Homeostasis Flashcards
What is homeostasis?
Process of maintaining a constant internal environment within tolerance limits, despite changes in the internal and external environment
In a homeostatic feedback loop, what is a stimulus?
Deviation from optimal or normal value
In a homeostatic feedback loop, what is a receptor?
Cells or tissues that detect the stimulus and sends message to modulator
In a homeostatic feedback loop, what is the modulator?
Recieves message from receptor and coordinates a response, sending message to effector
In a homeostatic feedback loop, what is the effector?
Muscle or gland that recieves a message from the modulator and carries out a response
In a homeostatic feedback loop, what is a response?
The action of the effector that counteracts the stimulus
In a homeostatic feedback loop, what is negative feedback?
Factor returns to optimal or normal value
What are 4 types of receptors and their purpose?
- Chemoreceptor: detects oxygen and ion levels
- Osmoreceptor: detects changes in blood, osmotic pressure and solute concentrations
- Photoreceptor: Detects light
- Thermoreceptor: External or internal temperature variations
What are 9 homeostatic variables?
- Body temp
- pH levels
- CO2 levels
- O2 levels
- Ion levels
- Nutrients
- Water
- Blood pressure
- Red blood cell number
Draw a tolerance range diagram.
What are 4 factors that need to be maintained in homeostasis?
- Body temp (through thermoregulation)
- Fluid levels (through osmoregulation)
- Concentration of glucose
- Concentration of nutrients, wastes and gases
Why are negative feedback loops important?
Brings change that reduces the effect of the original stimulus
What are 2 glands that play a part in the endochrine system?
Posterior pituritary gland
- Antiduretic hormone
- From kidney
- Stimulates reabsorbtion of water
Thyroid gland
- Thyroxine
- From all tissues
- Increases metabolic rate
Draw a negative feedback loop for thermoregulation, when body has an increased temp
- Stimulus: Increased body temp
- Receptor: Thermoreceptors in skin and hypothalamus
- Modulator: Hypothalamus, sends message to sweat glands
- Effector: Body cells, sweat glands, skin, blood vessels
- Response: Increased sweating, change in behaviour
- Negative feedback: Body temp lowers
Give an example of thermolegulation mechanisms in a plant for a cold climate.
Eucalyptus tree
- thick, leathery, waxy leaves reduce heat loss providing insulation
Give an example of thermolegulation mechanisms in a plant for a hot climate.
Hakea
- Narrow vertical leaves reduce amount of direct sunlight
- Increases resistance to cold temps at night as well as frost
What is thermoregulation ?
The process animals maintain an
internal temperature within a tolerance range.
What is an endotherm?
Organisms that maintain a constant body temperature independent of the environment
What is an ectotherm?
Organisms that cannot maintain a constant body temp, it fluctuates with the external environment
What are 2 costs for endothermic organisms?
- Use more energy to maintain higher metabolic rate
- Need more food and hunting time to supply energy
What are 3 benifits for endothermic organisms?
- Body temp is independent of external temp, can live in extreme environments
- Can be active more often (night or day)
- Being active at specific may reduce predation
What are 2 costs for ectothermic organisms?
- Body temp reliant on external temp, limited to living in less extreme environmtents
- Can’t tolerate very high or very low temps
What are 3 benifits for ectothermic organisms?
