

ACh containing vesicles fuse with cell membrane releasing ACh into junctional gap
ACh diffuses across gap and binds to nicotinic ACh receptors on sarcolemma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Ratio of ACh released from neurone vs number of receptors that need activating on muscle
Consequence

A

10:1
Reliable neurotransmission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Structure of nicotinic ACh receptor

A

5 membrane spanning sub units
2 alpha, 1 beta, 1 delta, 1 gamma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Activation and consequence of nicotinic ACh receptor

A

ACh binds to alpha subunit
Conformational change opens pore
Na enters cell rapidly down concentration gradient
Muscle membrane depolarisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Physiology of myofibril depolarisation and action potential
Resting potential, duration, speed

A

Similar to neurone however:
Resting potential -90mV
AP lasts 2-4ms
Travels around 5m/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the collective term for sarcolemma, t tubules and sarcoplasmic reticulum

A

Sarcotubular triad,

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How does a myocyte AP result in calcium release

A

Activation of dihydropyridine receptor in sarcolemma - voltage sensitive calcium channel
Sensing of this by direct contact with ryanodine receptor on sarcoplasmic reticulum membrane - again calcium channel when open
Calcium moves into cell and out of SR down concentration gradient into sarcoplasm

24
Q

Clinical correlation of ryanodine receptor in anaesthesia

A

Mutations responsible for malignant hyperthermia
Dantrolene is a ryanodine receptor inhibitor

25
Q

How is positive feedback involved in myosin binding to actin

A

Calcium binds to troponin C causing conformational change of I and T
Troponin dissociates and tropomyosin moves exposing myosin binding site.
Binding of myosin then causes further displacement of tropomyosin and more binding sites exposed encouraging further cross bridging.

26
Q

How do the myosin fibres move over the actin fibres once bound?
How is atp involved

A

Binding to actin causes conformational change in myosin causing head to move backwards resulting in movement of fibres
ATP binds to actin myosin complex causing disconnection of actin and calcium release
ATP hydrolysed on myosin leaving attached ADP and pi with potential energy
Calcium binds - myosin reattaches to actin
Power stroke occurs and adp and pi released
Then back to top

27
Q

How do muscles produce a sustained contraction

A

Calcium pumps always pumping back into sarcoplasmic reticulum, however, repeated depolarisations cause it to increase faster than it can be cleared resulting in maximum power.

28
Q

What is a skeletal muscle motor unit

A

The muscle cells Innervated by a single motor unit

29
Q

How do muscles differ between fine control and course strength

A

Small motor units for fine control

30
Q

How are multiple motor units in a muscle recruited in a contraction

A

Henneman’s Size Principle
Small motor units first followed by large units, allowing a graduated response and preserving fine control at beginning of response.

31
Q

What limits duration of continuous whole muscle contraction?

A

Glycogen store in muscle
Decreased firing rate of nerve cells
Reduction of blood supply through contracted muscle with diminishing oxygen supply

32
Q

How is muscle tone maintained

A

Low frequency discharge from motor nerve fibres using feedback from spindle fibres maintaining part state of contraction

33
Q

How does rigour mortis occur
What stops it

A

Sarcoplasmic reticulum calcium pumps stop working and so ca levels continue to dissociate tropomyosin from actin
There is no atp available to release myosin head from actin

Stopped as autolysis breaks down muscle proteins

34
Q

Types of skeletal muscle fibre and characteristics

A

Type 1a - red, slow twitch, high blood supply, myoglobin and mitochondria, low glycogen, slow to fatigue
Type IIa - red, moderate twitch, high blood supply, myoglobin and mitochondria, medium glycogen, slow to fatigue
Type IIb - white, fast twitch, low blood supply myoglobin and mitochondira, high glycogen, fast to fatigue

35
Q

Which sort of muscle fibres atrophy with age most

A

Red fibres

36
Q

What is the function of the muscle spindle system?
What are they

A

Provides background tone and modulation for accurate movements
Fusiform sensory structures located within each muscle belly

37
Q

What signals do muscle spindle fibres relay?

