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Animal Physiology III Internal Homeostasis - Coggle Diagram
Animal Physiology III
Internal Homeostasis
Ch44 Urinary / Excretory System
Excretory System Types
Four Steps of Excretion
Filtration
Blood → filtrate, cells/proteins stay
Reabsorption
Valuable solutes + water return via active transport
Secretion
Toxins/ions added to filtrate
Excretion
Urine leaves body
Systems Across Taxa
Protonephridia (flatworms)
Flame bulbs filter interstitial fluid
Metanephridia (earthworms)
Filter coelomic fluid; reclaim nutrients
Malpighian Tubules (insects)
Secrete waste into digestive tract without filtration
Kidneys (vertebrates)
Filter blood; highly regulated urine formation
Important Clarification
Defecation ≠ excretion (feces = digestive waste)
Nephron Structure & Concentration Mechanisms
Nephron Flow Path
4) Loop of Henle (Descending → Ascending Loop)
3) Proximal Convoluted Tubule (Reabsorption Step)
5) Distal Convoluted Tubule (Secretion Step)
6) Collecting Duct + Aquaporin (Excretion Step)
2) Bowman’s Capsule (Filtration Step)
1) Blood → Glomerulus Capillary
Region Functions
Proximal Tubule
Reabsorbs water, salts, glucose
Loop of Henle
Descending limb
Permeable to water; water exits (aquaporins
Ascending limb
Impermeable to water; pumps salt → creates osmotic gradient
Distal Tubule
Adjusts pH + ion concentration
Collecting Duct
Final water reabsorption controlled by ADH
Countercurrent Multiplier
Salt gradient in medulla allows concentrated urine
Adaptations
Desert mammals
Long loops → strong gradient
Vampire bat
Dilute urine when fed; concentrated urine when dehydrated
Birds/Reptiles
Uric acid reduces water loss
Freshwater fish
Very dilute urine
Marine fish
Drink seawater, excrete salt
Nitrogenous Waste & Evolutionary Adaptation
Urea
Requires energy to make
Moderately toxic
Produced in liver from ammonia
Conserves more water
Mammals & amphibians
Uric Acid
Highest ATP cost
Low solubility, excreted as paste
Water conservation and egg development
Used by birds, reptiles, insects
Evolutionary Pattern
Waste form reflects habitat water availability and life-history traits
Ammonia (NH₃)
Requires large amounts of water
Typical of aquatic organisms
Highly toxic
Source
Breakdown of proteins & nucleic acids → ammonia
Osmoregulation
Transport Epithelia
Specialized cells move solutes to control water balance (e.g., seabird salt glands)
Animals in Temporary Waters
Anhydrobiosis in tardigrades → near-total water loss survival
Habitat-Based Challenges
Terrestrial animals
Keratinized skin reduces evaporation
Behavioral methods (nocturnal)
Metabolic water from cellular respiration
Constant water loss
Respiration
Evaporation
Excretion
Freshwater fish (hypotonic environment)
Produce large volumes of very dilute urine
Actively absorb salts across gills
Gain water
Marine fish (hypertonic seawater)
Excrete salt via gills
Drink seawater
Lose water by osmosis
Osmoconformers vs Osmoregulators
Osmoregulators maintain stable internal osmolarity despite environment
Requires ATP
Osmoconformers (many marine invertebrates) match environment
Low energy use
Terms
Isoosmotic
Equal solute concentration, no net water movement
Hyperosmotic / Hypertonic
Higher solute; draws water inward
Hypoosmotic / Hypotonic
Lower solute; water leaves environment
Key Principle
Osmolarity
Solute concentration (mOsm/L)
Water moves toward higher solute concentration
“water follows salt”
Definition
Regulation of water + solute balance to prevent cell swelling or dehydration
Hormonal Regulation
ADH (Antidiuretic Hormone)
Trigger: high blood osmolarity
