BIOL 1050H Lecture Notes - Lecture 10: Paraventricular Nucleus Of Hypothalamus, Supraoptic Nucleus, Osteoblast
Endocrine System
Mechanisms of Communication Between Cells
1. Gap junctions
• Pores in cell membrane allow signaling molecules,
nutrients, and electrolytes to move from cell to cell
2. Neurotransmitters
• Released from neurons to travel across synaptic cleft to
second cell
3. Paracrines
• Secreted into tissue fluids to affect nearby cells
4. Hormones • Chemical messengers that travel in the bloodstream to
other tissues and organs
The Endocrine System
Glands, tissues, and cells that secrete hormones
• Endocrinology
• the study of this system and the diagnosis and treatment of its
disorders
• Endocrine glands
• organs that are traditional sources of hormones
• Hormones
• chemical messengers that are transported by the bloodstream • stimulate physiological
responses in cells of another tissue or
organ
• often a considerable distance away
Endocrine vs.
Exocrine Glands
Exocrine glands Have ducts Carry secretion to an
epithelial surface or the
mucosa of the digestive tract:
“external secretions” Extracellular effects (food
digestion)
Endocrine glands No ducts Contain dense, fenestrated
capillary networks which
allow easy uptake of
hormones into bloodstream:
