Endocrinology 28th October 2016 The Adrenal Cortex and Medulla Role of adrenal glands and hormone is to regulate the body's response to stress. The Adrenal System Perceived Danger ! Hypothalamus corticotrophin-releasing hormone (CRH) vasopressin Overview of organs involved Hypothalamus - receives input from higher centres of perceived danger and stress Aston University Anterior Pituitary It then relays the signal to the AP, which causes it to release hormones to adrenal gland. adrenocorticotropic hormone (ACTH) Adrenal Gland glucocorticoids (cortisol) epinephrine & norepinephrine, Stress Response The adrenal gland then produces hormones of its own, which elicit physiological response to stress and produce negative feedback to regulate their production. The Adrenal Glands Ad = on top off Renal = kidney The adrenal glands are positioned onto of the kidneys What they consist of: Outer capsule-> outer cortex-> inner medulla Adrenal Cortex The adrenal cortex consists of 3 layers: zona glomerulosa (outer) The Adrenal Cortex produces several different adrenocortical hormones: zona fasciculata (middle and largest) zona reticularis (inner) Zona glomerulosa: - Mineralocorticoids (aldosterone - mineral (electrolyte) balance) Zona fasciculate: - Glucocorticoids (cortisol - nutrient me tabolism and stress)
Endocrinology 28th October 2016 Zona reticularis: - Sex hormones identical or similar to those produced by the gonads (dehydroepiandrosterone) Each produce different classes of the different adrenal hormones Adrenal Medulla Adrenal medullary cells are modified sympathetic postganglionic neurons, which have lost their axons and dendrites. Instead function as endocrine chromaffin cells, which are innervated by preganglionic neurons of sympathetic ganglion. Chromaffin cells secrete catecholamines, which are mainly adrenalin(e) and noradrenalin(e) (epinephrine and norepinephrine) Actions are via the adrenergic (adrenoceptor) system, which is similar to the peripheral sympathetic nervous system - emergency 'Fight or flight' responses Steroidogenic Pathway Cholesterol 1 Pregnenolone Progesterone (female sex hormone) 11-Deoxycorticosterone Corticosterone Aldosterone Mineralocorticoid (adrenal cortex hormone) >17-Hydroxypregnenolone >17-Hydroxyprogesterone Deoxycortisol Cortisol Glucocorticoid (adrenal cortex hormone) Dehydroepiandrosterone (adrenal cortex hormone) Androstenedione Testosterone Androgens (male sex hormones) Estrone Estradiol Estriol Estrogens (female sex hormones) @ Cengage Learning Adrenal hormones are steroid hormones - generated by different downstream pathways. All generated from the same precursor cholesterol!
Endocrinology 28th October 2016 Stress 1 The HPA Axis Hypothalamus Circadian Rhythym corticotropin-releasing hormone (CRH) Anterior Pituitary Hypothalamus - receives from higher centres and circadian rhythm - biological responses to a body clock - induce the release of CRH ston University adrenocorticotropic hormone (ACTH) Adrenal Cortex 1 cortisol blood glucose, amino acids & fatty acids CRH to AP and stimulate secretion ofACTH ACTH goes to adrenal cortex to stimulate release of cortisol - increase levels of things and negatively regulates its production - inhibits production Cell type Corticotroph Pituitary population Product 15-20% ACTH b-lipotropin Target Adrenal gland Adipocytes Melanocytes Thyrotroph 3-5% Gonadotroph 10-15% Somatotroph 40-50% Lactotroph 10-15% Aston University TSH LH, FSH GH PRL Thyroid gland Gonads All tissues, liver Breasts gonads Hormone (CRH) It is a peptide hormone with 41 amino acids Anterior Pituitary Cells and Hormones Most cells of AP are somatotrophic - release growth hormones 5th of cells in AP secrete ACTH Corticotrophin-Releasing Parvocellular neuroendocrine cells