mod 2: The Endocrine System Flashcards
set point (definition)
“set value”. ideal/optimum conditions
negative feedback (definition)
mechanism where diversion from set point causes return to set point–leads to stability
positive feedback (definition)
mechanism where deviation from set point causes further deviation–leads to instability
hormone (definition, function)
chemical messenger circulating in the blood stream. produced by specialized cells. coordinates various parts of the body by interactive with target cells
target cell (definition)
cells with specialized receptors designed to react only with specific hormones
endocrine gland (definition)
cell, tissue, or organ that produces hormones directly into the blood stream (ductless)
exocrine gland (definition)
cell, tissue, or organ that produces hormones that are moved through ducts or channels
lipid-soluble hormone (definition)
hormone that is chemically identifiable as a lipid or steroid
water-soluble hormone (definition)
hormone that is chemically identifiable as an amino acid or protein
antagonistic hormones (definition)
two hormones that produce opposite effects (ex: insulin and glucagon)
tropic hormone (definition)
hormone that acts on another endocrine gland and causes it to produce another hormone. a hormone whose target cell is another endocrine gland
gonadotropic hormone (definition)
affect reproductive organs (gonads)
hypothalamus (structure, function)
connected to the pituitary gland by a thin stalk and controls the pituitary through “releasing hormones” (this is what they are called) that are carried to the anterior pituitary through a series of blood vessels that go through the stalk. secretes hormones some hormones that it then transfers through neural axons and stores in the posterior pituitary
posterior pituitary (structure, definition, secretions)
the half of the pituitary that faces inwards toward the brain. part of the nervous system. does not produce any hormones itself, only stores hormones produced by the hypothalamus.
SECRETES:
- antidiuretic hormone (ADH) (also called vasopressin)
- oxytocin (OCT)
anterior pituitary (structure, definition, secretions)
the half of the pituitary that faces outwards away from the brain. actually produces hormones SECRETES: - human growth hormone (hGH) - prolactin (PRL) - thyroid-stimulating hormone (TSH) - adrenocorticotropic hormone (ACTH) - follicle-stimulating hormone (FSH) - luteinizing hormone (LH)
diabetes insipidus (definition, cause)
condition where excessive production of very dilute urine occurs. caused by lack of ADH due to hypothalamus failing to produce it or by posterior pituitary failing to release it
releasing hormones (definition, function)
“releasing factors”. hormones produced by neurosecretory cells in the hypothalamus. stimulate or inhibit the secretion of hormones by the anterior pituitary. tropic hormones
hGH (function, effects of abnormal production)
“human growth hormone”
FUNCTION: increases protein synthesis, cell division and growth (especially of cartilage, bone, and muscle), and metabolic breakdown and release of fats stored in fat tissue.
EXCESS: in childhood, causes gigantism. in adults, causes acromegaly
DEFICIENCY: in childhood, causes pituitary dwarfism
gigantism (definition, cause)
a condition where a child will grow extremely quickly and without stopping (reaching a height of 8ft or more. caused by overproduction of hGH during childhood
acromegaly (symptoms/effects, cause)
EFFECTS: bones and soft tissue widen. face widens, ribs thicken, feet and hands enlarge, risk of cardiovascular disease, sugar intolerance, breathing problems, muscle weakness, colon cancer, extreme headache, coarse facial features (prominent forehead, enlarged nose and tongue and lips, widely-spaced teeth), enlarged heart and liver and kidneys, fatigue, excessive perspiration, visual disturbances.
CAUSE: overproduction of hGH in adulthood
pituitary dwarfism (definition, cause)
a condition where a person grows very little in childhood but has normal proportions, caused by insufficient hGH production in childhood
adrenal gland (location, structure)
located on top of the kidneys. made up of an outer layer (the adrenal cortex) and an inner mass (the adrenal medulla), where both parts secrete different hormones and are within the adrenal capsule (outside covering)
adrenal medulla (definition, secretion)
modified nerve tissue of the sympathetic nervous system. not stimulated by hormones from the pituitary, stimulated directly by the hypothalamus though the nervous system so it acts very quickly.
SECRETES:
- epinephrine
- norepinephrine (doubles as a hormone and a neurotransmitter)
in roughly 4:1 ratio
adrenal cortex (definition, secretion)
not nervous tissue. acts slower than the medulla. SECRETES: - glucocorticoids (cortisol) - mineralocorticoids (aldosterone) - gonadocorticoids
short-term stress response (definition, secretion, effects)
“fight or flight”. prepares the body for immediate action.
