7. Addicted Brain

CNS:

• brain and spinal cord

• integration and control center

PNS:

• all nerves outside the CNS

• Communication btw CNS and body

1. Autonomic NS (cardiac muscles, visceral muscles)

   1. sympathetic (active)

   2. parasympathetic (conserves energy)

   -> different Neurotransmitter

2. Somatic NS (skeletal muscles)

• myelencephalon

• metencephalon

• medulla oblongata

• contains ascending and descending sensory and motor tracts connecting the cereberum to the spinal cord

• contains nuclei that regulate breathing, blood pressure, vomiting

The process where nerve fibers cross from one side of the CNS to the other.

Key Example:

• Pyramidal decussation in the medulla oblongata — motor signals from the brain cross to the opposite side of the body.

Why it matters:

• Left brain controls right body

• Right brain controls left body

Occurs in:

• Medulla oblongata

• Spinal cord

• Brainstem

1. pons

   • contains pneumotacix centre which fine tunes breathing rate

   • relays info between cerebellum & cerebrum

2. cerebellum

   • feedback center for execution of motor movements

   • controls posture and balance

3. reticular fromation ( ARAS)

   • nuclei diffusely located through the brainstem

   • regulates wakefulness & muscle tone, pain, sleep-wake circle

Ascending Reticular Activating System

• network of neurons in the reticular formation of brainstem that prokects to the cerebral cortex

main role: maintain alertness, wakefulness

1. tectum (dorsal)

   • superior colliculi (nuclei for visual reflexes)

   • inferior colliculi (nuclei for auditory reflexes)

2. tegmentum (ventral)

   • substantia nigra (release dopamine to basal ganglia)

   • ventral tegmental area VTA (connections with N. accumbens)

Reward System

Telencephalon + Diencephalon

thalamus:

• main integrating centre of sensory info

• receives input from basal ganglia & cerebellum

• ADHS

hypthalamus:

• main control centre for autonomic NS (vegetative NS)

• control of hormones/ important in endocrine system

• contains nuclei important in reg. of circadian clock, hunger, thirst

• Amygdala

  • associated with pleasure, fear, addiction

• Hippocampus

  • importan in formation of memories inc spatial &navigation

-> both part of the limbic system

NO

attention, arousal, stress

motivation, curiosity, reward excepectation

sedation, mood & social behavior, appetite and digestion, sleep, memory and sexual desire & function

focused attention, promoting language

excitatory, inhibitory

• anatomically

• chemically

research about the relationship between neutotransmitter & behaviour

• glutamate

• involved in fast neurotransmission & signaling

• release Cs2+ dependetn

  • alzheimer's, epilepsy (distrubed regulation)

  • schiziophrenia (to less)

  • cell death, parkison (to much)

NMDA (slower, glutamat already there)

• important for memroy

AMPA

• fast and short term signal transmission

• GABA A = Ionotropic (fast, short-term)

  • keeps neurons from firing

  • drugs: benzodiazepines, steroids

• GABA B = Metabotropic (slow, long-lasting)

  • reduces neurotransmitter release

  • drugs: baclofen (muscle relaxant)

• Pathophysology:

  • anxiety

  • depression

  • memory

Neurotransmitter: Acetylcholine

• motor control

-> functions very differently in cardiac muscles

• stops contraction of muscles in the cardiac region

Pathophysiology:

• Alzheimer

• Parkinson (too high)

• Huntington ( too low)

1. Nicotinic ACh receptors

   • postsynaptic membrane of all autonomic ganglia

   • fast

   • depolarization -> excitation

   • agonist: nicotin

2. Muscarinic ACh receptors

   • pruduces parasympathetic nerve effects in the heart

   • slow

   • hyperpolarization -> inhibition & depolarization -> excitation

   • agonist: muscimol

• frontal cortex: cognition and memory

• hippocampus: memory

• other limibic areas: mood

brainstem (raphe nuclei)

• anxiety

• depression

• schizophrenia

• PNS: vomiting, peristalsis

• CNS: control of apetite

• Gi/G0-protein coupled

• Gq-protein coupled

• pleasure, reward and goal directed behavior

• motivational & emotional responses

• coordination of movement

• regulates secretion pf prolactin

• vomiting

Pthophysiology:

• hyperkinesis (too high)

• schizo

• depression

• D1

  • D1 & D5

  • excitatory (high cAMP)

• D2

  • D2, D3, D5

  • inhibitatory (low cAMP)

norepinephrine

• PNS: body temperature, increasing blood flow

• CNS: attention and consciousness

epinephrine

• excitatory effect along autonomic pathway

• depression

• stress

• alzheimer

• alpha 1: vascular

• beta 1: heart

• alpha 2: vascular

• beta 2: eyes

• modulation of wakefulness, motor activity, food intake, sexual behaviour

• food, water, sex

• allow organism to feel pleasure

• reinfoce the behaviour of repetition

• required for survival

any event that increases the probability of a response with a positive hedonic component

actions that produce a rewarding effect in a particular context become more likely to occur again in that context

VTA(dopamine production area) -> NAc (motication and goal directed behavior) & VTA -> PFC

(liking -> wanting -> craving)

stimulation of the dopaminergic reward system

• tune attributes of rewarding stimuli by encoding the value of reward

• enhacning associative learning of the reward system

• rewards activate neurons

• expectation of rewards activates the neurons

• unexpected rewards activate the neurons even more

Dopamine neurons actually stop responding to the primary reinforcer and instead begin to respond to the conditioned stimulus

• stimulus that causes response to be maintained and increased

• pos: increases behavioral response to get a positive reward

• neg: increases behavioral response to end the anhedonic situation

It’s how addictive drugs override the brain’s reward system, releasing large amounts of dopamine and reinforcing drug use.This rewires the brain to crave the drug, reducing response to natural rewards and leading to compulsive use and addiction.

• VTA dopamine neurons are controlling reward

• Drugs directly and powerful activate theres neurons with no connection to purposeful behavior

• this leads to a profound corruption of the brains meachnisms: drugs gradually, progressively, and insidiously replace neatural rewards as the major shaper of behavior

same that are activated by natural rewards

Nucleus accumbus

food : 50-100

cocaine 400

• chronically relapsing disorder

• compulsion to seek and take the drug, loss of control

• negative emotional state (when access prevented)

• social harm

• dependence

• physical harm

exposure = dose x time

• reduced responses to natural rewards

• sensitized resp. to drugs of abuse and associated cues

• impaired cortical control over more prim reward pathways

• drug-induced neural plasticity mediated via altered gene expression

• addiction produces a change in brain structure & function

• molecular and cellular changes in particular neurons alter functional neural circuits

• chronic drug use causes dopamine cells to shrink in animals, dramatically decreasing reward signals

• brain region in the midbrain that produces dopamine

• forming part of reward system

• Drugs of abuse stimulate the VTA, causing increased dopamine and reinforcing addictive behavior

• rewarding

• pos reinforcing

•