U4: Homeostasis
L1: Human Body Systems and Homeostasis
What is Homeostasis?
-
tendency for the body to maintain a relatively constant internal environment.
-
target values are not exact, but rather ranges.
-
body systems (ie, nervous system, endocrine system) help maintain homeostasis.
SBI4U
ie - blood sugar ¬ 70 -140 mg/dl
-blood pH-> 7.35-7.45
-body temp ¬36.5 - 37.5 oc
Feedback Systems
monitors, assesses, and adjust internal conditions to
within acceptable ranges
3 components
- sensor: detects changes in the internal environment
-control center: receiving info from sensor, comparing it to acceptable range
- effector: receives signal from control center to cause change in the internal environment.
two types of feedback:
Negative feedback system
-ie, reprimanding a child.
-body works to reduce a change in a variable to an acceptable range.
-ie, body temp.
U4: Homeostasis
L1: Human Body Systems and Homeostasis
Positive Feedback System
- ie, praising a child/ pet for good behavior
-effectour working to strengthen/ increase a change in a variable.
-ie, child birth, blood clotting.
Check Your Understanding
1. Identify a, b, and c in the diagram to the right.
a) A is sensor. B is control centre. C is effector.
SBI4U
U4: Homeostasis
L1: Human Body Systems and Homeostasis
SBI4U
2. Human growth hormone (hGH) helps to regulate blood glucose levels. If low blood glucose levels are detected,
the brain stimulates the pituitary glan2d to secrete hGH. Human growth hormone travels through the blood to
the liver where it stimulates the liver to convert glycogen to glucose, which is released into the bloodstream
raising blood sugar levels. Using a diagram resembling the seesaw model in to the right, illustrate the negative
feedback loop described above.
a) Human growth hormone (hGH) aids in blood glucose control. The brain encourages the pituitary gland to
release hGH when low blood glucose levels are sensed. Human growth hormone travels through the
bloodstream to the liver, where it encourages the liver to convert glycogen to glucose, which then enters the
bloodstream and raises blood sugar levels. Demonstrate the negative feedback loop stated above using a
diagram similar to the seesaw model to the right.
3. When you get sick, your body causes your internal temperature to increase, and you develop a fever. Past 45oC,
death may occur as proteins in the brain and body begin to denature. Is fever an example of a positive, or
negative feedback loop? Explain.
a)Fever is an example of a negative feedback loop. Past 45°C is above the average body temperature.
4. The diagram below shows the range in which body temperature is maintained by homeostasis.
a. Identify what type of homeostatic feedback system is
working between points A and C on this graph.
Explain your answer.
b. Identify what type of homeostatic feedback system is
working between points C and D on this graph.
Explain your answer.
c. Infer what occurred between points D and E on the
graph during which body temperature returned to
normal.
a)Negative feedback is exemplified through the workout method. Our bodies aim to maintain a healthy balance of
blood pressure, heart rate, and body temperature, and they use a cooling system to do it. a.k.a. sweat
b)Because it interacts with stimulation, an infection is an example of positive feedback. An infection or a bodily
injury are two instances.
c)The body is reverting to its normal state and assisting the abnormality in the internal environment.
U4: Homeostasis
L1: Human Body Systems and Homeostasis
SBI4U