Kinesiology 04
Terms
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- factors controling insulin and glucagon
- during exercise or stress, increased epinephrine stimulates liver glucose production, pancreatic glucagon production, and insulin inhibition.
- negative feedback
- maintenance of constancy of a set variable through signals which trigger mechanisms to return normalcy should a variance in set variable occur.
- glucagon
- hormone secreted by the Alpha cells of the pancreas which stimulates increased glucose levels in the blood.
- adrenal cortex
- outer portion of adrenal gland. secretes steroids, especially cortisol.
- somatostatin
- secreted by pancreas, controls secretion of both insulin and glucagon - control mechanism.
- normal glucose level
- 90 mg/100ml plasma
- exocrine gland
- empty their secretions into ducts that empty to the outside of the body: sweat glands, salivary glands, and digestive glands of the pancreas. Secretions are directed into ducts, which then empty their contents outside the body.
- second messenger
- the chemical released when the first messenger hormone acts on the cell. The second messenger causes events to happen within the target cell.
- peptide hormone
- eg: oxytocin. water soluble, circulate in the blood plasma, use receptor molecules. composed of amino acids, from 3 or 4, to hundreds in a chain. can be very similar in structure, with very different functions/effects.
- amines
- hormones. derivatives of the amino acid tyrosine - quite small molecules. Norepinephrine is an amine hormone.
- steroid hormone
- lipid soluble. carried in plasma by a carrier molecule. don't need a receptor molecule to enter cell. derived from the cholesterol molecule, secreted by many reproductive glands and adrenal gland. again, can be very similar to each other, with very different effects.
- cAMP
- second messenger hormone called cyclic AMP. causes the specific effect within the cell a hormones first messenger has targeted.
- hormone
- a chemical secreted into the blood by a gland and carried to its target via the bloodstream. there are three types of hormones: peptide, amine, and steroid. Regulate physiological processes and are released in response to a physiological change in state.
- target cell.
- the cell which the steroids take effect on.
- hyperglycemic response
- increase insulin, decrease glucagon. (decrease blood sugar.)
- hyperglycemia
- above normal concentrations of blood glucose
- cortisol
- the body's major glucocorticoid hormone, making up over 90% of the glucocorticoids secreted by the adrenal glands. Cortisol is a "permissive" hormone, that is, when it expresses itself, it allows a different hormone to function. It works to control cell metabolic activity and protein synthesis. It is used in medicine as an anti-inflammitory, although the precise reason why it functions as such is not well understood.
- anterior pituitary gland
- chemically controlled secretions via veinous blood from hypothalamus. forward portion of the pea-sized gland at the base of the brain.
- hypoglycemic response
-
increase glucagon, decrease insulin.
(increase blood sugar.) - positive feedback
- takes set variable further away from normal.
- adrenocortical hormones
- from adrenal cortex. mineralcorticoids and glucocorticoids. generally secretion of adrenocortical hormones controlled by other hormones. stress increases adreoncortical hormone secretion.
- mineralcorticoids
- steroids that regulate sodium and potassium levels in body. Aldosterone - main example - acts on kidney, increases Na+ retention, stimulates K+ secretion, thus determines blood volume.
- Type I diabetes
-
juvenile onset.
Insulin dependent.
pancreatic deficiency.
insufficient insulin production.
must use insulin. - trophic hormone
- a hormone that stimulates secretion of a second hormone.
- three main classes of hormones
-
peptide: water soluble, circulate in blood, use receptor molecules
amines - small molecules, derivitives of tyrosine, eg: norepinephrine.
steroids: lipid soluble, carried in plasma by carrier molecule. don't need receptor molecules. derived from cholesterol. - Type II diabetes
-
non-insulin dependent.
adult onset
pancreas and insulin production fine, but receptor and target cell unresponsive or post-receptor defect.
can be regulated with diet. - insulin
- protein hormone secreted by the beta cells of islets of langerhans of the pancreas. controls blood sugar glucose concentration (brain's energy source, of which constant supply is req'd, as brain can't store it.) insulin acts on cellular membranes, esp. striated muscle cells, to facilitate glucose uptake into cells, removing it from the blood.
- ACTH
-
adrenocorticotropic hormone.
stimulates the adrenal cortex to secrete hormones. it is released from teh anterior pituitary. control of ACTH is dependent on CRH in blood. ACTH release from AP signal comes from hypothalamus. - cushings syndrome
- hypersecretion of adrenal steroids. (can be caused by adrenal or pituitary tumors). excess NaCL + H2o retention, excess cortisol = increased appetite, increased glucose, decreased usage= increased FAT, increased male hormones = incr. masculinization.
- control of hormone secretion
- all endocrine glands can be stimulated to incr. hormone production. some stimulated directly by neurons, others by chemical.
