1. What would happen to me if I stuck my head in cold water??

2. Mammalian Dive Reflex Homeostatic Responses During:
Vasoconstriction in extremities to conserve heat
Decrease in heart rate
Blood flow returning to heart is increased
Kidneys release urine in effort to counter high blood volume in core

3. WHY ??
Optimizes respiration to allow staying underwater for extended periods of time.
It is exhibited strongly in aquatic mammals (seals, otters, dolphins, etc.), but exists in a weaker version in other mammals, including humans

4. What is a homeostatic response??
Homeostatic Responses After:
Vasodilation in extremities (face) to bring heat and oxygen back
Heart rate increases and re-sets rhythm
What is a homeostatic response??
Homeostasis – process by which a constant internal environment is maintained despite changes in the external environment

5. Poor old me, trying to get back in shape

6. All homeostatic control systems have:
Dynamic Equilibrium – condition that remains stable within fluctuating limits (homeostasis is a dynamic equilibrium)
All homeostatic control systems have:
Monitors and sensors
Coordinating centre
Regulator and effectors

7. Hire-wire Artist Model
Variable:
position of body
Setpoint:
directly over the wire
Monitors and Sensors:
nerve receptors (eyes, inner ears, muscle stretch receptors, etc.)
Regulator:
brain
Effectors:
skeletal muscles High-wire artist uses negative
feedback to maintain relatively
constant position on wire.

8. signal CHANGES in environmental temperatures
Heat and cold receptors, rather than detecting specific temperatures as does like a thermostat, are adapted to
signal CHANGES in environmental temperatures
Extension #1: Using this information, explain why you might feel a chill when you step out of a warm shower even though room temperature is comfortable
Extension #2: Using this information, explain why when a frog is placed in a beaker of water above 40°C, the frog will leap out immediately, but when the frog is placed in room-temperature water and the temperature is slowly elevated, the frog does not leap out

9. Negative Feedback Systems (common)
Bring system back to acceptable range
Prevents small internal adjustments from getting out of hand
Eg. When body temperature continues to drop, body begins to shiver to reverse the temperature (bring back to norm)
Blood glucose

10. Positive Feedback Systems (uncommon)
Amplify a small change, moves away from equilibrium
Allows a discrete event to happen rapidly
Eg. Lactation – suckling baby stimulates production of oxytocin, in turns causes contraction of milk duct muscles, causing milk flow… and flow of milk increases suckling

11. A reflex
A specific, involuntary, unpremeditated response to a particular stimulus.
A stimulus being a detectable change in the internal or external environment. The pathway meditating a reflex is called a reflex arc.

12. We will be examining 3 systems that help maintain homeostasis
The excretory system
The nervous system
The endocrine system

13. Excretory System Why do we really pee???
Average person consumes more protein than necessary
While most are converted to carbohydrates, the leftover nitrogen must be eliminated
Process is called deamination which produces urea - N2COH2
Kidneys play a crucial in:
Removing waste
Balancing blood pH
Maintaining water balance

14. Excretory System
Bladder
Sphincter at base allows storage of urine
When 200 ml is collected, bladder stretches which sends nerve message to the brain
600 ml or more – bladder relaxes and you urinate!
Urine is voided via the urethra

15. The nervous system
Neurons: Cells which can transmit nerve impulses in the form of electrochemical messages
The axon sends a wave of depolarization along its length
The wave of depolarization is primarily the movement of Na+ and K+ ions across the axon’s membrane

16. Endocrine system
The endocrine system is the system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body.
Endocrine hormones are produced in glands and are secreted into the bloodstream  find target cells