Endocrine System: Structure and Function PDF

8/27/24, 6:13 PM Platform | Study Fetch The Endocrine System: Structure and Function (00:00 - 00:19) The endocrine system is a chemical messenger system that produces hormones to regulate various bodily functions. Horm...

8/27/24, 6:13 PM Platform | Study Fetch The Endocrine System: Structure and Function (00:00 - 00:19) The endocrine system is a chemical messenger system that produces hormones to regulate various bodily functions. Hormones regulate metabolism, growth, development, sex, reproduction, mood, and other aspects. (00:19 - 00:29) This lesson will cover an overview of the endocrine system, the endocrine-specific glands and their hormones, and other organ systems that secrete hormones. (00:29 - 00:39) The endocrine system is made up of glands located throughout the body, including the thyroid, pituitary, parathyroid, ovaries, and testes. These glands release signals that coordinate with other tissues to maintain various bodily functions. (00:39 - 00:56) The endocrine glands release hormones that help coordinate the efforts of different tissues to maintain functions like blood pressure and sexual development. (00:56 - 01:08) Hormones are messengers that can tell cells to start dividing, synthesize certain proteins, and maintain many bodily functions. (01:08 - 01:28) There are three main types of hormone signaling: Paracrine signaling: A cell targets a nearby cell with a hormone. Autocrine signaling: A cell releases a hormone that binds to receptors on that same cell. Endocrine signaling: A hormone is released into the bloodstream and travels to a distant tissue. (01:28 - 01:44) Every cell needs a way to receive and respond to a signal, which is called the signal transduction pathway. (01:44 - 02:13) One type of signal transduction is through receptor tyrosine kinases: These are cell surface proteins that dimerize when a ligand binds. The dimerization causes the receptors to phosphorylate each other, triggering downstream enzymes and a signal to the nucleus. (02:13 - 02:35) G protein-coupled receptors are another type of signal transduction: The receptor is connected to an α, β, and γ subunit. When the receptor is triggered, the α subunit exchanges GDP for GTP and dissociates, going on to trigger a response. (02:35 - 02:50) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2ccef069b6d6b89c5eb5/document?go=note 1/7 8/27/24, 6:13 PM Platform | Study Fetch Steroid hormones are different - they can directly pass through the plasma membrane and bind to receptors in the cytoplasm. (02:50 - 04:02) The steroid hormone-receptor complex then translocates to the nucleus to regulate gene expression and cellular responses. Hormones and the Endocrine System Cellular Responses of Hormones (00:04:02 - 00:04:17) Hormones can travel to the nucleus and act as transcription factors, changing gene expression Cellular responses to hormones are generally slower but longer-lasting compared to G protein-coupled receptors and receptor tyrosine kinases Classes of Hormones (00:04:17 - 00:04:28) Peptide Hormones: Long chains of amino acids, often binding to receptor tyrosine kinases Example: Insulin Amino Acid-Derived Hormones (00:04:28 - 00:04:44) Amino Acid-Derived Hormones: Individual amino acids modified to serve as signaling molecules Examples: Epinephrine, norepinephrine, melatonin Steroid-Derived Hormones (00:04:44 - 00:05:18) Steroid-Derived Hormones: Four-membered ring structures, less polar, can more easily pass through plasma membrane Examples: Testosterone, estradiol Steroid hormones can bind to receptors and travel to the nucleus to act as transcription factors Organs of the Endocrine System (00:05:29 - 00:05:41) Pineal gland, pituitary gland, hypothalamus, thyroid, parathyroid, thymus, pancreas, adrenal glands, gonads, placenta https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2ccef069b6d6b89c5eb5/document?go=note 2/7 8/27/24, 6:13 PM Platform | Study Fetch Exocrine vs. Endocrine Glands (00:05:41 - 00:06:15) Exocrine Glands: Secrete substances into a lumen (e.g., pancreas digestive juices) Endocrine Glands: Secrete