Module 1: Physiology Flashcards
What is physiology?
Physiology is the study of function in living organisms. It explores the mechanisms by which the organisms control their internal environments regardless of what happens in the outside (or external) environment. Physiology also attempts to explain the physical and chemical factors responsible for both normal function and disease (also called pathology).
What is our internal environement?
The internal environment is the fluid in which the cells of our body are bathed. This essentially consists of the interstitial fluid and blood plasma (the extracellular fluid compartments).
What is our external environment?
The external environment is the region outside of the body. The external environment also includes the space and contents of the digestive, respiratory, and urogenital tracts.
What is homeostasis and how is it maintained?
Homeostasis is defined as the maintenance of relatively stable conditions within the internal environment, regardless of what is happening in the external environment. This includes maintaining a relatively constant body temperature, water balance, salt concentration, etc. The body maintains homeostasis using negative and positive feedback control mechanisms.
What are the components of a negative feedback system?
They contain a set point, a control center (integrator), an effector, a controlled variable, and a sensor (receptor). The controlled variable which is detected by the sensor will shut off its own production by the effector.
How does negative feedback work when body temperature rises above normal?
When body temperature rises above normal, the nervous system signals blood vessels in the skin to dilate and sweat glands to secrete sweat. Body heat is lost to the surroundings and body temperature returns towards normal (37 degrees).
- Set point: 37 degrees Celsius
- Sensors: sensors in the nervous system
- Control center: sensors send signals to the hypothalamus
- Effector: organs and other systems activated by the hypothalamus
- Controlled variable: heat
How does negative feedback work when body temperature drops below normal?
When body temperature drops below normal, the nervous system signals blood vessels in the skin to constrict and sweat glands to remain inactive. If body temperature continues to drop, then the nervous system will signal muscles to contract involuntarily. Muscle activity generates body heat and body heat is conserved by the constricted blood vessels. Body temperature will rise toward normal (37 degrees).
- Set point: 37 degrees Celsius
- Sensors: sensors in the nervous system
- Control center: sensors send signals to the hypothalamus
- Effector: organs and other systems activated by the hypothalamus
- Controlled variable: heat
What is a positive feedback control system?
It is a self-amplifying mechanism that can produce a very rapid change in a physiological system, where the controlled variable stimulates its own production. The controlled variable is detected by the sensor that signals the control center to activate the effector to produce more of the controlled variable.
Examples:
- Generation of action potentials in nerve cells
- Surge of luteinizing hormone that causes ovulation of the egg from the ovary
What systems of the body do feedback mechanisms rely on?
The nervous system and the endocrine system.
- The nervous system (brain, spinal cord, and all of the nerves) is especially adapted for rapid communication through its complex system of neurons and nerves.
- The endocrine system responds more slowly, communicating by the release and distribution of hormones in the blood.
What is the structural hierarchy of matter in the body?
Atoms < Molecules < Macromolecules < Cellular Organelles (nucleus, cell membrane, proteins, etc.) < Cells < Tissue (groups of cells with the same specialization) < Organ (two or more types of tissues combined into a functional unit) < Organ System < Organism
