Membrane potential

Question 1

What is membrane potential?

Answer 1

Difference in electrical charge between inside/outside of cell

Question 2

What is polarisation?

Answer 2

One side +ve one side -ve (-70, at rest is resting potential = sodium in extra cellular/ potassium in intracellular)

Question 3

Ion channels?

Ions?

Answer 3

Special pores for passage of ions.

=ve /-ve charged particles (remove /add electron)

Question 4

What is an atom?

Answer 4

Nucleus with protons and neutrons

Question 5

What two processes change ion concentration?

Answer 5

Concentration gradient and electrostatic pressure (polarised cell membrane)

Question 6

What is the difference between depolarise and hyperpolarise?

Answer 6

Depolarise - reduce polarisation of membrane eg goes down 70..65..63
Hyperpolarise - increases polarisation of membrane (70, 73, 77)

Question 7

What does excitatory/ inhibitory postsynaptic potential do?

Answer 7

E- increases possibility of neuron firing as excites neurons, reaches threshold - action potential)
I - decreases PSP (takes away from threshold level)

Question 8

What 3 things happen in PSP?

Answer 8

1) Graded response (intensity determines amplitude)
2) Instantaneous
3) decremental (less amplitude as travels along axon)

Question 9

What is action potential?

Answer 9

The reversal of membrane potential from -70 mv to +30 - 50 mv, lasts 1 millisecond. Depends on EPSP being enough to male cell reach threshold.

Question 10

What is threshold of excitation?

Answer 10

When membrane depolarised enough to create action potential generation (all or nothing response UNLIKE PSP WHICH ARE GRADED

Question 11

What are two integration possibilities?

Answer 11

1) Spatial summation - simutaneous PSP sum to form greater PSP OR cancel eahc other out.
2) Temporal summation - PSP formed rapidly, as same synapse for greater potential (hyperpolarise as more accumulate, no time for resting potential)

Question 12

What are most common axons?

Answer 12

Somatic and dendritic

Question 13

What are directed and non directed synapses?

What is dendritic spine?

Answer 13

1) Release of neuro and site of neuro reception are close by
2) Opposite to 1
3) Nodules located on spine of dendrite.

Question 14

How do small Neurotransmitters travel?

Answer 14

To golgi complex, packed into vesicles, go and cluster near presynaptic membrane , until exocytosis

Have effect on IONOTROPIC and METABO receptors. Involved in brief, effects on neuron. Released over directed synapse.

(Large (created on ribosomes) - golgi - microtubules - terminal buttons

Question 15

What are receptors and ligands ?

Answer 15

1) Proteins on surface of PS membrane

2) Molecule that binds to another molecule

Question 16

What is a large neurotransmitter?

Answer 16

Neuropeptide - short proteins (made up of amino acids) about 3 to 36 in length (short protein chains)
Released more diffusely, not directed synapse.
Bind to METAB receptors that release 2nd messengers. Effects longer lasting etc etc.

Question 17

What do Calcium gated channels do

Answer 17

When action potential, open up - allow influx of calcium ions, causes small molecule NT vesicle to fuse with membrane and release content into synaptic cleft. BUT LNT - General level of calcium ions in intracellular fluid, not single action potential, more general rate/series of AP.

Question 18

What influences a neuron to act?

Answer 18

NT bind to specific proteins on surface of synaptic membrane called receptors. Influence on neuron depends if has specific receptors that bind to specific NT.
Many Neurons bind to many N receptors.

Question 19

What are two types of receptors?

Answer 19

1) Ionotropic - causes ligan gated ion channel to open/ close, ions flow into neuron or our (depending on NT and receptor being activated.) Can cause PSP, whether E or I depend on channel. eg. sodium channel in to neuron- excitatory.
2) Metabotrophic - more common– Not GATE. Signal protein has G protein attached - when released can a) break of and cause synthesis of 2nd messenger , this can go into cell nucleus and cause changes in DNA
OR b) can open /close channel

Question 20

Compare metabotropic to Ionotropic receptors.

Answer 20

M = more common, have slower effects, last longer, and act over greater area (more diffuse) and more varied.

Question 21

How are NT moved from synaptic cleft?

Answer 21

1) Reuptake - transporter mechanism reabsorb NT back into presynaptic neuron/
2) Enzymatic degradation. NT broken down by enzymes.

Question 22

What are glial cells?

Answer 22

Non neurol cells in CNS and PNS
No axons or dendrites
Smaller but more numerous than neurons
Conduct signals

Question 23

What are gap junctions and what do they do?

Answer 23

Narrow spaces between adjacent cells, bridged by tubular protein channels filled with cytoplasm (connexins)
Allow small molecules and electrical signals to pass between cells.
Quicker message.

Question 24

Where is a NT created?

Answer 24

IN the cytoplasm of a neuron