Endocrine System Function Quiz

Endocrine System Function

• The primary function of the endocrine system is homeostasis, maintaining a stable internal environment.
• Hormones are chemical messengers that facilitate communication between cells, enabling the body to achieve and maintain homeostasis.
• Homeostasis is essential for optimal bodily function, ensuring a stable internal environment despite external changes.

Endocrine System & Homeostasis

• Role of the endocrine system: Regulates and coordinates bodily functions
• Hormone function: Chemical messengers produced by endocrine glands, secreted into the bloodstream, and travel to target cells with specific receptors.
• Homeostasis: Maintenance of a stable internal environment despite external fluctuations.
• Not a function of hormones: Rapid nerve impulse transmission (that's the nervous system)
• Well-functioning endocrine system's effect on homeostasis: Maintains balance and stability, ensuring optimal body functions.
• Long-term regulation: Growth and development.
• Endocrine system's role in metabolism: Regulates energy production, storage, and utilization through hormones like insulin and glucagon.
• Not a short-term function of the endocrine system: Long-term growth and development (that takes time).
• Endocrine system's contribution to reproduction: Produces hormones that regulate sexual development, menstrual cycle, and pregnancy.
• Short-term homeostasis managed by the endocrine system: Blood glucose levels.

Hormone Release and Action

• Hormones are released in response to a stimulus and work to restore balance in the body.
• This process is known as negative feedback.
• Negative feedback mechanisms work to maintain homeostasis, a state of internal equilibrium in the body.

Negative Feedback

• Negative feedback loops are a common regulatory mechanism in biological systems.
• These loops involve a sensor, a control center, and an effector.
• The sensor detects a change in a regulated variable, the control center compares the current value to the setpoint, and the effector takes action to bring the variable back to the setpoint.
• In the case of hormone release, the stimulus acts as the sensor, the endocrine gland acts as the control center, and the hormone acts as the effector.
• The hormone's action will then decrease or remove the original stimulus, completing the negative feedback loop.

Hormone Action

• Hormones only affect specific target tissues that have receptors for the specific hormone.
• Water-soluble hormones, like insulin, cannot cross the cell membrane. They bind to receptors on the cell surface, which triggers a signal transduction cascade within the cell.
• Lipid-soluble hormones, like estrogen, can cross the cell membrane and bind to intracellular receptors in the cytoplasm or nucleus.
• Hormone receptors are constantly being synthesized and broken down, ensuring a balance and responsiveness to changing hormone levels.
• Positive feedback loops amplify a response, while negative feedback loops decrease a response.

Hormone Action

• Hormones only affect specific target tissues that have receptors for that particular hormone.
• Water-soluble hormones bind to receptors on the cell surface.
• Lipid-soluble hormones can pass through the cell membrane and bind to intracellular receptors.
• Receptors are constantly being synthesized and broken down within the cell.
• The body uses positive and negative feedback to regulate hormone levels.
  • Positive feedback enhances the original stimulus, leading to an amplified response.
  • Negative feedback reduces the original stimulus, leading to a decreased response.

Cell Communication Using Hormones

• Endocrine hormones are secreted into the bloodstream and travel throughout the body to target cells.
• Paracrine hormones act on nearby cells within the same tissue.
• Autocrine hormones affect the same cells that produced them.
• Neuroendocrine hormones are secreted from nerve cells and travel through the bloodstream.

Classes of Hormones

• Polypeptides like insulin and growth hormone cannot cross cell membranes. They are water-soluble and interact with receptors on the cell surface.
• Steroid hormones, such as estradiol and testosterone, can cross cell membranes because they are lipid-soluble. They interact with receptors inside the cell.
• Modified amino acids like epinephrine and thyroid hormone are small and water-soluble, allowing them to cross cell membranes.
• Eicosanoids, like prostaglandins, are derived from fatty acids and play a role in inflammation, pain, and fever.

Cell Communication with Hormones

• Endocrine hormones travel through the bloodstream to reach distant target cells.
• Paracrine hormones act locally on nearby cells after being released by endocrine tissue.
• Autocrine hormones act on the same cell that produced them.
• Neuroendocrine hormones are secreted by nerve cells and travel via the bloodstream.

