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Human Physiology > W9 Muscular System > Flashcards

W9 Muscular System Flashcards

1
Q

Name the three different types of muscle?

Can you give an example of this?

A
  1. Skeletal - Bicep
  2. Cardiac - Heart
  3. Smooth- Small intestine
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2
Q

What are the functions of smooth muscle?

A
  1. Digestion
  2. Breathing
  3. Circulation
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3
Q

Smooth muscle have what kind of shape?

A
  • It has a fusiform shape (tapered at both ends)
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4
Q

Does smooth muscle have voluntary or involuntary contraction?

A
  • Smooth muscle has involuntary (slow wave motions)
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5
Q

How many nucleus’ does smooth muscle have?

A
  • Smooth muscle only has one centrally located nucleus
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6
Q

What does Cardiomyocytes mean?

A
  • Cardiomyocytes is just another word for cardiac muscle cells
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7
Q

What does cardiac muscle look like?

A
  • It is narrower and shorter than skeletal muscle
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8
Q

How many nucleus’ and mitochondria’s does cardiac muscle have?

A
  • It has one nucleus

- It has loads of mitochondria!

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9
Q

What supports the synchronised contraction of cardiac tissue?

A
  • Intercalated disks
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10
Q

What are intercalated disk and give the 4 distinct parts of them?

A
  • They are the ‘gap’ between cells membranes (allows electrical impulse from cell to cell)
    1. Z line of sarcomere (longitudinal structure of the tissue)
    2. Desmosome - Structural support
    3. Fascia adherent - mechanical support
    4. Gap junction - electrical synapses
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11
Q

Can you describe what skeletal muscle looks like?

A
  • Elongated muscle cell/myocytes (long structures)
  • It has multi nuclei
  • Striated (banded pattern (proteins))
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12
Q

What are the four characteristics of a skeletal muscle?

A
  1. Excitability
    - Capacity to muscles to respond to stimuli
  2. Contractibility
    - Ability to shorten to produce force
  3. Extensibility
    - Can be stretched to a limited degree beyond normal length
  4. Elasticity
    - Ability to recoil to original resting length following stretch
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13
Q

What are the four functions of skeletal muscle?

A
  1. Movement/locomotion
  2. Posture
  3. Stabilisation
  4. Generation of heat
    - Shivering
    - By-product
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14
Q

What causes indirect movement of skeletal muscle?

What is the insertion and origin of this?

A

Tendons/Aponeurosis

  • Immobile Bone (Origin)
  • Moveable Bone (Insertion)
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15
Q

What causes direct movement of skeletal muscle?

What is the insertion and origin of this?

A
  • Epimysium of muscle fused to Periosteum of bone

- Epimysium of muscle fused to Perichondrium of cartilage

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16
Q
  • What is myofibril?

- It contains two different types of filament. What are they and what do they contain?

A
  • It is a combination of proteins
  • Thick filement
    Mainly myosin
  • Thin filement
    Actin troponin & tropomyosin
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17
Q

What does Titin do?

A
  • It keeps thick & thin filament aligned resist muscle from over stretching and recoil muscle to resting length after stretching
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18
Q

What does nebulin do?

A
  • Anchoring actin to Z disc
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19
Q

What does Dystrophin do?

A
  • Anchoring protein
  • Actin to membrane via protein complex (sarcolemma)
  • Muscular dystrophy: weakening & breakdown of skeletal muscle
20
Q

Can you name the three different filaments in the sarcomere?

A
  1. Actin - thin
  2. Titin - elastic
  3. Myosin - thick
21
Q

What line separates each sarcomere?

A

The Z line separates each sarcomere

22
Q

What are the two components of a motor unit?

A
  1. Alpha-motorneuron

2. Muscle fibre innervated by the AMN

23
Q

What are the three types of motor unit?

A
  1. Slow = type 1 fibres
  2. Fatigue resistant = type 2a fibres
  3. Fast fatiguing = type 2x fibres
24
Q

What is Henneman’s size principle?

A
  • Motor units are activated in a sequence (1>2a>2x) which depends on the motor neuron size of the motor unit.
25
Q

What are some of the characteristics of type 1 fibres?

A
  • Slow contraction speed
    Adapted for aerobic respiration:
  • High myoglobin content
  • Large aerobic metabolism capacity and blood supply
  • High mitochondrial density and content/activity of oxidative enzymes
26
Q

What are some of the characteristics of type 2 fibres?

What are the two type 2 fibres?

