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A Level Biology > Neuronal Communication > Flashcards

Neuronal Communication Flashcards

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1
Q

dendrons branch off into?

A

dendrites

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2
Q

dendrites ?

A

:Connect to the synaptic knob of the previous neuron, allowing an impulse to be received.

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3
Q

all neurones have?

A

a cell body - which contains a nucleus and other organelles

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4
Q

axon?

A

Carries neurones away from the cell body to the synapses

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5
Q

synapses?

A

lie at the end of the axon and pass the AP onto the next cell

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6
Q

the central nervous system is composed of?

A

the brain and the spinal cord

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7
Q

describe a sensory neurone?

A
  • An axon on one side of the cell body and a dendron on the other side of the cell body
  • cell body is in the MIDDLE
  • kind of looks like a spider
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8
Q

how do signals travel in a sensory neurone?

A

from the dendron (to cell body) then to the axon and onto the next neurone

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9
Q

relay/ intermediate neurones?

A

carry nerve impulses between neurones

- often have highly branched dendrites and axons

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10
Q

effectors?

A

cells that carry out the response, are muscles or glands

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11
Q

Neurons?

A
  • Responsible for the detection of stimulus, relay of impulse and stimulation of response.
  • Allow for rapid changes in an organisms internal and external environment.
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12
Q

Dendron:

A

Long nerve fibre extension leading to the cell body.

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13
Q

Cell Body:

A

Contains nucleus, mitochondria, endoplasmic reticulum and neurotransmitters

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14
Q

Axon:

A

Long nerve fibre extension from the cell body through which impulses are transferred. Surrounded by a plasma membrane.

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15
Q

Myelin Sheath:

A

Myelinated tissue which insulates the nerve fibre helping the impulse travel more quickly.

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16
Q

Nodes of Ranvier:

A

Gaps in the myelin sheath which only allow depolarisation to occur at distanced intervals, speeding up transmission.

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17
Q

Synaptic Knob:

A

Neurotransmitters are released from here into the synaptic cleft when action potential stimulates an influx of calcium ions.

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18
Q

what do sensory neurones do?

A

transmit impulses from a sensory receptor cell to a relay or motor neuron.

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19
Q

Motor Neurons:

A

Transmit impulses from a relay neuron or sensory neuron to an effector cell such as a muscle or gland.

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20
Q

sensory receptors?

A

specialised cells in the NS that detect physical stimuli

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21
Q

transducers?

A

cells that convert one form of energy into another

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22
Q

sensory receptors role?

A

convert a type of energy e.g. light into electrical signals.

- These electrical signals are called the generator potential

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23
Q

a generator potential?

A

is the depolarisation of the membrane of a receptor cell

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24
Q

dendrites?

A
  • dendrons branch into these

dendrites receive signals

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25
Q

how was the resting potential and action potential discovered?

A

Hodgkin, Huxley and the giant axons of squid. 1952.

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26
Q

RP value?

A

-70mV

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27
Q

what does the nervous system allow?

A

us to react to our surroundings and co-ordinate our behaviour

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28
Q

the parts that comprise our NS?

A
  • Brain
  • spinal cord which runs through the spine (CNS)
  • peripheral NS - the NS outside the CNS
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29
Q

We have sense organs which?

A

relate stimuli e.g. heat, pain, noise receptors

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30
Q

Sensory receptors?

A

tend to be found in sense organs, convert diff forms of energy into APs. They act as transducers.

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31
Q

chemical energy ?

A
  • the energy input causes a change in the membrane potential of the sensory receptor cell
  • this potential is causes by the difference in the conc of ions across the membrane
  • it can be described as ‘chemical potential energy’ bc the ions are charged
  • can be measured as a tiny voltage
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32
Q

e.g.s of sensory receptors?

A
  • hair cells in the cochlea - convert sound energy into APs

- Stretch receptors (cells in muscles and joints) - convert KE into APs

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33
Q

what is the difference between nerve and neuron?

A

neuron = single

nerve = bundle of neurons (packaged) surrounded by a protective layer called the perineum

neurons = nerve cells

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34
Q

3 types of neurons are?

A
  • motor
  • sensory
  • intermediate (relay)
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35
Q

what do motor neurons do?

A
  • carry APs away from the CNS (they say “mmm see ya to the CNS” to muscles/ glands
  • effectors can the response
  • efferent - away from CNS (eff off)
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36
Q

What do sensory neurons do?

A

carry nerve impulses to CNS (can only hear a snake when its coming towards you)

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37
Q

what do intermediate neurons do?

A

carry APs within the CNS

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38
Q

MNs: facts

A
  • the dendron can / into multiple terminal branches which synapse with the effector
  • each synaptic bulb touches a muscle/ gland
  • one output along a long axon, but multiple inputs from multiple RN in CNS
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39
Q

dendrons?