- Heat source mainly environmental, lower energy requirements
- Don’t need as much food
- Wide tolerence range for internal temp
Give 3 reasons why temperature homeostasis is important
- Metabolic processes require an optimal temp
- Internal temps of higher then 37 degrees, enzymes can denature and stop functioning
- Internal temps lower than 37, chemical reactions in body start to slow
4 methods of heat transfer & definitions
- Conduction: Heat transfer through direct contact
- Convection: Currents of hot air transfer heat from surface of organism
- Radiation: Emmisions of heat waves
- Evaporation: Water turning into vapor absorbing heat
Name a thermoregulation structural adaptation for hot environments and give a real world example
Larger surface area allows heat loss via radiation
- Elephant ears: blood flow can increase to ears (physiological) and flap ears (behavioural) to loose body heat via radiation
Name and describe 4 thermoregulation physiological adaptations for hot environments
- Vasodilation: Nerves stimulate the dilation of blood vessels allowing heat loss via radiation (blushing)
- Sweating: Evaporation of sweat cools skin, assisted by air movement
- Metabolism levels: Decrease in metabolic rate, reducing amount of heat generated within body
- Pilorelaxation: Muscles attached to hair folicles relax, flattening hairs acting as insulation (not a human example)
Give 4 examples of a behavioral adaptations for hot environments with real world examples
- Sheltering from sun (lions)
- Licking forearms (kangaroos)
- Burrowing into ground (meerkats)
Name 3 structural adaptations for cold environments
- Insuation: Reduces heat loss to environment (blubber or fur)
- Surface area to volume ratio: Lower surface area to volume reduces heat loss
- Counter current heat exchange: Exchange of heat between 2 blood vessels flowing in opposite directions, warmer blood travelling to extremities heats up blood coming back
Name 2 physiological adaptations for cold environents
- Metabolism: Increasing metabolic rate through shivering (as its involuntary)
- Vasocinstriction: Narrowing blood vessels increases blood pressure and viscosity, decreasing plasma, increasing cardiac work (increasing metabolism)
Draw a negative feedback loop for a drop in external temperature
What are 4 behavioural adaptations for cold environments
- Huddling
- Sun bathing, or sticking flipper out of the water to catch sun rays
- Hibernating
- Migration to warmer areas
What are some behavioural adaptations for marine organisms affecting their body temp?
- Adjusting swim speed
- Seeking out warmer or cooler layers/currents
Name and explain 2 psysiological adaptations for marine organisms
- Metabolic adjustments: Based on temperature, slow down MR in cold water to conserve energy
- Anitfreeze protiens: Prevent ice crystal formation in bloodstream
Name and explain 3 structural adaptations for marine organisms
- Blubber: Thick layer of fat beneath skin to retain body heat by reducing heat loss to environment via ratiation
- Fur: Dense fur traps air providing an additional layer of insulation
- Countercurrent heat exchange: closely alligned networks or arteries and veins in flippers and fins
Name 3 and explain structural adaptations for marine birds
- Feathers: Trap air close to body reducing heat loss (insulation)
- Down feathers: Beneath outer layer, fluffy feathers give more insulation
- Feathers along wings usually darker colour for heat absorbsion
Name and explain a physiological adaptation for marine birds
Counter current heat exchange closely alligned networks or arteries and veins in legs, wings and feet
Name and explain 4 behavioural adaptations for marine birds
- Huddling: Share body heat reducing exposure to cold air (emperor penguins)
- Tucking: Tuck beaks and feat into feathers to conserve heat
- Sunbathing: To absorb heat
- Foraging times: Marine birds often limit foraging times to when temperature is desirable, returning to shelter when its too hot
What is osmoregulation?
Maintaining a fluid balance and concentration of electrolytes and other solutes that keep fluids becoming too diluted or concentrated. Key solutes are salt and glucose
What is osmolarity?
Or osmotic concentration, is the measure of concentration of a solution expressed as a number of solute particles per litre
Explain isotonic, hypertonic and hypotonic
Isotonic: Balances concentration between internal and outside environment
Hypotonic: Lower internal concentration than outside environment
Hypertonic: Higher internal concentration than outside environment
Name 4 ways water is essential for homeostasis
- All tissues use it
- Transports nutrients and dissolved gases
- Removes wastes
- Dissociates ions (dissolves things) allowing metabolic process to occur
What is dehydration? Explain what heppenes when someone is dehydrated
When body doesn’t have enough water, body fluids become hypertonic and individuals experience thirst.