A
  • Fast contraction speed
    Adapted for anaerobic respiration:
  • Less blood supply, myoglobin & mitochondria
  • High content of glycogen & glycolic enzymes
    1. Type 2a: fast oxidative fibres
    2. Type 2x: fast glycolic fibres
27
Q

What are the components of transverse tubules?

A
  1. Dihydropyridine Receptor (DHP) acts as a gate keeper
    - Voltage gated calcium channel
    - L type calcium channel
  2. Ryanodine Receptor
    - Which is mechanically coupled with actin
28
Q

What are Calsequestrin?

A

Glycoproteins

29
Q

What happens after the release of calcium?

A
  • Ca2+ binds to troponin (Tn-C) on the thin filament
  • Shifts tropomyosin off myosin binding sites
  • Enables myosin to bind to actin
30
Q

How many steps does the sliding filament mechanism have?

A
  • There are 5 steps
31
Q

Sliding filament mechanism:

- Can you describe Step 1?

A

Summary: The active site becomes exposed

  • At rest ATP molecules bind to myosin heads and having the enzyme ATPase on the myosin head hydrolyses ATP into ADP
  • This reaction releases energy that “cocks” the myosin head (pointing away from M-line) into a extended high energy position (ADP & Pi remain attached)
32
Q

Sliding filament mechanism:

- Can you describe Step 2?

A

Summary: Cross-bridge formation

  • “Cocked” myosin binds to active site on actin molecules (exposes E-C coupling process)
  • This is called the Cross-bridge.
  • Pi is released making bond stronger
33
Q

Sliding filament mechanism:

- Can you describe Step 3?

A

Summary: Pivoting of myosin head

  • Myosin releases ADP which bends myosin head and tugging actin along with it towards centre of sarcomere
  • This is called a Power Stroke
34
Q

Sliding filament mechanism:

- Can you describe Step 4?

A

Summary: Cross-bridge detachment

- A new ATP molecule binds to myosin head to release myosin from actin

35
Q

Sliding filament mechanism:

- Can you describe Step 5?

A

Summary: Myosin reactivation

  • ATP hydrolysis (by ATPase) cocks the myosin head again
  • Steps 3-5 are repeated (cross-bridge cycle) at a new active actin site further down the actin filament to shorten the sarcomere
36
Q

Where does the sliding filament mechanism occur?

A

It occurs in the sarcomere between the actin and myosin

37
Q

What is Calsequestrin?

A

Calmodulin is a glycoprotein

- It allows large quantities of calcium to be stored in the sarcoplasmic reticulum

38
Q

What does MLCK stand for?

A

Myosin light-chain kinase

39
Q

Calcium Kinetic Influencers:

- What decreases the activation metabolism of Ryanodine receptors (RyR)?

A
  • K+ & Na+
  • Increase Mg2+
  • Pi
  • Ca2+
40
Q

Contraction phase:

What receptor allows calcium to travel from the transverse tubules to the sarcoplasmic reticulum?

A
  • DHP or Dihydropyridine Receptor controls the voltage gated calcium channel
  • If open it can feed the actin in the sarcomere with calcium
41
Q

Contraction phase:

- What happens after calcium has accumulated in large quantities in the calsequestrin?

A
  • The calcium heads to the thin actin filament

-

42
Q

Contraction phase:
What happens during excitation contraction coupling?
(This is the process after calsequestrin)

A
  • So after calsequestrin the calcium heads towards the actin
  • Myosin binding sites are then exposed because of the calcium
  • Calcium sits in a specific location inside the actin
43
Q

Contraction phase:
How does the sarcomere change during a contraction phase?
(Specify on the bands & zones)

A
  • Actin slides over myosin
  • This pulls the Z line closer together
  • The A band stays the same
  • The I band decreases
  • The H zone disappears
44
Q

Contraction phase:

  • What is Calmodulin?
  • What is Calmodulin’s job role?
A
  • Calmodulin is a modulated protein
  • When calcium is released it binds to calmodulin
  • This then activates MLCK which increases the myosin ATPase activity
  • Therefore, creating muscle tension in a specific area
45
Q

Relaxation phase:

- What three components does calcium have to travel through to exit the filament?

A
  1. Sarco(endo)plasmic Ca2+ - ATPase which is released after the contraction
  2. This travels through the membrane proteins
  3. Lastly, it travels through the calcium & sodium exchange
    - This releases calcium into the extracellular fluids

Human Physiology (7 decks)

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