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BIO 212 Class > Unit 2 Study Guide > Flashcards

Unit 2 Study Guide Flashcards

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Biology 101 flashcards
1
Q

Two anatomic divisions of the nervous system

A
  • central nervous system

- peripheral nervous system

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2
Q

central nervous system

A
  • brain and spinal cord
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3
Q

peripheral nervous system

A
  • includes nerves and ganglia
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4
Q

functional divisions of the peripheral nervous system

A
  • sensory nervous system (afferent)
  • motor nervous system (efferent)
  • difficult because they sound the SAME
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5
Q

sensory nervous system

A
  • responsible for receiving sensory information from receptors that detect stimuli and transmitting this information to the CNS
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6
Q

divisions of the sensory nervous system

A
  • somatic sensory

- visceral sensory

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7
Q

somatic sensory

A
  • sensory input that is consciously received

- receptors of the five senses and proprioreceptors

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8
Q

visceral sensory

A
  • sensory input that is not consciously perceived

- structures within blood vessels and internal organs

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9
Q

motor nervous system

A
  • initiated and transmits motor input from the CNS to effectors
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10
Q

divisions of the motor nervous system

A
  • somatic motor

- autonomic motor

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11
Q

somatic motor

A
  • initiates and transmits motor output from the CNS to skeletal muscles
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12
Q

autonomic motor

A
  • innervates and regulates cardiac muscle, smooth muscle, and glands without our conscious control
  • further divided into sympathetic and parasympathetic
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13
Q

5 characteristics of a neuron

A
  • excitability - responsiveness to a stimulus
  • conductivity - ability to propagate an electrical signal. voltage gated channels along membrane open sequentially
  • secretion - release neurotransmitter in response to conductive activity. messenger is released from vesicle to influence target cell
  • extreme longevity - cell can live throughout person’s lifetime
  • amitotic - during fetal development of neurons, mitotic activity is lost in most neurons

SCALE

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14
Q

Cell body of the neuron

A
  • called the soma
  • enclosed by a plasma membrane and contains cytoplasm surrounding a nucleus
  • serve as neuron’s control center
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15
Q

dendrites

A
  • short, unmyelinated processes that branch off the cell body that receive input and transfer to cell body body for processing
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16
Q

axon

A
  • longer process emanating from the cell body to make contact with other neurons, muscle cells, or gland cells
  • attaches to the cell body at the axon hillock
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17
Q

axoplasm

A
  • cytoplasm within the axon
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18
Q

axolemma

A
  • membrane within axon
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19
Q

axon collaterals

A

side branches which lead to axon terminals with synaptic knobs

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20
Q

structure of a multipolar neuron

A
  • multiple processes extend directly from the cell body
  • typically many dendrites and one axon
  • most common type of neuron
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21
Q

anterograde transport

A
  • the movement of materials from the cell body to synaptic knobs
  • usually newly synthesized materials
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22
Q

retrograde transport

A
  • movement of materials from synaptic knobs to the cell body

- moves used material from axon for breakdown and recycling in soma

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23
Q

fast axonal transport

A
  • movement along microtubules
  • power for movement comes from specialized motor proteins that split ATP to supply energy needed
  • can be moved in either direction
  • anterograde transport of vesicles, organelles, and glycoproteins
  • retrograde transport of used vesicles to be broken down and recycled, and potentially harmful agents.
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24
Q

slow axonal transport

A
  • results from flow of axoplasm
  • substances only moved from the cell body toward the synaptic knob
  • includes enzymes, cytoskeletal components, and new axoplasm for regenerating axons
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25
Q

3 functional classification of neurons

A
  • sensory
  • motor
  • interneurons
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26
Q

sensory neurons

A

responsible for conducting sensory input from both somatic and visceral sensory receptors to the CNS

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27
Q

motor neurons

A

conduct motor output from the CNS to both somatic effectors and visceral effectors

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28
Q

interneurons

A
  • receive stimulation from many other neurons and receive, process, and store information, and “decide” how the body responds to stimuli.
  • facilitate communication between sensory and motor neurons
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29
Q

pumps on plasma membrane of neuron

A
  • maintain specific concentration gradients by moving substances against a concentration gradient, a process that requires energy
  • plasma membrane contains Na+/K+ pumps (entire neuron) and Ca2+ pumps (transmissive segment)
30
Q

leak channels on plasma membrane of neuron

A
  • leak channels - always open allowing Na+ to diffuse in and K+ to diffuse out. More K+ leak channels than Na+ leak channels
  • Na+ and K+ leak channels located throughout entire neuron plasma membrane.
  • important in establishing/maintaining RMP.
31
Q

