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LGS A-Level OCR Biology > Unit 5 - Neuronal Communication > Flashcards

Unit 5 - Neuronal Communication Flashcards

1
Q

Main functions of nervous system

A

Send, recieve and interpret info

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2
Q

Two parts of the nervous system

A

CNS

PNS

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3
Q

What is a neuron

A

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

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4
Q

Nerves vs neurons

A

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

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5
Q

Rods and cones

A

Receptors in eyes

Detect changes in light

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6
Q

Taste buds

A

Receptors on tongue

Detect change in chemical potential

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7
Q

Pacinian corpuscles

A

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

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8
Q

Ruffinis endings

A

Receptors on skin

Detect changes in heat

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9
Q

Proprioreceptors

A

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

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10
Q

What do the hair cells in semi-circular canals do

A

Detect movement

Involved in balance

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11
Q

What do the hair cells in the cochlea do

A

Detect sound

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12
Q

Transducers

A

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

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13
Q

Where is action potential summed

A

At axon hillock which is then propagated down the axon

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14
Q

Resting membrane potential

A

Potential diff across the membrane of a neuron

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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

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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

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17
Q

Need for refractory period

A

Prevents overlap of action potential

Prevents action potential from moving backward (unidirectional)

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18
Q

Receptor potentials

A

Localised changes in membrane potential

Graded and arent self-propagated

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19
Q

Mechanoreceptor

A

Pressure/ stretch opens a VG ion channel

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20
Q

Thermoreceptors

A

Temp affects enzymes controlling an ion channel

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21
Q

Chemoreceptors

A

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

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22
Q

Photoreceptors

A

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

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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

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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

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25
Nodes of Ranvier
Impulses ‘jump’ from one node to another as it travels along the neuron which speeds up the transmission
26
Axon
Singular elongated nerve fibres that transmit impulses away from the cell body. Cytoplasm surrounded by plasma membrane
27
Relay neurons
Transmit impulses between sensory and motor neurones | Many short axons and dendrons
28
Cell body
Contains nucleus surrounded by cytoplasm. Contains ER and mitochondria (involved in making neurotransmitters)
29
Dendrons
Short extensions that come from the cell body, divide into smaller branches (dendrites). Responsible for transmitting electrical impulses towards the cell body
30
Sensory neuron
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
Why do motor neurons have long axons
In order to transmit the action potential to the effectors all over the body
32
Myelination
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
Why are myelinated neurons found in the PNS
Neurons in the PNS frequently have to transmit over long distances so speed of impulse is crticital to efficient function
34
Action potential
Self regenerating depolarisation that allows excitable cells to carry a signal over a distance -60 to +40
35
Why does the pre-synaptic knob end in a bulb
To increase SA for release for acetylcholine by exocytosis
36
Why are Ca^+ channels on the pre-synaptic neuron VG
To prevent acetylcholine being released if theres no action potential
37
Touch stimulus
Distortion of Pacinian Corpuscles Causes stretch-mediated Na^+ channels to open Causes Na^+ to move in and depolarises
38
Depolarisation
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
Repolarisation
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
Hyperpolarisation
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
Threshold potential
The critical level to which a membrane potential must be depolarised to initiate an action potential -50 mV
42
Describe and explain how a resting potential is maintained
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
Describe what is happening at the cell membrane during an action potential
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
Saltory conduction
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
More intense the stimulus ...
The more frequently the neurons fire
46
Synaptic cleft
Gap between pre-synaptic and post-synaptic Neuron
47
Adaptations of post synaptic neuron
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
Transmission across the synapse
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
Role of synapses in the nervous system
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
Are relay neurons myelinated
No
51
Which neuron has dendrons
Sensory - one long one
52
Do motor neurons end at synaptic knobs as well
No, motor end plate
53
Why are mitochondria needed for transmission of impulses across the cleft
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
Propagation of action potentials
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
Why is saltatory conduction more efficient
Repolarisation requires ATP and less repolarisation is necessary
56
Factors affecting speed of conduction
Axon diameter | Temperature
57
How does axon diameter affect speed of conduction
Bigger the axon diameter faster the transmission | Less resistance to flow in cytoplasm
58
How does temperature affect speed of conduction
Higher the temp, faster the transmission | Ions diffuse faster at higher temp but only up to 40 degrees as proteins get denatured
59
Inhibitory synapses
Release transmitters that lead to hyperpolarisation of the postsynaptic membrane so there's no ap
60
What is acetylcholine hydrolysed into
Choline and ethanoic acid
61
Spatial summation
Several presynaptic neurones connectto postsynaptic neurones | Each releases a transmitter so the conc increases in the synapse
62
Temporal summation
Single presynaptic neurone releases transmitter due to several ap in a short time

LGS A-Level OCR Biology (42 decks)

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