neuro establishing membrane Flashcards

1
Q

b. A + B–> E –>AB

A

cell needs to have the right substrates and molecules in order to perform this reaction

all about protein synthesis and the role of the membrane

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2
Q

cellular physiology begins with access to the internal environment when a cell is

A

Selective permeable

at the membrane

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3
Q

describe membrane structure

A

i. Phospholipid bilayer oriented so heads are exterior and interior surfaces of the membrane; tail groups are directed inward towards the center of the membrane

hydrophobic inner

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4
Q

Fluid Mosaic Model)

A

describe membrane proteins that are relatively free to float around in the membrane and they can concentrate in certain areas of the membrane if needed

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5
Q

types of movements allows by phospholipid bilayer

A

simple and facilitated (you need a transport molecule to bind)

diffusion can be facilitated

this is how glucose moves

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6
Q

b. Factors that affect diffusion and diffusion rate:

A

i. Permeability (P) of the membrane
ii. Area: D = PxA
iii. Concentration Difference D(Co-Ci)

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7
Q

diffusion as it relates to permeability and area

A

a. Diffusion = permeability x area

size of a gradient also impacts net diffusion

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8
Q

V. When does movement of substances across selectively membrane stop?

A

Diffusion proceeds to equilibrium, NOT equal concentrations

If only one substance and no concentration gradient, then your net diffusion will be 0 but usually other forces and molecules in play

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9
Q

An _________ can make charged particles move in the absence of a concentration gradient

A

An electric potential can make charged particles move in the absence of a concentration gradient

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10
Q

VI. Nernst Potential

A

Find the equilibrium point for an ion in solution when there is a semipermeable membrane that is permeable to that ion

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11
Q

equilibrium potential

A

should be able to apply a positive charge that would counteract diffusion or concentration gradient

allows us to figure out the electrical current at which point the system would be in equilibrium

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12
Q

Nerst equation only works with what types of ions

A

univalent

so not Ca (2+)

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13
Q

osmotic pressure is created with

A

non diffusible elements on either side of the membrane

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14
Q

osmole is

A

the molar content of non diffusible elements

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15
Q

what is needed to phosphorylate enzymes

A

i. Need ATP to phosphorylate enzymes

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16
Q

In nerve and muscle physiology, this is important for establishing the concentration gradient that we need to use to create that electric voltage we need across the membrane

A

Na/K pump

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17
Q

functions of Na/K pump

A

Helps maintain osmotic balance

Electrogenic (separates charge unevenly and creates potential for electrical current)

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18
Q

step 1 of Na/k pump

A
  • takes in 3 Na molecules, which are bound to the protein.
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19
Q

step 2 of Na/k pump

A

ATP phosphorylates alpha subunit, stimulating conformational change

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20
Q

step 3 of Na/k pump after ATP phosphorylates alpha subunit, stimulating conformational change

A

Pump open to outside, ready to start second half of cycle

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21
Q

step 4 of Na/k pump after

Pump open to outside, ready to start second half of cycle

A

2 K accepted from outside

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22
Q

step 5 of Na/k pump after

2 K accepted from outside

A

dephosphorylation stimulates conformational change

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23
Q

step6 of Na/k pump after . dephosphorylation stimulates conformational change

A
  • 2 K expelled to inside; pump returns to initial state
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24
Q

Na/k pump helps establish what charge

A

So moving 3 Na+ out, and 2 K+ in =net positive charge outside and net negative charge inside

this is a membrane phenomenon
remember sodium concentrations 134-145

whereas K 3.5-5

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25
Q

Active Transport Mechanisms: Secondary

A

spend ATP to set up gradient that allows us to move molecules in the same or opposite directions

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26
Q

imbalance of charge is a form of

A

“potential” energy

relative difference of electrical charge between the two sides of the membrane

diagram of pulling back the bow from the arrow

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27
Q

forces at play with a cell and how they relate to NERST

A

membrane is relatively permeable to potassium

Na/k creates high intracellular K

flux of K ions would want to move out but

electrostatic pressure: outside is more positive and this is a repelling force that keeps

as the ion is fluxing the concentration gradient is reducing diffusion pressure

NERST looks at the balances of these and looks at where you can apply an electrical current to stop the flow of ions even if the concentration is not equal

