Exam Important Terms

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Homeostasis

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Theprocess by which the body’s substances and characteristics (such as temperatureand glucose level) are maintained at their optimal level. Important because ifthings are not constantly regulated, you can die

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Systemvariable

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• A variable that is controlled by a regulatorymechanism; Whatever you are measuring; for example, temperature in a heatingsystem.

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Set point

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Theoptimal value of the system variable in a regulatory mechanism.-numbed

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Detector

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• : Ina regulatory process, a mechanism that signals when the system variabledeviates from its set point. (Detector here is the thermostat. It is detectingthe temperature)

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Correctional Mechanism

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Ina regulatory process, the mechanism that is capable of changing the value ofthe system variable. (e.g. the heater. Changes what is being measured) 2.Wt

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Negative Feedback

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Aprocess whereby the effect produced by an action serves to diminish orterminate that action. (e.g. when the heater gets to a certain point, it shutsitself off) 0Qv

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Satiety Mechanism

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Abrain mechanism that causes cessation of hunger or thirst, produced by adequateand available supplies of nutrients or water. m

Front 8

How much of the body is water?

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70%

Front 9

Osmolality

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• concentration of sodium in interstitial fluid.Ideal level in 300 mosm. If you go over, it gets flushed out through kidneys. Underit, you will be motivated to consume products high in sodium.

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Isotonic

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theconcentration [ratio of water to solute molecules] is the same inside andoutside the cell. Water goes in and out at the same rate0il

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Hypotonic

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theratio of water molecules is high outside, and very few solute molecules, andvery little water inside. The outside of the cell has fewer solutes outside thecell. The solutes cannot move in and out of the cell, but water can. Throughosmosis, water is driven inside the cell because there are more outside thaninside. The cell will get larger. The cells can rupture and explode..25in;L

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Hypertonic

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• More solutes than water outside the cell. Somany solutes outside, therefore the water is driven outside of the cell.Through diffusion. The cell will get smaller. menr

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Intracellular Dehydration

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Thisis what most people think of when talking about dehydration. Undergoing timesof having very little water. Lack of drinking, eating salty meal. We lose a lotof water through our breath. The fog when fogging a mirror, you can see all thewater you are losing through each breath. If you don’t replenish the water,your water is low in circulation, and easily passes through extracellularenvironment. You now decreased fluids, so water flows out of your cells, theyshrink mP

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Bioassay

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• using a biological function to assess atreatment effect. E.B. Verney used injections of NaCl (increasingconcentrations) and measured urine output. Hypothesized the existence ofosmoreceptors and the existence of anti-diuretic hormone (ADH). The bodysomehow detected the change in solute concentration. They led to the release ofa hormone that was acting at the level of the kidney to change urine output.

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Osmoreceptors

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locatedin the Organum vasculosum of the lamina terminalis (OVLT) and the Subfornicalorgan (SFO) el-tex`

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Alan Epstein

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idea that some cells are neurons. Their osmoreceptors are neurons. As their sizes change their membrane potential changes

Front 17

What leads to the release of vasopressin?

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Osmoreceptoractivation. Released from the Paraventricular Nucleus (PVN) and supraoptic nucleus (SON). Released by the posterior pituitary

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Where is vasopressin released from?

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PAraventricular nucleus (PVN) and supraoptic nucleus (SON)

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Posterior pituitary

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release vaopressin (aka antidieuretic hormone).

it is made up of axons that come from the SON and PVN.

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Hypothalamic preoptic area

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if this area is lesioned, you get decreased drinking in response to stimulus that would normally make you drink

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Extracellular dehydration

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Loseboth water and solutes so there are no change isosmolality. Just less of both of them. Will cells grow or shrink? There willnot be a change in the size of the cells because you are losing both water andsolutes. Your osmoreceptors are not stimulated. They only change therate in firing for the change in the size of the cells. caused by things like hypovolemia(decrease in blood volume) hemorrhage, vomiting, excessive perspiration, bloodloss. YMͧH>(V1Oչˇb566

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How is hypovolemia detected? and by what?

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Detedted by the kidney and arterial baroreceptors. NOT osmoreceptors

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Baroreceptors

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withincirculatory system. Respond to drop in blood volume. Activation ofbaroreceptors with drop of blood volume. Vagus nerve innervates the heart,baroreceptors stimulate part of the vagus nerve.

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Hormonal Signal

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AngiotensinII is a hormone released into the blood at times of hypovolemia. It travels tothe brain stimulates the brain and causes regulatory mechanisms to come intoplay

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Synthesis pathway of Angiotensin II

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Liverreleases protein (antiotensinogen) --> thekidneys release renin (an enzyme) --> enzymes change the structure of the peptide creating angiotensin I --> from the lungs: angiotensin convertingenzyme leads to angiotensin II --> angiotensin II (is amazing btw bc it is biologically active) leads tovasoconstriction [constricts the blood vessels for return to normal rate ofrestriction ] --> leads to the brain --> water and salt intakeC

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Ace inhibitors

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Ace= angiotensin converting enzyme. Blocks ACE.Helps with blood pressure because it blocks the conversion from angiotensin Ito angiotensin II which therefore can do vasoconstriction ^O

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Renin

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hypovolemia stimulates the releaseof renin.