- target cell receptor
- for hormones to take effect within a cell to change the rate of synthesis for certain proteins, the hormone must first attach itself to a receptor molecule on the membrane of its target cell: the target cell receptor. This is because the solubility of most hormones makes it such that they can not enter the cell without the means of the receptor, which could be considered a type of chemical "lock" which can allow the hormones in, or not, depending upon the hormone "key." Neither steroid hormones nor thyroid hormones require target cell receptors to enter a cell, however they must, once in the cell, join with a receptor molecule in order to be carried to the nucleus to effect protein synthesis therein.
- pancreas
- gland which secretes hormones which control blood glucose levels.
- adrenal medulla
- inner portion of the adrenal gland - contains epinephrine and norepinephrine.
- glucocorticoids
- ssecreted during stress, type of hormone that acts to control metabolic activity, also are permissive hormones, allow others to do their job (i.e. epinephrine as vasoconstrictor when cortisol present.)
- sources of plasma glucose
- uptake directly from food digestion by intestines, liver breaks down stored glycogen into glucose
- diabetes mellitus
- lack of insulin or inability of target cells to respond to insulin, causing incorrect levels of blood glucose, which can alter other cell functions. decreased glucose uptake can cause increased fat uptake, with acidic keytone byproducts, causing acidosis (which causes death in diabetics.) Constant urination in the attempt by the body to remove excess ions can, called osmotic diuresis, can cause severe dehydration.
- aldosterone
- an important hormone which helps to regulate the volume of blood within the body by regulating the sodium retained and the potassium secreted by the kidneys, thus maintaining the blood volume by regulating the specific chemicals which effect blood volume. Aldosterone is a mineralcorticoid hormone, released by the adrenal gland cortical layer, and it acts upon the kidneys.
- glucocorticoid effects
-
stimulate protein breakdown
increase response to catecholemines
inhibit glucose uptake
increased release of fatty acids
increase glucose production. - endocrine glands
- have no duct system, produce and secrete hormones directly into the interstitial space, unlike exocrine glands.
- posterior pituitary gland
- rear portion of pituitary gland at base of skull. storage for hypothalamus hormones, hypothalamus directly controls secretions via neurons. (electrical signals.)
- infundibulum
- attaches pituitary to base of the brain.
- gonadotropins
- Regulatory tropic hormones (that is they stimulate - or "nourish" the release secretion of other hormones) secreted by the anterior pituitary gland, gonadotrophins in turn regulate the secretion of other hormones that the ovaries and the testicles produce.
- hGH
- human growth hormone. regulates growth of uhuman body cells and bone. naturally decreases by abt. 25% after puberty but is released throughout life. required for normal growth, excess causes excess growth and vice-versa.
- acromegaly
- thickening of bones and increased soft tissue growth due to increased secretion of hGH after puberty. (can be caused by pituitary tumor). internal organs, hands, feet, face enlarge, changes facial char. dramatically.
- thyroid gland
- located in neck, richly supplied with blood, contains many sacs called follicles contain thyroid hormones. takes up iodine from blood and synthesizes iodine containing hormones.
- thyroxine
- hormone with no single target cell. stimulates metabolic rates of each cell entered. determines basal metabolic rate of humans.
- TSH
- thyroid stimulating hormone. from the anterior pituitary, stimulates TH release from thyroid follicles.
- TRH
- Thyrotropin releasing hormone, from hypothalamus, stimulates secretion of TSH from anterior pituitary
- iodine
- A natural substance contained in trace amounts in the body, which when absent, causes a thyroid gland enlargement called goiter. When iodine is given to patients with this condition, the goiter may shrink or disappear. Iodine is added to table salt (iodized salt) as a means of ensuring intake of iodine in the human diet.
- hyperthyroidism
- causes increased metabolic rate, heart rate, body temperature, overactivity, weight loss, nervousness. Bulging eyes due to excess fluid and tissue storage behind eyes.
- parafollicular cells
- release calcitonin, hormone that lowers calcium levels in blood plasma, secreted by parafollicular cells. Acts on kidney and bone. Kidney increases excretion of calcium, bone ceases release of Ca++ to bloodstream.
- vitamin D
- stored in inactive form in Kidney. Kidneys can create active form from stored form. when released into bloodstream, increased Vitamin D causes intestines to increase uptake of calcium.
- parathyroid hormone (parathormone)
- PTH. peptide hormone secreted from parathyroid glands. regulates calcium balance through negative feedback. increases Ca++ levels in blood: Kidney makes more active Vit.D which increases intestinal uptake of Ca++ into system, Bone - more Ca++ into bloodstream, Kidney, more Ca++ absorbed from renal tubules.
- difference between how a peptide hormone (insulin) and a steroid hormone (cortisol) acts on target cells
-
Insulin = effects cells directly.
cortisol = permissive. causes another hormone to do its job. (ADH/Vasopressin.) - Sim/Diff between ACTH & GH: function, production site, secretion control.
