Download Homeostasis - HHS-Biology-3C

Unit 3: Vertebrate Body Systems
• We have looked at the digestive system
• We are going to study at two other systems:
– Circulatory and Respiratory
• Why are we studying these systems?
• These systems all help to keep us alive by
keeping balance within our body.
• Without balance we would
• become ill and possibly die
Homeostasis
• from Greek: ὅμοιος, hómoios, "similar"; and
στάσις, stásis, "standing still"
• The maintenance of a steady internal
environment despite changes in the external
environment
• Example: Human body temperature stays close
to 37 degrees C despite outside temperature
varying from -40 to +40
• Heart rate: 50 -100 beats/min
• Breathing rate: 16-20 breaths/min
• Blood pH: 7.35-7.45
Fishbowl Model of the Human Body
Function
Fishbowl
Human Body
Water
Body fluid
Glass bowl
Skin
Barrier (internal vs. external)
Fish
Cells
Stay alive
Air pump
Lungs
Keep O2 level constant (high)
Filter
Kidneys
Keep nitrogen wastes constant (low)
Heater
Muscles
Keep temperature constant (high)
Feeder
Internal environment
Digestive system Keep nutrient levels contant (high)
Everything working together Relatively constant conditions
• As with the fish bowl the organs/organ systems
of the human body work together to maintain
homeostasis
How is Homeostasis Maintained?
• Negative feedback
mechanisms return
system to the
“normal” levels if they
get out of balance
• A thermostat is an
example of a negative
feedback loop
Human Body Temperature 1
• Maintain your core
temperature
Too Hot?
• Sweat evaporates to
cool you down
• Seek shade
• Go swimming
Human Body Temperature 2
Too COLD?
• Muscles contract
rapidly (shiver)
• Put on more clothing
• Get into the sun or go
inside
Two Parts to Homeostasis
Things you do:
• Go inside
• Put on more clothes
• Find shade
• Eat, drink
• Put on sunglasses
Things your body does:
• Shiver
• Increase heart rate
• Feeling of hunger
• Sweat
• Constrict pupils
These are BEHAVIOURAL These are PHYSIOLOGICAL
responses
responses
Two Main Body Systems Involved
Nervous System
Central Nervous
System = Brain and
Spinal Cord
Periferal Nervous
System = Sensory
and Motor Neurons
(nerve cells)
Reflex Arc
Endocrine System
Endocrine System
• Consists of:
Glands, hormones
and target organs
e.g.: Pituitary gland
secretes HGH
(growth hormone)
which acts on most
cells in the body
A Simple Demonstation
• When we exercise our muscle cells need
more oxygen
• How does the body accomplish this?
• While sitting at your desk take your pulse
and record it.
• Record your resting breathing rate
• Walk down to the basement and then run
up the stairs. Take your pulse and
breathing rate again. Record the values.
Observation Chart
Resting
Pulse
(Beats/min)
Breathing
(Breaths/min)
After
Moderate
Exercise
Discussion
1. Explain your observations.
2. What would happen to the breathing rate
and heartbeat if you exercised vigorously
or longer?
3. What happened to both rates after a few
minutes of rest? Why