psyc 100-Chapter 3

Neuroscience

studies the connection between the brain and behavior

Types of Neurons: Sensory Neuron

bring information from the world into the body and to the brain

Types of Neurons: Interneurons

internal neurons that pass communication between sensory and motor neurons

Types of Neurons: Motor Neuron

carry messages away from central nervous system (brain and spinal cord) to muscles and glands

What are Neurons composed of?

Soma, Dendrites, Axon, Terminal buttons

Soma (cell body)

Contains DNA

dendrites

extensions from soma that receive info

axon

extends from cell body, carries electrical potential

terminal buttons

emits a chemical message that reaches adjacent neurons

Glial cells

supportive and protective for neurons (outnumber neurons in the brain)

Myelin cells

type of glial cell that wraps around the neuron axon to increase speed of action potential (common on longer neurons)

Myelination

The formation of a myelin around nerve fibers that increases the speed and efficiency of neural communication.

• Continues until about age 12.

• Children learn and react more slowly and differently than adults.

Action potential

Occurs when the membrane potential rapidly shifts in response to incoming signal from adjacent neuron

• Triggered when a signal causes the membrane potential to reach about -55 mV.

• Ion channels open, allowing sodium (Na⁺) to enter, making the inside positive.

• Resting potential is restored as other channels open and sodium is pumped back out.

Resting Membrane Potential

• The axon’s membrane carries an electrical charge at rest.

• The inside of the axon is more negative than the outside (≈ -70 mV)

Synapse

junction between an axon terminal and an adjacent nerve cell

Neurotransmitter

Molecules are released from the axon terminal into the synapse when the action potential arrives at the axon terminal region

Agonists

Drugs that mimic or enhance neurotransmitters

• Amphetamine - stimulates release of dopamine

• Nicotine - acts like acetylcholine (involved in thought, learning, and memory)

Antagonist

Drugs that block the action of neurotransmitters

• Anti-psychotic meds block dopamine receptors

• Botox – blocks the release of acetylcholine

Resting Membrane & Action Potential: Resting Potential

The neuron’s stable electrical state (≈ -70 mV).

Resting Membrane & Action Potential: Threshold Potential

The point at which an action potential begins (≈ -55 mV).

Resting Membrane & Action Potential: Depolarization

Rapid influx of positive charge, reaching about +30 mV.

Resting Membrane & Action Potential: Repolarization

The neuron returns toward resting potential

Resting Membrane & Action Potential: Hyperpolarization

A brief overshoot where the charge becomes more negative than resting level.

Synaptic Transmission

1. Action potential reaches end of axon
2. vesicles transport NTs to membrane and release them into the synapse
3. NT interact with the postsynaptic receptors
4. May cause action potential in the post synaptic neuron
5. NT deactivation starts (e.g. reuptake)

Excitatory Drugs

• Increase neural activity by stimulating neurotransmitter release or mimicking their effects.

• Examples: Caffeine, nicotine, amphetamines.

• Effect: Heightened alertness, energy, and mood; can lead to overstimulation.

Inhibitory Drugs

• Decrease neural activity by blocking neurotransmitter release or enhancing inhibitory signals.

• Examples: Alcohol, benzodiazepines, barbiturates.

• Effect: Relaxation, drowsiness, slower reactions.

Mixed (Excitatory & Inhibitory) Drugs

• Affect multiple neurotransmitter systems, producing both stimulating and calming effects.

• Examples: Cannabis (THC), MDMA (ecstasy), opioids.

• Effect: Can cause both euphoria and sedation depending on dose, setting, and individual response.

How do we study the human brain?

Brain Damage
Case Studies
Brain lesion studies (animals typically)
Disadvantage: no/limited control in studies
E.g., Phineas Gage

Activating the Brain
Chemical injection or electrode placement in brain (animals)
E.g., seizure reduction surgery in humans
Transcranial magnetic stimulation (TMS)

Brain Recordings
Electroencephalograph (EEG)
Various imaging techniques (PET, MRI)
Allows us to study human brain in real time

How do we view/ record the brain?