### Classes of Hormones

• Polypeptides are water-soluble and cannot cross cell membranes.
• Steroids are lipid-soluble and can cross cell membranes.
• Modified amino acids are small, water-soluble molecules that can cross cell membranes.
• Eicosanoids are a class of lipids, including prostaglandins, that act as signaling molecules.

Hormone Types

• Hormones are chemical messengers that regulate various bodily functions.
• Circulating hormones travel through the bloodstream to reach target cells throughout the body.
• Local hormones exert their effects in a more localized manner.
• Paracrine hormones act on neighboring cells, influencing their activity without entering the bloodstream.
• Autocrine hormones act on the same cell that secreted them, creating a self-regulatory loop.
• Interleukin-1 is an example of an autocrine hormone that regulates immune responses.

Hormone Types

• Circulating hormones travel throughout the body in the bloodstream. Insulin is an example of a circulating hormone.
• Local hormones have a localized effect.
  • Paracrine hormones act on neighboring cells.
  • Autocrine hormones act on the same cell that secreted them. Interleukin-1 is an example of an autocrine hormone.

Hormone Activation of Target Cells

• Hormones are chemical messengers that activate target cells.
• There are two mechanisms of activation based on hormone solubility:
  • Lipid-soluble hormones (e.g., steroid hormones) can pass through the plasma membrane of target cells.
  • Water-soluble hormones (e.g., protein hormones) cannot pass through the plasma membrane.
• Lipid-soluble hormones bind to receptor proteins located inside the cytoplasm of the target cell.
• Water-soluble hormones bind to specific receptor proteins located on the cell membrane of the target cell.

Water-Soluble Hormone Signaling

• Water-soluble hormones cannot pass through the cell membrane.
• These hormones bind to receptors on the cell surface.
• Receptor binding initiates a signaling pathway within the cell.
• The pathway involves G proteins, adenylyl cyclase, and the secondary messenger cyclic AMP (cAMP).
• Protein kinases are activated by cAMP.

Hypothalamus & Endocrine System

• The hypothalamus is the central regulatory component of the endocrine system.
• The hypothalamus receives input from both neural and hormonal stimuli.
• The hypothalamus integrates these stimuli and sends signals to the pituitary gland.

Hypothalamus Location

• Located at the base of the forebrain, specifically in the diencephalon.

Hypothalamus Structure

• Contains a pituitary stalk that connects to the posterior pituitary gland.

Hypothalamus Functions

• Receives information from the circulatory system regarding temperature, blood sugar levels, and hormones.
• Also receives neuronal input from the autonomic nervous system and emotional centers.
• Based on this input, the hypothalamus secretes hormones that target either the anterior or posterior pituitary gland.

Hypothalamus Blood Supply

• Supplied by the superior hypophyseal artery.
• Has hypophyseal portal vessels that carry a high concentration of hormones to the anterior pituitary.
• Drained by the cavernous sinus.

Hypothalamus Location and Structure

• Located at the base of the forebrain, specifically within the diencephalon.
• Connected to the posterior pituitary gland through the pituitary stalk.

Hypothalamus Functions

• Receives sensory input from the circulatory system regarding temperature, blood sugar levels, and hormones.
• Also receives neuronal input from the autonomic nervous system and areas related to emotions.
• Based on these inputs, the hypothalamus secretes hormones that target either the anterior or posterior pituitary gland.

Hypothalamus Blood Supply

• Supplied by the superior hypophyseal artery.
• Hypophyseal portal vessels, which carry a high concentration of hormones, connect the hypothalamus to the anterior pituitary.
• Blood is drained from the area by the cavernous sinus.

