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Ion channels and Ion Transport > Ion channels and Ion Transport (2) > Flashcards

Ion channels and Ion Transport (2) Flashcards

1
Q

What are the 3 major groups of ion channels?

A

Mechanosensitive, voltage-gated, and chemosensitive (ligand-gated)

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2
Q

What kind of conformational change do carrier proteins go through?

A

Substrate induced because they have a binding site for the transported molecule

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3
Q

What kind of transport can carrier proteins mediate?

A

Both active and passive transport

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4
Q

What kind of transport can channel proteins mediate?

A

Only passive transport

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5
Q

What are ion channels?

A

Transmembrane proteins that connect the intracellular and extracellular environments

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6
Q

What is the distinction between different ion channels?

A

They are distinguished by the ion that passes through them and the mechanisms which cause them to open

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7
Q

When do mechanosensitive channels open?

A

When sensory endings are stretched

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8
Q

When do voltage-sensitive channels open?

A

In response to a change in the membrane (electrical) potential

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9
Q

When do chemosensitive (ligand-gated channels) open?

A

When they bind neurotransmitters, hormones or intracellular chemicals to the extracellular surface of the channel

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10
Q

What is mechanosensation important for?

A

Sensory perception, proprioception, and sensing changes in blood pressure

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11
Q

What are some characteristics of mechanosensitive channels?

A

Nonselective cation channels, impermeable to proteins, and the influx of ions when open cause changes in membrane potential

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12
Q

What are the types of voltage-sensitive ion channels?

A

Voltage-gated K+ channels, Voltage-gated Na+ channels, Voltage-gated Cl- channels, and voltage-gated Ca2+ channels

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13
Q

What do voltage gated K+ channels do?

A

They are responsible for bringing the cell to its resting membrane potential and the maintainance of that resting value

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14
Q

What do voltage gated Na+ channels do?

A

They are responsible for the depolarization of the action potential

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15
Q

What do voltage gated Cl- channels do?

A

They are poorly understood but are known to have a role in kidney regulation

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16
Q

What do voltage gated Ca2+ channels do?

A

They increase the intracellular calcium levels necessary for muscle contraction and calcium signaling

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17
Q

Name some examples of ligand-gated channels

A

Acetylcholine receptor channels: nicotinic receptor channels, CNS postsynaptic channels: glycine, GABA and serotonin channels, ATP-sensitive (purinergic) of P2X receptors, and Inositol triphosphate (IP3) and ryanodine receptors

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18
Q

What do agonists do?

A

Activate the channel to produce an electrical signal

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19
Q

What do antagonists do?

A

Bind to the channel and prevent channel opening

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20
Q

What does the cell membrane serve as?

A

An insulator to prevent movement of electrical charges to prevent ions from moving back and forth between intracellular and extracellular compartments

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21
Q

What does the membrane potential difference reflect?

A

The separation of charge across the membrane

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22
Q

In regards to the membrane how are the charges allocated?

A

The inner surface of the membrane has a net negative charge and the extracellular side has a net positive charge

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23
Q

What is membrane potential?

A

The voltage difference that exists between the inside and outside of the cell. Vm=Vo-Vi

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24
Q

What causes K+, Na+, Ca+, and Cl- to move across the cell membrane?

A

The concentration gradient for each ion and the electrical (gradient) difference. The sum of these 2 factors is the electrochemical gradient or the electrochemical potential

25
Q

What generates an ionic current?

A

The net movement of an ion across the membrane

26
Q

What is the net flux of an ion through the membrane?

A

The electrical current Ix. Ix=gx(V-Ex)
V-Ex is the driving force of the magnitude for ion movement for ion x
gx is ion conductance

27
Q

When does an inward current result?

A

When there is an influx of positive charges or an efflux of negative charges

28
Q

When does an outward current result?

A

When there is an efflux of positive charges or an influx of negative charges

29
Q

When does an equilibrium (reversal) potential occur?

A

When the net current is zero (no net movement of that ion because it reached equilibrium). Each ion has its own equilibrium potential

30
Q

When is the Nerst equation used?

A 
To determine equilibrium potential for a given ion. Eion(in mV)=61/z*log[ion]out/[ion]in
Eion=equilibrium potential of the ion
z=charge of the ion
[ion]out=extracellular concentration
[ion]in=intracellular concentration
31
Q

What is the resting membrane potential (RMP)?