Structural brain imaging methods:
CT scan (Tumors, Stroke) , MRI (magnetic resonance imaging)

Functional brain imaging methods:
EEG, PET Scan, fMRI

Altering brain activity:
TMS (Transcranial magnetic stimulation)

Hindbrain: Reticular formation

Controls arousal and sleep

Hindbrains: Pons

Controls unconscious movement and some reflexes like sneezing

Hindbrain: Medulla

Controls heartbeat, breathing, blood pressure

Hindbrain: Cerebellum

“little brain” - Controls balance, coordination

Midbrain: Substatia nigra

Controls helps control movements

Midbrain: Superior collicus

Controls sensory relay center, coordinates responses, processes visual information

Midbrain: Inferior collicus

auditory sound relay center & coordinates responses to sound

Forebrain: Cerebral Cortex

Cerebral Cortex Lobes: The two hemispheres of the brain are divided into four lobes, each with distinct functions:

• Frontal: Decision-making, problem-solving, movement, speech, and personality. Fully develops around age 25.

• Parietal: Processes touch and spatial awareness.

• Temporal: Handles hearing, language, and memory.

• Occipital: Controls vision and visual recognition.

Forebrain: Thalamus

relay center for sensory information from body to the cortices

Forebrain: hypothalamus

regulates motivation and the pituitary gland

Forebrain: Pituary gland

regulates and monitors hormones

Forebrain: Amygdala

emotional processing and reactivity

Forebrain: Hippocampus

memory

Brain stem

Controls breathing, heart rate, blood pressure, and consciousness

• Midbrain: Upper part of the brain stem, involved in auditory and visual
  processing

• Pons: Middle part of the brain stem, controlling sleep and arousal

• Medulla oblongata: Lower part of the brain stem, controlling breathing, heart rate, blood pressure

Primary Motor Cortex

In the frontal lobe; controls voluntary movement.

• Moves the Opposite side of body

Somatosensory Cortex

In the parietal lobe; processes touch and body sensations.

• Feels for the Opposite side of body

What divides the brain into two hemispheres?

Corpus Callosum

Left Hemisphere

Specializes in language, logic, math, and analytical thinking

Right Hemisphere

Handles spatial awareness, creativity, music, and emotion

Which side of the body does each brain hemisphere control?

Each hemisphere controls the opposite side of the body 

• The left hemisphere controls the right side

• The right hemisphere controls the left side

Broca’s Area

In the frontal lobe; controls speech production. Damage → trouble speaking.

• Lower front of brain

Wernicke’s Area

In the temporal lobe; controls language comprehension. Damage → trouble understanding speech.

• Upper back of brain

Lateralization

the right side of brain controls left side of body and vice versa

Central Nervous System (CNS)

Brain and spinal cord

• Processes information and sends commands.

Peripheral Nervous System (PNS)

All nerves outside the CNS

• connects body to brain.

Peripheral Nervous System Divisions: Somatic

Controls voluntary movements and sensory input.

Peripheral Nervous System Divisions: Autonomic

Controls involuntary functions (organs, glands).

Subdivision’s

• Sympathetic: Activates “fight or flight” response.

• Parasympathetic: Promotes “rest and digest” functions.

The Endocrine System

• A network of glands that produce and release hormones into the bloodstream.

• Slower than the nervous system (effects last days or weeks).

• The hypothalamus regulates hormone release.

• Hormones influence metabolism, growth, sexual behavior, and stress response.

Natural Selection

the theory that certain traits get selected over generations in improve “fitness” of a species

Genes

Segments of chromosomes that contain instructions for influencing and creating
hereditary characteristics

• Genotype: actual genetic message

• Phenotype: traits observable characteristic

Epigenetics

The study of how environmental factors affect gene expression without changing DNA itself.

• Examples:
  ● Lifestyle differences (diet, stress, smoking) affect identical twins gene expression differently.
  ● Chemicals in cigarette smoke cause epigenetic changes in lung cells.
  ● Babies conceived during the famine had epigenetic changes that made them more prone to obesity, diabetes, and heart disease later in life.