SECRETIONS: roughly 80% epinephrine and 20% norepinephrine by the adrenal medulla. cortisol secreted by the adrenal cortex may enhance the response.
EFFECTS: very similar to the effects of the sympathetic nervous system but last 10x as long. involves: increase in breathing rate, heart rate, blood pressure, blood flow to heart and muscles, and blood glucose (increased conversion of glycogen to glucose in the liver) and decreased blood flow to extremities and dilation of pupils. cortisol assists with the increase of blood glucose
cortisol (definition, location, function)
the most important glucocorticoid. secreted by the adrenal cortex due to stimulations by ACTH from the anterior pituitary.
FUNCTION: raise blood glucose levels by prompting breakdown of muscle protein into amino acids (which are taken to the liver and used to make glucose) and prompting breakdown of fat cells. natural anti-inflammatory
glucocorticoid (definition, location, function)
group of hormones produced by the adrenal cortex that influence glucose metabolism from protein and fat and influence immune function by suppressing inflammation. cortisol is a glucocorticoid
long-term stress response (definition, secretion)
responses, mainly stimulated by cortisol, that are of long duration.
mineralocorticoid (definition, location, function)
hormone produced by the adrenal cortex. regulates salt and water homeostasis by influencing the reabsorption of Na+ ions in the kidneys. aldosterone is a mineralocorticoid
aldosterone (location, function)
secreted by the adrenal cortex.
increases permeability of tubes in the nephrons of the kidneys to sodium, increasing its reabsorption, and causing it to pull an increased amount of water with it as well, increasing blood pressure.
thyroid (location, structure, secretion)
LOCATION: directly below the larynx (voice box)
STRUCTURE: two lobes on either side of the trachea, connected by a narrow band of tissue. tissue contains follicles, consisting of a layer of secretory cells surrounding a storage space. large cells (“c cells” or “parafollicular cells”) are present between the follicles, which are like tiny, hollow spheres
SECRETION:
- thyroxine
- calcitonin
precursor (definition)
an inactive form of a molecule that can be changed easily into the active form
thyroxine (produced by, function)
PRODUCED BY: follicle cells of the thyroid gland. thyroglobulin combines with iodine in the follicle cell cavity to create thyroxine.
FUNCTIONS: mainly controls the rate at which the body metabolizes carbohydrates, fats, and proteins for energy, as well as stimulates the proper development of the nervous system. produces enzymes that carry out cellular respiration. more thyroxine = more enzymes = faster cellular respiration = more energy
calcitonin (produced by, function)
PRODUCED BY: parafollicular cells (C cells)
FUNCTIONS: decreases blood calcium levels by increasing uptake of calcium into bones and inhibiting decomposition of bones when blood calcium levels are too high.
antagonistic hormone pair to PTH
hypothyroidism (definition, symptoms, conditions)
a condition where not enough thyroxine is being secreted due to issue with the gland or deficient iodine consumption.
SYMPTOMS: low energy, lethargy, feeling cold, sleepy, difficulty talking, depression, goitre
CONDITIONS:
- myxoedema: form of hypothyroidism in adults
- cretinism: form of hypothyroidism in infants and young children
hyperthyroidism (definition, symptoms, conditions)
a condition where an excess of thyroxine is being secreted
SYMPTOMS: anxiety, insomnia, heat intolerance, irregular but strong heart rate, weight loss, goitre
CONDITION: Grave’s disease: autoimmune disorder where the immune system attacks the thyroid. severe hyperthyroidism. causes swelling in muscles around eyes, resulting in eye bulging
goitre (definition, types)
enlargement of the thyroid gland that is large enough to be noticeable without any special equipment.
ENDEMIC: caused by lack of iodine
EXOTHALMIC: caused by overactivity of the thyroid gland due to overstimulation
parathyroid (location, definition, secretion)
four small glands attached to the thyroid. produce parathyroid hormone (PTH)
parathyroid hormone
“PTH”. stimulates bone cells to break down material and blood to reabsorb Ca2+. stimulates kidneys to reabsorb Ca2+ from urine, also activating vitamin D in the process, which stimulates reabsorption of Ca2+ in the intestines. antagonistic hormone pair with calcitonin.
pancreas (structure, secretion, function)
STRUCTURE: scattered throughout the pancreas are islets of Langerhans, clusters of alpha cells (which are closer to the outside of the islet) and beta cells (which make up the centre).