chemically-gated channels on plasma membrane of neuron

A
  • normally closed but open in response to binding of neurotransmitter.
  • When they open, allow ions to diffuse across the plasma membrane.
32
Q

voltage-gated channels on plasma membrane of neuron

A
  • normally closed but open in response to changes in electric charge across the plasma membrane
  • when they open, allow a specific ion to diffuse across the membrane
  • voltage-gated Na+ channels are unique in that they have two gates (an activation gate and an inactivation gate)
33
Q

four functional segments of the neuron

A
  • receptive
  • initial
  • conductive
  • transmissive

TRIC

34
Q

receptive segment

A
  • includes both dendrites and the cell body

- chemically gated channels are located here

35
Q

initial segment

A
  • composed of axon hillock

- contains both voltage gated Na+ and K+ channels

36
Q

conductive segment

A
  • equivalent to the length of the axon

- contains both voltage gated Na+ and K+ channels

37
Q

transmissive segment

A
  • includes the synaptic knobs and contains voltage gated Ca2+ channels and Ca2+ pumps
38
Q

normal resting potential in a neuron

A
  • when neuron at rest, the membrane potential is referred to as RMP
  • typically -70 mV
39
Q

how RMP is maintained and established

A
  • consequence of movement of ions across the plasma membrane through leak channels
  • K+ exit the neuron into IF. Leaves inside more negative
  • Na+/K+ pumps move 3 Na+ out and 2 K+ into neuron
  • help maintain concentration gradient of both Na+ and K+
  • concentration gradient allows for diffusion of Na+/K+ as part of neuron’s generation of electrical current
40
Q

Graded potential

A
  • relatively small, short-lived changes in the RMP that are caused by the movement of small amounts of ion across the plasma membrane
  • established in the receptive segments by the opening of chemically gated channels: cation channels, K+ channels, and Cl- channels.
  • a graded potential lasts only as long as the channels are open and until the local current ceases.
41
Q

EPSPs

A

-postsynaptic potentials that result in the neuron becoming more positive

42
Q

how EPSPs are generated

A
  • NT crosses synaptic cleft and binds specifically to a receptor that is a chemically gated cation channel, causing it to open
  • Na+ and K+ move down concentration gradient, but more Na+ moves into the neuron than K+ moves out
  • inside of neuron becomes slightly more positive
  • local current of Na+ becomes weaker as it moves along neuron PM
  • DEPOLARIZATION
43
Q

IPSPs

A

postsynaptic potentials that result in the neuron becoming more negative

44
Q

how IPSPs are generated

A
  • NT crosses synaptic cleft and binds either to chemically gated K+ channel or Cl- channel
  • if binds to K+ channel, channel opens and K+ flows out. If binds to Cl- channel, Cl- flows into neuron
  • inside of neuron becomes slightly more negative
  • local current of ions becomes weaker as it moves along neuron PM
  • HYPERPOLARIZATION
45
Q

summation

A

the changes in the membrane potential associated with graded postsynaptic potentials are added in the initial segment

46
Q

temporal summation

A

occurs when a SINGLE presynaptic neuron repeatedly releases NT to produce multiple EPSPs in the postsynaptic neuron at the SAME location repeatedly within a very short time

47
Q

spatial summation

A

occurs when MULTIPLE presynaptic neurons release NT at VARIOUS locations onto the receptive segment, thus generating EPSPs, IPSPs, or both in the postsynaptic neuron

48
Q

significance of threshold membrane potential at the initial segment

A
  • the minimal voltage change in membrane potential is the determining factor if an action potential is initiated
  • on average, the value for the threshold membrane potential is about -55 mV. Change of +15 from RMP
  • When this threshold is reached, the voltage-gated channels are stimulated to open, which will initiate the generation of an action potential that will be propagated along the axon
49
Q

polarized phase of action potential

A
  • the resting membrane potential
50
Q

Depolarized phase of action potential

A
  • Na+ flows into region from adjacent areas. Membrane potential becomes more positive.
  • voltage-gated Na+ channels triggered to open when sufficient Na+ flows into region to change the membrane potential from -70 mV to -55 mV
  • voltage-gated Na+ channels remain open to allow Na+ entry to cause depolarization.
51
Q

Repolarized phase of action potential

A
  • reaching of threshold value triggers voltage-gated K+ channels to open.
  • slow to open and not completely open till about the point depolarization has ended
  • voltage-gated K+ channels remain open to allow rapid K+ exit from the axon
  • triggers the voltage-gated Na+ channels to change from the inactivation state to the resting state - now can be stimulated again
52
Q

