BIOL 371 FINAL Flashcards

BIOL 371 UofC Final

Flashcards Marked With “*”

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THEME 4: ANIMALS

Define Homeostasis

The maintenance of a stable internal environment suitable for metabolic processes, through responses to deviations from this stable state

What is the Significance of Homeostasis? (2)

1) Biochemical reactions are sensitive (require stable environment)

• Temperature, pH, [solute], [water], pressure

2) Organisms must regulate many internal variables

• Nutrients, gasses, pH, waste products, water/solutes, volume, pressure, temperature

Define Negative Feedback Loops

Homeostasis is maintained by regulating physiological variables with reference to a setpoint (generally in the integrator)

Homeostasis - Cell Location (Definition + 3 Implications)

Cell Location: Implications for how homeostasis is approached

1) External cells must face the environment

2) Cells of exchange surfaces must be alive

3) Internal cells provide homeostasis through regulation of internal environment

External cells must face the environment (2)

• Sometimes dead (i.e. superficial layers of skin)

• Sometimes protected by an acellular cuticle

Cells of exchange surfaces must be alive (3)

• Control access to internal environment

• Found inside the body, but dealing with aspects of the external environment

• Deal with wear & tear by: rapid turnover, produce lethal environment to microbes, covered by secretions to isolate them from the environment

*Internal cells: homeostasis by organism regulates the internal environment (example + 2)

E.g. Regulation of extracellular fluid solute content & volume

• Reduces amount of work cells have to do to maintain homeostasis, if internal cells are not isoosmotic with the environment

• Enables them to specialize

Define Osmoregulation

Regulation of the internal osmotic (water/salt/waste) environment

Define Circulation

Bulk flow of fluid within the body (water, solutes, nutrients, gasses)

Define Gas Exchange

Exchanging gasses with the environment

Define pH Regulation

Controlling the [proton (H+)] of body fluids

Define Water Potential (2)

• Tendency of water to move due to osmosis, hydrostatic pressure, gravity, humidity, etc.,

• Sum of osmotic potential, pressure potential, gravity, etc., across a membrane

Define Bulk Flow

Mass movement over long distances due to mechanical (hydrostatic) pressure

Define Diffusion

The movement of molecules a short distance from a region of higher concentration to a region of lower concentration down the concentration gradient to establish an equilibrium

Define Concentration Gradient

A spatial difference in the relative abundance of one type of molecule (or atom)

Fick’s Law (Equation + 4 Components)

Diffusion rate across a membrane = D A dC/dX

D = Diffusion coefficient - depends upon the characteristics of the solute and solvent, temperature, etc.,

A = Surface area of the membrane

dC = Concentration difference across a membrane

dX = thickness of the membrane

___ is the force driving diffusion

dC/dX

The quantity of particles moving across the membrane varies with ___, all else being equal

A

Define Osmoles

Total number of dissolved particles of solute per kg of solvent

• E.g. 1 mole of NaCl dissolved in 1 kg of water yields 2 moles of particles - 1 mole Na+, 1 mole Cl-

Define Osmolality

Osmotic concentration of a solution, measured in osmoles

Define Hypoosmotic

A solution having a lower osmolality than the reference solution (having a lesser concentration of solutes)

• E.g. Pure water is hypoosmotic to the red blood cell placed in it, which bloats (water goes into the cell)

Define Hyperosmotic

A solution having a higher osmolality than the reference solution (having a higher concentration of solutes)

E.g. A strong saline solution is hyperosmotic to the red blood cell placed within it, which shrivels (water moves from inside to the outside of the cell)

Define Isoosmotic

A solution having the same osmolality as the reference solution (same concentration of solutes)

• E.g. A bath of physiological saline is isoosmotic to the red blood cell placed within it, which stays the same (both environments, outside and inside, are the same & there is no net movement of water)

Define Osmosis

The tendency of water to diffuse across a selectively permeable membrane towards the side of greater solute concentration when the membrane is impermeable to the solute

Define Osmotic Potential (a.k.a soluble potential in plants)

Force exerted on water generated by differences in solute concentration across a semi-permeable membrane

Pure water has an osmotic potential of ___ - highest osmotic potential possible

Zero

Lower osmotic potential is a ___

Negative number (the more solute, the more negative the osmotic potential)

Water moves from ___ to ___ volumes

Less negative

More negative

Define Pressure Potential

Hydrostatic (mechanical) pressure affecting how water crosses membrane from volume of high osmotic potential to volume of low osmotic potential

What Happens When Pressure Potential is Opposed to Low Osmotic Potential?

Flow of water across membrane decreased, reversed or stopped

What Happens When Pressure Potential is Added to Low Osmotic Potential?