Pituitary Gland Location

• Located in the sella turcica
• Optic chiasma lies directly superior to the pituitary gland

Pituitary Gland Function

• Responsible for releasing hormones after receiving stimulus from the hypothalamus
• Hormones produced by the pituitary gland act on other endocrine organs

Pituitary Gland Blood Supply

• Supplied by the superior hypophyseal artery and hypophyseal portal vessels from the hypothalamus
• Drained by the cavernous sinus
• Hormones enter circulation through the cavernous sinus

Pituitary Gland Location and Function

• Located in the sella turcica, a bony cavity at the base of the skull.
• The optic chiasma, the point where the optic nerves cross, lies directly superior to the pituitary gland.
• Pituitary gland tumors can cause visual changes due to compression on the optic chiasma.
• Pituitary gland releases hormones after receiving signals from the hypothalamus.
• Hormones act on other endocrine organs, regulating various bodily functions.

Pituitary Blood Supply

• Receives blood supply from the superior hypophyseal artery.
• Hypophyseal portal vessels from the hypothalamus deliver hormones to the pituitary gland.
• Blood drains into the cavernous sinus, allowing hormones to enter circulation.

Posterior Pituitary

• Located behind the anterior pituitary
• Connected to the hypothalamus via the pituitary stalk
• Releases antidiuretic hormone (ADH), which acts on the kidneys to regulate water reabsorption
• Also releases oxytocin, involved in uterine contractions during labor and milk ejection
• Supplied by the inferior hypophyseal artery
• Drained by the cavernous sinus, which allows hormones to enter the bloodstream

Posterior Pituitary

• Located behind the anterior pituitary
• Connected to the hypothalamus via the pituitary stalk
• Releases antidiuretic hormone (ADH) and oxytocin
  • ADH acts on the collecting ducts of the kidneys
• Blood supply comes from the inferior hypophyseal artery
• Drained by the cavernous sinus, allows hormones to enter circulation

Hypothalamic-Pituitary-Thyroid Feedback Loop

• The Hypothalamic-Pituitary-Thyroid (HPT) axis is a complex feedback loop that regulates the production and release of thyroid hormones (T3 and T4).
• Thyrotropin-releasing hormone (TRH) is produced by the hypothalamus and acts on the anterior pituitary.
• Low levels of thyroid hormones (T3, T4) trigger the release of TRH, leading to the production of thyroid-stimulating hormone (TSH) by the anterior pituitary.
• TSH travels to the thyroid gland and stimulates the production and release of T3 and T4.
• Once T3 and T4 levels rise, they directly suppress the release of both TRH from the hypothalamus and TSH from the anterior pituitary, creating a negative feedback loop to maintain homeostasis.
• The HPT axis is crucial for maintaining metabolic rate, growth, and development, and ensuring proper function of many other physiological processes within the body.

Hypothalamus and Pituitary Hormones

• The hypothalamus releases hormones that regulate the anterior pituitary gland, which in turn releases other hormones.
• Growth Hormone-Releasing Hormone (GHRH) triggers the anterior pituitary to release Growth Hormone (GH), responsible for growth and development.
• Growth Hormone-Inhibiting Hormone (GHIH) inhibits the release of GH.
• Corticotropin-Releasing Hormone (CRH) stimulates the anterior pituitary to release Adrenocorticotropic Hormone (ACTH), which regulates cortisol production by the adrenal glands.
• Gonadotropin-Releasing Hormone (GnRH) promotes the release of Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH) from the anterior pituitary, which are critical for reproductive processes.
• Prolactin-Releasing Factor (PRF) stimulates the anterior pituitary to release Prolactin, which plays a role in lactation.
• Thyrotropin-Releasing Hormone (TRH) triggers the release of Thyroid-Stimulating Hormone (TSH) from the anterior pituitary, stimulating thyroid hormone production.

Posterior Pituitary Hormones

• Oxytocin is produced in the hypothalamus and released by the posterior pituitary, responsible for uterine contractions during labor and milk ejection during breastfeeding.
• Antidiuretic Hormone (ADH), also produced in the hypothalamus and released by the posterior pituitary, regulates water balance in the body by promoting water retention.

