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A&P 1 FAU > Lecture 11.4 main points > Flashcards

Lecture 11.4 main points Flashcards

1
Q

define the absolute refractory period, why does this occur (what ion channels play the main role and how)?

A

after initiating an action potential, there is a period of time called the absolute refractory period during which a cell cannot generate another AP no matter how strong the stimulus
Na channels are activated and then inactivated
inactivated Na channels must first return to the resting state before they can be opened again
not enough deactivated voltage gated Na channels to allow for another AP

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2
Q

define the relative refractory period, what type of stimulus is necessary for AP during relative refractory period

A

period of time during which a second action potential can be initiated, but only by a large-than-normal (suprathreshold) stimulus
coincides with the period when the voltage gated K channels are still open after enough inactivated Na channels have returned to their deactivated resting state to allow for another AP

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3
Q

list the phases of AP where the absolute and relative refractory periods take place

A

absolute refractory period - during depolarization and repolarization
relative refractive period - after hyper-polarizing state

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4
Q

where does AP begin ?

A

at the trigger zone near the axon hillock

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5
Q

what are the two types of methods in what AP are conducted

A

continuous conduction
saltatory conduction

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6
Q

which type of AP conduction method is used by myelinated axon

A

saltatory conduction

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7
Q

which type of AP conduction method is used by un-myelinated axons

A

continuous conduction

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8
Q

list the three factors that affect speed of AP conduction

A

axon diameter- wider diamater = faster curren
degree of myelination - more myelination = faster
temperature - higher temp = faster (to a point) : too high or too low affects ion channels (bc they are proteins)

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9
Q

what is the role of frequency of AP and number of neurons signaling for a response at the same time in perception of a stimulus

A

The frequency of AP plays a crucial role in determining the perception of a stimulus, or the extent of our response.
-In addition to this “frequency code,” a second important factor is the number of neurons recruited (activated) to the cause

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10
Q

list the three types of axon fibers and their characteristics

A

A fibers - largest diameter and fast (up to 280mph), myelinated neurons that carry touch and pressure sensations; many motor neurons are also of this type

B fibers - medium size diameter and speed (up to 32mph) compromise myelinated visceral sensory and autonomic pre ganglion neurons

C fibers - smallest diameter and slowest (up to 4mph), comprise un-myelinated sensory and un-myelinated autonomic neurons

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11
Q

in what direction does communication occur at a chemical synapse ? is this one way or both ways?

A

a one way transfer from a pre synaptic neuron to postsynaptic neuron

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12
Q

list the events involved in the release of NT from the presynaptic cell

A

When an AP reaches the end bulb of axon terminals, voltage gated Ca channels open and Ca flows inward, triggering the release of the neurotransmitter

-in this way, the presynaptic neuron converts an electrical signal (nerve impulse) into a chemical signal (release neurotransmitter)

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13
Q

what effect does the release of the NT from the pre synatic cell have on the post synaptic cell

A

the neurotransmitter crosses the synaptic cleft and binds to ligand - gated receptors in the post synaptic membrane. The post synpatic neuron receives the chemical signal and in turn generates an electrical signal (post synaptic potential)

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14
Q

how does the affect of speed signaling information being relayed by the synapse

A

the time required for these processes at a chemical synapse produces a synaptic delay of 0.5 msec

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15
Q

are NT receptors specific or can any molecule bind and cause an effect?

A

each neurotransmitter receptor has one or more neurotransmitter binding sites where its specific NT binds

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16
Q

what are ionotropic receptors? give an example

A

receptor that has NT binding site and is an ion channel as well, when a NT binds to the receptor, it opens or closes the ion channel portion of the receptor
-nicotinic ACh receptor is an example

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17
Q

what are metabotropic receptors and give an example?

A

contains NT binding site but lacks an ion channel as part of its structure
-glutamate is an example

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18
Q

how do metabotropic receptors directly activate or deactivate ion channels

A

G-proteins can go on to activate/deactivate separate ion channels (direct)

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19
Q

how to metabotropic receptors indirectly activate or deactivate ion channels

A

G proteins can activate other proteins that go on to activate/ deactivate ion channels

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20
Q

what type of neurotransmitters are found in both the CNS and PNS

A

excitatory and inhibitory

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21
Q

is an excitatory NT always excitatory?

A

no, may be excitatory in some locations and inhibitory in others

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22
Q

list main chemical classifications of NTs

A

amino acids, biogenic amines, peptides (neuropeptides), purines, gases and lipids, endocannabinoids

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23
Q

main ways NT effects modified

A

synthesis can be stimulated or inhibited (pre synaptic)
release can be blocked or enhanced (pre synaptic)
removal from synaptic cleft can he stimulated or blocked
receptor site can be blocked or activated

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24
Q

what is a NT agonist ? example

A

any chemical that enhances or stimulates the effects of a molecule at a given receptor
-nAchrs are an example

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25
Q

what is a NT antagonist? example

A

chemical that blocks or diminishes the effects of a molecule at a given receptor
-atracurium besylate is a neuromuscular- blocking drug used as a paralytic agent for intubation, surgery, or ventilators

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26
Q

what is the effect of a NT on the electrical state of the post synaptic cell via its receptor?

