biopsychology - drug action

How does DSM‑5 (2013) define mental disorder?

Clinically significant disturbance in cognition, emotion regulation, or behaviour due to dysfunction in psychological, biological, or developmental processes, causing distress or impairment

What does “disturbance in function” mean in DSM‑5?

Disruption in thinking, feeling, or behaving

What is the biological approach to mental disorder?

The medical model, which explains psychological disorders similarly to physical illnesses with biological causes

Who believed the brain was the centre of thought and emotion?

Hippocrates and Plato

What did Aristotle believe about thought and emotion?

He argued that the heart, not the brain, was responsible for thought and emotion

What is the anti‑psychiatry perspective?

A critique of the medical model, arguing mental illness is either a social construct or purely psychological without brain pathology

What is organic pathology? - how we know something is wrong from tissue pathology

Structural abnormalities in tissues or organs, such as enlarged ventricles in schizophrenia or temporal lobe atrophy in depression

What is functional pathology?

Physiological dysfunction detectable only with biochemical or pharmacological methods, e.g., underactive GABA in anxiety

What is the nature vs. nurture debate in biopsychology?

Biological determinism (nature) versus environmental determinism (nurture), with biopsychology supporting an interactionist view

What does the vulnerability‑stress model propose?

Biological vulnerability interacts with environmental stress to produce mental disorders

What is differential susceptibility?

Some individuals are more or less sensitive to environmental risks or supports, affecting outcomes

What does the hierarchical approach in biopsychology refer to?

Biological, psychological, and social levels interact to influence mental functioning

What was timeline for drugs relating to mental disorders

• 19th century - just sedating people

• 1952 - first antipsychotic -chlorpromazine

• 1953-57 - first antidepressants - iproniazid and imipramine

• 1960 - first anxiolytics - diazepam

  • These drugs had actually therapeutic benefits

What is psychopharmacology?

The study of how drugs affect the brain and behaviour; closely linked with neuroscience

What is the Golgi stain used for?

A chemical technique that stains individual neurons so they can be viewed microscopically

What was Cajal’s major contribution?

He proposed that neurons are discrete cells that communicate across gaps (synapses)

What is the role of glial cells?

To provide physical and chemical support for neurons

What is the resting potential of a neuron?

‑70 mV, where the inside of the neuron is more negative than the outside

What does it mean when a neuron is “polarised”?

It maintains an electrical difference across its membrane at rest

What are ion channels?

Proteins that allow charged ions to move across the neuron’s membrane

What forces drive ion movement across the membrane?

Concentration gradients (diffusion) and electrical forces (electrostatic pressure - positive and negative attract each other etc)

What does the sodium‑potassium pump do?

Uses ATP to pump 3 Na+ ions out and 2 K+ ions in, maintaining the resting potential

What is action potential arc?

1. Start at -70 = resting potential

2. When threshold is reached (-55mv)

   1. voltage dependent Na+ channels open causing influx of positive Na+ into the cell = Depolarisation

3. When cell reaches its peak, Na+ voltage channels turn off and cant turn on again

4. Inside cell is now + 40 charged so diffusion and electrostatic pressure pushes K+ ions out

5. Voltage dependent K+ channels are less sensitive than Na+ so they open later allowing for K+ to flow out

6. Refractory period = brief time where membrane potential is less than normal in RP, membrane is hypo polarised

What is the absolute refractory period?

A period where no new action potential can occur regardless of stimulus strength

What is the relative refractory period?

Time when a stronger-than-normal stimulus can trigger an action potential

What is a synapse?

The junction between neurons where chemical communication occurs

What triggers neurotransmitter release?

• Arrival of an action potential that opens voltage‑gated calcium channels

• Influx of Ca2+ ions cause vesicle to migrate to synaptic membrane

• Vesicles fuse with the membrane, rupture and release the neurotransmitters into the synapse

• diffuse across the synapse and bind to postsynaptic receptors

What is a postsynaptic potential (PSP)?

An electrical change in the postsynaptic neuron caused by neurotransmitter binding

What is an EPSP?

Excitatory postsynaptic potential that increases firing likelihood via Na+ influx

• increase in positive ions casing more likely chance of depolarisation

What is an IPSP?

Inhibitory postsynaptic potential that decreases firing likelihood via Cl− influx or K+ efflux

How is neurotransmitter release inhibited?

Through negative feedback via presynaptic autoreceptors on nerve terminal → once enough has binded it tells it to stop being released

What is enzymatic degradation?

Enzymes break neurotransmitters into inactive components

• active reuptake - Transporters return neurotransmitters to the presynaptic neuron

What is a neurotransmitter receptor?

A protein that selectively binds neurotransmitters and converts chemical signals to electrical responses

What is a ligand?

Any molecule, including drugs, that binds to a receptor

Why do neurotransmitters have different effects?

Each neurotransmitter has multiple receptor subtypes (e.g., dopamine D1–D5)

What is an ionotropic receptor?

A ligand‑gated ion channel that opens directly in response to neurotransmitter binding

What are the characteristics of ionotropic receptors?

Fast response and short‑term neural plasticity

What is a metabotropic receptor?

A G‑protein‑coupled receptor that indirectly influences ion channels

What are characteristics of metabotropic receptors?

Slow response and long‑term neural plasticity via G‑protein or second‑messenger pathways

What are the seven steps of neurotransmitter action?

Synthesis, transport, storage, release, autoreceptor interaction, postsynaptic binding, inactivation

How do psychoactive drugs work?

By increasing or decreasing chemical communication in the brain

Why do synapses not function in isolation?

Neural circuits integrate multiple synapses, pathways, and modulatory systems