Key Functions of Pituitary Hormones

• Growth Hormone (GH): Promotes growth and development.
• Adrenocorticotropic Hormone (ACTH): Regulates cortisol production.
• Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH): Regulate reproductive processes.
• Prolactin: Stimulates lactation.
• Thyroid-Stimulating Hormone (TSH): Stimulates thyroid hormone production.
• Oxytocin: Contractions during labor and milk ejection.
• Antidiuretic Hormone (ADH): Regulates water balance.

Thyroid Gland

• The thyroid gland is a butterfly-shaped endocrine gland located in the lower part of the neck, anterior to the trachea.
• It is responsible for the production and secretion of thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3).
• Thyroid hormones regulate metabolism, growth, and development.

Thyroid Hormone Synthesis

• Thyroid hormone synthesis requires iodine.
• The thyroid gland stores iodine and thyroglobulin, which are essential components for thyroid hormone production.

Thyroid Hormone Regulation

• The anterior pituitary gland secretes thyroid-stimulating hormone (TSH), which stimulates the thyroid gland to produce and release thyroid hormones.
• The thyroid gland also produces calcitonin, a hormone involved in calcium homeostasis.

Blood Supply

• The thyroid gland is supplied by the superior and inferior thyroid arteries.
• These arteries branch from the subclavian arteries.

Thyroid Gland Structure and Function

• The thyroid gland stores thyroglobulin and iodine for the production of thyroid hormones.
• The thyroid gland moves upwards when a person swallows.
• The thyroid gland is drained by the superior and middle thyroid veins.
• The thyroid gland is supplied by the superior and inferior thyroid arteries.
• The thyroid gland is butterfly-shaped.
• The thyroid gland produces calcitonin which regulates calcium homeostasis.
• The thyroid gland's blood supply drains through the brachiocephalic vein.
• Iodine is essential for the production of thyroid hormones (T3 and T4).
• The thyroid gland is located anterior to the trachea on the lower aspect of the neck.

Thyroid Hormone Regulation

• Stimuli for Thyroid Hormone Release:
  • Disease
  • Cold exposure
  • Pregnancy (estrogen)
  • Low levels of T3 and T4
  • Adrenaline
• Hypothalamus Role:
  • Releases thyrotropin-releasing hormone (TRH)
  • TRH release is triggered by stimuli such as cold exposure, stress, and low thyroid hormone levels.
• Anterior Pituitary Response:
  • Secretes thyroid-stimulating hormone (TSH) in response to TRH from the hypothalamus.
• Thyroid Gland Response:
  • Releases thyroid hormones (T3 and T4) in response to TSH.
• Iodine's Role:
  • Thyroid gland uses iodine to produce T3 and T4.
• T3 and T4 Action:
  • Travel to target tissues, where T4 is converted to T3.
• Negative Feedback Mechanism:
  • High levels of T3 and T4 inhibit the release of TRH from the hypothalamus and TSH from the anterior pituitary. This prevents overproduction of thyroid hormones.

Thyroid Hormone Actions

• Thyroid hormones increase the basal metabolic rate (BMR), leading to an increase in body temperature. This is referred to as the calorigenic effect.
• Thyroid hormones promote the use of glucose and fatty acids for energy production.
• Thyroid hormones stimulate lipolysis, the breakdown of fats into fatty acids.
• Thyroid hormones play a crucial role in the development and growth of nervous tissue and bones.

Hypothyroidism

• Symptoms:

  • Fatigue
  • Intolerance to cold
  • Weight gain
  • Constipation
  • Dry skin
  • Receding hairline and hair loss
  • Slow speech
  • Depression

• Hormone levels:

  • Low T3 & T4: The thyroid gland is not producing enough thyroid hormones (T3 and T4).
  • High TSH: The pituitary gland produces more TSH in an attempt to stimulate the thyroid gland.

• Common symptom: Receding hairlines and hair loss

Hyperthyroidism

• Symptoms:

  • Weight loss
  • Heat intolerance
  • Increased appetite
  • Diarrhea
  • Tremors
  • Tachycardia (fast heart rate)
  • Bulging Eyes (Exophthalmos)
  • Nervousness and anxiety

• Hormone levels:

  • High T3 & T4: The thyroid gland is overproducing thyroid hormones (T3 and T4).
  • Low TSH: The pituitary gland produces less TSH due to the negative feedback mechanism from high T3 and T4.