A

Static - muscle length
Dynamic - stretch, rate of contraction

38
Q

What happens on muscle spindle stretch
with nerve type

A

Stretch sensitive ion channels open,
Depolarisation
AP in Ia and IIa sensory nerves
1a sensory fibres monosynaptically synapse with alpha motor neurones triggering the muscle to contract opposing the stretch, also trigger inhibitory neurones to antagonistic muscle.
IIa nerves are used in proprioception
CNS trigger gamma efferent system to the spindle effecting their tension and thus tone of the muscle

39
Q

What are golgi tendon organs
Mechanism including nerves
Function

A

Encapsulated nerve endings wrapped around tendon just distal to muscle insertion
Sense tension in the muscle resulting in a polysynaptic inhibitory discharge via 1b nerve fibre, interneurone then alpha motor neurone back to muscle in question.
Function is to protect muscle from too much tension/equalisation of tension between muscles

40
Q

How is atp created

A

Phosphorylation of adp by creatine phosphate
Glycolytic phosphorylation
Oxidative phosphorylation in mitochondria

41
Q

What are the features of adp creation by creatine phosphate

A

Immediate supply of energy but depletes in a few seconds
Used in explosive movement
Produces creatinine waste
Regenerated during relative rest

42
Q

Features of glycolytic phosphorylation creating atp

A

Occurs in cytoplasm
Glycolysis creates pyruvate
Anaerobic and inefficient
Lactic acid waste product
May sustain contraction for a few minutes

43
Q

How long do intracellular stores of glycogen last to provide for muscle contraction

A

10 minutes

44
Q

What provides energy to muscles after glycogen exhausted

A

Blood glucose and fatty acids for first 40 mins then just fatty acids

45
Q

What is the energy efficiency of muscles? Where does the rest go?

A

25%
Heat

46
Q

What is smooth muscle
Locations

A

Involuntary muscle under control of autonomic nervous system
Found in viscera and blood vessel walls

47
Q

Types of smooth muscle

A

Single unit - all contracts as one (most)
Multi unit - individual cells may contract alone (eg iris of eye, large arteries)

48
Q

Differences between smooth and skeletal muscle

A

Smooth is:
Non striated
Smaller cells
Cluster rather than in parallel bundles
Different activation mechanism

49
Q

How is the contraction mechanism of smooth muscle different to skeletal
Implications

A

Contractile fibres anchored to dense bodies on the membrane or in cytoplasm rather than z discs
Myosin in bundles with heads in different direction
More actin less myosin

Can contract to much shorter lengths (up to 80% reduction resting length)

50
Q

How does the muscle action potential differ in smooth vs skeletal muscle

A

In smooth muscle depolarisation directly opens voltage gated calcium channels in cell membrane and depolarisation largely as a result of this rather than sodium .

51
Q

How does calcium mediated activation of contraction occur in smooth muscle

A

Ca binds to calmodulin in cytoplasm
Calmodulin activates myosin light chain kinase causing cross bridging and cycling
NO troponin in smooth muscle cells and tropomyosin is present but function unknown.

52
Q

What are the implications of the poor ATPase function of smooth muscle myosin vs skeletal muscle?

A

Stronger contraction per cell but slower

53
Q

How do smooth muscle cells go to cause waves of depolarisation such as peristalsis

A

All smooth muscle cells have unstable resting membrane potential
In isolated cells causes irregular contractions but in large bodies of cells results in waves of depolarisation through adherens junctions
Can be triggered by physical stretch - an important factor of auto regulation in blood vessels

54
Q

What happens if smooth muscles are tensioned and held at longer length

A

Tension in muscle gradually decreases - plasticity

55
Q

What can modify smooth muscle contractions

A

Autonomic nervous system
Hormones (eg progesterone causing relaxation)
Local humoral factors (e.g. calcium concentration in ECF)

Primary Physiology (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions