1.0 Introduction to Neurones Flashcards

Question 1

Q

What is the function of the medulla and pons?

Answer

A

Control regulatory systems for basic function (CVS/resp)

Question 2

Q

What is the function of the cerebellum?

Answer

A

Planning complex movements

Question 3

Q

What is the function of the midbrain?

Answer

A

Dorsal surface = tectum Contains superior and inferior colliculi Superior colliculi = visual processing Inferior colliculi = auditory processing

Question 4

Q

What is the function of the thalamus?

Answer

A

Closely linked to cerebral cortex (specific areas of cortex are linked to thalamus)

Question 5

Q

What is the function of the hypothalamus?

Answer

A

Regulator of homeostasis Controls endocrine/ANS/behaviour

Question 6

Q

What is the function of the cerebral cortex?

Answer

A

Largest part of brain Primary cortical areas = specialised for processing one modality Association cortices = receive and associate info of many modalities

Question 7

Q

What is the function of the basal ganlia?

Answer

A

Group of nuclei under the cortex Associated with learned selection and expression of beneficial beavhiour for a given circumstance

Question 8

Q

What is the function of the amygala?

Answer

A

Assessment and learning of the emotional significance of given sensory info

Question 9

Q

Function of Soma

Answer

A

Soma = cell body It is the metabolic centre of the cell Contains nucleus and ER Gives rise to dendrites and axons

Question 10

Q

Function of Dendrites

Answer

A

Receive incoming signals from other nerve cells

Question 11

Q

Function of Axon Hillock

Answer

A

Specialised part of the soma that connects it to axon. Action potentials are initiated here because it has the lowest threshold potential

Question 12

Q

Function of Axon

Answer

A

Carries signals to other neurons (can convey singles from 0.1mm to 2m)

Question 13

Q

For the following ions: 1) Sodium 2) Potassium 3) Chloride 4) Calcium What is the internal concentration, external conc. , valence, and equilibrium potential?

Answer

A

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Question 14

Q

What is the Nernst potential?

Answer

A

Membrane potential at which there is no net flux of that ion across the membrane Depends on chemical and electrical gradients

Question 15

Q

What is the Nernst equation?

Answer

A

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Question 16

Q

At rest, what ion is the membrane mainly permeable to?

Answer

A

Potassium (K⁺)

Question 17

Q

What is the Donnan equilibrium?

Answer

A

If a membrane is permeable to both K⁺ and Cl⁻, they will move across until their concentration gradient is balanced by membrane potential. Therefore if equilibrium is reached: [K⁺]i x [Cl⁻]i = [K⁺]o x [Cl⁻]o

Question 18

Q

What two secondary active processes are used to extrude Cl⁻:

Answer

A

1) KCC2 2) NDCBE Therefore ECl is usually more negative than membrane potential

Question 19

Q

What two neurons have increased internal [Cl⁻]?

Answer

A

1) Developing neurones 2) Adult olfactory receptor neurones Therefore opening of Cl⁻ channels → outward (excitatory) current

Question 20

Q

3 mechanisms by which calcium is extruded from the cell?

Answer

A

1) ATP-fuelled Ca²⁺ pump 2) NCX 3) NCKX

Question 21

Q

What are the steps for neurotransmitter release?

Answer

A

1) AP reaches nerve terminal 2) Opening of voltage gated Ca²⁺ channels 3) ↑ [Ca²⁺]i 4) Fusion of vesicles with membrane

Question 22

Q

What proteins are needed for vesicle fusion with plasma membrane?

Answer

A

1) v-SNAREs (synaptobrevin) 2) t-SNAREs (SNAP-25 and Syntaxin) 3) Synaptotagmin (Ca²⁺ sensor)

Question 23

Q

What are the stages for vesicle fusion with plasma membrane?

Answer

A

1) Vesicle docks at presynaptic active zone 2) Vesicle is primed by close association between v-SNAREs and t-SNAREs 3) Vesicles fuse with plasma membrane in Ca²⁺ dependent manner

Question 24

Q

3 criteria needed for a substance to be considered a neurotransmitter

Answer

A

1) Present at pre-synaptic terminal 2) Released during stimulation 3) Must have same effect when exogenously applied

Question 25

Q

What are the two types of neurotransmitter receptors?

