B13.3 - Homeostasis Flashcards
What is meant by external environment? [1]
things going on outside our body
What is meant by internal environment? [1]
things happening inside our body and organisms
Why does the internal environment need to remain constant? [1]
so they can work efficiently
What are examples of things needed to remain constant in the internal environment? [5]
- pH levels
- temperature
- oxygen levels
- keeping the water level constant
- keeping carbon dioxide levels low
What are cells in blood surrounded by? [1]
plasma
What are other cells surrounded by? [1]
tissue fluid
What is homeostasis? [2]
the maintenance of a constant internal environment
What are some examples of internal conditions which are kept constant? [3]
- body temperature
- blood glucose concentration
- water potential of the blood
Where does information about conditions in the body go and how? [2]
- goes to the BRAIN
- from SENSORY RECEPTORS
What does the brain do if the level has gone beyond the normal range? [2]
- initiates a response
- to bring the level back to within the set points
How does the brain know that the level has been restored? [1]
- receptors inform the brain
What is the mechanism by which homeostasis operates? [1]
negative feedback
What is negative feedback? [2]
a mechanism that detects a change from the set point and triggers a response that brings the level back to its set point
What is negative feedback in short? [2]
detects and corrects
What’s the equation for respiration? [2]
glucose + oxygen –> carbon dioxide + water
Why do we need glucose? [2]
- for respiration
- for energy
What happens if blood glucose levels are too high? [1]
plasma loses water by osmosis
What happens if blood glucose levels are too low? [2]
- cells cannot respire and release the energy they need
- brain cells are especially dependent on glucose for respiration and die quickly if deprived of it
How does glucose get into your blood? [2]
- starch gets broken down by enzymes into glucose
- gets absorbed out of small intestine into blood
Where does starch get broken down? [2]
- mouth
- duodenum
Why do you need more glucose when you exercise? [4]
- muscles contract more
- energy is needed more
- more respiration needs to happen
- more oxygen & glucose needed
How is the pancreas involved in controlling blood glucose levels? [2]
- detects the blood glucose levels
- secretes 2 hormones
Which two hormones does the pancreas secrete? [2]
- insulin
- glucagon
What does insulin do? [1]
lowers blood glucose
What does glucagon do? [1]
increases blood glucose
What is the process taken when blood glucose levels are too high? [3]
- detected by pancreas
- insulin is released into the blood
- insulin lowers the blood glucose levels in 2 ways
What are the 2 ways insulin lowers the blood glucose levels? [2]
- more glucose is taken up by cells of the body from the blood for respiration
- causes glucose to be converted into glycogen in the liver cells
What is the process taken when blood glucose levels are too low? [4]
- detected by pancrease
- glucagon released into the blood
- glucagon increases blood glucose levels
- glucagon makes the liver change glucogen back into glucose
What are facts about Type 1 Diabetes? [2]
- people have this from birth/early childhood
- own immune system attacks the cells that make insulin in pancreas
What are facts about Type 2 Diabetes? [3]
- linked with obesity
- not enough insulin is produced or doesn’t work
- overweight people need to exercise more and eat less food
Why must body temperature be kept constant? [4]
- enzymes
- cell membranes
- diffusion
- liquids e.g. blood
Why must body temperature be kept constant for enzymes? [2]
- works best at optimum temperature
- denatured if temperature too high
Why must body temperature be kept constant for cell membrane? [1]
- becomes more fragile as temperature rises
Why must body temperature be kept constant for diffusion? [2]
- increases at higher temperature
- decreases at lower temperature
Why must body temperature be kept constant for liquids? [1]
- become more viscous as temperature drops
What does viscous mean? [1]
sticky/thick
What happens if there is more heat gain than heat loss? [2]
hyperthermia = increase in temperature
What happens if there is more heat loss than heat gain? [2]
hypothermia = decrease in temperature
How does the body gain heat? [2]
- metabolism
- movement
How does the body gain heat through metabolism? [2]
- respiration
- chemical reactions in the liver
How does the body gain heat through movement? [2]
- respiration
- friction within the muscles
How does the body retain (keep) the heat it has? [1]
- adipose (fat) tissues under the skin
What does adipose tissues help with? [1]
helps insulate against heat loss
How does the body lose heat? [4]
- evaporation of water
- in exhaled air
- sweat on the skin
- urine and faeces
How is heat lost from the skin? [1]
radiation
What do sensory receptors in the skin and brain detect? [2]
- skin: external changes in temperature
- brain: internal changes in temperature
What are the effectors when body temperature is being controlled? [3]
- sweat glands
- skeletal muscle
- skin arterioles
What are responses that occur when the temperature falls below 37 degrees celcius? [3]
- hairs stand on end
- shivering
- vasoconstriction
What are the effectors for each response when temperature drops? [3]
- erector muscles
- skeletal muscles
- muscles in the skin arteriole
How does hairs standing on end help keep heat in the body? [2]
- hair traps a layer of air
- acts as an insulator
- reduces heat loss by convection
What are responses that occur when the temperature rises above 37 degrees celcius? [3]
- hairs lie flat
- sweating
- vasodilation
What is the process that occurs when vasoconstriction happens? [5]
- body needs to keep heat
- skin arterioles constrict (get narrower)
- shunt vessel dilates
- less blood flows to skin
- less heat lost by radiation from skin surface
What is the process that occurs when vasodilation happens? [5]
- body needs to lose heat
- skin arterioles dilate
- shunt vessel constricts
- more blood flows to skin
- more heat lost by radiation
