Unit 5 - Neuronal Communication Flashcards Preview

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Flashcards in Unit 5 - Neuronal Communication Deck (62)
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1
Q

Main functions of nervous system

A

Send, recieve and interpret info

2
Q

Two parts of the nervous system

A

CNS

PNS

3
Q

What is a neuron

A

Conductive, excitable cells of the nervous system that are specialized to transmit electrical nerve impulses

4
Q

Nerves vs neurons

A

Neurons are the cells and nerves are the elongated congregation of tissues

5
Q

Rods and cones

A

Receptors in eyes

Detect changes in light

6
Q

Taste buds

A

Receptors on tongue

Detect change in chemical potential

7
Q

Pacinian corpuscles

A

Receptors on skin
Detect changes in movement and pressure
Meissners corpuscles do the same

8
Q

Ruffinis endings

A

Receptors on skin

Detect changes in heat

9
Q

Proprioreceptors

A

Receptors on muscles
Detect mechanical displacement
Involved in placement of limbs/ body awareness

10
Q

What do the hair cells in semi-circular canals do

A

Detect movement

Involved in balance

11
Q

What do the hair cells in the cochlea do

A

Detect sound

12
Q

Transducers

A

Detect a spp type of energy and convert it into another e.g electrical energy

13
Q

Where is action potential summed

A

At axon hillock which is then propagated down the axon

14
Q

Resting membrane potential

A

Potential diff across the membrane of a neuron

15
Q

Na^+/K^+ pump

A

Pump binds 3 Na^+ and 1 ATP
Hydrolysis of ATP provides energy to undergo a conformational change
Na is released to outside of the membrane and the shape changes to allow 2 K^+ to bind
Release of the phosphate allows the channel to revert to its original form, releasing the K^+ on the inside of the membrane

16
Q

How do sensory receptors change the resting potential of the axon membrane

A

By taking the energy its detecting and using it to change the membrane permeability to Na^+ ions to start an action potential

17
Q

Need for refractory period

A

Prevents overlap of action potential

Prevents action potential from moving backward (unidirectional)

18
Q

Receptor potentials

A

Localised changes in membrane potential

Graded and arent self-propagated

19
Q

Mechanoreceptor

A

Pressure/ stretch opens a VG ion channel

20
Q

Thermoreceptors

A

Temp affects enzymes controlling an ion channel

21
Q

Chemoreceptors

A

Chemical binds to a receptor, initiating a signal cascade to control an ion channel

22
Q

Photoreceptors

A

Light alters a membrane protein initiating a signal that controls an ion channel

23
Q

Motor neurons

A

Transmit impulses from a sensory/relay neuron to an effector. Have a long axon and short dendrites
Found in CNS

24
Q

Myelin sheaths

A

Made of many layers of a plasma membrane produced by Schwann cells. Acts as insulating layer and allows impulses to be conducted much faster

25
Q

Nodes of Ranvier

A

Impulses ‘jump’ from one node to another as it travels along the neuron which speeds up the transmission

26
Q

Axon

A

Singular elongated nerve fibres that transmit impulses away from the cell body. Cytoplasm surrounded by plasma membrane

27
Q

Relay neurons

A

Transmit impulses between sensory and motor neurones

Many short axons and dendrons

28
Q

Cell body

A

Contains nucleus surrounded by cytoplasm. Contains ER and mitochondria (involved in making neurotransmitters)

29
Q

Dendrons

A

Short extensions that come from the cell body, divide into smaller branches (dendrites). Responsible for transmitting electrical impulses towards the cell body

30
Q

Sensory neuron

A

Transmit impulses from a sensory receptor cell to a relay/ motor neurone or the brain
Dendron carries the impulse to the cell body and the axon carries impulse away from the cell body
Found in PNS

31
Q

Why do motor neurons have long axons

A

In order to transmit the action potential to the effectors all over the body

32
Q

Myelination

A

Prevents ion movement and forces the current to ‘jump’ along the axon
Reduces energy expenditure
Stops leakage of charge across mebrane and local current is attenuated and insufficient to polarise next node

33
Q

Why are myelinated neurons found in the PNS

A

Neurons in the PNS frequently have to transmit over long distances so speed of impulse is crticital to efficient function

34
Q

Action potential

A

Self regenerating depolarisation that allows excitable cells to carry a signal over a distance -60 to +40

35
Q

Why does the pre-synaptic knob end in a bulb

A

To increase SA for release for acetylcholine by exocytosis

36
Q

Why are Ca^+ channels on the pre-synaptic neuron VG

A

To prevent acetylcholine being released if theres no action potential

37
Q

Touch stimulus

A

Distortion of Pacinian Corpuscles
Causes stretch-mediated Na^+ channels to open
Causes Na^+ to move in and depolarises

