Transcript The Endocrine System

The Endocrine System
VS 223
Dr. Noland
Endocrine Glands
• Secrete their product directly
into bloodstream
• Known as “ductless” glands
Hormones
• Act on target organs due to specific
receptors located on the target
plasma membrane
Neuroendocrine Reflex
• Nerve input on the afferent end
• Hormonal input on the efferent end
• Suckling reflex
• Induced ovulation in cats, rabbits
Endocrine Glands
• Discrete gland - Adrenal gland
• Organ – Duodenum
• Combo of Exocrine/Endocrine Pancreas
Classification of Hormones
• Peptides – chains of amino acids
–Most hormones
• Amines – tyrosine derivatives
–Catecholamines, T4
• Steroids – cholesterol derivatives
–Gonadal hormones and adrenal
cortical hormones
Mechanisms of Action
• Hormones circulate in the
bloodstream and bind with
target organ cell receptors to
affect a change in the target cell
Hydrophilic
Hormones
Peptides and
Catecholamines
Lipophilic Hormones
Steroids and Thyroid
Hormonal
Action
Feedback Regulation