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Baz: Y1 Semester 1 > Nervous System > Flashcards

Nervous System Flashcards

1
Q

Information flow through neurons

A

Dendrites
Cell body (Soma)
Axon

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2
Q

Specialised Glial Cells

A

Astrocytes
Schwann cells

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3
Q

Astrocytes

A

Most numerous cells in the brain
Fills spaces between neurons
Regulates chemical content of the extracellular space

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4
Q

Schwann cells

A

Oligodendroglial cells

Provides myelination of axons

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5
Q

Myelin sheath

A

Insulates the axonat intervals in order to speed up action potential propagation

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6
Q

Central Nervous Systym (CNS)

A

The brain and the spinal chord

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7
Q

Peripheral Nervous System (PNS)

A

Radiates form CNS

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8
Q

Afferent vs Efferent Axons

A
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9
Q

Brain vs Spinal Chord funtions

A

Brain:

Cognition, motivation, voluntary movement, learning and memory

Spine:

Reflexive actions, fast acting that doesn’t require the brain

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10
Q

Transport of electricity in biology

A

Ions in solution (biology is based on water)

Na+,K+,Cl-,Ca2+

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11
Q

Potassium Sodium Which Has Higher Concentration Inside/Outside of cell?

A

Memomic: You do K you stay inside, if you are outside you are Na

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12
Q

Resting Membrane Potential

A

-65mV

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13
Q

How the resting membrane potential is set

A

K+ ions leave via the potassium leak channels due to there being a lower concentration outside.

This leads to a drop in the charge inside the cell. As the charge inside become lower and lower a potnetial force builds up between the inside and the postive charge outside.

Eventually this equals the force due to concentration difference and while the channel is still open equilibrium is reached around -65/70mV

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14
Q

How to record resting membrane potential

A

Can use microelectrode

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15
Q

Action potential

A

Neurons fire action potentials when stimulated.

It is a binary unit, it either propegates or it doesn’t

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16
Q

Action potential trains and firing rate

A

The frequency of the train encodes information e.g. the harder the touch the faster the train will occure

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17
Q

What are the 4 phases of an action potential

A
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18
Q

What is threshold potential?

A

This is the potential required for an action potential to occur, if this isn’t reached nothing happens.

This is around -55mV

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19
Q

What is a voltage gated sodium channel?

A

These are sodium channels which open when the threshhold potential is reached and quickly close up after approx 1ms. They are responsible for the rapid depolarisation during an action potential. They can be only be opened again when the resting potential is once again reached

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20
Q

What is a voltage gated potassium channel?

A

These are potassium channels which open approx 1ms after the threshhold potential is reached, these are responsible for the rapid reploarisation of the axon. They close up again once resting potential is reached.

These are different to the two pore potassium channels which set the resting potential, the two pore ones are always open

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21
Q

How does action potential propegate in an unmyelinated axon?

A

The axon is like a tube so it passively propagates down as the nearby action potential stimulates the next part to threshhold potential

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22
Q

What is the myelin sheath and how does it increase signal propagation?

A

Shwann cells joins together to make the myelin sheath, the gaps inbetween sections of sheath are called nodes of Ranvier. Polarisation of the axon can jump from node to node resulting in much faster propagation

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23
Q

What is saltatory conduction?

A

Saltatory conduction is the rapid node to node conduction of action potentials along myelinated axons

