Neuronal signaling (5)

Question 1

What is the major psychoactive ingredient in opium, and what are its effects?

Answer 1

Morphine – it is addictive but also an effective analgesic (painkiller).

Question 2

Where are opioid receptors concentrated in the brain?

Answer 2

In the periaqueductal gray (PAG) of the brain stem, with additional concentrations in the hypothalamus and other limbic areas.

Question 3

What effect does morphine have when microinjected into the PAG or when the PAG is electrically stimulated?

Answer 3

Produces strong analgesia (pain relief).

Question 4

Why were opioid receptors in the brain considered significant before the discovery of endogenous opioids?

Answer 4

Their presence suggested that the brain naturally produces opioid chemicals (endogenous opioids) that bind to these receptors.

Question 5

Name the two major families of endogenous opioids.

Answer 5

• Enkephalins (“in the head”)
• Endorphins (“endogenous morphine”)

Question 6

What type of neurotransmitters are endogenous opioids, and what type of receptors do they bind to?

Answer 6

They are neuropeptides and bind to metabotropic receptors.

Question 7

How did Parkinson’s disease contribute to the discovery of antipsychotic drugs?

Answer 7

Researchers noticed that drugs producing mild Parkinsonian symptoms also had antipsychotic effects, suggesting dopamine involvement in schizophrenia.

Question 8

What pattern of effects did the first antipsychotic drugs show?

Answer 8

They reduced psychosis after ~3 weeks of use and produced mild Parkinsonian symptoms.

Question 9

What discovery about dopamine helped explain how antipsychotic drugs work?

Answer 9

• Parkinson’s disease involves degeneration of dopamine pathways
• Dopamine agonists can produce schizophrenia-like symptoms
  → Excess dopamine activity might underlie schizophrenia, so dopamine antagonists can help.

Question 10

Do antipsychotic drugs cure schizophrenia?

Answer 10

No, but they improve the quality of life for many individuals by reducing symptoms.

Question 11

Describe the ionic basis of a neuron at rest. Include the ions and forces involved.

Answer 11

Resting potential: ~−70 mV

Ions: Na⁺, K⁺, Cl⁻, A⁻ (proteins)

Forces:

K⁺ tends to leave (concentration) but is pulled in by negative inside (electrical)

Na⁺ tends to enter (both concentration and electrical)

Na⁺/K⁺ pump maintains gradient (3 Na⁺ out, 2 K⁺ in)

Question 12

What are the properties of a postsynaptic potential (PSP)?

Answer 12

Graded (amplitude varies with stimulus)

Localized (occurs at synapse)

Types:

EPSP: depolarizes (Na⁺ influx)

IPSP: hyperpolarizes (K⁺ out / Cl⁻ in)

Short-lived, decays over time and distance

Question 13

Describe the two ways postsynaptic potentials are added together.

Answer 13

Temporal summation: Multiple PSPs from the same synapse in rapid succession add together

Spatial summation: PSPs from multiple synapses at the same time combine

Question 14

What are the three phases of an action potential and the ionic basis for each?

Answer 14

Depolarization: Threshold reached → Na⁺ channels open → Na⁺ rushes in → membrane positive

Repolarization: Na⁺ channels close, K⁺ channels open → K⁺ leaves → membrane returns negative

Hyperpolarization: K⁺ channels stay open → membrane more negative than rest → restored by K⁺ leak and Na⁺/K⁺ pump

Question 15

What is the maximum firing rate of an action potential and why?

Answer 15

~500–1000 Hz, limited by the absolute refractory period (Na⁺ channels inactivated, neuron cannot fire immediately)

Question 16

Where are neurotransmitters stored and how are they released?

Answer 16

Stored in vesicles at presynaptic terminal

Release (exocytosis): AP → Ca²⁺ enters → vesicles fuse → neurotransmitter released

Small molecules: pulse release

Neuropeptides: slow, depends on firing rate

Question 17

What is the function of gap junctions?

Answer 17

Connect cytoplasm of adjacent cells via connexin channels

Allow electrical signals & small molecules to pass

Facilitate rapid, synchronized communication

Question 18

What are the different amino acid neurotransmitters?

Answer 18

Glutamate (excitatory)

Aspartate (excitatory)

GABA (inhibitory, sometimes excitatory)

Glycine (inhibitory, spinal cord)

Question 19

What are the different monoamine neurotransmitters?

Answer 19

Catecholamines: Dopamine, Norepinephrine, Epinephrine

Indolamines: Serotonin (5-HT)