Psych Unit 7

Neuroscience & Behavior

• Everything psychological is also biological.

• Every mood, behavior, and thought comes from the brain and nervous system.

Neuroscience

• The study of the brain and nervous system.

• Began in the early 1800s with Franz Gall, who created phrenology.

Phrenology

• A false/pseudoscientific theory.

• Claimed bumps on the skull could predict mental traits.

Neuron

• A nerve cell.

• The basic building block of the nervous system.

Dendrites

• Branching extensions of a neuron.

• Receive information and carry it toward the cell body.

Dendritic Spines

• Small structures on dendrites.

• Help transmit signals and store synaptic strength.

Receptor Sites

• Areas on the cell membrane sensitive to neurotransmitters.

• Work like a lock and key.

• Each receptor fits only one neurotransmitter.

Neuron’s Three Basic Tasks

• Receive information

• Carry information

• Pass information to the next neuron, muscle, or gland

Cell Body (Soma)

• The neuron’s life support center.

• Contains the nucleus and keeps the cell alive.

Axon

• Long extension that sends electrical impulses away from the cell body.

• Sends messages to other neurons, muscles, or glands.

• Can be several feet long.

Axon Hillock

• Where the cell body becomes the axon.

• Decides whether the neuron will fire.

Myelin Sheath

• Fatty layer that insulates the axon.

• Speeds up neural impulses.

Multiple Sclerosis (MS)

• An autoimmune disease that damages the myelin sheath.

• Causes slowed communication to muscles.

• Symptoms include:

  • Vision loss

  • Pain

  • Fatigue

  • Poor coordination

  • Loss of muscle control

Nodes of Ranvier

• Gaps in the myelin sheath.

• Discovered in 1878 by Louis-Antoine Ranvier.

• Allow impulses to jump from node to node, speeding up communication.

Terminal Branches

• Small, tree-like ends of the axon.

• Send messages to neurons, muscles, or glands.

Terminal Buttons

• Bulb-shaped ends of terminal branches.

• Store and release neurotransmitters.

• Form junctions with other cells.

Neural Communication

• Neurons generate electricity from chemical changes.

All-or-None Principle (Law)

• A neuron either fires or it doesn’t.

• If it fires, it always fires at the same intensity.

• All action potentials have equal strength.

Action Potential

• A neural impulse.

• A brief electrical charge that travels down the axon.

Depolarization

• Occurs when positively charged ions enter the axon.

• This allows the electrical charge to move down the axon.

Repolarization

• After the impulse passes, the neuron becomes polarized again.

• Positively charged ions are pumped out.

Resting Potential

• The neuron’s resting state.

• The neuron is ready to fire an action potential.

Refractory Period

• The rest/recharge phase after a neuron fires.

• During the absolute refractory period, the neuron cannot fire again, no matter how strong the signal is.

• Once this period is over, the neuron can fire again.

Synapse

• A tiny, fluid-filled gap between:

  • The axon terminal of one neuron

  • The dendrite of the next neuron

• Electrical signals cannot jump this gap

Excitatory Effect

• Makes the receiving neuron more likely to fire.

• Increases the chance of an action potential.

Inhibitory Effect

• Makes the receiving neuron less likely to fire.

• Decreases the chance of an action potential

Neurotransmitters

• chemical messengers that travel across the synapse from one neuron to another.

• They influence whether the receiving neuron will generate an action potential.

Agonists

• Drugs that mimic or enhance the effects of neurotransmitters

• Example: Morphine mimics endorphins

Antagonists

• Drugs that block neurotransmitters

• Example: Botox blocks acetylcholine (ACh)

Dopamine

• Responsible for motor movement, learning, attention, alertness, emotions

• Important in addiction

• Too much → schizophrenia

• Too little → Parkinson’s disease

Serotonin

• Affects mood, hunger, sleep, arousal, pain

• Too little → depression

Norepinephrine

• Controls alertness and arousal

• Associated with eating

• Too little → depression

• Too much → schizophrenia

GABA (Gamma-aminobutyric Acid)

• Inhibitory neurotransmitter

• Controls muscle activity, eating & sleeping

• Too little → seizures, tremors, insomnia

Noradrenaline

• Helps control alertness and arousal

• Accelerates heart rate

• Affects eating, learning, and memory

• Too much or too little → mood disorders

Acetylcholine (ACh)

• Controls learning, memory, muscle contraction, motor movement

• Linked to Alzheimer’s disease

• Related to nicotine addiction

Endorphins

• Natural opiates

• Released during pain and vigorous exercise

• Reduce pain and create euphoria

• Linked to addictions and OCD

Glutamate

• Excitatory neurotransmitter

• Involved in memory

• Too much → overstimulation → migraines or seizures

Nervous System

• The electrochemical communication system of the body

• The body’s primary information system

• Two main parts:

  • Peripheral Nervous System (PNS)

  • Central Nervous System (CNS)

Peripheral Nervous System (PNS)

• Sensory and motor nerves connecting the brain and spinal cord to the rest of the body

• “Peripheral” = outer region

• Subdivided into:

  • Somatic Nervous System

  • Autonomic Nervous System

Somatic Nervous System

• Controls skeletal muscles

• Handles voluntary movement

• Contains motor nerves for voluntary muscles

Autonomic Nervous System

• Controls glands and internal organs

• Has two divisions:

  • Sympathetic

  • Parasympathetic

Sympathetic Division

• Arouses the body

• Prepares body for fight-or-flight

• Activated during stress or danger

Parasympathetic Division

• Calms the body

• Returns body to a relaxed state

• Opposes the sympathetic system

Central Nervous System (CNS)

• Made up of:

  • Brain

  • Spinal cord

• Brain: main site of information processing

• Spinal cord: main pathway to and from the brain