Answer

A

Ionotropic - Direct mechanism of action - Ionic channels - Rapid - Can allow Ca²⁺ influx Metabotropic - Indirect mechanisms - Uses 2nd messengers - Effect is usually via α-subunit bound to GTP - Can also be due to βγ (usually acting on K⁺ channels) - Results in amplification

Question 26

Q

List 3 amino acid neurotransmitters:

Answer

A

Glutamate GABA Glycine

Question 27

Q

List 5 biogenic amine neurotransmitters:

Answer

A

ACh NA Dopamine Serotonin Histamine

Question 28

Q

List 2 purine neurotransmitters:

Answer

A

ATP Adenosine

Question 29

Q

List 2 gaseotransmitters:

Answer

A

NO CO

Question 30

Q

What is the mechanism of the NMDA receptor?

Answer

A

Glutamate ionotropic receptor Causes depolarisation Permeable to Ca²⁺ + Na⁺ At -ve potentials channel is blocked by Mg²⁺ When depolarised, membrane is relieved and Na⁺ + Ca²⁺ can pass

Question 31

Q

What is the mechanism of the AMPA receptor?

Answer

A

Glutamate ionotropic receptor Causes depolarisation Permeable to Na⁺ + K⁺ Impermeable to divalent ions

Question 32

Q

What is the mechanism of the β adrenergic receptor?

Answer

A

Adrenergic metabotropic recetor Gαs coupled → activation of adenylyl cyclase → ↑cAMP

Question 33

Q

What is the mechanism of the nACH receptor?

Answer

A

ACh ionotropic receptor Causes depolarisation Permeable to Na⁺ + K⁺

Question 34

Q

What is the mechanism of the Glycine receptor?

Answer

A

Glycine ionotropic receptor Causes hyperpolarisation Permeable to Cl⁻

Question 35

Q

What is the mechanism of the GABA-A receptor?

Answer

A

GABAionotropic receptor Causes hyperpolarisation Permeable to Cl⁻ + K⁺

Question 36

Q

Long sensory receptors vs short sensory receptors

Answer

A

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Question 37

Q

Direct transduction vs indirect transduction

Answer

A

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Question 38

Q

Define accessory structures:

Answer

A

Structures that can modify the sensitivity, selectivity, time course or response of a receptor

Question 39

Q

Examples of accessory structures:

Answer

A

1) Lens (focuses image onto retina) 2) Lamellae in Pacinian corpuscules (allow rapid adaptation)

Question 40

Q

Ionic basis of excitatory post-synaptic potential

Answer

A

Glutamate ion channel (permeable to Na⁺ + K⁺) Reversal potential = 0mV Opening of channel → membrane potential is drawn closer to reversal potential and depolarizing the cell

Question 41

Q

Ionic basis of inhibitory post-synaptic potential

Answer

A

Caused by release of glycine or GABA Glycine ↑ Cl⁻ conduction → hyperpolarisation Reversal potential = -80mV GABA ↑ Cl⁻ + K⁺ conductance → hyperpolarisation

Question 42

Q

Type I vs Type II synaptic inputs

Answer

A

Type I Excitatory Found on spine and shaft Round vesicles Type II Inhibitory Flat vesicles Found on soma

Question 43

Q

Where does initiation of AP occur?

Answer

A

Axon hillock (this region has the lowest threshold)

Question 44

Q

What is space constant?

Answer

A

“Distance at which 63% of Vmax is lost Larger space constant favours spatial summation<div> </div><div><img></img></div>”

Question 45

Q

What is time constant?

Answer

A

“Time taken for 63% of Vmax to be lost Larger time constant favours temporal summation<div> </div><div><img></img></div>”

Question 46

Q

What is spatial summation?

Answer

A

When two or more APs arrive simultaneously from different pre-synaptic neurons. Post-synaptic potentials add together. Allows control as inhibitory and excitatory inputs can be collated together and APs only fire is threshold is reached. ↑ space constant favours spatial summation

Question 47

Q

What is temporal summation?

Answer

A

When two or more APs arrive in rapid succession from same pre-synaptic neuron. Post-synaptic potentials add together. Allows APs to initiate in situations of high frequency stimulation of the receptor (successive excitatory post-synaptic potentials take membrane potential to threshold) ↑ time constant favours temporal summation

Question 48

Q

What is shunting inhibition? (what is significance of location of inhibitory and excitatory inputs?)

Answer

A

When an excitatory current and an inhibitory current synapse on the same dendrite, the current becomes divided Much less excitatory current is available than would be expected (↓ inhibitory current is needed to dissipate excitation) This is why excitatory inputs are further away on dendrites compared to inhibitory inputs on soma

Question 49

Q

What is presynaptic inhibition?

