Control of the Body’s Systems
A basic characteristic of all living organisms is their ability to respond to changes in
their internal and external environments. The term homeostasis is used to describe the
maintenance of a healthy balance of chemical reactions in an organism. The term
homeostasis is derived from two Greek words, homoios, meaning “same” and stasis,
meaning, “standing still”.
When a change in the environment upsets the state of balance, the body will sense the
change and respond by trying to re-establish the “normal levels”. This system of balance
requires constant monitoring and feedback about body conditions. Since people vary in
age, gender, genetic make-up, fitness and lifestyle “normal levels” will be different
from individual to individual.
What conditions or substances must remain constant in the body?
1.
2.
3.
4.
5.
6.
7.
Body Temperature
pH
Water levels
Oxygen/CO2 levels
Nutrient levels – macromolecules, vitamins and minerals
Electrolytes (dissolved ions)
Wastes/toxins
In response to a change in the body’s conditions, a process known as a feedback loop is
initiated:
Stimulus
 Sensory receptors
 Integrator
 Effector
 Response
Stimulus – any change in environmental conditions that is detected by your body
Sensory receptor – cells, tissues and/or organs that monitor internal conditions
Integrator – area that receives messages from the sensors and sends signals to the
effectors; typically the brain
Effector –
area that makes changes to the body’s varying condition; typically muscles,
an organ or a gland
An example of a typical feedback loop involves the control of body temperature
(thermoregulation).
There are two systems of the body that act together to maintain homeostasis:
1.
Nervous System (fast communication)
Electrical messages (high speed nerve impulses) are conveyed along nerve cells
(neurons).
2.
Endocrine System (slow communication)
Chemical messengers (hormones) are proteins that are typically secreted by glands
and are transported through the bloodstream to target areas.
Blood-sugar levels are controlled by two hormones, insulin and glucagon, that are
secreted by the pancreas.
Following a meal:
 Blood-sugar levels will begin to rise
 Stimulates receptors in the pancreas
to release insulin
 Insulin helps glucose (carbohydrate),
obtained from the food we eat, get
into our cells to undergo respiration
and manufacture energy (ATP)
 Excess glucose is converted into
glycogen and stored in the liver
After long periods without food:
 Blood-sugar levels decrease
 Stimulates receptors in the pancreas
to release glucagon
 Glucagon converts glycogen in the liver to glucose
 Blood-sugar levels will rise
Diabetes is a disorder that occurs when blood-sugar levels cannot be controlled. There
are two types of diabetes, Type 1 (insulin-dependent) diabetes and Type 2 (non-insulindependent) diabetes.
Type 1 Diabetes (insulin dependent)
 Also called juvenile diabetes
 Cause not well understood
 Evidence shows that it may be caused by an autoimmune disorder
 The immune system attacks the pancreas because it no longer recognizes the
cells of the pancreas as being "self"
 Immune system attacks insulin producing beta cells
 The body may lose its ability to produce insulin overnight
Type 2 Diabetes (non-insulin-diabetes)
 More common (almost 90% of cases)
 Adult onset diabetes (occurs in adults over the age of 40)
 The body produces insulin but in insufficient quantities and or the body cells
neither recognize or respond to the insulin
 Treated by means of changes in diet or exercise
 Patients may require medication or even insulin shots to control increased bloodsugar levels
Control of the Body’s Systems
A basic characteristic of all living organisms is their ability to _________ to changes in
their ______ and ______ environments. The term homeostasis is used to describe the
maintenance of a healthy balance of ___________________ in an organism. The term
homeostasis is derived from two Greek words, homoios, meaning “_______” and stasis,
meaning, “_______________”.
When a change in the environment upsets the state of balance, the body will _____ the
change and _____ by trying to re-establish the “__________”. This system of balance
requires constant ________ and ________ about body conditions. Since people vary in
___, _____, _______________, ______ and ______ “normal levels” will be different
from individual to individual.
What conditions or substances must remain constant in the body?
1.
2.
3.
4.
5.
6.
7.
In response to a change in the body’s conditions, a process known as a feedback loop is
initiated:




Stimulus –
Sensory receptor –
Integrator –
Effector –
An example of a typical feedback loop involves the control of body temperature
(____________________).
There are two systems of the body that act together to maintain homeostasis:
1.
_________________ (fast communication)
Electrical messages (high speed nerve impulses) are conveyed along nerve cells
(neurons).
2.
_________________ (slow communication)
Chemical messengers (hormones) are proteins that are typically secreted by glands
and are transported through the bloodstream to target areas.
Blood-sugar levels are controlled by two hormones, ________ and _________, that are
secreted by the _____________.
Following a meal:
 Blood-sugar levels will begin to _____
 Stimulates receptors in the pancreas
to release _______
 Insulin helps ______ (carbohydrate),
obtained from the food we eat, get
into our _____ to undergo ________
and manufacture _________ (ATP)
 Excess glucose is converted into
_________ and stored in the _____
After long periods without food:
 Blood-sugar levels ___________
 Stimulates receptors in the pancreas
to release ____________
 Glucagon converts __________ in the liver to ____________
 Blood-sugar levels will _______
Diabetes is a disorder that occurs when blood-sugar levels cannot be controlled. There
are two types of diabetes, Type 1 (insulin-dependent) diabetes and Type 2 (non-insulindependent) diabetes.
Type 1 Diabetes (insulin dependent)
 Also called ______________________
 Cause not well understood
 Evidence shows that it may be caused by an ________________ disorder
 The immune system attacks the __________ because it no longer recognizes the
cells of the pancreas as being "_______"
 Immune system attacks insulin producing ______ cells
 The body may lose its ability to produce insulin _________________
Type 2 Diabetes (non-insulin-diabetes)
 More common (almost _____ of cases)
 _____________ diabetes (occurs in adults over the age of ___)
 The body produces insulin but in ____________ quantities and or the body cells
neither __________ or ___________ to the insulin
 Treated by means of changes in _____ or _____________
 Patients may require medication or even _____________ to control increased
blood-sugar levels