Biology of Behavior I

Introduction

This section introduces foundational concepts in the biological basis of behavior, focusing on the nervous system, neurons, and research methods in psychology. Understanding these topics is essential for exploring how biological processes influence psychological phenomena.

Research Methods in Psychology

Internal vs. External Validity

Validity is crucial in psychological research to ensure that findings are accurate and generalizable.

• Internal Validity: Refers to the extent to which a study can demonstrate a causal relationship between variables. High internal validity means the study effectively tests if changes in the independent variable (IV) cause changes in the dependent variable (DV).

• External Validity: Refers to the generalizability of study results to other populations, settings, or times. High external validity means findings can be applied beyond the specific context of the study.

Example Table: Validity in Caffeine and Memory Studies

P-Values

P-values are a statistical measure used to determine the likelihood that an observed effect or correlation is due to chance.

• Definition: The p-value tells you the probability of observing a correlation (or mean difference) larger than the one you observed, assuming the null hypothesis is true.

• Threshold: A p-value of 0.05 is commonly used as a cutoff for statistical significance, though this value is arbitrary.

Correlation vs. Causation

It is important to distinguish between correlation (when two variables are related) and causation (when one variable causes changes in another).

• Correlation: Indicates a relationship between variables but does not imply one causes the other.

• Causation: Implies that changes in one variable directly result in changes in another.

Objectives in Biological Psychology

Key Learning Goals

• Describe key functions of the Central Nervous System (CNS) and Peripheral Nervous System (PNS).

• Identify parts of the neuron and explain neurotransmission.

• Articulate major brain structures and their functions.

Biopsychosocial Approach

Overview

The biopsychosocial approach emphasizes that psychological phenomena are influenced by biological, psychological, and social factors.

• Key Principle: Everything psychological is simultaneously biological.

Neurobiological Basis of Behavior

The Nervous System

Behavior is rooted in the nervous system, which enables complexity, integration, and adaptability.

• Complexity: The nervous system is highly intricate, with billions of neurons and connections.

• Integration: Different parts of the nervous system work together to process information.

• Adaptability: The nervous system can change and adapt in response to experience (neuroplasticity).

Central Nervous System (CNS)

The CNS consists of the brain and spinal cord, serving as the main center for processing information.

• Functions: Controls sensation, perception, thinking, language, and motor behavior.

Peripheral Nervous System (PNS)

The PNS connects the CNS to the rest of the body and is divided into two main subsystems:

• Somatic Nervous System: Controls voluntary movements and transmits sensory information.

• Autonomic Nervous System (ANS): Regulates involuntary functions such as heart rate and digestion.

  • Sympathetic System: Prepares the body for 'fight or flight' responses.

  • Parasympathetic System: Calms the body and conserves energy.

The Neuron

Structure and Function

Neurons are the basic units of the brain and nervous system, responsible for transmitting neural impulses.

• Dendrites: Receive messages from other cells.

• Axon: Passes messages away from the cell body to other neurons, muscles, or glands.

• Myelin Sheath: Covers the axon and helps speed neural impulses.

• Terminal Branches: Form junctions with other cells.

Types of Neurons

• Sensory Neurons: Convey information from the body to the CNS.

• Motor Neurons: Transmit information from the CNS to muscles and glands.

• Interneurons: Connect neurons within the CNS and are involved in processing information.

Neurotransmission

Electrical and Chemical Activity

Neurotransmission involves both electrical and chemical processes that allow neurons to communicate.

• Resting Potential: When a neuron is not sending a message, the inside is negatively charged relative to the outside.

• Action Potential: A stimulus causes the neuron to become more positively charged (depolarization), leading to the firing of an electrical impulse. All-or-None Law: If the membrane potential reaches the threshold, the neuron fires; otherwise, it does not. The size of the action potential is always the same. Equation: (resting potential)

Synaptic Transmission

When the action potential reaches the end of the neuron, neurotransmitters are released into the synaptic cleft to communicate with the next cell.

Neurotransmitters

Neurotransmitters are chemicals that transmit signals across the synapse.

• Excitatory Neurotransmitters: Facilitate firing by allowing positive ions in.

• Inhibitory Neurotransmitters: Prevent firing by allowing negative ions in.

• Examples:

  • Acetylcholine (ACh): Involved in muscle action, learning, and memory.

  • Dopamine: Associated with movement, attention, and emotion.

  • Serotonin: Regulates mood, hunger, and sleep; low levels linked to depression.

  • Norepinephrine: Influences alertness and arousal.

Neurotransmitter Reuptake

After neurotransmitters deliver their message, they are either broken down, reabsorbed (reuptake), or reused. Excessive reuptake can lead to low levels of neurotransmitters, affecting mood and behavior.

Summary Table: Nervous System Components

Additional info:

• Neuroplasticity refers to the brain's ability to reorganize itself by forming new neural connections throughout life.

• Multiple Sclerosis is a disease where the myelin sheath is damaged, leading to impaired neural transmission.