Homeostasis - Breaking Out In A Sweat Flashcards
What is homeostasis?
The maintenance of a constant internal environment
Why would metabolic rate decrease if the body temperature became too high?
- Enzymes would become denatured due to them vibrating too
- This breaks the hydrogen bonds that hold together the 3D shape
- Loss of 3D shape means active site has changed shape so no longer works as a catalyst
Give an example of negative feedback in the body
The controlling of body temperature
How is temperature controlled in mammals?
- Thermoreceptors in the skin detect a change in temperature
- The receptors send impulses along sensory neurons to the hypothalamus (brain)
- The hypothalamus then sends impulses along motor neurons to effectors
-The effectors restore body temperature to normal
eg hair errector muscles contract when body temperature is too low
What is the process called of maintaining body temperature?
Thermoregulation
What feedback mechanism is stimulated when the body increases in temperature?
Sweat glands secrete sweat
What feedback mechanisms are inhibited when there is an increase in body temperature?
- Contraction of arterioles - this means they are relaxed and dialated
- Hair errector muscles - relax so hair lies flat
- Liver - reduces metabolic rate
- Skeletal muscle - relax so no shivering
What feedback mechanisms are stimulated when there is a decrease in body temperature?
- Arterioles contract - this means they constrict, reducing blood flow
- Hair errector muscles contract - hair raises
- Liver - increases metabolic rate
- Skeletal muscles contract - this causes shivering
What feedback mechanisms are inhibited when there is a decrease in body temperature?
Sweat glands - no sweat produced
How can skin control body temperature?
- Sweating
- Raising or flattening hair
- Route of blood flow via vasoconstriction and vasodilation
- Shivering
What is shivering and how does it maintain body temperature?
- Shivering is the uncontrolled contraction of normally voluntary muscles
- Energy is transferred to muscle tissue
- This results in more respiration and therefore heat
- Heat production can increase six-fold
Describe what happens in vasoconstriction
- Muscles in the arteriole walls contract
- This means the arterioles constrict, reducing blood flow to the surface capillaries
- The shunt vessel, located further below the surface of the skin, dialates so more blood flows through it
- This means blood is travelling further away from the skin’s surface so less energy is lost via radiation, conduction and convection
Describe what happens in vasodilation
- Muscles in the arterioles walls relax so the arterioles dilate
- The shunt vessel constricts, reducing the amount of blood flowing through it
- More blood is travelling closer to the skin’s surface so more energy is lost via radiation, conduction and convection
What will happen to metabolic reactions if body temperature falls below or rises above the normal range?
- Low temperatures cause a decrease in metabolic reactions as enzyme-controlled reactions slow
- High temperatures cause an initial rise in metabolic rate but then declines as the enzymes become denatured
Name things that must be controlled by the body through homeostasis
- Glucose concentration
- Ion concentration
- CO2 concentration
- Water levels
- pH of blood
- Temperature of the blood
What are the homeostasis control mechanisms trying to maintain?
- The norm value of a condition
- This is usually the optimum for that condition
eg body temperature is 37°C
What stimulates effectors to return a condition to the norm value?
-Nerve impulses or hormones from the control centre
What is negative feedback?
-The mechanism that restores a condition back to the norm value
Explain how negative feedback would act to restore a decreasing population to the norm for the environment
- A fall in population below the norm reduces competition
- This increases available food
- The population increases back to normal
How are hormone levels controlled?
By negative feedback
Describe how testosterone levels are maintained
- A change in testosterone levels is detected by the hypothalamus
- A decrease in testosterone causes gonadotropin-releasing hormone to be produced by the hypothalamus
- This stimulates the pituitary gland to release hormones that stimulate the testes to synthesise testosterone
What is positive feedback? Give an example of it occuring in the body
- Output from the control centre moves the condition further from the norm value
- In child birth - there is a constant increase in contractions which increases the pressure in the uterus, until the baby is born
How is a clot forming an example of positive feedback?
- Platelets stick to exposed collagen in the wall and each other
- They release chemicals that attract more platelets
- This continues until a clot has formed
A marathon runner feels cooler after dousing himself in water. How does this help to cool him?
-Increased energy lost by conduction and evaporation