PART 3 Flashcards
Endocrine System
is a set of organs that secretes hormones directly into the circulatory system
Hormones regulate many of the processes in the human body
Relies upon blood circulation to transport hormones, chemical messengers secreted by ductless glands, to the cells and organs on which they have an effect (target sites)
Because blood flow is employed to transmit hormones from gland to target organ, it takes longer for a hormone-releasing stimulus to cause a regulatory response than it takes the neurons of the nervous system but they stay in the blood stream after a neurons signal has ended so they have a prolonged duration compared to the nervous system.
Epinephrine
also known as adrenaline released from the adrenal glands cant innate a quick accident avoiding car maneuver as the nervous system can but for a period of time after the incident, the hormone promotes a cautionary alert mode of the sympathetic nervous system.
Endocrine Glands
Do not have associated ducts
Exocrine Gland
salivary gland is one that delivers its secretions by a tube to an epithelial surface or mucosa.
An example of the external secretions is pancreatic amylase that digests starch in the small intestine.
they do not secrete hormones these are not hormones
Pancreas
Is a unique among organs in the body, because it secretes both enzymes and hormones.
One endocrine role of the pancreas is to release insulin, a hormone that triggers the uptake of glucose into cells, thus lowering blood glucose levels.
Feedback systems
The same cells of the pancreas that secrete insulin also detect levels of glucose
These beta cells are able to adjust the amount of insulin they secrete in proportion to the amount of blood glucose they detect.
Alpha cells of the pancreas are also able to detect blood glucose levels and when they are low alpha cells secrete a different hormone GLUCAGON to help it.
Glucagon
This hormone stimulates its target cells in the liver to convert hepatic glycogen stores into glucose and release that glucose into the blood.
Negative Feed back
Both kinds of pancreatic cells producing each of these hormones regulate blood sugar amounts through negative feed back and hormone secretion is stopped when a homeostatic level of blood glucose is detected.
Diabetes is a disease that results from a pancreatic hormone regulation malfunction.
Most hormone levels in the body are regulated through negative feedback whether a specific hormone is secreted is often influenced by the production of a releasing hormone or an inhibiting hormone.
HYPOTHALAMUS
is a location in the brain that is integration center between the endocrine and nervous system
produces releasing hormones that stimulate and inhibiting hormones that restrict the production of several hormones produced by the anterior pituitary
For example, the anterior pituitary secretes growth hormone, whose production but the anterior pituitary is stimulated or suppressed by specific releasing hormones or inhibits hormones secreted by the hypothalamus. If the influence of these hypothalamic hormones is ignored by the anterior pituitary, for instance due to a benign tumor in the pituitary overriding the effects of growth hormone-inhibiting hormone GHIH and gigantism can result because the secretion of growth hormone by the anterior pituitary fails to stop
Negative Feed back between Pituitary Gland and Thyroid gland
because thyroid hormone plays a role in regulating growth , development, and metabolic rate, homeostatic levels of TH blood levels are necessary
Thyroid hormone’s release from the thyroid gland is initiated by an anterior pituitary secretion called TSH
the release of TSH is triggered by the presence of Thyroid releasing hormone secreted by the hypothalamus
The presence of TH in the bloodstream causes negative feedback inhibition on the release of both TSH(from the pituitary) and TRH (from the hypothalamus)
a malfunction of these regulatory feedback loops leads to an overproduction of thyroid hormone and is called hyperthyroidism. (weight loss, anxiety, and rapid heartbeat)ss
Positive Feedback
only a few situations where positive feedback of hormone secretion takes place in the body
Positive feedback causes an increase in the secretion of a hormone, rather than cessation at a homeostatic set point or range.
Occurs during labor when oxytocin a chemical produced by the hypothalamus and stored in the posterior pituitary which stimulates uterine contraction that help push the fetus and this positive feedback continues until the baby is out
FSH
the target sites of some hormones are at considerable distance from the glands that release them.
FSH, which is secreted by the anterior pituitary, stimulates development of eggs in ovaries and sperm in testes.
also stimulates the production of the ovaries primary hormonal secretion estrogen
Steroid Hormones
are fat soluble hormones and are made from cholesterol, their lipid composition allows them to pass easily through cell membranes and nuclear membranes.
Nonsteroid Hormones
are water soluble hormones and the receptor sites of non steroid hormones are on the outer surface of the target cells membrane.
water soluble hormones cannot pass between phospholipid of the cell membranes instead they bind to cell surface receptors which are proteins embedded in the target cell membrane.
Binding of hormone to receptor triggers changes in the receptor that signals molecules within the target cell and these internal signals initiate a network of chemical reactions within the target cell, leading to specific metabolic effects.
Thymus
has an immune function
Nonsteroid hormone
a gland located behind the manubrium in adults, and is larger in children until about 6 years of age.
this gland is also a lymphoid organ and it is placed where the immune system’s t cells are produced.
Parathyroid (PTH)
non steroid and is produced in the parathyroid a small grouping of usually four bean-shaped endocrine glands on the doral aspect of the thyroid gland.
Secretes PTH when plasma calcium levels are low (hypocalcemia)
plays a role in regulation of plasma calcium levels
indirectly activates osteoclast causing the resorption of calcium from bones
also works in the excretory system to increase plasma calcium levels inhibiting the kidneys ability to transfer calcium ions to urine.
Urinary System
The organs of the urinary system function in the processing and excretion of fluids from the body
Kidneys
The primary organ of the urinary system
includes structures where blood is filtered, locations where filtered material can be reabsorbed by blood and places where what is not reabsorbed collects as urine.
In addition to blood vessels that bring blood to and from the kidneys, a system of tubes allow for collection and reabsorption of filtrate, the collection of urine from the kidneys, urine storage, and its excretion.
Kidneys Anatomy
The functional units of the kidney are miscroscopic nephrons
The kidney is divided into two major regions: the renal cortex which surrounds an area called the renal medulla. Within the cortex, is the glomerulus of the nephron. The glomerulus is a network of capillaries where blood pressure pushes water, salt, glucose, amino acids, and urea from the blood.
Filtrate
All of the material leaving the blood through the walls of the glomerular capillaries is called the filtrate.
Filtrate is collected by the Bowman’s capsule which surrounds the glomerulus.
Filtrate from the bowman’s capsule
Filtrate moves into a highly convuluted tubule before dipping down into the level of the kidneys medulla.
The proximal tubule is where glucose and other useful solutes are reabsorbed back into the blood through the walls of surrounding capillaries.
After the proximal tubule dips down into the renal medulla and the remaining filtrate flows through the switch back bend of the loop of Henle then continues back into the cortex through the distal tubule. The loop of Henle and the distal tubule are also sites of tubular reabsorption the movement of useful material from filtrate back into the blood stream.
Tubular Reabsorption
Happens in the loop of Henle and distal tubule
Osmotic pressure causes more than 80% of the water in filtrate to return to the blood plasma.
Additional water is reabsorbed from filtrate that has continued from the distal tubule into the collecting duct.
Final opportunity for Water reabsorption
In the renal cortex, distal tubules from numerous nephrons empty into each collecting duct and as the collecting ducts transport the contained liquid on its second journey through the medulla the remaining filtrate has its final opportunity for water reabsorption.
and here the remaining filtrate becomes more concentrated as urine.
Collecting ducts join and empty their urine into the renal pelvis of the kidney.