Flow of water across membrane increased

Pressures measured in ___ or ___

Pascals (Pa - animals)

Ψ (Psi - plants)

Water moves from volumes of ___ to volumes of ___

High water potential

Low water potential

Osmosis & The Living Cell: Significance to Animals

Cells will shrink or swell if not in an isoosmotic environment (without work on cell’s part)

• Net movement of water into the cell causing it to burst, or out of the cell shrivelling the cell (death in both cases)

Osmosis & The Living Cell: Significance to Plants

Cells will develop turgor pressure (hydrostatic) due to cell swelling and pressing against cell wall as water enters, which limits further influx of water

Bulk flow of transport fluids in animals requires application of ___

Hydrostatic pressure

• Affects exchange of water and solute between the bulk transport system and the extracellular fluid in closed circulatory systems

Hydrostatic pressure exerted on blood in upstream side of capillary bed ___

Exceeds osmotic potential of extracellular fluid

• Water and solutes leave capillaries

Osmotic potential of blood in downstream side of capillary bed ___

Exceeds hydrostatic pressure of extracellular fluid

• Water and solutes re-enter capillaries

Osmoregulation in Animals: Osmoconformer Strategies

Adjust osmotic potential of cells [Y] & extracellular fluid [X] to match environment [Z]

• Adjust internal environment to external (isoosmotic)

• Examples: Marine inverts, hagfish, elasmobranchs

Osmoregulation in Animals: Osmoregulators Strategies

Adjust osmotic potential of extracellular fluid [X] to match cells [Y] and regulate or protect [X] against the external [Z]

• Generally requires thick outer layer

• Spending effort

• Examples: Freshwater inverts & most vertebrates

Terrestrial Animals: Water/Salt; Gain/Loss

Terrestrial environments are dry, lose water to the environment

Marine Animals: Water/Salt; Gain/Loss

Marine environments are hyperosmotic (dry), lose water and gain salt from the environment

Freshwater Animals: Water/Salt; Gain/Loss

Freshwater environments are hyposmotic, gain water and lose salt to the environment

Body fluid ___ varies among aquatic organisms

osmolality

Some marine groups are ___ with seawater

Isoosmotic

Tonicity & The Environment: Marine Bony Fish (4)

• Hypoosmotic to environment, lose water and gain ions, especially through the gills

• Drink seawater to offset water loss

• Chloride cells in gills eliminate Na+, K+, & Cl- from blood (pump ions out from extracellular fluid to environment, pumped against concentration gradient, requires energy in the form of ATP)

• Produce small amounts of urine, conserving water, eliminating excess solute in feces

Tonicity & The Environment: Freshwater Bony Fish (4)

• Hyperosmotic to environment, lose ions and gain water, especially through the gills

• Do not drink water

• Produce large amounts of dilute urine (getting rid of water)

• Must replace ions from food or from transport across gill membrane

Tonicity & The Environment: Elasmobranchs (2)

• Isoosmotic to seawater, but concentrations of Na+, K+, Cl- all less than seawater, difference is made up by urea

• Still must deal with inward diffusion of Na+, K+, Cl- through gills, rectal gland secretes a highly concentrated salt solution

*Tonicity & The Environment: Land Dwellers (2)

• A dry environment = constant water loss through evaporation (across wet respiratory membrane, and across surface of skin)

• Water loss in urine and feces (waterproofing of outer layer of body, minimal exposure of gas exchange and digestive surfaces to air, minimizing electrolyte intake)

Define Excretion

Elimination of waste/toxins

• Aids in controlling content of extracellular fluid (salt/water/pH)

Major Means of Excretion in Animals (4)

• Diffusion into water (only in aquatic habitats)

Actions of excretory tubule (liquid waste):

• Filtration (non-selective): Small molecules & ions from body fluids or blood nonselectively pass through narrow spaces between cells into the tubule (hydrostatic pressure)

• Secretion (selective): Excess ions & toxic breakdown products are transported selectively from the body fluids or blood into the tubule (move ions to extracellular fluid)

• Reabsorption (selective): Nutrient molecules, some ions, and conserved water are returned to the body fluids or blood by transport equilibrium (only certain ions move)

Excretory Tubule (2)

• Composed of transport epithelium, allows active transport of ions between ECF and filtrate

• Other solutes and water diffuse in either direction

Filtration, reabsorption, & secretion result in production of ___

urine/filtrate

Different Functions of Excretory Tubule Localized Along Its Length (3)

• Filtration (isoosmotic): ECF/plasma enter excretory tubule

• Reabsorption (hyperosmotic): Occurs in proximal region of excretory tubule which contains water permeable membrane, and ions, sugars, and water leave excretory tubule