A

carry to the CB

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40
Q

Dendrites?

A

Come off dendrons

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41
Q

cell body?

A

Contains nucleus and all other organelles

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42
Q

axon?

A

Carries away from the CB. Can be μm -m long.

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43
Q

terminal branches lead to?

A

synaptic bulbs

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44
Q

generator potential?

A

a depolarisation in a SN caused by a stimulus e.g. pressure. If the generator potential reaches threshold potential then APs are generated.

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45
Q

Pacinian corpuscle?

A

a pressure sensitive receptor

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46
Q

SN in relation to CNS

A
  • the cell body of a SN is found in the dorsal root ganglion of the spinal cord
  • a stimulus causes APs to be generated at the dendrites of a SN
  • CARRY AFFERENT APs FROM sensory receptors in the PNS ➡ CNS
  • spidery looking
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47
Q

Intermediate Neuron info?

A
  • the majority of CNS is formed from them
  • each neuron can be connected to up to 10k others
  • multiple inputs from multiple dendrites from SN/ other IN
  • 1 output via dendron which can / into multiple terminal branches
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48
Q

interconnected INs carry out …

A

the processing and co-ordination of the afferent and efferent APs - the input and output

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49
Q

SRCER

A

some riders can eat rats

stimuli ➡ receptor ➡ (via SN) CNS (RN)➡ (via motor neuron) effector) ➡ response

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50
Q

response is usually?

A

a skeletal muscle contracting

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51
Q

which type of neuron are never myelinated?

A

IN

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52
Q

Myelination?

A
  • about 1/3 of all of our MN & SN are myelinated
  • Myelin sheath is made up of Schwann cells (20 layers of membranes)
  • insulate the axon and ⬆ the speed of the impulse by up to x100
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53
Q

how does myelination keep the membrane in place?

A

They increase the proportion of cholesterol in the membrane

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54
Q

myelinated dendrons?

A
  • myelinated dendrons and axons are wrapped in Schwann cells which form the myelin sheath
  • in between Schwann cells are gaps called nodes of Ranvier where the plasma membrane of the neuron is exposed
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55
Q

the reflex arc?

A
  • the simplest way 3 neurons can be connected
  • w/o conscious thought (bypasses the brain)
  • other neurons will be simulated to the brain after the response
56
Q

why does some matter appear white and some grey in the reflex arc?

A

grey = almost all INs no myelination

white matter = lot of myelin sheath, high level of fat

57
Q

ganglion means?

A

swelling

58
Q

resting potential?

A
  • the inside is always slightly negatively charged compared to the outside
    the diff is called the potential difference which is at around -70mV at rest
59
Q

what causes the RP?

A

The RP is maintained. caused by the sodium/ potassium pump in the membrane of axons

60
Q

the Na+/K+ pump?

A
  • 3 Na+ picked up via carrier proteins and placed outside
  • at the same time, 2K+ are brought in (both move against conc gradient so ATP required
  • causes outside the axon to be more +ve than inside
  • called an electrochemical gradient
  • some ions leak back (mainly K+) leaving outside more negative compared to inside (less + than outside NOT - charged)
61
Q

Rp value?

A

-70mV

62
Q

voltage gated channels?

A
  • channels in the membrane which change the permeability to Na+/K+
  • they open and close in response to voltage changes across the membrane
63
Q

sequence of events after a stimulus is detected?

A
  • RP
  • depolarisation
  • threshold reached
  • repolarisation
  • hyperpolarisation
  • RP
64
Q

Hyperpolarisation?

A

time taken for K+ VGC to close

65
Q

what is a localised circuit/ local circuit?

A

the AP is occurring at just one point on the axon

66
Q

how is depolarisation an e.g. of positive feedback?

A
  • the opening of Na+ VGC causes the membrane to become more depolarised
  • which causes more Na+VGC to open
  • which causes the membrane to become more depolarised
67
Q

depolarisation?

A

change within a cell during which the cell undergoes a shift in electric charge distribution resulting in a less - charge inside the cell.

68
Q

Transmission of an AP?

A
  • At a localised circuit, there is an increased conc of Na+ inside the axon
  • these Na+ will diffuse quickly down a conc gradient (electrochemical gradient) to the neighbouring regions of the axon
  • this depolarises the section next to it causing Na+VGC o open
  • this causes a further influx
  • this causes a start of an AP (and so on)
69
Q

(transmission of an AP) reality

A

In reality, this only happens ahead of the last AP because the section behind is recovering from the last AP (overshoot) & will not be back to normal yet. This recovery period is called the refractory period.

