Homeostasis Flashcards
Define homeostasis.
The maintenance of a constant internal environment in the body.
What are the two types of stimuli?
Physical (light, heat, pressure)
Chemical (hormones, neurotransmitters)
List some stimuli and their responses.
Hot sun - move to shade
Something is hot to touch - rapidly pull hand back
Cold - shivering (increases metabolic rate, generating heat as a biproduct)
Low water content - thirst
What are most receptors?
Sensors
List some receptors.
Thermoreceptors (heat)
Chemoreceptors (smell, taste, oxygen)
Pain receptors (pain)
Mechanoreceptors (touch, pressure, sound, balance)
List some factors in the internal environment that are subject to homeostatic regulation.
Water
Oxygen
Carbon Dioxide
Ions (Calcium, Sodium, Potassium)
Nutrients (Glucose)
pH
Blood pressure
Blood volume
Number of red blood cells
What happens when the factors in the internal environment that are subject to homeostatic regulation fall outside the narrow homeostatic range?
They stimulate a corrective response.
What must organisms do to survive?
Maintain an appropriate internal environment
Avoid danger
Grow and develop normally
What must organisms do to to maintain an appropriate internal environment, avoid danger and grow and develop normally?
Detect stimuli (fluctuations in the external and internal environments, growth signals or danger).
Respond to the stimulus.
What does the ability to detect and respond allow organisms to do?
Grow, develop and reproduce
Survive challenges in the external environment
Maintain homeostasis
Define the feedback principal?
A mechanism in which the output or response affects the input or stimulus.
List the stages in the feedback pricipal.
Describe the stages in the feedback principal.
- Stimulus is detected by a receptor
- Information is transferred to a processing centre
- Processing centre sends the information to an effecto
- Effector carries out a response
- Stimulus is corrected and no longer stimulates the response
Define negative feedback.
When the stimulus initiates a response that acts to correct the stimulus.
Very important in homeostasis - always aims to restore the internal environment to an ideal situation.
Define set point.
The point at which the internal environment is restored to an ideal situation.
What may falling outside the tolerance limits induce?
Physiological stress
Define positive feedback.
When adjustments are made to reinforce the original stimulus.
Usually associated with growth and development rather than homeostasis.
Examples of positive feedback.
Stimulates and reinforces the process of metamorphosis of a tadpole to a frog. Once the process has begun, it continues to completion.
Release of prostaglandins from the placenta during childbirth. Stimulate contractions and positive feedback only discontinues when placenta is delivered.
What needs to be correct for body cells to work?
Temperature
Water levels
Glucose concentration
Define metabolic activity.
The sum of chemical reactions that occur within an organism to maintain life.
Generates heat.
What happens if metabolic activity produces too much heat?
The body can increase pH levels, reducing metabolic activity, resulting in less heat produced.
What happens when muscles contract more rapidly?
More Oxygen and Glucose is required, resulting in more heat and Carbon Dioxide.
List some physiological ways to reduce the amount of Carbon Dioxide and heat produced by the contraction of muscles.
Increased breathing rate reduces CO2 concentration.
Thermoreceptors in hypothalamus remove excess heat.
How does increasing breathing rate reduce CO2 concentration?
By passing more blood through lungs, releasing CO2 into atmosphere and oxygenating blood.
How do thermoreceptors in the hypothalamus remove excess heat?
They detect the heat increase and signal for sweat glands to operate.
List some behavioural actions to reduce heat.
Removing clothes
Seeking shade
List some structural adaptations to remove heat.
Vast capillary network over the alveoli creates large surface area for the CO2 – allows Oxygen exchange to work efficiently
Define hyperthermia.
When the internal temperatures rises much above the set point
Enzymes denature
Metabolic processes fail
Define hypothermia.
When the internal temperatures falls below the set point
Enzyme function slows significantly
Define ectotherm.
An animal that depends on a source of external heat.
Define homeothermic.
The ability to maintain a relatively constant internal body temperature.
Define endotherm.
An animal that retains heat generated by metabolic activity.
Define poikilothermic.
An organism whose body temperature changes with the temperature of its surroundings.
Examples of homeothermic ectotherms.
Desert lizards
Tropical marine invertebrates (blood lobster, sea apple, cleaner shrimp)
Desert pupfish
Examples of poikilothermic ectotherms.
Snakes
Lizards
Frogs
Toads
Invertebrates (spiders, starfish, snails)
Fish (flathead, silver perch)
Examples of homeothermic endotherms.
Kookaburras
Penguins
Emus
Koalas
Humans
Wombats
Salmon sharks
Examples of poikilothermic endotherms.
Fast-swimming fish (yellowfin tuna, billfish, most sharks)
Naked mole rat
Bees
Butterflies
Hibernating animals (bears, squirrels)
Define heat exchange by conduction.
The transfer of heat between objects in direct contact with each other.
Define heat exchange by convection.
When heat is conducted away from an object of high temp to low temp through rising air currents.
Rate varies with different materials.
Define heat exchange by radiation.
Transfers heat between objects not in direct contact (infrared waves).
Sun energy.
Define heat exchange by evaporation.
Change of liquid to vapour through heating.
Cooling.
What affects the ability to keep warm in the cold?
Counter current heat exchange
Shape and size
What does the excretory system do?
Removes metabolic waste materials (excretion) regulates much of the body fluids (osmoregulation).