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28
Q

EMF =

A

electro
motor force

voltage that you have to apply to prevent the movement of ions

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29
Q

C1/C2

A

concentration inside and outside of the cell

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30
Q

Factors effecting diffusion potential

A

Polarity of each ion involved is important

Permeability of membrane for each ion

Concentration difference of each ion across membrane

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31
Q

Modified Nernst for multiple ions

A

: Goldman-Hodgkin-Katz equation

Calculates the membrane potential at rest given the different concentration gradients

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32
Q

GHK equation accounts for

A

Considers concentration differences of the ions most responsible for the membrane potential

Considers permeability because ions can only contribute to membrane potential if the membrane allows it/if they can diffuse

chloride and it’s negative charge is accounted for

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33
Q

GHK tells us

A

can us it to calculate the membrane potential at rest given the different concentration gradients

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34
Q

ions can only contribute to membrane potential if the membrane allows it/if they can _______

A

ions can only contribute to membrane potential if the membrane allows it/if they can diffuse

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35
Q

b. Voltage across membrane referred to as __________

A

b. Voltage across membrane referred to as “membrane potential”

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36
Q

c. In nerve cells, typically the membrane potential is

A

c. In nerve cells, typically -60- -90mV

Inside of the cell is more negative than the outside

remember the picture of the capacitor this is how the membrane acts

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37
Q

Factors influencing membrane potential

A

a. Activity of the Na/K pump
b. Membrane leak/Permeability
c. Effect of leak on membrane potential can be inferred from Nernst potential for each ion involved
d. Hyperpolarization by ATPase

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38
Q

If membrane only leaky to 1 of the ions, then that ion is going to….

A

If membrane only leaky to 1 of the ions, then that ion is going to move the membrane potential towards its own reversal potential

is i make the membrane permeable it will move the concentration toward equilibrium and it’s own reversal potential

can use the NERST to calculate where the potential would go in this case

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39
Q

membrane gets re-polarized by the

A

i. Gets repolarized by the ATPase

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40
Q

a. Vk

A

nerst potential/reversal potential for K is pretty negative

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41
Q

Vna

A

membrane potential is very positive; if open channels for Na, then it’s going to rush in to the cell

what this tells you is that Na is oging to rush into the cell

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42
Q

Vm

A

membrane potential is close to K’s reversal potential b/c of the leakiness to K, tending to keep the membrane near its own reversal potential

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43
Q

describe AP

A

When some threshold is reached, massive opening of Na channels and the membrane potential is driven towards the reversal potential for Na which is positive so you have the upstroke

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44
Q

when the membrane potential is drive back down this is an example of what physiological process

A

then slower K channels open and the membrane potential is driven back downward towards resting potential (downstroke)

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45
Q

skeletal m accounts for what %

A

a. 40% of the body

i. Move our skeleton

46
Q

skeletal muscles are specialized only to

A

b. Can only contract

Muscle can either extend or flex a joint (it can’t do both)

47
Q

Individual cells contain contractile protein calles

A

Individual cells contain myofibrils

myofibirls are bundled together as fibers and fasciclesc

48
Q

skeletal muscle is arranged in big bundles called and little bundles called

A

a. Bundles (fascicles) of bundles (fibers)

49
Q

Myofibrils bundled together as ___ and these are bundled together as_____

A

i. Myofibrils bundled together as fibers. Fibers bundled together as fascicles

50
Q

this surrounds muscle cell

A

c. Sarcolemma surrounds muscle cell

51
Q

Myofibrils are contractile elements containing _______

A

d. Myofibrils are contractile elements containing myofilaments

52
Q

Mitochondria what % of skeletal muscle

A

e. Mitochondria (2% in skeletal)

