Foundations of Biological Psychology: Neurons, Brain Structure, and the Nervous System

Biological Foundations of Psychology

Neurons: Structure and Function

The neuron is the fundamental unit of the nervous system, responsible for receiving, processing, and transmitting information throughout the body.

• Parts of a Neuron:

  • Dendrites: Receive incoming signals from other neurons.

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

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

  • Myelin Sheath: Insulates the axon, increasing the speed of neural conduction.

  • Glial Cells: Support, protect, and insulate neurons.

• Function: Neurons communicate via electrical impulses and chemical signals.

The Action Potential

An action potential is a rapid electrical signal that travels along the axon of a neuron, enabling communication within the nervous system.

• Resting Potential: The neuron maintains a negative charge inside relative to outside.

• Threshold: When stimulated, the neuron reaches a threshold and fires an action potential.

• All-or-None Law: The action potential either occurs fully or not at all.

• Propagation: The impulse travels down the axon to the synaptic terminals.

Equation:

$\text{Action Potential} = \text{Depolarization} \rightarrow \text{Repolarization} \rightarrow \text{Hyperpolarization}$

Neurotransmission: Communication Between Neurons

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

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

• Neurotransmitters: Chemicals that transmit signals across the synaptic gap.

  • Excitatory: Increase the likelihood of the receiving neuron firing (e.g., glutamate).

  • Inhibitory: Decrease the likelihood of firing (e.g., GABA).

• Key Neurotransmitters:

  1. Acetylcholine

  2. Dopamine

  3. Serotonin

  4. Norepinephrine

  5. GABA

  6. Glutamate

  7. Endorphins

• Reuptake and Enzymatic Degradation: Neurotransmitters are removed from the synaptic cleft by reuptake into the presynaptic neuron or by enzymatic breakdown.

Studying the Brain: Methods and Techniques

Lesioning and Brain Stimulation

Researchers use various methods to study brain structure and function, including lesioning and brain stimulation.

• Lesioning: Destroying specific brain areas in animals to observe behavioral changes.

• Brain Stimulation:

  • Deep Brain Stimulation (DBS): Invasive technique using implanted electrodes.

  • TMS (Transcranial Magnetic Stimulation), tDCS (Transcranial Direct Current Stimulation): Noninvasive methods for stimulating brain regions.

Neuroimaging Techniques

Modern imaging techniques allow scientists to map brain structure and function.

• Structural Imaging:

  • CT Scans: Computer-aided X-rays for brain structure.

  • MRI: Uses magnetic fields and radio waves for detailed images.

  • DTI: Diffusion Tensor Imaging for mapping white matter tracts.

• Functional Imaging:

  • EEG: Measures electrical activity via scalp electrodes.

  • MEG: Detects magnetic fields from brain activity.

  • PET: Uses radioactive tracers to visualize brain activity.

  • fMRI: Measures changes in blood flow related to neural activity.

Brain Structure: From the Bottom Up

The Hindbrain, Midbrain, and Forebrain

The brain is organized into three main regions, each with specialized functions.

• Hindbrain: Controls vital functions such as breathing and heart rate.

  • Medulla: Regulates breathing and heart rate.

  • Pons: Involved in sleep, waking, and dreaming.

  • Cerebellum: Coordinates balance and movement.

• Midbrain: Relays sensory information and controls arousal.

• Forebrain: Includes structures involved in emotion, memory, and higher cognitive functions.

Structures Involved in Emotion, Learning, Memory, and Motivation

• Thalamus: Directs incoming sensory messages to higher centers.

• Hypothalamus: Regulates hunger, thirst, emotion, and drives.

• Amygdala: Involved in emotion and aggression.

• Hippocampus: Essential for memory formation.

• Cingulate Cortex: Contributes to emotion and cognition.

The Cortex: Sensory and Motor Areas

The cerebral cortex is divided into lobes, each with specialized functions.

• Corpus Callosum: Band of fibers connecting the two hemispheres.

