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BIOL 2005 > (Lectures 4-6, Chapters 7 & 10) Nervous System, Neuron, CNS, ANS > Flashcards

(Lectures 4-6, Chapters 7 & 10) Nervous System, Neuron, CNS, ANS Flashcards

1
Q

Synapse

A

Site of communication between a neuron and another part of the body (neuron, muscle, gland, etc.)

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2
Q

Leak channels

A

Allow Na+ and K+ to flow into/out of (respectively) the neuron

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3
Q

Dendrites

A

Extensions from cell body that receive info from other neurons

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4
Q

Axon hillock

A

Area where action potentials are initiated, right below the cell body

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5
Q

Axon

A

Transmits action potentials

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6
Q

Cell body

A

Contains nucleus and most organelles

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7
Q

Anterograde vs retrograde transport

A

Anterograde = movement away from cell body (e.g. mitochondria, enzymes)

Retrograde = towards cell body (e.g. degrading organelles, viruses, bacterial toxins)

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8
Q

Central nervous system

A

Brain + spinal cord

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9
Q

Peripheral nervous system

A

Cranial/spinal nerves & sensory receptors in the skin

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10
Q

3 functions of the nervous system

A
  • Sensory (sensing stimuli)
  • Integrative (CNS decides on response based on sensory info)
  • Motor (movement is conveyed from CNS to effectors via PNS)
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11
Q

2 types of cells in the nervous system

A
  • Neurons (specialized, excitable)

- Neuroglia (support neurons)

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12
Q

Types of neuroglia in the CNS

A
  • Ependymal cells (barrier between central spinal fluid and tissue fluid w/CNS cells)
  • Oligodendrocytes (form/maintain CNS myelin)
  • Astrocytes (support, control surrounding chemical environment)
  • Microglia (protect neurons from pathogens/debris, stabilize injured neurons)
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13
Q

Types of neuroglia in the PNS

A
  • Satellite cells (support neurons)

- Schwann cells (generate myelin)

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14
Q

Synaptic end bulb

A

Contains synaptic vesicles that release neurotransmitters

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15
Q

Presynaptic vs postsynaptic neuron

A
  • Presynaptic neuron fires synapses, releases neurotransmitters
  • Postsynaptic neuron receives signal (i.e. neurotransmitters)
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16
Q

How are synapses named? + examples

A

Named by the cells/tissues that they connect (e.g. neuronal = neuron-neuron, neuromuscular = neuron-muscle)

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17
Q

Function of myelin

A

Protect/insulate axon

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18
Q

What cells produce myelin?

A

Schwann cells (PNS), oligodendrocytes (CNS)

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19
Q

Is myelination continuous along an axon?

A

No; gaps are nodes of Ranvier

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20
Q

T/F: all neurons have myelinated axons

A

False

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21
Q

Plasticity vs repair

A 
Plasticity = ability to adapt/repair over a lifetime
Repair = regeneration after being damaged
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22
Q

Regeneration in the PNS

A
  • Occurs if cell body is intact & Schwann cell is active
  • Damaged myelin is removed
  • Schwann cells use substances from the cell body to repair the axon
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23
Q

T/F: damage to the CNS is permanent

A

True

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24
Q

T/F: neuron repair takes a long time to finish

A

True - starts quickly, but takes weeks/months for the neuron to function again

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25
Q

How do neurons communicate?

A

Changes in membrane potential

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26
Q

Concentrations of ions (neurons)

A
  • High [Na+] and [Cl-] in the ECF

- High [K+] and [Pr-] in the cytosol

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27
Q

What is the resting membrane potential of a neuron?

A

-70mV

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28
Q

What would happen if Na+ and K+ only moved into/out of the neuron via leak channels (at rest)? Why?

A

Resting membrane potential would increase because there are more leak channels for K+ in the membrane

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29
Q

How is the resting membrane potential maintained?

A

Sodium-potassium pump; ejects 3 Na+, intakes 2 K+

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30
Q

T/F: no ions move across a neuron’s membrane at rest

A

False

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31
Q

Membrane potentials of Na+ and K+

A

Na+: 60mV

K+: -90mV

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32
Q

Why is the electrochemical force for Na+ greater than that of K+?

A

Membrane potential of Na+ is farther from resting membrane potential than that of K+

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33
Q

Factors in determining resting membrane potential (3):

A
  • Unequal ion distribution in ECF + cytosol
  • Differences in permeability of membrane for different ions
  • Action of Na+/K+ ATPase
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34
Q

All but two ions have non-negligible effects on the membrane potential of neurons:

A

Na+, K+

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35
Q

What are gated channels?

