summary of neuro

Question 1

Features of graded potentials?

Answer 1

Local action potential variable in size that can go in both directions and often generated in dendrites of post synaptic neurons.
Transmitter gated channels.
Can be excitatory (e.g Na channels) or inhibitory (e.g. Cl-)

Question 2

How can Ohms law be used to work out the movement of ions in a solution?

Answer 2

I=Vg
V=voltage pd across the membrane
g= electrical conductance- ability of charge to move from one point to another e.g. both ions and ion channels present.

Question 3

What are equilibrium potentials? Eion

Answer 3

The membrane potential (pd) that would be achieved if the membrane was only permeable to that ion- the pd when the no. of ions moving one way due to diffusion concentration gradient is equal to the number of ions moving the other way due to electrostatic force.

Question 4

How is Eion worked out?

Answer 4

Nerst equation. (if charge of ion is 1 and at 37degrees)
61.54mv x log (ion outside/ion conc inside cell)
If charge is two divide 61.54 by 2 (30.77)
-if only permeable to that ion.

Question 5

What equation also takes into account that a membrane is not only permeable to one ion?

Answer 5

Goldman equation.

Question 6

Explain: 61.54 x log ( Pk[K outside] + Pna [Na outside]) / (Pk [k inside] + Pna [Na inside])

Answer 6

P{ion} = the permeability for that ion (in meters per second)

Question 7

Explain the equation to work out net ionic driving force?

Vm-Eion

Answer 7

Membrane potential- ions equilibrium potential

e.g. in perfect neuron Ek=vm and to find the membrane potential of Na influx will be Ek-Ena. -80-62=-142mv

Question 8

The sodium voltage gated channel has a refractory period why?

Answer 8

In order to inactivate the channel a ball inserts into the channel which takes 1msec. (absolute refractory period)
In order for this channel to be able to open again the membrane needs to repolarise and the ball to be removed (but channel still closed) called de-inactivation this takes more time also another 1ms. (relative refractory period)

Question 9

Poison that inhibits the Na channels found in puffer fish and another that’s used as a local anaesthetic?

Answer 9

Tetrodoxin- puffer fish

Lidocaine

Question 10

Why does action potential travel in only one direction?

Answer 10

Because the Na+ ions diffuse up the neurone in both directions however the channels behind are deactivated so only open the voltage gated channels in front.

Question 11

Difference between temporal or spatial summation?

Answer 11

Temporal= Many AP from same neuron
Spatial= From many different axons

Question 12

Synapse gap?

Answer 12

20-50nm gap

Question 13

WHat is quantal release?

Answer 13

neurotransmitters are released into the synapse in vesicles. This is the minimum amount of simulation one neuron can send to another. One contains 35-50nm)

Question 14

Agonists and antagonists for nicotinic and muscarinic receptors? Found?

Answer 14

Nicotinic- sympathetic post- Agonists=Nicotine, Ach Antagnoist= Curare
Muscarinic- parasympathetic post- Agonist= Ach, Muscarine, Antagonist: Atropine.

Question 15

Nicotinic and muscarinic types of receptors?

Answer 15

Nicotinic: Ion gated channel permeable to Na e.g. skeletal muscle
Muscarinic: G protein coupled receptor activating K channels e.g. heart slows down.

Question 16

4 types of receptor origins?

Answer 16

Interoceptors – Internal organs, Visceral pain, nausea, stretch
Proprioreceptors – Muscles, tendons, joints – position & movement
Nociceptors – High threshold mechano- & thermoreceptors
Exteroceptors – Vision, hearing, touch, cutaneous pain

Question 17

Three outer layers in the eye?

Answer 17

• Sclera
• Choriod
• Retina

Question 18

The sclera and cornea is made up of what?

Answer 18

Tunica fibrosa- Collagen
sclera= white,
Cornea= Transparent

Question 19

The choroid, ciliary body and iris are made up of what?

Answer 19

Tunica vasculosa

Question 20

The retina and optic nerve are made up of what?

Answer 20

Tunica interna

Question 21

Two different humours of the eye?

Answer 21

Anterior humour at front

Vitreous humour in vitreous body (big space)

Question 22

What is the lamina Cribrosa? Distorts?

