Brain and Behavior: The Biological Foundations of Psychology

2.1 The Nervous System

Overview of the Nervous System

The nervous system is a highly complex network responsible for coordinating all bodily functions and behaviors. It is composed of billions of nerve cells (neurons) and supporting cells (glia), and is divided into several major branches, each with specialized roles.

• Central Nervous System (CNS): Consists (Bao gồm) of the brain and spinal cord. The brain is the main processing center, while the spinal cord transmits information between the brain and the rest of the body.

• Peripheral Nervous System (PNS): Includes all neural elements outside the CNS. It connects the CNS to limbs and organs.

Divisions of the Peripheral Nervous System

• Somatic Nervous System (SNS): Controls voluntary movements and transmits sensory information to the CNS.

• Autonomic Nervous System (ANS): Regulates involuntary bodily functions (e.g., heart rate, digestion). It is further divided into:

  • Sympathetic Nervous System: Activates the body during stress ('fight or flight').

  • Parasympathetic Nervous System: Calms the body and conserves energy ('rest and digest').

Neurons: Structure and Function

• Neuron: The basic unit of the nervous system, specialized for transmitting information.

• Parts of a Neuron:

  • Dendrites: Receive incoming signals from other neurons.

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

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

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

• Glial Cells: Support, nourish, and protect neurons; outnumber neurons 9:1.

Neural Communication: Action Potentials

• Resting Potential: The electrical charge difference across the neuron's membrane when inactive (inside negative relative to outside).

• Action Potential: A rapid change in electrical charge that travels down the axon when the neuron is sufficiently stimulated (threshold is reached).

• All-or-Nothing Principle: An action potential either occurs fully or not at all.

• Myelin Sheath: Insulating layer around some axons that speeds up neural transmission; damage leads to disorders like multiple sclerosis.

Sequence of an Action Potential:

1. Neuron at rest: negative inside, positive outside.

2. Stimulation opens ion channels; sodium ions (Na+) rush in, reversing the charge.

3. Action potential propagates ( lan truyền) along the axon.

4. The actiPotassium ions (K+) flow out, restoring the negative charge (repolarization).

Synaptic Transmission

• Synapse: The tiny gap between neurons where communication occurs.

• Neurotransmitters: Chemical messengers released from axon terminals, crossing the synapse to bind with receptor sites on the next neuron.

• Some neurotransmitters excite (increase likelihood of firing), others inhibit (decrease likelihood of firing) the next neuron.

Major Neurotransmitters and Their Functions

Neurotransmitter	Main Functions	Disorders/Effects
Acetylcholine	Muscle activation, learning, memory	Blocked by curare (paralysis)
Dopamine	Pleasure, reward, movement	Excess: schizophrenia; Deficit: Parkinson's disease
Serotonin	Mood, appetite, sleep	Deficit: depression
GABA	Main inhibitory neurotransmitter	Deficit: anxiety, seizures
Glutamate	Main excitatory neurotransmitter	Excess: migraines, seizures
Norepinephrine	Arousal, alertness	Implicated in mood disorders

Neuropeptides

• Neuropeptides: Regulate the activity of other neurons; influence pain, emotion, pleasure, and stress.

• Endorphins: Natural painkillers; released during stress, exercise, and pleasurable activities.

Neuroplasticity and Neurogenesis

• Neuroplasticity: The nervous system's ability to change and adapt in response to experience (e.g., learning, recovery from injury).

• Neurogenesis: The formation of new neurons, especially in the adult brain; important for learning and memory.

Example: London taxi drivers develop larger brain areas related to spatial memory due to extensive navigation experience.

2.2 Brain Research

Methods for Studying Brain Structure

• Dissection: Examining autopsied brains to identify structures.

• CT (Computed Tomography) Scan: Uses X-rays to create detailed images of brain structure; useful for detecting injuries and tumors.

• MRI (Magnetic Resonance Imaging): Uses magnetic fields and radio waves to produce high-resolution images of brain anatomy without radiation exposure.

Methods for Studying Brain Function

• Case Studies: Observing behavioral changes following brain injury or disease (e.g., Phineas Gage).

• Electrical Stimulation of the Brain (ESB): Applying mild electrical currents to brain areas to observe effects on behavior.

• Ablation and Deep Lesioning: Surgically removing or destroying brain tissue to study resulting behavioral changes.

• EEG (Electroencephalography): Measures electrical activity (brain waves) via electrodes on the scalp; useful for studying sleep, epilepsy, and mental states.

• PET (Positron Emission Tomography) Scan: Tracks radioactive glucose to visualize active brain regions during tasks.

• fMRI (Functional MRI): Measures changes in blood flow to indicate brain activity during specific tasks.

Example: fMRI can show increased activity in the frontal brain when a person is lying compared to telling the truth.

2.3 The Cerebral Cortex

Structure and Function

• Cerebral Cortex: The outer layer of the brain, responsible for higher-order functions such as perception, thought, and language.

• Divided into two hemispheres (left and right), connected by the corpus callosum.

