Neurophysiology and Synaptic Mechanisms

Question 1

What are the different types of neurons?

Answer 1

Projection neurons Local neurons

Question 2

What are the functions of Projection neurons?

Answer 2

Collect and collate input locally and from distant projection neurons Send output to distant areas of the brain

Question 3

Give examples of projection neurons

Answer 3

Pyramidal cells Stellate cells

Question 4

What are the functions of Local neurons?

Answer 4

Collect and collate input locally Send output locally to projection neurons or other local neurons

Question 5

Give an example of a local neuron

Answer 5

Interneurons

Question 6

What are the structural features of a neuron?

Answer 6

Nucleus Dendrites (Receives afferent signals) Schwann Cells (myelination) Soma (Processes information) Axon Terminal Bouton (forms the synapse)

Question 7

What are the structural features of the soma?

Answer 7

Cytosol Nucleus, nucleolus Endoplasmic reticulum (smooth, rough) Golgi apparatus Ribosomes Mitochondria Microtubules

Question 8

What is the function of the soma?

Answer 8

Summates input from dendrites to cause output to the axon

Question 9

What are the features of the dendtrites?

Answer 9

Multiple projections from the soma The information receivers Receive neurotransmitter input from other neurons (spines increase surface area for input) Express a huge variety of receptors; Ion channels - depolarising, hyperpolarising 2nd messenger systems, modulatory Membrane potential changes transmitted to soma

Question 10

What are the features of the axon?

Answer 10

Begins at axon hillock Single projection which may divide Carries output of the neuron in the form of action potentials Voltage gated Na+ channels Several types of K+ channel Microtubules carry vesicles to terminal Axoplasmic transport

Question 11

What are the features of the axon terminal?

Answer 11

Enlarged terminal of the axon Contains: Cytosol - Enzymes for neurotransmitter production Organelles - Mitochondria for ATP production - Neurotransmitter vesicles - Microtubules to hold vesicles

Question 12

What is resting membrane potential (Vr)?

Answer 12

Typically -65mV in a neuron (compared to ECF)

Question 13

What causes resting membrane potential?

Answer 13

Caused by relative permeabilities of ions

Question 14

What is the function of the Nernst Equation?

Answer 14

The Nernst Equation enables the determination of cell potential under non-standard conditions.

It calculates the Equilibrium Potential for an ion

•The Vm at which the ion will not flow

Question 15

What is the Nernst Equation?

Answer 15

E_ion = 61.5 log [ion]_o / [ion]_i

(at 37^oC, for monovalent cation)

Question 16

What is function of the Goldman Equation?

Answer 16

The Goldman equation is used in cell membrane physiology to determine the reversal potential across a cell’s membrane, taking into account all of the ions that are permeant through that membrane.

Combines Nernst equations to give Vm

Question 17

What is the Goldman equation?

Answer 17

Question 18

What does membrane potential (Vm) depend on?

Answer 18

Concentrations of ion inside and outside the cell

Relative permeabilities of the membrane to those ions