1. homeostasis

Question 1

what is physiology

Answer 1

study of how the body functions

Question 2

what is homeostasis

Answer 2

the ability to maintain relatively stable conditions in the internal environment (despite changes in external environment)
*cells can only survive within a narrow range of conditions, therefore body conditions must be maintained within physiological limits

Question 3

homeostasis conditions controlled include

Answer 3

1) pH
2) temperature
3) blood gases (CO2, O2)
4) blood pressure (b.p.)
5) intracellular + extracellular (ICF +ECF) fluid volumes
6) etc.

Question 4

what functions together to maintain homeostasis

Answer 4

organ systems

Question 5

disease =

Answer 5

the failure to maintain homeostasis

Question 6

nervous and endocrine systems control all other systems (control centers): act to:

Answer 6

1) maintain homeostasis
2) permit departures from homeostasis in a controlled manner
* eg. pregnancy, growth, sudden fright

Question 7

homeostasis regulation

Answer 7

change in internal environment must be detected or anticipated
*the NS and or endocrine respond alternating systems responsible for that condition

Question 8

Types of endocrine resposonses

Answer 8

1) anticipatory responses

2) feedback mechanisms

Question 9

anticipatory responses

Answer 9

*e.g. ⇑ respiratory rate at start of exercise ⇒ proprioceptors (NS sensory
receptors) signal movement before a change in internal conditions (gases
in blood)
* may also be learned or behavioral
(e.g. put on coat)

Question 10

feedback mechanisms

Answer 10

• mechanisms that respond to change in system
• consist of set points, receptors, control areas, and effectors
• Set point = range of values of a variable (e.g. body temp.) that do not bring
  about a response (i.e. “normal range”)
• Variable is monitored by receptors ⇒ info (input) fed back to control area (NS/endocrine gland) ⇒ controls the effector (output)

Question 11

types of feedback mechanisms

Answer 11

negative feedback

positive feedback

Question 12

Negative Feedback

Answer 12

• Most common homeostatic control mechanism
• Result of “output” W variable moves back toward the set
  point i.e. in opposite (negative) direction to the change that
  triggered the response (“input”)
• e.g. #1: body temp. (= variable) set point 36 to 37.8 oC. If ⇑
  temp (e.g. 40 oC):
• Result = core blood to skin surface and sweat evaporates = ⇑ heat loss & ⇓ temp (opposite direction of input)
• e.g. #2: ⇓ temp -> shiver -> ⇑ temp
  *set point can change e.g fever

Question 13

positive feedback

Answer 13

• Less common W NOT homeostatic ! Output intensifies the input
• e.g. Childbirth – labour
• check notes for diagrams
• — *continues until endpoint (=baby born)