Hormones (Endocrine system), Pituitary gland and Pituitary disorders

What does the endocrine system consist of?

Collection of all glands of the body and hormones they produce

What is another name for the endocrine system?

Hormone system

How do glands and hormones work together in the endocrine system?

They work together to sustain life

What is a hormone?

A substance normally produced by specialized cells in some part of the body, carried by the bloodstream to another part, and affects the body as a whole.

How do endocrine secretions differ from exocrine secretions?

Endocrine secretions go into the blood, while exocrine secretions go to ducts or surfaces.

What are examples of exocrine glands

1. Bile ducts

2. Sweat glands

3. Salivary glands

What is endocrinology?

The study of ductless glands and the action of their secretions

How do ductless glands work?

The release their hormones directly into the bloodstream

Where are hormones produced?

The endocrine glands

What is the main function of hormones?

They provide regulatory effects

What hormone regulates glucose uptake for storage as fat?

Insulin

Which hormone regulates metabolism?

Thyroxine

What hormone is known as the stress hormone and is involved in the fight and flight response?

Cortisol

What type of regulatory effects do hormones have?

Autocrine and Paracrine

What is an autocrine effect?

It occurs within a given endocrine gland or tissue affecting the same cell that produces the hormone

What is an example of an autocrine effect?

Growth Factors

What is a paracrine effect?

It occurs when a hormone affects nearby or neighboring cells from the site of production

What are examples of paracrine effects?

Neurotransmitters and neurohormones

What is one main function of hormones in the body?

Homeostasis

How do hormones help during stressful or emergency situations?

They adapt to meet increased demands

What can manifest during extreme fight-or-flight situations due to hormonal action?

Superhuman abilities

How does epinephrine act during an acute stress response related to glucose?

It acts acutely on insulin to make glucose available

What hormone action is involved in restoring blood volume during dehydration, starvation, or hemorrhage?

Hypovolemia

How do hormones respond to temperature extremes like hypothermia or hyperthermia?

Epinephrine, norepinephrine, thyroid hormone, and cortisol increase the metabolic rate by stimulating fat breakdown to generate or dissipate heat.

Which hormones increase metabolic rate to manage temperature extremes?

1. Epinephrine

2. Norepinephrine

3. Thyroid hormone

4. Cortisol

What is the role of hormones in growth and development?

They regulate it

How do hormones affect sexual maturation?

They promote it

How do hormones regulate energy production?

Insulin acts as a anabolic hormone, while epinephrine and cortisol are catabolic, making glucose available

How do hormones influence the production or release of other hormones?

Through positive feedback mechanisms

How do hormones inhibit the production or release of other hormones?

Through negative feedback mechanisms

What is the role of hormones in the immune system?

They regulate the immune system, including T cell proliferation, maturation, and function.

How do glucocorticoids and sex hormones affect immune cells?

Glucocorticoids suppress immune cell activity, while sex hormones enhance it.

Why can hormones regulate immune cells?

Because immune cells have receptors for these hormones

What are the three types of hormones based on chemical structure?

1. Polypeptides

2. Amines or amino acids

3. Steroids

Give an example of a polypeptide hormone.

Parathyroid hormone

What is an example of an amine or amino acid hormone?

3,5,3',5'-tetraiodothyronine (T4).

Provide an example of a steroid hormone.

Cortisol.

How are peptide hormones characterized in terms of solubility?

They are highly water soluble and have little lipid solubility

Why can't peptide hormones penetrate lipid membranes?

Because they are not lipid soluble

How do peptide hormones interact with cells if they can't penetrate the membrane?

They bind to surface receptors

What system is activated by peptide hormones after binding to a surface receptor?

A second messenger system

What signaling protein do peptide hormones use to initiate their action?

G-protein

What enzyme does the G-protein activate in the peptide hormone mechanism?

Adenylate cyclase

What is the function of adenylate cyclase?

It catalyzes the conversion of ATP to cyclic-AMP

What acts as the second messenger in the peptide hormone mechanism?

Cyclic-AMP

What is the role of the first messenger in the peptide hormone mechanism?

The hormone itself is the first messenger, initiating the process.

What is the function of epinephrine in the body?

It increases glucose availability and energy

What is the solubility characteristic of steroid hormones?

They have high lipid solubility and low water solubility

Why do steroid hormones require transport proteins in the bloodstream?

Because they are not water soluble and the bloodstream is hydrophilic due to plasma

What is an example of a transport protein for steroid hormones?

Sex hormone-binding globulin (SHBG).

How do steroid hormones travel from the organ of synthesis to their target site?

They are carried through the bloodstream by transport proteins

How do steroid hormones enter their target cells?

Through diffusion

What do steroid hormones bind to once inside the target cell?