53
Q

this stores calcium

A

f. Sarcoplasmic reticulum stores calcium

54
Q

______lines the surfaces of the fascicles

A
  1. Epimysium lines the surfaces of the fascicles
55
Q

myofilaments

A

actin (thin)

myosin (thick)

56
Q

a small purple protein which coil around the coil of actin protein

A

i. Tropomyosin

57
Q

sit attached both to actin and tropomyosin molecules

A

ii. Troponin

58
Q

describe the arrangement of actin

A

helical coil of actin subunits. Actin arranged in long polymers, 2 long polymers are coiled around each other with a particular frequency

59
Q

describe the arrangement of myosin

A

Myosin has head groups w/ 2 hinges (one hinge at the attachment of the head group and one lower down near the tail region)

60
Q

skeletal muscle contraction always begins with

A

a. Begins with stimulation by nervous system in skeletal muscle

61
Q

Motor unit

A

Individual motor nerve fibers and all of the muscle fibers that are innervated by that nerve

if you have a muscle with a lot of smaller motor units you have a lot more options

62
Q

larger muscles have what type of motor untis

A

ii. Larger muscles that move the limbs have big motor units - you don’t require fine movement with the limbs
1. Each individual neuron can stimulate a lot more individual muscle fibers. So motor units are fewer but bigger

63
Q

smaller muscles have what type of motor units

A

iii. Smaller muscles have small but numerous motor units - required for dexterity

64
Q

contents at NMJ of skeletal muscle

A

iv. The contents here at the NMJ is Ach, it diffuses across the space. Across the gap Ach will bind to a receptor on the postsynaptic membrane/motor end plate

takes two Ach to open the channel

65
Q

what type of ion channel controls AP of skeletal muscle

A

This is ligand gated channel and it is a positive ion channel

it will allow Na to flux into the cell and drive the membrane potential towards Na’s reversal potential = Action potential

66
Q

what type of ion flux mediates the release of Ach in the NMJ

A

When electrical charge comes down the membrane, you see a Ca++ flux that mediates the movement of vesicles to the

67
Q

Sarcoplasmic reticulum releases its store of ______ under the influces of

A

releases store of Ca under the influence of …?

68
Q

b. Union between nervous and muscular systems

A

NMJ

uses AcH AS nt AND BINDING RECEPTOR usually triggers an AP and causes release of Ca from sarcoplasm

69
Q

Protein heads of myosin are known as the____ and they extend away from the body of the filament

A

Protein heads of myosin are known as the cross bridges and they extend away from the body of the filament
Myosin, each molecule is composed of 6 polypeptide chains
i. Head region and a tail region

70
Q

Actin (thin) filaments made of 2
helically coiled ______

these strands are made up of _____ which is attached to one ADP

A

Actin (thin) filaments made of 2 helically coiled F-actin strands

F-actin strands made of G-actin which is attached to one ADP

71
Q

when in contraction actin filaments are closer to the center of the the

A

Contracted state where actin filaments are closer to the center of the sarcomere where they are drawn that way by the thick filaments

72
Q

Troponin made of 3 protein subunits

name them and what they bind to

A

i. TI binds actin
ii. TT binds tropomyosin
iii. TC binds calcium

73
Q

Ca is where waiting to be released under what condition

A

Ca is in the SR waiting to be released when a muscle undergoes an action potential)

74
Q

how does troponin tropomyosin complexes work

A

Troponin/tropomyosin complexes inhibit binding of cross bridges by physically blocking binding sites that the myosin head groups want to attach to when the muscle is at rest

k. When AP comes down the membrane of the muscle cell, the voltage gated Ca channels release the store of Ca.

