ODWS icon

The Open Door Web Site
HOMEPAGE BIOLOGY HOMEPAGE CHEMISTRY PHYSICS ELECTRONICS HISTORY HISTORY OF SCI & TECH MATH STUDIES LEARNING FRENCH STUDY GUIDE  PHOTO GALLERY
IB BIOLOGY HOMEPAGE SCIENTIFIC INVESTIGATIONS DRAWING IN BIOLOGY DRAWING TABLES ERROR ANALYSIS IN BIOLOGY ALL ABOUT GRAPHS ICT IN BIOLOGY STATISTICS SCIENTIFIC POSTERS MOLECULAR IMAGES
WS

Powerpoint Presentation: Homeostasis

 

Homeostasis Index

The hormone pathway
Thermoregulation
The Pancreas, Insulin and Glucagon Fact Sheet
The homeostatic control of blood glucose levels
Homeostatic control of water balance

Topic Chapters Index

 

In animals there are two communication systems

The endocrine system based upon hormones

Hormones are organic substances produced in small quantities in one part of an organism (an endocrine gland), transported by the blood system to a target organ or tissue where it has a profound effect.

The endocrine system therefore produces chemical signals. Each hormone is different and they travel relatively quickly through the blood stream all over the body. Their effects may be very slow (e.g. growth hormone over years) or very fast (e.g. adrenaline which acts in seconds).

 

The nervous system based upon nerve impulses

The nervous system is composed of excitable cells called neurones (also neurons). Neurones, characteristically, have long thin extensions which carry electrical nerve impulses. This electrical signal needs to be converted into a chemical signal (a neurotransmitter) so that it can pass from nerve cell to nerve cell.

All nerve impulses look the same. So the nervous system sends signals along nerves to specific parts of the body. The nerve impulses travel very quickly and affect their target tissues in milliseconds.

 

 

HOMEOSTASIS

Custom Search

Introduction

Homeostasis is the maintenance of a steady state in the body despite changes in the external environment. The steady state is the optimum level for the body functions.

For example the core temperature of the human body remains at about 37°C despite fluctuations in the surrounding air temperature.

For example the blood glucose level remain about 1g per litre despite fasting or eating a meal rich in sugars.

Other examples of homeostatically controlled variables include: blood concentration (osmoregulation), blood pH (about pH 7.35), blood O2 and CO2 levels.

 

A system in homeostasis needs:

  • Sensors to detect changes in the internal environment.

  • A comparator which fixes the set point of the system (e.g. body temperature). The set point will be the optimum condition under which the system operates.

  • Effectors which bring the system back to the set point.

  • Feedback control. Negative feedback stops the system over compensating (going too far).

  • A communication system to link the different parts together.

Homeostasis

 

Communication systems

These should consist of the following components:

communcation systems

The nervous system is organised into:

  • A Central Nervous System (CNS) made of the brain and spinal cord

  • And peripheral nerves connecting it to sensors and effectors

The CNS

 

The Open Door Web Site is non-profit making. Your donations help towards the cost of maintaining this free service on-line.

Donate to the Open Door Web Site using PayPal

SITE MAP
WHAT'S NEW?
ABOUT

PRIVACY

COPYRIGHT

SPONSORSHIP

DONATIONS

ADVERTISING

© Paul Billiet 2018
Any questions or problems regarding this site should be addressed to the webmaster

Hosted By
Web Hosting by HostCentric


SiteLock