Animal Osmoregulation: Systems and Key Terms

Lab Exercise #5: Osmoregulation

• Osmosis is critical for animals as it impacts all cells
• Osmoregulatory systems are essential for maintaining extracellular fluid and internal body conditions, minimizing osmosis-induced cell volume changes

Key Terms in Osmoregulation

• Plasma membrane: A hydrophobic barrier that restricts solute movement into and out of cells, water moves through osmosis
• Aquaporin facilitates water movement across cell membranes
• Osmosis: Water moves to and from cells based on solute concentration gradients across the plasma membrane.
• Water moves from low to high solute concentration areas
• Water movement depends on thermodynamic considerations involving solute interactions
• Osmoregulatory system types depend on the animal group and aquatic environment like freshwater vs. marine

Osmoregulatory Systems

• Osmoregulatory systems involve active ion transport across epithelial surfaces, with water following the ion gradient through osmosis, and is often coupled with organ system modifications and water-drinking behaviors
• Osmoregulatory animals maintain body solute concentrations different from their environment, such as freshwater fish, which are hyperosmotic relative to their low-salt environment
• Osmoconformers do not maintain different osmotic concentrations from their environment, such as some marine animals
• Isotonic solutions have equal solute concentrations inside and outside the cell
• Hypotonic solutions have lower osmolarity, while hypertonic solutions have higher osmolarity

Additional Terms

• Osmolality measures the concentration of chemical particles in blood fluid
• Semipermeable membranes are found in aquatic animals.
• Hemolysis is red blood cell rupture and hemoglobin release occurs
• Crenation is when water loss via osmosis creates abnormal notched surfaces on cells

Red Blood Cells and Solutions

• Red blood cells are prone to crenation due to ionic changes or membrane abnormalities, disrupting their ability to maintain an isotonic state
• Echinocytes and acanthocytes are two types of crenated RBCs that possess a rounder form with spiny projections
• Cells are isotonic when solute and water concentrations are equal inside and outside the cell
• Metanephridia are excretory glands found in invertebrates like annelids, arthropods, and mollusca.

Experiment 1: Osmoregulation in Annelid Worms

• Four known sea water concentrations were used.
• Worms were weighed before and after immersion in the solutions for 30 minutes.
• An unknown seawater concentration was also used.
• Linear regression analysis was applied using the equation to determine the percent of unknown seawater which employed worms as osmometers to measure osmotic change
• Percent of initial mass indicates the relationship between worm mass and seawater percentage
• Sea water at 100% concentration equals 1000 mOsm
• Earthworm internal body solute concentration is between 250-400 mOsm, this enables predictions about mass changes in the experiment
• Weight decreases in worms placed in 50% (=500 mOsm) as the hypertonic external environment causes water to leave
• Weight increases in worms placed in 5% (=50 mOsm) as the internal environment has a higher solute concentration, causing water to move into the cell

Experiment 2: Osmotic Effects on Animal Cells

• Sheep red blood cells are placed in various solutions

• RBCs isotonically placed in plasma, maintain a similar concentration inside and outside the cell and exhibit no osmotic water movement, preserving their biconcave shape

• RBCs incubated in hypotonic solution 1 swell and enlarge due to water entering the cell

• RBCs incubated in hypertonic solution 2 shrink and fold (crenulate) because water exits the cell

• Very hypotonic solutions (300 mOsm) can cause cell lysis

• Measurements are taken using a microscope, recording the number of dashes (ticks) corresponding to cell diameter

• 40 dashes equal 100 micrometers.

• Cell diameter in each solution:

  • Plasma (isotonic)
  • Unknown 1 (hypotonic): Cells are larger
  • Unknown 2 (hypertonic): Cells are smaller

• Standard error mean bars indicate variance, with longer bars meaning more variance and likely significant differences between groups

• Osmotic changes are artificially induced, as mammalian cells have limited tolerance to osmolarity changes

• Kidneys regulate blood plasma osmolarity

• Changes in osmolarity can cause drastic changes to cells

Lab Exercise #6: Human Respiratory System Physiology

• Pulmonary ventilation involves air inflow and outflow between the atmosphere and the lungs' alveoli
• Spirometry, a method used by physicians and respiratory therapists, measures the volume of air moving in and out of the lungs
• Spirometry is crucial in diagnosing asthma and other lung conditions through measurements and mathematical computations
• Simple diffusion is sufficient for gas exchange in small animals
• Large animals rely on lungs and gills to enhance surface area for gaseous exchange
• Actively metabolizing cells need oxygen, and generate CO2 waste
• Lungs increase the surface area for gaseous exchange
• The human respiratory system uses branching tubes that terminate in alveoli
• Air entering and leaving the lungs measures respiratory physiology in humans
• The quantity of air exchanged determines the efficiency of lung ventilation and volume recorder

Respiratory System Components

• The respiratory system is a series of tubules and branches
• Bronchi are the main airways that branch into bronchioles
• Alveoli are clusters of small, membranous air sacs where O2 and CO2 rely on simple diffusion
• The total surface area of the alveoli is approximately the size of a tennis court, with thin walls to minimize diffusion distance

Factors That Influence Gas Diffusion Between Lungs and Blood

• Respiratory surface area
• Diffusion distance
• Concentration gradient

Ventilation

• A high concentration gradient is maintained by the movement of blood with low O2 and high CO2 to the lungs and pulmonary ventilation, which maintains high O2 and low CO2 in the alveolar air