• Common symptoms:

  • Bulging eyes (Exophthalmos)
  • Tachycardia (fast heart rate)
  • Diarrhea

Parathyroid Gland Location

• The parathyroid glands are situated on the posterior surface of each thyroid gland lobe.

Parathyroid Gland Size

• The average diameter of a parathyroid gland is 5 mm.

Parathyroid Gland Cells

• The parathyroid glands are composed of chief cells, oxyphil cells, and adipocytes.

Parathyroid Gland Function

• The primary function of the parathyroid glands is to maintain calcium and phosphate homeostasis in the body.

Parathyroid Gland Regulation

• The activity of the parathyroid glands is regulated through a negative feedback mechanism based on calcium blood levels.

Parathyroid Gland Blood Supply

• The inferior thyroid arteries supply blood to the parathyroid glands.

Calcium Homeostasis

• Parathyroid Hormone (PTH) is secreted by the parathyroid glands in response to low blood calcium levels.
• PTH acts on bones to stimulate osteoclasts, breaking down bone tissue and releasing calcium into the bloodstream.
• PTH also acts on the kidneys to promote calcium reabsorption and reduce calcium excretion in urine.
• PTH stimulates the activation of inactive vitamin D in the kidneys.
• Active vitamin D enhances calcium absorption from the intestines.
• Increasing blood calcium levels triggers a negative feedback mechanism, inhibiting further release of PTH, preventing excessive calcium levels.
• Calcium homeostasis is maintained by the interplay of PTH, vitamin D, and bone activity, ensuring a delicate balance of calcium in the body.

Adrenal Glands: Location and Structure

• Adrenal glands sit atop each kidney
• Right adrenal gland is pyramid shaped
• Left adrenal gland is semi-lunar shaped
• Adrenal glands are divided into two distinct regions: the cortex and medulla

Adrenal Functions and Regulation

• Adrenal glands release steroid and catecholamine hormones directly into the blood
• Adrenal cortex is regulated by the pituitary gland, specifically by ACTH (adrenocorticotropic hormone)
• Adrenal medulla is regulated by the sympathetic nervous system

Adrenal Gland Hormones

• The adrenal cortex secretes cortisol in response to stress.
• Mineralocorticoids, secreted by the adrenal cortex, primarily regulate blood volume.
• The adrenal cortex also secretes androgens as sex hormones.
• Catecholamines (adrenaline and noradrenaline) are secreted by the adrenal medulla and primarily prepare the body for fight or flight responses.
• Glucocorticoids like cortisol increase blood glucose levels, regulate blood pressure, and respond to stress.
• The adrenal capsule separates the adrenal cortex and medulla.

Blood Supply to the Adrenal Glands

• The adrenal glands are supplied by three main arteries: the superior adrenal artery, the middle adrenal artery, and the inferior adrenal artery.
• The superior adrenal artery originates from the inferior phrenic artery.
• The middle adrenal artery originates from the abdominal aorta.
• The inferior adrenal artery originates from the inferior renal artery.
• The right adrenal vein drains into the inferior vena cava.
• The left adrenal vein drains into the left renal vein.
• The adrenal veins drain deoxygenated blood from the adrenal glands.

Aldosterone and its role in regulating blood pressure and electrolyte balance

• Aldosterone is a hormone primarily responsible for regulating blood pressure through the balance of potassium and sodium ions.
• It acts within the renin-angiotensin-aldosterone pathway.
• Aldosterone's main function in electrolyte is regulating sodium and potassium homeostasis, which affects blood pressure.
• Aldosterone increases sodium reabsorption in the kidneys, which increases blood volume and raises blood pressure.
• Aldosterone decreases potassium reabsorption in the kidneys, which reduces potassium levels in the blood and helps maintain electrolyte balance.
• Aldosterone is the principal mineralocorticoid, a type of steroid hormone, that regulates blood pressure by influencing sodium and potassium levels.

