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PSYC270 > Neurochemistry > Flashcards

Neurochemistry Flashcards

1
Q

What did Roman y Cajal do?

A

Used the Golgi Technique that fills in some cells completely to allow to trace the entire shape of cells in our brain

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2
Q

What did Otto Loewi do?

A

Studied frog hears in vitro in 1920

Electrically stimulated 1 heart via the vagus nerve and noticed a decrease in heart rate

Transferred the liquid from first hear to the second and noticed a decrease in heart rate even through the second heart did not have stimulation

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3
Q

What is electrophysiology?

A

2 electrodes are placed

  • One inside the cell
  • Other is made of glass and placed into cell (intracellular)
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4
Q

What are voltage gated channels?

A

Transmembrane proteins

Amino acids twist depending on the charge of the membrane

Novocain binds and prevents Na channels opening, blocking APs

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5
Q

What do myelin sheaths do?

A

AP jumps to Nodes of Ranvier in 1mm intervals which contain Na channels
Prevents the loss of ions
Velocity of AP increases as the diameter of the sheath increases
Insulating fat material on axon found in vertebrates

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6
Q

Role of neurons

A

Receive information and transmit it to other cells

  • 86 billion neurons and 85 billion glia
  • 16 billion neurons in the cortex and 69 billion neurons in the cerebellum
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7
Q

Multipolar interneuron

A

Short/no axon

Integrate neural activity with one brain region and do not conduct information to other regions

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8
Q

Multipolar neuron

A

More than 2 processes

Most neurons are this type

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9
Q

Bipolar neuron

A

2 processes

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10
Q

Unipolar neuron

A

Contains 1 process extending from the cell body

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11
Q

What are the 4 major classes of neurons

A

Unipolar, Bipolar, multipolar, multipolar interneuron

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12
Q

How do neurons vary

A
  • Morphology (determines its connections/plasticity)
    • Function (releted to the shape)
    • Transcriptone (genes expressed by cell)
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13
Q

What are local neurons?

A

Small neurons without axons
Exchange information only with close neighbours
Do not follow the all-or-none law
Incoming information has a graded potential:
- Varies in magnitude in proportion to the intensity of stimulus
- Gradually decays as it travels

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14
Q

Define interneuron/intrinsic neuron

A

Cell’s dendrites and axon are entirely contained within a single structure

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15
Q

Define efferent axon

A

Brings information away from the structure

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16
Q

What is a motor neuron?

A

Has its soma in the spinal cord

Receives excitation through its dendrites and conducts impulses along its axon to a muscle

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17
Q

What is a presynaptic terminal?

A

At the end of an axon branch releasing chemicals into synapse

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18
Q

What is an axon?

A

Thin fiber constant in diameter, only 1 per neuron but has branches
Transmit signals to other neruons, organs, muscles
AP generated at the axon hillock, presynaptic terminals at the end

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19
Q

What is an axon?

A

Thin fiber constant in diameter, only 1 per neuron but has branches
Transmit signals to other neruons, organs, muscles
Action potential is generated at the axon hillock
Presynaptic terminals at the end of an axon release chemicals

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20
Q

What are dendritic spines?

A

Short outgrowths that increase the surface area of synapse and show plasticity (change often)
- Schizophrenia may change the number of dendritic spines in the prefrontal cortex

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21
Q

What are dendrites

A

Branching fibers that get narrower near the ends, lined with synaptic receptors responsible for bringing information into the neuron

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22
Q

What is a sensory neuron?

A

Specialized at one end to be highly sensitive to a particular stimulation

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23
Q

What are glia?

A

Non-neuronal cells in CNS
Outnumber neurons in cortex
Types:
Astrocytes, Microglia, Oligodendrocytes + Schwann cells, Radial Glia

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24
Q

Radial glia

A

Guide the migration of neurons during embryotic development

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25
Q

Schwann cells

A

found in the PNS

Build myelin sheaths with with oligodendrocytes

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26
Q

Microglia

A

Part of the immune system, remove viruses and fungi from the brain
Proliferate after brain damage to remove dead/damaged neurons
Contribute to learning by removing the weakest synapses

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27
Q

Describe the blood-brain barrier

A

Endothelial cells in brain are packed so tightly that viruses and bacteria are blocked
Also keeps out chemotherapy and some therapeutic drugs
Glucose, amino acids, some hormones and vitamins enter the brain via active transport
Barrier is leaky in some areas (ex. by the hypothalamus)

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28
Q

Nourishment of neurons

A

Need Vitamin B1 to use glucose, therefore deficiency (common in alcoholism) leads to the death of neurons known as Korsakoff’s syndrome

29
Q

Resting membrane potential

A

Membrane maintains electrical gradient (polarization) at rest
Electric potential is more negative on on the inside than the outside (-70 mV)
Resting potential is due to negative charged proteins inside the cell
Na 10x more concentrated on the outside
K 10x more concentrated on the inside
Na-K concentrations maintained by Sodium-Potassium Pump