70
Q

Speed of conduction of a myelinated vs unmyelinated neuron?

A
  • Myelinated up to 100 m^s-1

- Unmyelinated around 1ms^-1 (some as slow as 0.5ms^-1)

71
Q

Myelinated neurons and the node of Ranvier?

A
  • Myelinated neurons are insulated - Na+ K+ can’t go thru these regions
  • AP can only occur at the Node of Ranvier (node to node 1-3mm)
  • This is called saltatory conduction
72
Q

saltatory conduction?

A

where the AP jumps from node to node. This speeds up tranimssion and saves ATP (so there are less Na/k+ pumps), less leakage of K+

73
Q

What impact does diameter have on speed of conduction?

A
  • bigger the diameter ➡ faster transmission (less resistance to flow & less leakage)
    = larger = smaller SA:V ratio of membrane
  • cell body contains organelles. if larger, Na+ more likely to bump into organelles
74
Q

how do we ensure that the AP only goes one way?

A
  • when Na+ come in through NaVGC, it diffuses along the axon
  • once depolarisation happens, NaVGC have a refractory period - cannot open
  • this ensures AP only goes one way
75
Q

how does temp affect speed of conduction?

A

increases it due to increased KE (but over 40 degrees denatures the channels)

76
Q

what is all or nothing?

A
  • either the stimulus causes an AP or it doesn’t
  • If the stimulus is strong enough., it causes Na+VGC to open for long enough to cause depolarisation (allows a potential difference of around -55mV)
  • The min change needed to start an AP is called a threshold value
77
Q

How does our brain know if it was a strong or light touch?

A
  • the freq of an AP
  • increased freq for strong stimuli
  • strong stimuli will stimulate more receptors (neurons, brain interprets the frequency and no. of neurons)
78
Q

how does the brain tell between APs?

A
  • All APs are the same whether they’re to light, smell, touch
  • It’s the area of the brain that the APs arrive at that determines the nature of the stimulus
  • e.g. light (stimuli): Rods and cones so brain interprets from the eye
79
Q

what is a synapse?

A

where 2 neurons meet, it’s a gap

80
Q

Presynaptic neuron ➡

A

Presynaptic neuron ➡ synapse ➡ post synaptic

81
Q

What is the difference between the synapse and synaptic cleft?

A

Synapse = ends of neurons and gap

Synaptic cleft - just gap

82
Q

how is the message transmitted at a synapse?

A

NT molecules

83
Q

no ? at the synapse?

A

No nucleus. It’s only in the cell body.

84
Q

What is the key player in synaptic transmission ?

A

Ca2+

85
Q

what else is there at the synapse?

A
  • Na+/K+ VGC

- Na+/K+ pumps

86
Q

what do receptors on the post synaptic neuron do?

A

open channels

87
Q

neurotransmitters?

A
  • many different (40)

- most common: Acetylcholine (Ach), glutamic acid

88
Q

if Ach is the NT, then the synapse is?

A

cholinergic

89
Q

e.g. of a cholinergic synapse?

A

the neuromuscular junction

90
Q

if noradrenaline is the NT?

A

the synapse is adrenergic synapse

91
Q

Role of the synapse?

A
  • communication
  • ensuring unidirectional transmission of an AP
  • synaptic convergence & divergence
  • summation and decision making
92
Q

how does the synapse ensure the unidirectional transmission of AP?

A
  • no receptors for NT on he presynaptic neuron, no Ach can bind, no AP generated
  • No Ach vesicles in the post synaptic neuron, can’t be released into synapse
  • local circuits in presynaptic neuron in refractory period
93
Q

2 types of NT?

A
  • excitatory

- inhibitory

94
Q

Excitatory NT?

A

Open Na+ channels, causing more Na+ to enter - more likely that post synaptic neuron will depolarise

95
Q

Inhibitory NT?

A

less Na+, less chance of depolarisation

96
Q

E.g. of NT: Ach?

A
  • used by spinal cord neurons to control muscles and by many neurons in the brain to regulate memory
  • excitatory in most cases
97
Q

E.g. of NT: Dopamine?

A
  • produces feelings of pleasure when released by the brain reward system
  • multiple functions depending on where in the brain it acts
  • usually inhibitory
98
Q

E.g. of NT: Norepinephrine?

A
  • acts as NT & hormone
  • in the peripheral NS, it’s part of the fight/ flight response
  • in brain, acts as NT, regulating normal brain processes
  • usually excitatory but inhibitory in some areas
99
Q

E.g. of NT: GABA

A

the major NT in the brain

100
Q

how many other neurons can 1 neuron communicate with and receive signals?

A

1000s

101
Q

Synaptic convergence?

