HOMEOSTASIS AND RESPONSE
HOMEOSTASIS
Homeostasis: the regulation of internal conditions in the body, needed to maintain the
optimum conditions for body function
Homeostasis controls
o Blood glucose concentration
o Body temperature
o Water levels
The control systems involved are:
o Nervous system: uses electrical impulses
o Endochrine system: uses chemical molecules
All control systems have:
o Receptors: cells that detect stimuli
o Co-ordinators: process the information received from receptors
o Effectors: a muscle or gland that brings a response to bring conditions in the body
back to optimum levels
NERVOUS SYSTEM
Uses electrical impulses to enable you to react quickly to your surroundings and coordinate
your behaviour
PROCESS
o Receptors detect stimuli
o Impulses from receptors pass along the sensory neurones to the brain or spinal cord
o Brain coordinates response and impulses are sent along motor neurones from the
brain to the effector organs
o Effectors carry out a response
SYNAPSE: the junction between 2 neurones
o Electrical impulse arrives at the synapse
o Chemicals are released from the first neurone
o The chemical diffuses across the synapse
o The chemical attaches to the next neurone
o An impulse is triggered in the next neurone
THE REFLEX ARC
o Reflex actions are responses that are automatic, extremely quick and protect the
body
o Bypasses brain processing so the response is much quicker
o Mediated by the spinal cord
o PROCESS:
, The finger comes into contact with a flame
Pain receptors in the skin cause the impulse to be transmitted through the
sensory neurone
Impulses reach the spinal column and an effector response is sent to
muscles through motor neurones
Muscles in the arm/hand move the finger out of the flame
CONTROL OF BLOOD GLUCOSE
If glucose levels are too high, water leaves cells by osmosis; if the glucose levels are too low,
there is not enough for respiration
Blood glucose levels lower during exercise due to increased respiration
WHEN BLOOD GLUCOSE LEVELS ARE TOO HIGH:
o Insulin is released by the pancreas
o Insulin tells the liver to take glucose out of the blood, turn it into glycogen and store
it
o Blood glucose levels return to normal
WHEN BLOOD GLUCOSE LEVELS ARE TOO LOW:
o Glucagon is released by the pancreas and insulin stops being released
o Glucagon tells the liver to break glycogen into glucose and release it into the blood
o Blood glucose levels return to normal
DIABETES
o Type 1:
The pancreas cannot produce enough insulin
Treated with insulin injections
o Type 2:
Body cells no longer respond to insulin
Obesity and age are risk factors
Treatments include exercise and reducing simple carbohydrates
ENDOCHRINE SYSTEM
Hormone: a chemical released by an endochrine gland that travels through the blood to the
receptor of a target cell
The endochrine system is made up of glands that secret hormones directly into the
bloodstream
PITUITARY GLAND
o Master gland
o Stimulates other glands to release hormones
PANCREAS
o Secretes insulin
o Controls blood glucose levels
THYROID
o Secretes thyroxine
HOMEOSTASIS
Homeostasis: the regulation of internal conditions in the body, needed to maintain the
optimum conditions for body function
Homeostasis controls
o Blood glucose concentration
o Body temperature
o Water levels
The control systems involved are:
o Nervous system: uses electrical impulses
o Endochrine system: uses chemical molecules
All control systems have:
o Receptors: cells that detect stimuli
o Co-ordinators: process the information received from receptors
o Effectors: a muscle or gland that brings a response to bring conditions in the body
back to optimum levels
NERVOUS SYSTEM
Uses electrical impulses to enable you to react quickly to your surroundings and coordinate
your behaviour
PROCESS
o Receptors detect stimuli
o Impulses from receptors pass along the sensory neurones to the brain or spinal cord
o Brain coordinates response and impulses are sent along motor neurones from the
brain to the effector organs
o Effectors carry out a response
SYNAPSE: the junction between 2 neurones
o Electrical impulse arrives at the synapse
o Chemicals are released from the first neurone
o The chemical diffuses across the synapse
o The chemical attaches to the next neurone
o An impulse is triggered in the next neurone
THE REFLEX ARC
o Reflex actions are responses that are automatic, extremely quick and protect the
body
o Bypasses brain processing so the response is much quicker
o Mediated by the spinal cord
o PROCESS:
, The finger comes into contact with a flame
Pain receptors in the skin cause the impulse to be transmitted through the
sensory neurone
Impulses reach the spinal column and an effector response is sent to
muscles through motor neurones
Muscles in the arm/hand move the finger out of the flame
CONTROL OF BLOOD GLUCOSE
If glucose levels are too high, water leaves cells by osmosis; if the glucose levels are too low,
there is not enough for respiration
Blood glucose levels lower during exercise due to increased respiration
WHEN BLOOD GLUCOSE LEVELS ARE TOO HIGH:
o Insulin is released by the pancreas
o Insulin tells the liver to take glucose out of the blood, turn it into glycogen and store
it
o Blood glucose levels return to normal
WHEN BLOOD GLUCOSE LEVELS ARE TOO LOW:
o Glucagon is released by the pancreas and insulin stops being released
o Glucagon tells the liver to break glycogen into glucose and release it into the blood
o Blood glucose levels return to normal
DIABETES
o Type 1:
The pancreas cannot produce enough insulin
Treated with insulin injections
o Type 2:
Body cells no longer respond to insulin
Obesity and age are risk factors
Treatments include exercise and reducing simple carbohydrates
ENDOCHRINE SYSTEM
Hormone: a chemical released by an endochrine gland that travels through the blood to the
receptor of a target cell
The endochrine system is made up of glands that secret hormones directly into the
bloodstream
PITUITARY GLAND
o Master gland
o Stimulates other glands to release hormones
PANCREAS
o Secretes insulin
o Controls blood glucose levels
THYROID
o Secretes thyroxine
