01HOMEOSTASIS.ppt

8/9/2019 01HOMEOSTASIS.ppt

1/12

HOMEOSTASIS

Homeostasis is the maintenance of asteady state in the body despite

changes in the external environmentThe steady state is the optimum levelfor the body functions

© 2008 Paul Billiet O!"

http://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.html


2/12

A system in homeostasis

needs

Sensors to detect changes in the internalenvironment

# comparator $hich fixes the set point of the system%e&g& body temperature'&

The set point $ill be the optimum condition under$hich the system operates

Effectors $hich bring the system bac( to the setpoint

)eedbac( control& Negative feedback stops thesystem over compensating %going too far'

# communication system to lin( the different partstogether




3/12

A system in homeostasis

needs

Sensor Perturbation in

the interna

environment

!eturn to

normainterna

environment

Effector "omparator

Sensor

Negative

feedback




4/12

"ommunication systems

These should

consist of the

follo$ingcomponents #inkage

system

*ffector

Reponse

"ensor

Stimulus




5/12

In animas there are t$o

communication systems

The endocrine system based upon

hormones

The nervous system based uponnerve impulses




6/12

Hormones

Organic substances

Produced in small +uantities

Produced in one part of an organism%an endocrine gland'

Transported by the blood system

To a target organ or tissue $here ithas a profound effect




7/12

The endocrine system The endocrine system produces chemical

signals

*ach hormone is different and they travel

relatively +uic(ly through the blood stream allover the body

Their effects may be very slo$ %e&g& gro$th

hormone over years'

"ome are very fast %e&g& adrenaline $hich acts

in seconds'



8/12

Nerve impuses

#ll nerve impulses loo( the same

"o the nervous system sends signalsalong nerves to specific parts of the

body

The nerve impulses travel very +uic(ly

and affect their target tissues in

milliseconds© 2008 Paul Billiet O!"


9/12

The nervous system

The nervous system is composed of

excitable cells called neurones %also

neurons'

,eurones- characteristically- have long thinextensions $hich carry electrical nerve

impuses

This electrical signal of the nerve impulse

needs to be converted into a chemicalsignal %a neurotransmitter ' so that it can

pass from nerve cell to nerve cell



10/12

The nervous system

organisation # "entra Nervous System %.,"' made of the

brain and spinal cord/

and periphera nerves connecting it to sensors

and effectors

Stimulus

Effector

eg musce or gand

"entra Nervous

System

!eceptor or Sensor

eg photoreceptor

Sensory nerve

Response

Motor nerve



11/12


12/12

Hormone path$ay

Hormone

receptor site

Target ce

Metabolic effect


Documents

01HOMEOSTASIS.ppt