Endocrine Flashcards
What is the endocrine comprised of?
Hormones and the glands that secrete them. Some of the glands include the adrenal glands, the hypothalamus in the brain, the pituitary gland, the pancreas, the pineal gland, the thyroid and parathyroid glands, the ovaries and the testes.
How does the endocrine system influence metabolism of cells in the body?
Hormones can increase or decrease the body’s metabolic rate, depending on which side of the autonomic N.S. is turned on at any given time. When the sympathetic N.S. is turned on metabolism increases. When the parasympathetic is turned on, metabolic rate decreases.
What’s a hormone?
A chemical that is secreted in one part of the body (a gland) and then has an effect on other parts of the body. The blood is how hormones are moved from one part of the body to another.
Describe hormones that are amino acid based. Can they cross membranes on their own? Can they travel in the blood on their own?
Most hormones are amino acids. They are polar, which means that they are water-soluble. That means that they are soluble in the blood, so can move through the blood without the help of another molecule. However, they can not diffuse right through cell membranes, which are lipids. So, they need help to cross that barrier. They end up not crossing the cell membrane barrier, but binding to receptors on the cell’s surface.
What’s a target cell and how does it respond to a hormone?
Target cells have receptors for a particular hormone. For example, a cell is a target for insulin if it has receptors for insulin on the cell membrane. Steroid hormones find their cell receptors inside the cell, but there are still receptors.
Hormones made out of amino acids act on cells by binding where?
To a cell receptor on the cell membrane.
Where do hormones that are made out of steroids bind to cells? Why is this possible?
To cell receptors that are inside the cell. This is possible because the steroid hormones diffuse right through the cell membrane.
Describe the 5 steps of cyclic AMP signaling.
First, the hormone binds to receptor in the cell membrane. Second, the receptor now activates a G-protein. The G protein slides along the inside of the cell membrane until it comes into contact with adenylate cyclase. Third, the adenylate cyclase is activated by the G-protein. Adenylate cyclase is an enzyme. G-protein is turned off or deactivated. Fourth, adenylate cyclase converts ATP to cyclic AMP (the second messenger). The hormone itself is considered the first messenger. This happens for as long as the G-protein is attached to adenylate cyclase. Last, cyclic AMP activates protein kinases (these are also enzymes). Protein kinases donate a phosphate to different proteins in the cell. We call this phosphorylation (adding a phosphate). Some of the proteins accepting a phosphorus are enzymes, which then become either activated or deactivated.
Describe how hormones that are lipid soluble act in a cell.
Lipid soluble (steroid based hormones) diffuse right through the membrane of the target cell and bind to a receptor that’s inside the cell. Once this happens, the hormone/receptor complex enters the nucleus and binds to the DNA on the gene that this particular hormone is activating. The gene turns on and then the cell produces the protein that this gene codes for. High levels of this protein will inactivate the hormone.
humor stimuli
Humor refers to fluids. So, humoral stimuli are usually changes of levels of solutes in the blood, which stimulate hormones to be released or deactivated. For example, if calcium levels in the blood start to fall, parathyroid hormone is secreted, as blood sugar levels increase, insulin is secreted, and so forth.
Neural stimuli of hormone release:
nerves stimulate the release of hormones. A good example of this is the stress response. There is a stressful event and nerves stimulate the adrenal gland to produce adrenalin and noradrenalin.
Hormonal stimuli
occurs when hormones are released in response to other hormone levels being either high or low. For example, the pituitary gland releases thyroid stimulating hormone. When levels of this get high enough, the thyroid gland secretes thyroid hormones.
Explain how negative feedback ensures that we don’t make too much of a certain hormone.
There is a stimulus that causes a hormone to be released. The hormone produces some kind of change. The change causes the hormone to stop being made. For example, you eat a meal that has sugar in it. This is the stimulus. Insulin is made by the pancreas. Insulin causes the change of blood sugar levels decreasing. Once blood sugar levels are normal, insulin is not secreted any more.
What determines whether a cell will respond to a hormone or the hormone passes right by that cell, with no effect?
Whether or not the cell has receptors for that particular hormone….whether or not that cell is a target cell for that hormone.
What is up regulation? What causes up-regulation to occur? Give an example. -
Up-regulation occurs when a cell is constantly exposed to low levels of a certain hormone. In this case, the cell will make more cell receptors, so it becomes sensitized, or more sensitive to the hormone. For example, if you don’t eat carbohydrates, or eat very low levels of carbohydrates, then your cells might up-regulate their insulin receptors, so cells become extra sensitive to any insulin that is secreted.
Down regulation? What causes down-regulation to occur? Give an example. -
Down regulation occurs when a cell is over exposed to high hormone levels on an on-going basis. In this case they decrease the number of cell receptors for that particular hormone. In other words, they become desensitized and respond less vigorously to that hormone. For example, if someone eat sugar in high amounts every day, then insulin is secreted often and cells are exposed to insulin quite often (every day, all day).
What is stored in the posterior lobe of the pituitary gland? Where are these hormones made?
Two hormones are stored in the posterior lobe of the pituitary gland. They are oxytocin and anti-diuretic hormone. Both of these are made in the hypothalamus.
What is made in the anterior lobe of the pituitary? What stimulates the anterior lobe to release these hormones into the blood?
There are 6 hormones made in the anterior lobe of the pituitary. The hypothalamus stimulates the release of these hormones, but they are made in the pituitary, not the hypothalamus. The hormones are: growth hormone, thyroid stimulating hormone, adrenocorticotropic hormone, follicle stimulating hormone, luteinizing hormone, and prolactin.
What are the main functions of oxytocin?
Oxytocin stimulates uterine contraction and the let-down reflex during nursing.
ADH
is secreted when you are dehydrated. It helps decrease urine production and retain water in the body.
