Ch 3 Chemical Signaling By Neurotrasmitters and Hormones

Question 1

Define synapse

Where can synapses occur?

Answer 1

Synapse = one-way communication between pre and post synaptic cells

Synpases occur on the post synaptic cell, on the:

Dentrite (axodendritic) - most common in the brain; axon terminal communicates with dendrite of post synaptic cell

Cell body ( Axosomatic) - between nerve terminal and a nerve cell body

Axon (Axoaxonic)

Question 2

What are the categories of neurotransmitters?

What is the exception?

Answer 2

Amino Acid Transmitters

Monoamine transmitters

Lipid transmitters

Neuropeptide transmitters

Gaseous transmitters

EXCEPTION: Acetylcholine

Question 3

How many neurotransmitters do neurons typically synthesize?

Answer 3

2, usually from different categories

Question 4

What is exocytosis?

Answer 4

A Ca 2+ - dependent process where by neurotransmitters are released from nerve terminals; vesicle fuses to axon terminal, exposing tths inside of the vesicle to the outside of the cell

Question 5

What factors affects the rate of neurotrasnsmitter release?

Answer 5

1. Rate of cell firing
2. Release probability at specific synapse
3. Inhibitory terminal and somatodendritic autoreceptors(Thermostats)

Question 6

How does termination of transmitter action occur?

Answer 6

Dependent on neurotransmitter

BY:
A)Process of uptake (e.g. reuptake by the presynapitc cell)

b)Enzymatic breakdown

Question 7

What is a synaptic vesicle?

Answer 7

Small sacklike object present in the synaptice cleft, which is filled with thousands of molecules of neurotrasmitters

Usually the sources of transmitter release

Question 8

What are classical neurotransmitters?

Answer 8

Amino Acids

• building blocks of proteins
• serve metabolic functions

Monoamines

• derrived from animo acids
• includes dopamine, norepinephrine, seretonin

Acetocholine

Question 9

What are nonclassical neurotransmitters?

Answer 9

Neuropeptides

• small proteins (3-40 anino acids)
• includes families of endorphines, enkephalines (implicated in opiod usage)

Lipids
- few

Gases
-nitrous oxide

Question 10

How and where are neurotransmitters manufactured?

Answer 10

All, (EXCEPT NEUROPEPTIDES) are synthesized by enzymaitc reactions that can occur anywhere in the cell

Most commonly from the axon terminals

Neuropeptides require protein precursor, therefore are generated in cell body and released at terminal. Replenishment of neuropeptides compared to other trasmitters is slower.

Question 11

Define Neuromodulator

Answer 11

substances that don’t act exactly like neurotransmitters, but may alter the action off a standard transmitter by prolonging, enhancing or reducing transmitter effectiveness

Question 12

What are the two categories of neuroreceptors?

Answer 12

Ionotropic

• composed of multiple subunits
• form an intrinsic ion channel that is permeable either to cations such as Na+ (and sometimes also Ca2+) or to anions such as Cl–.
• Na/Ca = mediate fast excitatory transmision
• Cl= mediates fast inhibitory transmission.

Metabotropic

• 1 subunit
• activates G proteins in the cell membrane
• mediate slower transmission involving ion channel opening (e.g., inhibitory K+ channels) or second-messenger synthesis or breakdown.

Question 13

How does a second messenger work?

Answer 13

by activating protein kinases that phosphorylate target proteins in the postsynaptic cell.

Question 14

How does psychoactive drugs act on synaptic transmission to create the drug effect?

Answer 14

1. Increase/decrease transmitter synthesis
2. reducing transmitter inactivation by inhibiting enzymatic breakdown or blocking reuptake
3. stimulating transmitter release
4. acting as agonists or antagonists at transmitter receptors on the postsynaptic or presynaptic

Question 15

What is synaptic plasiticity?

Answer 15

functional and structural changes in synaptic connectivity.

Plasticity can be produced by sensory and experiential stimuli, as well as psychoactive drugs.