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bisc 221 > Topic 8: Nervous System > Flashcards

Topic 8: Nervous System Flashcards

1
Q

What are neurons?

A

nerve cells that transfer information within the body

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2
Q

What are the two types of signals neurons use to communicate?

A

electrical signals (long-distance) and chemical signals (short-distance)

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3
Q

Where are most of a neuron’s organelles?

A

the cell body

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4
Q

What are dendrites?

A

highly branched extensions that receives signals from other neurons

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5
Q

What is an axon?

A

a much longer extension that transmits signals to other cells at synapses

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6
Q

What is the axon hillock?

A

the cone-shaped base of an axon

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7
Q

What are neurotransmitters?

A

chemical messengers that pass information from the synaptic terminal of one axon across the synapse

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8
Q

What is a synapse?

A

a junction between an axon and another cell

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9
Q

Where do information transmit from and to?

A

from a presynaptic cell (a neuron) to a postsynaptic cell (a neuron, muscle, or gland cell)

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10
Q

What cells are neuron cells supported by?

A

glia or glia cells

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11
Q

What are the three stages of the nervous system?

A
  1. sensory input
  2. integration
  3. motor output
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12
Q

What happens during sensory input?

A

sensors detect external stimuli and internal conditions and transmit information along sensory neurons

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13
Q

What happens during integration?

A

sensory information is sent to the brain or ganglia, where interneurons integrate the information

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14
Q

What happens during motor output?

A

motor output leaves the brain or ganglia via motor neurons, which trigger muscle or gland activity

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15
Q

What are three classes of neurons?

A
  1. sensory neuron
  2. interneuron
  3. motor neuron
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16
Q

What is the central nervous system?

A

(CNS) where integration takes place; this includes the brain and a nerve cord

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17
Q

What is the peripheral nervous system?

A

(PNS) which carries information into and out of the CNS

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18
Q

What forms nerves?

A

bundles of PNS neurons

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19
Q

What establishes the resting potential of a neuron?

A

ion pumps and ion channels

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20
Q

What is a membrane potential?

A

a voltage (difference in electrical charge) across its plasma membrane

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21
Q

What is the resting potential?

A

the membrane potential of a neuron not sending signals

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22
Q

What is the resting potential in mammalian neurons (concentrations)?

A

the concentration of K+ is the highest inside, while the concentration of Na+ is highest outside the cell

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23
Q

What are the sodium-potassium pumps?

A

use the energy of ATP to maintain these K+ and Na+ gradients across the plasma membrane

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24
Q

What is the function of the opening of ion channels?

A

converts the chemical potential to electrical potential

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25
Q

What is the resting potential in mammalian neurons (channels)?

A

many open K+ channels and fewer open Na+ channels

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26
Q

What is the major source of membrane potential?

A

the resulting buildup of negative charge within the neuron

27
Q

What are action potentials?

A

signals conducted by axons

28
Q

Why do changes in membrane potential occur?

A

neurons contain gated ion channels that open or close in response to stimuli

29
Q

What are graded potentials?

A

changes in polarization where the magnitude of the change varies with the strength of the stimulus

30
Q

What causes an action potential?

A

a sufficient depolarization results in a non-linear change in membrane voltage

31
Q

What are the characteristics of action potentials?

A

have a constant magnitude, are all-or-none, and transmit signals over long distances

32
Q

What happens during resting potential?

A

most voltage-gated sodium (Na+) and potassium (K+) channels are closed

33
Q

What happens during depolarization?

A

voltage-gated Na+ channels open first and Na+ flows into the cell

34
Q

What happens during the rising phase of the action potential?

A

the threshold is crossed, and the membrane potential become positive

35
Q

What happens during the falling phase of the action potential?

A

voltage-gated Na+ channels become inactivated; voltage gated K+ channels open, and K+ flows out of the cell

36
Q

What happens during undershoot?

A

membrane permeability to K+ is at first higher than at rest, then voltage-gated K+ channels close and resting potential is restored

37
Q

What is the refractory period?

A

after an action potential, a second action potential cannot be initiated

38
Q

How is the speed of action potential propagation limited in unmyelinated axons?

A

the time it takes to move along every section of the membrane

39
Q

What is the function of the refractory channels?

A
  1. prohibits the action potential from going backwards
  2. limit the frequency of firing a second one cannot follow two closely after
40
Q

What is the relationship between action potential and diameter?

A

the speed of an action potential increases with the axon’s diameter

41
Q

What is the speed difference between myelinated and non-myelinated axons?

A

the speed of action potential propagation is 15x faster (150 m/sec or 335 mph) than with non-myelinated axons (with no increase in axon diameter)

42
Q

What is saltatory conduction?

A

myelin sheath allows the action potential to jump from node to node; can only be generated at the nodes

43
Q

What is the function of refractory periods (2)?

A
  1. prevents backward propagation
  2. sets an upper limit on frequency of firing
44
Q

What are the mechanisms for electrical synapse (3)?

A
  1. coordinates adjacent cells
  2. rapid synaptic transmission
  3. bidirectional
45
Q

What are the mechanisms for chemical synapse (3)?

A
  1. amplifies signals
  2. diversity of postsynaptic responses
  3. plasticity allows for flexibility
46
Q

What does direct synaptic transmission involve?

A

binding of neurotransmitters to ligand-gated ion channels in postsynaptic cell causing ion channels to either open or close, generating a postsynaptic potential

47
Q

What is excitatory postsynaptic potentials (EPSPs)

A

depolarizations that bring the membrane potential toward threshold

48
Q

What is inhibitory postsynaptic potentials (IPSPs)

A

hyperpolarizations that move the membrane potential farther from threshold

49
Q

When do receptor activation and postsynaptic response cease?

A

when neurotransmitters are cleared from the synaptic cleft

50
Q

How are neurotransmitters removed?

A

by simple diffusion, inactivation by enzymes, or recapture into the presynaptic neuron

51
Q

What happens in neural plasticity?

A
  1. connections between neuron are strengthened or weakened in response to activity
  2. if two synapses are often active at the same time, the strength of the postsynaptic response may increase at both synapses
52
Q

What is long-term potentiation (LTP)?

A
  1. an increase in the strength of synaptic transmission
  2. involves glutamate receptors
53
Q

What happens when presynaptic and postsynaptic neurons are stimulated at the same time?

A

the set of receptors present on the postsynaptic membranes changes

54
Q

What is the gyrus?

A

a small protrusion or bump formed by the folding of the cerebral cortex

55
Q

What is the sulcus?

A

a groove in brain matter, often found in the neocortex or cerebellum

56
Q

What is the fissure?

A

a very deep sulcus

57
Q

What is the function of cerebrospinal fluid?

A

fills the central canal of the spinal cord and the ventricles of the brain, which supplies the CNS with nutrients and hormones and carries away wastes

58
Q

What is gray matter?

A

neuron cell bodies, dendrites, and unmyelinated axons

59
Q

What is white matter?

A

bundles of myelinated axons

60
Q

What is the function of the peripheral nervous system?

A

transmits information to and from the CNS and regulates movement and the internal environment

61
Q

What is the function of afferent neurons?

A

transmit information to the CNS

62
Q

What is the function of efferent neurons?

A

transmit information away from the CNS

63
Q

What is the sympathetic division?

A

regulates arousal and energy generation (“fight-or-flight” response)

64
Q

What is the parasympathetic division?

A

antagonistic effects on target organs and promotes calming and a return to “rest and digest” functions

bisc 221 (10 decks)

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