They bind to intracellular receptor molecules

What happens when steroid hormones bind to their intracellular receptors?

They produce a conformational change in the receptor structure

Where are intracellular receptors for steroid hormones located?

In the cytoplasm and nuclear fractions of cells

What is the final action of steroid hormones at the cellular level?

They induce gene expression

What type of binding protein is albumin?

A high capacity binding protein

What type of binding protein is globulin?

A high specificity binding protein

What is another name for the pituitary gland?

The hypophysis or the master gland

Where is the pituitary gland located?

At the base of the skull in the sella turcica

What is the size and weight of the pituitary gland?

It is about the size of a pea and weighs 500 mg

How is the pituitary gland attached to the hypothalamus?

Via the infundibulum

What are the three lobes of the pituitary gland?

1. Adenohypophysis (anterior lobe)

2. Neurohypophysis (posterior lobe)

3. Intermediate lobe

What is the adenohypophysis?

It is the anterior lobe, the glandular portion of the pituitary that contains cells

How is the adenohypophysis controlled?

It is controlled by releasing hormones (RH) and inhibitory hormones (IH) from the hypothalamus

What is the neurohypophysis?

It is the posterior lobe of the pituitary, containing axons or secretory cells from the hypothalamus and has no hormone producing cells

What hormones are stored in the neurohypophysis?

Oxytocin and antidiuretic hormone (ADH) are stored there.

What is secreted by the intermediate lobe of the pituitary gland?

melanocyte-stimulating hormone (MSH).

How is blood supplied to the anterior pituitary?

The hypothalamic-hypophysial portal system (microcirculation)

What is the hypothalamic-hypophysial portal system?

A specialized vascular network connecting the hypothalamus to the anterior pituitary gland

Through which vessels does blood first pass in the hypothalamic-hypophysial portal system?

Through portal veins in the hypothalamus

Why does blood pass through the hypothalamus before reaching the anterior pituitary?

To pick up releasing hormones or inhibitory hormones or peptides from the hypothalamus

How does the hypothalamus control the anterior pituitary?

By releasing regulating or inhibitory hormones into the blood that reaches the anterior pituitary

Why is the pituitary gland referred to as the master gland?

Because it releases several hormones that control the activity of other glands

What role does the hypothalamus play relative to the pituitary gland?

It acts as the master switch, while the pituitary gland acts as the transponder, responding to hypothalamic signals

What is the hypothalamus considered in the endocrine system?

The master switchboard

What types of hormones or factors does the hypothalamus produce?

releasing factors (RF or RH) and inhibitory factors (IF or IH).

What is the function of the hypothalamus regarding circulating hormone levels?

It senses the level of circulating hormones and increases production of releasing factors if the levels drop

Where do the releasing factors (RF) from the hypothalamus go?

They pass directly to the anterior lobe of the pituitary

What do releasing factors stimulate in the anterior pituitary?

The synthesis and secretion of tropic hormones

What is the pituitary gland considered in the endocrine system?

The transponder

How does the pituitary gland respond to releasing factors?

It produces tropic hormones

What are tropic hormones (TH)?

They are hormones produced by the anterior pituitary that regulate the function of other endocrine glands

Give an example of a tropic hormone and its target gland.

Thyrotropic hormones targets the thyroid gland

What functions does the thyroid gland regulate under the influence of Thyrotropic hormone?

It regulates metabolism, growth, and nutrition in target cells

Give another example of a tropic hormone and its target gland.

Adrenocorticotropic hormone (ACTH) targets the adrenal gland.

What controls the pituitary gland

The hypothalamic-pituitary axis

What role does the hypothalamus play in controlling the pituitary gland?

It is the primary control center for the pituitary gland

Where is the hypothalamus located relative to the pituitary gland?

It is a small gland adjacent to the pituitary gland

How is the hypothalamus connected to the pituitary gland?

Via the “pituitary stalk” connector

What hormones are synthesized by the hypothalamus?

ADH (vasopressin) and oxytocin.

Where are ADH and oxytocin stored and released from?

They are stored and released from the posterior pituitary gland

What is negative feedback in hormone regulation?

It is when an increase in a product causes a decrease in the activity of the system, inhibiting it

What is positive feedback in hormone regulation?

It is when an increase in a product causes an increase in the activity of the system, amplifying it

When does positive feedback in the body stop?

When negative feedback takes over, such as after a baby is delivered

What is the role of oxytocin during labor?

It stimulates contractions during labor ("push it").

What other process is oxytocin involved in after labor?

Lactation

What happens to T4 levels in hyperthyroidism?

They are high

What happens to T4 levels in hypothyroidism?

They are low

What is primary disease in hormone abnormalities?

It is due to a disease of the endocrine gland producing the hormone, such as the thyroid gland