Neurophysiology and Neurosecretion

Question 1

Describe the anatomy of the neuron?

Answer 1

Cell body from which high branched nerve processes called dendrites and a single axon extend

Question 2

What are dendrites covered by?

Answer 2

Dendritic spines

Question 3

What does dendritic spines do?

Answer 3

form connections or synapses with dendritic spines of other neurons

Question 4

Where does the Axon arise from?

Answer 4

Axon hillock

Question 5

Describe an axon?

Answer 5

At its end an axon will branch forming telodendria

Question 6

How is telodendria terminated?

Answer 6

By small swellings called presynaptic terminals or boutons

Question 7

What does Presynaptic terminals contain?

Answer 7

Small vesicles

Question 8

What does the Vesicles contain?

Answer 8

Chemical messengers or neurotransmitters

Question 9

Describe the Process of Axonal transport?

Answer 9

neurotransmitters are synthesised in the nerve cell body and transported down the axon

Question 10

What are the 3 major neuron types?

Answer 10

Multipolar, Unipolar and Bipolar

Question 11

What is the Resting Membrane Potential?

Answer 11

is when the Inside of a nerve cell has negative potential in relation to the positive electrical potential contained in extracellular fluid

Question 12

How is an Electrical gradient created?

Answer 12

Cells pump NA from interior to exterior fluid to swap NA for K, the high extracellular conc of NA and High intracellular conc of K causes this

Question 13

What happens when the cell reaches RMP?

Answer 13

Cell becomes polarised

Question 14

How does the Cell become polarised?

Answer 14

When K enters cell following electrical gradient but move out the cell along its own conc gradient and the forces are balanced

Question 15

How can RMP value be calculated?

Answer 15

Nernst equation, average -70 to -90mV

Question 16

What is the C0 and C1 (conc in and out of k) normally?

Answer 16

5mM and 140mM respectively

Question 17

How can NA channels open in localised changes of RMP?

Answer 17

Through voltage gated channels

Question 18

How can NA channels open in Neurotransmitter activation?

Answer 18

Ligand gated channels

Question 19

How does the Cell become depolarised?

Answer 19

During an Action potential when NA channels open and NA enters cells

Question 20

What are the small internal electric currents set up by the AP called?

Answer 20

Intrinsic/local currents

Question 21

How does Intrinsic currents conduct AP?

Answer 21

Open voltage gated NA channels initiate another AP

Question 22

What prevents the backflow of excitation?

Answer 22

The inactive/refractory period

Question 23

How is a Inactivation period created?

Answer 23

Once voltage gated NA channels has opened and closed it goes through period of inactivation

Question 24

How is conduction velocity enhanced?

Answer 24

Myelination of Axons

Question 25

How is the myelin sheath formed?

Answer 25

Cells called Schwann cells

Question 26

What does the myelin sheath do?

Answer 26

Wraps around axons to form 1mm sheath leaving short stretch of unmyelinated axon before next schwann cell

Question 27

How does Myelin sheath function?

Answer 27

Increasing the conductivity of the axon which increases conductivity of intrinsic currents increasing conduction velocity

Question 28

What do local anaesthetics target?

Answer 28

Voltage gated ion channels as have high affinity for NA ion channels in open state

Question 29

What increases the effect of the local anaesthetic?

Answer 29

Exhibit use dependant block which creates more channels to open, maintains in inactivated state

Question 30

What does maintenance in inactivated state mean?

Answer 30

Cell cant be re-stimulated

Question 31

What is a synapse?

Answer 31

Junction between a neuron and target cell

Question 32

Whar are the 2 types of Synapses?

Answer 32

Electrical and Chemical

Question 33

How does Electrical Synapses work?

Answer 33

Transmission via pores (gap j), allows rapid communication between neurons found in smooth and cardiac muscle

Question 34

What does the Chemical synape consist of?

Answer 34

Pre-synaptic membrane at pre-syn terminal of an axon and post-syn membrane

Question 35

What seperates the pre- and post-synaptic membranes?

Answer 35

Synaptic cleft

Question 36

How is a post-synaptic potential initiated?

Answer 36

AP in presyn activates release of neurotransmitter molecules into synaptic cleft that bind to specific receptors opening ligand gated channels

Question 37

What happens if the post-syn potential is large enough?

Answer 37

Elicit an AP in the target neuron

Question 38

What are 3 classical neurotransmitters?

Answer 38

AA, Monoamines, Purines

Question 39

Give me an example of AA neurotransmitters?

Answer 39

Glutamate, Gabba, Glycine

Question 40

Give me an example of Monoamine neurotransmitters?

Answer 40

ACh, Dopamin, NA, Adrenaline, Sertonin, Histamine

Question 41

Give me an example of a Purine Neurotransmitter?

Answer 41

Adenosine, ATP

Question 42

When fired where the does AP reach?

Answer 42

Synaptic bouton

Question 43

What enters and opens the boutons?

Answer 43

Calcium channels open to release calcium

Question 44

What protein is Calcium detected by?

Answer 44

Synaptotagmin

Question 45

What does Synaptotagmin do?

Answer 45

Promotes formation of SNARE complex between snare proteins

Question 46

What is the SNARE protein embedded in the vesicle membrane?

Answer 46

Protein Synaptobrevin

Question 47

What are the SNARE proteins associated with pre-syn membrane?

Answer 47

Protein Synatacin and SNAP-25

Question 48

How does a neurotransmitter release at an active zone?

Answer 48

Vesicle and pre-syn membranes fuse - then diffuse across synapse

Question 49

How does a neurotransmitter get back into the neuron?

Answer 49

It binds to the receptor and is broken down and recycled back

Question 50

Where do neuropeptides release?

Answer 50

From any location of the terminal membrane

Question 51

What do neuropeptides require to be released?

Answer 51

High concentrations of calcium to increase cell firing rate

Question 52

What is co-transmission?

Answer 52

More than 1 neuropeptide being released from single synapse

Question 53

What is the control of neurosecretion mediated by?

Answer 53

Autoreceptors and heteroreceptors

Question 54

What do Autoreceptors do?

Answer 54

Monitors self secretion

Question 55

What does hetroreceptors do?

Answer 55

Transmission from other synapses

Question 56

What do the receptors function as part of?

Answer 56

Localised negative feedback system

Question 57

What are sub-threshold potentials?

Answer 57

Inhibitory postsyn (ISPS) or Excitatory postsyn (ESPS)

Question 58

What are the 3 Mechanisms behind neurotransmitter inactivation?

Answer 58

Reuptake Enzymes Diffusion

Question 59

How does Reuptake mechanism work?

Answer 59

Ion gradients with high affinities

Question 60

How does Enzyme mechanism work?

Answer 60

AchE (acetate and choline) blocked by organophosphates

Question 61

How can Diffusion mechanism work?

Answer 61

Route for peptides as they are large so have prolonged effects