Section 1

Question 1

describe homeostasis

Answer 1

• body has a “normal” setting at which it functions
• when external or internal forces influence this normal, the body can make a coordinated response to return to these optimal conditions

Question 2

what is set point?

Answer 2

the range or point at which a variable physiological state (e.g body temp) tends to stabilize

Question 3

what are the three components of most homeostatic control systems + their functions?

Answer 3

homeostasis —> change detected —>
- Sensor: responsible for detecting an environmental variable/change

— input sent via afferent pathway —>
- Integrator: compares the variable being detected to its set point

— output sent via efferent pathway —>
- Effector: responsible for initiating the changes to restore the variable back to the set point

— response to change, and imbalance corrected —> homeostasis

Question 4

what are the two types of homeostatic regulation?

Answer 4

• intrinsic regulation (aka local or autoregulation)
• extrinsic regulation

Question 5

define intrinsically controlled regulation:

Answer 5

• the sensor, integrator and effector are all located in the tissue so it can regulate its own internal environment
• e.g is exercising skeletal muscle; needs a lot of oxygen to produce ATP and when local oxygen concentration drops, the blood vessels in the muscle dilate/get bigger to increase the amount of oxygen that can be delivered

Question 6

define extrinsically controlled regulation:

Answer 6

• the regulatory mechanisms are outside of the tissue or organ
• e.g regulation of body temp
• majority of homeostatic control systems in the body are dependent upon extrinsic controls

Question 7

what is negative feedback?

Answer 7

a change in an environmental parameter, causing the effector to initiate a response in the opposite direction, restoring the parameter to the set point
- e.g blood glucose regulation with insulin (which lowers blood glucose and upregulates liver’s ability to convert glucose to store as glycogen)

Question 8

Name sensor, integrator, and effector in glucose regulation:

Answer 8

sensor: pancreatic cells, measure glucose level in blood

integrator: pancreatic cells

effector: liver (glucose uptake and conversion) and body cells (skeletal muscle, adipose tissue)

Question 9

what is positive feedback

Answer 9

occurs when the effector causes changes that amplify the initial signal

e.g decreased body temp: positive feedback loop would further decrease body temp, which would further activate the sensor

• positive feedback is NOT homeostatic

Question 10

give an example of positive feedback

Answer 10

Child birth:
- brain stimulates pituitary gland to secrete oxytocin
- oxytocin is carried through bloodstream to the uterus
- oxytocin stimulates uterine contractions which push the baby towards the cervix
- the head of baby pushes against cervix
- the nerve impulses from the cervix are transmitted to the brain
- repeat

Question 11

What is the level of control (intrinsic or extrinsic) and mechanism of control (neg or pos) of each of the following:

• Blood clotting
• Childbirth
• Regulation of blood pressure
• Regulation of blood-glucose levels

Answer 11

• Blood clotting (intrinsic, pos)
• Childbirth (extrinsic, pos)
• Regulation of blood pressure (intrinsic, neg)
• Regulation of blood-glucose levels (extrinsic, neg)