Chapter I - The Human Body: An Orientation (Part 2)

HE WMAN BOODD : DORII ENTATION CONT
mmmm .




1. 4 : Homeostasis is maintained by negative feedback
Homeostasis a state of body equilibrium or stable internal environment of the
body .




Homeostasis Control is communication within the body ,
it is accomplish by the nervous and
endocrine
systems which use neural electrical impulses or blood borne hormones , respectively
as information carriers
.



The variable is the factor or event being regulated
.


3
Input : Information sent



J
4
along afferent pathway to Control Output : Information sent along


- -
Control center Center
efferent to effector
pathway
Afferent Efferent
pathway pathway
2
receptor detects change
Eceptor Effector



↓
.




*
I
5
Response of effector


*
A IMB feeds back to reduce the




·
*

I
effect of stimulus and
returns


variable to homeostatic level .




I stimulus produces
-
=>

change in variable

IMB
ALANCE
The receptor is the first component. It is a sensor that monitors the environment. It responds to stimuli (changes) by
sending information (input) along the afferent
pathway to the second component ,
the control center .




The control center determines the set which is the level at which variable is to be maintained
. It
point ,
a
analyzes the inp
it receives point appropriate response Information (output)
by comparing it to the set and determines the .
then flows

flows the control center along the efferent to the third component the effector (to help you
pathway ,
. remember the

difference between "afferent" and "efferent" , note that information traveling along the afferent pathway approaches the

control center .)
and efferent information exits from the control center


The effector carries out the control Center's response to the Stimulus
. The results of the response then feedback to influence the

effect of the stimulus either shut off, enhancing that the whole process
,
reducing it so that the whole control process is or it so

continues at an even faster rate
.




Negative feedback mechanisms the most common . The net effort is that the
homeostatic control mechanism output of the system
shuts off the
original stimulus or reduces its intensity .

, Body temperature is regulated by a
negative feedback mechanism
.




- ·
Afferent
pathway
Efferent

pathway

~
tor
E
Effector
sweat glands sweat gland activated




I
I IMB
Response
Evaporation of sweat
*
A




·
*
Body temprises bodytempfals i
Stimulus : heat I
=>

Stimulus : Cold

Response *
Body temperature
M
fails
Body temperature
2




rises ; stimulus
ends
#


② *
Effectors
Receptors
Skeletal muscles temperature sensitive
-




cells in skin and brain
↳

Efferent Afferent
pathway Pathway



I
Control center
thermoregulatory #
center in brain
shivering begins


Remember :

Negative feedback mechanisms work to minimize changes in the value of a controlled

variable.