Ca binds to its binding site on the Troponin complex (TC subunit)

this will release the myosin heads so they can bend and pull the ends of the sarcomere togehter

75
Q

role of ATP in muscle contraction

A

ATP binds to the head of the myosin cross bridge and it is hydrolyzed and causes myosin head group to reset to its open posture
i. Open head group has the separated ADP and Pi (hydrolyzed pieces of the ATP still attached)

this is stored energy from the hydrolyses of ADP

76
Q

when is the myosin head at thigh energy configuration

A

when the aDP and P (hydrolyzed aDP) are attached to the head group and reset to an open posture

here it can attach and close and a new ADP will take the place

77
Q

Increasing tension developed with stretch (maximum at approx. 110% of normal sarcomere width)

is characteristic of single or whole m fibers

A

single

Tension limited by the ends of the myosin filaments

If you go beyond the 110% you lose the amount of tension you can develop

78
Q

Shortening sarcomeres does what to tension

A

limits tension as z-lines contact myosin filaments

79
Q

energy required for contraction

A

a. ATP required in large amounts
b. Muscle sequester short supply
c. ADP must be phosphorylated and returned to high energy ATP state to keep the muscle moving

80
Q

how do we phosphorylate ADP

A

a. Creatine phosphate
b. Glycogen:
c. Creatine Synthesis

81
Q

i. Can phosphorylate very quickly but can’t keep up for very long
ii. Tends to be the first thing we draw on when we contract muscle

A

a. Creatine phosphate (phosphocreatine) stored in muscle provides, fast but short-lived source of phosphate. Stored in levels about 5x greater than raw ATP

82
Q

when do we utilize glycogen for muscle contraction

A

glycogen takes longer but will mobilize and take over for creatine phosphate

83
Q

The Mother Lode of ATP

A

a. Oxidative phosphorylation:

dietary sugars broken down first through glycolysis and the Krebs cycle then combine with oxygen as part of an enzymatic cascade producing ATP in large numbers as a by-product

84
Q

c. Creatine Synthesis

A
  1. Comes from arginine in the kidneys then goes through a few steps in the liver to form creatine. Creatine is phosphorylated by creatine phosphate into creatine phosphate which can give off the phosphate molecule to phosphorylate ADP
85
Q

compare ATP pathways

greatest to lowest

A

a. CP: 4M/min ATP produced by phosphorylation through creatine phosphate but it lasts only for seconds
b. Glycogen/lactic acid (anaerobic): 2.5M/min for minutes
i. Glycogen pathway is anaerobic and it leads to lactic acid production
c. Oxidative phosphorylation: 1M/min of ATP as long as the food holds out!
i. You can do this forever as long as there is fuel in the machine

86
Q

Isometric relates to what development of tension

A

“same length.” Tension = Load

generate tension without shortening the lengt

87
Q

isotonic contraction

A

Tension > load

i. Muscle tone remains the same throughout, tension is greater than the load
ii. Ex - when you pick something up

88
Q

smooth contraction when you pick something up is isotonic
isometric
or lengthening

A

c. Isotonic = Tension > load

Muscle tone remains the same throughout, tension is greater than the load

89
Q
  • if you try to pick up something you can’t hold

you will have what type of contraction

A

d. Lengthening contraction = Tension < Load
ii. Muscle starts to lengthen under the load but it still develops tension

but still develops tension

90
Q

large fibers, very strong fibers

A

a. Fast Fibers

Large SR = large, fast ion release. Large supply of glycolytic enzymes.

91
Q

oxidative metabolism with fast fibers

A

Oxidative metabolism less important, blood supply reduced, fewer mitochondria. Fatigue quickly.
i. Can generate a great deal of strength quickly but fatigue quickly

92
Q

smaller, more extensive blood supply, increased mitochondria, large myoglobin content, slow fatiguing.

