neurones

Question 1

what is voltage

Answer 1

the difference in electric potential energy per unit charge between two points

Question 2

what is current

Answer 2

a flow of electric charge through a medium (through a surface)

Question 3

what is a resistance

Answer 3

the opposition to the passage of an electric current; the inverse quantity is electrical conductance (g), measuring how easily electricity flows along a certain path

Question 4

what is conductance

Answer 4

1/R – ability to conduct electric current

Question 5

what is ohms law

Answer 5

V = I x R
I = V x g
(if you multiply the force on an ionic species (voltage) by the ability of it to be conducted forward (conductance = g), the result is the current that actually can flow per second

Question 6

what is membrane potential

Answer 6

A measurement of the overall electrical potential energy across the membrane

Question 7

what does membrane potential depend on

Answer 7

Vm depends on the relative electrical current and conductance of different ions

Question 8

what happens when ion channels open- neurones

Answer 8

[Na+] is higher outside the cell so when the channels open, Na+ flows inside the cell and the membrane tends to become positive (inside)
[K+] is higher inside the cell so when the channels open, K+ flows to outside and the membrane becomes negative (inside)

Question 9

what is equilibrium potential

Answer 9

whenever ion channels for that ion open, the membrane potential moves toward that ion’s equilibrium potential

Question 10

what is Ena

Answer 10

+60mV

Question 11

what is Ek

Answer 11

-90mV

Question 12

what is Eca

Answer 12

+123mV

Question 13

what is ECl

Answer 13

-40mV (-65mV neurones)

Question 14

what is action potential

Answer 14

rapid changes in the membrane potential that spread rapidly along the nerve fibre membrane

Question 15

at rest what is the membrane potential and what is the membrane more permeable to

Answer 15

-70 to -90 mV
membrane more permeable to K+

Question 16

at action potential what is the membrane potential and what is the membrane more permeable to

Answer 16

+20 to +40mV
membrane temporarily more permabe to Na+, Ca2+ or both

Question 17

what are the stages of action potential

Answer 17

stimulus reaches threshold
depolarisation
repolarisation
refactory period-hyperpolarisation
resting

Question 18

what is the resting stage

Answer 18

: K+ that is going out of cell clamps the membrane potential negative

Question 19

what is the initial depolarisation

Answer 19

Depolarisation: inside the cell the voltage becomes less negative (or more positive)
Could be a nearby cell depolarising
Could be synaptic transmission where a neurotransmitter opens a ligand-gated channel

Question 20

what happens if the stimulus is below the threshold

Answer 20

Background K+ permeability pulls Vm back resting stage
This is a “failed initiation”

Question 21

what is the positive feedback of depolarisation

Answer 21

The initial depolarisation causes a few of the Na+ channels to open
The additional current of Na+ going into the cell
more depolarisation
This acts as a positive feedback loop
When the voltage goes above the threshold voltage the cell is committed to an AP

Question 22

what is repolarisation

Answer 22

Na+ channel inactivation decreased Na+ current going in
Delayed rectifier K+ channels open increased K+ going out
These cause the membrane to be less positive and more negative inside

Question 23

what is hyperpolarisation

Answer 23

the voltage inside temporarily becomes slightly more negative than at rest
increased K+ permeability and decreased Na+ permeability
the membrane potential becomes even more negative
causes refractory period

Question 24

what happens to the synapse when an action potential is caused

Answer 24

When Vm becomes positive inside during action potential, calcium channels open
Increase influx of Ca2+

Question 25

what is a neurotransmitter

Answer 25

Endogenous chemical Released extracellularly by a neuron Used to signal to other neurons, myocytes, endocrine cells,… Under physiological conditions

Question 26

what is the life cycle of a neurotransmitter in the presynaptic neurone

Answer 26

Synthesis In the soma (cell body) or locally in the axon terminal Sometimes instead of synthesis it is recycled (after use) Storage Transported into a vesicle for storage (synaptic vesicle) Membrane depolarisation and activation of voltage-gated Ca2+ channels Vesicle Transport and Fusion with the membrane Release

Question 27

what is the life of a neurotransmitter at the post synaptic neurone

Answer 27

Diffusion across the synaptic cleft Action on post-synaptic cell Activation of specific receptors Excitatory or inhibitory inputs Open ion channel – if Na+, will cause depolarisation in the post-synaptic cell Any of the different types of receptors Signal termination Removal of transmitter from synaptic cleft  Degradation by enzymes Recycled into the presynaptic cells - reuptake