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What does angiotensin do/stimulate?

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Brian: tells the brain to drink, eat salt, etc. Behavior and vasopressin release

Kidney

Adrenal Cortex: synthesis and release of aldosterone

Gut

Vascular smooth muscle

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How does a peptide get access to the brain?

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It cant get across the blood brain barrier. There are certain nuclei in the brain. Circumventricular organs lack a blood brain barrier. There are gaps between the cells that make up the vasculature of the blood brain barrier. Lack a blood brain barrier that angiotensin can stimulate. e.g. SFO, AP, OVLT

Front 30

Which circumventricular organs are important for intercellular dehydration?

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SFO and OVLT

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Area Postrema

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detects toxins in the blood. If there are toxins in the blood, it will stimulate you to vomit.

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Where does angiotensin bind?

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in the SFO

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Aldosterone

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steroid that acts in conjunction with Angiotensin II and stimulates salt intake. Angiotensin and this have a syngergetic effect on salt intake when used together

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Glucoprivation

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low glucose levels

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Lipoprivation

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low levels in fat concentration

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Insulin

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moves glucose from the blood stream into cells. Comverts glucose of glycogen for storage. Reguired for glucose uptake into cells for storage or ATP production (for use). Reduced blood glucose- shunting it out of circulation and into the cells. It is a peptide

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Glucagon

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converts liver glycogen to glucose, inceases blood glucose level

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What 2 hormones are released from the pancreas?

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insulin and glucagon

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Failure of insulin function

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diabetes mellitus. Glucose cannot enter cells, so it builds up in the blood and causes hyperglycemia (high blood sugar). Excessive urination

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what is diabetes mellitus

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failure of insulin function. Glucose cannot enter cells, so it builds up in the blood and causes hyperglycemia (high blood sugar). Excessive urination. Tastes sweet

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Type 1 diabetes

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body cant make insulin

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Type 2 diabetes

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body can make insulin, but isinsensitive to it. The insulin receptor is no longer receptive to the insulin. Can bepartially genetic. Its mostly preventable– through a change in diet andincreased exercise Tµ

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What do you need to make a cell function

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either glucose or fatty acids

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2DG

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mimics glucoprivation. The cell can no longer use glucose. The cell doesnt see the glucose.

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MP (MEthyl palmoxirate)

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the body thinks it has low lipids (lipoprivation)

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When the body experiences glucoprivation

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it stimulates food intake

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When the body experiences lipoprivation

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the body wants to eat

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2DG + MP

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have a synergistic effect for food intake.

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What is the direction of flow for CSF

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rostral (front) to caudal (back)

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If you inject a substance into the 3rd ventricle...

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it will flow throughout the entire brain

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If you inject a substance into the 4th ventricle...

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It will only stimulate the hindbrain. Will not back able to go back up to the forebrain because of the direction of flow

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What part of the brain contains cells that monitor available glucose?

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the hindbrain

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Why doesnt MP have an effect on the brain?

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The brain cells cannot metabolize fatty acids. Brain cells only metabolize glucose.

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Vagus nerve

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integrates signals. Relays info to the brain (the nucleus of the solitary tract) about gastric stretch. A lot of regulation takes place here.

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Cholecystokinin (CCK)

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Hormone released from the cels in the intestine in reponse to nutrients. Receptors are located in the periphery and in the brain.

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Where are CCK receptors located?

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receptors are located in the periphery and the brain

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Dual Center Hypothesis

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1 region of thebrain stimulated hunger and eating and 1 region of the brain stopped hunger andpromoted satiety. These were the 2 critical areas. Wrong forthe most part.

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LAteral hypothalamus

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believed to be the region to stimulate hunger

Part of the dual center hypothesis which is wrong

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Decerebrate rats

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cant regulate long term food intake

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hindbrain is important for

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regulation of food intake

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LH lesioned animals

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destruction of dopamine pathways important for movement. Animals that dont move well dont eat well

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Why is the dual center hypothesis incorrect?

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The VMH isloosely related to food intake. More related to insulin release and glucose. Iyou lesion the VMH, there is a rapid increase in insulin. Takes all of theglucose and moves them into the cells into storage. The animal is then seeing glucoprivation.

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What did the discovery of leptinand the leptin receptor change about the way people thought of the control offood intake?

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-Provided link between fat storesand the control of intake-- Provided a marker in the brainthat could be used for future investigations-- Identified a gene that contributedto some weight issues-- Sparked the “peptide boom”