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330 Quiz 3


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What is a neurotransmitter and what are the three classes?
Chemicals released by a neuron to cause an excitatory or inhibitory effect.

Three classes: small- molecule transmitters, peptide transmitters, and transmitter gases.

Small- Molecule Transmitters
Quick acting neurotransmitter synthesized from dietary nutrients and packaged ready for use in axon terminals.
Peptide Transmitters
Neuropeptides act as hormones that respond to stress, allow a mother to bond to her infant, regulate eating and drinking and pleasure and pain.

Amino acid chains that are degraded by digestive processes, they generally cannot be taken orally as drugs as the small-molecule transmitters can.

Transmitter Gases
Water soluble gases that are synthesized in the cell as needed and afterwards each gas diffuses away, easily crossing the membrane and immediately becomes active.
What is a synapse and what does it do?
Where the messenger molecules are released from one neuron to excite the next neuron.

Do one of two things:
-Excite (type I)
-Inhibit (type II)

How are neurotransmitters made?
1. Genes (in the nucleus)
...then transported to axon terminal

2. Diet (in the axon)
Transporters pump in building blocks
Rate limiting enzymes

What are the steps to sending and receiving a neurotransmitter signal?
1. Action Potential
2. Neurotransmitters move to presynaptic membrane
3. Moves across synapse
4. Activation of the next cell

Where are excitatory and inhibitory synapses located?
Excitatory (type I) synapses are located on dendritic spines

Inhibitory (type II) synapses are located on the cell body

What is the receptor for direct effect?
Ionotropic Receptor

Allow the movement of ions across a membrane. Two parts:
1. Binding site
2. Pore

When the neurotransmitter attaches to the binding site the receptor changes shape, either opening the pore and allowing the flow of ions or closing it and blocking the flow. Rapid changed in membrane voltage, usually excitatory and trigger an action potential.

What are the two types of amino acids?
1. Glutamate: excitatory, depolarize

2. GAGA: inhibitory, hyperpolarize

What are the receptors for indirect effect?
Metabotropic Receptor

Has a binding site for a neurotransmitter but lacks its own pore through which ions can flow through a series of steps they indirectly produce changes in nearby ion channels or in the cell metabolic activity.

Generally inhibitory.

Metatropic Receptors and the g-protein, coupled to an ion channel and coupled to a second messenger system
G-Protein: activation results in binding to nearby proteins

Coupled to an ion channel= slower

Coupled to a second messenger system= even slower

How does the signal stop? (4)
1. Diffusion away from the synaptic cleft

2. Degradation by enzymes in the synaptic cleft

3. Reuptake into the presynaptic neuron

4. Taken up (glial cells)

What is a psychoactive drug?
Substance that acts to alter mood, though, or behavior and is used to manage neuropsychological illness.
What are the routes of administration into the nervous system?
Oral: Most common, absorbed in stomach or intestinal wall

Inhalation: Absorbed into cell lining of respiratory tract.

Injection: Intramuscular (im), intravenous (iv) and subcutaneous (sc)

Patch: Absorbed into skin

Blood Brain Barrier
Small, uncharged molecules are able to pass through the endothelial membrane and reach the brain. Certain other molecules are carried across the membrane by active transport. Large and electrically charged molecules are unable to pass out of the capillary.
Weakness in the blood brain barrier
Pineal gland: allows entry of chemicals that affect day-night cycles.

Pituitary: allows entry of chemicals that influence pituitary hormones.

Area Postrema: allows entry of toxic substances that induce vomiting.

How do drugs get eliminated?
Metabolized in kidneys, liver and intestines

Excreted in urine, feces, swear, breast milk and exhaled air

Some substances cannot be removed- build up = toxic

How many barriers does each entry have?
Brain: no barriers (quick, low doses)

Oral: most barriers, but safest easiest, but (larger doses and slower) weak acids (stomach-bloodstream) weak bases (intestines-bloodstream)

Muscle: more barriers

Inhalation: few barriers

Blood: fewest barriers but must be hydrophilic- water soluble

Patch: absorbed through skin into bloodstream

What are factors that influence drug response?
Age: older people are more sensitive because they have weaker barriers and reduced elimination due to lower metabolism

Body size: smaller individuals are more sensitive and have fewer body fluids to dilute drug

Sex: Females are more sensitive because they are smaller than men on average and have hormonal differences

What is an agonist?
A substance that enhances the function of a synapse
What is an antagonist?
A substance that blocks the function of a synapse.
What do amphetamines and cocaine do?
They block DA reuptake
What does ecstasy do?
Blocks serotonin reuptake
What is substance abuse?
Use for the psychological and behavioral effects, non- therapeutic
What is substance dependence?
Compulsive drug seeking, tolerance. Withdrawal both physical and emotional
What is binge drinking?
Drinking enough to elevate blood level to 0.08% or higher within a two hour period.
What is positive reinforcement?
To produce the chances that the positive feelings will happen again (beginning)
What is negative reinforcement?
Take a drug to counteract negative feelings (end)
What are the later stages of addiction?
Tolerance, withdrawal (anxiety, irritability, depressed, drug craving), neuroadaptive changes: neurotransmitter systems, brain damage
What are synaptic vesicles?
Contain the neurotransmitter

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