38
Q

Depolarisation

A

The condition of the membrane that is less highly polarized than the usual resting state so the inside of the cell becomes less -ve with respect to the outside
VG Na - open
VG K - closed

39
Q

Repolarisation

A

The condition of the membrane when mechanisms are trying to bring the potental diff. across the cell back being to more - ve on the inside of the cell w/ respect to the outside
VG Na - closed
VG K - open

40
Q

Hyperpolarisation

A

The condition of the membrane that is more highly polarized than the usual resting state so the inside of the cell becomes more - ve than usual w/ respect to the outside

41
Q

Threshold potential

A

The critical level to which a membrane potential must be depolarised to initiate an action potential
-50 mV

42
Q

Describe and explain how a resting potential is maintained

A

Na/K ion pump - 3 Na ions out and 2 K into axon
VG Na+ channels are closed to stop Na diffusing in
Some K ion channels are leaky. Effect of conc. gradient is greater than the electrochemical gradient so diffuse out into extracellular fluid
Cell cytoplasm contain large organic anions (proteins)
Results in polarised cell membrane (+ve out/ -ve in)

43
Q

Describe what is happening at the cell membrane during an action potential

A

Resting membrane potential
Detection of stimuli - causes VG Na^+ to open. Begins to get depolarised
+ve feedback - More VG Na^+ channels open and moves in
When potential reaches +40mV VG Na^+ close and VG K^+ open - eflux of K+ causes repolarisation
K+ diffuse back out of the cell
Too -ve, hyperpolarisation
Resting membrane restored by Na/K pump

44
Q

Saltory conduction

A

Propagation of action potential along myelinated axons from one node to another
Done by creating longer local currents
Uninsulated nodes are the only place ions are exchanged across axon membrane

45
Q

More intense the stimulus …

A

The more frequently the neurons fire

46
Q

Synaptic cleft

A

Gap between pre-synaptic and post-synaptic Neuron

47
Q

Adaptations of post synaptic neuron

A

Contains specialised proteins in its membrane that act as acetylcholine receptor sites
They form Na^+ channels, which open in response to acetylcholine (generates action potential)

48
Q

Transmission across the synapse

A

Action potential arrives at presynaptic neuron and calcium ions open, so Ca^+ diffuse into knob
Vesicles move towards membrane and fuse to release acetylcholine into the cleft (exocytosis)
Diffuse across cleft and bind to receptors
Na^+ channels on post open and diffuses into post neurone
Membrane is depolarised
Acetylcholinesterase breaks down acetylcholine
Na^+ channels close and the choline is recycled back into the presynaptic knob

49
Q

Role of synapses in the nervous system

A

Ensures that action potentials travel in one direction; only receptor on post
Filters out low intensity stimulus; many vesicles must be released to cause a post synaptic action potential
Continuous, unimportant stimulus can be ignored; vesicles run out (fatigue) —> acclimatisation
Summation - amplify many low level stimulus

50
Q

Are relay neurons myelinated

A

No

51
Q

Which neuron has dendrons

A

Sensory - one long one

52
Q

Do motor neurons end at synaptic knobs as well

A

No, motor end plate

53
Q

Why are mitochondria needed for transmission of impulses across the cleft

A

Mitochondria in the pre-synaptic bulb is needed for:
Energy to move vesicles
Exocytosis
Na+/K+ pump to maintain resting potential
Vesicle formation
Active transport of Ca2+

54
Q

Propagation of action potentials

A

Once membrane is depolarised Na+ inside membrane attracted to -ve charge ahead and conc gradient causes it to diffuse further into axon, triggering depolarisaton

55
Q

Why is saltatory conduction more efficient

A

Repolarisation requires ATP and less repolarisation is necessary

56
Q

Factors affecting speed of conduction

A

Axon diameter

Temperature

57
Q

How does axon diameter affect speed of conduction

A

Bigger the axon diameter faster the transmission

Less resistance to flow in cytoplasm

58
Q

How does temperature affect speed of conduction

A

Higher the temp, faster the transmission

Ions diffuse faster at higher temp but only up to 40 degrees as proteins get denatured

59
Q

Inhibitory synapses

A

Release transmitters that lead to hyperpolarisation of the postsynaptic membrane so there’s no ap

60
Q

What is acetylcholine hydrolysed into

A

Choline and ethanoic acid

61
Q

Spatial summation

A

Several presynaptic neurones connectto postsynaptic neurones

Each releases a transmitter so the conc increases in the synapse

62
Q

Temporal summation

A

Single presynaptic neurone releases transmitter due to several ap in a short time