How do animals produce nitrogenous wastes?
The breakdown of proteins and nucleic acid.
What determines the kinds of nitrogenous wastes excreted?
The animal’s habitat
Explain Ammonia’s effect on animal cells?
It highly toxic and must either be rapidly removed from the body or converted to a less toxic compound such (Urea or Uric acid).
How are Nitrogenous wastes formed in animals?
Deamination of amino acids
Nitrogen base degradation
Define osmoregulators.
Organisms that maintain internal water and solute concentration, despite fluctuations in the external environment.
What is the toxicity level of Ammonia?
High
What is the toxicity level of Urea?
Low
What is the toxicity level of Uric acid?
Low
What are Ammonia’s characteristics in relation to water?
Highly soluble
What are Urea’s characteristics in relation to water?
Soluble
What are Uric acid’s characteristics in relation to water?
Insoluble
What are the advantages of Ammonia?
Suitable for aquatic organisms/organisms surrounded by water
Requires very little energy to produce
What are the advantages of Urea?
Can be stored as a concentrated solution.
What are the advantages of Uric acid?
Can be stored for a relatively long period of time
Requires very little water to excrete/excreted as semi-solid (suitable for organisms in dry environments)
Suitable for birds/reptiles/land vertebrates that have shelled eggs as forms harmless solid in egg
What are the disadvantages of Ammonia?
Not suitable for land animals because it requires large amounts of water to store or excrete
Toxic
Can’t be stored
Requires large amounts of water to excrete
What are the disadvantages of Urea?
Requires water to excrete (intermediate between Uric acid and Ammonia)
More energy to produce than Uric acid but less than Ammonia
What are the disadvantages of Uric acid?
It’s a complex molecule that requires a large amount of energy to produce
Examples of Ammonia producers?
Most fish
Examples of Urea producers?
Mammals
Turtles
Sharks
Examples of Uric acid producers.
Reptiles
Birds
Insects
Land snail
What is the kidney’s function?
The filtering of toxins from the blood.
How do kidneys perform osmoregulation?
- Blood flows into hepatic artery, into nephron into, glomerular capsule under high pressure.
- Blood is separated into various components.
- Essential components are reabsorbed into blood capillaries surrounding nephron through proximal tubule, loop of Henle and distal tubule.
- Toxins are secreted into collecting tubule and flow into bladder where it is stored until it needs to be expelled.
What are the functional units of the kidneys and how many of these units do they contain?
Nephrons
Over 1,000,000
Describe how the length of the loop of Henle affects how it functions.
The longer the loop of Henle is, the more surface area there is to reabsorb water from filtrate (separation of blood components).
Examples of animals with loops of Henle of different lengths.
Desert animals have very long loop of Henle (spinifex hopping mouse)
Fish have very short loop of Henle
Give examples of structural adaptations for osmoregulation in animals.
Kidney structure (long loop of Henle)
Wax coatings
Shells
Layers of skin
Chitinous skeletons coated with wax
How does and animals kidney structure (long loop of Henle) help regulate water?.
Allows increased surface area to reabsorb water back into blood and create concentrated urine.
How do wax coatings, shells, layers of skin and chitinous skeletons coated in wax help an animal to regulate water?
Prevents dehydration
Reduces water loss
Reduces desiccation
Examples of animals with body coverings.
Wax coatings: some invertebrates (millipedes, centipedes)
Shells: crabs
Layers of skin: mammals, birds
Chitinous skeletons covered with wax: scorpions, beetles
Give examples of behavioural adaptations for osmoregulation in animals.
Live/survive in or next to aquatic environments
Burrow deep into mud until rains arrive
Travel long distances
How does living/surviving in or next to aquatic environments help to regulate water?
Water constantly available
How does burrowing deep into mud until rains arrive help to regulate water?
Organism hibernates/torpor until suitable conditions arrives to breed again
How does travelling long distances help to regulate water?
When a water source dries up they travel to next water source
Examples of animals that live/survive in or next to aquatic environments.
Frogs/fish/some invertebrates
Examples of animals that burrow deep into mud until rains arrive.
Burrowing frogs
Examples of animals that travel long distances?
Kangaroos
Give examples of physiological adaptations for osmoregulation in animals.
Burrow deep into mud until rains arrive
Store water in body
How does storing water in an animal’s body help it to regulate water?
They drink lots of water which is then stored in fatty tissue in hump
Examples of animals that store water in their bodies.
Camels
Define osmoconformers.
Organisms where the internal solute concentration changes with the concentration of solutes in the external environment.
Found only in marine ecosystems
Define hypotonic.
A solution that has a lower solute concentration than compared to another solution
Define hypertonic.
A solution that has a higher solute concentration than compared to another solution
Give examples of how marine animals conform water.
They have highly permeable skin surfaces
Their body fluids are isotonic with the surrounding seawater
How does having highly permeable skin surfaces help to conform water?
No energy is lost maintaining water balance
How does having body fluids that are isotonic with surrounding seawater help conform water?
Water is gained and lost at similar rates
The tolerance range of solute concentration is low allowing normal function
Give examples of osmoconforming animals?
Marine invertebrate species
Give examples of how marine organisms regulate water.
They maintain osmolarity by physiological means
They use excretory organs (kidneys, salt glands, specialised secretory cells in gills)
Some marine animals (shark, rays) have high urea levels in their body tissues
