PSYBIO Exam 3 ch.6+8+9

Substance use disorder (SUD)

A pattern of drug use in which people rely on a drug chronically and
excessively, allowing it to occupy a central place in their life; diagnostic term
encompassing four categories (DSM-5)

Withdrawal Symptom

Physical and psychological behaviors that occur when drug use ends

Environmental factors called ___________ are associated with an increased
risk of drug initiation and addiction

adverse childhood experiences (ACEs)

-these can include things like emotional, physical, and sexual abuse or neglect

-women are more likely then men to abuse

All psychoactive drugs, regardless of the primary neurotransmitter they affect, result in the release of

dopamine in the mesolimbic pathway

is released into the nucleus accumbens

Dopamine

Where does dopamine travel from and to?

Ventral Tegmental Area (VTA): Located in the midbrain/brainstem, it contains dopamine-producing neurons that send dopamine to the nucleus accumbens (part of the brain's reward system)

What is the striatum?

A group of brain structures located underneath the cerebral cortex.

Dorsal Striatum

dorsal aspects of the caudate nucleus, putamen, globus pallidus

-part of basal ganglia

Ventral Striatum

ventral aspects of the striatum, including the nucleus accumbens

-part of basal ganglia

Nucleus Accumbens

collectively, this part of the brain participates in motor coordination, reinforcement, and learning

Dopamine neurons are always active at low rates of firing called

tonic firing

Dopamine neurons fire quickly, when something unexpected happens (e.g. reward or something highly
aversive)

phasic firing

-causes an increase in dopamine that “overflows” into D1 receptors

Why are D2 receptors occupied at low dopamine concentrations?

Because they have a high affinity for dopamine, meaning they bind easily even when dopamine levels are low

How do drugs of abuse affect D1 and D2 receptors?

They cause large increases in dopamine, activating both receptors. D1 activation is especially important in addiction.

How do dopamine changes from drug use contribute to substance use disorders?

-Dopamine is released in many areas in the brain

• Striatum and cortex (D1): Strengthen reward.

• Amygdala, medial orbitofrontal cortex, and hippocampus (D1): Strengthen conditioning and drug-related memories.

Why do people develop a substance use disorder- Hedonia Hypothesis

-explanation of substance use disorder that is centered on the pleasure associated with natural experiences and produced by psychoactive drugs

-A pleasurable rush leads to a variety of impulse control disorders, such as repeated drug taking

-central problem: Over repeated drug exposure, the pleasurable or hedonic experience is dissociated from the drug-taking

Wanting and Liking theory (incentive sensitization)

• Wanting: Increases through sensitization of the mesolimbic dopamine system. This leads to stronger cravings and motivation to seek the drug.

• Liking: Can decrease as tolerance develops. The pleasurable effects of the drug may become weaker. Opioid neurons are involved in the brain's pleasure response.

-Repeated drug use increases wanting (cravings) but can decrease liking (pleasure), making a person crave a drug even when they enjoy it less.

Dark Side of Addiction theory

Stress and negative emotions drive addiction. People continue using drugs to relieve withdrawal symptoms and negative feelings.

• Stress: Negative emotions contribute to addiction.

• Brain systems: Stress and reward systems overlap.

• Negative reinforcement: Removing unpleasant feelings (such as withdrawal symptoms) increases the likelihood of continued drug use.

Binge/intoxication

increased incentive salience

-craving/wanting the drug

Withdrawal/negative affect

-decreased brain reward

-increased brain stress

-substances stress the body because it pulls the body away from homeostasis

Preoccupation/anticipation

-compromised executive function

How do brain systems contribute to wanting versus liking drugs?

• Frontal cortex: Helps make the decision to take a drug.

• Opioid system: Involved in pleasurable experiences (liking).

• Dopamine system: Drives wanting, cravings, and motivation to seek drugs.

• Striatum: Repeated drug use can turn voluntary drug-taking into automatic habits.

