Week 24b: Endocrine System

How is the endocrine system related to the nervous system?

The endocrine system is closely related to the nervous system, but it coordinates maintenance of long-term homeostasis across a range of tissues and organs, whereas the nervous system responds to short-term stimuli at specific receptors that induce responses at specific effectors.

How do endocrine tissues secrete hormones?

Endocrine tissues secrete hormones directly into the bloodstream, and cells with complementary receptors respond to these hormones.

What is this and can you describe it?

What is a similarity between the endocrine and nervous systems in terms of chemical messengers?

Both the endocrine and nervous systems use chemical messengers.

Are there any chemical messengers that are used by both the endocrine and nervous systems?

Yes, some chemical messengers such as adrenaline are used by both the endocrine and nervous systems, acting as both hormones and neurotransmitters.

Do the endocrine and nervous systems use negative feedback?

Yes, both the endocrine and nervous systems use negative feedback.

What is the common aim of the endocrine and nervous systems?

The common aim of both the endocrine and nervous systems is to maintain homeostasis in the body.

What is this and can you describe it?

Which cells and tissues of the body produce hormones?

Hormones are produced by all the endocrine cells and tissues of the body.

What is the difference between endocrine and exocrine?

The endocrine system secretes hormones directly into the bloodstream to travel to distant target tissues, whereas the exocrine system secretes substances into ducts that lead to the outside of the body or into body cavities.

Are all hormones distributed throughout the body?

No, some hormones are "local" and only affect cells close to the site of secretion, such as prostaglandins.

What are the primary endocrine tissues?

The primary endocrine tissues include the pituitary and pineal glands.

What are the secondary endocrine tissues?

The secondary endocrine tissues include the liver and kidneys.

Can you describe what this is?

Can you describe what this is?

Are all tissues exposed to hormones in the bloodstream?

Yes, all tissues are exposed to hormones in the bloodstream.

Do all tissues respond to hormones in the bloodstream?

No, only those tissues that have complementary receptors for specific hormones will respond to them.

How do hormones affect the tissues in the body?

Hormones affect the tissues in the body by binding to specific receptors on the surface of or within target cells that have complementary receptors for specific hormones.

What is this and can you describe it?

Endocrine system: secondary messaging

1\. Peptide hormones (first messengers) cannot pass the PLB so they bind to receptors in the membrane

2\. G-proteins are bound to receptors on the cytosolic side of the cell and binding activates them

3\. Activated G-proteins convert ATP to cyclic AMP (cAMP) which activates protein kinases; cAMP is the secondary messenger

4\. Kinases phosphorylate transcription factors which change the identity and proportion of gene products

What is this can you describe it?

Endocrine system: intracellular receptors

1\. Fatty-acid and cholesterol derived hormones can pass freely through the PLB

2\. They bind directly to receptors in the cytoplasm to form hormone-receptor complexes

3\. Thyroid hormones bind to mitochondria and alter ATP production

4\. Steroid hormones bind to transcription factors which alter the production of gene products

What is this and can you describe it?

How is endocrine activity regulated?

Endocrine activity is regulated by negative feedback loops.

Endocrine system: negative feedback

1. A stimulus causes an increase in the production of a hormone
2. Hormones bind to receptors in target cells which causes a response
3. The response causes a chemical change near the endocrine organ
4. This change acts as a second stimulus and stops hormone production

What is this and can you describe it?

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What is this and can you describe it?

How are calcium levels regulated in the body?

Calcium levels in the body are regulated humorally by parathyroid hormone (PTH) and calcitonin released by the thyroid.

What is this and can you describe it?

What is the role of the hypothalamus in the endocrine system?

The hypothalamus provides the link between the nervous and endocrine systems

Neurones in the hypothalamus produce antidiuretic hormone (ADH) and oxytocin which directly enter the bloodstream

The hypothalamus also regulates activity of the pituitary gland by secreting releasing (RH) and inhibitory hormones (IH)

What is the pituitary gland?

The pituitary gland is one of the most important endocrine organs it secretes nine different hormones.

What is this and can you describe it?

What is this and can you describe it?

What are the five classes of hormones and how can they be broadly separated?

