The Study of Body Function Lecture 1- foundation

Prof. Hisham Al-Matubsi

Lecture 1 Outline

Introduction to Physiology

Homeostasis

HUMAN PHYSIOLOGY

Physiology: study of how body works to maintain life

Pathophysiology: how physiological processes are altered in

disease or injury

HOMEOSTASIS

Is maintenance of fairly constant internal conditions

Around physiological set points

Maintained by negative feedback loops

NEGATIVE FEEDBACK LOOPS

Sensor: Detects deviation from set point

Integrating center: Determines response

Effector: Produces response

Control center Thermostat detects deviation from set point and signals effectors.

Receptors Thermostat in room detects change.

Effectors Heater turns off; air conditioner turns on.

Stimulus Room temperature rises above normal.

Response Room temperature returns toward set point.

too high

Normal room temperature

too low

Stimulus Room temperature Decreases.

Response Room temperature returns toward set point.

Receptors Thermostat in room detects change.

Effectors Heater turns on; air conditioner turns off.

Control center Thermostat detects deviation from set point and signals effectors.

Thermostat set point.

Thermostat as example of homeostatic mechanism

Thermostat as example of homeostatic mechanismSlide number: 2

Stimulus Room temperature rises above normal.

too high

Normal room temperature

Thermostat set point.

Thermostat as example of homeostatic mechanismSlide number: 3

Receptors Thermostat in room detects change.

Stimulus Room temperature rises above normal.

too high

Normal room temperature

Thermostat set point.

Thermostat as example of homeostatic mechanismSlide number: 4

Control center Thermostat detects deviation from set point and signals effectors.

Receptors Thermostat in room detects change.

Stimulus Room temperature rises above normal.

too high

Normal room temperature

Thermostat set point.

Thermostat as example of homeostatic mechanism Slide number: 5

Control center Thermostat detects deviation from set point and signals effectors.

Receptors Thermostat in room detects change.

Effectors Heater turns off; air conditioner turns on.

Stimulus Room temperature rises above normal.

too high

Normal room temperature

Thermostat set point.

Thermostat as example of homeostatic mechanism Slide number: 6

Control center Thermostat detects deviation from set point and signals effectors.

Receptors Thermostat in room detects change.

Effectors Heater turns off; air conditioner turns on.

Stimulus Room temperature rises above normal.

Response Room temperature returns toward set point.

too high

Normal room temperature

Thermostat set point.

Thermostat as example of homeostatic mechanism Slide number: 7

Normal room temperature

too low

Thermostat set point.

Stimulus Room temperature Decreases.

Thermostat as example of homeostatic mechanism Slide number: 8

Normal room temperature

too low

Thermostat set point.

Stimulus Room temperature Decreases.

Receptors Thermostat in room detects change.

Thermostat as example of homeostatic mechanism Slide number: 9

Normal room temperature

too low

Thermostat set point.

Stimulus Room temperature Decreases.

Receptors Thermostat in room detects change.

Control center Thermostat detects deviation from set point and signals effectors.

Thermostat as example of homeostatic mechanism Slide number: 10

Normal room temperature

too low

Thermostat set point.

Stimulus Room temperature Decreases.

Effectors Heater turns on; air conditioner turns off.

Receptors Thermostat in room detects change.

Control center Thermostat detects deviation from set point and signals effectors.

Thermostat as example of homeostatic mechanism Slide number: 11

Normal room temperature

too low

Thermostat set point.

Stimulus Room temperature Decreases.

Response Room temperature returns toward set point.

Effectors Heater turns on; air conditioner turns off.

Receptors Thermostat in room detects change.

Control center Thermostat detects deviation from set point and signals effectors.

By turning heater on (antagonistic effect) i.e activity of effector is in negative or reverse negative feedback loop Negative feedback: Effectors are activated by changes in the internal environment and inhibitory actions of the effectors serve to counteract these changes and maintain a state of internal constancy or homeostasis

HOMEOSTASIS

Regulatory mechanisms:

Intrinsic control is built into organ being regulated

Extrinsic control comes from outside of organ

By nervous or endocrine systems

E.g. nervous control of body temperature

Homeostatic mechanism regulates body temperature

Slide number: 1

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Control center The brain detects the deviation from the set point and signals effector organs.

Receptors Thermoreceptors send signals to the control center.

Effectors Skin blood vessels dilate and sweat glands secrete.

Stimulus Body temperature

rises above normal.

Response Body heat is lost to surroundings,

temperature drops toward normal.

too high

too low

Normal body

Temperature

37oC (98.6oF)

Stimulus Body temperature

drops below normal.

