Brainscape's Knowledge GenomeTM

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


See full index

204: The Musculoskeletal System > Physiology of skeletal muscle contraction > Flashcards

Physiology of skeletal muscle contraction Flashcards

1
Q

How troponin works

A

4 Ca2+ bind to troponin C

TnC changes conformation

Conformational change in TnC shuts off TnI

Tropomyosin-troponin leaves F-actin groove

Unmasks the myosin binding site on actin

Next myosin heads make cross bridges to actin

  • myosin break down ATP
  • myosin pulls thin filaments
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Total TnI

A

Marker for total muscle breakdown

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

Cardiac TnI

A

Marker for myocardial infarct

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

Cross bridge cycling

A

Molecular cycle of actin-myosin interaction

Mechanism of contraction at molecular level

Contraction depends on binding of myosin heads to thin filaments (actin) at specific binding sites

In resting state of sarcomere, mypsin heads are blocked from binding to actin by tropomyosin, which occupies the specific binding sites

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

Cross bridge cycle reactions

A

Myosin releases actin

Myosin head cleaves ATP

Myosin binds actin

Power stroke

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

ATP, creatine phosphate and creatine phosphokinase

A

Creatine found in muscle fibres

  • phosphorylated to creatine phosphate
  • how energy is stored in muscle

When cross bridge cycling hydrolyses ATP to ADP+ Pi, creatine phosphate donates a high energy phosphate to ADP restoring it to ATP
- ATP levels must be kept stable- buffering and regeneration

Reaction is catalysed in both directions by the enzyme creatine phosphokinase

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

Creatine vs creatinine

A

Creatine is a small molecule that can accept high energy phosphate bonds from ATP

Creatine phosphate is the when phosphate has been added to it

Creatine phosphokinase is the enzyme that adds phosphate to creatine

  • plasma marker of muscle destruction
  • large molecule detected by antibodies

Creatine kinase is the same enzyme

Creatinine is a diagnostic marker of kidney function (breakdown product of creatine)

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

Two Ca2+ gradients

A

Extracellular vx cytosolic free Ca2+

SR vs cytosolic free Ca2+

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

Depolarisation leads to increase in Ca2+

A

ACH leads to depolarisation

Active nicotinic AChR leads to net inward current

Depolarisation spread via T-tubules

Local action potentials trigger Ca2+ efflux from terminal cisternae

  • across membrane of SR
  • into the fibre cytoplasm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Ryanodine receptor

A

In SR membrane

Releases Ca2+

From SR

Triggered by voltage sensor on Ca2+ channel

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

SERCA

A

In SR membrane

Pumps Ca2+ back into SR

Needs ATP

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

Tetany: molecular basis

A

A single AP -> Ca2+ release from SR -> twitch

Ca2+ ions are rapidly pumped back into SR -> end of twitch

Frequent APs -> insufficient Ca2+ resequestration -> summation of contraction

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

Two main types of muscle fibres

A

Slow twitch

  • type 1- red- oxidative
  • high myoglobin
  • many mitochondria

Fast twitch

  • type 2- white- nonoxidative
  • lower myoglobin
  • increase energy from glycolysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Fibre types differ in

A

Aerobic vs anaerobic

Faster calcium re-uptake

Maximum tension produced

Fatigue resistance

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

Distribution of fibre types

A

Muscles contain mixtures of fibre types, composition depends on muscle action

Soleus= 80% type 1 (slow), 20% type 2a

Vastus lateralis= mixture of type 1, 2a, 2x

Proportions depend on physical fitness

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

3 types of muscle coordination

A

Motor units
- recruitment and size principle

Tetany

Fusion of myocytes into long myofibres

17
Q

Definition of motor unit

A

A single alpha motor neuron and all muscle fibres it innervates

18
Q

Motor units

A

Function as a single contractile unit of skeletal muscle

All muscle fibres in a single motor unit are of the same type

19
Q

Motor units: variety

A

Large muscles responsible for powerful gross contractions, as single motor neuron may synapse on 1000 fibres

In small muscles mediating precision movement a single motor neuron may synapse with as few as 2-3 muscle fibres

Type and function of the lower motor neuron determines the muscle fibre

Different sorts of motor units in a single muscle

20
Q

Isometric contraction

A

Generates a variable force while length of muscle remains unchanged

21
Q

Isotonic contraction

A

Generates a constant force while the length of the muscle changes

22
Q

Concentric force generation

A

Force during contraction- tossing ball into air

23
Q

Eccentric force generation

A

Force during muscle elongation

24
Q

Proprioception

A

Controls force generation based on length and stretch

25
Q

Size principle

A

As the initial isometric contraction occurs:

  • more and more motor units are recruited
  • starts with smaller ones and progressively adds larger ones

Allows fine gradation of force for small movements

26
Q

Lower motor neuron disease

A

Weakness

Muscle atrophy

27
Q

Upper motor neurone disease

A

Spasticity

Hypertonia

28
Q

Stretch reflex

A

Controls muscle length

Increases muscle force

Lack of patellar reflex= Westphal’s sign

29
Q

Stretch reflex: patellar

A

Sensory= muscle spindle fibre

  • detects strethc
  • proprioception

Spindle is parallel to other muscle fibres

Ipsilateral spinal reflex

Monosynaptic

30
Q

Muscle spindle

A

Spindle consists of 3-12 intrafusal fibres

Gamma motor neurons increase sensitivity
- drive contraction of edge of intrafusal fibres

Spindle is like a thermostat that regulates the relationship between muscle length and muscle contractility

31
Q

Sensors from muscle spindle

A

Called type 1a and type 2

Wrap around the intrafusal fibres

Detect stretch of central non-contracting region using stretch receptors

32
Q

Absence of muscle spindle reflex

A

Westphal’s sign

Receptor damage

Femoral nerve damage

Peripheral nerve disease
- e.g. peripheral neuropathy

33
Q

Muscle spindle reflex in upper motor neuron disease

A

Can lead to hypertonia and spasticity

UMN inhibits normal descending inhibitory input to spinal interneurons

Spindle reflex becomes over sensitive

Can attempt to contract muscle all the time

34
Q

Tendon reflex

A

Protects from overloading

Decreases muscle force -> dropping the load

Sensor firing -> decrease contraction

  • sensor to spinal cord
  • interneuron to motor neuron
  • motor neuron inhibited
  • motor neuron to muscle
35
Q

Tendon reflex sensor

A

Golgi tendon organ

  • detects tension
  • in series with muscle
  • in tendon (near border with muscle)

Disynaptic

Ipsilateral spinal reflex

204: The Musculoskeletal System (23 decks)

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