Neuroscience: Neuron Function and Activity

Introduction to Psychology 2E

• Course title: Psychology 2E
• Chapter: 3 Biopsychology
• Textbook: OpenStax

The Nervous System

• A network of nerves controlling various functions (thought, heartbeat, coordination, etc.).
• Comprises the brain, spinal cord, and other components.
• Enables receiving external information and responding to it.

Neurons

• Specialized cells within the nervous system.
• Transmit electrochemical signals (firing) between neighboring neurons.
• Humans are born with over 100 billion neurons, mostly in the brain.

Neuron Structure

• Cell body: Integrates information, receives stimulation.
• Dendrites: Branch-like structures receiving stimulation.
• Axon: Long, extended fiber transmitting signals.
• Terminal buttons: Swollen bulb-like structures releasing neurotransmitters.

Myelin Sheath

• Fatty substance insulating axons.
• Speeds up signal transmission.
• Damaged myelin is associated with multiple sclerosis, impacting neural impulse timing.

Parts of the Neuron

• Dendrites: Branch-like structures extending from the cell body and receiving stimulation from sensory receptors or other neurons.
• Cell Body (Soma): Contains the nucleus and DNA. Integrates information and passes signals to the axon. Can sometimes receive stimulation directly.
• Axon: Long, extended fiber along which the neural impulse travels. Vary greatly in length, particularly in the spinal cord.
• Terminal Buttons: Swollen bulb-like structures containing neurotransmitters, the chemical messengers.

The Synapse

• The space between the terminal button of one neuron and the dendrite of another.
• Neurotransmitters released into the synapse from vesicles bind to receptors on the neighboring neuron.
• This either increases or decreases neuron activity.
• Neurotransmitters not bound can be broken down or reabsorbed.

Neurotransmitters

• Chemical substances transmitting information from one neuron to another.
• Released by synaptic vesicles in axon terminals.
• Bind to receptor sites on dendrites of receiving neurons.
• Can be either excitatory or inhibitory.

Reuptake

• Process of removing neurotransmitters from the synapse.
• Neurotransmitters either drift away, are broken down, or reabsorbed.

Examples of Neurotransmitters

• Acetylcholine: Affects muscle action and memory.
• Beta-endorphin: Associated with pain and pleasure.
• Dopamine: Related to mood, sleep, and learning.
• Norepinephrine: Affects heart, intestines, and alertness.
• Serotonin: Influences mood and sleep.

Drugs and Neurotransmitters

• Psychotropic medications regulate neurotransmitter balance.
• Agonist drugs mimic or strengthen neurotransmitter effects.
• Antagonist drugs block or impede neurotransmitter activity.
• Prescribed to correct imbalances.

Parts of the Nervous System

• Central Nervous System (CNS): Consists of the brain and spinal cord.
• Peripheral Nervous System (PNS): Contains somatic and autonomic divisions.
• Nerves: Bundles of axons from many neurons.

Peripheral Nervous System

• Somatic Nervous System: Controls purposeful body movements. Sensory and motor neurons transmit messages to and from the CNS.
• Autonomic Nervous System: Regulates the glands and muscles of internal organs. Contains sympathetic and parasympathetic divisions.

Autonomic Nervous System

• Sympathetic Nervous System: Activation during stress ("fight-or-flight"). Increases energy reserves for heightened senses and motor function.
• Parasympathetic Nervous System: Activation during relaxed conditions ("rest-and-digest"). Calms the body after stress. Both systems complement each other to maintain homeostasis (body equilibrium).

The Brain and Spinal Cord

• Brain: Composed of billions of interconnected neurons and glia. Bilateral (two-sided). Separable into lobes, though areas interact.
• Spinal cord: Delivers messages to and from the brain and has reflex mechanisms. Sensory and motor nerves send messages between the brain and the body.

The Two Hemispheres

• Lateralization: Each brain hemisphere specializes in specific functions.
• Left hemisphere controls the right side of the body, often associated with logical analysis, language, and mathematical computation.
• Right hemisphere controls the left side of the body, often associated with visual-spatial functions, facial recognition, and emotional understanding.

The Corpus Callosum

• Connects the left and right hemispheres of the brain.
• Crucial for communication and coordination between them.

Left Brain, Right Brain

• Different functional responsibilities between the brain hemispheres, with some degree of overlap.

Split-Brain Experiments

• Split-brain operations sever the corpus callosum in severe epilepsy cases.
• This can lead to strange behaviors, with each hemisphere acting largely independently.

Forebrain, Midbrain & Hindbrain

• Three major categories the brain can be divided into for functional analysis.

Forebrain Structures

• Cerebral cortex: Higher-level processing, consciousness, thought, emotion, language, and memory.
• Thalamus: Sensory relay center.
• Hypothalamus: Homeostasis.
• Pituitary gland: Master gland of the endocrine system.
• Limbic system: Emotion and memory circuitry.

Lobes of the Brain

• Frontal Lobe: Executive functions, planning, judgment, attention, reasoning, motor control, emotion, language.
• Parietal Lobe: Processes sensory and perceptual information (touch, temperature, pain).
• Temporal Lobe: Associated with hearing, memory, and language (auditory cortex, Wernicke's area).
• Occipital Lobe: Associated with visual processing (primary visual cortex).

Language Functions

• Two key areas—Broca's and Wernicke's area in the left hemisphere.
• Damage to these areas results in aphasia, difficulty understanding or producing language.

The Thalamus

• Serves as a relay center for most sensory information (excluding smell) before it's directed to other brain areas for processing.

The Limbic System

• Mediates emotional responses and memory.
• Amygdala: Processes emotion, particularly fear.
• Hippocampus: Crucial for learning, memory especially spatial memory.
• Hypothalamus: Regulates homeostasis, including body temperature, appetite, and blood pressure.

The Midbrain

• Reticular formation: Regulates sleep/wake cycles, alertness, and motor activity.
• Substantia nigra, Ventral tegmental area (VTA): Dopamine production, involved in movement, mood, reward, and addiction. Damage affects Parkinson's disease.

The Hindbrain

• Medulla: Controls automatic processes like breathing and heart rate.
• Pons: Connects the brain and spinal cord and involved in regulating brain activity during sleep.
• Cerebellum: Coordinates movement, motor skills, balance, and is involved in certain types of memory.

The Endocrine System

• A network of glands regulating body functions through hormones.
• Hypothalamus links nervous and endocrine systems via the pituitary gland.
• Pituitary gland: Master gland controlling other glands' hormone secretion.
• Thyroid: Affects growth, metabolism, and appetite.
• Adrenal glands: Secrete hormones in response to stress.
• Gonads: Produce sex hormones, crucial for reproduction and sexual motivation.
• Pancreas: Regulates blood sugar.