30
Q

Forces acting on ions

A

Sodium-Potassium pump, Na Channels, K Channels

31
Q

Na channels

A

Closed at rest
With slight depolarization, channels open
Once threshold is reached, channels open wide and Na flows in
At AP peak, channels close and cannot be opened again for 1 ms

32
Q

K Channels

A

Few open at rest
Once threshold is reached, channels open but K leaves slowly
Channels stay open after AP is reached and more ions exit
The cell becomes hyperpolarized and then returns back to resting membrane potential due to Sodium-Potassium pump

33
Q

Membrane at rest

A

Sodium is pulled in due to electrical and concentration gradient
Potassium is pulled in due to electrical gradient, but pulled out due to concentration gradient
Chlorine ions mainly outside of the cell with concentration gradient equal at rest

34
Q

The action potential

A

Means by which messages are sent by axons, electrical signal traveling down an axon
Non-decremental
Speed depends on the size of the axon and myelination

35
Q

All or non law

A

Any depolarization that reaches the threshold will produce an action potential
All action potentials are equal in amplitude and velocity (varies in axons depending on axon width and myelination), and are independent of the stimulus

36
Q

Stages of AP

A
  1. At the start, Sodium is on the outside, Potassium on the inside
    1. When depolarized, sodium and potassium channels open
      1. At first, potassium channels produces little effect
      2. Sodium ions rush into axon
    2. Positive charge flows down the axon and opens voltage-gated sodium channels at the next point
    3. At peak of the action potentials, sodium channels close but potassium channels are slower to change
    4. Potassium flows out, allowing for the membrane to reach its original depolarization
37
Q

AP propogation

A

The positive charge of the sodium slightly depolarizes the adjacent area causing it to reach threshold and open its voltage-gated channels
Back propagation, Saltatory conduction

38
Q

Saltatory conduction

A

Jumping of action potentials from node to node on myelin sheath

39
Q

Back propagation

A

Cell bodies and dendrites passively register an electrical event at a nearby axon
The dendrite becomes more susceptible to structural changes responsible for learning

40
Q

The refractory period

A

Cell resists production of another action potential
- Absolute refactory period +Relative refactory period
Refactory period depends on:
- Sodium channels being closed
- Potassium flowing out of the membrane at a faster rate than usual

41
Q

Absolute refractory period

A

Happens immediatley after an action potential

Membrane cannot produce another action potential regardless of stimulation

42
Q

Relative refractory period

A

Stronger than usual stimulus is necessary to initiate an action potential

43
Q

Excitatory postsynaptic potential (EPSP)

A

Graded depolarization from flow of Na entering neuron
If it does not cause the cell to reach threshold, depolarization decays quickly
A quick sequence of EPSPs produces temporal summation

44
Q

Spacial summation

A

Synaptic inputs from separate locations combine their effects on a neuron
Critical to brain functioning

45
Q

Inhibitory postsynaptic potential (IPSP)

A

Temporary hyperpolarization of a membrane
Can regulate the timing of an activity
Synaptic input selectively opens gats for K to exit the cell or Cl to enter

46
Q

Spontaneous firing rate

A

Periodic production of action potentials even without synaptic input
EPSPs increase the frequency of action potentials above the spontaneous rate
IPSPs decrease the frequency of action potentials below the spontaneous rate

47
Q

Neurotransmitter categories

A

Amino acid: Glutamate, GABA, Aspartate, Glycine
Monoamines:
-Catecholamines: Dopamine, epinephrine, norepinephrine
Contain a catechol group + amine group
- Indolamines: Serotonin
Soluble gases: Nitric oxide
Modified A.A: Acetylcholine
Neuropeptides: NPY, AVP, OT
Synthesized in the cell body
Released by dendrites, cell bodies, and the side of the axon, diffuse widely
Release from dendrites primes other nearby dendrites to release the same neuropeptide
Release requires repeated stimulation, so they do not release often, but when they do, they release a lot

48
Q

Chemical events @ synapse

A
  1. Neuron synthesizes chemicals that serve as neurotransmitters.
    • Smaller neurotransmitters synthesized in the axon terminals and neuropeptides in the cell body
  2. Action potentials travel down the axon, enabling Ca to enter cell at presynaptic terminal. Ca releases neurotransmitters from the terminals into the synaptic cleft.
    • Ca entering the presynaptic terminal causes exocytosis; a burst of neurotransmitter release
  3. Released molecules diffuse across the cleft, attach to receptors and alter the activity of the postsynaptic neuron
  4. Neurotransmitter molecules separate from their receptors
  5. Neurotransmitter molecules are either taken back to the presynaptic terminal for recycling or diffuse away
  6. Some postsynaptic cells send reverse messages to control further release of neurotransmitters by presynaptic cells
49
Q

