Nervous system

Question 1

Three main classes of neurons

Answer 1

1. Afferent/sensory
2. Interneurons (entirely in CNS)
3. Efferent neurons (somatic and autonomic)

Question 2

How can you divide efferent autonomic neurons into?

Answer 2

Sympathetic and parasympathetic

Question 3

What do somatic motor neurons control ?

Answer 3

Skeletal muscles

Question 4

What do sympathetic and parasympathetic neurons control?

Answer 4

Smooth muscles
Cardiac muscle
Glands

Question 5

What is the CNS made of?

Answer 5

Bran and spinal cord

Question 6

Name one neurotrophic factor produced by Schwann cells

Answer 6

Nerve growing factor (ngf); potential solution to Alzheimer

Question 7

What do Schwann cells do?

Answer 7

They form myelin sheaths in PNS and secrete neurotrophic factors

Question 8

What do satellite cells do?

Answer 8

Cover the cell bodies in ganglia(outside cans) and support cell bodies

Question 9

What do ependymal cells do?

Answer 9

They line the spaces in the brain called ventricles where you find cerebrospinal fluid

They are also a source of neural stem cells

Question 10

What are ganglia?

Answer 10

They are clusters of cell bodies outside the CNS

Question 11

What do oligodendrocytes do?

Answer 11

They produce myelin in CNS

Question 12

What do microglia do?

Answer 12

Macrophage-type cells that protect the nerve cells

Question 13

What do astrocytes do?

Answer 13

(in CNS)
Secrete neurotrophic factors.
Take up neurotransmitters, ions and water
Provide neutrons with substrates for ATP production

Question 14

How are Schwann cells and oligodendrocytes different in myelination process?

Answer 14

Hundreds of Schwann cells may myelinated one single axon whereas one oligodendrocyte myelinates portions of several axons

Question 15

What is the white matter?

Answer 15

Areas of CNS that contain a high number of myelinated axons

Question 16

What is the grey matter?

Answer 16

Areas of CNS that contain cell bodies and unmyelinated axons

Question 17

What does the membrane potential depend on?

Answer 17

1. Concentration of positively and negatively charged ions on each side of the membrane
2. Ion permeability of the membrane

Question 18

What 3 types of channel can there be ?

Answer 18

1. Voltage-gated : selective for particular ions
2. Chemically gated: operand close in response to binding of ligands like neurotransmitters.
3. Mechanically-gated: open and close in response to physical forces like vibration and stretch

Question 19

Where do graded potentials usually happen?

Answer 19

Cell body and dendrites

Question 20

Why do graded potentials lose strength ?

Answer 20

Because of current leaking across non-insulated membrane and because of resistance from cytoplasm

Question 21

Where do action potentials happen?

Answer 21

Axon hillock

Question 22

Can there be a summation of action potentials?

Answer 22

No, because of refractory period

Question 23

Can there be a summation of graded potentials?

Answer 23

Yes and two or more graded potentials coming together might produce an action potential if they are suprathreshold

Question 24

How does diameter relate to conduction?

Answer 24

Large diameter= faster conduction due to less resistance

Question 25

Stages of action potential

Answer 25

1. Resting membrane potential (-70mV) 2. Depolarizing stimulus 3. Membrane depolarises to threshold(-50). Voltage-gated Na+ channels open 4. Na+ entry depolarises cell 5. Na+ channels close. Voltage-gated K+ channels open 6. K+ leaves the cell. Membrane returns to resting potential 7. Membrane hyperpolarizes due to loss of k+ 8. K+ channels close 9. Membrane potential restored

Question 26

How is signal transmitted in electrical synapses?

Answer 26

Through gap junctions

Question 27

How are gap junctions formed?

Answer 27

By docking two hemichannels from two cells.

Question 28

What are the hemichannels composed of?

Answer 28

Connexin and innexin proteins

Question 29

Classes of neurotransmitters

Answer 29

1. CLASSICAL - Acetylcholine - Biogenic amines (noradrenaline, dopamine, histamine...) - Amino Acid (glutamate) 2. PEPTIDES - Substance P (sens. of pain) - Opioids (endorphins..) 3. UNCONVENTIAL TRANSMITTERS - Gases: Nitric oxide - Purine: ATP - Lipids: cannabinoids/anandamide

Question 30

How does an excitatory transmitter act on postsynaptic neuron?

Answer 30

It depolarises the membrane and if it reaches threshold it will cause an. action potential

Question 31

How does an inhibitory transmitter act on postsynaptic neuron?

Answer 31

It hyperpolarizes the membrane making it difficult to fire an action potential as it is farther away from the threshold

Question 32

How many steps for production of Acetylcholine?

Answer 32

Just one enzymatic step

Question 33

Where do substrates for Acetylcholine production come from?

Answer 33

Acetyl CoA comes from glucose metabolism | Choline comes from plasma

Question 34

What enzyme makes Acetylcholine and how?

Answer 34

Choline acetyltransferase catalyses transfer of acetyl group from AcetylCoA to choline.

Question 35

How is Acetylcholine degraded?

Answer 35

By enzyme acetylcholinesterase in ECS, which converts it into acetic acid and choline (recycled)

Question 36

What protein is involved in regulated exocytosis of neutrontramsitters?

Answer 36

Synaptotagmins bind to calcium ions and trigger the vesicle to use snare proteins and fuse with membrane

Question 37

What is an inotropic receptor?

Answer 37

A receptor that upon binding of neurotransmitter, opens an ion channel

Question 38

What is a metabotropic receptor?

Answer 38

A receptor that upon binding of neurotransmitter, changes the concentration of intracellular metabolites (e.g. cAMP) It does so via a G-protein linked effector molecule (e.g. adenylate cyclase)

Question 39

What is a metabotropic receptor coupled to ?

Answer 39

A G-protein effector molecule

Question 40

What is an agonist?

Answer 40

A substance that binds to and activates the receptor

Question 41

What is an antagonist

Answer 41

A substance that interferes with transmitter binding

Question 42

What kind of receptor is Nicotinic ACh receptor ?

Answer 42

Inotropic because the transmitter binding allows cations to enter the neuron

Question 43

What kind of receptor is Muscarinic ACh receptor?

Answer 43

Metabotropic

Question 44

What is the receptor for noradrenaline ?

Answer 44

Adrenergic receptor; metabotropic

Question 45

What do the different subtypes of adrenergic receptors do?

Answer 45

alpha1: activates phospholipase C1... alpha2: inhibits adenylate cyclase, decreasing cAMP beta1-3: activate adenylate cyclase, increasing cAMP

Question 46

How are transmitters removed?

Answer 46

- Enzymatic degradation in synaptic cleft | - Re-uptake into nerve terminal or glia followed by enzymatic metabolism

Question 47

Is there an uptake mechanism for ACh?

Answer 47

No, although choline is recycled

Question 48

Are biogenic amines uptaken?

Answer 48

Yes, in the nerve terminal

Question 49

Are amino acids taken up?

Answer 49

Yes, by nerve terminal and glia