Homeostasis Flashcards
Define homeostasis.
The condition of a relatively stable internal environment, maintained within narrow limits.
What are 8 conditions needing controlling?
- Carbon dioxide
- Oxygen
- Wastes
- Temperature
- Salts
- Water
- pH
- Glucose
Why do carbon dioxide levels need to be maintained within limits?
When dissolved in water it forms carbonic acid, lowering pH and affecting enzyme activity.
Why do oxygen levels need to be maintained within limits?
To supply energy for cellular functioning.
Why do nitrogenous waste levels need to be maintained within limits?
High concentrations inhibit the reactions that form them and raise pH.
Why do temperature levels need to be maintained within limits?
Affects enzyme activity and metabolism.
Why do salt levels need to be maintained within limits?
Sodium from sodium chloride is important in regulating fluid levels as well as nerve transmission and muscle contraction.
Why do water levels need to be maintained within limits?
It maintains the concentration of cell contents at the correct level for cellular reactions.
What are the 6 stages of a steady state system?
- Stimulus
- Receptor
- Modulator
- Effector
- Response
- Feedback
Define stimulus.
Change in the internal environment.
Define receptor.
Detects change.
Define modulator.
Is the control centre, processes information from receptors, compares information from optimum and sends messages to the effector.
Define effector.
Carries out the response.
Define response.
Counteracts the stimulus.
Define feedback.
The original stimulus changed.
What are the 2 types of feedback loops?
- Positive feedback loop.
- Negative feedback loop.
What is a negative feedback loop?
An increase in one thing leads to a decrease in another.
What is a positive feedback loop?
An increase in one thing leads to an increase in another.
What are 4 ways to decrease heat loss?
- Vasoconstriction.
- Reduction in sweating.
- Conscious behaviour - Putting on a jumper.
- Reduction in surface area - Curl up into a ball.
What are 3 ways to increase heat production?
- Shivering.
- Increase in voluntary activity.
- Increased metabolic activity.
What are 4 ways to increase heat loss?
- Vasodilation
- Sweating.
- Conscious behaviour - Remove clothing.
- Increase surface area - spreading out.
What are 2 ways to decrease heat production?
- Decrease in voluntary activity.
- Decreased metabolic rate.
Write an SRMERF for when there is an increase in temperature. Include 4 effectors and 4 receptors.
S - Increase the temperature in blood.
R - Thermoreceptos in the hypothalamus.
M - Hypothalamus.
E - Sweat glands, blood vessels, skeletal muscles, thyroid.
R - increased sweat production, vasodilation, seeking shade/increased surface area, decreased thyroxine secretion decreases metabolic rate.
F - Decrease temperature in blood.
Write an SRMERF for when there is a decrease in temperature. Include 3 effectors and 3 receptors.
S - Decrease temperature in blood.
R - Thermoreceptos in the hypothalamus.
M - Hypothalamus.
E - Blood vessels, skeletal muscles, Thyroid.
R - Vasoconstriction, shivering/reduce surface area/seeking warmth, increased secretion of thyroxine increases metabolic rate.
F - Increase the temperature of the blood.
What does a small increase in temperature cause?
Can cause an increase in enzyme activity. This increases metabolic rate.
What does a significant increase in temperature cause?
It can cause enzymes to denature, leading to critically low metabolism. Cells can die. A person can experience heat stress and exhaustion. Cell membranes become too fluid, causing unwanted substances to enter and wanted substances to exit.
How is ammonia formed?
When organisms break down proteins and nucleic acids.
What can an increase in nitrogenous wastes cause?
An increase in the conetration of nitrogenous wastes the more toxic they become. An increase of ammonia in the blood can increase the pH. Enzymes only function within a certain pH tolerance range.
What happens if cellular pH is outside the optimal range?
Enzyme activity can decrease.
What happens if cellular pH is outside the tolerance range?
Enzymes can denature resulting in low metabolism.
What can increase in water content cause?
This can lead to a decrease in collision rates of reactants involved in biochemical pathways, slowing metabolism. This will lead to a hypotonic solution. Water will move into cells to reach an equilibrium. If too much water enters cells they will swell and burst.
What can a decrease in water content cause?
This can lead to a hypertonic solution. Causes water to move out of cells by osmosis. Causes dehydration and cells can shrink.
What can cause an increase in salts?
An increase in salt concentrations outside of cells may result in water being transported out of cells by osmosis.
