Chapter 6: Biological Basis of Behavior

Learning Objectives

• Identify the main parts and functions of the nervous system.

• Familiarize with the main parts and functions of the endocrine system.

• Explain certain behaviors or reactions to situations as a product of neuroendocrine activity.

Neurobiological Psychology

• Humans are biological beings.

• Behavior is governed by both psychosocial factors and biological processes.

Nervous System

• Neurons: Basic structural units.

  • Cell Body (Soma): Contains nucleus; center of nourishment.

  • Axon: Conducts nerve impulses away from the cell body (sender).

  • Dendrite: Conducts neural impulses towards the cell body (receiver).

Neuron Functions

1. Sensory Neurons (Afferent Neurons)

   • Send impulses from the receptors to the brain.

2. Interneurons

   • Conduct neural impulses from sensory neurons to motor nerve cells.

3. Motor Neurons (Efferent Neurons)

   • Send impulses from the brain to motor nerve cells.

4. Glial Cells

   • Non-neural cells providing a supportive framework of the nervous system.

Neurotransmitters

• Synaptic Terminals: End points of neurons; contain neurotransmitters.

• Synaptic Gap: The gap between neurons.

• Synapses: Junctions where synaptic terminals meet.

• Neurotransmitters are chemical substances carrying messages across synapses, can either excite or inhibit neuron firing.

Key Neurotransmitters

• Acetylcholine (ACh)

  • Functions: Learning, memory, muscle contractions.

  • Deficiency: Disrupts learning and memory; linked to Alzheimer’s disease.

• Norepinephrine

  • Functions: Stress hormone; affects attention and responding actions.

  • Role: Fight-or-flight response; influences heart rate and energy release.

  • Imbalances: Too little leads to depression; too much may cause hyperactivity.

• Dopamine

  • Functions: Controls large muscle movements, pleasure perception.

  • Imbalances: Oversupply leads to schizophrenia, undersupply to Parkinson’s disease.

• Serotonin

  • Functions: Regulates mood, sleep, and appetite.

  • Imbalances: Lack can cause insomnia and eating disorders.

• Gamma-Aminobutyric Acid (GABA)

  • Functions: Decreases neuron activity, reduces anxiety; anti-anxiety medications increase its effects.

Nervous System Divisions

• Central Nervous System (CNS)

  • Processes and interprets info; issues orders to muscles and organs.

• Peripheral Nervous System (PNS)

  • Divided into:

    • Somatic Nervous System: Controls voluntary movements.

    • Autonomic Nervous System: Controls involuntary processes (e.g., digestion, circulation).

      • Sympathetic Nervous System: Mobilizes body for action (fight-or-flight).

      • Parasympathetic Nervous System: Conserves energy and maintains tranquility.

The Brain and Spinal Cord

• Brain: Central control center; protected by cranium.

  • Organizes sensory information and higher cognitive processes.

• Spinal Cord: Pathway for sensory information; reflex actions.

Brain Structures

• Hindbrain:

  • Medulla: Controls breathing, heart rate, and reflexes.

  • Pons: A bridge involved in sleep, attention, and arousal.

  • Cerebellum: Coordinates movement and balance.

• Midbrain: Relays information between sensory systems; regulates alertness.

• Forebrain: Highest level of brain; includes limbic system, thalamus, basal ganglia, hypothalamus, and cerebral cortex.

  • Limbic System: Involved in emotion and memory (e.g., amygdala, hippocampus).

  • Thalamus: Sensory relay station; regulates sleep and wakefulness.

  • Hypothalamus: Regulates hunger, thirst, and emotional responses.

  • Cerebral Cortex: Involved in complex functions (thinking, planning).

    • Subdivided into four lobes: Frontal, Temporal, Parietal, Occipital.

Functions of Brain Lobes

• Frontal Lobe: Planning, judgment, personality; damage may cause personality changes.

• Temporal Lobe: Memory and language processing; damage may lead to memory impairments.

• Parietal Lobe: Spatial location, attention, motor control; linked to specialized reasoning abilities.

• Occipital Lobe: Visual processing; damage may cause blindness.

The Endocrine System

• Coordinates psychological reactions and regulates bodily functions via hormone secretion.

• Major Glands:

  • Thyroid Gland: Controls metabolism via thyroxin.

  • Pituitary Gland: Master gland; regulates other glands.

  • Adrenal Glands: Secrete stress-related hormones.

  • Pineal Gland: Regulates sleep patterns via melatonin.

  • Pancreas: Regulates blood sugar levels.

Key Takeaways

1. Human and animal behavior originates from biological structures and processes, aiding treatments for psychological disorders.

2. The nervous system is specialized and hierarchical, with neuroplasticity allowing adaptation.

3. The endocrine system influences behavior by secreting hormones into the bloodstream.

4. Imaging technologies are used by biopsychologists to study brain structure and function.

5. The capacity to learn behaviors is influenced by genetics, persisting due to their contribution to organism fitness.

6. Psychologists study consciousness, including self-awareness and altered states.