By DR QAZI IMTIAZ RASOOL

1. Discuss feedback (negative & positive) as a common characteristic of control system. 2. Describe the concept of tone and antagonism in control of body functions. 3. Discuss other types of control as feed-foreword and adaptive control. 4. Describe the concept of regulated change (rheostasis versus homeostasis). 5. Apply the knowledge gained to examples of control.

Which internal factors are being stressed in each picture?

1.Negative feedback 2.Positive feedback 3.Feed forward feedback 4. Servo-mechanisms 5. Others

1.Process by which a mechanism is activated to restore conditions to their original state 2.It ensures that small changes don’t become too large. 3. Defending the set point 4. Main form of regulation. (most feedback systems in the body) 5. Driving the variable in the opposite direction of the initial change. 6. Multiply the error signal by some proportionate factor(cold-shivering).

(Y) (T)

(Y) (T) GAIN= CORRECTION APPLIED RESIDUAL CHANGE

1. It must first suffer a disturbance before it can act 2. Delayed response 3. Overshoots the set point 4. FLAWS OVERCOME by : Feedforward system (Anticipation) Predicts

Positive feedback 1. ↑ es and amplifies the actions of the body 2. Produces more instability in the body 3. Produces more chaos in the body 4. Few types necessary for our survival 5. Short-lived 6. Controls less frequent forms of events that do not require continuous adjustments 7. Considered to be the uncommon loop 8. Driving the variable in the same direction of the initial change.

Harmful Effects of Positive Feedback Positive feedback can be harmful. e.g: 1.Fever can cause a positive feedback within homeostasis that pushes the body temperature continually higher.> 45 0 c (113 0 F) cellular proteins denature bringing metabolism to a stop and death. 2.Chronic hypertension - favor the process of atherosclerosis - narrow. This, in turn, will intensify the hypertension bring on more damage to the walls of blood vessels.

3. Feed-forward control ADAPTIVE FEEDBACK CONTROL Concept: a direct effect of stimulus on the control system before the action of feedback signal occurs. (prepare the body for the change). 1.Less frequent form of regulation. 2.Mechanism for minimizing lag time, stimulus triggers a response in anticipation of a change in a variable. 3.Here the direct effect of the stimulus is termed disturb signal or interfere signal. e,g 1. Shivering, smelling, Eating – sight or smell of food causes feedforward mechanisms, Muscle-Exercise –.

Significance of Feedback-forward : 1.Adaptive feedback control. 2.Makes the human body to fore-see and adapt the environment promptly and exactly 3.Prepare the body for the change. Servomechanism 1.Set piont is not fixed 2. Changes from time to time e.g stretch reflex

- Variation in the environment stimulates change – body response can result in either increase or decrease in activity. NOTE;-So when dealing with a body’s response to the environment it is not just simply on or off.  EX: insulin – bolus of food -glucose increases - glucose drops - decrease production- lower production 2. Antagonistic control If in the body something exists to shift homeostasis in one direction, an mechanisms exists that produces the opposite effect.  EX: Parasympathetic and sympathetic nervous system

1.Dynamic stability, 2.Regulated change. 3.Reset System changes the set point of a negative feedback system ◦ Recognizes that the body does not just stay the same all the time. There are necessary changes that occur – growth, development of the body – permanent changes result

1.Temporary emergencies 1.Fever, set point it centrally reset to higher and the body in turn attempts to maintain the set point – you shiver 2.Exposure to extreme cold – drives down the heart rate, blood pressure, and respiratory rate (used during heart and operations to allow for manipulation of structures) 1.Cyclical “clocks – Circadian rhythms 1.Temp – set point varies throughout the day. Am tends to be lower and PM tends to be slightly higher 2.Sex- Hormones released in a cycle- GH, cortisol at puberty Reproductive cycle -menstrual cycle

evolution by natural selection Acclimatization - physiological, biochemical, or anatomical change within an individual from chronic exposure to a new environment

1.Chemical reactions in our body rely on enzymes (biological catalysts made of proteins) 2.They need a reasonably high temperature to allow enough collisions with other molecules (substrates) but not too high in case they denature (no longer work) 37.0 ° (set point)

7.4

1. Your cells also need an exact level of glucose in the blood. 2. Excess glucose gets turned into glycogen in the liver 3. This is regulated by 2 hormones (chemicals) from the pancreas Insulin Glucagon

If there is too much glucose in the blood, Insulin converts some of it to glycogen Glycogen Insulin Glucose in the blood

If there is not enough glucose in the blood, Glucagon converts some glycogen into glucose. Glycogen Glucagon Glucose in the blood

The glucose in the blood increases. Glycogen Insulin Glucose in the blood But there is no insulin to convert it into glycogen. Glucose concentration rises to dangerous levels.

Time Glucose Concentration Meal eaten Insulin is produced and glucose levels fall to normal again. Glucose levels rise after a meal. Normal

Time Glucose Concentration Meal eaten Insulin is not produced so glucose levels stay high Glucose levels rise after a meal. Diabetic

The skin

If the temperature rises, the blood vessel dilates (gets bigger). This means more heat is lost from the surface of the skin

If the temperature falls, the blood vessel constricts (gets shut off). This means less heat is lost from the surface of the skin What mechanisms are there to warm the body up? Vasoconstriction

What mechanisms are there to warm the body up? Piloerection This is when the hairs on your skin “stand up”. It is sometimes called “goose bumps” or “chicken skin”! The hairs trap a layer of air next to the skin which is then warmed by the body heat The air becomes an insulating layer.

:00:000:02:000:04:000:06:00 HR [bpm] Time Healthy mean and variance Sit Stand Healthy response