The Endocrine System: Pineal Gland Flashcards
Hormone Control
What is the purpose of hormones?
They are a way of adjusting bodily function
Hormone Control
Endocrine Hormones
Travel through the blood to a distant location for their action
Hormone Control
Paracrine Hormones
Hormones act on neighboring cells
Hormone Control
Autocrine Hormones
Cells release hormones that they can also respond to
Hormone Signaling
What are the three types of hormone signalling?
Cell Surface Receptor Signaling
Nuclear-Initated Steroid Signaling
Membrane-Initiated Steroid Signaling
Hormone Signaling
Cell Surface Receptor Signaling
Hormones bind to receptors on the surface of the cell and act thru second messengers to impact cell function
Hormone Signaling
Nuclear Initiated Steroid Signaling
Hormones cross the membrane then bind to receptors in the cytoplasm or nucleus
Usually cholesterol based hormones
Hormone Signaling
Membrane - Initiated Steroid Signaling
Steroid hormones can bind to receptors in the caveolae → are endocytosed → initiate activity of secondary messengers
The Pineal Gland: Epiphysis cerebi
What is the structure of the pineal gland? Where is it found?
Flattened, pine cone-shaped structure found in the midbrain (posterior wall of third ventricle in humans)
The Pineal Gland: Epiphysis cerebi
The pineal gland produces…
Melatonin
The Pineal Gland: Epiphysis cerebi
What is the function of melatonin?
In mammals: inhibits hormone production by the gonads
* regulates reproductive function
* Inhibits GnRH production by the pituitary
* Regulates diurnal cycle
Responsible for reproductive cycles
The Pineal Gland: Epiphysis cerebi
How does melatonin regulate the diurnal cycle?
- Obtains light/dark information from retina
- Light (daytime) - melatonin release inhibited
- Dark (nighttime) - melatonin released
The Pineal Gland: Epiphysis cerebi
What cell types are found in the pineal gland?
Pinealocytes
Glial Cells
Only about 5% of cells in the pineal gland are glial cells (they are similar to astrocytes and pituicytes)
The Pineal Gland: Epiphysis cerebi
What is the function of pinealocytes?
Produce melatonin
The Pineal Gland: Epiphysis cerebi
Describe pinealocytes histologically
Found in clumps or cords surrounded by CT septa (lobules)
Large nucleus with prominent nucleolus (nucleoli)
Lipid droplets in cytoplasm
Cytoplasmic processes in contact with blood vessels
Less compact nucleus
1 or more visible nucleoli
