Physiology 2130 Study Guide - Fall 2018, Comprehensive Midterm Notes - Homeostasis, Extracellular Fluid, Cell Membrane
12 Oct 2018
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Physiology 2130
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Module 1 – Introduction to Human Physiology
Introduction
• Physiology: study of function in living organisms
o Explores how organisms control their internal environments regardless of what
happens in the external environment
o Explains physical and chemical factors responsible for both normal function and
disease
Homeostasis
• Internal environment: fluid in which the cells of our body are bathed
o Consists of interstitial fluid and blood plasma
• External environment: region outside the body
o Space and contents of the digestive, respiratory and urogenital tracts
• Homeostasis: maintenance of relatively stable conditions within the internal environment
regardless of what is happening in the external environment
o Body maintains internal environment so that cells can function regardless of
external environment
o Maintains through negative and positive feedback
Negative Feedback Control Systems
• All negative feedback control systems operate the same way to maintain homeostasis from
maintaining body temperatures to body fluid volumes
• They contain:
o Set point
o Control center (integrator)
o Effector
o Controlled variable
o Sensor (receptor)
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• Negative feedback and body temperature:
o Set point for body temperature is 37 degrees Celsius but it could drop
o Sensors in the nervous system detect the change in temperature and signal a control
center in the brain (hypothalamus)
o Control centers notices a difference between the set point and the actual value
o Control center activates organs and systems (the effector) to generate heat (the
controlled variable) by shivering and conserving heat by decreasing blood flow to
the skin
o When body temperature is restored, the control center would stop the shivering and
return the blood flow to the extremities
o Opposite happens if body temperature increases above the set point
▪ Sensors detect rise in temperature and signal the hypothalamus and the
hypothalamus utilizes the nervous system and signals blood vessels in the
skin to dilate and sweat glands to sweat
▪ Heat dissipates and body temperature would be normal
• Negative feedback: the controlled variable eventually shuts off its own production
Positive Feedback Control Systems
• Mechanism where the controlled variable actually stimulates its own production
o Self-amplifying mechanisms that can product a rapid change
• Controlled variable is detected by the sensor that signals the control center to activate the
effector to produce more of the controlled variable
o Large amounts of controlled variable are produced
find more resources at oneclass.com
find more resources at oneclass.com
