Hormuzdi Physiology

Question 1

Which ions have an excitatory effect (depolarizing) on a cell when they influx?

Answer 1

Na+

Ca+

Question 2

Which ion has an inhibitory effect (hyperpolarizing) on a cell with influx?

Answer 2

Cl-

Question 3

Which ion has an inhibitory effect (hyperpolarizing) on a cell with efflux?

Answer 3

K+

Question 4

What would be the effect of an Na channel antagonist on neurotransmission? Give an example of a drug that works like this

Answer 4

Closes Na channel, stops Na influx, hyperpolarizing (inhibitory) effect, cell relaxes
e.g. lidocaine in anaesthesia

Question 5

Influx of which ion, in response to depolarization, causes exocytosis of neurotransmitter at the synaptic cleft?

Answer 5

Ca

Question 6

What are the 2 main types of receptor neurotransmitter can act on in the postsynaptic cell?

Answer 6

Ionotropic receptor (direct)
Metabotropic receptor (indirect)

Question 7

What is the structural/mechanical difference between ionotropic and metabotropic receptors?

Answer 7

Ionotropic = channel molecule
Metabotropic = signalling molecule

Question 8

The action of a metabotropic receptor is sufficient to illicit an action potential. True/False?

Answer 8

False

Question 9

Which receptor does ACh act on in autonomic ganglia - ionotropic or metabotropic?

Answer 9

Both!

Question 10

ACh acting on ionotropic receptors illicits a fast/slow epsp

Answer 10

ACh acting on ionotropic receptors illicits a fast epsp

Question 11

ACh acting on metabotropic receptors illicits a fast/slow epsp

Answer 11

ACh acting on metabotropic receptors illicits a slow epsp

Question 12

Out of ACh, GABA, glycine and glutamine, which are excitatory and which are inhibitory neurotransmitters?

Answer 12

Excitatory: ACh, glutamine
Inhibitory: GABA, glycine

Question 13

GABAa is the ionotropic/metabotropic receptor and GABAb is the ionotropic/metabotropic receptor

Answer 13

GABAa is the ionotropic receptor and GABAb is the metabotropic receptor

Question 14

How do benzodiazepines work in terms of GABA inhibition?

Answer 14

Positively modulate GABAa receptor to enhance GABA neuro-inhibition

Question 15

What is the normal frequency range for sound that humans can hear?

Answer 15

20-20,000 Hz

Question 16

Which ossicle converts rhythmic sound energy to mechanical energy in the middle ear?

Answer 16

Stapes at oval window

Question 17

What is impedance matching of sound?

Answer 17

Ossicles overcome loss of sound pressure caused by fluid by amplifying stimulus by 30dB

Question 18

What are the 3 fluid-filled cavities of the cochlea?

Answer 18

Scala vestibuli, tympani and media

Question 19

Which membrane separates the scala vestibuli and media?

Answer 19

Reissner’s membrane

Question 20

Which membrane separates the scala media and tympani?

Answer 20

Basilar membrane

Question 21

Which fluid - endolymph or perilymph - is present in the scala media?

Answer 21

Endolymph

Question 22

Which fluid - endolymph or perilymph - is present in the scala vestibuli?

Answer 22

Perilymph

Question 23

Which fluid - endolymph or perilymph - is present in the scala tympani?

Answer 23

Perilymph

Question 24

The basilar membrane is flexible and vibrates with fluid motion. Which end of the membrane is wider and how does this relate to pitch?

Answer 24

Wide at apex of cochlea, narrow at base

High pitch/frequency received at base

Question 25

Stereocilia transduction is caused by K efflux. True/False?

Answer 25

False! | K influx causes depolarisation in this case

Question 26

The auditory system has two types of hair cell - describe their function

Answer 26

Inner hair cells perceive sound (CN VIII) | Outer hair cells regulate sound (superior olivary complex)

Question 27

What are the two methods by which the auditory nerve codes frequency of sound?

Answer 27

``` Place code (area of basilar membrane) Temporal code (no. of action potential peaks) ```

Question 28

Which vestibular structures aid head rotation?

Answer 28

Semicircular canals

Question 29

Which vestibular structures aid translational (linear) head movement?

Answer 29

Utricle Saccule (otolith organs)

Question 30

What displaces hair cells in the vestibular labyrinth?

Answer 30

Acceleration/gravity

Question 31

List the 3 main vestibular reflexes

Answer 31

Vestibulo-ocular reflex Vestibulo-colic reflex Vestibulo-spinal reflex

Question 32

At rest, photoreceptors are depolarised. True/False?

Answer 32

True

Question 33

What causes depolarisation in photoreceptors?

Answer 33

Dark current at rest involving Na influx through cGMP channel

Question 34

What causes hyperpolarisation in photoreceptors?

Answer 34

Light causes less Na influx so Vm is closer to Ek which causes K efflux

Question 35

Which cells - ganglion, bipolar or photoreceptors - generate action potentials?

Answer 35

Ganglion cells