A

can cause excitatory or inhibitory graded potential

27
Q

what is an EPSP and why is it called so?

A

causes depolarization of the postsynaptic cell
brings Vm closer to threshold

28
Q

is a single EPSP usually enough to reach threshold

A

no, but does make the post synaptic cell does become more excitable

29
Q

what is an IPSP and why is it called so?

A

hyperpolarizes the post synaptic cell - makes it more negative, moves Vm away from threshold

30
Q

how does spatial summation work?

A

occurs when postsynaptic potentials arrive near the same location at the same time

31
Q

how does temporal summation work

A

occurs when post synaptic potentials arrive near the same location close to the same time

32
Q

NOTE for summation

A

whether or not the post synaptic cell reaches threshold depends on the net effect after summation of all the post synaptic potentials (excitatory and inhibitory)

33
Q

what would be the effect on the post synaptic cell if the NT stayed in the synapse?

A

if stayed in the synapse, would influence postsynaptic neuron, muscle fiber, or gland cell indefinitely

34
Q

how are NT removed from the synapse

A

re-uptake
degradation
diffusion

35
Q

reuptake of NT from the synapse

A

removal of NT via astrocytes (in CNS) or axon terminal of release neuron

36
Q

degradation of NT in synapse

A

removal of NT by enzymes

37
Q

diffusion of NT in synapse

A

removal of NT that removes NT away from the cleft

38
Q

what is integration in reference to neuronal signaling

A

the process accomplished by the post synaptic neuron when it combines all excitatory and inhibitory inputs and responds accordingly
this process occurs over and over as interneurons are activated in higher parts of the brain

39
Q

what is a neuronal network

A

may contain thousands or even millions of neurons

40
Q

what are diverging circuits in a neuronal network, provide an example

A

one input, many outputs
an amplifying circuit
example- a single neuron int he brain can activate 100 or more motor neurons in the spinal cord and thousands of skeletal muscle fibers

41
Q

what are converging circuits, what are they used for, provide an example

A

many inputs, one output
a concentrating circuit
example- different sensory stimuli can all elicit the same memory

42
Q

what are reverberating circuits, what are they used for, provide an example

A

signals travel through a chain of neurons, each feeding back to previous neurons
an oscillating circuit
involved in breathing, sleep wake cycle, and repetitive motor activities such as walking

43
Q

discuss parallel after-discharging circuits, what are they used for, provide an example

A

signal stimulates neurons arranged in parallel arrays that eventually converge on a single output cell
impulses reach output cell at different times, causing a burst of impulses, called an after-discharge
example- may be involved in exacting mental processes such as mathematical calculations

44
Q

what are neurotoxins and how do they affect neurons?

A

an extensive class of exogenous chemicals which adversely affect function in both developing and mature nervous tissue

45
Q

are neurotoxins always exogenous

A

no, some overproduction or release of endogenous NT can be neurologically toxic

46
Q

list an example and know the terminology for an endogenous neurotoxic event

A

over release of glutamate in the CNS from ischemia (low oxygen) can cause neuronal over-excitation leading to the death of the neuron (excito-neurotoxicity)
this is what happens in a stroke

47
Q

what is botulinum toxin?

A

most acutely lethal toxin known. average lethal dose is 1.3-2.3ng/kg

48
Q

how does botulinum toxin work

A

it blocks the release by cutting snare proteins and blocking the release of Ach from motor neuron terminal means no stimulation of skeletal muscle fiber contraction - paralysis of skeletal muscle innervated by the neuron

49
Q

what is TTX?

A

tetrodotoxin

50
Q

list an example of where TTX can be found

A

in the viscera of a type of japanese puffer fish and many other animals

51
Q

how does TTX work

A

it is a fast voltage gated Na channel inhibitor, it binds and inhibits the opening of voltage gated Na channels in the PNS
can cause paralysis in muscle and loss of sensation

52
Q

how can TTX kill you

A

can lead to paralysis in the diaphragm

53
Q

what are local anesthetics

A

drugs that block pain or other somatic sensations around the site of injection

54
Q

why are they called local

A

because they only block pain or sensation at the site of the injection

55
Q

how do most local anesthetics work

A

blocking neuronal voltage gated Na channels therefore AP are blocked

56
Q

what are examples of local anesthetics

A

lidocaine and procaine (novocaine)

57
Q

how can cooling in a neuron affect signaling

A

can slow or partially block AP conductions as well

application of ice to an injury not only reduces swelling from inflammation but also decreases pain by affecting ion channel kinetics

58
Q

what are general anesthetics

A

drugs that can cause a reversible loss of consciousness

59
Q

how are general anesthetics different from that of local

A

they do not dull pain, just cause unconsciousness

60
Q

what is depression

A

a disorder in which people may feel sad and helpless, have lack of interest, and may experience suicidal thoughts

61
Q

list examples of depression

A

major depression, dysthymia, bipolar disorder, manic depressive illness, seasonal affective disorder (SAD)

62
Q

is depression caused by just one thing

A

no

63
Q

what NT may play a role in depression

A

serotonin, norepinephrine, and dopamine

64
Q

what are SSRIs and how do they work

A

inhibit the re uptake of serotonin in the synapse by the presynaptic cell therefore prolonging its duration and effects

A&P 1 FAU (15 decks)

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