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Bio Module 5 > Neuronal communication 5.3 > Flashcards

Neuronal communication 5.3 Flashcards

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Biology 101 flashcards
1
Q

What is a Pacinian corpuscule?

A

A pressure sensor found in the skin that detects changes in pressure

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2
Q

What are sensory receptors?

A

Specialised cells that can detect changes in our surroundings

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3
Q

What is a transducer?

A

A cell that converts one form of energy into another

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4
Q

Where are Pacinian corpuscules found?

A

The skin

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5
Q

What kind of receptors are Pacinian corpuscules?

A

Mechanoreceptors

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6
Q

What is the structure of a pacinian corpuscule?

A

Oval shaped structure consisting of rings of connective tissue wrapped around the end of a nerve cell

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7
Q

What triggers an action potential in a pacinian corpuscule?

A

When pressure is applied which stretches the nerve cell membrane and causes a change in polarity

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8
Q

What energy transfer do photoreceptors do?

A

Light to electrical

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9
Q

What energy transfer do mechanoreceptors do?

A

Movement to electrical

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10
Q

What energy transfer do chemoreceptors do?

A

Chemical to electrical

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11
Q

What energy transfer do thermoreceptors do?

A

Heat to electrical

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12
Q

What is the resting potential?

A

When the charge is negative on the inside and positive on the outside

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13
Q

Is resting potential polarised or depolarised?

A

Polarised

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14
Q

What is the permeability of the membrane like?

A
  • more permeable to K ions so they leak out more
  • less permeable to Na ions so few leak out
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15
Q

Is an action potential polarised or depolarised?

A

Depolarised

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16
Q

What do neurons consist of?

A
  • myelin sheath
  • schwann cells
  • nodes of ranvier
  • nucleus
  • mitochondria
  • ribosomes
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17
Q

What does a dendron do?

A

Transmits electrical impulse towards the cell body

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18
Q

What does an axon do?

A

Transmits electrical impulse away from cell body

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19
Q

What is the myelin sheath made up from?

A

Schwan cells

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20
Q

What is saltatory conduction?

A

When the action potential jumps from node of ranvier to node of ranvier

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21
Q

Why is saltatory conduction quicker?

A
  • reduces energy expenditure
  • reduces degradation of impulse
    (can travel longer distances)
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22
Q

What causes quicker transmissions?

A
  • bigger axon (higher SA)
  • higher temp
  • nodes of ranvier
    (doesnt depolarise entire membrane)
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23
Q

What is depolarisation?

A

A change in polarity (Inside of cell becomes more positive)

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24
Q

What happens due to slow closing potassium channels?

A

Refractory period

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25
Q

What cannot occur during a refractory period?

A

An action potential

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26
Q

Why does the refractrory period happen?

A

Allows time for the cell to recover and ensures that action potentials only occur in one direction

27
Q

What is happening during the refractory period?

A

Hyperpolarisation

28
Q

What is the threshold potential?

A

The threshold needed to create an action potential (-50mV)

29
Q

What is the refractory period?

A

The period after an action potential when another action potential cannot be reached

30
Q

What causes the refractory period?

A

Hyperpolarisation of the membrane

31
Q

What is the difference between a small stimulus and a strong one?

A

A weak stimulus only triggeres 1 action potential whereas a strong one triggers multiple

32
Q

What is the voltage inside the cell at resting potential?

A

-60mV

33
Q

What do sodium potassium pumps do?

A

Actively transport 3 Na+ out of the neuron for every 2 K+ moved in

34
Q

What do non gated ion channels do?

A

Allow facilitated diffusion of K+ and Na+ down their diffusion gradients (more K+ channels than Na+)

35
Q

What causes an action potential?

A
  • Pressure is applied
  • Na gated channel open
  • Na ions diffuse into cells
  • causes small amount of depolarisation (generator potential)
  • If voltage change is higher than -50mV threshold value an action potential will occur
36
Q

What are the 6 stages of an action potential?

A
  • resting potential
  • stimulius
  • depolarisation
  • PD reaches +40mV
  • repolarisation
  • hyperpolarisation
37
Q

What happens at resting potential?

A
  • outside is positive and inside is negative
  • 70mV difference in charge
  • Na+ voltage gate ion channels are closed
  • K+ non voltage gated channels mostly closed
  • Na/K gated channel protein actively transport 3Na+ out for every 2K+ in
38
Q

What happens when a stimulus appears?

A
  • triggers some Na+ voltage gated channels to open
  • Na+ diffuses into the neuron
  • Inside of neuron becomes more positive
39
Q

What happens at depolarisation?

