Section 1

Question 1

What are the 6 main functions of the endocrine system as a whole?

Answer 1

1. Maintain constant internal environment via regulation of metabolism and H2O/electrolyte balance
2. Adaptive stress (physical, chemical, physiological, infectious, or emotional) response
3. Growth and development
4. Reproduction
5. Red blood cell production
6. Integrating with the autonomic nervous system in regulating both the circulation and digestive functions

Question 2

What is the adaptive stress response, and how does the endocrine system play a role in this function?

Answer 2

The adaptive stress response is the body’s reaction to conditions that overwhelm its ability to maintain homeostasis. These stress conditions can be physical (trauma, intense heat or cold), chemical (reduced oxygen supply), physiological (exercise, pain), infectious (bacterial invasion), or emotional (anxiety, fear). The endocrine system contributes to the adaptive stress response by releasing hormones that help the body cope with and adapt to these stressors, thereby assisting in maintaining overall physiological balance.

Question 3

What are hormones, and how are they typically released into the bloodstream?

Answer 3

Hormones are chemical substances secreted by endocrine tissues. They are released directly into the blood at low quantities and exert physiological effects at distant target tissues.

Question 4

What are hydrophilic hormones, and how are they characterized in terms of solubility?

Answer 4

Hydrophilic hormones are highly water-soluble with low lipid solubility.

Question 5

What are the two major groups of hydrophilic hormones, and what are they primarily composed of?

Answer 5

The two major groups are peptides (short amino acid chains) or proteins (longer amino acid chains), collectively known as peptide hormones.

Question 6

Besides peptides and proteins, what is the other group within hydrophilic hormones, and what are examples of hormones in this group?

Answer 6

The other group is amines, which includes catecholamines (norepinephrine, epinephrine) and thyroid hormones.

Question 7

What makes catecholamines unique among hydrophilic hormones?

Answer 7

Catecholamines are unique because they can be found both free and bound to carrier molecules.

Question 8

What characterizes lipophilic hormones, and what are the two main types within this category?

Answer 8

Lipophilic hormones are highly soluble in lipids and poorly soluble in water. The two main types are amine thyroid hormones and steroid hormones.

Question 9

Explain the solubility characteristics of lipophilic hormones and mention the two subtypes within this category.

Answer 9

Lipophilic hormones are highly soluble in lipids and poorly soluble in water. This category includes amine thyroid hormones and steroid hormones. These hormones generally require carrier molecules for effective transport throughout the body.

Question 10

True or false: Lipophilic hormones generally require carrier molecules for effective transport throughout the body.

Answer 10

True

Question 11

True or false: Hydrophilic hormones generally require carrier molecules for effective transport throughout the body.

Answer 11

False

Question 12

How are peptide hormones synthesized and released into the bloodstream?

Answer 12

Peptide hormones are synthesized from large precursor proteins called preprohormones. These preprohormones are processed and packaged into secretory vesicles in the endoplasmic reticulum and Golgi complex. Upon receiving the appropriate signal, the vesicles undergo exocytosis, releasing hormones into the bloodstream.

Question 13

Outline the steps involved in the synthesis of peptide hormones, including the initial synthesis, processing, packaging, storage, and the final release into the bloodstream.

Answer 13

Peptide hormones undergo a multi-step synthesis process. Large precursor proteins, known as preprohormones, are synthesized by ribosomes in the endoplasmic reticulum.

During their transit through the endoplasmic reticulum and Golgi complex, these preprohormones are processed into active hormones and packaged into secretory vesicles. These vesicles, containing the active hormones, can be stored until the cell receives the appropriate signal.

Upon receiving the signal, exocytosis is initiated, leading to the release of hormones into the bloodstream.

Question 14

Which of the following is/are able to freely dissolve in plasma:

a) steroid hormones
b) catecholamines
c) thyroid hormones
d) peptide hormones

Answer 14

d) peptide hormones

Question 15

Which of the following is/are not able to freely dissolve in plasma, and thus must bind to specific carrier molecules, or to plasma proteins such as albumin:

a) steroid hormones
b) catecholamines
c) thyroid hormones
d) peptide hormones

Answer 15

a) steroid hormones
AND
c) thyroid hormones

Question 16

Which of the following is/are unique as 50% are found free in the plasma, and 50% bind to albumin:

a) steroid hormones
b) catecholamines
c) thyroid hormones
d) peptide hormones

Answer 16

b) catecholamines

Question 17

What is the common precursor molecule for all steroid hormones, and how is the synthesis of a specific steroid hormone determined?

Answer 17

Cholesterol serves as the precursor for all steroid hormones. The synthesis of a particular steroid hormone is determined by the specific enzymes present in the cells of the tissue producing that hormone.

Question 18

Explain the synthesis process of steroid hormones, emphasizing the role of cholesterol as the precursor. How is the production of a specific steroid hormone regulated within a tissue?

Answer 18

Steroid hormones are synthesized from the single molecule cholesterol. The tissue-specific synthesis of a steroid hormone depends on the enzymes present in the cells of that tissue.

For instance, cortisol synthesis is initiated by a key enzyme found exclusively in the adrenal cortex. Unlike some other hormones, steroid hormones, being lipophilic, are not stored but released immediately upon synthesis. Consequently, the regulation of steroid hormone release involves controlling the synthesis process itself.

Question 19

When is it important for hormones to be in their unbound state?

Answer 19

For hormones to achieve their desired effect, they must be in their unbound state to interact with receptors on target cells.

Question 20

Which type of hormones does the requirement for being in an unbound state primarily apply to?

Answer 20

This primarily applies to lipophilic hormones, such as steroid hormones.

