- Explain the role of negative feedback in visceral reflexes - Describe the gene

Question

- Explain the role of negative feedback in visceral reflexes

- Describe the general characteristics of a hormone

- Contrast the characteristics of water vs. lipid soluble hormones

- Explain the anatomical and physiological relationships between the hypothalamus and

pituitary gland

- Describe how hypersecretion of parathyroid hormone can affect its target organs and overall

body function

- Create the endocrine pathway that leads to the release of thyroid hormone and

glucocorticoids

- Describe how dysfunction in the endocrine glands in the glucocorticoid pathway can affect

normal body function and how the source of dysfunction can be detected

- Identify which hormones are involved and how they influence blood glucose regulation

Explanation / Answer

1. Explain the role of negative feedback in visceral reflexes

ANS: Visceral reflexes are the reflexes that occur in the soft tissue organ of the body, such as reproductive and digestive system. Examples like dilation of pupils, defecating, and vomiting.Reflexes controlled by autonomic neurons

Example of a homeostatic negative feedback loop

Baroreflex:
1) high BP detected by arterial stretch receptors
2) afferent neuron carries signal to CNS
3) efferent signals travel to the heart
4) heart slows reducing BP

SYMPATHETIC division is the fight or flight response. Prepares the body for activity, increases heart rate, BP, airflow, blood glucose and reduces blood flow to the skin/digestive tract.
PARASYMPATHETIC division is the "resting and digesting" response. Reduces energy expenditure and has a calming effect. Aids in digestion and waste elimination.

2. Describe the general characteristics of a hormone

ANS: All hormones share three charactensbcs Hormones have defferent levels of stability, or the time they are usable. The chemcal make up of the hormone is the largest determining factor on how long it is stable. Some hormones lare only a couple of minutes, while others last over an hour. Degradation occurs because of other chemicals in the bloodstream that it may react with.

second characterstic of hormones is that they communicate. If a hormone cannot communicate and set off events than it is useless. For the required events to occur, a hormone must be able to interact with as target, usually by binding. This causes the target to act. This act can be growth caused by the pituitary gland or cause a fetus to grow sex organs.

A third characteristic of hormones is their distribution They must be able to get to their target tissue, even it is far away. Water soluble hormones tend to be very small, meaning even a little change makes them inert. This is trouble because the blood A full of enzymes that can cause reactions that will change the hormone's chemical structure. Particularly reactive hormones sometimes have proteins that cany them, or chaperone, to their target. The protein keeps them from being rendered inet. Lipid soluble hormones can travel further safer because they are harder to react with due to their lack of solubilky and just general lack of reactivity.

3. Contrast the characteristics of water vs. lipid soluble hormones

ANS: Water soluble hormones as do not pass through the plasma membrane, because the plasma membrane is rich in lipids and cholesterols. It binds to a specific receptor on the plasmamembrane and activates it. Once the receptor is activated it generates second messangers which activates the proteins of different metabolic pathways. These water soluble hormones, activates proteins rather than gene expression. Since they activate or inhibit specific proteins in the pathway, the effect is usually immidiate.

Example: Adrenalin binds and activates adrenergic receptors which activates adenyl cyclase ezyme. Adenyl cyclase generates cyclic AMP (cAMP) a second messengers which activates enzymes of glycogen breatkdown and inhibits enzymes of glycogen synthesis.

Lipid soluble hormones on the other hand easly cross the plasma membrane. Once inside the cytoplasm they bind to receptors in cytoplasm to form hormone-receptor complex which is then trnaslocated inside nucleus. Once inside nucleus it binds to transcriptional factors either to activate or inhibit the gene expression. They can activate or inhibit multiple genes. The effect of Lipid soluble is usually a slow response (But not hormones show slow responce).

Example: androgens produces by males stimulate the production of sperms, development of male sexual charecters, inhibit the production of estrogen. Androgen enters through the plasmamembrane and binds to androgen recetor in the cytosol. This hormone-receptor complex is translocated to nucleus where it activates multiple genes respnsible for anotomical, physiological or behavioral changes.

4. Explain the anatomical and physiological relationships between the hypothalamus and

pituitary gland

ANS: Hypothalamus secretes stimulating and inhibiting hormones that stimulate or inhibit hormone production by anterior pituitary

Anatomically posterior pituitary lobe develops as an extension of hypothalamus.i t is connected to hypothalamus by median eminence via a small tube called pituitary stalk

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