HOMEOSTASIS

• maintenance of a relatively constant environment within the body.

  homeostasis
• to achieve homeostasis, the body must be actively regulate body conditions that are constantly changing

  true
• body temperature is one of body's

  variable
• these changes in body conditions are called variables because their values are not 


  constant
• for cells to function normally, the volume, temperature, and chemical content of the cell's environment must be maintained within a narrow range

  true
• _ is variable that increase when you are too hot and decreases when you are too cold.

  body temperature
• maintain normal body temperature include sweating or shivering to maintain body temperature near an ideal normal value, or set point

  homeostatic mechanisms
• or set point


  ideal normal value,
• most homeostatic mechanisms are regulated by what systems?

  nervous system and endocrine system
• homeostatic mechanisms are not able to maintain body temperature precisely at the set pointinstead body temp increase and decrease slightly around the set point, producing a _of values.


  normal range
• normal body temp


  1 degrees F above or normal
• average body temp

  98.6 degrees F
• the _ help keep the bodys internal environment relatively constant

  organ system
• if body fluids deviate from homeostasis, body cells do not function normally and can even die.

  true
• disrupts homeostasis and sometimes results in death

  disease
• most systems in the body are regulated by_ which maintains homeostasis

  negative- feedback mechanisms
• the word negative from "negative feedback means"


  to decrease
• when any deviation from the set point is made smaller or is resisted

  negative feedback
• does not prevent variation but maintains variation within a normal range.

  negative feedback
• the maintenance of normal body temperature is an example of

  negative feedback mechanism
• 3 components of negative feedback mechanisms

  receptor, control center, effector
• which monitors the value of a variable, such as body temperaturesby detecting stimuli

  receptor
• such as part of the brain, which determines the set point for the variable and receives input from the receptor about the variable

  control center
• such as the sweat glands, which can adjust the value of the variable when directed by the control center, usually back to the set point

  efffector
• a changed variable is a _ cause it initiates a homeostatic mechanism

  stimulus
• type of mechanism that works to maintain homeostasis

  positive feedback
• occur when a response to the original stimulus results in deviation from the set point becoming even greater

  positive- feedback mechanism
• positive means


  increase
• this response is required to return to homeostasis

  positive feedback
• chemical responsible for blood clot formation called

  thrombin
• 2 basic principles about homeostatic mechanisms to remember are that

  (1) many disease states result from the failure of negative feedback to maintain homeostasis (2) mechanisms can be detrimental instead of helpful
• example of detrimental positive- feedback mechanism

  inadequate delivery of blood to cardiac muscle
• _ of cardiac muscle generates blood pressure

  contraction
• following a modern amount of blood loss, _ result in an increase in heart rate that restores blood pressure

  negative- feedback mechanisms
•   -  maintenance of constant internal environment

  homeostasis
• measures of body properties that may

                    change in value

  variables:
• Examples of variables:

   

  body temperature         blood glucose levels

    heart rate         blood cell counts

    blood pressure         respiratory rate
•   normal, or average value of a variable


  set point:
• normal extent of increase or decrease around a set point

  normal range
•   example: over time, body temperature fluctuates around

                   a set point of about 98.6o 

  example of normal range