Neurotransmitter Types, Functions, and Neural Development in Psychology

3 Major Categories of Neurotransmitters

Amino acids, amines, peptides; grouped by structure, synthesis, and function

Amino Acid Neurotransmitters

Simple, synthesized from glucose, mostly in CNS

Glutamate

Main excitatory neurotransmitter in brain and spinal cord

GABA

Main inhibitory neurotransmitter in brain

Glycine

Inhibitory neurotransmitter in spinal cord

Amines (Monoamines)

Contain amine group, stored in vesicles, "classic neurotransmitters"

Acetylcholine (ACh)

Neurotransmitter for memory, learning, arousal, movement

Dopamine (DA)

Neurotransmitter for reward, motivation, attention, motor control

Serotonin (5-HT)

Neurotransmitter for mood, sleep, hunger

Norepinephrine (NE)

Neurotransmitter for attention, stress, mood

Epinephrine (E)

Neurotransmitter for fight-or-flight response

Peptide Neurotransmitters

Large molecules, slow, long-lasting effects

Cholinergic System

ACh system in basal forebrain & pons; memory, learning, movement

ACh Breakdown

Broken down by acetylcholinesterase

ACh Synthesis

Made in synapse via ChAT enzyme

Catecholamine Pathway

Tyrosine → L-DOPA → DA → NE → E

Dopaminergic Locations

Substantia nigra (movement), VTA (reward)

Dopamine Regulation

Autoreceptors + reuptake transporters

Noradrenergic Location

Locus coeruleus

NE Unique Feature

One neuron connects to ~250,000 synapses

Serotonergic Location

Raphe nuclei

Serotonin Removal

Mainly reuptake; SSRIs block it

Endocannabinoid System

Retrograde signaling (post → pre synaptic)

Endocannabinoid Functions

Hunger, memory, mood, stress, pain

Neurotransmitter Receptors

Determine excitatory/inhibitory effects

Key Receptor Concept

Same NT, different effect depending on receptor

ACh Receptors

Nicotinic and muscarinic

Embryonic Origin of NS

Ectoderm

Neural Tube

Becomes brain and spinal cord

Neural Tube Formation

Folding of neural plate

Spina Bifida

Bottom of tube fails to close

Anencephaly

Top of tube fails to close

Neurogenesis

Creation of neurons in ventricular layer

Migration

Neurons move using radial glia scaffolding

Migration Pattern

Organized, not random

Cell Differentiation

Neurons specialize via genetic signals and induction

Synaptogenesis

Formation of connections between neurons

Chemotropism

Axons guided by chemical signals

Growth Cone

Axon tip that detects signals with filopodia

Guidepost Cells

Direct axons via chemical gradients

Cell Death (Apoptosis)

Neurons die without connections or signals

Apoptosis Rule

"No connection = death"

Synaptic Pruning

Weak synapses eliminated, strong remain

Pruning Function

Improves efficiency of neural circuits

Theory of Mind

Ability to understand others' thoughts/emotions

ASD Criterion A

Social communication deficits (ALL required)

Social Reciprocity Deficit

Difficulty with back-and-forth interaction

Nonverbal Deficit

Poor eye contact, gestures, facial expressions

Relationship Deficit

Difficulty forming/maintaining relationships

ASD Criterion B

Restricted/repetitive behaviors (need ≥2)

Repetitive Behaviors

Repetitive movements or speech

Rigidity

Strong routines/resistance to change

Intense Interests

Highly focused interests

Sensory Sensitivity

Over/under response to sensory input

ASD Additional Criteria

Early onset + functional impairment

Mirror Neurons

Fire when acting or observing actions

Mirror Neuron Function

Empathy and social understanding

Mirror Neurons in ASD

Dysfunction → social deficits

ASD Brain Size

Larger early in development

Hippocampus/Amygdala in ASD

Larger in childhood, dense neurons in adults

Cerebellum in ASD

Fewer/smaller Purkinje cells

Cortex in ASD

Thicker, poor layering, weak boundaries

GABA in ASD

↓ GAD → ↓ inhibition → affects pruning

Serotonin in ASD

Abnormal migration/differentiation → excess synapses

Migration Issues in ASD

Poor cortical layering

Synaptogenesis Issues in ASD

Too many/few connections

Pruning Issues in ASD

Excess synapses

Apoptosis in ASD

Abnormal timing of cell death