• Occipital Lobes: Contain the visual cortex.

• Parietal Lobes: Contain the somatosensory cortex for body sensations.

• Temporal Lobes: Contain the auditory cortex; left temporal lobe is crucial for language.

• Frontal Lobes: Contain the motor cortex; involved in planning, taking initiative, and voluntary movement.

Association Areas of the Cortex

• Found in all lobes, especially the frontal lobes.

• Integrate information from various brain areas.

• Crucial for language, reasoning, and higher-order thinking.

Brain Hemispheres: Lateralization of Function

The brain is divided into left and right hemispheres, each with specialized functions.

• Left Hemisphere: Controls language, writing, logical thought, and analysis.

• Right Hemisphere: Processes information globally, controls spatial perception, facial recognition, and emotional expression.

• Corpus Callosum: Connects the two hemispheres, allowing communication.

• Split-Brain Research: Demonstrates functional differences between hemispheres.

The Nervous System

Central and Peripheral Nervous Systems

• Central Nervous System (CNS): Consists of the brain and spinal cord; processes and interprets information.

• Peripheral Nervous System (PNS): Connects the CNS to the rest of the body.

  • Somatic Nervous System: Controls voluntary movements.

  • Autonomic Nervous System: Regulates involuntary functions.

    • Sympathetic Division: Prepares the body for action ("fight or flight").

    • Parasympathetic Division: Calms the body and conserves energy.

The Endocrine System

Pituitary Gland: The "Master Gland"

• Located just below the hypothalamus.

• Controls the release of hormones that regulate other endocrine glands.

• Secretes hormones involved in growth, metabolism, and reproduction.

• Produces "love hormones" such as oxytocin.

Other Endocrine Glands

• Pineal Gland: Secretes melatonin, regulating sleep cycles.

• Thyroid Gland: Controls metabolism by secreting thyroxin.

• Pancreas: Regulates blood sugar via insulin and glucagon.

• Gonads (Ovaries/Testes): Regulate sexual development and reproduction.

• Adrenal Glands: Release hormones for stress response (e.g., cortisol).

Applying Psychology: Coping with ADHD

Strategies for Coping with Attention-Deficit/Hyperactivity Disorder (ADHD)

ADHD is a complex neurodevelopmental disorder characterized by inattention, hyperactivity, and impulsivity. Effective coping strategies can help manage symptoms and improve functioning.

• Behavioral interventions (e.g., organizational skills training, time management).

• Medication (e.g., stimulants, non-stimulants) as prescribed by a healthcare provider.

• Environmental modifications (e.g., reducing distractions, structured routines).

• Support from family, teachers, and mental health professionals.

Summary Table: Major Divisions and Functions of the Nervous System

Division	Main Components	Primary Function
Central Nervous System (CNS)	Brain, Spinal Cord	Processes and interprets information; issues commands
Peripheral Nervous System (PNS)	Nerves outside CNS	Transmits information to and from CNS
Somatic Nervous System	Motor and sensory nerves	Controls voluntary movements
Autonomic Nervous System	Sympathetic and Parasympathetic divisions	Regulates involuntary functions
Sympathetic Division	Part of Autonomic NS	Prepares body for action ("fight or flight")
Parasympathetic Division	Part of Autonomic NS	Calms body, conserves energy

Key Terms and Definitions

• Neuron: A nerve cell; the basic building block of the nervous system.

• Action Potential: A brief electrical charge that travels down an axon.

• Neurotransmitter: Chemical messenger that crosses synapses between neurons.

• Lesioning: Destroying brain tissue to study its effects on behavior.

• Neuroimaging: Techniques for visualizing brain structure and function.

• Endocrine System: The body's "slow" chemical communication system; a set of glands that secrete hormones into the bloodstream.

• Pituitary Gland: The "master gland" that regulates other endocrine glands.

• ADHD: Attention-Deficit/Hyperactivity Disorder, a neurodevelopmental disorder.