Biological Psychology and the Nervous System: Study Guide

Biological Psychology

Neurons: Structure and Function

Neurons are the fundamental units of the brain and nervous system, responsible for receiving sensory input, sending motor commands, and relaying electrical signals throughout the body.

• Parts of a Neuron: Dendrites (receive signals), cell body (soma; contains the nucleus), axon (transmits signals), and axon terminals (communicate with other neurons).

• Function: Neurons process and transmit information via electrical and chemical signals.

• Example: Sensory neurons carry information from sensory receptors to the brain; motor neurons send commands from the brain to muscles.

Electrical Responses of Neurons

Neurons communicate through electrical impulses known as action potentials, which are generated by changes in the neuron's membrane potential.

• Resting Potential: The difference in electric charge across the membrane of a resting neuron (typically around -70 mV).

• Action Potential: A rapid change in membrane potential that travels along the axon. Triggered when the threshold is reached.

• Key Mechanism: Movement of sodium (Na+) and potassium (K+) ions across the membrane.

• Equation: $V = IR$ (Ohm's Law, relating voltage, current, and resistance in neural membranes)

Neurotransmitters and Neural Communication

Neurons communicate with each other at synapses using chemical messengers called neurotransmitters.

• Synapse: The junction between two neurons where neurotransmitters are released.

• Process: Action potential reaches axon terminal → neurotransmitters released into synaptic cleft → bind to receptors on the next neuron.

• Examples: Dopamine (movement, reward), serotonin (mood), acetylcholine (muscle action).

Brain Plasticity: Development, Learning, and Injury

The brain is capable of changing its structure and function in response to experience, learning, and injury—a property known as neuroplasticity.

• Development: Synaptic connections are formed and pruned during childhood.

• Learning: Repeated activity strengthens synaptic connections ("cells that fire together, wire together").

• Injury: The brain can reorganize itself to compensate for lost functions.

Central Nervous System: Structure and Function

The central nervous system (CNS) consists of the brain and spinal cord, each with specialized roles in behavior and bodily control.

• Brain: Controls thought, memory, emotion, and voluntary movement.

• Spinal Cord: Transmits signals between the brain and the rest of the body; involved in reflexes.

• Example: The cerebellum coordinates movement; the frontal lobe is involved in decision-making.

Somatic and Autonomic Nervous Systems

The peripheral nervous system is divided into the somatic and autonomic systems, each with distinct roles in daily functioning.

• Somatic Nervous System: Controls voluntary movements of skeletal muscles.

• Autonomic Nervous System: Regulates involuntary functions (e.g., heart rate, digestion).

• Subdivisions of Autonomic System: Sympathetic ("fight or flight") and parasympathetic ("rest and digest").

• Example: Sympathetic activation increases heart rate during stress; parasympathetic slows it down during relaxation.

Hormones and Behavior

Hormones are chemical messengers released by endocrine glands that influence behavior, mood, and physiology.

• Examples: Adrenaline (increases alertness), cortisol (stress response), testosterone and estrogen (sexual development and behavior).

• Effect: Hormones can affect aggression, mood, and cognitive abilities.

Brain Imaging and Stimulation Techniques

Modern neuroscience uses various techniques to study brain structure and function.

• Brain-Stimulating Techniques: Transcranial magnetic stimulation (TMS), deep brain stimulation (DBS).

• Imaging Techniques: MRI (magnetic resonance imaging), fMRI (functional MRI), PET (positron emission tomography), EEG (electroencephalography).

• Purpose: To observe brain activity, map functions, and diagnose disorders.

Localization of Brain Function

Different brain regions are specialized for particular functions, a concept known as localization of function.

• Examples: Broca's area (speech production), Wernicke's area (language comprehension), occipital lobe (vision).

• Evidence: Brain imaging and studies of brain injury support localization.

Genes, Heritability, and Psychological Traits

Genes influence psychological traits, but their effects are shaped by environmental factors. Heritability estimates the proportion of variation in a trait due to genetic differences.

• Heritability: Expressed as a percentage (0-100%), indicating the genetic contribution to individual differences in a population.

• Misconceptions: Heritability does not apply to individuals, nor does it mean a trait is unchangeable.

• Example: Intelligence and personality traits show moderate heritability, but environment also plays a significant role.

Summary Table: Nervous System Divisions

Division	Main Function	Example
Central Nervous System (CNS)	Processes information, controls behavior	Brain, spinal cord
Peripheral Nervous System (PNS)	Connects CNS to limbs and organs	Nerves in arms and legs
Somatic Nervous System	Voluntary muscle control	Moving your hand
Autonomic Nervous System	Involuntary functions	Heartbeat, digestion
Sympathetic	Prepares body for action	Increased heart rate
Parasympathetic	Calms body, conserves energy	Slowed breathing