Renin-Angiotensin-Aldosterone System (RAAS)

• Activation: The RAAS is triggered by low blood pressure, dehydration, hemorrhage, or sodium deficiency.
• Renin: Secreted from juxtaglomerular cells in the kidneys in response to low blood pressure.
• Angiotensinogen Conversion: Renin converts angiotensinogen (produced by the liver) into angiotensin I.
• Angiotensin I Conversion: Angiotensin I is converted to angiotensin II in the lungs by angiotensin-converting enzyme (ACE).
• Angiotensin II Action: Angiotensin II acts as a vasoconstrictor, raising blood pressure by constricting blood vessels.
• Aldosterone Release: Angiotensin II stimulates the adrenal cortex to secrete aldosterone.
• Aldosterone Action: Aldosterone increases sodium reabsorption in the kidneys, causing water reabsorption.
• Outcome of Aldosterone: This leads to increased blood volume and raised blood pressure.
• Clinical Relevance: RAAS plays a crucial role in regulating blood volume and pressure and is a target for managing hypertension and heart failure.
• ACE Inhibitors: Medications like ACE inhibitors block the conversion of angiotensin I to Angiotensin II, lowering blood pressure.
• ARBs: Angiotensin II Receptor Blockers (ARBs) prevent angiotensin II from binding to its receptors, reducing its vasoconstrictive effects.

The Renin-Angiotensin-Aldosterone System (RAAS)

• RAAS is a complex hormonal system that regulates blood pressure and fluid balance.
• RAAS activation is triggered by a decrease in blood pressure or volume.
• Renin, an enzyme released from the kidneys, initiates the cascade.
• Renin converts angiotensinogen, a precursor protein produced in the liver, into angiotensin I.
• Angiotensin I is further converted to angiotensin II in the lungs by angiotensin-converting enzyme (ACE).
• Angiotensin II is a potent vasoconstrictor causing blood pressure to increase and helps maintain sodium and water balance by affecting the kidneys.
• Angiotensin II also stimulates the adrenal glands to release aldosterone.
• Aldosterone, a hormone produced by the adrenal glands, acts on the kidneys to promote sodium reabsorption and water retention, further increasing blood pressure.
• By increasing sodium and water reabsorption, RAAS elevates blood volume and pressure, helping to stabilize blood pressure and maintain fluid balance.
• ACE inhibitors and angiotensin II Receptor Blockers (ARBs) are drugs used to block the RAAS pathway, preventing angiotensin II from binding to its receptors, thus lowering blood pressure.
• ACE inhibitors prevent the conversion of angiotensin I to angiotensin II.
• ARBs block the action of angiotensin II, preventing its vasoconstricting effect and promoting vasodilation (widening of blood vessels), thus lowering blood pressure.
• The use of ACE inhibitors and ARBs are effective treatment options for hypertension.

Renin-Angiotensin-Aldosterone System (RAAS) Pathway Activation

• Triggered by a decrease in blood pressure.

Renin

• Released by the kidneys in response to low blood pressure.
• Converts angiotensinogen (produced in the liver) into angiotensin I.

Angiotensin I

• Converted into angiotensin II by the enzyme angiotensin-converting enzyme (ACE) primarily located in the lungs.

Angiotensin II

• Powerful vasoconstrictor, increasing blood pressure by narrowing blood vessels.
• Stimulates the release of aldosterone from the adrenal glands.
• Promotes sodium and water retention by the kidneys, further increasing blood volume and pressure.

Aldosterone

• Hormone produced by the adrenal glands.
• Increases sodium and water reabsorption in the kidneys, elevating blood pressure.

RAAS Pathway Function

• Regulates blood pressure by increasing blood volume and constricting blood vessels.

Medications Targeting RAAS Pathway

• ACE inhibitors block the conversion of angiotensin I to angiotensin II.
• Angiotensin II receptor blockers (ARBs) prevent angiotensin II from binding to its receptors, blocking its effects.
• Both are used to treat hypertension.

