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Physiology of Organisms > 9-11 > Flashcards

9-11 Flashcards

1
Q

What are Dynein and Kinesin?

A

The proteins that move along the microtubules

  • dynein is a dimer and moves towards the negative end of the microtubules—> towards the centrosome (nucleus) - in 9+2 stucture moves along neighbouring doublet of microtubule dragging the other to cause bending
  • Kinesin moves away from centrosome
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2
Q

Structure of microtubule

A

25nm across and made of α and β tubulin

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3
Q

Examples of movement mechanisms

x 7

A
  1. Outer hair cell motor
  2. Invertebrate photoreceptors
  3. ATP synthase
  4. RNA polymerase
  5. Flagella/cilia
  6. Actin/tubulin axonal transport
  7. Myosin/actin
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4
Q

Difference between parallel and series muscle unit structure

A

PARALLEL - each contract and force but then this is additive for each unit pulling so big force if parallel

SERIES - Adding contractile elements in series amplifies degree of movement as each segment shortens

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5
Q

Structure of muscle -

A

Myofibrils are bundles of protein filaments and then a group of myofibrils makes a muscle fibre (one single muscle cell) and then a bundle of fibres is a fascicle (sheathed in connective tissue) and then the whole skeletal muscle is multiple fascicles

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6
Q

What are the dark and light bands of striated (skeletal) muscle

A

Dark = A band = ANISOTROPIC

Light = I band = ISOTROPIC

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7
Q

Structure of a sarcomere

A
  • single contractile unit of a muscle cell
  • Z to Z line is 2 μm
  • middle is m line which is the middle of the H zone, in the middle of the A band
  • next to A band is I band and the Z line is in the middle of this
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8
Q

Structure of myosin

A

6 polypeptide chains

  • Main is two supercoiled α helices so dimer with 2 heads and then three of these dimers per section
  • the heads have the stiff neck with flexible hinge (each head has a ATP binding site)
  • cocked state is the high energy state
  • heads at 120 degrees and repeat every 43 nm
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9
Q

Structure of actin - F actin

A

G actin dimers into filaments

  • polarised with + and - ends
  • Tropomodulin at negative end
  • g dimers to + at 5-10 x faster than loss at -
  • 40nm sections and differ from 43 of heads of myosin - maybe purposeful desynchronisation (dont actually know why)
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10
Q

Other proteins of the thin actin filament

A

Tmod = tropomodulin at negative end

  • Tropomyosin - cover myosin binding sites - is a dimer
  • Troponin holds tropomyosin in place as its association is weak - moves it out of the way
  • nebulin but do not know of function
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11
Q

Troponin structure

A

2 subunits

TnI inhibitory element and binds to actin

TnT binds to tropomyosin

TnC binds to Ca2+ and this causes the troponin to make a lateral shift of tropomyosin

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12
Q

What is titin?

A

largest protein in genome

  • like a spring and maybe to protect against overstretching of sarcomere
  • half life of roughly 3 days so continuously repaired
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13
Q

Structure of sarcomere diagram (so can draw)

A

diagram

- twice as many thin filaments as thick

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14
Q

What visually changes to sarcomere during contraction?

A

I band shrinks but the A band is constant size

- H zone reduces as well

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15
Q

What is the cross-bridge cycle?

x 6

A
  1. ATP binds to myosin heads and so dissociates from actin
  2. Break to ADP and Pi which causes head to cock into high energy position
  3. head attaches to myosin site on actin and releases Pi (strengthens binding and activates power stroke)
  4. Power stroke
  5. ADP dissociates from myosin head
  6. ATP attaches to head to cause dissociation from actin
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16
Q

What causes the start of contraction?

A

Release of Ca2+ from sarcoplasmic reticulum
- binds to TnC which moves tropomyosin

  • force production rises rapidly for only a small rise in Ca2+
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17
Q

How do muscle fibres ensure Ca2+ gets to all sarcomeres?

A

invaginating membrane as otherwise diffusion would take too long

  • so near synchronous activation
  • done via t-tubules
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18
Q

Structure and purpose of t -tubules

A

90nm across and penetrate into fibre
- cause the shallow slope after depolarisation
- small and few ions
has Cl- ions to aid in repolarisation
- is K+ accumulates during intense activity can cause problems-volume

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19
Q

What is myotonia congenita

A

inherited condition which skeletal muscle goes into contracture
- chloride channel mutation of t-tubules

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20
Q

Where is Ca2+ stored?

