Homeostasis Flashcards
Define Homeostasis
maintaining relatively constant conditions despite constant changes in the external environment
Define auto regulation
- the automatic response in a cell, tissue or organ to some environmental change
Define Extrinsic regulation
Responses controlled by nervous & endocrine systems
What are the 3 components of homeostasis ?
- receptors
- control centres
- effectors
What are some biological variables involved in homeostasis ?
- body temp
- body fluid composition & volume
- blood pressure
Define the Set Point
- designated value/range of a biological variable
What is the set point for body temp?
37 degrees
What is the set point for blood glucose levels ?
4.0 - 5.9 mmol/L
What is the set point for potassium levels?
3.6 - 5.2 mmol/L
Describe receptors
- body structure that monitors changes in a controlled condition
- sends input to a control centre
Describe Control Centres
- example = Brain
- sets the set points for a controlled condition
- evaluates received input & generates output commands when necessary
What do output commands typically occur as ?
- hormones or nerve impulses
Describe Effectors
- body structure that receives output from control centre
- produces a response/effect that changes the controlled condition
Define Positive Feedback
- body is moved away from homeostasis
- used to speed processes
- response of the effector increases change of the stimulus
Define Negative Feedback
- response of effector negates the stimuli
- body is brought back into homeostasis
What can you expect increased levels of in Graves’ disease ?
- T3 (triiodothyronine)
- T4 (thyroxine)
- persistent TSHr stimulation
Describe characteristics of Graves’ disease
- hyperthyroidism
- exophthalmos (bulging eyes)
- diffuse goiter (enlarged thyroid)
-Abs to TSHr - heat intolerance & anxiety
What will you see decreased levels of in Graves’ disease ?
- TRH/ TSH
What are some treatments for Graves’ disease?
- thyroidectomy
- anti-thyroid drugs (carbimazole)
- Radioiodine-131
