15 Endocrine System Flashcards
Endocrine System
secrete their products (hormones) directly into the blood which carries them throughout the body to specific target cells
Endocrine System Response
Causes a slow but prolonged response (versus the nervous system which is fast, short reponse)
Hormones
Chemical signals that allow communication between different cells, body parts and even other animals - usually act at a distance
Peptide hormone
proteins that bind to receptors in plasma membranes causing the formation of cAMP which activates a cascade of enzymes in the cells
Steroid hormones
lipids that enter the cell nucleus and affect gene activity (and thus protein synthesis)
Prostaglandins (hormones)
local hormones that affect neighboring cells and thus are not carried in the bloodstream
Pheromones (hormones)
a chemical hormone signals that pass between and influence behavior of other animals
Action of Peptide Hormones
- hormone binds to receptor on plasma membrane
- binding leads to activation of enzymes, changes ATP to cAMP
- cAMP activates enzyme cascade
- many molecules of glycogen are broken down and enter the blood stream
Action of Steroid HOrmones
lipids from adrenal cortex, ovaries, testis - include aldosterone, testosterone and estrogen
As lipids, they pass through cell membrane and bind to intranuclear receptors - not to membrane receptors
- Hormone diffuses through plasma membrane (lipid solute)
- hormone binds to receptor inside nucleus
- hormone receptor activates synthesis of mRNA
- mRNA moves to ribosomes and protein synthesis occurs
Hypothalamus
located at the base of the brain, regulates internal environment through the autonomic nervous system
- helps control hearbeat, body temp, water balance, controls glandular secretions of pituitary
Posterior Pituitary Gland
Stores ADH (antidiuretic hormone) and oxytocin that are produced by the hypothalamus (gets to posterior via axons)
ADH
antidiuretic hormone
regulates water balance by reabsorbing water from the renal filtrate in tubule back into bloodstream at the kidney
Oxytocin
causes uterine contractions during childbirth and allows milk to be released from breast during nursing
Anterior Pituitary Gland
Controlled by hypothalamic-releasing and inhibiting hormones (e.g. thyroid releasing and inhibiting hormones) via a portal system (2 capillary beds connected by a vein) and frequently uses negative feedback homeostasis
• Six hormones produced by the anterior pituitary:
1. Thyroid-stimulating hormone (TSH): stimulates the thyroid
to produce thyroid hormones
2. Adrenocorticotropic hormone (ACTH): stimulates the adrenal cortex to produce cortisol
3. Gonadotropic hormones: Folicle Stimulating and Leutenizing Hormones (FSH and LH) stimulate gonads (ovary and testicle) to produce sex cells and sex hormones
4. Prolactin (PRL): stimulates mammary glands to develop and produce milk only after childbirth
5. Melanocyte-stimulating hormone (MSH): causes skin cells to produce melanin
6. Growth hormone (GH): promotes skeletal and muscular growth
Too little or too much growth hormones?
• Pituitarydwarfism–toolittleGHproduced
during childhood results in small stature
- Gigantism–toomuchGHproduced during childhood results in large stature but poor health
- Acromegaly–overproductionofGHasan adult results in larger than normal feet, hands, and face
Thyroid Gland
- Alargeglandinnecklocatedbelowthe larynx
- Dietaryiodineneededbythethyroidto produce its hormones
• Thyroid produces:
– Thyroxine (T4) and Triiodothyronine
(T3): both regulate metabolism
– Calcitonin: helps lower blood Calcium levels by stimulating the deposition of calcium in bones
Thyroid Abnormalities
Simple goiter – thyroid enlarges because of increased TSH from Ant. Pituitary, due to lack of iodine in the diet (causing not enough thyroid hormones T3 and T4)
•_ Hypothyroidism_ – low blood levels of thyroid hormonesA. Congenital hypothyroidism: A child’s thyroid does not develop properly - characterized by a short, stocky person that may be mentally retardedB. Myxedema: hypothyroidism in adults characterized by lethargy, weight gain, loss of hair, cold intolerance and thick, puffy skin
• Hyperthyroidism – excess thyroid hormones in the blood
A. Exophthalmic goiter: such as seen in Graves’ disease - is characterized by enlargement of the thyroid gland, protrusion of the eyes, hyperactivity and insomnia
B. Thyroid tumor: can also cause hyperthyroidism
Parathyroid Glands
• Usuallyfoursmallglandsembeddedinor near the surface of the thyroid gland
• Produceparathyroidhormone(PTH):
– causes blood calcium level to increase by promoting osteoclast activity to break down bones (releasing calcium)
– Promotes reabsorption of calcium by the kidneys
Adrenal Glands
Adrenals have two parts
– Adrenal medulla: inner portion, controlled by the
nervous system
– Adrenal cortex: outer portion, controlled by adrenocorticotrophic hormone (ACTH) from the anterior pituitary gland
Adrenal Medulla
• Innerportionoftheadrenalglands
• Vianeurons(nothormones),thehypothalamus stimulates the adrenal medulla to produce its
own hormones that allow a rapid, (but not as fast as neural) short-term response to stress: This is termed “Fight or flight”
– Epinephrine (adrenaline)
– Norepinephrine
Adrenal Cortex
- Outer portion of the adrenal glands
- Stimulated by ACTH (hormone) from anterior pituitary, adrenal cortex produces its own hormones that provide a slow but long-term response to stress
Mineralocorticoids : regulate salt and water balance • e.g. aldosterone (reabsorbs Na+ at the kidney)
Glucocorticoids : regulate carbohydrate, protein and fat metabolism, e.g. cortisol and cortisone
• Promote breakdown of muscle protein to amino acids, which liver converts to glucose, and increases metabolism of fatty acids, sparing glucose
• Suppresses the body’s inflammatory response
Adrenal Gland Malfuction
Addison’s disease – hyposecretion of glucocorticoids
by the adrenal cortex causes “bronzing” of the skin
Pancreas
Composed of 2 separate tissues:
– Exocrine: produces and secretes digestive juices via duct into duodenum (amylase, lipase, trypsin, etc.)
– Endocrine: (islets of Langerhans): produces and secretes hormones into blood
- Insulin – secreted when blood glucose is too high - stimulates uptake of glucose by muscle and liver cells (which lowers blood glucose)
- Glucagon – secreted when blood glucose is too low - stimulates the breakdown of glycogen in the liver to glucose (which raises blood glucose
What is diabetes mellitus?
Inability to control blood glucose levels
• Two types: Type 1 and Type 2 (used to be called Juvenile and Adult Onset Diabetes, but now so many overweight kids have “adult onset,” the names had to be changed!)
• 20 million people in the US have diabetes – up to 100 million are at risk of getting it (nearly 1/3 US population)
• General symptoms:
– Frequent urination
– Unusual hunger and/or thirst
– Unexplained change in weight
– Blurred vision
– Sores that heal slowly or not at all – Excessive fatigue
Long-term effects all caused by vascular disease (atherosclerosis): blindness, loss of limbs, nerve
deterioration, kidney failure, heart disease.