• Secretion (hyperosmotic): Occurs in distal region of excretory tubule which contains water impermeable membrane, and unwanted ions enter excretory tubule

Ammonia (NH3) Excretion

Ammonia is toxic, we must get rid of it

Ammonia (NH3) Excretion: Aquatic Animals (3)

• Diffusion into the environment (across body/gills)

• Excretion in filtrate/urine

• Ammonium (NH4+)/sodium exchangers

Ammonia (NH3) Excretion: Terrestrial (& some aquatic) Animals (3)

• Terrestrial animals cannot use diffusion or ion exchange with air (only excretion in filtrate)

• Produce urea (mammals, amphibians, sharks)

• Produce uric acid (land snails, insects, reptiles/birds; key for animals that develop in terrestrial eggs)

Protonephridium (4)

• Filters extracellular fluid

• Eliminates waste by means of current produced by ciliated flame cell

• Drains into series of ducts

• Reabsorption takes place in the ducts

Metanephridium (2)

• Filters coelomic fluid, reabsorption into circulatory system through blood vessels

• Associated with closed circulatory system

Malpighian Tubules (6)

Large absorptive surface area in contact with haemolymph involved in active secretion of uric acid,

• Ions into lumen of tubule

• Water follows through osmosis

• Filtrate released into gut

• Na+ and K+ actively transported out, water follows

• Solid uric acid released with faeces

Nephron (2)

• Found in vertebrates

• Filters water and solutes from blood, reabsorbs water and solutes to produce concentrated urine

Loop of Henle (2)

• Important in formation of concentrated urine

• Blood plasma is squeezed out into the Loop of Henle which is found in mammals (this region has high osmolality)

Homeostasis & Circulation: Why Circulate Fluids? (2)

• Processing

  (regulate pH, osmolarity, waste, add nutrients, gas exchange)

• Transportation and communication (hormones, heat, gasses, nutrients, immune components, solutes)

___ is adqeuate in small (>1mm thick) simple organisms, larger require a circulatory system

Diffusion

*Homeostasis & Circulation: Plants vs Animals (4)

Both use a series of tubes, but differ in:

• Nutrient, energy, and water sources

• Metabolic rates

• Cell structure

• Presence or absence of muscle

*Circulation in Animals (7)

• Occurs in heterotrophs with extracellular digestion

• High metabolic rates demand rapid circulation

• Tissues require oxygen, nutrients, and respiratory wastes must be carried away

• Move (vessels of system must be flexible)

• Muscular pump and flexible tubes (vasculature) for circulation

• Fluids must be forced through the vessels

• A cardiovascular system (pump and vessels)

Circulation in Animals: Open Circulatory System (2)

• Low pressure, slow, suitable for taxa with slow metabolic rates

• Hemolymph: Transport fluid in open circulatory system, comes into direct contact with tissues (extracellular fluid pool)

Circulation in Animals: Open Circulatory System (Continuation) (5)

• Heart(s) sit in hemolymph (filled hemocoel)

• On contraction, hemolymph expelled from heart via major arteries to other hemolymph spaces

• On relaxation, hemolymph enters heart from hemocoel

• Valves in heart wall maintain unidirectional flow

• Further distributed by body movements (directed flow to active tissues not possible; accessory hearts may supply limbs)

Circulation in Animals: Closed Circulatory System (3)

• Blood under pressure

• Blood vessels and heart form continuous closed circuit

• Found in forms able to sustain prolonged high activity rates (annelids, cephalopods, some crustaceans, all vertebrates)

Circulation in Animals: Closed Circulatory System (Continuation) (4)

• Blood contained within heart and vessels of circulatory system, not coming in direct contact with any of the tissues of the body

• Blood plasma is part of the extracellular fluid pool

• Capillary beds connect veins and arteries

• Confinement makes regulation, direction of flow, and high flow rates possible

The Heart

Muscular pump; creates pressure and directional flow in vasculature in closed circulatory systems, creates directional flow in open circulatory systems

In closed circulatory systems, heart maintains bulk flow of fluids in the face of ___

Resistance

Ohm’s Law

Flow = pressure/resistance

Closed Circulatory System: From Heart to Capillaries (2)

• Blood pressure drops with distance from heart due to greater total volume occupied, resistance

• Blood velocity decreases with distance from heart due to smaller diameters of vessels occupied, due to resistance, decreasing diameters of vessels

Closed Circulatory System: From Capillaries to Heart (2)

• Blood pressure continues to drop

• Blood velocity increases due to increasing diameters of fewer vessels

Blood Vessels In A Closed System (3)

