FUNDAMENTALS
OF PHYSIOLOGY
AND ANATOMY
4BBY1060
Epithelial & Muscular
Physiology & Anatomy
, LECTURE 3:
Important physiological variables
O2, CO2, pH, Blood Glucose, Osmomolarity (Na +, K+), Temperature
Homeostatic control: dynamic maintenance of physiological variables within a
predictable range. May fluctuate within a normal range but average will be
predictable.
- Short term -> Immediate survival
- Medium-long term -> Health and well-being, reproductive capability
Negative feedback: Change in variable is compared to a set point, causing a
response that brings it back to normal ranges. (Blood O 2 and CO2 content)
Different types include:
- Neuronal, usually involving the ANS (sympathetic and parasympathetic)
- Endocrine (hormonal)
- Local (chemical/physical)
When physiological circumstances change, set points may be overridden (Fever,
during exercise)
Feed-forward: Anticipation of a change brings about the response to that change
before the change can be detected by negative feedback sensors
Positive feedback: Change in a variable trigger a response that causes further
change in that variable (e.g., giving birth)
Consists of:
Sensors: detect changes in the physiological variable
Afferent Pathway: carry signals from sensors to integrating center
Integrating Centre: compares inputs from sensors against physiological
set-points and elicit a response
Efferent Pathway: carry signals from integrating centre to effectors
Effectors: produce a response that tends to normalize the physiological
variable
Hierarchy of importance: a variable that is of greater importance may be
maintained at the expense of other variables that are of importance at a longer
term.
Increased salt intake –> increased water intake –> plasma osmolarity
maintained at expense of higher MABP –> Hypertension
OF PHYSIOLOGY
AND ANATOMY
4BBY1060
Epithelial & Muscular
Physiology & Anatomy
, LECTURE 3:
Important physiological variables
O2, CO2, pH, Blood Glucose, Osmomolarity (Na +, K+), Temperature
Homeostatic control: dynamic maintenance of physiological variables within a
predictable range. May fluctuate within a normal range but average will be
predictable.
- Short term -> Immediate survival
- Medium-long term -> Health and well-being, reproductive capability
Negative feedback: Change in variable is compared to a set point, causing a
response that brings it back to normal ranges. (Blood O 2 and CO2 content)
Different types include:
- Neuronal, usually involving the ANS (sympathetic and parasympathetic)
- Endocrine (hormonal)
- Local (chemical/physical)
When physiological circumstances change, set points may be overridden (Fever,
during exercise)
Feed-forward: Anticipation of a change brings about the response to that change
before the change can be detected by negative feedback sensors
Positive feedback: Change in a variable trigger a response that causes further
change in that variable (e.g., giving birth)
Consists of:
Sensors: detect changes in the physiological variable
Afferent Pathway: carry signals from sensors to integrating center
Integrating Centre: compares inputs from sensors against physiological
set-points and elicit a response
Efferent Pathway: carry signals from integrating centre to effectors
Effectors: produce a response that tends to normalize the physiological
variable
Hierarchy of importance: a variable that is of greater importance may be
maintained at the expense of other variables that are of importance at a longer
term.
Increased salt intake –> increased water intake –> plasma osmolarity
maintained at expense of higher MABP –> Hypertension
