Endocrine System (Q4,P5) Flashcards
Endocrine System
-A system of glands and organs hat make hormones and release them directly into the blood so they can travel to tissues and organs all over the body
- a system of ductless glands
- Secrete messenger molecules called hormones
- this system interacts closely with the nervous system
What is a ductless gland?
glands that produce secretions that are released directly into the blood, not to any tubes or ducts
Endocrinology
study of hormones and endocrine glands
Pure Endocrine Glands
- Pituitary
- Pineal
- Thyroid
- Parathyroid
- Adrenal Glands
Organs containing endocrine cells
- Pancreas
- Thymus
- Gonads
- Hypothalamus
Hormones Function
- Circulate throughout the body in blood vessels and influence specific target cells
ex: Regulate blood sugar levels, regulate calcium ion levels
Humoral Stimuli
- simplest of endocrine control mechanisms
- Secretion in direct response to changing ion or nutrient levels in the blood
Neural Stimuli
- sympathetic nerve fibers stimulate cells in the adrenal medulla
- Induces release of epinephrine and norepinephrine
Hormonal Stimuli
- stimuli received from other glands
- Certain hormones signal secretion of other hormones
Pituitary Gland/Hypophysis
- called the “master gland” of the endocrine system
- Secretes nine major hormones
- Main hormone: growth hormone (HGH/ somatotropin)
- Attached to the hypothalamus by the infundibulum
Thyroid Gland
- largest pure endocrine gland
- Located in the anterior neck
- Produces two hormones: Thyroid hormone (TH), Calcitonin
Thyroid Hormone (TH)
Hormone that controls metabolism
Calcitonin
Hormone that decreases blood concentration of calcium ions (Ca2+)
Parathyroid Gland
- Lie on the posterior surface of the thyroid gland
- Produces parathyroid hormone (PTH)
Parathyroid Hormone (PTH)
Increases blood concentration of calcium ions Ca2+
Adrenal Glands
- Located on the superior surface of the kidneys
- Nerve supply is almost exclusively sympathetic fibers
- Two endocrine glands in one: adrenal medulla, adrenal cortex
Adrenal Medulla
- a knot of nervous tissue
- Secrete hormones that are active in “fight, flight, and fright” response
Adrenal Cortex
- bulk of the adrenal gland
- Secretes a variety of hormones: only steroids are secreted from the adrenal cortex
Pineal Gland
- Located on the roof of the diencephalon
- Shaped like a pinecone
- secretes melatonin
Melatonin
A hormone that regulates circadian rhythms (sleep-wake cycle)
Pancreas
- Located in the posterior abdominal wall
- Heterocrine Gland: Contains both endocrine and exocrine cells
Exocrine Cells of the Pancreas
- Pancreatic cells that produce and transport chemicals that will exit the body through the digestive system.
- Secrete digestive enzymes
Endocrine Cells of the Pancreas
- Pancreatic cells that produce hormones that are secreted into the bloodstream.
- pancreatic islets (islets of Langerhans): groups of pancreatic cells secreting insulin and glucagon.
- About one million islets are scattered throughout the pancreas
Main Hormones Secreted From the Pancreas
- Glucagon
- Insulin
- Both hormones are from endocrine cells/endocrine function
Glucogen
- A hormone that signals liver to release glucose from glycogen
- Raises blood sugar
Insulin
- A hormone that signals most body cells to take up glucose from the blood
- Promotes storage of glucose as glycogen in liver
- Lowers blood sugar
Thymus
- Important immune organ
- Located in the lower neck and anterior thorax
- Site at which T-lymphocytes arise from precursor cells
- Primary function is maturation of T Cells
What T cells mature in the Thymus?
- Thymosin
- Thymopoietin
Gonads
- Testes and ovaries are the main sources of sex hormones
Male Gonads
- Interstitial cells secrete androgens, primarily testosterone
Testosterone
- Hormone that promotes the formation of sperm
- Maintains secondary sex characteristics
Female Gonads
- secretes estrogen
Estrogen
- Hormone that controls ovulation
- Maintains secondary female sex characteristics
