Choose a hormone ( Antidiuretic hormone \"ADH\"), research its feedback look com

Question

Choose a hormone (Antidiuretic hormone "ADH"), research its feedback look components,

make a 6 slide powerpoint presentation

describing every component of that hormonal feedback loop.

This slide’s each component of the feedback loop with your specific hormone ’s information.

This slide should be your FIRST slide in the presentation.

The rest of the slides should EACH provides more information on EACH provides

more information on each component.

Here is an example of the hormone INSULIN

Receptor: beta cells of Islets of Langerhans (pancreas)Be careful this

is not the receptor for the hormone in the target organ/effector but the receptor

that senses the variable and tells those cells in control center/gland to produce that hormone

Control center: beta cells of Islets of Langerhans (pancreas)

Variable, set point: blood glucose; 70-110, 140 mg/mm3

Effector: cells able to absorb glucose, amino acids from blood, muscle and

Adipose store glycogen and fat; synthesis of glycogen

Outcome: decrease blood glucose; released when blood glucose high

Disease: Diabetes Mellitus

Feedback Loop Components:

1.Variable: Chemical or physical characteristic of the body that varies in the internal

environment. Start with the variable when you do your presentations.

2.Receptor: The Receptor is an anatomical structure that picks up changes in

the variable (stimulus)

3.Afferent pathway: how the message that a change in the variable has occurred

is sent to the control center. In many endocrine feedback loops, the receptor

and control center is the same and therefore the afferent pathway is absent.

4.Control Center: The Control Center is an anatomical structure that establishes the set point (average value for that variable), receives input from the Receptor and decides if action needs to be taken on the changing variable.

5.Efferent pathway: A “message” is then sent from the Control Center by way of

the efferent pathway to the Effector. In endocrine feedback loops, the hormone.

being released into the bloodstream is the efferent pathway.

6.Effector: The Effector is an anatomical structure that changes the value of the

variable (increases or decreases). An Effector produces a response to the

stimulus.

The hormone for this presentation is Antidiuretic hormone.

Explanation / Answer

The hormones of posterior pituitary are oxytocin and vasopressin (anti diuretic hormone, ADH). Both are synthesized in the hypothalamus and released out through the posterior pituitary. Oxytocin increases the uterine contraction and milk ejection. Vasopressin is essential for the maintenance of blood volume and fluid balance.

The ADH (anti-diuretic hormone or vasopressin) increases the water reabsorption from the distal tubule by binding to the vasopressin receptors V1 and V2, which re a type of G-protein coupled receptors. It has no direct effect on sodium reabsorption. Decreased aldosterone secretion causes decreased sodium reabsorption.

Regulation of ADH release:

If the blood pressure falls below the normal levels, a hormone called erythropoietin (EPO) is released from the endocrine cells of the kidney and renin is released from the juxtra glomerular apparatus of the kidney.

The activation of renin-angiotensin system (RAS) causes the secretion of aldosterone and anti-diuretic hormone (ADH), which together causes increased thirst and fluid intake that in turn causes increase in blood volume and pressure. Activation of RAS also causes increased red cell production that contributes for increasing the blood volume. Once the blood pressure is increased (reach normal levels), the ADH secretion is decreased.

Summary of negative feedback regulation of ADH:

Stimulus – Change in blood pressure --> Alter the osmolarity of plasma and interstitial fluid

Receptors – Osmoreceptors in the hypothalamus --> Sends input in the form of nerve impulses to the control center

Control center ---> Hypothalamus and posterior pituitary gland --> Sends output in the form of increased ADH release to the effectors

Effectors --> Principal cells of nephron --> Produce response by becoming more permeable to water, and increasing the water reabsorption

Response --> Restores the normal homeostasis and bring the normal plasma osmolarity --> Supress the stimulus

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