A
  • Come together
  • multiple sensory inputs
  • 1 output causing
102
Q

synaptic divergence?

A
  • 1 input

- multiple outputs

103
Q

so divergence and convergence are?

A

opposites

104
Q

Summation?

A
  • whether synapses are inhibitory or excitatory depends on the NT involved or the type of post synaptic protein
  • sometimes an AP doesn’t automatically cause another AP, but does cause a post synaptic potential (PSP)
  • These ‘blips’ of voltage can be ESPS - a depolarisation towards threshold
  • or ISPS - a hyperpolarisation away from threshold
105
Q

These PSPs…

A
  • summate (Add together) at a synapse

- If threshold is reached, then an AP is generated in the post SN.

106
Q

how can summation occur?

A
  • in space: spatial summation

- in time: temporal summation

107
Q

spatial summation?

A
  • summation can occur in space

- APs arriving from diff areas of the body

108
Q

temporal summation?

A
  • summation can occur in time

- APs arriving at different frequencies from the same place

109
Q

whether a post synaptic cell generates an AP is controlled

A
  • by spatial and temporal summation of ESPS & ISPS

- This concept also explains how synapses filter out low levels of sensory stimulation

110
Q

stimulant drugs?

A
  • if a drug amplifies the effect of the NT at a synapse= stimulant
  • drugs that stimulate the NS create more APs in the post SN resulting in an enhanced response
111
Q

inhibitory drugs?

A
  • if a drug inhibits the effect of the NT at a synapse = inhibitor
112
Q

the effect of other chemicals at the synapse?

A
  • many drugs cause their effects by acting at synapses

- this will result in the NS being stimulated/ inhibited

113
Q

stimulant drugs may work by?

A
  • mimicking the shape of NT (e.g. nicotine is the same shape as Ach so can bind instead)
  • stimulating the release of more NT
  • inhibiting the enzyme responsible for breaking down the NT in the synapse
114
Q

drugs that inhibit the NS….

A

create fewer APs in the post SN, resulting in a ⬇ response

115
Q

inhibitory drugs may work by?

A
  • blocking receptors - NT can no longer bind & activate receptor
  • Binding to spec receptors on the post membrane and changing the shape of the receptor
  • preventing the release of NT from pre SN cell
116
Q

synaptic transmission: what happens to excess ACh?

A
  • to prevent over stimulation, Ach is broken down by Ach esterase
  • which changes its shape so it can’t bind to the receptor
  • Ach re-enters cell and reused - requires ATP
117
Q

Temporal summation alt wording

A

might need repeated signals to release enough Ach to open enough Na+ channels to allow enough Na+ in so threshold can be reached

118
Q

order of events in the generation of an AP?

A
  1. sodium potassium pump
  2. depolarisation (Na+ VGC)
  3. repolarisation (K+ VGC)
  4. PR
119
Q

Continuous conduction?

A

opp of saltatory conduction, happens in unmyelinated neurons

120
Q

the effect of other chemicals at the synapse?

A

Atropine: blocks Ach receptors on post SN membrane

Curare: competes w Ach preventing the opening of post synaptic Na+ ion channels

121
Q

organs and cells that detect sight?

A

organ: eye
cell: rods and cones

122
Q

organs and cells that detect smell?

A

organ: nose
cell: olfactory cells

123
Q

organs and cells that detect taste?

A

organ: tongue
cell: taste receptor cells

124
Q

organs and cells that detect touch?

A

organ: skin
cell: mechanoreceptors

125
Q

organs and cells that detect sound?

A

organ: ears
cell: hair cells in the ear

126
Q

The spinal reflex arc?

A

receptor ➡ enter CNS through dorsal root ➡ motor neurons leave through ventral root ➡ effector

127
Q

dorsal route?

A

sensory neurons enter

128
Q

grey matter?

A

contains almost all intermediate neurons - mostly cell bodies

129
Q

CNS?

A

sends APs down a motor neuron to effector

130
Q

white matter?~

A

a lot of myelin sheath - high level of fat

131
Q

ventral route?

A

motor neurons leave via ventral route

132
Q

SN

A
  • Stimuli causes APs to be generated at the dendrites of a SN
  • the cell body of a SN is found in the dorsal root ganglion of the SC
  • terminal ranches synapse w RN in the CNS
133
Q

what do neurons do generally/

A

carry electrical signals in the NS. The NS is just a collection of neurons

134
Q

sensory receptors?

A

specialised cells in the NS that detect physical stimuli

135
Q

Pacinian corpuscle?

A
  • pressure receptors in the skin that detect pressure changes
  • when pressure is detected, it deforms
  • this results in electrical signals in the sensory neuron
  • signals are sent during deformation, but after a while the signals stop

A Level Biology (28 decks)

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