• Each hemisphere is divided into four lobes: frontal, parietal, temporal, and occipital.

Hemispheric Lateralization

• Lateralization: Specialization of function in each hemisphere.

• Left hemisphere: Language, math, sequential processing.

• Right hemisphere: Spatial abilities, pattern recognition, holistic processing, emotional expression.

• Split-brain research (e.g., Sperry, Gazzaniga) shows that each hemisphere can function independently when the corpus callosum is severed.

Example: In split-brain patients, the right hand may not know what the left hand is doing due to lack of communication between hemispheres.

Lobes of the Cerebral Cortex

Lobe	Main Functions	Key Areas
Frontal	movement, planning, reasoning, self-regulation, language production	Prefrontal cortex, Broca's area, primary motor cortex
Parietal	Sensory processing (touch, temperature, pain), spatial orientation	Primary somatosensory cortex
Temporal	Hearing, language comprehension, memory	Primary auditory cortex, Wernicke's area
Occipital	Visual processing	Primary visual cortex

Specialized Areas

• Broca's Area: Speech production (frontal lobe); damage causes expressive aphasia.

• Wernicke's Area: Language comprehension (temporal lobe); damage causes receptive aphasia.

• Mirror Neurons: Fire both when performing an action and when observing the same action; may be involved in imitation and empathy.

Disorders Related to the Cortex

• Spatial Neglect: Inattention to one side of space, often after right hemisphere damage.

• Visual Agnosia: Inability to recognize objects despite intact vision.

• Facial Agnosia: Inability to recognize familiar faces.

2.4 The Subcortex and Endocrine System

The Subcortex

• Hindbrain: Includes the medulla (controls vital functions), pons (sleep/arousal), reticular formation (attention, arousal), and cerebellum (coordination, skill memory).

• Midbrain: Connects hindbrain and forebrain; part of the brainstem, relays information.

• Forebrain: Includes the thalamus (sensory relay), hypothalamus (regulates drives and hormones), and limbic system (emotion, memory).

Limbic System

• Amygdala: Processes emotions, especially fear.

• Hippocampus: Essential for forming new memories and spatial navigation.

• Contains pleasure and aversion centers; involved in reward and addiction.

The Endocrine System

• Endocrine Glands: Secrete hormones into the bloodstream, influencing behavior and bodily functions.

• Pituitary Gland: The 'master gland,' regulates other glands and growth; controlled by the hypothalamus.

• Pineal Gland: Releases melatonin, regulates sleep-wake cycles.

• Thyroid Gland: Controls metabolism; imbalances affect mood and energy.

• Adrenal Glands: Release epinephrine (adrenaline) and norepinephrine during stress; produce corticoids and sex hormones.

Example: Overproduction of adrenal sex hormones can cause virilism or premature puberty; anabolic steroid abuse leads to serious health risks.

2.5 Psychology and Your Skill Set: Self-Regulation

Self-Regulation and Executive Function

Self-regulation is the ability to consciously control thoughts, emotions, and behaviors to achieve long-term goals. It is closely linked to executive functions in the prefrontal cortex.

• Executive Functions: Planning, goal-setting, attention control, impulse inhibition, and monitoring progress.

• Hot Emotional System: Driven by immediate impulses (limbic system).

• Cool Cognitive System: Reflective, considers long-term consequences (prefrontal cortex).

Example: The Marshmallow Test demonstrates that children who can delay gratification tend to have better life outcomes (health, finances, academic achievement).

Improving Self-Regulation

• Selective Attention: Focus on cues that support long-term goals, avoid temptations.

• Cognitive Reappraisal: Reframe situations to reduce temptation.

• Environmental Control: Change surroundings to minimize exposure to temptations.

• Practice: Self-regulation can be improved through repeated effort and strategy use.

Additional info: Socioeconomic status can influence self-regulation; children from less affluent backgrounds may focus more on immediate rewards due to life circumstances.

Summary Table: Major Brain Structures and Functions

Structure	Main Function(s)
Medulla	Vital life functions (breathing, heart rate)
Pons	Sleep, arousal, bridge between brain areas
Reticular Formation	Attention, arousal, muscle tone
Cerebellum	Coordination, skill memory
Thalamus	Sensory relay station
Hypothalamus	Drives, hormone regulation, emotion
Amygdala	Emotion (fear, aggression)
Hippocampus	Memory formation, spatial navigation
Cerebral Cortex	Higher-order thinking, perception, language

Key Equations and Concepts

• Resting Potential: $V_{rest} \approx -70 \ \mathrm{mV}$

• Action Potential Threshold: $V_{threshold} \approx -55 \ \mathrm{mV}$

• All-or-Nothing Principle: $\text{If} \ V_{membrane} \geq V_{threshold}, \ \text{action potential fires}$

Conclusion

The biological foundations of behavior are rooted in the structure and function of the nervous and endocrine systems. Understanding how neurons communicate, how the brain is organized, and how hormones influence behavior is essential for comprehending psychological processes and human behavior.