Homeostasis

Diffusion

movement of solutes from high → low concentration

Osmosis

movement of water across a semipermeable membrane (low solute → high solute)

Cortex

outer region of kidney where filtration occurs

Medulla

inner region of kidney, contains loops of Henle and collecting ducts

Renal artery/vein

bring blood to and from kidney

Ureter

tube carrying urine from kidney to bladder

Urethra

tube carrying urine from bladder to outside

Nephron

functional unit of kidney

Aquaporin

protein channel that allows water movement

Microvilli

folds that increase surface area (e.g., proximal tubule)

Vasa recta

blood vessels surrounding nephron loops

Countercurrent multiplier

loop of Henle mechanism concentrating urine

Renin

enzyme released when blood pressure/Na+ is low; activates angiotensin

Angiotensin

hormone that causes vasoconstriction and stimulates aldosterone

Antidiuretic hormone (ADH)

increases aquaporins in collecting ducts → more water reabsorbed

Aldosterone

hormone that increases Na+ reabsorption (and water follows)

Micturate

urinate

Incontinence

inability to control urination

Ectotherm

body temp depends on environment

Endotherm

generates its own heat

Radiation

heat exchange via infrared rays

Conduction

direct heat transfer between objects

Convection

heat transfer via moving air or water

Evaporation

heat lost when liquid water changes to vapor

Countercurrent circulation

arterial and venous blood flow in opposite directions to reduce heat loss

Torpor

temporary lowering of metabolism to conserve energy

Hypotonic solution

water enters cell, solutes leave, cell swells

Hypertonic solution

water leaves cell, solutes enter, cell shrinks

Isotonic solution

no net movement

Osmotic conformers

body fluid matches environment (e.g., marine invertebrates)

Hypoosmotic regulators

body fluids saltier than environment → actively excrete water, uptake ions (e.g., freshwater fish)

Hyperosmotic regulators

body fluids less salty than environment → drink water, excrete salt (e.g., marine fish, seabirds, reptiles)

Ammonia

very toxic, excreted by aquatic animals (requires water)

Urea

less toxic, excreted by mammals and amphibians

Uric acid

least toxic, paste-like, excreted by birds, reptiles, insects (water-conserving)

Protonephridia (flame cells)

flatworms

Metanephridia

annelids, molluscs

Malpighian tubules

insects, spiders

Green glands / antennal glands

crustaceans

Filtration (Kidney Function)

glomerulus → Bowman's capsule

Reabsorption (Kidney Function)

proximal tubule, loop of Henle, collecting duct

Secretion (Kidney Function)

distal tubule

Excretion (Kidney Function)

collecting duct → ureter → bladder → urethra

Filtration (Nephron Locations & Structures)

glomerulus → small molecules pass, proteins/blood cells stay

Reabsorption (Nephron Locations & Structures)

proximal tubule (microvilli, lots of mitochondria for ATP)

Secretion (Nephron Locations & Structures)

distal tubule (actively adds H+, K+, drugs)

Excretion (Nephron Locations & Structures)

collecting duct (regulated by ADH and aquaporins)

When blood pressure or Na+ is low

Kidney releases renin → angiotensin II forms → vasoconstriction + ADH + aldosterone → ↑ water & salt reabsorption → ↑ blood pressure

How is high blood pressure corrected

Stop renin, ADH, and aldosterone → less water & salt reabsorbed → more excreted → blood pressure lowers

Detrusor muscle

Smooth muscle that forms the wall of the bladder and contracts to empty it.

Internal sphincter

Smooth muscle that provides involuntary control.

External sphincter

Skeletal muscle that provides voluntary control.

Sequence of Urination

The process involving stretch receptors, spinal cord reflex, brain input, detrusor contraction, and sphincter relaxation leading to urination.

Behavioral Thermoregulation Adjustments

basking, burrowing, huddling, seeking shade

Physiological Thermoregulation Adjustments

sweating, shivering, vasodilation/constriction

Metabolic Thermoregulation Adjustments

only ectotherms (change enzyme activity, metabolic rate)

Countercurrent blood flow

Warm arterial blood warms returning venous blood, minimizing heat loss (e.g., penguin legs, whale flippers)

Torpor

Short-term drop in metabolism & body temp to save energy (e.g., hummingbirds overnight)

Small mammals (Hot temps)

nocturnal, burrowing, evaporative cooling

Large mammals (Hot temps)

sweating, panting, vasodilation

Small mammals (Cold temps)

high metabolic rate, fur insulation, shivering

Large mammals (Cold temps)

fat/blubber, seasonal coat changes, reduced extremity heat loss