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What is homeostasis?
The maintenance of a constant internal environment
On which principle is homeostasis based?
- Negative feedback
- A deviation from a set level causes events to happen which reverse the change, bringing levels back to those set
What is the optimum temperature for enzyme action within mammals?
From where is external temperature monitored?
Thermo receptors in the skin
From where is internal temperature monitored?
The hypothalamus in the brain
What happens when a deviation is detected?
- A nerve impulse is sent to the thermoregulatory centre in the hypothalamus
- An impulse is then sent to an effector in order to reverse the change
How does the body respond to temperatures below the optimum?
- Thermo receptors send impulses to the heat gain area of the hypothalamus
- Impulses fem the heat gain area are sent along sympathetic neurones of the autonomic nervous system to a number of effectors
How do skeletal muscles raise body temperature?
They contract rapidly increasing heat generated the electron transport chain of respiration as more respiration is occurring
How do arterioles raise body temperature?
- The circular muscles in arteriole walls contract reducing blood flow to the skin
- This reduces the heat loss through radiation to the surrounding air
- Blood is diverted through shunt vessels deeper within the body
- This process is known as vasoconstriction
How do hair muscles raise body temperature?
- They contract causing hairs to raise
- This traps a layer of insulating air, reducing heat lost via convection
How does the adrenal gland raise body temperature?
- Adrenaline is released
- This increases respiration rates in organs and thus more heat is generated
How does the body respond to temperatures above the optimum?
- Thermo receptors send impulses to the heat loss area of the thermoregulatory centre of the hypothalamus
- Impulses from the heat loss area are sent along parasympathetic neurones of the autonomic nervous system
How do sweat glands lower body temperature?
- Sweat is released onto the surface of the skin
- The evaporation of the water uses heat energy cooling the skin and therefore the blood
How do arterioles lower body temperature?
- Circular muscle in arteriole walls relaxes
- This increases blood flow through them to the skin which heats up
- This increases heat loss through radiation
- This process is known as vasodilation
What happens if internal temperatures exceed 40oC?
- Negative feedback mechanisms stop
- Positive feedback begins as metabolic rates increase, releasing more heat energy
- Thus leads to greater deviation from set levels and can cause death
From where do ectotherms derive most of their heat?
- Their environment
- This means their body temperature will fluctuate along with environmental temperature
What happens when the environment of an ectotherm is cool?
Respiratory enzymes within the ectotherm are inactive meaning muscle contraction will be slow due to lack of ATP
How might an ectotherm attempt to gain heat from its environment?
- Basking in the sun to absorb solar radiation
- Gain dark coloration to maximise wavelengths of absorbed radiation
- Through respiration to release heat
How might ectotherms attempt to cool down?
- By sheltering in cool burrows during the day
- Through nocturnal behaviour
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