Answer 22

Mesh of collagen at the posterior of the eye through hole in the sclera where the optic nerve exits.
Distorts under high pressure and compresses the optic nerve damaging blood supply. Induces degeneration of retina leading to glaucoma.

Question 23

Cataracts caused by?

Answer 23

Decreased water content in the eye. lens becomes less transparent.

Question 24

Refractive indexes of structures in the eye?

Answer 24

Cornea: 1.38
Aqueous and vitreous humour: 1.34
Lens: 1.41

Question 25

Pupillary constrictor vs dilator muscles?

Answer 25

Constrict: smooth circular muscles
Dilate: smooth radial muscles

Question 26

WHat is the photopapillary reflex?

Answer 26

Controls the diameter of the pupil.

Optic nerve> pretactal region>Edinger westphal nucleus> down oculomotor> to ciliary ganglion> to ciliary nerves.

Question 27

Emmetropia? Convergence? Miosis? Accommodation of lens in the eye?

Answer 27

Emmetropia- relaxed eye focus greater than 6m away
Convergence- eyes crossed, come together
Miosis: Constriction of pupil
Accomodation of lens- changes shape, either thin( far point relaxation of cilliary muscles) and long or short and fat (near point, contraction of ciliary muscles)

Question 28

Back to front of the eye layers?

Answer 28

Sclera, choroid, pigment epithelia (regenerate photoreceptors) rod and cone outer segments, then nuclei, bipolar cells, ganglion cells with nerve fibers to optic nerve.

Question 29

Rods vs cones in the retina?

Answer 29

Cones: Photopic (in bright light-Low light senstitivity) low convergence, high resolution, 3 types: red, green and blue. See colour
Rods: scotopic (in low light- high light sensitivity) high convergence, low resolution. peripheral rods good at 500nm wave length

Question 30

What is the Duplicity theory?

Answer 30

Can’t have high sensitivity (rods) and high resolution (cones) in a single receptor hence have two separate cells.

Question 31

Rods to optic nerve pathway? Cones difference?

Answer 31

Rods to bipolar cells to amacrine cells to converge onto a ganglion cell to optic nerve. (cones many ganglions and no amacrine cells needed)

Question 32

Different photopigments in rods and cones?

Answer 32

Rods: Rhodopsin
Cones: Photopsin

Question 33

Light strikes the ……… in Rod cells, activates the conversion of …… into ……., which activates the breakdown of ……Without this the ….. causes … channels to be open. However, with it this is hydrolysed to …. which closes the above channels. This causes a …….. of the membrane.

Answer 33

Rhodopsin, Transducin GDP to GTP. PDE (phosphodiesterase), CGMP, NA, GMP, hyperpolarisation.

Question 34

Difference in rod cells in the light vs the dark?

Answer 34

In the light the membrane becomes hyperpolarised -70mv as the Na channels close so only being pumped out, whereas in the dark membrane is at -40mv, and rod cells release glutamate.

Question 35

Difference between on bipolar cells and off?

Answer 35

on: glutamate inhibits on bipolar cells, Indirectly linked to ion channel. Hyperpolarized in the dark
Off: glutamate excites. Directly linked to ion channel. Depolarised in the dark.

Question 36

Learn ganglion cells types from folder cba to make question on this and bored of anatomy of the eye

Answer 36

Make a cup of tea and relax.

Question 37

4 types of Lingual Papillae on the tongue?

Answer 37

• Filiform= spiked,no taste just texture most common. Down centre of tongue.
• Foliate= least abundant gone by 2-3 yrs. middle edge.
• Fungiform= tip and side of tongue
• Vallate= large back of tongue contain half of all taste buds

Question 38

Which 3 cranial nerves does the tongue innervate?

Answer 38

Glossopharngeal IX, Facial VII, Vagus

Question 39

Distribution of different tasting taste buds e.g. sweet

Answer 39

Sweet and salty at the front, texture down the centre, bitter at the back and sour at the edges.

Question 40

How does the olfactory system result in depolarisation?

Answer 40

The receptor is a neuron. Odorant binds to odorant binding protein, which binds to the receptor which is an GPCR activating adenyl cyclase converting ATP to CAMP opening the NA Ca channel causing it to depolarise.

Question 41

In the olfactory bulb what’s the sequence of cells?

Answer 41

From mitral cell to tufted cell - which convey info from 2nd order neurons and integrate to other regions e.g. limbic system.