How do stress and reward systems overlap in the brain? (Dark Side theory)

CRH (corticotropin releasing hormone) and dynorphin (peptide) influence stress and reward circuits in the amygdala, prefrontal cortex, and VTA

-act as a neuropeptides in circuits within the brain (outside of the stress response)

-Stress chemicals affect brain areas involved in reward, motivation, and emotions

-no dopamine involved

Can drugs cause brain damage?

Yes, but damage can happen in different ways:

• Alcohol: Can contribute to thiamine (B1) deficiency→damage to thalamus and limbic system

• Cocaine: Can reduce blood flow to the brain.

• Marijuana: Contains 400+ chemicals.

-Drugs can harm the brain directly or indirectly

-many substances, even natural ones, can be neurotoxins

Stem cells

-are self-renewing multipotent cells that can become any cell type in the body

-early embryonic development is cell division→as division continues cell become more specialized

Neural Stem cell

-is self renewing multipotent cell that gives rise to neurons and glia

-when stem cells divides, it produces two stem cells, one dies and the other lives to divide again→this process repeats again and again throughout life

Progenitor cell

-precursor cell derived from a stem cell; it migrates and produces a neuron or glial cell

-produces nondividing cells known as neuroblasts and glioblasts

Neuroblast

product of a progenitor cell that gives rise to different types of neurons

Glioblast

product of a progenitor cell that gives rise to different types of glial cells

Stages of Brain development Steps 1-3

1-Cell birth

2-Neural (cell) migration

3-Neural (cell) differentiation

*prenatally→before birth

Stages of Brain development Steps 4-7

4-Neural (cell) maturation

5-Synaptogenesis

6-Cell death and synaptic pruning

7-myelogenesis

*postnatally→after birth

Step 1 Cell birth

-Neuroblasts and Glioblasts that are produced in the ventricular zone become neurons and glia

Neurogenesis: generation of neurons, some neurogenesis happens throughout life

Gliogenesis: generation of glia and continues throughout life

-cells are born

Step 2 Neural Migration

Radial glial cell: is a path-making cell that a migrating neuron follows to its appropriate destination

-neurons move from ventricular zone out

Step 3 Cell Differentiation

-neuroblasts become specific types of neurons

-cells get more specific

Step 4 Neuronal Maturation

Mature in two ways

Dendritic growth: grow dendrites to provide surface area for synapses with other cells

Axonal growth: extend axons to appropriate targets to initiate synapse formation

-develop dendrites, axon, and arborization/branching of dendritic spines

Clinical Focus Autism Spectrum

-hypothesized to relate to abnormal neuronal migration and maturation

-higher brain volume in the amygdala and gray matter

-genetic and epigenetic factors

-convergence of brain growth in females, but no convergence in males

Step 4 Neuronal Maturation→axonal growth

Growth cone: the growing tip of an axon

Filopod: process at the end of a developing axon that reaches out to search for a target or to sample the intercellular environment

Growth cones

-growing tip of an axon

-are responsive to cues from two types of molecules Cell adhesion molecule (CAM) and Tropic molecule

Cell adhesion molecule (CAM)

-provides surface to which growth cones can adhere

-serves to attract or repel growth cones

-Help cells stick or attach to other cells

-think of them as glue holding cells together

Tropic molecule

-is produced by targets being sought by the axons

-tells growth cones to “come over here”

-likely signals other growth cones seeking different targets to keep away

-Help developing neurons find their correct destination or target

-act as directions/road signs

Step 5 Synaptic Development

-synaptic genesis

-dendrites and axons meet and form synapses

Step 6 Cell death and Synaptic Pruning

-brain chisels away pieces through cell death and synaptic pruning

-cortex becomes measurably thinner in a caudal-rostral (back to front) gradient

-cells that didn’t make connections get killed off

Step 6 Neural Darwinism

-Hypothesis that cell death and synaptic pruning are, like natural selection in species, the outcome of competition among neurons for connections and metabolic resources in a neural environment

-use it or lose it

Step 6 Apoptosis

-genetically programmed cell death

Step 7 Progress of Myelination

-areas that perform simpler functions are myelinated earlier than those that perform more complex functions

-adding my