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Introduction. Physiology: Study of the function and relationship of the various organ systems. Made of 40% solid particles and 60% H2O The percentage of H2O varies with age, sex Babies: up to 80% H2O Older, slim person: 60%. The body. Figure 1.4. 2/3 cell fluid (intracellular fluid=ICF)

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introduction
Introduction
  • Physiology: Study of the function and relationship of the various organ systems
the body
Made of 40% solid particles and 60% H2O

The percentage of H2O varies with age, sex

Babies: up to 80% H2O

Older, slim person: 60%

The body
fluid compartments
2/3 cell fluid (intracellular fluid=ICF)

1/3 fluid outside the cell  extracellular fluid (ECF)

- 80% interstitial fluid (IF)

- 20% circulating fluid –

mostly plasma + CSF

+ eye and ear fluid

Fluid compartments
homeostasis
Homeostasis
  • The process of maintaining a constant internal environment despite changing external environment
  • Components:

- Sensors

- Integrating center

- Effectors

regulatory mechanisms
Regulatory mechanisms:
  • Negative feedback: the most common
  • Positive feedback: rare (ex:blood coagulation, parturition)
  • Most parameters controlling body function (heart rate, breathing rate, blood pressure, blood glucose..) are maintained within a narrow range
negative feedback
If a parameter value increases, body mechanisms works to bring the value down, within normal range

The most common mechanism

Negative feedback
positive feedback
As a value increases, the body reacts to increase the value further

Example: parturition (labor and delivery) and blood clotting

Positive feedback
regulation of body temperature
Body heat is a by-product of muscle contraction

Heat losses or gains are due to:

- convection: transfer of energy through moving gases or liquids

- conduction: transfer of heat energy between objects in direct contact

- radiation: transfer of energy through electromagnetic waves

- evaporation: loss of heat when water is evaporating

Regulation of body temperature
body temperature regulation normal body temperature 37 o c 98 6 o f
If external temperature is high body reacts to cool down

skin: flush appearance due to blood vessel dilation, sweating

Heart rate increases

Respiratory rate increases

If external temperature is low  body reacts to warm up

skin: pale appearance due to blood vessel constriction, goose bumps

Heart rate decreases

Respiratory rate decreases

Muscle shivering

Body temperature regulation Normal body temperature = 37oC = 98.6oF
mechanism of regulation
Mechanism of regulation
  • Temperature receptors in the skin and deep within the body send temperature information to the temperature integrating center in the hypothalamus
  • The integrating center makes a decision about the adjustments to be made
  • Effectors in charge of adjusting the temperature are activated
body temperature regulation normal body temperature 37 o c 98 6 o f15
If external temperature is high body reacts to cool down

skin: flush appearance due to blood vessel dilation, sweating

Heart rate increases

Respiratory rate increases

Body temperature regulation Normal body temperature = 37oC = 98.6oF
pathology of temperature regulation heat exhaustion
A person is working in the sun, is hot, sweat and drinks large amount of water

The electrolytes (salts) lost through sweating are not replaced  risk of seizures, loss of consciousness and death

Treatment: give fluids and electrolytes (ex: gatorade)

Pathology of temperature regulation: heat exhaustion
pathology of temperature regulation heat stroke
A person is working in the sun, is hot. The sun increases body and especially brain temperature

If the brain temperature reaches too high level, the brain becomes unable to react  sweating stops

Body temperature reach very high levels  the person dies

Pathology of temperature regulation: heat stroke
so what is fever
Body temperature can be as high as 35-36oC (105-106oF), despite external temperatures being much cooler.

Pathogens invade the body  macrophages fight against the infection and in the process secrete a special compound, a pyrogen.

A pyrogen has the ability to reset the body’s internal temperature to a higher level

When it does, the body reacts to increase its temperature  shivering, …  fever

When the body has won its battle against the pathogen, the macrophages no longer secrete pyrogen.

However, the body temperature is high  the temperature center in the hypothalamus direct the body to cool down  sweating ….

So what is fever?
readings
Readings
  • Chp. 1: p2-20. Book pages corresponding to notes.
  • Clinical connections: p 10
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