Lecture 16- Physiological Aspects of the Endocrine System

What is a hormone?

• A chemical sign that enables an event in one part of the body to have an effect elsewhere in the body

Thyroid gland

• Secretes T3 and T4 follicular cells
• Calcitonin - parafollicular cells

3 Types of cell signalling

• Autocrine
• Paracrine
• Endocrine

Proteins, peptides and amines

• Hydrophilic
• Cell surface receptors, act via second messenger systems
• Circulate primarily dissolved in plasma

Steroids and Thyroid hormones

• Hydrophobic
• Intracellular receptors, promote or supress gene transcription
• Circulate primarily bound to plasma proteins

Factors…