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Alevel Biology OCR > 5.1.3 Neuronal Communication > Flashcards

5.1.3 Neuronal Communication Flashcards

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1
Q

What is a neurone?

A

a specialised nerve cell that transmits electrical impulses rapidly around the body

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2
Q

What is the function of a sensory neurone?

A

to transmit electrical impulses from a sensory receptor cell to a relay neurone, motor neurone or the brain

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3
Q

What is the structure of a sensory neurone?

A
  • one dendron (transmits impulse to cell body)
  • cell body
  • one axon (transmits impulse from cell body)
  • dendron and axon have a myelin sheath
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4
Q

What is the function of a relay neurone?

A

to transmit electrical impulses between neurones

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5
Q

What is the structure of a relay neurone?

A
  • cell body
  • have many short dendrons and axons
  • non-myelinated
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6
Q

What is the function of a motor neurone?

A

to transmit electrical impulses from a sensory or relay neurone to an effector (aka muscle or gland)

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7
Q

What is the structure of a motor neurone?

A
  • cell body
  • lots of short dendrons (transmit impulses to cell body)
  • one long myelinated axon (transmits impulses from cell body)
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8
Q

What is a cell body of a neurone?

A
  • made up of nucleus, endoplasmic reticulum and mitochondria in cytoplasm
  • produces neurotransmitters
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9
Q

What is an axon?

A
  • a singular, elongated nerve fibre

- transmits impulse away from cell body

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10
Q

What are dendrons?

A
  • short extensions that come out of the cell body
  • split into smaller dendrites
  • transmit impulses towards cell body
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11
Q

What is a myelin sheath?

A

layers of plasma membrane around the axon

  • produced by Schwann cells growing around the axon
  • act as an insulating layer so that impulse can be transmitted quicker
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12
Q

What are nodes of Ranvier?

A

small gaps between each Schwann cell where the impulse jumps from one node to the next

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13
Q

What cells produce the myelin sheath?

A

Schwann cells

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14
Q

Why are impulses transmitted quicker in myelinated neurones?

A

at every node of Ranvier, the impulse jumps from one node to the next, which means it is transmitted quicker

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15
Q

What are sensory receptors?

A

groups of specialised cells which detect a change and convert this detected stimulus into a nerve impulse
-are usually located in sense organs

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16
Q

What are the main types of sensory receptors?

A
  • photoreceptor
  • thermoreceptor
  • chemoreceptor
  • mechanoreceptor
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17
Q

What is the stimulus of a thermoreceptor?

A

heat

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18
Q

What is the stimulus of a photoreceptor?

A

light

19
Q

What is the stimulus of a chemoreceptor?

A

chemicals

20
Q

What is the stimulus of a mechanoreceptor?

A

pressure and movement

21
Q

Name an example of a thermoreceptor

A

end-bulbs of Krause

-located in the tongue

22
Q

Name an example of a photoreceptor

A

cone cell

-located in eye

23
Q

Name an example of a chemoreceptor

A

olfactory receptor

-located in nose

24
Q

Name an example of a mechanoreceptor

A

Pacinian corpuscle
-located in skin

Baroreceptor
-located in blood vessels near heart

25
Q

How does the Pacinian corpuscle convert its stimulus into an impulse?

A
  • in resting state, stretch-mediated Na+ channels are too narrow for Na+ to pass through (resting potential)
  • when pressure is applied, the corpuscle changes shape so the axon stretches so its membrane is deformed, causing the Na+ channels to widen
  • Na+ diffuse in
  • this makes the membrane potential becomes +ve (is depolarised) which is known as a generator potential
  • this generator potential creates an action potential so the impulse passes along the neurone
26
Q

What is resting potential?

A

potential difference across membrane when it’s not transmitting an impulse (aka it is at rest)

  • membrane is polarised
  • potential difference is about -70mV
27
Q

How is resting potential established?

A
  • sodium/potassium pump actively transports 3Na+ out for every 2K+ it transports in
  • Na+ channels are closed so Na+ can’t move back into the axon but K+ channels are open so K+ can diffuse out of the axon
  • this means there are more +ve ions outside the axon so the axon is more -ve so reaches a resting potential of -70mV
28
Q

What is the potential difference at resting potential?

