1. An Introduction to Anatomy and Physiology
Chapter 1 Homeostasis
Slides
1.13_C_Homeostasis-Intro (Slides 1-9)

2. INTRO
1.13_C_Homeostasis-Intro

3. Homeostatic Regulation
Ex: Household temperature control 1. Variable that is regulated 2. Receptor: monitors the variable (receives and transmits “stimulus”) 3. Control Center: integrates information and compares it to a “set point” (decides on appropriate response) & transmits command 4. Effector: receives & executes response to stimulus

4. Human thermostat

6. Pyrogens change the temperature control center “set-point” to a new higher level.
Fever = higher body temperature, often accompanies bacterial or viral infections
Blood flow shifted to core to conserve heat, shivering, increase in metabolic rate
Chills stop when higher temp reached
Benefits of a higher temperature:
Inhibits bacterial growth
Speeds up metabolic reactions for repair
Increases delivery of white blood cells to infection sites

7. Negative Feedback: Blood glucose regulation

8. Negative Feedback: Fluid/Electrolyte balance

9. Negative Feedback Loop Restores Homeostasis (Temperature)
In negative feedback systems the response of the effector negates or opposes the stimulus (shuts off the original stimulus)
Too hot > effector leads to less hot (sweat, increase skin blood flow, decrease metabolism)
Too cold > effector leads to less cold (shiver, behavioral changes, increase metabolism)
Responses are often controlled by nervous and endocrine systems (e.g. brain regulates body temp) EXTRINSIC CONTROL but sometimes controlled at the cell and tissue level = AUTOREGULATION or INTRINSIC CONTROL

10. Negative Feedback: Regulation of Blood Pressure
External or internal stimulus increase BP
Baroreceptors (pressure sensitive receptors)
Detect higher BP
Send nerve impulses to brain for interpretation
Response sent via nerve impulse sent to heart and blood vessels
BP drops and homeostasis is restored
Drop in BP negates the original stimulus

11. Homeostatic Regulation
Homeostasis- The existence of a stable internal environment.
Has 3 Parts:
Receptor: a sensor that is sensitive to a particular environmental change or stimulus.
Control Center: receives and processes the information supplied by the receptor.
Effector: a cell or organ that responds to the commands of the control center and whose activity opposes or enhances the original stimulus.

12. Feedback System Cycle of events Three Basic components
Body is monitored and re-monitored
Each monitored variable is termed a controlled condition
Three Basic components
Receptor
Control center
Effector

13. Feedback Systems Receptor
Body structure that monitors changes in a controlled condition
Sends input to the control center
Nerve ending of the skin in response to temperature change

14. Feedback Systems Control Center Brain
Sets the range of values to be maintained
Evaluates input received from receptors and generates output command
Nerve impulses, hormones
Brains acts as a control center receiving nerve impulses from skin temperature receptors

15. Feedback Systems Effector Receives output from the control center
Produces a response or effect that changes the controlled condition
Found in nearly every organ or tissue
Body temperature drops the brain sends and impulse to the skeletal muscles to contract
Shivering to generate heat

16. Paramecium eating pigmented yeast
"As the paramecium stuffs itself with a meal of pigmented yeast, vacuoles form. As food particles are digested by acidic enzymes, the congo red will reveal the pH drop-color will shift from a more alkaline red, to a more acidic blue."

17. Blood Clot Formation

18. Body’s
Internal
Environment

20. Homeostatic Imbalances
Normal equilibrium of body processes are disrupted
Moderate imbalance
Disorder or abnormality of structure and function
Disease specific for an illness with recognizable signs and symptoms
Signs are objective changes such as a fever or swelling
Symptoms are subjective changes such as headache
Severe imbalance
Death

21. Positive Feedback
Definition: enhances the original stimulus causing a greater deviation from the set point.
Activates infrequent events that require immediate action
Most are not related to the maintenance of homeostasis.
Positive feedback often results in disease.
Examples:
Blood clot
Uterine contractions in childbirth (stretch releases oxytocin from posterior pituitary),
Cancer

22. Positive Feedback Systems: Normal Childbirth
Uterine contractions cause vagina to open
Stretch-sensitive receptors in cervix send impulse to brain
Oxytocin is released into the blood
Contractions enhanced and baby pushes farther down the uterus
Cycle continues to the birth of the baby (no stretching)

23. Childbirth

24. Positive Feedback: Blood Loss
Normal conditions, heart pumps blood under pressure to body cells (oxygen and nutrients)
Severe blood loss
Blood pressure drops
Cells receive less oxygen and function less efficiently
If blood loss continues
Heart cells become weaker
Heart doesn’t pump
BP continues to fall

25. Positive Feedback -Disease

26. Two Types of Homeostasis
Negative Feedback: when the effector(s) activated by the control center oppose or eliminate stimulus.
Many examples; most common feedback system.
Positive Feedback: initial stimulus produces a response that exaggerates or enhances its effects.
Labor Contractions
Blood Clotting

27. Negative Feedback
Inhibitor
Oppose change by creating response opposite in direction of initial disturbance
change – temperature drop
response – heat production
initial disturbance – temp fall below normal set point
Stabilize physiological variables
Maintain constant internal environment
Ex: goosebumps, sweating
Positive Feedback
Stimulatory
Amplifies/reinforces change which can be harmful and disastrous
Cause instability and disrupt homeostasis (continuous temp increase)
Ex: sneezing, birth of baby, immune response to infection, blood clot

28. HOMEOSTASIS TUTORIALS & QUIZ
1.17_C_HOMEOSTASIS TUTORIALS_QUIZ