Human Anatomy Final

Dendrite

Receives signals and carries them toward the cell body.

Cell body (soma)

Contains nucleus; metabolic center of neuron.

Axon

Carries impulses away from cell body.

Axon terminal

Releases neurotransmitters.

Myelin sheath

Insulation around axon that speeds conduction.

Schwann cell

Produces myelin in the PNS.

Node of Ranvier

Gaps in myelin where impulses jump.

Acetylcholine (ACh)

Neurotransmitter used by motor neurons and parasympathetic NS.

Epinephrine

Hormone/neurotransmitter released during sympathetic responses.

Action potential

Electrical nerve impulse.

Polarized

Resting state; inside negative.

Depolarization

Na⁺ enters cell, making inside positive.

Repolarization

K⁺ leaves cell, restoring negative charge.

Afferent neuron

Sensory neuron carrying information TO CNS.

Efferent neuron

Motor neuron carrying information FROM CNS.

Interneuron

Neuron within CNS connecting sensory and motor neurons.

Reflex arc

Pathway producing automatic response.

Tropic hormones

Hormones that stimulate other endocrine glands.

Plasma

Liquid portion of blood.

Formed elements

RBCs, WBCs, platelets.

Erythrocytes

Red blood cells.

Leukocytes

White blood cells.

Platelets

Clotting cell fragments.

Megakaryocytes

Bone marrow cells that produce platelets.

Hematocrit

% of blood volume occupied by RBCs.

Hemostasis

Stopping blood loss.

Hematopoiesis

Blood cell formation.

Coagulation

Clot formation.

Agglutination

Clumping of RBCs.

Hemolysis

Rupture/destruction of RBCs.

Arteries

Carry blood away from heart.

Veins

Carry blood toward heart.

Capillaries

Exchange vessels.

Arterioles

Small arteries.

Venules

Small veins.

Vena cavae

Return blood to right atrium.

Aorta

Largest artery leaving left ventricle.

Heart rate (HR)

Beats/minute.

Stroke volume (SV)

Blood pumped per beat.

Cardiac output (CO)

= HR × SV.

Peripheral resistance

Opposition to blood flow.

Blood pressure

Force exerted by blood on vessel walls.

Systole

Contraction.

Diastole

Relaxation.

Foramen ovale

Bypasses lungs (RA → LA).

Ductus arteriosus

Bypasses lungs (pulmonary trunk → aorta).

Ductus venosus

Bypasses liver.

Lymph

Fluid in lymphatic vessels.

Antigen

Substance that triggers immune response.

Antibody

Protein that binds antigen.

Pyrogen

Fever-causing substance.

Interferon

Antiviral protein.

Chemotaxis

Movement toward chemicals.

Membrane attack complexes (MACs)

Complement proteins that punch holes in pathogens.

Antigen-presenting cells (APCs)

Display antigens to activate T cells.

Oral cavity

Mouth.

Nasal cavity

Filters, warms, humidifies air.

Pharynx

Throat.

Larynx

Voice box.

Epiglottis

Prevents food entering airway.

Trachea

Windpipe.

Bronchus

Airway entering lungs.

Alveoli

Gas exchange sacs.

Surfactant

Prevents alveolar collapse.

Sympathetic (Fight or Flight)

Increases heart rate, dilates pupils, inhibits digestion.

Parasympathetic (Rest and Digest)

Decreases heart rate, stimulates digestion, conserves energy.

Resting (Polarized)

Na⁺ outside, K⁺ inside, inside negative.

Depolarization

Na⁺ channels open; Na⁺ enters.

Repolarization

K⁺ channels open; K⁺ leaves.

Sodium-Potassium Pump

Pumps 3 Na⁺ out and 2 K⁺ in; restores resting conditions.

Humoral immunity

B cells; action involves antibody production.

Cell-mediated immunity

T cells; action involves destruction of infected cells.