19. Chemical Coordination and Integration

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Why are endocrine glands called duct-less glands?

They do not have ducts

Endocrine gland secretions are called _______.

hormones

What is the current scientific definition of hormones?

Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts.

What is the classical definition of hormones?

A chemical produced by endocrine glands and released into the blood and transported to a distantly located target organ.

___________ possess very simple endocrine systems with few hormones whereas a large number of chemicals act as hormones and provide coordination in the ____________.

(vertebrates / invertebrates)

Invertebrates possess very simple endocrine systems with few hormones whereas a large number of chemicals act as hormones and provide coordination in the vertebrates.

Hypothalamus

Pineal

Pituitary

Thyroid and parathyroid

Thymus

Pancreas

Adrenal

Ovary (in females)

Testis (in males)

What parts of the human body comprise the endocrine system?

The endocrine glands and hormone producing diffused tissues/cells located in different parts of our body constitute the endocrine system.

Where is the hypothalamus located?

the hypothalamus is the basal part of diencephalon, forebrain.

The hypothalamus contains several groups of neurosecretory cells called ________ which produce hormones.

The hypothalamus contains several groups of neurosecretory cells called nuclei which produce hormones.

What are nuclei (with regards to the hypothalamus)?

The hypothalamus contains several groups of neurosecretory cells called nuclei which produce hormones.

What is the role of the hormones secreted by the hypothalamus?

These hormones regulate the synthesis and secretion of pituitary hormones.

What are the two types of hormones secreted by the hypothalamus?

1. Releasing hormones (which stimulate secretion of pituitary hormones)

2. Inhibiting hormones (which inhibit secretions of pituitary hormones)

What is the full form of GnRH?

Gonadotrophin releasing hormone

What is the function of GnRH (Gonadotrophin releasing hormone)?

It stimulates the pituitary synthesis and release of gonadotrophins.

What is the function of somatostatin?

It inhibits the release of growth hormone from the pituitary.

Which gland synthesises GnRH?

Hypothalamus (hypothalamic neurons)

Which gland synthesises somatostatin?

Hypothalamus (hypothalamic neurons)

In hypothalamus, where do hormones originate, and how are they released?

These hormones originating in the hypothalamic neurons, pass through axons and are released from their nerve endings.

How do hypothalamic hormones reach the anterior pituitary gland?

These hormones reach the pituitary gland through a portal circulatory system and regulate the functions of the anterior pituitary.

How do hypothalamic hormones reach the posterior pituitary gland?

The posterior pituitary is under the direct neural regulation of the hypothalamus.

(The nerve endings from the hypothalamus terminate inside the posterior pituitary gland)

Hypothalamus

Hypothalamic neurons

Portal circulation

Posterior pituitary

Anterior pituitary

Where is the pituitary gland located? How is it connected to the hypothalamus?

The pituitary gland is located in a bony cavity called sella tursica.

It is attached to hypothalamus by a stalk.

The pituitary gland is anatomically divided into which two parts?

1. adenohypophysis

2. neurohypophysis

Adenohypophysis consists of two portions, which are?

1. Pars distalis

2. Pars intermedia

What is the pars distalis commonly known as?

It is commonly called anterior pituitary.

Which 7 hormones are produced by the pituitary gland?

PMT FLAG

1. Prolactin (PRL)

2. Melanocyte stimulating hormone (MSH)

3. Thyroid stimulating hormone (TSH)

4. Follicle stimulating hormone (FSH)

5. Luteinizing hormone (LH)

6. Adrenocorticotrophic hormone (ACTH)

7. Growth hormone (GH)

Which hormone is produced in the pars intermedia?

Melanocyte stimulating hormone (MSH)

How are the pars intermedia and pars distalis related in humans?

In humans, the pars intermedia is almost merged with pars distalis.

What is pars nervosa?

The one part that makes up neurohypophysis

What is the common name of neurohypophysis (pars nervosa)?

posterior pituitary

Which are the two hormones released by pars nervosa?

1. Vasopressin

2. Oxytocin

Where are oxytocin and vasopressin synthesized?

Hypothalamus

Where are oxytocin and vasopressin secreted?

Pituitary gland

Where is GH (growth hormone) produced and secreted?

Pituitary gland

Where is Prolactin (PRL) produced and secreted?

Pituitary gland

Where is TSH (thyroid stimulating hormone) produced and secreted?

Pituitary gland

Where is ACTH (adrenocorticotrophic hormone) produced and secreted?

Pituitary gland

Where is LH (luteinizing hormone) produced and secreted?

Pituitary gland

Where is FSH (follicle stimulating hormone) produced and secreted?

Pituitary gland

Where is MSH (melanocyte stimulating hormone) produced and secreted?

Pituitary gland (pars intermedia)

Over-secretion of GH during development leads to what?

Over-secretion of GH stimulates abnormal growth of the body leading to gigantism.

Low secretion of GH leads to what?

low secretion of GH results in stunted growth resulting in pituitary dwarfism.

Excess secretion of growth hormone in adults leads to what?

Excess secretion of growth hormone in adults especially in middle age can result in severe disfigurement (especially of the face) called Acromegaly.

What is acromegaly?

Excess secretion of growth hormone in adults especially in middle age can result in severe disfigurement (especially of the face) called Acromegaly.

How dangerous is acromegaly?

It may lead to serious complications, and premature death if unchecked.

How quickly can acromegaly be diagnosed?

The disease is hard to diagnose in the early stages and often goes undetected for many years, until changes in external features become noticeable.

What is the function of prolactin?

