1 - Homeostasis Flashcards
What is physiology?
study of how the body functions and maintains homeostasis
What is homeostasis?
maintenance of relatively constant internal environment
What are the 7 optimal conditions that cells in our body must meet?
- Temperature
- pH
- CO2
- O2
- Blood pressure
- Concentration of ions (Na+, Cl-, etc) and volumes of fluid (inside and outside cell)
- Waste levels
What results when homeostasis is not maintained?
disease
What 2 systems function together to control all of the other body systems?
- Nervous system
- Endocrine system
What do the nervous + endocrine function together to do?
- maintain homeostais
- permit **controlled departure from homeostasis
What are examples of the nervous + endocrine system permitting departure from homeostasis in a controlled fashion?
- Pregnancy
- Blood clotting
- Growth
- Response to danger
What are two ways responses can occur in homeostasis?
- subconscious
- conscious
subconscious or conscious response to homeostasis: changes to heart rate or rest. rate at start of a sprint
*subconscious:
- proactive change that anticipates changes in blood gas levels that occur during exercise
subconscious or conscious response to homeostasis: putting on a hat before heading outside
*conscious:
- learned behaviour that occurs in response to change
- anticipates heat loss and change change in body temp
overall summary of feedback mechanism
stimulus (sensory info) > receptor (input) >** control center** (nervous + endocrine) > effector (output) > response (systems)
**
what type of feedback is the most common mechanism of homeostasis control?
negative feedback
what is negative feedback?
- output functions to **reduce the input, moving the variable back to set-point
- the opposite direction from that which triggered the response
- ** negative feedback helps keep things stable by reversing any changes that go too far in one direction.
what is an example of negative feedback?
**body temperature:
- set-point: 36-37.5°C
- high temp: 40°C
- detected by cells of hypothalamus
- sweat glands > effector that produce the CNS generated output (sweat)
- smooth muscle of blood vessels relax > inc. blood flow to body’s surface > heat escapes to atmosphere
- result: increased heat loss leading to drop in body temp back to set-point values
what type of feedback is not a homeostasis mechanism?
positive feedback
what is positive feedback?
- output acts to **intensify the stimuli rather than turn it down
what is an example of positive feedback?
**uterine contractions during childbirth:
- input: increased contractions
- posterior pituitary (nervous sys.)
- oxytocin release
- contractions increase further
