Chapter 18 - Endocrine System Flashcards
Master terms in Ch 18
What are the functions of hormones?
Regulate activity of smooth/cardiac muscle, glands, alter metabolism, spur growth and development, influence reproductive processes, and participate in circadian rhythms.
Endocrine gland basics
Secrete hormones into bloodstream.
System consists of pineal, thyroid, pituitary, parathyroid, adrenal.
Other hormone secreting organs may also be involved such as the hypothalamus, ovaries/testes, pancreas, kidneys, stomoach, liver, small intestine, skin, heart, adipose tissue, placenta, thymus.
Exocrine gland basics
secrete their products into ducts into body cavities or onto surfaces (sudorriferous, sebaceous, mucous, mammary, digestive).
Basics of hormone activity
- Hormones affect specific targets that have receptors to bind a given hormone.
- The number of receptors may decrease or increase called down-or-up-regulation.
- May be lipid soluble or water soluble
Local hormone activity
Paracrines - act upon adjacent structures
Autocrines - act upon themselves
Water soluble and lipid soluble hormone
Lipid soluble - thyroid, steroid, androgens. Can pass through the phospholipid membrane easily and receptors are inside the cell or nucleus.
Water soluble - amines, peptides, eicosanoids. Can’t pass through the phospholipid membrane so receptors are on the outside of the membrane and must be bound to proteins to pass through. (Described in detail in another card).
Hypothalamus and Pituitary Gland
The infundibulum connects the two glands, and connects the posterior pit and hypothalamus with a tract of nerves (hypothalmic-hypophyseal tract).
Hypothalamus hormones are tropic hormones (other glands are the target).
7 hormones of the anterior pituitary
GH TSH FSH LH PRL ACTH MSH
2 hormones of the posterior pituitary
Oxytocin, antiduretic hormone
Primary plexus of the hypophyseal portal system
Network of capillaries outside the infundibulum where the hypothalmic inhibitory or releasing hormones target complimentary and specific cells on the anterior pit.
Thyroid gland
- Located in the lower neck - sternal notch
- Butterfly shaped (ishthmus in between the wings/lobes) and heavily vascularized
- There are 2 cells in the gland - parafollicular cells and follicular cells.
- Follicular cells are stimulated b y TSH and they produce T4 and some small T3.
- Parafollicular cells produce the hormone calcitonin to regulate calcium homeostaisis (target: osteoblasts - to decrease blood calcium).
8 steps of thyroid hormone synthesis
1 - Iodide trapping from the blood 2 - Synthesis of thyrogobulin (TGB) 3- Oxidation of iodide 4 - Iodination of tryosine 5 - Coupling of T1 and T2 6 - Pinocytosis and digestion of colloid 7 - Secretion of thyroid hormones 8 - Transport in the blood
Functions of the thyroid hormones
1 - Increases the BMR
2- Maintains body temp (with hypothamus)
3- Stimulate protein synthesis
4- Increases fight or flight/catecholamines
5- Regulation and development of growth and nervous tissues, and bones.
Parathyroid glands
Produces PTH
Contains chief cells and oxyphyl cells.
Chief cells release PTH in response to low calcium level by releasing calcitonin. Target cells of PTH are the osteoclasts (w calcitriol) increase calcium in the blood.
Adrenal glands
- AKA “suprarenal” glands above the kidneys.
- Aldosterone is the major mineralocorticoid regulates sodium and potassium homeostasis.
- Contains a cortex and medulla
- Cortex has 3 zones (glomerulaosa, fascitulata, reticularis)
Medulla is where norepinephrine and epinephrine are secreted.
