Endocrine System Overview

Endocrine System

• The endocrine and nervous systems work together to regulate homeostasis.
• The nervous system handles short-term "crisis management".
• The endocrine system manages longer-term metabolic functions through hormones.
• Endocrine cells release hormones into interstitial fluid, affecting target cells.

Endocrine System Overview

• Endocrine system consists of all endocrine cells and tissues.
• Hormones are categorized by chemical structure: amino acid derivatives, peptide hormones, steroids, and eicosanoids.
• Hormone activity is regulated by neural activity, sometimes positive feedback, but mostly complex negative feedback.

Hypothalamus and Endocrine Regulation

• The hypothalamus regulates endocrine and neural activities.
• It controls the adrenal medulla (a component of the sympathetic nervous system).
• It makes hormones (ADH and oxytocin), released by the neurohypophysis (posterior lobe).
• It controls the adenohypophysis (anterior lobe).

Pituitary Gland

• The pituitary gland produces nine peptide hormones.
• Some are produced by the hypothalamus and released at the neurohypophysis.
• Other hormones are produced by the adenohypophysis.

Neurohypophysis

• The neurohypophysis contains axons of hypothalamic neurons.
• Neurons produce hormones like antidiuretic hormone (ADH) and oxytocin.
• ADH decreases water loss in the kidneys.
• Oxytocin affects uterus and mammary glands.

Adenohypophysis

• The adenohypophysis has different parts (pars distalis, pars intermedia, and pars tuberalis).
• It's highly vascularised.
• Hypothalamic regulatory factors (releasing and inhibiting hormones) control its endocrine cells.

Pituitary Hormones

• TSH (thyroid-stimulating hormone) triggers thyroid hormone release.
• ACTH (adrenocorticotropic hormone) stimulates glucocorticoid release.
• FSH (follicle-stimulating hormone) regulates estrogen/sperm production.
• LH (luteinizing hormone) controls ovulation and hormone production.
• PRL (prolactin) aids in mammary gland development and milk production.
• GH (growth hormone) stimulates cell growth and replication.
• MSH (melanocyte-stimulating hormone) stimulates melanin production.

Thyroid Gland

• The thyroid gland is positioned below the thyroid cartilage.
• It has two lobes connected by an isthmus.
• Follicular cells make thyroglobulin and thyroid hormones (T3 and T4).
• TSH stimulates the release of these hormones.

Thyroid Follicles and Thyroid Hormones

• Thyroid follicles contain thyroglobulin with thyroid hormones.
• Thyroid hormones (T3 and T4) are released into the circulation.

C Thyrocytes of the Thyroid Gland

• Follicular cells make calcitonin.
• Calcitonin reduces calcium ion concentration in fluids.
• Calcitonin works opposite to parathyroid hormone.

Parathyroid Glands

• Four parathyroid glands are on the thyroid.
• Principle cells produce parathyroid hormone (PTH) to increase calcium.
• PTH increases osteoclast activity, limits calcium loss via urine, and promotes calcium absorption.

Thymus

• The thymus produces thymosins, promoting immune system development.

Suprarenal Glands

• The suprarenal glands rest above each kidney.
• The cortex makes corticosteroids (mineralocorticoids, glucocorticoids, and androgens).
• The medulla makes epinephrine and norepinephrine.

Endocrine Functions of Kidneys and Heart

• Kidney cells produce renin, erythropoietin, and calcitriol.
• Renin helps regulate blood pressure.
• Erythropoietin increases red blood cell production.
• Calcitriol controls calcium/phosphate absorption.
• Heart cells produce ANP and BNP to regulate blood volume/pressure.

Pancreas (Digestive/Endocrine)

• The pancreas makes exocrine and endocrine secretions.
• Islets of Langerhans (clusters of cells) produce hormones like insulin and glucagon.
• Insulin lowers blood glucose.
• Glucagon raises blood glucose (increases glycogen breakdown, glucose synthesis).
• Somatostatin inhibits insulin and glucagon.

Digestive System/Endocrine

• Digestive tract, liver, and pancreas produce exocrine secretions.
• These are essential for digestion and absorption.

Testes

• Interstitial cells in the testes produce androgens like testosterone.
• Testosterone affects sperm production, secondary sexual characteristics, influences the reproductive tract, and stimulates muscle growth.
• Inhibin, made by nurse cells, interacts with FSH from the anterior pituitary.

Ovaries

• Oocytes develop in follicles.
• Follicle cells produce estrogens (estradiol).
• Estrogen helps with oocyte maturation, uterine lining growth.
• Inhibin controls FSH release.
• After ovulation, corpus luteum makes estrogens and progestins (progesterone).
• Progesterone prepares the uterus for implantation.

Pineal Gland

• Pinealocytes in the pineal gland produce melatonin, a hormone that influences circadian rhythms and reduces reproductive hormone production.

Hormones and Aging

• The endocrine system shows relatively few changes with age.
• The most significant changes are puberty associated hormone increases and the menopause-related hormone decreases.

Clinical Terms (Endocrine)

• Diabetes insipidus
• Diabetes mellitus (Type 1/Type 2)
• Goiter
• Myxedema

Explore the intricacies of the endocrine system in this quiz. Understand how it interacts with the nervous system to maintain homeostasis, the types of hormones produced, and the regulatory role of the hypothalamus. Test your knowledge on how these components work together to influence bodily functions.