Chapter 1- Communication and Homeostasis

CELL SIGNALLING

• A chemical or electrical signal is produced by cells for communicatio
• Paracrine signalling: communication between cells close by
• Endocrine signalling: communcation between cells over long distances
• Needed for the response to external and internal conditions
• Needed for the co-ordinations of organs in the body

THE PRINCIPLES OF HOMEOSTASIS

• Homeostasis: maintenance of near-constant conditions within narrow limits

Negative feedback

• NF: type of control mechanism in which a change is detected in the environment and a response is made to restore normal value of condition 
• Example/ Increase in blood glucose concentration

Positive feedback

• PF: type of control mechanism in which a change is detected in the environment and a response is made to proliferate the change 
• Example/ Oxytocin released in labour, intensifies uterine contractions 

CONTROL OF BODY TEMPERATURE

• In…