Download Homeostasis

Life Processes
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Metabolism
Responsiveness
Movement
Growth
Differentiation
Reproduction
Survival Needs
1. Appropriate body temperature
2. Atmospheric pressure
– Must be kept within a certain range for proper
breathing and cellular metabolism
3. Nutrients
– Needed for energy and building cells
4. Oxygen
– Required for the breakdown of nutrients
5. Water
Homeostasis
Ms Clark
PVMHS
Homeostasis
• The body’s ability to maintain relatively stable
internal conditions despite changes inside and
outside of the body
• Every body structure has one or more
homeostatic devices that works to keep the
internal environment within normal limits.
• Homeostatic mechanisms are mainly under
the control of the nervous system and the
endocrine system.
Homeostasis and the Nervous System
Detects changes from balanced state
Sends message in the form of nerve impulses to
organs that can counteract change
Organ reacts
Afferent vs Efferent
• AFFERENT neurons are responsible for
sending information about the stimulus
to the central nervous system
• EFFERENT neurons carry signals away
from the central nervous system in order
to initiate an action
Example
Body temperature rises above normal level
Nerve impulses cause sweat glands to release
more sweat
Body cools as sweat evaporates
Homeostasis and the Endocrine
System
Endocrine system corrects changes by secreting
hormones into the blood
Hormones target specific body cells where they
cause responses that restore homeostasis
Example
Blood glucose level is too high
The hormone insulin is secreted and reduces
blood glucose level
• Nerve impulses typically restore homeostasis
more rapidly than hormones
Feedback System
• A cycle of events in which the status of a body
condition is continually monitored, evaluated,
and changed.
• Each monitored condition is called a
controlled condition
– Ex: Body temperature, blood pressure, blood
glucose level
• Stimulus: any disruption that causes a change
in a controlled condition
– Ex: Extreme heat, lack of oxygen, low blood
glucose level
Components of a Feedback System
– Receptor
• Monitors changes, sends input to a control center
• Ex: temperature-sensing nerve endings in skin
– Control Center
• Sets the range of acceptable values for a body
condition, generates output to effector
• Ex: brain
– Effector
• Receives output and generates a response
• Ex: skeletal muscles
Types of Feedback Systems
• Negative Feedback System
– Reverses the original stimulus
• Ex: Restoring body temperature through production of
sweat
• Positive Feedback System
– Enhances or intensifies original stimulus
• Ex: Contractions during childbirth
• Ex: Blood clots
Negative Feedback System
Positive Feedback System
Homeostasis & Disease
• As long as homeostasis is maintained, the
body stays healthy
• If a component of the body loses its ability to
contribute to homeostasis, balance among all
body processes may be disturbed
• If homeostatic imbalance is moderate, a
disorder or disease may occur
• If it is severe, death may result.
Homeostasis & Disease
• Disorder
– Any abnormality of a function
– Ex: Heart disorder, OCD
• Disease
– An illness characterized by a recognizable set of
signs and symptoms
– Ex: Heart disease, flu
Diseases/Disorders
Acute: affects a person for a certain
amount of time; usually temporary
•Ex: heart attack
Chronic: remain for a long time and
can get worse; usually no cure
•Ex: atherosclerosis (heart disease)
• Symptoms
– Subjective changes in body functions that are not
apparent to an observer
– Ex: Headache, nausea
• Signs
– Objective changes that someone can observe and
measure
– Ex: Bleeding, swelling, fever, rash