-
- both produced in the anterior pituitary gland
- both travel to their target areas through the bloodstream
- In response to stress, ACTH stimulates the adrenal cortex to secrete hormones. one hormone controls another, and has a specific triggering mechanism.
- hGH, is released throughout life, particularily in the early phases of development. If secreted in normal amounts after adulthood, it doesn't result in change in size of the individual. This happens only when abnormally large amounts of hGH are secreted. hGH is not released in response to a specific mechanism, nor does it specifically act on another organ to control the release of a second hormone. Instead, hGH directly effects the growth and development of body cells and bone cells.
Lastly, the secretion of ACTH is regulated both by hypothalamus neural input, and adrenal gland secretions as a negative feedback mechanism. The production of corticotropin releasing hormone (CRH) by the hypothalamus causes an increase in ACTH output. By contrast, as mentioned before, hGH is released throughout life, but is naturally reduced (probably by the hypothalamus) when adulthood is reached. - negative feedback loop: TSH, TRH, TH
- brain centres/environmental challenges-->stimulates hypothalamus to release TRH-->stimulates Ant.Pit. to release TSH--> stimulates thyroid follicles to release TH into blood --> biological effects of TH, plus TH in blood feeds back to Hypothalamus to inhibit release of TRH. diag p137.
- compare/contrast structure and function of anterior and posterior pituitary glands.
- both secrete hormones, both receive signals from hypothalamus. but ant via blood (chemical) and post. direct via nerve (electrical). posterior enervated by neural elements from hypothalamus, posterior stores hypothalamic hormones, transferred from hypothal --> post.pit via neurones. posterior releases hormones based on signals from hypothalamus. Ant. pit creates and secretes own set of hormones, mostly tropic, and some target cell metabolic rates.
- what happens when a piece of bread has been absorbed as glucose in the small intestine and is circulating in the bloodstream?
- with dig. of bread, absorption of its glucose into the intestine, sensed increase in blood glucose levels, causes the pancrease to increase insulin secretion, allowing for increased glucose uptake into the striated muscles. at the same time, levels of glucagon in blood lower. combination of incr. insulin prod. & decr. glucagon in reaction to incr. glucose in plasma are what keep blood glucose at the correct level.
- what is the relationship between PTH, calcitonin, vitamin D, and plasma calcium levels?
-
together they work, through negative feedback systems, to regulate and maintain calcium levels in the blood. For example, the hormone calcitonin, which the thyroid glands produce, can cause calcium levels in the blood plasma to drop. If the calcium level in the blood decreases, this reduces the glandular inhibition of the parathyroid portions of the thyroid gland, causing them to increase parathyroid hormone (PTH) production. This PTH is released into the blood, where it circulates through the body. When PTH reaches the kidney, it causes the kidney both to retain more calcium (thus reducing the loss of calcium through urine) and also to activate an enzyme which produces an active form of vitamin D. The presence of the active form of vitamin D within the body causes the intestines to absorb more calcium. PTH also directly effects the bones, causing them to release calcium from the bone directly into the blood. These effects of PTH on the kidney, bone, and intestines causes a net increase of calcium in the bloodstream, which then produces a negative feedback reaction of the parathyroid glands, to increase their glandular inhibition, and therefore to decrease the level of parathyroid hormone produced and returning the body to homeostasis.
Conversely, if there is a calcium increase in the blood, the thyroid produces additional calcitonin, to reduce the calcium plasma levels by increasing the excretion of calcium from the kidney, and by reducing dissolution of the bone (which, as explained above, increases plasma calcium levels.) - patient displays excess cortisol secretion. what factors could be measured in a blood sample to determine whether the condition is caused by a defect at the hypothalamic anterior pituitary level or the adrenal cortex level?
-
In a blood sample, the levels of Adrenocorticotropic hormone (ACTH) glucose could be measured, to see whether these are a hypothalamic-anterior pitiutary level input, causing the excess adrenal cortex output of cortisol.Excess cortisol output reduces the usage of glucose, thereby causing an increase in blood glucose. Excess CRH also causes high levels of ACTH, triggering the excess production of glucocorticoids by the adrenal cortex. Suspect the hypothalamus then and a hypothalamic-anterior pituitary level condition.
If there is not excess glucose, but still high levels of ACTH causing excess glucocorticoid production by the adrenal cortex, then also suspect a hypothalamic-anterior pituitary level condition. However, if neither too much ACTH, nor glucose are found in the blood plasma sample, then suspect that the condition is at the adrenal cortex level. - What underlying defect could be responsible for these symptoms? female, menstrual periods cease, excessive facial hair, very thirsty, frequent urination.
- hypersecretion of adrenal steroids caused by an adrenal or pituitary tumor, leading to increased levels of male sex hormones, cortisol, reduced glucose usage. This would cause the masculinization, the excess urination and thirst.