Neurochemistry Flashcards

Question

Schwann cells

Answer 1

found in the PNS | Build myelin sheaths with with oligodendrocytes

Answer 2

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

Answer 3

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)

Answer 4

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

Answer 5

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

Answer 6

Sodium-Potassium pump, Na Channels, K Channels

Answer 7

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

Answer 8

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

Answer 9

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

Answer 10

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

Answer 11

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

Answer 12

1. At the start, Sodium is on the outside, Potassium on the inside 2. When depolarized, sodium and potassium channels open 1. At first, potassium channels produces little effect 2. Sodium ions rush into axon 3. Positive charge flows down the axon and opens voltage-gated sodium channels at the next point 4. At peak of the action potentials, sodium channels close but potassium channels are slower to change 5. Potassium flows out, allowing for the membrane to reach its original depolarization

Answer 13

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

Answer 14

Jumping of action potentials from node to node on myelin sheath

Answer 15

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

Answer 16

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

Answer 17

Happens immediatley after an action potential | Membrane cannot produce another action potential regardless of stimulation

Answer 18

Stronger than usual stimulus is necessary to initiate an action potential

Answer 19

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

Answer 20

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

Answer 21

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

Answer 22

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

Answer 23

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

Answer 24

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

Answer 25

Acetyl CoA (from metabolism) + Choline (metabolism or diet) → Acetylcholine Phenylalanine → Tyrosine → Dopa → Dopamine → Norepinephrine → Epinephrine Tryptophan → 5-hydroxytryptophan → Serotonin

Answer 26

``` 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

Answer 27

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

Answer 28

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

Answer 29

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

Answer 30

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

Answer 31

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

Answer 32

Presynaptic neuron takes up released neurotransmitter and reuses them using transporters

Answer 33

Faster than chemical synapses + synchronous | Gap junction: direct contact of membrane of 1 neuron with another

Answer 34

- Mimics activity of neurotransmitters, can block reuptake and prolong neurotransmitter in the synapse - L-Dopa: agonist used for Parkinson's

Answer 35

Blocks the activity of neurotransmitters

Answer 36

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

Answer 37

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

Answer 38

Therapy that includes rewards for remaining drug free

Answer 39

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

Answer 40

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

Answer 41

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

Answer 42

Stimulates acetyl choline receptors — nicotinic receptors | Increase dopamine release

Answer 43

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

Answer 44

In CNS | Make myelin sheaths with Schwann cells

Answer 45

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