Response Body heat is conserved,

temperature rises toward normal.

Receptors Thermoreceptors send signals to the control center.

Effectors Skin blood vessels constrict and sweat glands remain inactive.

Effectors generates body heat.

Control center The brain detects the deviation from the set point and signals effector organs.

If body temperature continues to drop, control center signals muscles to contract involuntarily.

Homeostatic mechanism regulates body temperature Slide number: 2

Stimulus Body temperature rises above normal.

too high

Normal body Temperature 37oC (98.6oF)

Homeostatic mechanism regulates body temperature Slide number: 3

Receptors Thermoreceptors send signals to the control center.

Stimulus Body temperature rises above normal.

too high

Normal body Temperature 37oC (98.6oF)

Homeostatic mechanism regulates body temperature Slide number: 4

Control center The brain detects the deviation from the set point and signals effector organs.

Receptors Thermoreceptors send signals to the control center.

Stimulus Body temperature rises above normal.

too high

Normal body Temperature 37oC (98.6oF)

Homeostatic mechanism regulates body temperature Slide number: 5

Control center The brain detects the deviation from the set point and signals effector organs.

Receptors Thermoreceptors send signals to the control center.

Effectors Skin blood vessels dilate and sweat glands secrete.

Stimulus Body temperature rises above normal.

too high

Normal body Temperature 37oC (98.6oF)

Homeostatic mechanism regulates body temperature Slide number: 6

Control center The brain detects the deviation from the set point and signals effector organs.

Receptors Thermoreceptors send signals to the control center.

Effectors Skin blood vessels dilate and sweat glands secrete.

Stimulus Body temperature rises above normal.

Response Body heat is lost to surroundings, temperature drops toward normal.

too high

Normal body Temperature 37oC (98.6oF)

Sweeting and increased blood flow

cause increased heat loss

too low

Normal body Temperature 37oC (98.6oF)

Homeostatic mechanism regulates body temperature Slide number: 7

Stimulus Body temperature drops below normal.

Receptors Thermoreceptors send signals to the control center.

too low

Normal body Temperature 37oC (98.6oF)

Homeostatic mechanism regulates body temperature Slide number: 8

Stimulus Body temperature drops below normal.

Receptors Thermoreceptors send signals to the control center.

too low

Normal body Temperature 37oC (98.6oF)

Homeostatic mechanism regulates body temperature Slide number: 9

Stimulus Body temperature drops below normal.

Control center The brain detects the deviation from the set point and signals effector organs.

Receptors Thermoreceptors send signals to the control center.

too low

Normal body Temperature 37oC (98.6oF)

Homeostatic mechanism regulates body temperature Slide number: 10

Stimulus Body temperature drops below normal.

Control center The brain detects the deviation from the set point and signals effector organs.

If body temperature continues to drop, control center signals muscles to contract involuntarily.

Effectors Skin blood vessels constrict and sweat glands remain inactive.

Receptors Thermoreceptors send signals to the control center.

too low

Normal body Temperature 37oC (98.6oF)

Homeostatic mechanism regulates body temperature Slide number: 11

Stimulus Body temperature drops below normal.

Effectors Muscle activity generates body heat.

Control center The brain detects the deviation from the set point and signals effector organs.

If body temperature continues to drop, control center signals muscles to contract involuntarily.

Effectors Skin blood vessels constrict and sweat glands remain inactive.

Receptors Thermoreceptors send signals to the control center.

too low

Normal body Temperature 37oC (98.6oF)

Homeostatic mechanism regulates body temperature Slide number: 12

Stimulus Body temperature drops below normal.

Response Body heat is conserved, temperature rises toward normal.

Effectors Muscle activity generates body heat.

Control center The brain detects the deviation from the set point and signals effector organs.

If body temperature continues to drop, control center signals muscles to contract involuntarily.

Decreased skin blood flow

helps retain heat

Shivering produced heat

NEGATIVE FEEDBACK HORMONAL CONTROL OF

BLOOD GLUCOSE

Homeostasis Sate of relative constancy of internal environment. To maintain homeostasis, such environmental changes or stimuli are detected, conveyed via nervous to the spinal cord and brain. The incoming information is then processed and conveyed by nervous to the muscle and glands of the body causing the muscle to contract or relax and glands to secrete or not secrete their product.

POSITIVE FEEDBACK LOOP

Activation of one clotting factor results in activation of many other factors in a positive feedback cascade. (Amplification of an initial changes)

Another example: Oxytocin from pituitay gland →stimulates

contractions of uterus → Contraction of uterus →stimulates more secretion of oxytocin → more contractions of uterus and so on