NT synthesis

A

Acetyl CoA (from metabolism) + Choline (metabolism or diet) → Acetylcholine

Phenylalanine → Tyrosine → Dopa → Dopamine → Norepinephrine → Epinephrine

Tryptophan → 5-hydroxytryptophan → Serotonin

50
Q

Ionotropic receptors

A 
When a neurotransmitter binds to an ionotropic receptor, it twists and opens its central channel to let specific ions pass
Immediately opens the channel in > 1ms, short lasting
Ligand gated (ligand: chemical that binds another molecule, typically a protein)

Non-NMDA: uses glutamate for Na to come in and K to go out

NMDA: uses glutamate and glycine for Ca to come in and K to go out

GABA, Glutamate, Acetylcholine

  • Glutamate is most used in the brain’s excitatory ionotropic synapses
  • Inhibitory ionotropic synapses use GABA
    • Opens Cl gates and crosses into the cell more rapidly
51
Q

Cholinergic pathway

A

Uses acetylcholine (generally excitatory), ionotropic

  • Acetylcholine receptor: outer portion is embedded in the membrane and inner portion surrounds Na channel
  • 2 acetylcholine molecules bind to the receptor at the alpha subunit and opens the channel
52
Q

Metabotropic receptor

A

Neurotransmitter initiates a sequence of metabolic reactions that start slow but last longer than ionotropic effects (several seconds) that uses much or all of the cell and many neurotransmitters

  1. Neurotransmitter binds to receptor to change its shape
    • The other side of the receptor is attached to a G protein (guanosine triphosphate - GTP)
    • Bending the receptor detaches the G protein
    • This increases the concentration of a second messenger inside the cell that communicates to areas within the cell to open or close channels
  2. Intracellular portion of the receptor affects other proteins (2nd messenger)
    - Dopamine, norepinephrine, serotonin, glutamate, GABA
53
Q

Dopaminergic receptors

A

Metabotropic

- Cyclic AMP is a common 2nd messenger — turns on a gene in the nucleus and can open or close ion channels

54
Q

Breakdown of NT

A

Acetylcholinesterase (AChe)
Breaks acetylcholine → Acetate + choline
Choline can go back into the neuron to form ACh again

    Monoamine oxidase (MAO)
        Contained in neurons releasing serotonin, dopamine, or norepinephrine
        Breaks down neurotransmitters into inactive chemicals, detaching from receptor and prevents the accumulation of harmful levels

COMT
Enzyme that breaks down any neurotransmitter not taken up by transporters

55
Q

Autoreceptors

A

Pre synaptic receptors detect the amount of neurotransmitter released and inhibit further synthesis and release
- Provides negative feedback

56
Q

Reuptake

A

Presynaptic neuron takes up released neurotransmitter and reuses them using transporters

57
Q

Electrical synapse

A

Faster than chemical synapses + synchronous

Gap junction: direct contact of membrane of 1 neuron with another

58
Q

Agonist

A
  • Mimics activity of neurotransmitters, can block reuptake and prolong neurotransmitter in the synapse
  • L-Dopa: agonist used for Parkinson’s
59
Q

Antagonist

A

Blocks the activity of neurotransmitters

60
Q

Mixed agonist-antagonist

A

Agonist for some effects and an antagonist for others or an agonist for some dosages and antagonist for others

61
Q

Drug affinity vs efficacy

A

Affinity: Tendency for a drug to bind to a receptor
Efficacy: Tendency for a drug to activate a receptor

62
Q

Contingency management

A

Therapy that includes rewards for remaining drug free

63
Q

Opiate abuse treatment

A

Methadone:
Activates the same brain receptors and has the sam effects as heroin and morphine
Taken orally and gradually breaks down to avoid the “rush” and minimizes withdrawal

Buprenophrine + Levemethadyl acetate (LAAM):
Similar to methadone
LAAM has long lasting effects

64
Q

Alcohol Abuse treatment

A

Antabuse:
Antagonizes the enzyme that metabolizes acetaldehyde
User becomes nauseated after drinking

Naloxone and naltrexone:
Blocks opiate receptors and therefore decreases the pleasure from alcohol

65
Q

Hallucinogenic drugs

A

Many resemble serotonin and stimulate at inappropriate times or for a longer time

66
Q

Nicotine

A

Stimulates acetyl choline receptors — nicotinic receptors

Increase dopamine release

67
Q

Stimulants

A

Inhibit transporters for dopamine, serotonin, and norepinephrine which decreases reuptake at prolongs effects
Leads COMT to break down dopamine faster than the presynaptic cell can replace it — user feels low hours after taking the stimulant

68
Q

Oligodendrocytes

A

In CNS

Make myelin sheaths with Schwann cells

69
Q

Na-K pump

A

3 Sodium out, 2 Potassium in
Uses active transport
Closed when the membrane is at rest

PSYC270 (6 decks)

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