- Low quantities of concentrated urine
- Blood pressure drop, increase in HR to compensate
What are 3 key functions of the kidney?
- Remove nitrogenous wastes
- Regulate water concentration in blood
- Maintain ion levels in blood
Draw a simple diagram of a kidney with labels
Explain what happens in the kidney
- In the glomerus, blood plasma is filtered from fine capillaries
- Filtrate is collected in the Bowman’s capsule
- Filtrate travels through loop of Henle, where nutrients and protiens are selectively reabsorbed back into the blood stream
What hormone controls osmoregulation
Antidiuretic hormone, controls permeability of DCT and collecting duct
Explain the steps of blood filtering through the kidney?
- Level of water in nplasma & tissue is regulated by varying the mount of water taken in and the amount reabsorbed from filtrate
- Osmoreceptors in hypothalamus detect osmotic potential of the blood. Hypothalamus controls secretion of the ADH from posterior pituritary gland as well
- Water is mostly reabsorbed from filtrate in distal confoluted tubule (DCT) and collecting duct
- Some water moves naturally due to concentration gradients (osmosis)
Draw a negative feedback loop for high water volume in blood
Draw a labelled diagram of a nephron
Where does filtration (in blood) take place
In the glomerulus in the nephron
Name 6 things that are selectively reabsorbed in the proximal convoluted tubule excluding water
- Glucose
- Ammino acids
- Sodium
- Potassium
- Chloride
- Bicarbonate ions
What is the main thing that the loop of Henle and DCT are responsible for reabsorbing?
Sodium
What is the main thing that the collection duct is responsible for reabsorbing?
Water
What is tubular secretion and where does it occur?
Takes unwanted materials from the blood and adds it to the filtrate, can be active or passive, occuring in the DCT
What pH range does the blood have to be kept within?
7.4 - 7.5
How does the body raise the pH of blood?
Secretes hydrogen and ammonium ions into filtrate, making urine more acidic
Name 3 real life examples of mechanisms reducing water loss
Western water-holding frog:
- Can swell and store its water for use in the dry season, can live underground for years at a time waiting for rainfall
Spinifex hopping mouse:
- Can concentrate its urine more than any other known rodent due to its long loop of henle, can also undergo aestivation a hibernation state where metabolism slows for months until water is available
Camels:
- Have wider tolerance range for water loss and concentration of their bodily fluids
Explain how nitrogenous wastes form and how they become toxic
- Protein is comprised of ammino acids, containing nitrogen
- When proteins break down nitrogenous parts split off and remainder of the molecule is converted into carbs or lipids
- That leftover nitrogenous waste can beome toxic and needs to be removed from the cell
- When nitrogenous wastes break down they form ammonia, then converting into urea or uric acid
What are the 3 forms of nitrogenous waste and their toxicity? Explain them
Ammonia - Most toxic, needs to be removed quickly, small molecule very soluble in water meaning lots of water is needed to remove it
Urea - Intermediatly toxic, also very soluble but less toxic moderate amount of water required to remove it. Converting ammonia to urea requires lots of energy
Uric acid - Least toxic, very insoluble little water is required to remove it less harmful then ammonia and urea but requires twice as much energy to convert ammonia to uric acid
Give examples of animals that produce he 3 types of nitrogenous wastes and a brief explanation why
Ammonia
- Most aquatic animals, fish and tadpoles
- Water in their environment to dilute the ammonia
Urea
- Mammals, adult frogs
- Must conserve water, so they convert ammonia and dissolve urea in urine
Uric acid
- Birds, insects, reptiles
- Is a solid mixed with little water, to conserve it
Make a table outlining the costs and benifits of the 3 nitrogenous wastes, include homeostatic energy, toxicity and water
What are osmoregulators?
Organisms that regulate their solute concentration to be higher or lower than their external environment
What are osmoconformers?
