1 ENDOCRINE PHYSIOLOGY PSL 223 PSL 223

Dr. S.Bashir2 Objectives By the end of this part of the course the student should be able to: By the end of this part of the course the student should be able to: 1- Define the terms endocrine, hormone, receptor. 1- Define the terms endocrine, hormone, receptor. 2- Describe the homeostatic roles of the endocrine system. 2- Describe the homeostatic roles of the endocrine system.

Dr S.Bashir3 Adrenal Gland Anatomical position: on top of the kidney Anatomical position: on top of the kidney The cortex : 80% of the gland’s mass. The cortex : 80% of the gland’s mass. - Secretes adrenocorticoids. - Secretes adrenocorticoids. The medulla: 20%. The medulla: 20%. - Secretes chatecholamines.

Adrenal cortical hormones : 1. Cortisol. 1. Cortisol. 2. Aldosterone. 2. Aldosterone. 3. Androgens. 3. Androgens. 4

Physiological actions of cortisol 5

Dr S.Bashir6 Abnormal States Cortisol Excess  Cortisol Excess  Cushing's’ Syndrome. Cushing's’ Syndrome. Deficiency  Addison's’ disease. Deficiency  Addison's’ disease.

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8 Adrenal Medulla 20% total mass of adrenal gland. 20% total mass of adrenal gland. Contains chromaffin cells and secretes catecholamines: Contains chromaffin cells and secretes catecholamines: –80% epinephrine –20% norepinephrine –<1% dopamine

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Dr S. Bashir11 Water & electrolytes homeostasis. Water & electrolytes (Na & K) homeostasis involves the following hormones:- Water & electrolytes (Na & K) homeostasis involves the following hormones:- ADH  water retention. ADH  water retention. Aldosterone  Na + & water retention & K + excretion. Aldosterone  Na + & water retention & K + excretion. Angiotensin II  water retention Angiotensin II  water retention (& vasoconstriction). ANP which cause Na + excretion. ANP which cause Na + excretion.

12 Water & electrolyte homeostasis Antdiuretic Hormone (ADH). Antdiuretic Hormone (ADH). Aldosterone Aldosterone Angiotensin II Angiotensin II Atrial Naturetic Peptide (ANP) Atrial Naturetic Peptide (ANP)

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Dr S. Bashir14 Water & electrolytes homeostasis. Water & electrolytes (Na & K) homeostasis involves the following hormones:- Water & electrolytes (Na & K) homeostasis involves the following hormones:- ADH  water retention. ADH  water retention. Aldosterone  Na + & water retention & K + excretion. Aldosterone  Na + & water retention & K + excretion. Angiotensin II  water retention Angiotensin II  water retention (& vasoconstriction). ANP which cause Na + excretion. ANP which cause Na + excretion.

Dr S.Bashir 15 Calcium homeostasis.

Dr S.Bashir16 Serum Ca Non-filterable Ca: Non-filterable Ca: –Protein bound. ( ≈40%) Filterable:- Filterable:- Complexed Ca ?( ≈ 10%) Complexed Ca ?( ≈ 10%) Ionized Ca ( ≈ 50%) Ionized Ca ( ≈ 50%)

Dr S.Bashir17 Serum Ca Normal total serum Ca: Normal total serum Ca: – mmol/l, (mg% -?) Ionized serum Ca Ionized serum Ca mmol/ l. (mg%?)

Dr S.Bashir18 Ionized Serum Ca It is the fraction which is:- It is the fraction which is:- Biologically active. Biologically active. Hormonally controlled. Hormonally controlled.

Dr S.Bashir19 Figure 26.7 Thyroid gland releases calcitonin Summary of Calcium homeostasis Summary of Calcium homeostasis STIMULUS: Rising blood Ca 2+ level (imbalance) Calcitonin Stimulates Ca 2+ deposition in bones Homeostasis: Normal blood calcium level (about 10 mg/100 mL) Reduces Ca 2+ uptake in kidneys STIMULUS: Falling blood Ca 2+ level (imbalance) Parathyroid glands release parathyroid hormone (PTH) Parathyroid gland Active vitamin D Stimulates Ca 2+ release from bones Increases Ca 2+ uptake in kidneys Increases Ca 2+ uptake in intestines PTH

Dr S.Bashir20 Ca intake Dietary sources? Dietary sources? RDA : g. RDA : g.

Dr S.Bashir21 Parathyroid Glands Anatomical position? Anatomical position?

Dr S.Bashir22 Vitamin-D Vitamin-D 2 ? Vitamin-D 2 ? –Ergocalciferol from plants. Vitamin-D 3 ? Vitamin-D 3 ? –Cholecalciferol from animals.

Dr S.Bashir23 Vitamin –D deficiency Decreased skin synthesis? Decreased skin synthesis? Decreased dietary supply? Decreased dietary supply? Abnormal, hepatic or renal metabolism? Abnormal, hepatic or renal metabolism?

Sun light when and how much? 5–30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen. 5–30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen. Remember UV light does not penetrate glass. Remember UV light does not penetrate glass. Dr S.Bashir24

Dr S.Bashir25 Vitamin- D Deficiency consequences: In children :Rickets  In children :Rickets  abnormal bone development abnormal bone development  abnormal bone histology  abnormal bone histology  weak & deformed bones.  weak & deformed bones. In adults : osteomalacia: delayed mineralization of bone  weak painful bones. In adults : osteomalacia: delayed mineralization of bone  weak painful bones.

Dr S.Bashir26 Rickets

Dr S.Bashir27 Osteomalacia

Calcitonin Hormone secreted by the thyroid gland. Hormone secreted by the thyroid gland. Acts to decrease serum calcium. Acts to decrease serum calcium. 28

29 Thank You Thank You