📚 COMPLETE EXAM SUMMARY

Three Cell Layers

• Ectoderm → Nervous system
• Mesoderm → Muscles, bones
• Endoderm → Internal organs

Neurulation Timeline

• Day 17: Neural plate forms
• Day 18: Neural groove appears
• Day 21: Neural tube closes
• Day 24: Three brain vesicles form

Three Brain Vesicles

Forebrain → Midbrain → Hindbrain (front to back)

Position determines destiny! (Cutting experiment proved this)

Cell Migration & Death

• Inside-out migration pattern
• 40× more cells made than needed
• NGF (Nerve Growth Factor) determines survival
• Radial glial cells guide migration

Three Migration Hypotheses

• Chemoaffinity: Chemicals attract specific axons (Sperry)
• Blueprint: Pioneer axons leave trail for others
• Topographic Gradient: Cells maintain relative positions

Critical Periods & Influences

• Hubel-Wiesel: Closed eye → that brain area shrinks
• Enriched environment → heavier brain, more dendrites
• Teratogens (thalidomide, alcohol) cause damage
• Adult neurogenesis IS possible! (hippocampus)

Neuron Types

• Unipolar: One process
• Bipolar: Two poles (eye, ear)
• Multipolar: Most common

Parts: Cell Soma (body) + Axon (output) + Dendrites (input)

Glial Cells

Brain Protection

• 3 Meninges: Dura (tough) → Arachnoid (web) → Pia (soft)
• CSF: 125ml, replaced every 3 hours
• 4 Ventricles: Lateral (1,2), 3rd, 4th

Electrical Communication

• Resting potential: -70mV (inside negative)
• Action potential: +50mV (Na+ rushes in)
• Digital = within neuron | Analog = between neurons
• Na-K Pump uses 40% of cell's energy!

Three Brain Divisions

Key Structures

• Thalamus: Relay station for ALL senses (except smell)
• Hypothalamus: Temperature, Hunger, Thirst, Sleep, Hormones
• Hippocampus: Memory formation
• Amygdala: Fear, aggression
• Cerebellum: Balance, coordination

Four Cortex Lobes

• Frontal: Motor, Broca's, planning, personality
• Parietal: Somatosensory (touch)
• Temporal: Hearing, Wernicke's, memory
• Occipital: Vision

Movement Disorders

• Parkinson's: Too little dopamine → Slow, rigid, tremor
• Huntington's: Basal ganglia degeneration → Jerky movements

Four Neurochemical Types

• Neuromodulators: Fine-tune activity
• Neuroregulators: 2nd messengers
• Neurohormones: From hypothalamus/pituitary
• Neurotransmitters: Direct message carriers

Synapse Parts

• 📤 Presynaptic: Releases NT (has vesicles)
• 〰️ Synaptic Cleft: Gap between neurons
• 📥 Postsynaptic: Receives NT (has receptors)

6 Steps of Transmission

1. Synthesis & Storage in vesicles
2. Release (Ca²⁺ triggers exocytosis)
3. Binding to receptor (lock & key)
4. Postsynaptic response (EPSP/IPSP)
5. Inactivation (reuptake or degradation)
6. Recycling of vesicles

Catecholamine Synthesis

Tyrosine → L-DOPA → Dopamine → Norepinephrine → Epinephrine

TH (Tyrosine Hydroxylase) = rate-limiting step

Major Neurotransmitters

Inactivating Enzymes

• AChE: Breaks down ACh (in cleft)
• MAO: Breaks down monoamines (inside neuron)
• COMT: Breaks down catecholamines (outside)

Receptor Types

• Ionotropic: Fast, direct channel opening
• Metabotropic: Slow, G-protein cascade

Drug Actions

• Agonist: Mimics NT
• Antagonist: Blocks NT
• Reuptake Inhibitor: Keeps NT longer (SSRIs)

Homeostasis

Body's system to maintain stable internal environment through feedback loops

• Feedback: Reports current status
• Feed-forward: Anticipates needs

Temperature Regulation

• Ectotherms: Depend on environment (reptiles)
• Endotherms: Internal control (mammals)
• Set Point: ~37°C in humans
• Control: Preoptic area of hypothalamus

Hunger Centers

• 🛑 VMH (Ventromedial): STOP eating (satiety)
• 🍴 LH (Lateral): START eating (hunger)
• VMH lesion = obesity | LH lesion = starvation

Two Types of Thirst

• Osmotic: From salty food → cells shrink → need water
• Hypovolemic: From blood loss → need water + salt

Circadian Rhythms

• ~24-hour biological cycles
• SCN (Suprachiasmatic Nucleus): Master clock
• Melatonin: "darkness hormone" from pineal

Sleep Types

Sleep Disorders

• Insomnia: Can't sleep
• Sleep Apnea: Breathing stops
• Narcolepsy: Sudden sleep attacks
• REM Behavior Disorder: Act out dreams

Reward System

• Pathway: VTA → Nucleus Accumbens → Prefrontal Cortex
• Uses DOPAMINE
• Olds & Milner: Rats pressed lever 7000x/hour for stimulation!
• All addictive drugs hijack this system

Hemispheric Specialization

Language Areas

• Broca's Area (Frontal): Speech PRODUCTION
• Wernicke's Area (Temporal): Speech COMPREHENSION
• Arcuate Fasciculus: Connects them

Types of Aphasia

Split-Brain Studies

• Cutting Corpus Callosum → Two separate "minds"
• Right hemisphere CAN understand, just can't SPEAK
• HE-ART experiment proved this

Memory Types

• Sensory: Milliseconds
• STM: Seconds-minutes (7±2 items)
• LTM: Permanent, unlimited
• Declarative: Facts you can state
• Procedural: Skills you can do

Memory Brain Areas

• Hippocampus: STM → LTM transfer (NOT storage!)
• Amygdala: Emotional memories
• Prefrontal: Working memory
• Cerebellum: Motor memories

Patient H.M. Case

• Both hippocampi removed for epilepsy
• Result: Couldn't form NEW declarative memories
• BUT could learn motor skills (mirror drawing)
• Proved different memory systems exist!

Types of Amnesia

• Anterograde: Can't form NEW memories
• Retrograde: Can't recall OLD memories
• Korsakoff's: Both types (from alcoholism)

Lashley's Principles

• Equipotentiality: All cortex parts contribute equally
• Mass Action: Memory loss depends on AMOUNT of damage

Other Disorders

• Apraxia: Can't do learned movements
• Agnosia: Can't recognize (visual, faces, sounds)
• Prosopagnosia: Can't recognize faces
• Dyslexia: Reading difficulty