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BRS Phys > Ch1 > Flashcards

Ch1 Flashcards

1
Q

Attachments between cells that permit intracellular communication

A

Gap Junctions

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2
Q

Channel proteins that permit communication in gap junctions

A

Connexins

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3
Q

Prevents paracellular movement of solutes between cells

A

Tight junctions (zonula occludens)

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4
Q

Factors (3) which increase permeability of a solute in a membrane

A

Increased oil/water coefficient of the solute (more lipophilic) Decreased size of the solute Decreased membrane thickness

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5
Q

Three types of carrier-mediated transport

A

Facilitated diffusion, primary active transport, and secondary active transport (antiport/symport)

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6
Q

Is facilitated diffusion active or passive?

A

Passive (down its concentration gradient with the help of a carrier protein)

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7
Q

Glucose transport into muscle and adipose is an example of which type of transport?

A

Facilitated diffusion (down concentration gradient with a carrier protein).

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8
Q

Na/K ATPase is an example of which type of transport?

A

Primary active transport (uses a carrier and ATP to move 2 solutes against their concentration gradients)

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9
Q

Stoichiometry of the Na/K ATPase

A

3 Na out, 2 K in

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10
Q

Sodium/glucose transport in the small intestine is an example of which type of transport?

A

Secondary active transport (symport) - moves sodium down its concentration gradient to provide the energy to move glucose against its concentration gradient. Both move in the same direction.

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11
Q

Moving one solute down its concentration gradient to generate the energy to move another solute against its concentration gradient is known as…

A

Secondary active transport (antiport/countertransport)

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12
Q

What does ion conductance refer to?

A

The probability that a specific ion channel is open (i.e. the permeability of a particular ion)

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13
Q

Approximate equilibrium potentials for Na, Ca, K, Cl

A

Na = +65 mV
Ca = +120 mV

K = -85 mV

Cl = -85 mV

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14
Q

What is the significance of the resting membrane potential with respect to individual ion permeability?

A

The ion with an equilibrium potential closest to a given RMP will be the most permeable to a membrane at the given RMP.

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15
Q

At RMP, which ion is the membrane most permeable to? Why?

A

Potassium
RMP = -70
K equilibrium potential = -85

K’s equilibrium potential is the closest to the RMP. Its high resting conductance sets the resting membrane potential.

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16
Q

What is responsible for the upstroke of an action potential?

A

Depolarization causing opening of activation gates (M gate) of sodium channels, with inward flow of sodium ions.

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17
Q

Tetrodotoxin and lidocaine block…

A

Voltage sensitive sodium channels

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18
Q

A time period at which no action potential can be fired, no matter how large the stimulus

A

Absolute refractory period

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19
Q

Time period at which an action potential can be fired, but only with a larger-than-normal stimulus

A

Relative refractory period

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20
Q

What is the neurotransmitter released by presynaptic neurons at the NMJ? What receptor does it bind to?

A

Ach, nicotinic receptor

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21
Q

Steps following action potential propagation at the NMJ.

A
  1. Action potential passes
  2. Calcium channels opened on presynaptic neuron, causing calcium influx
  3. Calcium uptake causes release of Ach into the synaptic cleft
  4. Ach binds postsynaptic nicotinic receptors (ligand gated ion channels)
  5. Ach binding causes influx of sodium and efflux of potassium on the postsynaptic membrane (generates a miniature end plate potential)
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22
Q

Acetylcholinesterase degrades Ach into what (2)?

A

Acetyl CoA and choline

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23
Q

MOA of hemicholinium

A

Blocks choline reuptake by the presynaptic neuron at the NMJ, depleting the presynaptic endings of Ach.

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24
Q

Inputs that depolarize a postsynaptic cell, bringing it closer to threshold and more likely to fire an action potential.

A

Excitatory postsynaptic potentials (EPSPs) - caused by opening of sodium and potassium channels.

25
Q

Inputs that hyperpolarize a postsynaptic cell, bringing it farther away from threshold and less likely to fire an action potential.

A

Inhibitory postsynaptic potentials (IPSPs) - caused by opening of chloride channels (inhibitory neurotransmitters GABA and glycine).

26
Q

What is the primary NT released from postganglionic sympathetic neurons?

A

Norepinephrine

27
Q

Serotonin is derived from which amino acid?

