BISC 101 Chapter Notes -Childbirth, Fluid Compartments, Systemic Disease

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Published on 8 Oct 2012
School
Simon Fraser University
Department
Biological Sciences
Course
BISC 101
Professor
Week 4 Homeostasis 1
Homeostasis the condition of equilibrium in the body’s internal environment due to the constant interaction of
the body’s many regulatory processes
The body’s equilibrium shifts among points in the narrow range that is required to maintain life
Example: blood glucose level normally stays between 70 to 110 mg of glucose per 100 mL of blood
Every structure contributes in some way to homeostasis
Homeostasis and Body Fluids
Maintain composition and volume of body fluids is important for homeostasis.
Body fluids dilute, watery solutions containing dissolved chemicals found inside and outside cells
Proper functioning of body cells depends on the regulation of ISF around them.
Interstitial fluid “body’s internal environment”
Composition of ISF changes as substances move back and forth between it and plasma
o Occurs in the smallest blood vessels blood capillaries
o Provides needed materials (like glucose, O2, ions, etc) to tissue cells
o Removes wastes like CO2 from ISF
Body fluids - dilute,
watery solutions
containing dissolved
chemicals that are found
inside and outside of cells
Extracellular fluid (ECF) -
fluid outside cells
Interstitial fluid (ISF) - ECF
that fills narrow spaces
between cells of tissues
ECF differs depending on
where it is in the body.
Plasma, CSF, synovial fluid,
aquaous humor, vitreous
body, etc
Intracellular fluid (ICF) -
fluid within cells
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Week 4 Homeostasis 2
Control of Homeostasis
Homeostasis is continually disturbed.
o External environment (physical insults) intense heat, lack of oxygen
o Internal environment low blood glucose level
o Psychological stresses from our social environment demands of work and school
Most disruptions are mild/temporary, and body cells quickly restore balance in the internal environment.
Some disruptions are intense/prolonged (like overexposure to temperature extremes, a severe infection,
or major surgery)
The nervous system and endocrine system are the “regular” systems used in homeostasis, whether they work
together or independently.
Nervous system sends nerve impulses (action potentials) to organs that counteract changes
o Rapid changes
Endocrine system includes glands that secrete hormones into the blood
o Slower changes
Both means work toward the same end, usually through negative feedback systems.
Feedback Systems a cycle of events in which the status of a body condition is monitored, evaluated,
changed, remonitored, reevaluated, and so on.
Each monitored variable (like blood pressure or body temperature) = controlled condition
Disruption that changes a controlled condition = stimulus
A feedback loop consists of a receptor, a control center, and an effector
Stimulus
disrupts
homeostasis by
increasing or
decreasing a...
Controlled
condition or
variable that is
monitored by...
Receptors that
send an INPUT
(AP/hormones)
to...
The control
center that
provides an
OUTPUT
(AP/hormones)
Effectors are
body structures
that bring about
a response that
alters the
controlled
condition
HOMEOSTASIS
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Document Summary

Homeostasis the condition of equilibrium in the body"s internal environment due to the constant interaction of the body"s many regulatory processes. The body"s equilibrium shifts among points in the narrow range that is required to maintain life. Example: blood glucose level normally stays between 70 to 110 mg of glucose per 100 ml of blood. Every structure contributes in some way to homeostasis. Maintain composition and volume of body fluids is important for homeostasis. Body fluids dilute, watery solutions containing dissolved chemicals found inside and outside cells. Body fluids - dilute, watery solutions containing dissolved chemicals that are found inside and outside of cells. Interstitial fluid (isf) - ecf that fills narrow spaces between cells of tissues. Ecf differs depending on where it is in the body. Plasma, csf, synovial fluid, aquaous humor, vitreous body, etc. Proper functioning of body cells depends on the regulation of isf around them.

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