A

The membrane potential difference for a cell at rest. It is established by charge and concentration for ions that can move across the membrane

32
Q

What are some different cell types and their membrane potentials?

A

Skeletal and cardiac muscle= -90 mV
Sensory/motor neurons= -70 mV
Smooth muscle= -60 mV
Red blood cells= -10 mV

33
Q

What ion is the resting membrane potential mainly permeable to?

A

K+ because the RMP is close to the equilibrium potentials for K+ when the cell is at rest

34
Q

What contributes to the resting membrane potential?

A

Potassium leak channels allow the efflux of potassium at rest and they continue to flow until the cell reaches the potassium equilibrium potential. Sodium leak channels allow a small influx of sodium ions so the cell never reaches the potassium equilibrium potential

35
Q

Does calcium play a major role in the resting membrane potential of most excitable cells?

A

No

36
Q

What is the basic mechanism for transmission of information in the excitable cells (nerve and muscle cells)?

A

Action potentials. Most are the result of changes in sodium and potassium ion movement in these cells. In cardiac cell action potentials also involve Ca2+

37
Q

How fast do action potentials occur in nerve and muscle cells compared to cardiac cells?

A

Nerve and muscle: ~1 millisecond

Cardiac: hundreds of milliseconds

38
Q

What is depolarization?

A

The process of making the membrane potential less negative

39
Q

What is repolarization?

A

The process of making the membrane potential more negative (brings the membrane potential back to the resting value)

40
Q

What is hyperpolarization?

A

The process of making the membrane potential more negative (usually more negative than the resting membrane potential)

41
Q

What is threshold potential?

A

The membrane potential at which the action potential will fire

42
Q

What is overshoot?

A

The portion of the action potential where the membrane potential is positive

43
Q

What is hyperpolarizing afterpotential (undershoot)?

A

The portion of the action potential where the membrane potential is more negative to the cell at rest

44
Q

What is the refractory period?

A

The period during which another normal action potential cannot be elicited

45
Q

Can graded potentials become action potentials?

A

Yes potentially

46
Q

What are the subdivisions of the refractory period?

A

Absolute refractory period: the time during which no stimulus regardless of its size, can stimulate an action potential
Relative refractory period: when a larger than normal stimulus can develop an action potential (usually abnormal in shape)

47
Q

What are the 4 methods of local communication between cells?

A

Gap junctions, contact dependent signals, autocrine signaling, and paracrine signaling

48
Q

What are gap junctions?

A

Junctions formed from the union of connexins that serve as a cytoplasmic bridge between neighboring cells. They allow the transfer of chemical and electrical signals from cell to cell and play an important role in the conduction of action potentials of cardiac muscle

49
Q

What are contact-dependent signals?

A

They occur by the direct interaction between 2 cells. A surface molecule on one cell binds to the receptor of another cell and they are important in the immune system and play a role in cell-adhesion processes

50
Q

What is autocrine signaling?

A

Occurs when a chemical signal that is released acts on the same cell that initiated the signal. The cell acts on itself

51
Q

What is paracrine signaling?

A

Occurs when a chemical signal is released and it acts on neighboring cells (near the site of release)

52
Q

How does the endocrine system work?

A

It uses hormones (chemical signals) that are released into the blood to act on specific cell receptors that are located in many places in the body

53
Q

How does the nervous system work?

A

It uses both chemical and electrical signals to communicate with cells and specific cell receptors in the body

54
Q

How do lipophilic molecules work?

A

They diffuse across the plasma membrane and bind to intracellular receptors to alter gene transcription and protein synthesis

55
Q

How do hydrophilic molecules work?

A

They can’t cross the plasma membrane so they bind to receptors located in the cell membrane to elicit an intracellular response

56
Q

What are the 4 categories of membrane receptors?

A

Receptor channel-ligand binding opens or closes the channel
Receptor enzyme-ligand binding to a receptor-enzyme activates an intracellular enzyme
G protein-coupled receptor-ligand binding to a G protein-coupled receptor opens an ion channel or alters enzyme activity
Integrin receptor- Ligand binding to integrin receptors alters the cytoskeleton

57
Q

What kind of signaling is an example of a receptor-enzyme linked signaling pathway?

A

Tyrosine kinase signaling

58
Q

Tyrosine kinase signaling is an important component of what actions on the body?

A

Insulin, growth hormone, and insulin-like growth factor-1

Ion channels and Ion Transport (1 decks)

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