substances directly into the bloodstream Endocrine Functions of Non-Endocrine Organs (00:06:15 - 00:06:33) Heart, kidneys, stomach, small intestine can also have endocrine functions and release substances into the blood Important Endocrine Axes (00:06:45 - 00:07:23) 1. Hypothalamus-Pituitary-Adrenal (HPA) Axis: Regulates cortisol levels and stress response 2. Renin-Angiotensin-Aldosterone System (RAAS): Regulates fluid and electrolyte balance The Endocrine System: Pituitary Gland and Hormones (00:07:23 - 00:07:33) The kidney module discussed the uptake of sodium and water, which helps regulate volume and blood pressure. (00:07:33 - 00:07:46) We will now discuss the endocrine glands and their hormones. There are three main types of endocrine stimuli: Humoral stimuli from the bloodstream Neuro stimuli directly from nerve fibers Hormonal stimuli from hormones released by other glands (00:07:46 - 00:07:59) The pituitary gland has two lobes: The posterior lobe secretes neural hormones made by the hypothalamus. The anterior lobe secretes its own hormones, signaled by the hypothalamus through the hypothalamic- pituitary portal system. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2ccef069b6d6b89c5eb5/document?go=note 3/7 8/27/24, 6:13 PM Platform | Study Fetch (00:07:59 - 00:08:11) The posterior pituitary secretes: Oxytocin, which triggers contractions during childbirth, milk production, and promotes bonding. ADH (antidiuretic hormone), which regulates the osmolarity of the blood. (00:08:11 - 00:08:25) The hypothalamus synthesizes hormones that travel down axons into the posterior pituitary, where they are released. This is different from the anterior pituitary, which secretes its own hormones. (00:08:25 - 00:08:38) The anterior pituitary secretes several hormones: Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Adrenocorticotropic hormone (ACTH) Thyroid-stimulating hormone (TSH) Prolactin Growth hormone (00:08:38 - 00:08:50) The hypothalamus releases hormones into the hypothalamic-pituitary portal system, which then trigger the release of hormones from the anterior pituitary. (00:08:50 - 00:09:01) The hypothalamus releases hormones that directly stimulate the anterior pituitary to secrete its own hormones. (00:09:01 - 00:09:19) Oxytocin from the posterior pituitary triggers contractions during childbirth, milk production, and promotes bonding. ADH from the posterior pituitary regulates the osmolarity of the blood. (00:09:19 - 00:09:36) ADH inhibits water loss and increases water absorption, helping to regulate the osmolarity of the blood. This contrasts with aldosterone, which regulates blood volume and pressure. (00:09:36 - 00:09:52) The anterior pituitary secretes: Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Adrenocorticotropic hormone (ACTH) Thyroid-stimulating hormone (TSH) Prolactin Growth hormone (00:09:52 - 00:10:04) Mnemonic for anterior pituitary hormones: "Flat Pig" (FSH, LH, ACTH, TSH, Prolactin, Growth hormone) (00:10:04 - 00:10:19) FSH contributes to follicle growth in females and sperm maturation in males. LH maintains the corpus luteum and produces testosterone. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2ccef069b6d6b89c5eb5/document?go=note 4/7 8/27/24, 6:13 PM Platform | Study Fetch (00:10:19 - 00:10:33) Mnemonic for FSH: "FSH looks like fish, which should remind you that in males FSH stimulates the production of sperm which swim like fish." (00:10:33 - 00:10:47) LH produces testosterone, which makes men large and hairy. (00:10:47 - 00:10:58) The thyroid gland secretes thyroid hormone, which is one of the main mechanisms for controlling metabolism. It produces both T3 and T4, with T4 being the inactive form that is converted to T3 in peripheral tissues. (00:10:58 - 00:11:23) Thyroid hormone is the main source of metabolic stimulation in the body. Patients who are hypothyroid often experience symptoms related to a slower metabolism. (00:11:23 - 00:11:37) The conversion of T4 to T3 in peripheral tissues is an important process for regulating metabolism. Thyroid Gland and Metabolism (00:11:37 - 00:11:59) If the thyroid gland is not