A
  • PD reaches threshold value of -50mV
  • causes all Na+ voltage gated channels to open
  • more Na+ diffuses into the neuron
  • positive feedback loop so this keeps happening to increase voltage inside
40
Q

What happens once PD reaches -40mV?

A
  • Na+ voltage gated channels close
  • K+ voltage gated channel proteins open
41
Q

What happens during repolarisation?

A
  • K+ diffuses out the neuron
  • reduces PD
  • inside is now more negative than the outside
42
Q

What happens during hyperpolarisation?

A
  • Lots of K+ diffuses out due to slow closing gates
  • inside is now more negative than resting potential
  • K+ voltage gated channels now fully close
  • Ma/K pump moves Na out the neuron
  • K+ diffuses back into neuron
  • resting potential is now achieved
43
Q

What is the all or nothing law?

A

The idea that once threshold value is reached an action potential will always fire with the same voltage no matter the size of the stimulus

44
Q

What is a synapse?

A

A junction between two or more neurones or a neurone and an effector?

45
Q

Why do synapses use chemical messages?

A

An action potential cannot bridge the gap so a neurotransmitter is used

46
Q

What are the components of a cholinergic synapse?

A

Axon terminal, presynaptic knob, synaptic cleft, post synaptic cell, dendrites

47
Q

How does a synapse pass on a message?

A
  • action potential arrives at axon terminal
  • depolarisation causes voltage gated Ca 2+ channels and Ca 2+ enters cell
  • Vesicles release ACh (acetylcholine) into synaptic cleft by exocytosis
  • ACh diffuses across synaptic cleft and binds to specific cholinergic receptors
  • Na+ channels open and it diffuses in
  • action potential continues
48
Q

What happens to ACh after it binds to the receptors?

A

Enzymes (acetylcholinesterase) digest neurotransmitter and products are transported back to presynaptic nob

49
Q

Why is the neurotransmitter digested?

A
  • to recycle the neurotransmitter
  • to prevent response from happening again
50
Q

How do cholinergic receptors work?

A

2 acetylcholine molecules fuse to receptor site and sodium ion channel opens

51
Q

What is an exitatory synapse?

A
  • have receptors that are Na+ channels
  • when open Na+ diffuses in
  • causes a local depolarisation and make an AP more likely
  • exitatory post synaptic cleft (EPSP)
52
Q

What is the neuro transmitter for an exitatory synapse?

A

acetylcholine

53
Q

What is an inhibitory synapse?

A
  • has receptors that let Cl- ions in sp make membrane potential more negative
  • hyperpolarises membrane sso inhibits an action potential
  • impulse in one neuron can inhibit the impulse in the next
  • inhibitory post synaptic potential (IPSP)
54
Q

What is the neuro transmitter for an inhibitory synapse?

A

GABA (gamma aminobutyric acid)

55
Q

What is the importance of synapses?

A
  • unidirectional transmission
  • convergence
  • divergence
  • spatial summation
  • temporal summation
  • Filtering out low level signals
  • habituation
  • memory
56
Q

Why is unidirectional transmission important?

A
  • ensures every impusle travels in one direction
  • vesicles of neurotransmitter are only found in the presynaptic buld
  • neurotransmitter receptors are only found in the post synaptic membrane
57
Q

Why is convergence important?

A

Allows impulses from several neurones to be passed to a single neurone

58
Q

Why is divergence important?

A

Allows impulses from a single neurone to be passed to multiple neurones

59
Q

What is spatial summation?

A
  • each stimulus causes the release of the same amount of neurotransmitter
  • sometimes this causes a small depolarisation in the post synaptic neurone but not enough to trigger an action potential
  • spatial summation is when when multiple neurones release neurotransmitters to combine to cause an action potential
  • volume
60
Q

What is temporal summation?

A
  • where two or more impulses arrive in quick succession from the presynaptic neurone
  • the quantity of neurotransmitter in a short period of time is enough to trigger an action potential
  • frequency
61
Q

Why is it important to filter out low level signals?

A
  • to not become overwhelmed by every stimulus
  • if a low level stimulus creates an AP in the presynaptic neurone, it is unlikely to pass across the synapse and will not cause another AP
62
Q

What is habituation?

A
  • after repeated stimulation a synapse might run out of vesicles of neurotransmitter
  • nervous system no longer responds to the stimuls as it has become habituated
  • prevents overstimulation and damage of effectors
63
Q

Why is memory important?

A
  • synaptic membranes are adaptable
  • post synaptic membranes an be made more sensitive by adding more receptors
  • and adapted post synaptic membrane is more likely tyo fire an action potential
  • creates a specific pathway in response to a stimulus

Bio Module 5 (3 decks)

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