Prolactin regulates the growth of the mammary glands and formation of milk in them.

What is the function of Thyroid Stimulating Hormone?

TSH stimulates the synthesis and secretion of thyroid hormones from the thyroid gland.

What is the function of Adrenocorticotrophic hormone?

ACTH stimulates the synthesis and secretion of steroid hormones called glucocorticoids from the adrenal cortex.

What are gonadotrophins?

LH and FSH stimulate gonadal activity and hence are called gonadotrophins.

What is the function of LH in males?

In males, LH stimulates the synthesis and secretion of hormones called androgens from testis.

What is the function of FSH in males?

In males, FSH and androgens regulate spermatogenesis.

What is the function of LH in females?

In females, LH induces ovulation of fully mature follicles (graafian follicles) and maintains the corpus luteum.

How is corpus luteum formed in females?

It is formed from the remnants of the graafian follicles after ovulation.

What is the function of FSH in females?

FSH stimulates growth and development of the ovarian follicles in females.

What is the function of MSH (melanocyte stimulating hormone)?

MSH acts on the melanocytes (melanin containing cells) and regulates pigmentation of the skin.

What is the function of oxytocin in general?

Oxytocin acts on the smooth muscles of our body and stimulates their contraction.

What is the function of oxytocin in females?

In females, it stimulates a vigorous contraction of uterus at the time of child birth, and milk ejection from the mammary gland.

What is the function of vasopressin?

Vasopressin acts mainly at the kidney and stimulates resorption of water and electrolytes by the distal tubules and thereby reduces loss of water through urine (diuresis).

What is the full form of ADH?

Anti-diuretic Hormone

What is diuresis?

loss of water through urine

Which hormone is also called anti-diuretic hormone?

vasopressin

What does an impairment affecting synthesis or release of ADH result in?

An impairment affecting synthesis or release of ADH results in a diminished ability of the kidney to conserve water leading to water loss and dehydration.

What is diabetes insipidus?

An impairment affecting synthesis or release of ADH results in a diminished ability of the kidney to conserve water leading to water loss and dehydration. This condition is known as Diabetes Insipidus.

Vocal cord

Parathyroid glands

Trachea

Where is the pineal gland located?

The pineal gland is located on the dorsal side of forebrain.

Which hormone is secreted by the pineal gland?

Pineal secretes a hormone called melatonin

What is the main function of melatonin?

Melatonin plays a very important role in the regulation of a 24-hour (diurnal) rhythm of our body.

For example, it helps in maintaining the normal rhythms of sleep-wake cycle, body temperature.

What are the secondary functions of melatonin? (4 things)

melatonin also influences metabolism, pigmentation, the menstrual cycle as well as our defense capability.

What is the location of the thyroid gland?

The thyroid gland is composed of two lobes which are located on either side of the trachea.

Both the lobes of the thyroid gland are interconnected with a thin flap of connective tissue called _________.

Both the lobes of the thyroid gland are interconnected with a thin flap of connective tissue called isthmus.

What is the isthmus?

Both the lobes of the thyroid gland are interconnected with a thin flap of connective tissue called isthmus.

The thyroid gland is composed of which two types of cells?

The thyroid gland is composed of follicles and stromal tissues.

Each thyroid follicle is composed of _________ ______, enclosing a ________.

Each thyroid follicle is composed of follicular cells, enclosing a cavity.

(sorry idk how else to add this part)

The follicular cells of the thyroid gland secrete which two hormones?

1. tetraiodothyronine or thyroxine (T₄)

2. triiodothyronine (T₃).

Which mineral is essential for the normal rate of hormone synthesis in the thyroid?

Iodine

Iodine is essential for the normal rate of hormone synthesis in the thyroid. Deficiency of iodine in our diet results in what?

Deficiency of iodine in our diet results in hypothyroidism and enlargement of the thyroid gland, commonly called goitre.

What does Hypothyroidism during pregnancy cause?

Hypothyroidism during pregnancy causes defective development and maturation of the growing baby leading to stunted growth (cretinism), mental retardation, low intelligence quotient, abnormal skin, deaf-mutism, etc

What does hypothyroidism cause in adult women?

In adult women, hypothyroidism may cause menstrual cycle to become irregular.

Due to cancer of the thyroid gland or due to development of nodules of the thyroid glands, what happens?

the rate of synthesis and secretion of the thyroid hormones is increased to abnormal high levels leading to a condition called hyperthyroidism which adversely affects the body physiology.

What is hyperthyroidism caused by?

It is due to cancer of the thyroid gland or due to development of nodules of the thyroid glands.

What is exopthalmic goitre?

Exopthalmic goitre is a form of hyperthyroidism, characterised by enlargement of the thyroid gland, protrusion of the eyeballs, increased basal metabolic rate, and weight loss, also called Graves’ disease.

What is Graves’ disease?

Exopthalmic goitre is a form of hyperthyroidism, characterised by enlargement of the thyroid gland, protrusion of the eyeballs, increased basal metabolic rate, and weight loss, also called Graves’ disease.

What is the function of thyroid hormones? (3 things)

1. Thyroid hormones play an important role in the regulation of the basal metabolic rate. Thyroid hormones control the metabolism of carbohydrates, proteins and fats.

2. These hormones also support the process of red blood cell formation.

3. Maintenance of water and electrolyte balance is also influenced by thyroid hormones.

Thyroid gland secretes a hormone other than T₄ or T₃, which is?

Thyroid gland also secretes a protein hormone called thyrocalcitonin (TCT).

Where is Thyrocalcitonin secreted?

thyroid gland