Chapter 18: The Endocrine System Flashcards
What is the function of the endocrine system
To secrete chemical messengers (hormones) that will be delivered to the blood, producing a gradual change over time.
(Different from an impulse which produces results immediately)
Where do endocrine glands secrete hormones
Into the interstitial fluid around secretory cells which will diffuse through blood capillaries, and be carried to target cells throughout the body.
How can endocrine glands be organized?
- As a discrete organ (ex. The thyroid gland)
- As a group of cells within an organ (ex. Pancreas, testis)
- Individual cells within another organ (ex. Erythropoietin in kidney)
Paracrine hormone
Hormones that act on neighbouring cells
(Does not enter the blood stream)
Autocrine hormone
Hormones that act on the same cell that secreted them
(Does not enter the blood stream)
What is down regulation
When a target cell DECREASES it number of receptors due to INCREASE of the hormones concentration.
(Target cells becomes less sensitive to hormone)
doesn’t need anymore hormone
What is up regulation
When a target cell INCREASES its number of receptors due to DECREASE of the hormones concentration.
(Target cell becomes more sensitive to hormone)
needs more hormone
What are the 5 things that hormones can do to target cells?
- Stimulate protein synthesis
- Change membrane properties
- Activate/deactivate enzymes
- Increase secretory activity
- Stimulate mitosis
Humoral stimuli
Stimulates the creation and release of hormones through chemical changes in blood or nutrient levels
Neural stimuli
Stimulates the creation and release of hormones through nerve impulses
Hormonal stimuli
Stimulates the creation and release of hormones through tropic hormones (one hormone influencing another hormone to release)
How many hormones does the hypothalamus produce?
9 total
7 of them communicate with anterior pituitary gland (5 secretory, 2 inhibitory)
2 of them with posterior pituitary gland (antidiuretic and oxytocin)
What is a portal system?
Blood flowing from 1 capillary bed, into a portal vein, then into a second capillary bed.
Ex. Hypophyseal portal system (transports 5 secretory hormones into the anterior pituitary)
Infundibulum
Attaches the hypothalamus to the pituitary gland
The pituitary gland
Anterior lobe: secretes 6 hormones (GH, TSH, FSH, LH, ACTH, prolactin)
Posterior lobe: secretes 2 hormones (ADH, oxytocin)