The five classes of hormones are amino acid derivatives, peptide hormones (including glycoproteins), steroids, eicosanoids, and lipid-insoluble hormones. They can be broadly separated into two groups based on their mode of action. Lipid-insoluble hormones rely on secondary messaging while lipid-soluble hormones bind directly with intracellular receptors.

Can you give an example of a hormone from each of the five classes?

Amino acid derivative - Melatonin,

Peptide hormone - Oxytocin

Glycoprotein hormone - Follicle-stimulating hormone (FSH)

Steroid hormone - Cortisol

Eicosanoid hormone - Prostaglandins.

What is the function of eicosanoids and how can they be classified based on their mode of action?

Eicosanoids almost always act on the cells that produce them or on neighboring cells, that is, over short distances and time periods, and, therefore, can be classified as autocrine/paracrine hormones.

What is this and can you label it?

What are amino acid derived hormones and what are they manufactured from?

Amino acid derived hormones are a class of hormones that are manufactured from tyrosine and/or tryptophan.

How can you identify amino acid derived hormones?

Amino acid derived hormones are identifiable by the fact they end with the suffix ‘-ine’. They are also the smallest class of hormones.

What are some examples of amino acid derived hormones and where are they synthesized?

Some examples of amino acid derived hormones include epinephrine and norepinephrine, which are synthesized in the adrenal glands, thyroxine which is synthesized in thyroid glands, and melatonin (tryptophan-derived) which is synthesized in the pineal gland.

What is this?

What is this?

What is this?

What type of hormones are peptide hormones and how do they exert their effects on target cells?

Peptide hormones are lipid-insoluble and rely on secondary messaging to exert their effects on target cells. Examples of peptide hormones include oxytocin, ADH, and glycoproteins like FSH and LH.

What is this?

What is this?

What are glycoprotein hormones?

Glycoprotein hormones are a subclass of peptide hormones that include the gonadotropins such as follicle stimulating hormone (FSH).

What is this?

What is this?

What is this?

What are steroid hormones synthesized from?

Steroid hormones are synthesized from cholesterol in the gonads and adrenal glands.

Where do corticosteroids and sex steroids form?

Corticosteroids form in the adrenal glands, while sex steroids form in the gonads.

What type of hormones are steroid hormones and how do they bind?

Steroid hormones are lipid-soluble and bind with intracellular receptors to form hormone-receptor complexes. Often, these are transcription factors. If they bind to membrane receptors, they will alter ionic permeability.

What is this?

What is this?

What are the diverse functions of steroid hormones?

1. Control of metabolism
2. Control of inflammatory response
3. Regulation of immunity
4. Osmoregulation
5. Development of sex characteristics
6. Resistance to illness and injury
7. Control of ‘flight or fright’ response

What are Eicosanoids?

Eicosanoids are a class of lipid hormones made from polyunsaturated fatty acids with 20 carbon backbones. Unlike ‘true’ hormones, they are not secreted by specialised glands, and are secreted by all tissues. Eicosanoids have short half-lives which means they operate locally (autocrine/paracrine) and their biological activity is mediated by G protein-coupled receptors (GPCRs).

What is this?

Label this:

How many primary endocrine organs are there?

7

How many organs are there with secondary endocrine functions?

6

What are primary and secondary endocrine organs?

Primary endocrine organs solely secrete hormones, while secondary endocrine organs secrete hormones as well as perform additional biological functions to support their primary functions.

What is the most active form of vitamin D?

Calcitriol is the most active form of vitamin D.

Which cells in females and males secrete inhibins, and what is their function?

Inhibins are protein hormones secreted by granulosa cells in females and Sertoli cells in males. They selectively suppress the secretion of pituitary follicle-stimulating hormone (FSH).

Can you describe this and label this

What hormones are secreted by the hypothalamus and what are their functions?

The hypothalamus secretes antidiuretic hormone (ADH) and oxytocin.

What is the role of antidiuretic hormone (ADH) and oxytocin in the body?

ADH is involved in osmoregulation, helping the body retain water and maintain proper fluid balance. Oxytocin regulates social bonding, including maternal behavior and romantic attachment.