Question 28

when does synthesis of neurotransmitters stop

Answer 28

Synthesis stops depending the enzymes present in the neuron / cell

Question 29

what is noradrenaline secreted by

Answer 29

sympathetic nerve terminals

Question 30

what is adrenaline secreted by

Answer 30

secreted by chromaffin cells in the adrenal medulla

Question 31

what are types of adrenoreceptors

Answer 31

a and b

Question 32

what are features of α-adrenoceptors

Answer 32

α1, α2 (post-/pre-synaptic) Blood vessels of organs and tissues except skeletal muscle vessels Agonists: NA, Adr, isoprenaline Antagonist: phentolamine

Question 33

what are features of β-adrenoceptors

Answer 33

β1 (myocardium), β2 (bronchi, uterus, muscle and coronary vessels), β3 (adipose tissue, bladder, gallbladder) Agonists: Isoprenaline, Adr, NA Antagonist: propranolol Sensitive to up/down regulation

Question 34

what is the 2nd messenger system of a1 receptors

Answer 34

Gaq

Question 35

what is the 2nd messenger system of a2 receptors

Answer 35

Gai

Question 36

what is the 2nd messenger system of B1/2/3

Answer 36

Gas

Question 37

which adrenoreceptor causes smooth muscle contraction/ vasoconstriction

Answer 37

A1- in blood vessels

Question 38

which adrenoreceptor causes GI smooth muscle relaxation

Answer 38

A1

Question 39

which adrenoreceptor causes GI sphincteric muscle / bladder sphincter contraction

Answer 39

a1

Question 40

which adrenoreceptor causes glycogenolysis in the liver

Answer 40

a1/b1

Question 41

which adrenoreceptor causes decreased neurotransmitter release in the presynaptic sympathetic neurones

Answer 41

a2

Question 42

which adrenoreceptor causes increased heart rate and force of contraction

Answer 42

B1

Question 43

which adrenoreceptor causes dilation/relaxation in the bronchi and blood vessels

Answer 43

b2

Question 44

which adrenoreceptor causes tremor and glycogenesis in skeletal muscle

Answer 44

b2

Question 45

which adrenoreceptor causes lipolysis, thermogenesis in adipose tissue and skeletal muscle

Answer 45

b3

Question 46

which adrenoreceptor causes relaxation - preventing urination in the bladder

Answer 46

b3

Question 47

what is the pathway of ACH

Answer 47

Synthesis in the cytosol Storage Vesicle Transport and Fusion with the membrane Release Diffusion across the synaptic cleft Action on post-synaptic cell – receptors Signal termination Metabolism by cholinesterase:

Question 48

what are metabotropic receptors (GPCR)

Answer 48

Metabotropic (GPCR) Located postsynaptically in the smooth muscle, cardiac muscle, glands Agonists: ACh, muscarine Antagonist: atropine

Question 49

what are ionotropic receptors

Answer 49

Ionotropic (pentameric cations channel) Autonomic ganglia, motor endplate, CNS Agonists: ACh, nicotine Antagonist: curare (tubocurarine)

Question 50

what is the 2nd messenger system for nicotinic receptors

Answer 50

ion channel

Question 51

what is the 2nd messenger system for muscarinic M1 (neural)

Answer 51

Gaq

Question 52

what is the 2nd messenger system for Muscarinic m2 (cardiac)

Answer 52

Gai

Question 53

what is the 2nd messenger system for muscarinic M3 (glandular/ smooth muscle)

Answer 53

Gaq

Question 54

what do muscarinic receptors do in the airway smooth muscle

Answer 54

bronchoconstriction

Question 55

what do muscarinic receptors do in the gut smooth muscle

Answer 55

constraction

Question 56

what do muscarinic receptors do in salivary glands

Answer 56

increased salivation

Question 57

what do muscarinic receptors do in the bladder smooth muscle

Answer 57

contraction

Question 58

what are features of preganglionic neurones

Answer 58

Cell bodies in the grey matter of the brain stem OR in the lateral horn of spinal cord grey matter Long, synapse with postganglionic neurons at or near organ Release ACh to activate nicotinic receptors on postganglionic neurons

Question 59

what are features of post-ganglionic neurones

Answer 59

Cell bodies are in indistinct ganglia near or on their final target organ (further away from the spinal cord) Short, synapse on the target organ Release ACh to activate muscarinic receptors on the target organ

Question 60

what are the effects of the sympathetic nervous system on sweat glands mediated by

Answer 60

muscarinic receptors because in this special case the postganglionic neurones are also cholinergic

Question 61

what are drugs effect on the autonomic nervous system

Answer 61

Drugs enhance or mimic the autonomic nervous system or block the effects of theneurotransmitters at their receptor sites