A

sarcoplasmic reticulum

  • has a system where wraps around tubule system
  • in SR is calsequestrin which is a calcium buffer
  • calcium channels are ryanodine receptors
21
Q

Triadic regions of t tubules

A

two SR terminal cisternae either side of t-tubule in triad form
- t tubule dihydropyridine receptors are voltage sensors on surface of t tubule and line up with ryanodine receptors on both SR membranes so quick release of Ca2+ when membrane depolarisation

22
Q

What delays force production in muscles?

A

Ca2+ build in concentration and then the binding of 4 Ca2+ to troponin as require all 4 to be full activation

23
Q

What is SERCA

A

the pump that transports Ca2+ back into SR to stop muscle contraction
- activated when ca2+ released

24
Q

What does temporal summation of calcium concentration

A

tetanus from multiple action potentials and calcium cannot be taken up quickly enough between AP

25
Q

Describe a motor unit

A

the nerve and innervated muscle fibres

- and each motor unit can be low or high force by containing a smaller number of muscle fibres

26
Q

What is asynchronous activation?

A

Different motor units recruited one after another usually in order of size when force increases

  • controlled by central pattern generations
27
Q

What are muscle spindles?

A

Muscle spindles are proprioceptors that consist of intrafusal muscle fibers enclosed in a sheath
- they provide information on muscle length and positioning

28
Q

Cardiac muscle

A

striated with no tendons as pull on next cell (the intercalated disks)

  • contract around the chambers and the cells have gap junctions between then to allow for conduction between cells
  • part between two intercalated disks is a myocyte
29
Q

Smooth muscle

A

striation is less obvious and wrapped around vessels and organs

  • efficient and long lasting contraction
  • dont have an end plate, have gap junctions and are thin and spindle like cells
30
Q

Insect asynchronous muscle

A

contraction of antagonist muscle activates contraction in the muscle which then causes antagonist to contract

31
Q

atrophy vs hypertrophy

A 
at = disuse
hyper = with use
32
Q

What affects the speed of muscle twitches?

A

Temperature and the types of muscle fibre

33
Q

4 types of muscle fuel (providing atp)

A
  1. ATP store
  2. Phosphocreatine
  3. Lactic acid system
  4. Aerobic respiration
    GRAPH (pg 10 lecture14)
34
Q

How does phosphocreatine work?

A

can phosphorylate ADP to make more ATP

35
Q

What is VO2 max?

A

the max oxygen taken in per kg per minute

36
Q

What is myoglobin?

A

the oxygen binding protein in muscles similar to haemoglobin

- a lot in red muscle and not as much in white muscle

37
Q

Properties of slow oxidative fibres
- type 1 of red muscle
x 8 and example

A
  1. small diameter
  2. low force per area
  3. low Vmax
  4. low myosin ATPase activity
  5. High fatigue resistance
  6. A lot of mitochondria
  7. high oxidative capacity
  8. low number of oxidative enzymes
    example = postural muscles in humans
38
Q

Properties of fast oxidative fibres
- type 2 red muscle
x 8 and examples

A
  1. Medium diameter
  2. medium force per unit area
  3. medium Vmax
  4. High myosin ATPase activity
  5. medium fatigue resistance
  6. a lot of mitochondria
  7. high oxidative capacity
  8. medium number of glycolytic enzymes
    example is flight muscles in migratory birds
39
Q

Properties of fast glycolytic fibres
- white muscle
x 8 and examples

A
  1. large diameter
  2. high force per unit area
  3. high Vmax
  4. high myosin ATpase activity
  5. Low fatigue resistance
  6. Few mitochondria
  7. low oxidative capacity
  8. High number of glycolytic enzymes
    example is chicken breast
40
Q

The length-tension relationship for a whole muscle

A

graph

41
Q

Using a single fibre length to explain active tension relationship

A

graph

42
Q

What is isometric contraction

A

Tension increase but not movement so not work done

- lifting something that is too heavy

43
Q

What is isotonic contraction?

A

when the muscle shortens and there is the same tension throughout the movement
- bicep curl

44
Q

what is Work?

A

Work in joules is force x distance

- force is mass x acceleration

45
Q

How can isometric contraction still cause fatigue?

A

as no work but as there is tension then ATP is being used and therefore muscle fatigues

46
Q

What is power (watts)

A

joules per second = force x velocity

47
Q

Force velocity relationship

A

graph

48
Q

How do muscle shapes help alter mechanics of movement?

2 examples

A

different types of movement with different force and speed of contraction

  1. strap muscle like the bicep has lots of series elements and produces large movement with high velocity but low force
  2. unipennate like intercostal muscle with lots of parallel elements produce small movement with low velocity but high force

Physiology of Organisms (9 decks)

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