B1.2: Responses to a changing environment

Question	Answer
Define Homeostasis	Maintaining a stable internal environment
Define Vasodilation	When the body is too warm, blood flows near the surface through superficial capillaries. This allows more heat to be lost, which cools the body down.
Define Vasoconstriction	When the body is too cold, blood flow is restricted near the surface, allowing heat to be retained, warming the body up.
Sensory neurones	Take nerve impulses from receptors to the central nervous system
Relay neurones	In the central nervous system. Take nerve impulses from sensory neurones to motor neurones.
Motor neurones	Take impulses from the central nervous system to muscles or glands (effectors).
Name 2 hormones found in humans	Insulin, adrenaline, testosterone, oestrogen, and progesterone.
Define Reflex arc	Reflex actions bypass the brain, speeding up response times. Used when the body is in danger.
Give an example of a reflex action	Iris reflex - Iris contracts or expands depending on light level
Define Type 1 diabetes	Unable to produce insulin
Define Type 2 diabetes	Resistant to insulin produced

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