Open vs Closed Circulatory Systems

Study Notes

Open: No distinction between circulating and extracellular fluid. This fluid is called hemolymph. The heart pumps hemolymph, but tissues like wing muscles receive oxygen directly from tracheae.
Closed: Distinct circulatory fluid enclosed in blood vessels and transported to and from the heart. The heart pumps blood to arteries which carry blood away from the heart. Arteries branch into capillaries where gas exchange occurs. Veins return blood to the heart.

Gas Exchange: Consists of 5 major steps:
- Ventilation: Movement of air or water through a specialized organ like lungs or gills.
- Diffusion at respiratory surface: Oxygen moves from air/water into blood and CO2 moves from blood into air/water.
- Circulation: Transporting dissolved oxygen and CO2 throughout the body via the circulatory system.
- Diffusion at tissue: Oxygen moves from blood into tissue and CO2 moves from tissue into blood.
- Cellular respiration: Cells use oxygen and produce carbon dioxide.

Bronchi: Narrow tubes that carry inhaled air to the lungs, branching off from the trachea.
Bronchioles: Even narrower tubes that branch off from the bronchi within the lungs.

Tiny sacs within mammal lungs that greatly increase surface area for gas exchange.

Inhalation: Diaphragm contracts, moving down and lowering pressure in the chest cavity. This causes lungs to expand and air to move in.
Exhalation: Diaphragm relaxes, chest cavity decreases (ribs relax), and air is exhaled.

Arteries: Tough, thick-walled vessels that carry blood away from the heart under high pressure.
Capillaries: Vessels with walls only one cell thick, allowing gas exchange between blood and tissues. Form capillary beds.
Veins: Thin-walled vessels that return blood to the heart.

Dendrite: Receives chemical signals and converts them into electrical signals.
Axon: Conducts electrical signals.
Cell Body: Integrates incoming electrical signals.

Involves the transport of sodium (Na+) ions outside the axon and potassium (K+) ions inside.

Parasympathetic: Promotes "rest and digest" functions that conserve or restore energy.
Sympathetic: Prepares organs for stressful situations ( "fight-or-flight")

Inner Ear: Transforms vibrations for hearing and balance.
Middle Ear: Transmits sound waves from the external environment to the inner ear.
Outer Ear: Collects pressure waves and funnels them into the ear canal where they strike the tympanic membrane.

Cornea: Transparent sheet of connective tissue that helps focus light.
Iris: Pigmented round muscle inside the cornea that controls the size of the pupil.
Pupil: Hole in the center of the iris that allows light to enter the eye.
Lens: Clear, curved structure that focuses incoming light onto the retina.
Retina: Back of the eye where the cornea and lens focus light.

Series of canals running along the head and body of fish. Water enters the canals through pores and bends kinocilia on hair cells which activate sensory neurons, helping fish detect water movement and vibrations.

Smooth Muscle: Found in intestines and arteries, helps move food and regulate blood pressure.
Cardiac Muscle: Found in the heart, pumps blood through the circulatory system.
Skeletal Muscle: Attached to the skeleton, move the skeleton by contracting.

Hydrostatic Skeletons: Use the hydrostatic pressure of enclosed body fluids or soft tissues to support the body.
Endoskeletons: Have rigid structures inside the body, such as bones.
Exoskeletons: Have rigid structures on the outside of the body like shells or chitinous armor.