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Biology > Neuronal Communication > Flashcards

Neuronal Communication Flashcards

1
Q

In a sensory neurone where is the cell body located?

A

in the middle of two extensions

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2
Q

Which extension in a sensory neurone carries impulses from the sensory receptors towards the cell body?

A

the dendron

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3
Q

Electrical impulses are carried away from the cell body in a sensory neurone by which extension?

A

the axon

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4
Q

What type of cells form the myelin sheath?

A

Schwann cells

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5
Q

What are the gaps in between the Schwann cells called?

A

the nodes of Ranvier

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6
Q

What does myelin sheath act as?

A

an electrical insulator

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7
Q

Where are dendrites located on a motor neurone?

A

around the cell body

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8
Q

Where is the cell body located on a motor neurone?

A

at one end

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9
Q

Does a motor neurone have a dendron?

A

No only an axon

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10
Q

What direction does an electrical impulse travel along an axon of a motor neurone?

A

from the cell body to the axon terminal

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11
Q

Do relay neurones have axons or dendrites?

A

relay neurones can have multiple short dendrons and short axons

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12
Q

What direction does an electrical impulse travel along a relay neurone?

A

from dendrites to axons

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13
Q

What is the state called when there is no electrical impulse travelling along a neurone?

A

resting state

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14
Q

In a resting neurone, what is the charge inside of the membrane compared to the outside? What do scientists call the membrane?

A

negative and they say that the membrane is polarised

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15
Q

What is the resting potential of a neurone?

A

-70 mV

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16
Q

In an axon membrane, the sodium-potassium pump does what?

A

actively transports sodium ions out of the axon and, at the same time, it actively transports potassium ions into the axon

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16
Q

In every pump of the sodium-potassium pump, how many sodium ions are pumped out of the axon?

A

3

16
Q

In every pump of the sodium-potassium pump, how many potassium ions are pumped into the axon?

A

2

16
Q

In a resting state, are the ion channels in the axon membrane mainly open or closed?

A
  • sodium ion channels are mainly closed so there is a low rate of diffusion of sodium ions into the axon
  • the potassium ion channels are mainly open so there is a high rate of diffusion of potassium ions out of the axon
17
Q

What are the two factors that contribute to the resting potential of an axon membrane?

A
  • the sodium-potassium pump transfers three sodium ions out of the axon for every two potassium ions transferred in
  • the outward movement of potassium ions via facilitated diffusion through ion channels
18
Q

What does the Pacinian corpuscle detect?

A

pressure

19
Q

Where are Pacinian corpuscles located?

A

in the deep layers of the skin

20
Q

Where on the body are high numbers of Pacinian corpuscles located and where else are Pacinian corpuscles located?

A

the fingertips and soles of the feet and they are also in joints

21
Q

Why are Pacinian corpuscles also found in joints?

A

they detect when the joints are changing direction

22
Q

What does a Pacinian corpuscle produce in response to pressure? And what do scientists call this?

A

a nervous impulse (a generator potential)

23
Q

Why do scientists say that the Pacinian corpuscle acts as a transducer?

A

the Pacinian corpuscle converts mechanical energy (pressure) into the energy of a nervous impulse

24
Q

What is located in the centre of a Pacinian corpuscle?

A

the end of the sensory neurone

25
Q

In a Pacinian corpuscle, what is the end of the sensory neurone surrounded by?

A

many layers of connective tissue

26
Q

In a Pacinian corpuscle, what is between each layer of connective tissue?

A

a layer of gel

27
Q

In the membrane of the end of the sensory neurone in a Pacinian corpuscle, what are the sodium ion channels called?

A

stretch-mediated sodium channels

28
Q

What happens when pressure is applied to a Pacinian corpuscle?

A

Pressure causes the shape of the Pacinian corpuscle to change. This shape change causes the membrane of the neurone to stretch which causes the stretch-mediated sodium channels to widen so now sodium ions diffuse through the channels into the neurone. This causes the interior of the neurone to become positively charged (the neurone has depolarised). A generator potential has been created.

29
Q

What does the generator potential (in a Pacinian corpuscle) cause? What do scientists call this?

A

a wave of depolarisation to pass down the sensory neurone to the CNS and scientists call this wave of depolarisation an action potential

30
Q

As well as ion channels and sodium-potassium pumps, what other protein structures are in an axon membrane?

A

voltage-gated ion channels

31
Q

When do voltage-gated ion channels open?

A

when the membrane potential reaches a certain value

32
Q

What does a stimulus trigger first on the axon membrane?

A

the energy of the stimulus triggers voltage-gated sodium ion channels to open and sodium ions now rapidly diffuse into the axon

33
Q

After a stimulus is detected, what does the initial rapid diffusion of sodium ions into the axon cause?

A

this causes the inside of the axon to become less negative and this now triggers more voltage-gated sodium ion channels to open, allowing more sodium ions to diffuse into the axon (scientists call this positive feedback)

34
Q

After a stimulus is detected, what is the influx of sodium ions into the axon called?

A

depolarisation

35
Q

After the depolarisation of the membrane, the inside of the membrane reaches a potential of what?

A

+40mV

36
Q

During an action potential, what happens when the membrane potential reaches around +40mV?

A

this triggers the voltage-gated sodium ion channels to close and the voltage-gated potassium ion channels to open - sodium ions stop diffusing into the axon and potassium ions now diffuse out of the axon down their electrochemical gradient

37
Q

Steps of sliding filament model

A

1, Tropomyosin (held in place by troponin) prevents myosin head from attaching to binding site on actin.
2, Calcium ions (from sarcoplasmic reticulum) bind to troponin which moves/pulls tropomyosin.
3, Myosin head (ADP attached) can now attach to binding site on actin.
4, Myosin head bends which moves actin filament. ADP released. (power stroke)
5, ATP attaches to the myosin head. Causes myosin head to detach from actin.
6, Hydrolysis of ATP to ADP - provides energy for myosin head to resume its normal position.
7, Myosin head attaches to another binding site + repeats.

38
Q

A muscle fibre only contains enough ATP to allow for how many seconds of contraction?

A

1 - 2 seconds

39
Q

Why is creatine phosphate important in a muscle cell?

A

creatine phosphate maintains a supply of ATP in a muscle cell by rapidly transferring an inorganic phosphate to ADP, reforming ATP

Biology (27 decks)

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