How many hormones are secreted by the pituitary gland, and what are their functions?

The pituitary gland secretes nine hormones with a variety of functions. These include 7 secreted by the anterior lobe which are peptide hormones. The first 4 regulate hormone production of other endocrine tissues - adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH) and these three which have direct impacts on physiology and metabolism - growth hormone (GH), prolactin (PRL), melanocyte-stimulating hormone (MSH) and two secreted by the posterior lobe antidiuretic hormone (ADH) and oxytocin.

What are the hormones and their functions that are produced by the anterior lobe of the pituitary gland?

What are the hormones and their functions that are produced by the posterior lobe of the pituitary gland?

What hormone does the pineal gland secrete, and what stimulates its production?

The pineal gland secretes melatonin, and its production is stimulated by darkness.

What is the role of melatonin in the body?

Melatonin applies sleep pressure and helps regulate the sleep-wake cycle.

Where are the parathyroid glands located and what hormone do they produce?

The parathyroid glands are located behind the thyroid gland. They produce parathyroid hormone (PTH), which regulates calcium levels in the body by increasing the release of calcium from bones and the reabsorption of calcium in the kidneys.

What is this and can you label it?

What is this

What hormones are secreted by the thyroid gland, and what are their functions?

The thyroid gland secretes thyroxine, triiodothyronine, and calcitonin. Thyroxine and triiodothyronine regulate metabolism, while calcitonin regulates calcium levels in the blood by decreasing the release of calcium from bones and increasing calcium excretion by the kidneys.

What is the role of calcitonin in the body?

Calcitonin helps regulate calcium levels in the body by decreasing the release of calcium from bones and increasing calcium excretion by the kidneys.

What hormones are produced by the adrenal glands, and what is their role?

The adrenal glands produce epinephrine (adrenaline), norepinephrine (noradrenaline), and cortisol. These hormones help regulate the body's response to stress, including the "fight or flight" response, blood pressure, and blood sugar levels.

What is this and can you label it?

What is this and can you label it?

What are the dual functions of the pancreas?

The pancreas is both an endocrine and an exocrine organ. As an endocrine organ, it secretes insulin and glucagon which regulate glucose levels in the blood. As an exocrine organ, it secretes digestive enzymes into the lumen of the small intestine.

What is this can you label it?

What hormone does the heart secrete, and what stimulates its release? What is its association with high blood pressure?

The heart secretes atrial natriuretic peptide (ANP). ANP is released in response to atrial distension. It is common in people with high blood pressure.

What is the function of the thymus, and what hormone does it secrete in response to pathogens?

The thymus is only active until puberty. It secretes thymosins in response to pathogens. Thymosins stimulate T-cell production.

Can you label this?

Can you label this?

What hormone is secreted by adipose tissues, and what are its functions?

Adipose tissues secrete leptin. Leptin controls the hunger response and effects fat storage.

What hormones are secreted by the digestive tract, and what are their functions?

The digestive tract secretes many hormones with a range of functions, such as Gastrin, secretin, and cholecystokinin (CCK). These hormones play a role in glucose metabolism and appetite.

Can you label this?

What hormone is secreted by the kidneys, and what is its function?

The kidneys secrete erythropoietin (EPO) when RBC levels are low. EPO stimulates the production of RBCs in the bone marrow.

What are the gonads responsible for, and what hormones do they produce?

The gonads are involved in the production of steroid sex hormones. Testes produce androgens, while ovaries produce oestrogens and progesterone.

Can you label this?

What is the pituitary gland?

A small oval gland that sits in the sella turcica of the sphenoid bone (at the skull base). It is also called the hypophysis cerebri.

What are related structures of the pituitary gland called?

Hypophyseal.

What structure attaches the pituitary gland to the hypothalamus?

The infundibulum.

How many lobes does the pituitary gland have?

Two.

What hormones does the anterior lobe of the pituitary gland secrete?

Seven hormones.

What hormones does the posterior lobe of the pituitary gland secrete?

Two hormones.

What is the chemical nature of the hormones secreted by the pituitary gland?

Peptides.

What is the secondary messaging system used by pituitary hormones?

cAMP.