Hyperpolarized phase of action potential

A
  • the voltage-gated K+ channels typically remain open longer than the time needed to reestablish the RMP.
  • the inside of the neuron during this brief time is more negative than the RMP
53
Q

refractory period

A
  • the brief time period after an action potential has been initiated during which an axon is either incapable of generating another potential or a greater than normal amount of simulation is required to generate another action potential.
54
Q

absolute refractory period

A
  • the time after an action potential onset when no amount of stimulus, no matter how strong, can initiate a second action potential
  • during this time, the voltage-gated Na+ channels are first opened, and then they are closed in the inactivation state (activation gate open, inactivation gate closed)
  • generally remain in inactivation state until membrane potential has almost retuned to the RMP through depolarization
  • ensures the action potential only moves in one direction
55
Q

relative refractory period

A
  • occurs immediately after the absolute refractory period
  • another AP may now be initiated in an axon only if the stimulation of the PM is greater than the stimulus normally needed to generate an AP.
  • at this time, voltage-gated Na+ channels have returned to their resting state, but the neuron is hyperpolarized
56
Q

continuous conduction

A
  • occurs in unmyelinated axons and involves sequential opening of voltage-gated Na+ channels and voltage-gated K+ channels located within the axon PM along entire length of axon
57
Q

saltatory conduction

A
  • occurs in myelinated axons
  • APs do not occur in regions of the axon that are myelinated
  • propagated only at neurofibril nodes which have a relatively large # of both voltage-gated Na+/K+ channels and lack myelin insulation
  • ions are relatively free to flow into an out of the axon in these regions when channels are open.
58
Q

neurofibral node

A
  • initiation of AP
  • Na+ into axon (conduction of AP)
  • followed by repolarization as voltage-gated K+ channels open, and K+ diffuses out
59
Q

myelinated regions

A
  • diffusion through axoplasm
  • relatively fast
  • becomes weaker with distance as experiences resistance
  • can’t go through myelin so flows in one direction
60
Q

next neurofibral node

A
  • arrival of weak Na+ current

- sufficient to cause opening of voltage-gated Na+ channels, new AP generated

61
Q

Events of the transmissive segment

A
  • release of NT from synaptic vesicles
  • before AP arrives, Ca2+ pumps embedded in PM establish Ca2+ gradient by pumping Ca2+ into IF
  • nerve signal reaches synaptic knob
  • Voltage-gated Ca2+ channels open and Ca2+ enters synaptic knob and binds with proteins associated with synaptic vesicle
  • synaptic vesicles fuse with synaptic knob PM and NT is exocytosed
  • NT diffuse across synaptic cleft and attaches to receptor on a muscle or to receptors of a neuron or gland
62
Q

graded potential

A
  • occurs in receptive segment of neuron and are due to opening of CHEMICALLY-GATED channels.
  • results in membrane potentials becoming depolarized or hyper polarized
  • loses its intensity as it moves along the plasma membrane;
  • short lived and travel short distances

THE CONNOR POTENTIAL

63
Q

action potential

A
  • generated within initial segment and propagated along conductive segment of neuron
  • initiated when VOLTAGE-GATED channels open in response to a minimum voltage change
  • AP is self-propagating and maintains intensity as it moves along axon to synaptic knob bc of successive opening of voltage-gated channels

THE JL POTENTIAL

64
Q

synthesis of acetylcholine

A
  • synthesized from acetate and choline and then stored within synaptic vesicles within synaptic knob of neuron.
  • released by exocytosis into synaptic cleft in response to arrival of AP in presynaptic neuron
65
Q

Acetylcholine effect on nicotinic receptor

A
  • directly causes EPSP
66
Q

acetylcholine effect on muscarinic receptor

A
  • indirectly leads to either EPSP or IPSP
67
Q

removal of acetylcholine

A
  • some ACh will be immediately digested by acetylcholinesterase, an enzyme that resides in synaptic cleft
  • digested into choline and acetate
  • choline taken up into the neuron.
68
Q

neuromodulation

A
  • the release of chemicals from cells that locally regulate or alter the response of neurons to neurotransmitters
69
Q

facilitation

A
  • occurs where there is a greater response from a postsynaptic neuron because of the release of neurotransmitter in the synaptic cleft
  • increase release from presynaptic or less reuptake/breakdown
  • or increased number of receptors on postsynaptic neurons
70
Q

inhibition

A
  • occurs when there is less response from a postsynaptic neuron because of the release of neuromodulators
  • results from either a decreased amount of NT in synaptic cleft
  • decreased release from presynaptic or greater reuptake/breakdown
  • or decreased number of receptors on postsynaptic neurons.

BIO 212 Class (12 decks)

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