Biological Psychology: Neurons, Neurotransmission, and Brain Structure

Biological Psychology

Introduction

Biological psychology explores the relationship between the brain, nervous system, and behavior. This field examines how specialized nerve cells (neurons) and supporting cells (glia) communicate, as well as the structure and function of major brain regions.

Neurons and Neural Communication

Neuron Structure and Function

• Neurons: Specialized nerve cells that send and receive information via electrical and chemical signals. They are the building blocks of the nervous system.

• Function: Transmit information as electrical signals called action potentials.

Neural Components

• Cell body (soma): Contains the nucleus; main metabolic center.

• Dendrites: Branch-like extensions that receive incoming signals from other neurons.

• Axon: Long fiber that transmits electrical impulses away from the cell body.

• Axon terminal: End of the axon; releases neurotransmitters into the synapse.

• Synapse: Gap between neurons where neurotransmitters are released to transmit signals to the next neuron.

Glial Cells

• Support and protect neurons ("glue" of the brain).

• Roles:

  • Provide nutrients and protection ("bodyguards").

  • Involved in physiological functioning (e.g., myelin formation).

  • Essential for healthy nervous system function.

How Does a Neuron Fire?

1. Resting Potential: Neuron is polarized (inside is negative, outside is positive).

2. Action Potential:

   • Brief electrical charge travels down the axon.

   • Triggered when the neuron is sufficiently stimulated.

   • All-or-none response: neuron either fires completely or not at all.

3. Refractory Period: Short period after firing when the neuron cannot fire again, regardless of stimulation.

Electrochemical Communication

• Neurons communicate using both electrical and chemical signals.

• Process:

  • Electrical signal (action potential) travels down the axon (electro).

  • At the axon terminal, neurotransmitters are released into the synapse (chemical).

  • Neurotransmitters bind to receptors on the next neuron, transmitting the signal.

• Excitatory messages: Increase the likelihood that a neuron will fire.

• Inhibitory messages: Decrease the likelihood that a neuron will fire.

Neurotransmitters

Definition and Function

• Chemical messengers that help neurons communicate with each other.

• Regulate mood, movement, learning, memory, and other functions.

Release and Removal

• Neurotransmitters are released from vesicles into the synaptic cleft.

• Bind to receptors on the postsynaptic neuron.

• Removed by drifting away, being broken down, or reuptake (reabsorbed by the presynaptic neuron).

Types of Neurotransmitters

• Glutamate: Main excitatory neurotransmitter; increases chance neurons will communicate. Associated with learning and memory. Excess may contribute to schizophrenia and other mental disorders.

• GABA (gamma-aminobutyric acid): Main inhibitory neurotransmitter; decreases brain activity. Important for anxiety regulation and sleep.

• Acetylcholine (ACh): Involved in arousal, attention, memory, and muscle movement. Deficits linked to Alzheimer's disease.

• Dopamine: Associated with pleasure, reward, voluntary movement, and attention. Deficits linked to Parkinson's disease; excess linked to schizophrenia.

• Serotonin: Regulates mood, appetite, sleep, and pain perception. Deficits linked to depression and anxiety.

Drug Effects

• Valium: Increases GABA activity (calming effect).

• Alcohol: Increases GABA, decreases glutamate.

• SSRIs (Selective Serotonin Reuptake Inhibitors): Block reuptake of serotonin, increasing its availability (used to treat depression).

Neural Plasticity

Definition and Mechanisms

• The brain's ability to adapt and change based on experience and learning.

• Myelination: Increases speed and efficiency of neural transmission.

• Pruning: Removal of unused synaptic connections, making the brain more efficient.

• Plasticity continues into adulthood, though it is most pronounced in childhood.

Major Regions of the Brain

Hindbrain

• Medulla: Controls vital functions like heartbeat and breathing.

• Pons: Involved in sleep and arousal.

• Cerebellum: Coordinates movement and balance.

• Reticular Activating System: Regulates arousal and attention.

Midbrain

• Transmits information between the hindbrain and forebrain; involved in vision and hearing.

Forebrain

• Manages complex cognitive activities, sensory and associative functions, and voluntary motor activities.

• Main components: cerebral cortex, thalamus, hypothalamus, limbic system.

Cerebral Cortex Lobes

• Frontal Lobe: Planning, decision making, executive functions, voluntary movement (motor cortex), language production (Broca's area).

• Parietal Lobe: Sensation (somatosensory cortex), spatial orientation.

• Temporal Lobe: Auditory processing, language comprehension (Wernicke's area), memory.

• Occipital Lobe: Vision processing.

Lateralization

• Cognitive function that relies more on one side of the brain than the other.

• Right hemisphere: spatial skills, facial recognition, simple speech.

• Left hemisphere: language, logic, analytical tasks.

Limbic System

• Emotional center: Involved in smell, memory, emotion.

• Amygdala: Fear, aggression.

• Hippocampus: Memory formation.

• Hypothalamus: Hunger, thirst, temperature regulation, links emotions to physical reactions.

• Thalamus: Relays sensory information to the appropriate areas of the brain.

Brain Mapping and Imaging Methods

• CT Scan: Uses x-rays to create images of brain structure; useful for detecting tumors.

• PET Scan: Uses radioactive substances to show brain activity.

• MRI: Uses magnetic fields to produce detailed images of brain structure.

• fMRI: Measures changes in blood flow to show brain activity over time.

• EEG: Records electrical activity of the brain via electrodes on the scalp; useful for studying sleep and seizures.

• MEG: Measures magnetic fields generated by brain activity.

• DBS (Deep Brain Stimulation): Modulates brain function via implanted electrodes; used for disorders like Parkinson's disease.

• TMS (Transcranial Magnetic Stimulation): Uses magnetic fields to stimulate or interrupt brain function.

Autonomic Nervous System

• Sympathetic: "Fight or flight" response; prepares body for action.

• Parasympathetic: "Rest and digest"; conserves energy and restores the body to a resting state.

Summary Table: Key Neurotransmitters

Neurotransmitter	Main Function	Associated Disorders	Drug Effects
Glutamate	Excitatory; learning, memory	Schizophrenia (excess)	Alcohol decreases activity
GABA	Inhibitory; anxiety regulation, sleep	Seizures (deficit)	Valium increases activity
Acetylcholine	Muscle movement, memory	Alzheimer's disease (deficit)	Anticholinergic drugs block activity
Dopamine	Pleasure, reward, movement	Parkinson's (deficit), Schizophrenia (excess)	Cocaine increases activity
Serotonin	Mood, sleep, appetite	Depression (deficit)	SSRIs increase activity

Additional info:

• Phineas Gage's case illustrates the role of the prefrontal cortex in personality and decision-making.

• Brain plasticity is essential for recovery after injury and for learning new skills.

• Neuroimaging techniques are critical for diagnosing brain disorders and understanding brain function.