PHYS20008 Lecture Notes - Lecture 2: Osmotic Concentration, Homeostasis, Extracellular Fluid
12 Jun 2018
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Lecture 2
PHYS20008 - HUMAN PHYSIOLOGY
LECTURE 2
HOMEOSTASIS
HOMEOSTASIS
•Founding principle of physiology, will come back to
every single lecture.
•Homeostasis is the maintenance of a relatively
constant internal environment, of a biological entity.
•Thus the ‘relatively’, as we are biological entities and
cannot be perfect; usually operate within ranges. Our
bodies are always changing and we are always trying
to maintain changes.
•We need a stable internal environment in order for
cells to survive as they operate within certain ranges
including temperature, acidity, oxygen levels, pH etc.
•Basically, things change and our body changes to
compensate so that things remain stable.
HOMEOSTATIC PROCESSES
•Detect changes
•Sensor
•Message to integrator
•Afferent
•Controller or integrator
•Compare to set point 100mm
mercury
•Message to effector
•Efferent
•RESPONSE
•Return to within desired range
•=> negative feedback
INTEGRATION
•Negative feedback
•Constant monitoring and adjustment
•If something moves out of its ideal range, we bring it back into its ideal range. Something
needs to move in the opposite direction to correct a change.
•Integration involves:
•Endocrine: hormones
•Neural
•In order to respond to hormones, cells need receptors. So different cells have unique
receptors in order to receive certain neural signals; not any cell can receive neural signals.
We are always monitoring
things and our integrating
centre and output are making
fine adjustments all the time.
Lecture 2
PHYS20008 - HUMAN PHYSIOLOGY
Document Summary
We are always monitoring things and our integrating centre and output are making fine adjustments all the time. Homeostatic processes: detect changes, sensor, message to integrator, afferent, controller or integrator, compare to set point 100mm mercury, message to effector, efferent, response, return to within desired range, => negative feedback. Integration: negative feedback, constant monitoring and, if something moves out of its ideal range, we bring it back into its ideal range. Something adjustment needs to move in the opposite direction to correct a change: integration involves, endocrine: hormones, neural, in order to respond to hormones, cells need receptors. So different cells have unique receptors in order to receive certain neural signals; not any cell can receive neural signals. Positive feedback: positive feedback reinforces the stimulus and escalates the response. There are a few examples in the human body of positive feedback loops but not many: eg. Blood clotting, ovulation, pushing against cervix during pregnancy, na channels in action potential.