A

small fibers

93
Q

small fibers fatigue how compared to fast

A

more slowly but they generate mroe tension

94
Q

changing contraction by summing motor unit activity over time and its done by altering the frequency of stimulating APs

A

XVIII. Temporal Summation

95
Q

changing contraction by summing motor unit activity over time and its done by altering the frequency of stimulating APs

A

XVIII. Temporal Summation

96
Q

recruitment of muscle fibers

A

i. Smaller motor units contract first, but with growth of signal strength, larger motor units are recruited (smaller motor neurons are more excitable)
1. Larger motor units need a bigger signal to contract
2. Nerves for small motor units are generating AP first

97
Q

a. At some level contractions fuse into state of sustained contraction referred to as ______

A

a. At some level contractions fuse into state of sustained contraction referred to as “tetanus.”
b. Nearly every movement involves tetany

98
Q

staircase effect of muscle contraction

A

b. Step like increase in strength of contraction after period of rest (staircase effect). May occur due to flooding of the sarcoplasm with calcium
i. Period of rest gives SR to accumulate more Ca so it releases more Ca next time it is stimulated

99
Q

smooth tension with contraction is maintained by

A

we alternate motor untits

100
Q

what is muscle tone

A

a. Resting tension on the muscle

Results from low baseline rate of nerve impulses from the spinal cord causing low level of release of NT which sets muscle tone and provides trophic effect which provides bulk of your musculature

101
Q

fatigue increases in proportion to the loss of

A

a. Increases in proportion to the loss of glycogen stores
b. Transmission of nerve impulses at the NMJ also reduced after prolonged stimulation due to inability to keep up with the recycling of the NT

102
Q

muscle must cross what?

A

a. Muscles apply tension at insertion points on bone
b. Work with joints to affect movement of the skeleton
i. Muscle must cross a joint

103
Q

how does muscle tension work as a lever system

A

Force related to the distance of the attachment from the fulcrum, the length of the lever arm to be moved and the original position of the lever.

The finger representing the attachment point and at a great distance from the lever in order to be able to lift the mass. We can’t do that in our body.

104
Q

how is bicep strength limited

A

Our biceps is not attached at a great distance from the elbow so it limits the strength that can be generated. If it was attached at the wrist, that would allow for a lot more strength

105
Q

how do muscles change

fibers?

sarcomeres?

A

a. Almost continuous process
b. Fiber number changes rare
c. Fiber hypertrophy by addition of myofibrils
i. When you exercise, your muscle gets bigger
d. New sarcomeres added with stretch
e. Increase in metabolic enzyme and glycogen storage, blood supply with sustained aerobic activity

106
Q

why do we have atrophy with the loss of innervation

A

when you lose innervation of the muscle, you lose the trophic effect of the constant low level of NT that is released so

107
Q

what happens when we have de-innervation of a muscle

A

b. Most fibers destroyed and replaced by fibrous or fatty tissues

108
Q

what are macromotor units

how do thye compare to original muscle

A

a. Neighboring motor units can sprout new branches to re-innervate muscle fibers resulting in “macromotor units.”
i. Macromotor units have less dexterity than the original muscle but they do preserve some fxn

109
Q

Duchenne MD

A

a. Heritable absence of dystrophin (protein required for muscle structure)
b. Males, females have 50% chance of carrying/passing mutation
c. Onset of progressive weakness leading to paralysis at 3-5 yr, most lose ability to walk by 12 yo
d. Becker MD similar but less severe disorder of dysfunctional dystrophin

110
Q

Adult MD

A

a. Fascioscapulohumeral MD - slowly progressive disorder of face, arms, shoulder beginning in teens
b. Myotonic - MC adult form characterized by cardiac abnormalities and cataracts, swan neck, drooping eyelids

111
Q

MD

A

a. Mostly affects boys (rarely girls).
b. Often brothers or male relatives have same problem.
c. First signs appear around ages 3 to 5: the child may seem awkward or clumsy, or he begins to walk ‘tiptoe’ because he cannot put his feet flat. Runs strangely. Falls often.
d. Problem gets steadily worse over the next several years.
e. Muscle weakness first affects feet, fronts of thighs, hips, belly, shoulders, and elbows. Later, it affects hands, face, and neck muscles. “Walk up” from seated/lying position.
f. Most children become unable to walk by age 10.
g. May develop a severe curve of the spine.
h. Heart and breathing muscles also get weak. Child usually dies before age 20 from heart failure or pneumonia.