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Hormones

Chemical messengers that travel in the blood and regulate body functions.

Peptide Hormones

Water-soluble hormones that bind to receptors on the cell membrane and trigger internal signaling cascades.

Steroid Hormones

Lipid-soluble hormones that pass through cell membranes and bind to receptors inside the cell, directly altering gene expression.

Amine Hormones

Hormones derived from amino acids that can behave like peptide or steroid hormones.

Hypothalamus

Gland that controls the pituitary gland by secreting releasing hormones.

Anterior Pituitary

Releases hormones like growth hormone, ACTH, TSH, LH, and FSH.

Posterior Pituitary

Releases ADH and oxytocin.

Thyroid Gland

Produces thyroxine (T4) and triiodothyronine (T3) to increase metabolism.

Parathyroid Hormone

Hormone secreted by the parathyroid glands to raise blood calcium levels.

Insulin

Hormone secreted by the pancreas to lower blood sugar.

Glucagon

Hormone secreted by the pancreas to raise blood sugar.

Negative Feedback

Mechanism that stabilizes hormone levels, inhibiting production based on high levels.

Positive Feedback

Mechanism that amplifies changes, as seen with oxytocin during labor.

Autocrine Signaling

Cell signaling where a cell targets itself.

Paracrine Signaling

Cell signaling that occurs between nearby cells.

Endocrine Signaling

Cell signaling that uses the bloodstream to reach distant cells.

Juxtacrine Signaling

Cell signaling that involves direct contact between neighboring cells.

Reception (Signal Transduction)

Step where a signaling molecule binds to a specific receptor.

Transduction (Signal Transduction)

Step where the signal is converted into a form that brings about a response.

Response (Signal Transduction)

Step where the cell performs an action in response to the signal.

G-protein-coupled receptors (GPCRs)

Receptors that activate a G protein to produce second messengers.

Receptor Tyrosine Kinases (RTKs)

Receptors that activate by dimerization and phosphorylation.

Ion Channel Receptors

Receptors that open to allow ions in or out, affecting membrane potential.

Intracellular Receptors

Receptors that bind steroid hormones and act directly on DNA.

cAMP

A common second messenger in GPCR pathways that activates protein kinases.

Calcium Ions (Ca²⁺)

Second messenger released to activate various cellular processes.

IP₃ (Inositol trisphosphate)

Molecule that helps release calcium from storage.

Innate Immunity

The body’s immediate defense against infection; nonspecific.

Inflammation

Response where damaged cells release histamine, leading to blood vessel permeability and entry of white blood cells.

Adaptive Immunity

Specific immune response involving lymphocytes (B cells and T cells).

B cells

Lymphocytes that mature in bone marrow and produce antibodies.

T cells

Lymphocytes that mature in the thymus and help or kill infected cells.

Antibody-Mediated Response

Response where activated B cells become plasma cells that secrete antibodies.

Cell-Mediated Response

T cell response where helper T cells recognize antigens, and cytotoxic T cells kill infected cells.

Major Histocompatibility Complex (MHC)

Molecules that display antigens to T cells; class I for cytotoxic T cells and class II for helper T cells.

Lymphatic System

System that returns leaked fluid to the blood and filters lymph.

Central Nervous System (CNS)

Includes the brain and spinal cord; responsible for integration and processing of information.

Peripheral Nervous System (PNS)

Consists of nerves and ganglia that transmit signals to and from the CNS.

Action Potentials (AP)

Rapid changes in membrane potential due to ion movement across the axon membrane.

Resting Potential

Stable membrane potential at approximately -70 mV maintained by the sodium-potassium pump.

Depolarization

Phase where sodium channels open, allowing Na⁺ to rush in, making the inside of the membrane positive.

Repolarization

Phase where K⁺ channels open after depolarization, allowing K⁺ to exit and restore negative inside.

Hyperpolarization

Phase where K⁺ channels remain open too long, making the membrane more negative.

Synaptic Transmission

The process of converting an electrical signal into a chemical signal, then back to electrical.

Neurotransmittters

Chemicals that transmit signals across a synapse between neurons.

Acetylcholine (ACh)

Neurotransmitter that activates skeletal muscles and is used in parasympathetic pathways.

Dopamine

Neurotransmitter involved in pleasure/reward and motor control.

GABA

Major inhibitory neurotransmitter in the brain.

Glutamate

Main excitatory neurotransmitter in the CNS.

Reflex Arc

Simplified neural pathways for automatic responses to stimuli.

Neural Plasticity

The brain's ability to form new connections in response to learning or injury.

Multiple Sclerosis

Disease where the immune system destroys myelin, slowing down conduction.

Parkinson's Disease

Degeneration of dopamine-producing neurons.

Alzheimer's Disease

Condition characterized by accumulation of plaques and tangles, leading to memory loss.

Epilepsy

Condition characterized by uncontrolled electrical activity in the brain, causing seizures.