A

Tryptophan

28
Q

Histamine is derived from which amino acid?

A

Histidine

29
Q

GABA is derived from which amino acid?

A

Glutamate

30
Q

NE/epinephrine are derived from which amino acid?

A

Tyrosine

31
Q

A sarcomere runs from…

A

Z line to Z line

32
Q

What happens to its length during contraction?

A

Length of myosin (thick) filament Nothing

33
Q

What function does troponin T serve?

A

Attaches the troponin complex to tropomyosin

34
Q

What function does troponin I serve?

A

Inhibits interaction of actin and myosin (I for inhibition)

35
Q

What function does troponin C serve?

A

Binds calcium, causing a conformational change which moves troponin I, allowing interaction of actin and myosin.

36
Q

What function do T-tubules serve?

A

Carry the depolarization from the sarcolemma membrane to the cell interior.

37
Q

Where are T tubules located?

A

At the junction of A bands and I bands

38
Q

What is the function of the dihydropyridine receptor?

A

Sits in the T tubules, senses the passing action potential, opening the ryanodine receptor, which causes release of calcium from the SR.

39
Q

What causes reuptake of calcium into the SR following the passage of an action potential?

A

SERCA (antiport with sodium)

40
Q

What protein binds calcium in the SR?

A

Calsequestrin

41
Q

What are the 3 components of thin filaments?

A

Actin, troponin, tropomyosin

42
Q

Explain the 4 steps in cross-bridge cycling

A
  1. No ATP bound to myosin, myosin is tightly bound to actin. This is permanent with complete loss of ATP (rigor mortis). 2. ATP binds to myosin, causing myosin to be released from actin. 3. Hydrolysis of ATP moves the myosin head towards the + end of actin. 4. Myosin-ADP binds a new site on actin, “upstream”, and release of Pi causes the power stroke. ADP is then released, resulting in the rigor state (back to 1)
43
Q

Good video: https://www.youtube.com/watch?v=Ct8AbZn_A8A

A

KK

44
Q

What purpose does ATP serve in cross-bridge cycling with respect to the affinity of actin and myosin for each other?

A

Binds to myosin, causing it to be released from actin.

45
Q

What is the function of tropomyosin?

A

Blocks the myosin-binding site on actin, preventing contraction.

46
Q

How is relaxation achieved in skeletal muscle?

A

When calcium is taken up back into the SR by SERCA.

47
Q

What is an isometric contraction?

A

A contraction where the length of the muscle is held constant with no shortening (trying to push LECOM across Grandview boulevard).

48
Q

What is an isotonic contraction?

A

A contraction where the load on the muscle is held constant. Shortening is measured (lifting a 2 pound barbell)

49
Q

What contraction protein is present in skeletal muscle but not smooth muscle?

A

Troponin

50
Q

Explain the steps in excitation contraction coupling of smooth muscle.

A
  1. Depolarization of the membrane opens voltage gated calcium channels, increasing intracellular calcium 2. Calcium binds to calmodulin
  2. Calmodulin activates myosin light chain kinase
  3. Myosin light chain kinase phosphorylates myosin, allowing it to bind actin, initiating cross bridge cycling 5. Decreases in intracellular calcium produces relaxation
51
Q

What happens to the I band during contraction?

A

Shortens

52
Q

What is the H band?

A

Central area of myosin filaments that contains no crossbridges.

53
Q

What is the reflection coefficient?

A

A value representative of the solubility of a solute in a membrane. Reflection coefficient of 1 = impermeable. Coefficient of 0 = highly permeable.

54
Q

What is unique about carrier mediated-transport with respect to the rate at which it can do its job?

A

Carrier mediated transport is saturable. That is, transport rate increases as the concentration of the solute increases until the transporter reaches its transport maximum (Tm).

55
Q

Define transport maximum. With what type of transport is it seen?

A

Transport maximum - the rate at which carrier mediated transport proteins are saturated, and can’t work at a faster rate.

56
Q

In contracting smooth muscle, what binds calcium?

A

Calmodulin

57
Q

When calcium binds calmodulin, what does it activate?

A

Myosin light chain kinase.

58
Q

What activates myosin light chain kinase?

A

Calmodulin with calcium bound to it

BRS Phys (6 decks)

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