1) Arteries

2) Veins

3) Capillaries

Arteries (Efferent Vessels) (3)

• Carry fluid away from heart

• Control blood distribution to the body by controlling vessel diameter (resistance)

• Depulsate pressure waves from the beating heart (elastic - expand/contract)

Veins (Afferent Vessels) (2)

• Carry fluid back to heart

• Store blood (easily expand)

Capillaries (3)

• Exchange of substances between blood & tissues (gas, fluids, solutes, nutrients, waste)

• Morphology of wall permits diffusion

• Huge cumulative surface area

Blood (ECF) Components in Vertebrates (4)

1) Plasma

2) Erythrocytes

3) Leukocytes

4) Platelets

Plasma

Component of the ECF that contains water, ions, proteins, nutrients, and gas

• Key ions are Na+, K+, Cl-, HCO3-, Ca+, H+

• Key proteins are globulins, albumin, fibrinogens

• Key gasses are O₂ and CO₂

Erythrocytes

Contain respiratory pigments

• Haemoglobin, haemocyanin, etc.,

Increase capacity of fluid to carry O₂ and CO₂

Leukocytes

White blood cells (immune system)

Platelets (Thrombocytes)

Help stop bleeding by forming clots

Variation in Circulatory System in Vertebrates Associated With: (3)

• Whether or not gravity is a factor affecting blood flow (requiring higher pressure)

• Where gas exchange takes place (gills, lungs, or lungs and skin)

• Thermoregulatory mode (endothermy or ectothermy)

Vertebrate Circulatory Systems: Fish (3)

1) 2 chambers

• Atrium: Thin-walled, receives O₂-poor blood from systemic circulation

• Ventricle: Thick-walled, muscular, sends O₂-poor blood through aorta to gills

2) Circulatory system forms single loop (single circuit)

3) Low-pressure (effects of gravity are negligible)

Vertebrate Circulatory Systems: Tetrapods (3)

1) Tetrapods evolved two separate circuits

• Low-pressure pulmonary circuit between heart and lungs

• High-pressure systemic circuit between heart and rest of the body

2) 3-4 Chambers: Each of these circuits required its own atrium, and increasing separation of the ventricle into two chambers

3) High pressure (gravity becomes a factor)

Vertebrate Circulatory Systems: Ectothermic Tetrapods (2)

1) Variable Circuit: Ectothermic tetrapods can bypass pulmonary circuit

• While diving

• Cutaneous respiration

2) Incomplete separation of ventricle: Ectotherms tolerate some mixture of deoxygenated blood and oxygenated blood due to low metabolic rates

Vertebrate Circulatory Systems: Mammals and Birds (3)

1) Complete separation between ventricles

2) Double Circuit: Blood can only pass between pulmonary and systemic circuits at the heart

3) Endothermic requires efficient delivery of O₂ to tissues

*Homeostasis and Gas Exchange: Why Is It Needed? (3)

All plants and animals must breathe

• Krebs cycle and oxidative phosphorylation (consume oxygen and produce carbon dioxide)

• Photosynthesis (consumes carbon dioxide and produces oxygen)

• pH regulation (via CO₂ regulation, forms carbonic acid)

Gas Exchange With The Environment (2)

Ventilation (Breathing)

• Bulk flow between the respiratory medium (air/water) and the gas exchange surface (body surface, lungs, gills, etc.,)

• Gas enters/exits extracellular fluid bulk flow system by diffusion

Gas Exchange and Gas Transport (2)

• Gas exchange takes place between blood and air or water (at the respiratory membrane) and between tissues and blood (diffusion in both exchanges)

• Gas transport is carried out by the blood (circulatory system)

Atmospheric Composition and Pressure (3)

• Atmospheric pressure decreases with altitude

• The composition of the atmosphere remains the same

• Each gas making up the atmosphere contributes towards total atmospheric pressure (has a partial pressure)

Partial Pressure Gradients in The Body (4)

• Diffusion in gas exchange is based on partial pressure gradients

• Oxygen and carbon dioxide partial pressures differ throughout the body

• CO2 produced in tissues (high partial pressure); O2 consumed in tissues (low partial pressure)

• Gradients maintained by circulatory system

Gas Exchange With The ECF

Gas Exchange Surface: Diffusion between air/water and the ECF

Surface area of gas exchange surface is ___ to mass and metabolic rate

proportional

Surface Area/Volume Relationships Are Important (2)

• Large animals need specialized gas exchange structures

• Lungs, gills, book lungs/gills, trachea (not just body surface)

Characteristics of a Good Gas Exchange Structure (3)

Reflected in Fick’s Law of Diffusion (Rate = D A dC/dX)

• Large SA

• Moist

• Thin