Answer

A

Axo-axonic synapse where inhibitory neuron synapses with axon of another neuron and prevents neurotransmitter release This offers powerful control over synaptic transmitter release Inhibitory signal must occur at same time as action potential Cl⁻ + K⁺ channel opening → ↓ AP → ↓ Ca²⁺ influx → ↓ neurotransmitter release → preventing neuron from generating EPSP

Question 50

Q

What is the A current?

Answer

A

Inactivating K⁺ current Inactivated with depolarisation Function = spaces spikes in spike train (it leads to a graded change in frequency that is dependent on the initial depolarising current* Ik - takes membrane potential back to resting levels A current - keeps membrane potential at resting levels by opposing depolarising current. But a greater depolarisation → quicker inactivation of the A current → more frequent spikes

Question 51

Q

What are the different Ca²⁺ channels?

Answer

A

T Transient Threshold = -65mV Inactivates with moderate speed (20-50ms) Function = Rhythmic burst firing L Long lasting Threshold = -20mV Inactivates with very slow speed (>500ms) Function = Synaptic transmission + dendritic Ca²⁺ spikes N Neither Threshold = -20mV Inactivates with moderate speed (50-80ms) Function = synaptic transmission + dendritic Ca²⁺ spikes P Purkinje Threshold = -50mV Function = dendritic Ca²⁺ spikes

Question 52

Q

What is divergence?

Answer

A

One presynaptic neuron synapses with multiple post-synaptic neurons

Question 53

Q

What is convergence?

Answer

A

Multiple presynaptic neurons synapse with one post-synaptic neuron Can be important for excitation as one EPSP may not be enough to reach threshold

Question 54

Q

What is subliminal fringe?

Answer

A

“Excitatory input to a motor neuron pool can cause some neurons to reach threshold (via spatial summation) Some neurons are excited but not enough to reach threshold. These are called the subliminal fringe (Neurons within the motor neuron pool that are stimulated, but not sufficiently to reach firing threshold) Overlap of 2x subliminal fringes → summation in a supra-linear manner<div> </div><div><img></img></div>”

Question 55

Q

What is feedforward inhibition?

Answer

A

Pathway to antagonist is inhibited when agonist pathway is stimulated (e.g. inhibition of extensor muscles when flexors are stumulated)

Question 56

Q

What is feedback inhibition?

Answer

A

Excitatory cell contains an inhibitory interneuron which inhibits its own firing (and that of synergistic neurons) Example = Renshaw cell of spinal cord (stabilises motor neuron firing)

Question 57

Q

Describe the flexor withdrawal reflex

Answer

A

Stimulation of cutaneous nociceptors → 1) Inhibition of extensors 2) Stimulation of flexors Above two responses → withdraw limb from harm

Question 58

Q

Describe to crossed extensor reflex

Answer

A

Nociception → 1) Stimulation of contralateral extensors 2) Inhibition of contralateral flexors Above two responses → provides support

Question 59

Q

What is synaptic facilitation?

Answer

A

Repeated stimulation → enhanced post-synaptic potential Due to ↑ Ca²⁺ within the terminal → ↑ transmitter release

Question 60

Q

What is synaptic depression?

Answer

A

Repeated tetanic stimulation → depression Due to depletion of vesicle pool

Question 61

Q

What is post-tetanic potentiation?

Answer

A

Following cessation of tetanic stimulation + recover from depression, the post-synaptic response is transiently enhanced This is due to actions of Ca²⁺ on vesicle priming (can persist for several minutes after stimulation)

Question 62

Q

What is long-term potentiation?

Answer

A

Very long lasting changes in excitability following stimulation. Can occur when 2 inputs are stimulated at the same time

Question 63

Q

What is Hebb’s Law?

Answer

A

An input is strengthened when it plays a role in firing of the target cell

Question 64

Q

What is the Bruce Effect?

Answer

A

Female mouse learns the odour of a familiar male mouse who mated with her. If, within a few days, the pregnant mouse is exposed to the odour of an unfamiliar male, the fetus is aborted However, exposure to the pheremones of the mated male does not terminate pregnancy Mechanism: 1) A specific mitral cell is activated by the odour of the familiar male, and releases glutamate in response 2) Glutamate stimulates adjacent granule and peri-glomerular cells, and granules cells promote reciprical inhibition of the stimulating mitral cell with GABA 3) During mating, noradrenaline acts on adrenergic receptors on both the granule cell and mitral cell to reduce GABA release, such that the specific mitral cells responding to the mated male odour is strongly activated 4) Following this strong activation, inhibition of the synapses stimulated by the male odour is strongly enhanced, which prevents pregnancy block