Chapter 4 Neurons

Question 1

The neuron at rest

Answer 1

• the membrane of dendrites are studded with receptor sites, which are specialized structures that will bond with neurotransmitters
• the interior of the neuron is about -70 mV compared to the outside. The charge is maintained by keeping a balance of ions between the inside and outside

Question 2

Receptor sites

Answer 2

• activated by neurotransmitters from nearby neurons
• when the neurotransmitter binds to the receptor, small channels in the membrane open, allowing ions to flow into or out of the cell
• after the depolarization or hyperpolarization, the neuron ejects the ions

Question 3

Depolarization

Answer 3

if a positive ion such as Na+ enters the cell, it will make the interior less negative; it depolarizes the cell, which excites it
- if the cell is significantly depolarized, an action potential is triggered and it travels down the axon

Question 4

Hyperpolarization

Answer 4

if a negative ion such as Cl- enters the cell, it will make the inside more negative; it hyperpolarizes the cell, which inhibits it

Question 5

Action potential

Answer 5

• causes the neuron to communicate with the next structure
• the AP travels down the axon
• when the AP reaches the bouton, the bouton will release its own neurotransmitters
• those neurotransmitters cross the synapse and bind to receptor sites on nearby neurons
• neurotransmitters are removed after release; they may be taken back up into the neurons that released them (reuptake); they may be broken down by enzymes (enzymatic breakdown); they may diffuse away gradually

Question 6

Agonists

Answer 6

drugs that stimulate receptors; they mimic the neurotransmitter

Question 7

Antagonists

Answer 7

drugs that block receptors so that neurotransmitters can’t bind to those receptors

Question 8

Reuptake inhibitors

Answer 8

drugs that prevent reuptake of neurotransmitters

Question 9

Enzyme inhibitors

Answer 9

drugs that prevent enzymatic breakdown of neurotransmitters

Question 10

Delayed effects when a drug is taken chronically

Answer 10

• if it is an agonist or a reuptake inhibitor, the neuron can respond to constant occupation of receptors by removing or desensitizing some receptors
• if it is an antagonist, the neuron may produce more receptors
• many receptors when occupied signal other events in the neuron; drugs can cause changes in these signals

Question 11

Monoamines

Answer 11

Dopamine: involved in motor activity and pleasure/craving. there are three major DA pathways arising from the midbrain- two from the ventral tegmental area and one from the substantia nigra
Norepinephrine: involved in arousal and attention. Most NE arises from the locus coeruleus in the brainstem
Serotonin: has multiple roles - mood, impulse control, eating, sleep. All serotonin arises from the raphe nuclei of the brainstem

Question 12

Acetylcholine

Answer 12

• most ACH in the CNS comes from one area: the nucleus basalis of Meynert. It projects all over the brain. in most systems it works in concert with dopamine
• deficits are linked to memory loss; damage to Alzheimer’s disease

Question 13

Glutamate

Answer 13

functioning is sensitized in alcohol withdrawal and is affected by PCP and ketamine

Question 14

GABA

Answer 14

functioning is altered by most sedatives, many anti-anxiety drugs and anti-seizure drugs

Question 15

Anandamide

Answer 15

• an inhibitory neurotransmitter that is released from the postsynaptic neuron and affects the presynaptic neuron
• THC is an anandamide
• found all over the brain but is not pronounced in the brainstem, which is probably why marijuana isn’t toxic in overdose