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Intro Bio II Exam 1 > The Neuron > Flashcards

The Neuron Flashcards

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1
Q

What does the neuron talk to?

A

Other neurons, muscle, glands

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2
Q

Leak channel

A

Unregulated channel that is usually open that allows ions, mostly K+, to leak out of the cell

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3
Q

Membrane potential

A

Because the inside of the cell is negative relative to the outside, a charge difference across the membrane exists creating a membrane potential

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4
Q

Water with dissolved ions is a good _____.

A

Conductor

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5
Q

The lipid bilayer is an area of high electrical ______.

A

Resistance

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6
Q

Source of cell resting potential

A

Unequal charges that result from the Na+/K+ pump removing 3 Na+ from the cell and bringing 2 K+ into the cell + fixed anion

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7
Q

Electrogenic

A

Something that creates an electrical imbalance such as the sodium potassium pump

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8
Q

Fixed anion

A

A fixed/not moving/changing source of negative charge - sometimes thought of as proteins but is more likely nucleic acid such as RNA/DNA

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9
Q

What is the resting/membrane potential (in mV) of the cell?

A

-70 mV

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10
Q

In which direction does the electrical gradient move sodium? In which direction does the chemical gradient move sodium?

A

Both move sodium into the cell

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11
Q

In which direction does the electrical gradient move potassium? In which direction does the chemical gradient move potassium?

A

Electrical —> into the cell

Chemical —> out of the cell (this is why we have pumps)

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12
Q

Why are sodium and potassium leak channels necessary for a resting potential of -70 mV?

A

Potassium leak channels allow it to find its electrochemical equilibrium. When positively charged potassium ions leave the cell, the fixed anion inside the cell remains making the cell more negative. The sodium leak channel allows more sodium into the cell to keep the cell potential at -70 mV.

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13
Q

Depolarization

A

Cell membrane potential becomes less negative (moves toward zero mV)

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14
Q

Repolarization

A

Cell membrane potential returns to resting potential

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15
Q

Hyperpolarization

A

Cell membrane potential becomes more polarized

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16
Q

Which equation describes the equilibrium potential for any one ion species?

A

Nernst equation

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17
Q

Which equation describes the membrane potential (accounts for multiple ion species)?

A

Goldman-Hodgkin-Katz equation

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18
Q

Why is a cell polarized?

A

The interior of the cell is negatively charged with respect to the exterior of the cell.

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19
Q

Overshoot

A

When membrane potential becomes more positive (greater than zero and rising).

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20
Q

Basic parts of the nervous system

A

Central Nervous System = brain + spinal cord (surrounding by cerebral spinal fluid)

Peripheral Nervous System = somatic (control of skeletal muscles) + autonomic (sympathetic and parasympathetic)

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21
Q

Sympathetic

A

Fight or flight

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22
Q

Parasympathetic

A

Rest and digest

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23
Q

Dendrites

A

Projections off the neuron cell body that receive an input signal from another neuron, the environment via sensations, or sensory cells such as those in the eyes

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24
Q

What is the “integration center” of the neuron?

A

Axon hillock

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25
Q

Axon hillock

A

Region connecting the cell body to the axon

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26
Q

Axon

A

Single, long projection that is variable in length; where the electrical signal travels; ends in the presynaptic axon terminal

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27
Q

Axon terminal

A

End of the axon where the electrical signal becomes either a chemical signal to travel to the postsynaptic neuron dendrite

28
Q

Synapse

A

Region where the axon terminal communicates with its postsynaptic target cell

29
Q

What types of cells can neurons signal to?

A

Other neurons, muscle cells, gland cells

30
Q

Which cells are the most prominent in the brain?

A

Glial cells

31
Q

Types of glial cells

A

CNS - ependymal, astrocytes, microglia, oligodendrocytes

PNS - Schwann cells, satellite cells

32
Q

Which glial cells produce myelin?

A

Oligodendrocytes (CNS) and Schwann cells (PNS)

33
Q

Myelin sheath

A

Layers of membrane wrapped around the axon

34
Q

Purpose of myelin

A

Speed transmission of electrical signals and protects electrical signals - acts as an insulator

35
Q

Gated ion channels + descriptions

A

Ligand/chemical - A ligand binds to the channel causing a conformational change which opens the channel. When the ligand detaches, a conformational change closes the channel.

Voltage change - Closed at -70 mV. When the membrane potential changes, the channel senses depolarization and undergoes a conformational change to open. Upon repolarizaiton, the channel undergoes a conformational change and closes.

Mechanical - In select locations, a force (ex: fluid) pushes on a channel to force it open or closed.

36
Q

Overview of how neurons signal

A
  1. The neuron receives a signal
  2. Neuron undergoes an electrical change due to the movement of ions across the membrane via channels (membrane potential change)
  3. Neuron sends the generated electrical signal
37
Q

Excitable cells

A

Cells that generate an action potential (neurons and muscle)

38
Q

Directionality of an action potential in a neuron

A

Dendrites —> axon terminal

39
Q

Which cells have a resting potential?

A

All cells!

40
Q

Steps in the firing of an action potential

A
  1. Cell is at resting potential
  2. Stimulus depolarizes cell to threshold (~-55mV)
  3. Voltage-gated Na+ and K+ channels begin to open; Na+ open faster
  4. Rapid sodium entry depolarizes the cell
  5. Na+ channels begin to close while K+ channels are still opening
  6. K+ leaves cell and moves into ECF causing cell to repolarize
  7. K+ channels remain open allowing even more K+ to leave cell causing hyperpolarization
  8. K+ channels close and cell returns to resting potential
41
Q

What factors contribute to the amount of depolarization in an action potential?

