Biology of Behavior II

Overview

This study guide covers the biological foundations of behavior, focusing on the structure and function of the nervous system, the process of neurotransmission, and the major regions of the brain. Understanding these topics is essential for grasping how physiological processes underlie psychological phenomena.

The Nervous System

Central and Peripheral Nervous Systems

The nervous system is divided into two main parts: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).

• Central Nervous System (CNS): Consists of the brain and spinal cord. Responsible for processing and integrating information, and directing responses.

• Peripheral Nervous System (PNS): Composed of all nerves outside the CNS. Connects the CNS to limbs and organs, facilitating communication between the body and brain.

Example: When you touch a hot surface, sensory neurons in the PNS send a signal to the CNS, which processes the information and sends a response back through motor neurons.

Neurons and Neurotransmission

Structure of a Neuron

Neurons are the basic functional units of the nervous system. They transmit information via electrical and chemical signals.

• Dendrites: Receive incoming signals from other neurons.

• Cell Body (Soma): Contains the nucleus and integrates signals.

• Axon: Transmits electrical impulses away from the cell body.

• Axon Terminals: Release neurotransmitters to communicate with other neurons.

Action Potential and Neurotransmission

Neurons communicate through action potentials and the release of neurotransmitters.

• Depolarization: Sodium (Na+) channels open, Na+ floods into the neuron, making the inside more positive.

• Repolarization: Potassium (K+) channels open, K+ flows out, restoring the negative charge inside the neuron.

• Hyperpolarization: The neuron becomes even more negative than its resting state before returning to normal.

Key Equation:

Example: The action potential travels down the axon, triggering the release of neurotransmitters at the synapse, which then bind to receptors on the next neuron.

Major Brain Structures

Hindbrain

The hindbrain is responsible for basic life functions and coordination.

• Medulla: Controls breathing, blood circulation, and postural control.

• Pons: Involved in respiration, swallowing, bladder control, hearing, taste, eye movement, and facial expressions.

• Reticular Formation: Regulates arousal, sleep, and attention.

• Cerebellum: Coordinates balance, movement, and spatial reasoning.

Midbrain

The midbrain acts as a relay station for sensory and motor information.

• Superior and Inferior Colliculi: Transmit sensory information and assist in movement control.

• Substantia Nigra: Part of the dopamine pathway; degeneration is linked to Parkinson's disease.

Forebrain

The forebrain is involved in complex cognitive, sensory, and emotional functions.

• Cerebral Cortex: The outer layer, divided into two hemispheres and four lobes:

  • Occipital Lobe: Processes visual information.

  • Temporal Lobe: Involved in hearing and language processing.

  • Frontal Lobe: Responsible for personality, intelligence, voluntary movement, planning, and reasoning.

  • Parietal Lobe: Processes spatial location, attention, and motor control.

• Limbic System: Associated with emotions and drives. Includes:

  • Amygdala: Involved in fear, anxiety, and aggression.

  • Hippocampus: Essential for forming new memories.

  • Hypothalamus: Regulates internal states (temperature, hunger, thirst, sex) and directs motivated behaviors.

  • Pituitary Gland: Influences hormone release and stress response.

Brain Function Perspectives

Localization vs. Distributed Processing

Some brain regions have specialized functions, while others work together for complex tasks.

• Localization: Specific areas underlie specific functions (e.g., fusiform gyrus for face recognition, Broca's area for speech production, Wernicke's area for language comprehension).

• Distributed Processing: Multiple regions collaborate (e.g., memory formation involves the cerebellum, cerebral cortex, hippocampus, and medial temporal lobe).

Example: Damage to Broca's area causes non-fluent speech (Broca's aphasia), while damage to Wernicke's area results in fluent but meaningless speech (Wernicke's aphasia).

Neuroplasticity

Experience-Dependent Brain Changes

The brain can reorganize itself in response to experience, injury, or learning.

• Musicians may have enlarged somatosensory cortex areas related to finger movement.

• London taxi drivers show increased hippocampal size proportional to years of driving.

• Blind individuals may recruit visual cortex for touch processing.

• Children can recover function after hemisphere removal due to plasticity.

Studying the Brain

Methods of Investigation

Scientists use various techniques to study brain structure and function:

• EEG (Electroencephalogram): Measures electrical activity in the brain.

• ERP (Event-Related Potentials): Tracks brain responses to specific stimuli.

• fMRI (Functional Magnetic Resonance Imaging): Visualizes active brain regions during tasks.

Summary Table: Major Brain Structures and Functions

Additional info: Some details about neuroplasticity and brain imaging methods were expanded for academic completeness.