Effect: adds aquaporins → more water reabsorbed → less urine
RAAS (Renin → Angiotensin → Aldosterone)
Trigger: low blood pressure / volume
Effect: reabsorb Na⁺ + water, constrict vessels → raises BP
ANP (Atrial Natriuretic Peptide)
Trigger: high blood pressure
Effect: reduce Na⁺ + water retention → lowers BP
Ch45 Endocrine System
Nervous + Endocrine Coordination
Feedback Loops
Negative feedback stabilizes (most hormones)
Positive feedback amplifies (oxytocin in labor)
Neuroendocrine Pathway
Hypothalamus → Pituitary → Endocrine Glands → Target Tissues
Endocrine Glands & Hormone Actions
Parathyroid
Parathyroid
Breaks down Bone to Increase Blood Calcium
Adrenal
Medulla
Epinephrine
Fight or Flight (Adrenaline)
Norepinephrine
Fight or Flight (Adrenaline)
Cortex
Mineralocorticoid
Regulates Minerals (sodium, potassium, etc)
Glucocorticoid
Turns Fat into Sugar
Gonadocorticoids
Acts like Estrogen & Testosterone
Thyroid
Thyroid
Regulates Metabolic Rate
Calcitonin
Moves Calcium from Blood to Bones
Pituitary
Anterior
Thyroid Stimulating
Stimulates Thyroid
Adrenocorticotropic
Stimulates Adrenal Gland Cortex
Growth Hormone
Stimulates Mitosis
FSH & LH
Triggers Sperm/Egg Maturation and Releases Testosterone/Estrogen
Prolactin
Triggers Milk Release
Malanocyte
Stimulates Skin Melanin
Posterior
Oxytocin
Produces Milk & Labor Contractions
Antidiuretic (ADH)
Keeps Water Inside; Anti-Urination
Pancreas
Insulin
Regulates Sugar in Blood
Glucagon
Triggers Release of Sugar From Glycogen in Liver to Blood
Hypothalamus
Growth hormone-releasing (GHRH)
stimulates GH production in pituitary
Growth hormone-inhibiting (GHIH)
inhibits GH production in pituitary
Thyrotropin-releasing (TRH)
stimulates TSH production in pituitary
Corticotropin-releasing (CRH)
stimulates ACTH production in pituitary
Gonadotropin-releasing (GnRH)
stimulates gonadotropin (FSH, LH) production in pituitary
Prolactin-releasing (PRH)
stimulates prolactin production in pituitary
Prolactin-inhibiting (PIH) (dopamine)
inhibits prolactin production in pituitary
Gonads
Ovaries
Estrogen
Female Development & Ovarian Follicles
Progesterone
Prevents Shedding of Uterus Lining
Testes
Testosterone
Develops Male Characteristics & Sperm
Pineal
Melatonin
Regulates Sleep/Circadian
Thymus
Thymosin
Stimulates Production of T-Cells in Adolescence
Hormone Types & Signaling
Communication Chemicals
Neurotransmitter
Produced by brain cells, transmit to other brain cells, use cerebral spinal fluid (not blood)
Hormone
Polypeptide
Water-soluble; binds to receptors; multi-chain amino acid (partial protein)
Amine
Mostly water-soluble; some lipid-soluble, modified amino acid
Steroids
Lipid-soluble; non-polar; diffuses through membrane
Other Compounds
Nitric Oxide, ATP, etc...
Neuroendocrine
Hypothalamus → Pituitary → Endocrine Glands
Target Receptors
Water-soluble
Use cell membrane receptors
Lipid-soluble
Diffuse through membranes, DNA transcription changes
Communication Pathways
Exocrine
Secretions outside the body or in tubes leading out of the body
Paracrine
Local secretions for neighboring cells
Endocrine
Secretions in the blood
Autocrine
Self affecting secretions
Hormone Deficiency / Overload
Down-regulation
Hormone overload causes fewer receptors
Up-regulation
Hormone deficiency causes super sensitivity
Hormone Effects
Stimulation
Increases or triggers metabolic activity
Inhibition
Slows or stops metabolic activity
Agonists
A Hormone that increases the effect of another hormone, i.e. positive feedback
Antagonists
A Hormone that cancels out the effect of another hormone, i.e. negative feedback or homeostasis