A

Strength of a signal will impact how many sodium voltage-gated channels open

42
Q

What is the action potential threshold?

A

~ - 55 mV; the point along depolarization at which the voltage-gated ion channels all open (?)

A necessary membrane potential level achieved by a graded potential for an action potential to form.

43
Q

What is an action potential and where is it generated?

A

A signal propagated by changes in the membrane potential. Generated at the axon hillock. Multiple AP are fired for one signal to avoid losing signal strength. The AP always has the same magnitude.

44
Q

Process of opening, closing, and re-opening of a voltage-gated Na+ channel

A
  1. At resting potential, the voltage-sensitive activation gate keeps the channel closed.
  2. Depolarization causes the activation gate to open allowing Na+ ions into the cell.
  3. After a short period of time, the inactivation gate closes and Na+ entry stops.
  4. Repolarization allows both gates to reset to their original positions.
45
Q

Two types of gates in voltage-gated Na+ channel

A

Activation - voltage dependent gate

Inactivation - voltage independent gate

46
Q

Refractory period

A

When the Na+ channels are closed so a new AP cannot be fired (easily or at all)

47
Q

Absolute vs relative refractory period

A

Absolute - no AP can fire bc Na+ Channel Inactivation gates are closed

Relative - some open/closed inactivation gates allows a large enough stimulus to fire an AP

48
Q

Why does an AP only travel down the axon towards the axon terminal?

A

Refractory period prevents a signal from traveling backwards

The absolute refractory period follows along in the wake of the moving AP

49
Q

Describe the propagation of an AP down the axon

A

Each section of the axon is experiencing a different phase of the action potential. All AP have the same amplitude.

50
Q

Which neurons conduct AP most rapidly and why?

A

Myelinated neurons

  • insulation
  • current “jumps” down the axon due to Nodes of Ranvier
51
Q

Which glial cells myelinate peripheral neuronal axons?

A

Schwann cells

52
Q

Which glial cells myelinate central neuronal axons?

A

Oligodendrocytes

53
Q

Salutatorian Conduction

A

AP jump from one node of Ranvier to the next as they propagate along a myelinated axon. Only at the nodes do ion channels exist allowing for a new potential to be generated at each node. Only the current moves down the axon, not the ions. No ions cross the membrane where there is myelin.

54
Q

Effect of hyperkalemia

A

Increased [K+] brings membrane closer to threshold. Normally subthreshold graded potentials will trigger an AP.

55
Q

Effect of hypokalemia

A

Decreased [K+] brings membrane further from threshold. Normally suprathreshold graded potentials will no longer trigger an AP.

56
Q

Graded potentials

A
  • Input stimulus that fires an AP when suprathreshold
  • Amplitude varies with size of the initiating event
  • multiple GP can be summed
  • GP have no threshold
  • GP have no refractory period
  • Amplitude decreases with distance
  • can be depolarization or hyperpolarization
  • initiated by a stimulus, synapse, or spontaneously
  • mechanism depends on ligand-gated channels or other chemical or physical changes
57
Q

Steps to release a neurotransmitter when AP has reached the axon terminal

A
  1. AP depolarizes terminal
  2. Depolarization causes voltage-gated Ca2+ channels to open and for Ca2+ ions to enter the cell
  3. Ca2+ binds to protein called SNAREs in the membrane of synaptic vesicles which triggers exocytosis by pulling the synaptic vesicle against the cell membrane so that they fuse and release the neurotransmitter
  4. Neurotransmitter diffuses across the synaptic cleft and binds to receptors on the postsynaptic cell which initiates a response in that cell
58
Q

Recycling of acetylcholine

A
  1. In the cell, acetylcholine (ACh) is made from choline and acetyl CoA
  2. It is releases as a neurotransmitter and binds to the alpha-helical, non-ion specific cholinergic ligand receptor on the postsynaptic cell
  3. Acetylcholinesterase (AChE) degrades ACh
  4. choline is transported back int o the cell via secondary active transport with Na+ to make more ACh
59
Q

Types of axonal transport

A

Fast axonal - walks vesicles and mitochondria using motor proteins along microtubule network (reverse is retrograde)

Purpose is to avoid build up of materials at the axon terminal

60
Q

How does a neuron fire signals of differing strengths?

A

Fire more AP at hire frequency.

More, frequent AP —> more neurotransmitter released

61
Q

Graded potential summation

A

Spatial - signals from multiple presynaptic cells can fire at the same time at different dendrites and be summed. Some signals are excitatory (depolarizing, AKA EPSP) and some are inhibitory (hyperpolarizing, AKA IPSP). Either way, they sum to create a graded potential that may or may not be above threshold for an AP.

Temporal - multiple signals that are very close together in time can also sum

62
Q

EPSP, IPSP

A

Excitatory/inhibitory post synaptic potential
Excitatory - depolarization
Inhibitory - hyperpolarization

63
Q

Which ion often enters the postsynaptic cell at an inhibitory synapse?

A

Cl-

64
Q

Druggable targets in synaptic signaling

A
  • release and degradation of the neurotransmitter inside the axon terminal
  • increased neurotransmitter release into the synapse
  • prevention of neurotransmitter release into the synapse
  • inhibition of neurotransmitter synthesis
  • reduced reuptake of the neurotransmitter from the synapse (ex: choline)
  • agonists, antagonists can occupy receptors
  • reduced biochemical response inside the dendrites
65
Q

Agonists vs antagonists

A

Specific terms for neurotransmitters
Agonists evoke the same response as a neurotransmitter and antagonists block the response of a neurotransmitter

(Lack of signal does not always equal a reverse response)

Intro Bio II Exam 1 (5 decks)

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