SECRETIONS:
- alpha cells secrete glucagon
- beta cells secrete insulin
islets of Langerhans (definition)
clusters of alpha and beta cells that secrete glucagon and insulin into the blood
beta cells (definition)
cells in the islets of Langerhans in the pancreas that secrete insulin
insulin (produced by, function)
PRODUCED BY beta cells in islets in the pancreas.
LOWER BLOOD GLUCOSE BY acting on receptors of target cells and making them more permeable to glucose, allowing those cells to use it for energy (especially effects muscle and liver cells), and convert it to fat or glycogen for storage.
alpha cells (definition)
cells in the islets of Langerhans in the pancreas that secrete glucagon
glucagon (produced by, function)
PRODUCED BY alpha cells in islets in the pancreas.
RAISE BLOOD GLUCOSE BY stimulating the liver to turn glycogen back to glucose and stimulating breakdown of fat into glucose
diabetes mellitus–type I (onset, definition, treatment)
juvenile, insulin dependent. a chronic condition where the immune system attacks beta cells so they become unable to produce insulin. treated with daily insulin injections
diabetes mellitus–type II (onset, definition, treatment)
adult-onset, non-insulin-dependent. develops gradually. insulin receptors on cells stop responding to insulin or beta cells produce less and less over time. linked closely to unhealthy diet and weight gain. can turn into type I if not dealt with. treated with diet, exercise, and oral medication.
what are the symptoms of diabetes? explain how high blood glucose levels can cause them. what are some more serious, long-term symptoms?
without insulin, cells remain relatively impermeable to glucose and cannot obtain enough from the blood (this causes fatigue); the body tries to compensate by switching to protein and fat metabolism for energy, the breakdown of which is harder and may release kerosine (this can be smelled on the breath and smells like nail polish remover); the kidneys are incapable of reabsorbing that much glucose so it is excreted with the urine, changing the osmotic gradient and dragging water with it (this causes dehydration and large quantities of sweet urine).
LONG-TERM SYMPTOMS: leads to blindness, kidney failure, nerve damage, and gangrene in the limbs
hyperglycaemia (definition)
condition caused by high levels of blood glucose. occurs in people with diabetes mellitus
hypoglycaemia (definition)
condition caused by low levels of blood glucose. occurs in people who secrete and excessive amount of insulin when a tumour develops in the beta cells or in diabetics who have injected too much insulin
compare the endocrine and nervous systems
- endocrine typically has slower and longer-lasting effects, and affects a broader range of cell types
- some nervous system tissues secrete hormones (hypothalamus, adrenal gland)
- several chemicals function as neurotransmitters and hormones (norepinephrine and epinephrine)
- endocrine and nervous systems are included in responses regulated by negative feedback loops
- regulation of several physiological processes involves both systems working together (such as breastfeeding)
TSH (secreted by, function)
“thyroid stimulating hormone”
secreted by the anterior pituitary.
stimulates the thyroid.
ACTH (secreted by, function)
“adrenocorticotropic hormone”
secreted by the anterior pituitary.
stimulates the adrenal cortex.
FSH (secreted by, function)
“follicle stimulating hormone”
secreted by the anterior pituitary.
stimulates production of ova and sperm from the ovaries and testes.
LH (secreted by, function)
“luteinizing hormone”
secreted by the anterior pituitary.
stimulates sex hormone production from the ovaries and testes.
PRL (secreted by, function)
“prolactin”
secreted by the anterior pituitary.
stimulates milk production (but not secretion) from the mammary glands
OCT (secreted by, function)
“oxytocin”
secreted by the posterior pituitary.
stimulates uterine muscle contractions and release of milk by the mammary glands.
estrogen (secreted by, function)
secreted by the ovaries.
stimulates uterine lining growth and promotes development of the female secondary sex characteristics.
progesterone (secreted by, function)
secreted by the ovaries.
promotes growth of the uterine lining and prevents uterine muscle contractions.
testosterone (secreted by, function)
promotes sperm formation and development of the male secondary sex characteristics
ADH (secreted by, function)
“antidiuretic hormone”
secreted by the posterior pituitary.
promotes the retention of water by the kidneys.
