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Human Physiology 2 > Nervous system > Flashcards

Nervous system Flashcards

1
Q

Three main classes of neurons

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

How can you divide efferent autonomic neurons into?

A

Sympathetic and parasympathetic

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3
Q

What do somatic motor neurons control ?

A

Skeletal muscles

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4
Q

What do sympathetic and parasympathetic neurons control?

A

Smooth muscles
Cardiac muscle
Glands

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5
Q

What is the CNS made of?

A

Bran and spinal cord

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6
Q

Name one neurotrophic factor produced by Schwann cells

A

Nerve growing factor (ngf); potential solution to Alzheimer

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7
Q

What do Schwann cells do?

A

They form myelin sheaths in PNS and secrete neurotrophic factors

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8
Q

What do satellite cells do?

A

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

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9
Q

What do ependymal cells do?

A

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

They are also a source of neural stem cells

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10
Q

What are ganglia?

A

They are clusters of cell bodies outside the CNS

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11
Q

What do oligodendrocytes do?

A

They produce myelin in CNS

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12
Q

What do microglia do?

A

Macrophage-type cells that protect the nerve cells

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13
Q

What do astrocytes do?

A

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

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14
Q

How are Schwann cells and oligodendrocytes different in myelination process?

A

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

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15
Q

What is the white matter?

A

Areas of CNS that contain a high number of myelinated axons

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16
Q

What is the grey matter?

A

Areas of CNS that contain cell bodies and unmyelinated axons

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17
Q

What does the membrane potential depend on?

A
  1. Concentration of positively and negatively charged ions on each side of the membrane
  2. Ion permeability of the membrane
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18
Q

What 3 types of channel can there be ?

A
  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
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19
Q

Where do graded potentials usually happen?

A

Cell body and dendrites

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20
Q

Why do graded potentials lose strength ?

A

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

21
Q

Where do action potentials happen?

A

Axon hillock

22
Q

Can there be a summation of action potentials?

A

No, because of refractory period

23
Q

Can there be a summation of graded potentials?

A

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

24
Q

How does diameter relate to conduction?

A

Large diameter= faster conduction due to less resistance

25
Q

Stages of action potential

A
  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
26
Q

How is signal transmitted in electrical synapses?

A

Through gap junctions

27
Q

How are gap junctions formed?

A

By docking two hemichannels from two cells.

28
Q

What are the hemichannels composed of?

A

Connexin and innexin proteins

29
Q

Classes of neurotransmitters

A
  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
30
Q

How does an excitatory transmitter act on postsynaptic neuron?

A

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

31
Q

How does an inhibitory transmitter act on postsynaptic neuron?

A

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

32
Q

How many steps for production of Acetylcholine?

A

Just one enzymatic step

33
Q

Where do substrates for Acetylcholine production come from?

A

Acetyl CoA comes from glucose metabolism

Choline comes from plasma

34
Q

What enzyme makes Acetylcholine and how?

A

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

35
Q

How is Acetylcholine degraded?

A

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

36
Q

What protein is involved in regulated exocytosis of neutrontramsitters?

A

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

37
Q

What is an inotropic receptor?

A

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

38
Q

What is a metabotropic receptor?

A

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)

39
Q

What is a metabotropic receptor coupled to ?

A

A G-protein effector molecule

40
Q

What is an agonist?

A

A substance that binds to and activates the receptor

41
Q

What is an antagonist

A

A substance that interferes with transmitter binding

42
Q

What kind of receptor is Nicotinic ACh receptor ?

A

Inotropic because the transmitter binding allows cations to enter the neuron

43
Q

What kind of receptor is Muscarinic ACh receptor?

A

Metabotropic

44
Q

What is the receptor for noradrenaline ?

A

Adrenergic receptor; metabotropic

45
Q

What do the different subtypes of adrenergic receptors do?

A

alpha1: activates phospholipase C1…
alpha2: inhibits adenylate cyclase, decreasing cAMP

beta1-3: activate adenylate cyclase, increasing cAMP

46
Q

How are transmitters removed?

A
  • Enzymatic degradation in synaptic cleft

- Re-uptake into nerve terminal or glia followed by enzymatic metabolism

47
Q

Is there an uptake mechanism for ACh?

A

No, although choline is recycled

48
Q

Are biogenic amines uptaken?

A

Yes, in the nerve terminal

49
Q

Are amino acids taken up?

A

Yes, by nerve terminal and glia

Human Physiology 2 (5 decks)

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