Organisms that allow their solute concentration to be equal to their external environment
What are 3 structural features that reduce water loss? How are they similar and how do they work?
- Scales on reptiles
- Hair on mammals
- Feathers on birds
All 3 contain keratine, a protein that hardens and waterproofs acting as a barrier preventing water loss via osmosis and evaporation
Name 3 physiological features that reduce water loss, their examples
- Birds and reptiles reabsorb waterfrom their cloaca, and exctering nitrogenous waste as uric acid to conserve water
- Australian desert frogs slow the production of urine by reducing the rate of glomerular filtration, the frog swells up like a ball retaining its urine for use in the dry season
- Australian desert hopping mouse can concentrate its urine more than any other rodent, water is conserved during reabsorbtion in the longer loop of henle meaning low volume, high concentration urine
Describe marine fish and their environment, and how they osmoregulate to keep water balance
Their internal environment more dilute than their external environment. They tend to gain salts and lose water.
- Drink almost continuously.
- Produce small amounts of urine.
- Actively excrete salts from special cells in their gills.
Describe freshwater fish and their environment, and how they osmoregulate to keep water balance
Their internal environment is more concentrated than their
external environment. They tend to lose salts and gain water.
- Rarely drink water
- Excrete large amounts of very dilute urine.
- Actively absorb salts by specialised cells in their gills.
Name 4 adaptations in marine bony fish for water balance
- Constantly drinking sea water.
- Eating food containing water
- High level of reabsorption in kidneys
- Excretes a low volume of highly concentrated urine
Name 3 adaptations in freshwater bony fish for water balance
- Does not drink water
- Low level of reabsorption in kidneys
- Excrete high volumes of dilute urine
Draw a negative feedback loop for a low water concentration in blood
What are xerophytes?
Plants that are well adapted to dry conditions, good at minimising water loss
What are halophytes?
Plants that are tolerant to saline conditions
What are 2 things plants do to maintain homeostatic regulation?
- Maintain an adequate uptake of water and nutrients from soil into leaves
- Control stomatal opening so that water loss is
minimised and carbon dioxide uptake is maximised.
Draw an lable the cross section of a leaf
Explain what plants are tolerant to in terms of their extra cellular fluid
- Plants are tolerant of changes in the solute concentration of extracellular fluid, as long as the extracellular fluid is hypotonic compared to inside their cells. Meaning the net movement of water is into the plant cells
- If the solute concentration of the extracellular fluid is hypertonic (Therefore water leaves the plant cells), water diffuses out of the cytoplasm, resulting in plasmolysis (cytoplasm shrinks) and, potential cell death
What does stomatal opening regulate in plants?
The rate of movement of water, CO2 and water between the atmosphere and internal spaces of the plant
What 3 structural features control stomata function? How do they work?
- Joined at their ends in pairs
- Cell walls are thicker on the pore side
- Bands of inelastic cellulose fibres run around each cell
Stomatal movement is the result of changes in the turgor (pressure) of the guard cells
– If water flows into the guard cells by osmosis, their turgor
increases and they expand
– The relatively inelastic inner wall makes them bend and draw away from each other
– Stomata opens
Draw a diagram of the stimuli, responses and outcomes of the stomata opening and closing
Name and describe 6 characteristicsts of xerophytes
- Closing stomata so fewer gases escape, only open stomata at night reducing water loss
- Thick waxy cuticle, more impermeable lowerind evaporation conserving water
- Hairs on leaf trapping humid air
- Sunken stomata making small pockets of moist air so water isnt lost during transpiration
- Rolled leaves maintaining humid air around stomata
- Extensive roots maximising water uptake
Give an example of a xerophyte
Australian Mulga
Name 6 characteristicts of halophytes
- Reduced leaves/spines
- Water storage structures in leaves, away from saline environment
- Thick cuticle and multiple epidermal layers
- Sunken stomata
- Long roots to search for water
- Structures to remove salt build up
