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Ch. 1


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internal environment
fluid that surrounds the cells inside the body, including fluid in the bloodstream that surrounds blood cells; synonymous with extracellular fluid
In GI tract, the water, inorganic salts, and nutrients obtained from digested food are transported from the lumen to the bloodstream
in aid of digestion of food, the stomach uses materials from the blood to produce acids and proteins that are then transported into the lumen.
Happens in kidneys
fluid from bloodstream enters tubules.
fluid travel along tubules, and needed materials (H2O, inorganic salts, and nutrients) are selectively transported back into the bloodstream.
fluid that reaches the end of the tubules make up the urine which elminated from body.
What's the most abdundant substance in the body?

acts as a solvent w/solutes.
inorganic ions
amino acids
Large molecules (proteins)
cell membranes
ICF and ECF are separated by ____ _______.
proteins and potassium
Fluid outside cells
maintenance of CONSTANT conditions in the internal environment
Total body water (TBW)
the total volume of fluid enclosed within the outer epithelial layer. Includes water that is found inside cells (ICF) and outside cells (ECF).
Intracellular fluid (ICF)
fluid inside cells
in blood
noncellular part of the blood
rich in proteins
Interstitial fluid (ISF)
The portion that is present OUTSIDE the blood and that bathes most of the cells in the body
few proteins
smallest and most numerous blood vessels
highly permeable to most solutes except proteins.
Homeostatic regulatory mechanisms
mechanism works to resist changes in the internal environment
has it's limitations even when it's undamaged by disease or trauma and is functioning normally.
Negative Feedback
Homeostatic regulatory mechanisms follow same pattern
if regulated variable increases, the system responds by making it decrease.
if it decrease, it responds to make it increase
work to resist changes in the internal environment
Regulated variable
something that must stay within narrow limits.
ex. Body temp., Potassium, sodium, and calcium.
kept constant by homeostatic regulatory mechanisms
Set point
Homeostatic regulatory mechanisms that make adjustments only when they DETECT a difference btwn. the actual value of the regulated variable and the normal "desired" value.
Error signal
Any difference btwn. the actual value and the set point sets off an _____ ______.
cells that are sensitive to the variable in question.
This is the way that Homeostatic regulatory mechanisms can detect regulated variable.
sensitive to concentrations of oxygen and carbon dioxide in the blood
sensitive to temperature
Integrating center
often a particular set of neural circuits in the brain
compares the regulated variable variable to the set point and plans the right response
Sensors relay signal to integrating center
Integrating center relays signals to the cells, tissues, or organs that bring about the final response.
Thermoregulatory center
the region responsible for temp. regulation
Positive feedback
the response of the system goes in the same direction as the change that sets it in motion.
LH surge
triggers ovulation
utilization of feedback mechanisms to maintain normal body temp.
Prolonged exposure to very cold temps can cause body temp to fall below the set point
overextertion or exposure to very high environmental temps can cause body temp to rise above the set point.
humans and other mammals are less affected by changes in the ambient temp because they have the ability to maintain their body temp within a fairly narrow range
animals and mammals who are not homeothermic.
heat loss mechanisms
transfer of thermal energy in the form of electromagnetic waves
when object is warmer than its surroundings, it absorbs and loses heat
if an object is cooler than it surroundings, it absorbs more energy than it emits and gains heat.
ex. heat from fire
transfer of thermal energy btwn. objects that are in direct contact with each other.
touching something cold can make you feel cold
the process that converts it from liquid form to gaseous form absorbs thermal energy.
ex. takes place on skin, in lungs and mouth
more water evaporates which carries away more thermal energy.
Insensible water loss
happens in skin, lungs, and mouth on a continual basis without your being aware of it.
a salt-containing solution secreted by numerous small sweat glands in the skin.
the transfer of heat from one place to another by moving gas or liquid, contributes to heat loss on a windy day.
under still conditions, the air that is closer to your skin warm up due to the absorption of heat from the body's surface (forms a "blanket" around body)
warmer air slows down heat loss
when windy the "blanket" is reduced which leads to heat loss
a region located in the base of the brain just above the pit. gland.
central thermoreceptors
send input to brain center (brain, spinal cord) and monitor the temp. from inside body (core temp.)
Core temperature
temp deep within the body
Peripheral receptors
located in the skin whose temp is usually well below core temp and is more variable.
enables us to sense the temp of the environment
effectors that vary the rate of heat production or loss
sweat glands
blood vessels in skin
skeletal muscle
sweat glands
control evaporative heat loss increasing or decreasing sweat production
Blood vessels in the skin
which control conductive and radiative heat lossby increasing or decreasing blood flow to the skin
skeletal muscle
which control heat production through shivering
rapid bursts of involuntary contractions that generate heat as a metabolic by product
thermoneutral zone
outside temp is within a narrow range (25 to 30 C)
blood flow to skin can make normal adjustments till core temp is normal
thermoregulatory centers
When core temps change ________ ______ send signals to effectors.
Negative feedback response to core temperature
1. Decrease sweat production
2. Decrease blood flow to skin
3. Stimulate shivering
elevation of body temp usually during illness. Not from failure of thermoregulatory system. Set points not being reset cause fever.
bacterial & viral infections stimulate WBC's to proliferate chemical substances which rise set point, and act as pyrogens.
↑ muscle activity used to ↑ body temp
↑ evaporative cooling to ↓ body temp
fever inducers

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