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24
Q

The different axons for sensory input

A
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25
Mechanosensitive ion channels
This are the channels present around mechanorecptors are they are gated depending on the stretch of the surrounding membrane
26
4 main sensory input modalities from the skin
1. Temperature 2. Touch 3. Pain 4. Pressure
27
What is a synapse?
A terminal between neurons in which they communicate through neurotransmitters. It consists of a presynaptic terminal where the transmitters are synthesised and a postsynaptic terminal where transmitters are recieved
28
How are neurotransmitters sythesised?
Enzymes produced in the neuron cell body travel down the axon, these then react with precursors to make the neurotransmitters
29
How does an action potential release neurotransmitters?
30
What is a vesticle?
This holds neurotransmitter for release during exocytosis
31
Exocytosis vs endocytosis
* Exocytosis is the fusion of a vesticle to the cell membrane thus releasing neurotransmitters * Endocytosis is the generation of new vesticles by pinching them from the membrane
32
Exocytosis/Endocytosis cycle
33
Two types of receptors
* Ionotropic - fast acting, ion channels open as soon and neuroreceptor binds * Metabotropic - slower acting, activation of a second messenger e.g. via g-protiens
34
Excitatory vs Inhibitory neurotransmitters
Excitatory neurotransmitters increase the excitability of the post synaptic neuron, inhibitatory neurotransmitters deacrease the excitability of the postsynaptic neuron
35
What is the quantal hypothesis of neurotransmission?
This is that the postsynaptic response will be quantised or discrete as opposed to continuous. This is due to the vesticles. The response will be proportional to vesticles released e.g. (1,2,3...)vesticles
36
How do excitatory neurotransmitters work?
They act on ion channels which increase the charge within the postsynaptic terminal
37
How do inhibitory neurotransmitter work?
They act on ion channels which decrease the charge within the postsynaptic terminal
38
How can multiple inputs add together to excite a neuron? ## Footnote There are two different types of summation of EPSPs
Spatial summation is the summation of EPSPs generated at different synapses Temporal summation os the summation of EPSPs generated at the same synapse
39
What EPSP stand for
Excitatory postsynaptic potential
40
Describe how the excitatory and inhibitatory synapses interact and balance
The excitatory synapse produces a depolarisation in the dendrite which passively propagates towards the soma, if there is an active inhibitory synapse present this will counteract the depolarisation produced by the excitatory synapse therefore at the soma no depolarisation is detected and the threshold potential is not reached in order to produce an action potential down the axon.
41
With regards to neuropharmocology what is an agonist and an antagonist
An agonist acts to mimic an endogenous neurotransmitter An antagonist acts to block an endogenous neurotransmitter
42
What does ANS stand for and what are it's two sub branches
Autonomic nervous system Sympathetic and parasympathetic nervous system
43
What muscles does the somatic nervous system control?
Skeletal muscle
44
What muscles does the sympathetic nervous system control and what is it's general purpose
Smooth muscle, cardiac muscle and gland cells. It is responsible for fight or flight responses
45
What muscles does the parasympathetic nervous system control and what is it's general purpose
Smooth muscle, cardiac muscle ad gland cells. Responsible for rest and digest functions and acts to counter the sympathetic nervous system
46
The origins and features of the SNS
* Short preganglionic fibres originating from the thoracic and lumbar region * These act on many different long postganglionic fibres making it very general (all or nothing)
47
What is a ganglion
A synaptic relay station between nerves
48
The origins and features of the PSNS
* Long preganglionic fibres originating from the cranial and sacral areas * These act on select short postganglionic fibres resulting in more sleective functions (e.g. can act to increase digestion while leaving heart rate alone)
49
How does the SNS and PSNS affect the different body function?
SNS * Increases heart rate * Increases breathing * Decreases digestion and urination * Stimulates energy(glucose) production and release * Constrics blood vessels PSNS * Slows heart rate * Slows breathing and constricts airways * Stimulates digestion * Stimulates energy(glucose) storage
50
What is ACh
Acetylcholine Used for muscle contraction in the somatic nervous system In the ANS released by all preganglionic neurons and the postganglionic neurons of the PSNS
51
What is released by the SNS from the postganglionic neurons?
Noradrenaline
52
Uppermotor neurons vs lower motor neurons
* Upper motor neurons are found within the spinal chord * Lower motor neurons are the ones from the spinal chord to the peripheries
53
What is a motor neuron pool
A collection of alpha motor neurons all responsible for the same muscle, if damage to one occurs then the muscle can still be innervated
54
What is the predicable organisation of lower motor neurons within the ventral horn
Ones that innervate distal muscles occur lateral to ones that innervate axial Ones that innervate flexors occur posterior to those that innervate extensors
55
What is this and what is it's function?
Sarcolemma Is the excitable cell membrane covering the muscle fibre
56
What is this and what is it's function?
Sarcoplasmic reticulum Stores calcium which when released causes contraction
57
Describe how calcium interacts with tropinins and in order for muscles to contract
Calcium binds to tropinins which in turn open up the actin filament to binidng with the myosin filament. The myosin head bends thus sliding the actin filament
58
Describe the whole story of excitation-contraction coupling from an action potential in an alpha neuron to a muscle contraction
1. AP occurs in alpha neuron 2. Motor neurons release ACh at synapses 3. ACh triggers depolarisation of the sarcolemma 4. In response to this the sarcoplasmic reticulum releases Ca2+ 5. This triggers the sliding of the actin/myosin filaments resulting in muscle contraction
59
What is a muscle twitch?
This is the response due to a single action potential If these stack you end up with full contraction
60
Where are reflexs processed?
In the spinal chord
61
What is an inhibitory interneuron
This is a neuron in the spinal CNS that inhibits an antagonist muscle while the agonist muscle is activated

Baz: Y1 Semester 1 (30 decks)

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