AP psych unit 1
1. Parts and Functions of the Neuron
Neuron: Specialized cells that transmit electrical signals in the body. They are the fundamental units of the brain and nervous system.
Synapse: The small gap between two neurons or between a neuron and a target cell (like a muscle or gland). Neurotransmitters cross this gap to allow communication between neurons.
Myelin Sheath: A fatty layer that wraps around the axon of some neurons. It speeds up the transmission of electrical impulses (action potentials) by allowing signals to jump from node to node in a process called saltatory conduction.
Order of an Action Potential:
Resting Potential: The neuron is at rest, with a negative charge inside the cell and a positive charge outside.
Threshold: A certain level of depolarization is reached. Once this threshold is crossed, an action potential is triggered.
Depolarization: Sodium (Na+) ions rush into the neuron, causing the inside of the neuron to become more positive.
Repolarization: Potassium (K+) ions flow out of the neuron, restoring the negative charge inside.
Hyperpolarization: The neuron becomes more negative than its resting state before returning to resting potential.
2. Types of Neurons
Glial Cells: Non-neuronal cells that provide support to neurons. They help maintain homeostasis, form myelin, and protect neurons. They play a role in signal transmission, immune defense, and nutrient supply.
Sensory Neurons: Carry signals from sensory receptors (e.g., skin, eyes, ears) to the central nervous system (CNS).
Motor Neurons: Transmit signals from the CNS to muscles or glands to initiate action (e.g., muscle contraction).
Interneurons: Found in the CNS, these neurons process information between sensory and motor neurons and are involved in reflexes and higher functions (e.g., thinking, decision-making).
3. Neurotransmission
Resting Potential (Polarized): The neuron is at rest with a negative internal charge and a positive external charge. The resting potential is typically around -70mV. The sodium-potassium pump maintains this balance by moving Na+ out and K+ in.
Threshold: The minimum level of stimulation required to trigger an action potential. If the stimulus reaches the threshold, the neuron fires; if not, it does nothing (all-or-nothing response).
Action Potential (Depolarized): When the threshold is met, sodium channels open, and sodium ions rush into the cell, causing the inside to become more positive (depolarization). This electrical signal travels down the axon.
Refractory Period: After an action potential, the neuron temporarily cannot fire again until it has returned to its resting potential. This period ensures the signal travels in one direction.
Reuptake: The process by which neurotransmitters that have been released into the synapse are reabsorbed by the presynaptic neuron, terminating the signal.
Neurotransmitters: Chemical messengers that transmit signals across synapses. They are essential for mood regulation, motor control, and various physiological processes.
4. Neurotransmitters
Acetylcholine (ACh): Involved in muscle contraction, memory, and learning.
Too little: Linked to Alzheimer's disease.
Too much: Can cause muscle spasms or tremors.
Endorphins: Natural painkillers that promote feelings of well-being and happiness.
Too little: Can contribute to chronic pain, depression, or anxiety.
Too much: May cause a lack of pain perception, leading to risky behaviors.
Serotonin: Regulates mood, appetite, and sleep.
Too little: Associated with depression, anxiety, and sleep disorders.
Too much: Can lead to serotonin syndrome (agitation, confusion, etc.).
Dopamine: Involved in reward, motivation, and motor control.
Too little: Linked to Parkinson's disease and motor control issues.
Too much: Associated with schizophrenia and addiction.
Antagonists/Agonists:
Agonists: Enhance or mimic the action of neurotransmitters (e.g., morphine mimics endorphins).
Antagonists: Block or reduce the action of neurotransmitters (e.g., curare blocks acetylcholine at neuromuscular junctions).
5. Nervous System
a. Peripheral Nervous System (PNS)
Somatic Nervous System: Controls voluntary movements of skeletal muscles (e.g., walking, picking up objects).
Autonomic Nervous System: Controls involuntary functions (e.g., heartbeat, digestion).
Sympathetic Nervous System: Prepares the body for "fight or flight" by increasing heart rate, dilating pupils, and inhibiting digestion.
Parasympathetic Nervous System: Restores the body to a calm, resting state ("rest and digest").
b. Central Nervous System (CNS)
Medulla: Controls basic life functions such as breathing, heart rate, and blood pressure. Damage can be fatal.
Reticular Formation: Regulates wakefulness and sleep cycles. Damage may result in coma or inability to stay awake.
Cerebellum: Coordinates voluntary movements, balance, and motor learning. Damage can lead to poor coordination (ataxia).
Pons: Involved in sleep, respiration, and facial expressions. Damage may affect sleep cycles and facial control.
Thalamus: Acts as a relay station for sensory information (except smell) to the appropriate areas of the cerebral cortex. Damage may impair sensory processing.
Limbic System: A group of structures involved in emotion, memory, and motivation.
Hypothalamus: Regulates homeostasis, including hunger, thirst, body temperature, and the release of hormones.
Amygdala: Involved in processing emotions, particularly fear and aggression.
Hippocampus: Plays a critical role in memory formation and spatial navigation. Damage may cause amnesia.
ii. Higher Order Processing
Cerebral Cortex: The outer layer of the brain, responsible for complex thought processes like reasoning, perception, and decision-making.
Broca’s Area: Located in the left frontal lobe, responsible for speech production. Damage causes Broca's aphasia, where speech is non-fluent but comprehension is intact.
Wernicke’s Area: Located in the left temporal lobe, responsible for language comprehension. Damage leads to Wernicke’s aphasia, where speech is fluent but nonsensical.
Sensory Cortex: Located in the parietal lobe, it processes sensory input such as touch, pain, and temperature.
Motor Cortex: Located in the frontal lobe, it controls voluntary muscle movements.
Auditory Cortex: Located in the temporal lobe, it processes sound information.
Visual Cortex: Located in the occipital lobe, it processes visual information from the eyes.
iii. Hemispheric Specialization
Corpus Callosum: A bundle of nerves that connects the two hemispheres of the brain, allowing them to communicate.
Gazzaniga/Sperry (Split Brain): A condition where the corpus callosum is severed, leading to limited communication between the left and right hemispheres. This can cause unique cognitive and behavioral effects (e.g., the right hemisphere can control the left hand, but the left hemisphere controls speech).
Facial Recognition: Primarily occurs in the right hemisphere.
Speaking Fluently: Primarily occurs in the left hemisphere.
iv. Brain Scans
fMRI (Functional MRI): Measures brain activity by detecting changes in blood flow, revealing which areas of the brain are active during specific tasks.
EEG (Electroencephalogram): Measures electrical activity in the brain. It is used to detect patterns of brainwaves associated with different states of consciousness (e.g., sleep, alertness).
6. Endocrine System
How does it work?: The endocrine system is a network of glands that produce and secrete hormones into the bloodstream. These hormones regulate various bodily functions like metabolism, growth, mood, and reproduction.
Pituitary Gland: Known as the "master gland," it controls other endocrine glands and regulates growth, metabolism, and reproduction. It releases hormones such as growth hormone (GH), thyroid-stimulating hormone (TSH), and oxytocin (which is involved in childbirth and bonding). Damage to the pituitary can affect hormone production and lead to growth disorders, reproductive issues, or metabolic problems.