Endo I

Question 1

Hormones are secreted into the blood by a(n) […]

Answer 1

endocrine gland

Question 2

What is neuroendocrine signalling?

Answer 2

It is when nerve cells are sources of hormones, such as dopamine (which is also a neurotransmitter).

Question 3

What is the difference between paracrine and autocrine signalling?

Answer 3

Paracrine signalling is local and involves a cell secreting a signalling substance that travels to the target cell.

Autocrine signalling is one cell talking to itself. It releases a hormone and also expresses the receptor for that hormone on its surface.

Question 4

What are the 6 steps of communication by hormones (or neurohormones)

Answer 4

1. Synthesis by endocrine cells or neurons for neurohormones
2. Release of the hormone by endocrine cells
3. Transport of hormone or neurohormone via blood stream
4. Detection of the hormone or neurohormone by target cells
5. Change in cellular metabolism triggered by the hormone-receptor interactions
6. Removal of the hormone, which often terminates the cellular response

Question 5

Where is the Hypothalamic-Hypophyseal Portal System?

Answer 5

It goes from the hypothalamus to the adenohypophysis (anterior pituitary).

Question 6

Explain how hypothalamic-pituitary signaling works.

Answer 6

It occurs via the hypothalamic-hypophyseal portal system. The hypothalamus releases neurohormones via the blood vessels of the pituitary stalk. These either activate (releasing factors) or inhibit (inhibiting factors) the activity of one of the six types of hormone-producing cells in the anterior pituitary.

Question 7

What are the classes of hormones based on structure?

Answer 7

Peptides and proteins:
1. Glycoproteins
2. Polypeptides

Other:
3. Steroids
4. Amines
+ ionic calcium

Question 8

What is the difference between peptides and proteins and other classes of hormones (not based on the structure itself)?

Answer 8

Peptides and proteins are directly encoded by a gene, whereas the others don’t have genes encoding for them directly. There are instead genes encoding for enzymes that produce them.

Question 9

Upon synthesis, protein hormones begin as a […]

Answer 9

preprohormone

Question 10

Describe the process of synthesis of protein hormones up until release.

Answer 10

The protein is first synthesized in the ribosome in the form of a preprohormone. The rough endoplasmic reticulum then converts the preprohormone into a prohormone. The golgi apparatus then packages the prohormone into secretory vesicles. It is stored in the vesicles until it is time for its release.

Question 11

What type of hormone is cortisal?

Answer 11

Steroid

Question 12

What type of hormone is aldosterone?

Answer 12

Steroid

Question 13

What type of hormone is testosterone?

Answer 13

Steroid

Question 14

What type of hormone is estradiol?

Answer 14

Steroid

Question 15

How does the structure of estradiol differ from testosterone, cortisol, and aldosterone?

Answer 15

It has an aromatic ring, which none of the others have. It also lacks the methyl group that testosterone has.

Question 16

What are the two types of thyroid hormones? Describe how their structures differ.

Answer 16

T4 and T3. T4 has 4 iodines in its structure, while T3 has 3.

Question 17

What is reverse T3? Describe its structure and what it is.

Answer 17

Reverse T3 resembles thyroid hormones but is not one. It has 3 iodines like T3, but has 2 and 1 on opposite rings to T3.

Question 18

What is the lock and key mechanism?

Answer 18

It is the idea that receptors and their corresponding hormones must have complementary shapes to allow for binding.

Question 19

Name the 4 major properties of hormone receptors. Explain them

Answer 19

1. Specificity: recognition of a single hormone or hormone family
2. Saturability: finite number of receptors
3. Affinity: binding hormone at its physiological concentration
4. Measureable biological effect: there is a biological response due to interaction of hormone with its receptor

Question 20

What are the two ways in which receptors can be regulated?

Answer 20

They can be either upregulated or downregulated by:
- Increasing/decreasing their activity in response to a hormone
- Increase/decreasing their synthesis

Question 21

What are the 3 mechanisms by which a hormone can exert effects on target cells?

Answer 21

1. Direct effects on function at the cell membrane
2. Intracellular effects mediated by the second messenger systems
3. Intracellular effects mediated by genomic or nuclear action

Question 22

Explain how a hormone can exert effects on target cells via direct effects on function at the cell membrane.

Answer 22

There is a direct interaction between the receptor and its target.

Question 23

Explain how a hormone can exert effects on target cells via intracellular effects mediated by second messenger systems.

Answer 23

The hormone is going to exert effects not only on the membrane itself, but within the cell, potentially changing transcription and translation of genes. For this to happen, there has to be second messengers, which transmit the signal to various places within the cell.

Question 24

Explain how a hormone can exert effects on target cells via intracellular effects mediated by genomic or nuclear action. What type of hormones typically do this?

Answer 24

Hormones enter the cell and bind to receptors that are in the cytoplasm or are already in the nucleus. Once in, they alter protein synthesis and lead to an altered functional response.

This is typically done by steroids because they can penetrate the membrane.

Question 25

The production of cyclic AMP is an example of what type of hormone signaling?

Answer 25

Signaling via intracellular second messenger