A

Channels that open/close in response to stimuli, changing the rate of ion movement across the membrane by changing the membrane’s permeability

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36
Q

3 types of gated channels

A
  • Voltage-gated (respond to voltage)
  • Chemically-gated (respond to chemicals/ligands)
  • Mechanically-gated (respond to mechanical forces)
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37
Q

How do voltage-gated potassium channels work?

A
  • Channel closes = increase in membrane potential (from -70 to +30), K+ can’t leave
  • Channel opens = decrease in membrane potential (from +30 to -90), K+ leaves cell
38
Q

How do voltage-gated sodium channels work?

A
  • At rest, the activation gate is closed and the inactivation gate is open
  • At depolarization, both gates are open, so Na+ can enter the cell
  • Right after depolarization, the inactivation gate closes
39
Q

Where are chemically-gated channels found?

A

Dendrites, cell body

40
Q

Where are mechanically-gated channels found?

A

Sensory receptors

41
Q

Signals are either _____or ______.

A

Excitatory, inhibitory

42
Q

Graded potential vs action potential

A
  • GP: small, used to communicate over short distances (in the cell body)
  • AP: large, used to communicate over long distances (between neurons)
  • A significant enough change in the membrane potential will initiate an action potential at the axon hillock
43
Q

Temporal summation + spatial summation

A

Graded potentials can sum together over time (same stimulus repeated over small time intervals) and area (different stimuli at the same time)

44
Q

What is the threshold membrane potential (i.e. required to start an action potential)

A

-55mV

45
Q

Is an action potential triggered for every stimulus we receive?

A

No

46
Q

All-or-None Principle

A

Once a graded potential reaches threshold, an action potential occurs. The size of the stimulus doesn’t have an impact beyond what’s needed for an action potential (i.e. a threshold stimulus and a superthreshold stimulus result in the same change in membrane potential)

47
Q

3 steps in generation of action potential

A

1) Depolarization (occurs from rest until +30mV)
2) Repolarization (membrane potential drops after action potential, towards K+ membrane potential)
3) After Hyperpolarization (membrane potential returns to -70mV)

48
Q

Ion flow in action potentials

A

1) Rest: Na+ and K+ move across the membrane via leak channels, Na+/K+ ATPase pump
2) Depolarization: Na+ flows in
3) Repolarization: K+ flows out
4) After Hyperpolarization: resting membrane potential is restored by K+ outflow

49
Q

Absolute Refractory Period

A

Membrane can’t respond to any stimulus, regardless of strength

50
Q

Relative Refractory Period

A

Membrane can only respond to (and initiate an action potential due to) a stronger-than-normal stimulus

51
Q

Continuous Conduction

A

Action potential propagates along the entire length of an unmyelinated axon

52
Q

Saltatory Conduction

A

Action potential travels along a myelinated axon by “jumping” between nodes of Ranvier

53
Q

Between continuous and saltatory conduction, which is faster?

A

Saltatory (by a lot; 0.5-10m/s vs 150m/s)

54
Q

Electrical Synapses

A
  • Action potentials are conducted between adjacent cells via gap junctions
  • Connexons in gap junctions function as tunnels connecting the cells’ cytosol
  • Allow for fast communication and synchronization of a group of neurons or muscle fibers
55
Q

On a myelinated axon, where do ions interact with open channels?

A

Nodes of Ranvier

56
Q

Chemical Synapses

A
  • Involve release of a neurotransmitter into the synaptic cleft, which separates two neurons
  • Postsynaptic potential occurs in response to the chemical signal - action potentials can’t actually cross a synaptic cleft
57
Q

Where are synaptic vesicles located before releasing neurotransmitters?

A

In the cellular matrix; cytoskeleton of synaptic bulb

58
Q

How is the release of neurotransmitters triggered?

A
  • Voltage-gated Ca2+ channels open when the action potential reaches the synaptic bulb
  • Flow of Ca2+ into the bulb triggers exocytosis of synaptic vesicles
  • ## Neurotransmitters are released into the synaptic cleft + bind to receptors on the postsynaptic neuron (e.g. chemically-gated channels)
59
Q

Synaptic cleft

A

Space between neurons

60
Q

Inhibitory Post-Synaptic Potential (IPSP)

A

Neurotransmitter release causes a hyperpolarization of the post-synaptic membrane

61
Q

Excitatory Post-Synaptic Potential (EPSP)

A

Neurotransmitter release causes a depolarization of the post-synaptic membrane

62
Q

How does an action potential occur at the trigger zone of a postsynaptic neuron? (hint: IPSP and EPSP)

A

The net summation of IPSPs + EPSPs is a depolarization that reaches threshold

63
Q

Characteristics of neurotransmitters (4)

A
  • Synthesized in neurons
  • Released following depolarization
  • Bind to postsynaptic receptor
  • Inactivated after binding
64
Q

