a&p i exam 2 notes

Tissue

A group of similar cells that work together to perform a function.

Histology

The study of tissues.

Organ

A structure made of two or more types of tissues working together.

Organ system

A group of organs working together to perform major body functions.

Epithelial tissue

Tissue that covers surfaces, lines cavities, and forms glands.

Connective tissue

Tissue that supports, protects, binds, and connects other tissues.

Muscle tissue

Tissue specialized to contract and produce movement.

Nervous tissue

Tissue that detects stimuli and transmits electrical signals.

Cell membrane

The outer boundary of a cell that controls what enters and leaves.

Cytoplasm

The material inside a cell between the membrane and nucleus.

Nucleus

The cell structure that contains DNA and controls cell activities.

Receptor

A structure that binds a specific chemical signal, such as a hormone.

Target cell

A cell that has receptors for a particular hormone or signal.

Stimulus

A change that causes a response.

Response

The reaction of a cell, tissue, or organ to a stimulus.

Secretion

The release of a substance from a cell or gland.

Hormone

A chemical messenger released by endocrine cells.

Endocrine gland

A ductless gland that releases hormones into body fluids or blood.

Exocrine gland

A gland that releases substances through ducts.

Target organ

An organ that responds to a particular hormone.

Trophic hormone

A hormone that stimulates another endocrine gland.

Negative feedback

A process where the result reduces or stops the original stimulus.

Positive feedback

A process where the result increases or strengthens the original stimulus.

Steroid hormone

A hormone made from cholesterol that binds to intracellular receptors.

Nonsteroid hormone

A hormone that usually binds to receptors on the cell membrane.

Cholesterol

A substance used as the starting material for steroid hormones.

Pituitary gland

The endocrine gland connected to the hypothalamus.

Hypothalamus

A brain region that controls the pituitary gland and helps maintain homeostasis.

Anterior

Located toward the front of the body or structure.

Posterior

Located toward the back of the body or structure.

Cortex

The outer region of an organ, such as the adrenal cortex.

Medulla

The inner region of an organ, such as the adrenal medulla.

Pancreatic islets

Groups of endocrine cells in the pancreas that release hormones.

Alpha cells

Pancreatic cells that secrete glucagon.

Beta cells

Pancreatic cells that secrete insulin.

Delta cells

Pancreatic cells that secrete somatostatin.

Neuron

A nerve cell that receives and transmits information.

Neuroglia

Cells that support, protect, and nourish neurons.

Dendrites

Neuron extensions that receive information.

Axon

A neuron extension that carries impulses away from the cell body.

Myelin

An insulating substance that surrounds certain axons.

Myelin sheath

The insulating covering around an axon.

Nodes of Ranvier

Gaps between sections of the myelin sheath.

Synapse

The junction where a neuron communicates with another cell.

Synaptic cleft

The small gap between communicating cells at a synapse.

Neurotransmitter

A chemical messenger that carries signals between cells.

Synaptic knob

An enlarged axon ending that releases neurotransmitters.

Action potential

An electrical impulse that travels along a neuron.

Resting potential

The electrical charge across a neuron membrane when it is not transmitting an impulse.

Threshold

The minimum stimulation needed to trigger an action potential.

Depolarization

A change where the inside of a neuron becomes less negative.

Repolarization

The return of a neuron membrane toward its resting negative voltage.

Hyperpolarization

A state where the inside of a neuron becomes more negative than resting potential.

CNS

The central nervous system, made up of the brain and spinal cord.

PNS

The peripheral nervous system, made up of nerves and ganglia outside the CNS.

Ganglion

A group of neuron cell bodies located outside the CNS.

Autonomic nervous system

The nervous system division that controls involuntary functions.

Somatic nervous system

The division that controls voluntary skeletal muscle movement.

Skeletal muscle

Muscle tissue usually attached to bones and controlled voluntarily.

Cardiac muscle

Involuntary muscle tissue found in the heart.

Smooth muscle

Involuntary, nonstriated muscle found in walls of hollow organs.

Myofibril

A contractile structure inside a muscle fiber.

Myofilament

A protein filament that makes up a myofibril.

Actin

The protein that forms thin muscle filaments.

Myosin

The protein that forms thick muscle filaments.

Sarcomere

The basic functional contractile unit of a myofibril.

Troponin

A protein that binds calcium during muscle contraction.

Tropomyosin

A protein that covers actin binding sites when muscle is relaxed.

Sarcoplasmic reticulum

The structure in muscle cells that stores and releases calcium.

Acetylcholine (ACh)

A neurotransmitter that stimulates skeletal muscle fibers.

Neuromuscular junction

The connection between a motor neuron and a skeletal muscle fiber.

Motor unit

One motor neuron and all the muscle fibers it controls.

Effector

A muscle or gland that carries out a response.

Reflex arc

The pathway followed by nerve impulses during a reflex.