Lung Volumes and Capacities

• Tidal volume (TV) is the air volume during any breath
• Inspiratory reserve volume is the additional air breathed in after normal inspiration
• Expiratory reserve volume is the additional air breathed out after normal expiration
• Residual Volume is the air volume that cannot be exhaled, It has lower O2 and CO2 concentrations than atmospheric air
• The mixing of fresh air with residual volume ensures sufficient gas diffusion to capillaries
• Vital Capacity is the maximum exchangeable air volume during a breathing cycle
  • VC Male Formula: (.025H in cm) – (.022A) – 3.60
  • VC Female Formula: (.041H in cm) – (.0180A) – 2.69
• The respiratory center regulates TV and breathing rate
• Peripheral chemoreceptors detect blood pH, O2, and CO2 levels
• Stretch receptors provide activity modulation in respiratory center neurons

Spirometer

• A spirometer is a volume recorder used to measure air exchanged during lung ventilation
• Spirometry is a common pulmonary function test measuring inhaled and exhaled air volume, speed, and ease

Exercise and Respiration

• Lung volumes, breathing rate, and minute respirometry volume during rest and exercise impact O2 requirements in tissues
• During exercise, the heart and lungs provide energy and remove carbon dioxide
• The heart pumps oxygen to muscles
• Oxygen use and CO2 production increase during exercise
• Breathing rate must increase from 15 breaths a minute (12 liters of air at rest) to 40–60 breaths a minute (100 liters) during exercise
• The circulation also speeds up supply oxygen to the muscles

Formulas

• Minute Respiratory Volume = Tidal Volume * Breathing Rate
• Inspiratory Capacity (IC) = TV + IRV
• Expiratory Capacity (EC) = TV + ERV
• Functional Residual Capacity (FRC) = ERV + RV
• Total Lung Capacity (TLC) = TV + RV + IRV + ERV
• At rest VC = 75% of TLC
• TLC-VC = RV

Diffusion Limitations

• Diffusion is limited as a respiratory strategy for organisms more than a few millimeters thick
• As the animal size increases, so does surface area-to-volume ratio decreases
• Diffusion depends on surface area
• Large organisms require more gas exchange, but have smaller surface area leading to inefficient diffusion
• Gas exchange is more challenging in water than in air

Respiratory System Response to Exercise

• Exercise increases metabolic demand, resulting in more CO2 and increased ventilation.
• Tidal volume and breathing frequency are responsible for most changes.
• The respiratory center in the brain stem, influenced by chemoreceptors and stretch receptors, controls changes to tidal volume and breathing rate
• Terrestrial invertebrates (humans) rely on CO2 for their respiratory drive, the respiratory system stimulates the body to increase ventilation for rid excess CO2
• Alveoli always have air due to reserve volume

Human Circulatory System Physiology

• The cardiac cycle in vertebrates involves sequential atrial and ventricular contraction
• Clinical diagnoses for cardiac arrhythmias and heart damage rely on ECG measurements and interpretation
• The heart's rhythmic contraction sequence is prompted by myocardial action potentials
• Body fluids conduct electricity, allowing easy recording of electrical activity at the body surface

Arterial System Functions

• The arterial system distributes blood after it is ejected
• The aerial system acts as a revisor of pressure, linking blood flow to arterial pressure difference
• Heart function and central blood pressure increase, while the autonomic nervous system directs contraction of smooth muscles in arterial walls
• Vasoconstriction raises blood pressure, while vasodilation lowers blood pressure
• The autonomic nervous system alters blood allocation based on the animal’s needs

Modification of Heart Activity

• Nervous system input adjusts cardiac action
• Excitation or impediment changes the contraction rate, heart rate increases as time between beats (T-P interval) and overall depolarization/repolarization cycle (P-T interval) reduces
• Affect is modifying the electrical signals conduction velocity
• Sympathetic and parasympathetic nerves innervate the heart directly
• Sympathetic cardiac nerves release norepinephrine
• Parasympathetic vagus nerves release acetylcholine.

Effects of Heart Rate Changes

• Heart rate changes affect arterial blood pressure in major arteries like the aorta
• Exercise-induced vasodilation can lower blood pressure, while increased heart rate increases it
• The autonomic nervous system uses peripheral loops to coordinate heart activity, arterial blood pressure, and blood flow

Baroreceptor

• Reflec regulates central arterial pressure to match metabolic needs and prevents vessel rupture or fluid leakage

Diving Reflex

• The diving reflex causes vasoconstriction in limbs, gut, and skin
• Blood is delivered to the brain and heart
• Selective vasoconstriction can raise central artery blood pressure to prevent heart rate which reduces oxygen and aerobic output

Term Definitions

• Myocardium coordinates heart muscle contraction
• Bradycardia: slow heart rate
• Tachycardia: fast heart rate
• Myogenic: signal originates within the muscle
• Neurogenic: signal originates from a nerve
• Systole: contraction
• Diastole: relaxation
• Baroreceptor: receptor that senses blood pressure
• Baroreflex: reflex to regulate blood pressure
• Depolarization: change in membrane potential
• Repolarization: return to resting membrane potential

ECG Waveforms

• P wave = atrial depolarization,
• Q,R,S complex = ventricular depolarization
• T wave = ventricular repolarization
• Atria contracts first, followed by ventricles
• Electrical activity of the heart can be seen in different waves and it ties in with the contraction 3 lead recordings vs hospital has 12
• Measure p-p to determine heart rate, pulse amplitude measures size

Experiment 2: Lab #7: Human Circulatory System Physiology Exp 1: Effects of Exercise on the ECG and Peripheral Circulation

• Peripheral circulation in a fingertip is represented by the pulse
• Vasoconstriction is indicated if its lowered, and vasodilation if its elevated
• Sensitivity is highest to constriction that it causes pulse to sharply decrease
• Blood goes to metabolizing cells and lungs when you exercise, resulting in blood being redirected, and peripheral circulation decreases in fingertip causing vasoconstriction