Endocrine

Question 1

Endocrine signaling involves

Answer 1

1. Regulated secretion of an extracellular signaling molecule, called a hormone, into the extracellular fluid.
2. Diffusion of the hormone into blood and its circulation throughout the body. 3.Diffusion of the hormone from blood to the extracellular space and binding to a specific receptor within cells of a target organ.

Question 2

Hormones in Hypothalamus

Answer 2

•Thyrotropin-releasing hormone •Corticotropin-releasing hormone •Growth hormone–releasing hormone •Growth hormone–inhibiting hormone •Gonadotropin-releasing hormone •Dopamine or prolactin inhibiting factor

Question 3

Hormones in Anterior pituitary

Answer 3

•Growth hormone (GH)•Thyroid-stimulating hormone(TSH)•Adrenocorticotropic hormone (ACTH)•Prolactin(PL)•Follicle-stimulating hormone (FSH)•Luteinizing hormone (LH)

Question 4

Hormones in Parathyroid glands

Answer 4

Parathyroid hormone (PTH)

Question 5

Hormones in Thyroid gland

Answer 5

•Tetraiodothyronine(T4; thyroxine)•Triiodothyronine (T3)•Calcitonin

Question 6

Hormones in Islets of Langerhans (endocrine pancreas)

Answer 6

•Insulin•Glucagon•Somatostatin

Question 7

Hormones in Ovaries

Answer 7

• Estradiol-17β
• Progesterone
• Inhibin

Question 8

Hormones in Testes

Answer 8

•Testosterone•Antimüllerianhormone (AMH)•Inhibin

Question 9

Classification of hormones

Answer 9

• Depending upon the chemical nature

- Depending upon the mechanism of action

Question 10

A. Depending upon the chemical nature

Answer 10

1. Amines or amino acid derivativesCatecholamines (epinephrine and norepinephrine) and Thyroxine (T4) and Triiodothyronine (T3).
2. Proteins and polypeptides:Posterior pituitary hormones (antidiuretic hormone and oxytocin)Insulin,Glucagon, Parathormone, anterior pituitary hormones.
3. Steroid hormones. Glucocorticoids, Mineralocorticoids, Sex steroids and Vitamin D.

Question 11

B. Depending upon the mechanism of action

Answer 11

1. Group I hormones:•These act by binding to intracellular receptor-form a hormone–receptor complex. •Includes steroid, retinoid and thyroid hormones.
2. Group II hormones.These involve second messenger to mediate their effect

Question 12

Hormone transport

Free/Unbound form:

Answer 12

Water-soluble hormones (peptides and catecholamines) are dissolved in the plasma and transported from their sites of synthesis to target tissues, where they diffuse out of the capillaries, into the interstitial fluid, and ultimately to target cells.

Question 13

Hormone transport Bound form

Answer 13

Steroid and thyroid hormones circulate in the blood while being mainly bound to plasma proteins.

Question 14

Characteristics of hormone receptors

Answer 14

1. Receptor specificity
2. Change in receptor number
   a. Downregulation
   b. Upregulation

Question 15

Mechanism of action of hormones

Answer 15

▪Action through change in the membrane permeability.▪Action through effect on gene expression by binding of hormones with intracellular receptors.▪Action through secondary messengers which activate intracellular enzymes when hormones combine with membrane receptors.▪Action through tyrosinkinase activation.

Question 16

Action through change in membrane permeability

Answer 16

•Hormones + receptors present in the cell membrane -cause conformational change in the protein of the receptors.•Either opening or closing of the ion channels (such as Na+channels, K+channels and Ca2+ channels). •The movement of ions through Ca2+channels causes the subsequent effect, e.g. adrenaline, noradrenaline act by this mechanism.

Question 17

Action through effect on gene expression by binding of hormones with intracellular receptors

Answer 17

•Steroid hormones, retinoids and thyroid hormones.•These hormones are lipophilic in nature and can easily pass across the cell membrane.•They act through intracellular receptors located either in the cytosol or in the nucleus.

Question 18

Action through effect on gene expression by binding of hormones with intracellular receptors

Answer 18

1.Transport2.Internalization3.Receptor–hormone complex4.Conformational change5.Receptor–hormone complex diffuses into the nucleus and binds on the specific region of the DNA (HRE)-initiates gene transcription.6.Binding of the receptor–hormone complex to DNA alters the rate of transcription of messenger RNA (mRNA).7.The mRNA diffuses in the cytoplasm –translation at ribosomes-new proteins formed.