Download KINE 3315 Chapter 2 powers

Chapter 2:
Control of the
Internal Environment
Objectives
Define the terms homeostasis and steady
state
Diagram and discuss a biological control
system
Give an example of a biological control
system
Explain negative feedback
Define what is meant by the gain of a
control system
Homeostasis: Dynamic
Constancy
Homeostasis
– Maintenance of a constant internal
environment
Steady state
– Balance between demands placed on body
and the physiological response to those
demands
Body Core Temperature
During Exercise
Fig 2.2
Blood Pressure at Rest
Fig 2.3
Control Systems of the Body
Goal
– To regulate some physiological variable at or
near constant value
– Maintain homeostasis
Non-Biological Control System
” in room
Temperature
below 200 C
Room
temperature
Returns to 200 C
’Room Temperature
Signals thermostat
To turn off heat
Thermostat set
at 200 C
Heating System
Fig 2.4
Biological Control Systems
Series of interconnected components that serve
to maintain a physical or chemical parameter at
or near constant
Receptor
– Capable of detecting changes
Integrating center
– Assesses input and initiates response
Effector
– Corrects changes to internal environment
– Removing stimulus
Components of a Biological
Control System
Fig 2.5
Control Systems
Most biological control systems
– Response reverses the initial disturbance in
homeostasis
– Negative feedback
Negative Feedback
Receptors
– Chemoreceptors
Specialized nerve endings → CNS
Respond to changes in O2 and CO2
Exercise
– Adrenergic (adrenaline) (α1 and α2)
Epinephrine (hormone) and Norepinephrine (SYM)
Inhibit or excite
Receptors
Receptors (cont)
– Proprioceptors (sensory)
Golgi, muscle spindles, joint receptors
Body position
Mechanoreceptors (muscle) – sensitive to force
and speed
– Body temperature
Skin (thermal receptors)
Core (stimulates sweat glands)
Positive Feedback
Vicious cycle
– Hemorrhage
Heart ↓ pumping ability
Decreased coronary blood flow
Further weakens heart
Clotting (useful)
– Clotting factors activate enzymes to clot blood
Clotting (vicious cycle)
– Heart attacks
Gain of a Control System
Gain of the system
– Degree to which the control system maintains
homeostasis
– System with large gain is more capable of
maintaining homeostasis
– System with small gain is less capable of
maintaining homeostasis
Gain of a control system
Small gain
– Baroreceptors
Normal pressure – 100 mmHg
Blood infusion – 175 mmHg (no baroreceptors)
Blood infusion – 125 mmHg (with baroreceptors)
Large gain (greater control)
– Body temperature
– 98 to 98.8 oC
Example:
Regulation of Blood Pressure
Fig 2.6
Example:
Regulation of Blood Glucose
Fig 2.7
Stress Proteins
Disturbance beyond gain
Proteins help maintain homeostasis
– Intracellular transporters
– Enzymes
Stress Proteins
Stress proteins
– Synthesized to repair damaged proteins
– Restore homeostasis
Stressors
– Hyperthermia
– Hypoxia
– Alkalosis
– Free radical production
Example:
Cellular Stress Response
Fig 2.8
Exercise: A Test of Homeostatic
Control
Submaximal exercise in a cool
environment
– The body’s control systems can maintain
steady state
– Lactic acid produced = lactic acid utilized
– Oxygen delivery = oxygen required for ATP
Body Core Temperature
During Exercise
Fig 2.2
Exercise: Homeostatic Control
Maximal exercise or exercise in a
hot/humid environment
– May not be able to maintain steady state
– Severe disturbances in homeostasis can
occur
Exercise
Heavy exercise
– Lactic acid – acidosis
– ↑ carbon dioxide production
– ↑ oxygen requirements
Resulting in
– ↑ in pulmonary ventilation
– ↑ in blood flow