Question 21

What is the dynamic equilibrium related to lipophilic hormones and their carrier molecules?

Answer 21

Lipophilic hormones, like steroid hormones, are in a dynamic equilibrium of binding and unbinding with their carrier molecules in the blood.

Question 22

Why is a small fraction of lipophilic hormones unbound at any given time, and why is this fraction crucial?

Answer 22

The dynamic equilibrium results in a small fraction of lipophilic hormones being unbound, and it is this unbound fraction that is active and able to act on target cells.

Question 23

What is the role of carrier molecules in the interaction of lipophilic hormones with target cells?

Answer 23

Carrier molecules transport lipophilic hormones in the blood, and these hormones must be unbound from their carrier protein to enter target cells and interact with receptors.

Question 24

Why is it crucial for hormones to be in their unbound state to interact with receptors at target cells, and how does this requirement differ between hydrophilic hormones/catecholamines and lipophilic hormones?

Answer 24

For hormones to achieve their desired effect, they must be in their free, unbound state to interact with receptors on target cells.

This is NOT an issue for hydrophilic hormones and catecholamines, which are mainly found in their unbound state. However, for LIPOPHILIC hormones that require carrier molecules, the dynamic equilibrium of hormone binding to its carrier becomes significant.

Question 25

_______ hormones, such as ________ hormones, must be unbound from their carrier protein in order to enter their target cell and interact with their receptor.

Answer 25

LIPOPHILIC hormones, such as STEROID hormones, must be unbound from their carrier protein in order to enter their target cell and interact with their receptor.

Question 26

Predict where the receptors of peptide hormones, steroid hormones, catecholamines, and thyroid hormones are located in the cell.

Answer 26

Peptide hormones and catecholamines bind to specific receptors on the outer surface of the plasma membrane of their target cells and they are hydrophilic, and thus unable to freely cross the lipid bilayer of the plasma membrane.

On the other hand, steroid hormones and thyroid hormones are lipophilic and can easily slip through the plasma membrane and bind to specific receptors inside their target cells.

Question 27

What is the specificity of hormone action determined by?

Answer 27

The specificity of hormone action is determined by the presence of receptors on target cells.

Question 28

How do peptide hormones & catecholamines exert their effects on their target cell in comparison to steroid & thyroid hormones?

Answer 28

Peptide hormones and catecholamines:

Binding of these hormones to their surface receptors produces effects within cells by activating second messenger systems. These pathways are able to amplify the initial signal, as low concentrations of hormones trigger pronounced cellular responses

Steroid and thyroid hormones:

These hormones are able to pass through both the plasma membrane and the nuclear membranes of the cell. Binding of these hormones to their receptors inside target cells produces effects by regulating gene transcription and protein synthesis.

Question 29

What are the two major second messenger systems for peptide hormones and catecholamines?

Answer 29

Cyclic AMP (cAMP)
and
Calcium (Ca2+)

Question 30

Options: adenylyl cyclase, cAMP, G protein, Messenger, phosphorylate, target proteins

First, an extracellular ___________ binds to a receptor, activating a ___________ which shuttles to and activates several ___________ molecules. Next, these activated proteins convert many molecules of ATP to ___________ , which then activate protein kinase A. The activated protein kinase A enzymes then ___________ , and activate ___________, which can then bring about the desired result.

Answer 30

First, an extracellular messenger binds to a receptor, activating a G protein which shuttles to and activates several adenylyl cyclase molecules.

Next, these activated proteins convert many molecules of ATP to cAMP, which then activate protein kinase A.

The activated protein kinase A enzymes then phosphorylate, and activate target proteins, which can then bring about the desired result

Question 31

Options: Ca2+, G protein, PIP2, phospholipase C, protein kinase, target proteins

First, an extracellular messenger binds to a receptor, activating a ___________, which shuttles to activate several ___________ enzymes.

These proteins convert ____________ to IP3 and DAG. IP3 mobilizes
intracellular ___________, which activates calmodulin. The Ca2+-calmodulin complexes then activate Ca2+-calmodulin-dependent _________ (CaM kinase), which phosphorylate and activate ___________, bringing about the desired response

Answer 31

First, an extracellular messenger binds to a receptor, activating a G protein, which shuttles to activate
several phospholipase C enzymes.

These proteins convert PIP2 to IP3 and DAG. IP3 mobilizes intracellular Ca2+, which activates calmodulin. The Ca2+-calmodulin complexes then activate Ca2+-calmodulin-dependent protein kinase (CaM kinase), which phosphorylate and activate target protein, bringing about the desired response

Question 32

How do lipophilic hormones regulate protein synthesis in cells, and what are the six steps involved in this process?

Answer 32

Lipophilic hormones regulate protein synthesis by interacting with intracellular receptors. The six steps involved are:

1. Free lipophilic hormone diffusion across plasma and nuclear membranes.
2. Binding of hormone-receptor complex (H-R) to the hormone response element (HRE) within DNA.
3. Activation of specific genes, leading to mRNA production.
4. Exit of mRNA from the nucleus.
5. Binding of mRNA to a ribosome and synthesis of proteins.
6. Newly synthesized proteins inducing the cellular response of the hormone.

Note: Lipophilic hormone receptors can be found within the cytoplasm or the nucleus.

Question 33

List the key differences between hormones and neurotransmitters

Answer 33

• Neurotransmitters belong to the nervous system, and hormones are a central component of the endocrine system.
• Neurotransmitters are transmitted across a synaptic cleft. Hormones are transported by the blood.
• Hormones are produced by endocrine glands, while neurotransmitters are produced by
  neurons.
• Neurotransmitters must travel a short distance to their target, while hormones may travel a great distance.