3 ways in which a signal is terminated, by removing the neurotransmitter

A
  • Diffusion away from the synaptic cleft
  • Enzymatic degradation
  • Uptake by other cells (either neuron that released them, or adjacent neuroglia)
65
Q

Autonomic Nervous System

A

Regulates the activity of visceral effectors (smooth/ cardiac muscle, glands)

66
Q

3 branches of the ANS

A
  • Sympathetic (fight/flight)
  • Parasympathetic (rest/digest)
  • Enteric (tissue in GI tract)
67
Q

Characteristics of autonomic motor pathway

A
  • Preganglionic neuron emerging from spinal cord
  • Postganglionic neuron emerging towards tissues
  • Ganglia (cell bodies around synapse)
  • ACh as the primary neurotransmitter
68
Q

T/F: In the sympathetic nervous system, the preganglionic neurons are longer than the postganglionic neurons

A

False

69
Q

Innervation of organs (by nerves of ANS)

A
  • Multiple sympathetic postganglionic nerves innervate one organ
  • One parasympathetic postganglionic neuron innervates one organ
70
Q

Adrenal medulla

A
  • Sympathetic pre-neurons extend to chromaffin cells in the adrenal medulla, which release NE and epinepherine into the bloodstream
71
Q

Where does an autonomic postganglionic neuron communicate with visceral effectors? Where are the neurotransmitters released?

A

Neuroeffector Junction; varicosities

72
Q

Cholinergic neurotransmitters/receptors

A
  • Receptors bind ACh
  • Neurotransmitters are first released from pre-neuron in both the sympathetic + parasympathetic nervous systems
  • Neurotransmitters are then released by post-neurons in the parasympathetic nervous system
73
Q

Adrenergic neurotransmitters/receptors

A
  • Norepinepherine/epinepherine

- First released by post-neurons in the sympathetic nervous system, then by chromaffin cells in the adrenal medulla

74
Q

Autonomic tone

A

Balance between sympathetic and parasympathetic activity

75
Q

What part of the brain regulates autonomic tone?

A

Hypothalamus

76
Q

Why is autonomic tone important?

Do visceral tissues always receive signals from both branches?

A
  • Ensures that visceral tissue function is stable at rest
  • Allows for quick responses from visceral tissue when needed
  • Visceral tissues always receive signals from both branches; one intensifies signals, the other attenuates them
77
Q

Functions of the parasympathetic branch

A
  • Salivation
  • Lacrimation (tearing up)
  • Urination
  • Digestion
  • Defecation
78
Q

Functions of the sympathetic branch

A
  • Support vigorous physical activity + rapid ATP production
  • Diffuse effects (spread out over several organs)
  • Excitement, emergency, exercise, embarrassment
79
Q

Which branch of the ANS has longer-lasting effects?

A

Sympathetic

80
Q

Somatic nervous system

A

Regulates activity of skeletal muscle - allows for voluntary contractions

81
Q

Neuromuscular junction

A

Site where a somatic nerve interacts with a skeletal muscle fiber

82
Q

How does signal transmission differ at the neuromuscular junction (compared to a neuronal synapse)?

A
  • Depolarization of motor end plate causes an end plate potential, which is larger in amplitude than an EPSP (so it can depolarize a muscle fiber to threshold)
  • Muscle action potential initiated by Na+ inflow via voltage-gated channels
  • Muscle action potential propagates in 2 directions away from the NMJ, triggering events to cause muscle contraction
  • Breakdown of ACh into acetyl and choline by AChE; neither can activate the ACh receptor
83
Q

Motor end plate

A
  • Region of muscle fiber opposite to the synaptic end bulb

- Contains 30-40M ACh receptors

84
Q

T/F: tissues innervated by the ANS will no longer function if their nerve supply is cut

A

False

85
Q

For the sympathetic and parasympathetic nervous systems, where are the cell bodies of their preganglionic neurons found?

A

Sympathetic: thoracic/upper lumbar regions of the spinal cord

Parasympathetic: brain stem/sacral region of the spinal cord

86
Q

Ionotropic receptors

A

Postsynaptic receptor that allows ion flux to change cell voltage; type of ligand-gated channel. Response is rapid + short-lasting

87
Q

Metabotropic receptors

A

Postsynaptic receptor that acts as a secondary messenger to produce effects in the cell; coupled to a G protein that causes the opening/closing of ion channels. Response is slow and long-lasting

88
Q

Cholinergic neurons in the ANS

A
  • Release ACh
  • All preganglionic neurons
  • Most parasympathetic postganglionic neurons
  • Sympathetic postganglionic neurons that innervate sweat glands
89
Q

Adrenergic neurons in the ANS

A
  • Release NE, epinepherine

- Sympathetic postganglionic neurons (except those that innervate sweat glands)

90
Q

T/F: there are no nodes of Ranvier in the CNS

A

False

BIOL 2005 (8 decks)

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