A

-70mV

29
Q

What is an action potential?

A

when an electrical impulse is created by the depolarisation in the membrane of a neurone

30
Q

How is an action potential generated?

A
  • neurone is at resting potential (-70mV) where some K+ channels are open and Na+ channels are closed
  • energy of the stimulus causes voltage-gated Na+ channels to open so Na+ diffuse out of the axon, making it less -ve
  • by positive feedback, more voltage-gated Na+ channels open so more Na+ leave and the inside of the axon becomes more +ve (it is depolarised)
  • when pd reaches +40mV, voltage-gated Na+ channels close and voltage-gated K+ channels open
  • K+ diffuse out of axon, making the inside of the axon more -ve (it is repolarised)
  • as lots of K+ diffuse out, axon becomes more -ve than at normal rest (it is hyperpolarised)
  • voltage-gated K+ channels close and sodium/potassium pump actively transports Na+ in and K+ out, bringing the axon back to resting potential (-70mV)
31
Q

What is the potential difference of the axon once it is depolarised?

A

+40mV

32
Q

What is a synapse?

A

the gap between two neurones or a neurone and an effector

33
Q

How is an impulse transmitted across a synapse?

A
  • action potential (Na+) reaches the end of the pre-synaptic neurone
  • the depolarisation of the pre-synaptic neurone causes Ca2+ channels to open
  • Ca2+ diffuse in
  • this causes vesicles containing neurotransmitters t move across the pre-synaptic knob and to fuse with the pre-synaptic membrane so that the neurotransmitters are released into the synapse by exocytosis
  • the neurotransmitters diffuse across the synapse and bind to receptors on Na+ channels on the post-synaptic membrane, causing these channels to open
  • Na+ diffuses into post-synaptic knob and along the neurone, causing an action potential (aka impulse) to be generated
34
Q

What neurotransmitter do cholinergic synapses use?

A

acetylcholine

35
Q

What is acetylcholine broken down into after an impulse is transmitted across a cholinergic synapse?

A

acetyl and choline

-by acetylcholinesterase

36
Q

How do synapses ensure impulses are only transmitted in one direction?

A

receptors for neurotransmitters are only on the post-synaptic membranes

37
Q

What is an inhibitory synapse?

A

a synapse where when neurotransmitters bind to receptors on the post-synaptic membrane, the membrane is hyperpolarised (pd becomes more -ve) which prevents an action potential from being fired

38
Q

What is an excitatory synapse?

A

a synapse where when neurotransmitters bind to receptors on the post-synaptic membrane, the membrane is depolarised (pd becomes less -ve) which causes an action potential to be fired if the threshold is reached

39
Q

What is synaptic divergence?

A

when one neurone connects to several neurones so the information can be dispersed to different parts of the body

40
Q

What is synaptic convergence?

A

when multiple neurones connect to one neurone so information can be amplified

41
Q

What is summation?

A

the process where whether a new action potential is generated after the synapse is controlled based on the conc of neurotransmitter released by the pre-synaptic neurone
-an action potential is only generated when the neurotransmitters reach a threshold

42
Q

What is spatial summation?

A

when neurones converge and multiple pre-synaptic neurones release neurotransmitters which diffuse across the synapse to the post-synaptic neurone
-if only one of the pre-synaptic neurones receives the signal (and releases neurotransmitters) no action potential would be generated on the post-synaptic knob

43
Q

What is temporal summation?

A

occurs when there is only one pre and post-synaptic neurone and higher frequencies of action potentials in the pre-synaptic neurone cause higher concs of neurotransmitters to be released so lots bind to the receptors on the post-synaptic neurone and cause an action potential/impulse to be triggered
-if there is only one action potential/impulse received, only low concs of neurotransmitters could be released so not enough bind to the post-synaptic neurone to trigger an action potential

44
Q

What is the threshold when an action potential is being created?

A

-50mV

Alevel Biology OCR (26 decks)

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