producing enough thyroid hormone (T3 or T4), the body will slow down and essentially go into a state of stasis Without proper thyroid hormone, the body's metabolism slows down and shuts down Hyperthyroidism (00:11:59 - 00:12:13) When there is too much thyroid hormone (hyperthyroidism): People will have diarrhea They'll be bouncing off the walls, talking a mile a minute They'll be hot all the time The thyroid gland regulates metabolism and energy utilization in the body Parathyroid Gland (00:12:13 - 00:12:41) The parathyroid glands secrete parathyroid hormone Parathyroid hormone regulates calcium and phosphate levels in the blood It does this by: Releasing calcium from bones Reducing calcium clearance Activating vitamin D, which helps absorb calcium from the gut Parathyroid hormone is the main way the body increases calcium levels in the blood https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2ccef069b6d6b89c5eb5/document?go=note 5/7 8/27/24, 6:13 PM Platform | Study Fetch Adrenal Glands (00:12:51 - 00:14:35) Adrenal Cortex The adrenal cortex has 3 layers that secrete different hormones: Outer layer: Aldosterone (a mineralocorticoid) Middle layer: Cortisol (a glucocorticoid) Inner layer: Androgens The adrenal cortex is the primary endocrine component of the adrenal gland Adrenal Medulla The adrenal medulla is an extension of the sympathetic nervous system It releases catecholamines (e.g. epinephrine, norepinephrine) in response to stress and the "fight-or-flight" response Adrenal Gland Hormones Corticosteroids (mineralocorticoids and glucocorticoids) Androgens (e.g. testosterone) Cortisol Aldosterone Adrenal Gland Importance (00:14:35 - 00:15:26) In females, adrenal androgen production is more important, as it can impact sexual development and sex differentiation if there are issues In males, adrenal androgens are less important since the testes produce most of the androgens Key Points: Thyroid hormone regulates metabolism Parathyroid hormone controls calcium/phosphate levels Adrenal glands have cortex and medulla with distinct functions Adrenal hormones include corticosteroids, androgens, cortisol, aldosterone Adrenal androgens are more crucial for female development (Video Timestamps in Parentheses) The Endocrine System (00:15:39 - 00:15:51)The pineal gland secretes melatonin, one of the main hormones that regulates the sleep- wake cycle. Pineal tumors can occur in children. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2ccef069b6d6b89c5eb5/document?go=note 6/7 8/27/24, 6:13 PM Platform | Study Fetch (00:15:51 - 00:16:03)The pancreas secretes glucagon and insulin. Glucagon increases blood glucose, while insulin decreases it. (00:16:03 - 00:16:14) The alpha cells of the pancreas secrete glucagon. The beta cells secrete insulin. The delta cells secrete somatostatin. (00:16:14 - 00:16:28) The ovaries produce estrogen and progesterone. The testes produce testosterone. (00:16:28 - 00:16:52) The adipose cells secrete leptin, a signal for the amount of fat stored in the body. The kidneys secrete erythropoietin, which promotes red blood cell formation. (00:16:52 - 00:17:14) Kidney failure can lead to anemia due to decreased erythropoietin production. (00:17:14 - 00:17:49)The Renin-Angiotensin-Aldosterone System (RAAS) Renin is released by the kidneys and converts angiotensinogen (from the liver) to angiotensin I. Angiotensin-converting enzyme (ACE) in the lungs converts angiotensin I to angiotensin II. Angiotensin II stimulates the adrenal glands to release aldosterone. Aldosterone travels back to the kidneys and increases sodium and water reabsorption, expanding the vascular volume. (00:17:49 - 00:19:12) Angiotensin II also causes vasoconstriction. The RAAS is a major regulator of blood volume and pressure. Bones secrete osteocalcin, which promotes insulin release and increases metabolic activity. (00:19:12 - 00:19:24) Osteocalcin is a good marker for osteoblast activity in the body. (00:19:24 - 00:19:28)Congratulations! You have now mastered the endocrine system. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2ccef069b6d6b89c5eb5/document?go=note 7/7