RAAS Pathway Final Outcome

• Increased blood volume and higher blood pressure.

Glucocorticoids

• Cortisol is the most abundant glucocorticoid hormone.
• Glucocorticoids are released in response to stress.
• Cortisol affects protein metabolism.
  • It increases protein breakdown to free amino acids for new protein synthesis.
• Cortisol affects glucose metabolism.
  • It stimulates the liver to convert amino acids or lactic acid into glucose.
  • This increases blood glucose levels.
• Cortisol is important for stress response.
  • It increases glucose formation from amino acids or lactic acid during stress.

Cortisol and its Effects

• Lipolysis: Cortisol stimulates the breakdown of triglycerides in adipose tissue, releasing fatty acids into the bloodstream. This process provides energy for the body during stress.

• Stress Resistance: Cortisol increases the availability of energy substrates (like fatty acids and glucose) to prepare the body for a "fight-or-flight" response. This enables the body to cope with stressful situations.

• Anti-inflammatory Action: Cortisol inhibits the inflammatory response by suppressing immune function, reducing inflammation. This action is crucial for controlling excessive inflammation and preventing tissue damage.

• Clinical Applications: Cortisol's anti-inflammatory effects are often used in treating inflammatory conditions, like autoimmune diseases, allergies, and inflammatory bowel diseases.

Catecholamines and the Fight or Flight Response

• Epinephrine (adrenaline) is the primary catecholamine released during the fight or flight response.
• Epinephrine accounts for approximately 80% of the total catecholamines released during this response.
• Catecholamines increase heart rate to deliver more oxygen to muscles.
• Catecholamines redirect blood flow to vital organs like the heart, liver, and muscles.
• Catecholamines dilate the airways to enhance oxygen intake.
• Catecholamines increase energy production to provide fuel for the body's response to a perceived threat.

Addison's Disease Symptoms

• Bronze pigmentation of skin: Caused by increased levels of melanocyte-stimulating hormone (MSH) due to high ACTH

• Hypoglycemia (low blood sugar): Caused by decreased cortisol production

• Postural hypotension (low blood pressure when standing up): Caused by decreased aldosterone & cortisol levels

• Gastrointestinal symptoms: Includes nausea, vomiting, and abdominal pain.

• Weight loss: Due to decreased appetite and hormonal deficiencies.

• Muscle weakness and fatigue: Caused by low cortisol levels.

• Dehydration: Caused by low aldosterone levels leading to an imbalance in water and sodium.

Adrenal Crisis Symptoms

• Extreme fatigue: A common and critical symptom.

• Electrolyte imbalances: Low sodium and high potassium due to insufficient aldosterone.

Risks & Complications

• Adrenal crisis: Can occur if Addison’s disease is left untreated or if a person with Addison's disease faces sudden stress.

Pancreas Functions

• The pancreas is a vital organ with both endocrine and exocrine functions.
• Endocrine function involves the production and release of hormones directly into the bloodstream via the Islets of Langerhans.

Islets of Langerhans

• These are clusters of endocrine cells responsible for hormone secretion.
• Insulin and glucagon, key regulators of blood glucose levels, are produced by the Islets of Langerhans.

Exocrine Function

• The pancreas also has an exocrine function, contributing to digestion.
• Digestive enzymes are produced by the exocrine acini cells and secreted via ducts into the small intestine.
• These enzymes break down food molecules, aiding digestion.

Tail of the Pancreas

• The tail of the pancreas contains both endocrine and exocrine tissues, emphasizing the organ's multifaceted role.

Location of the Pancreas

• The pancreas is located posterior and inferior to the stomach.

Function of the Pancreas

• The pancreas has both endocrine and exocrine functions.

Structure of the Pancreas

• The pancreas contains the islets of Langerhans, which are clusters of cells that produce hormones.
• The islets of Langerhans contain four types of cells: alpha, beta, delta, and PP cells.

Blood Supply of the Pancreas

• The body and tail of the pancreas are supplied by branches of the splenic artery.
• The head and uncinate process of the pancreas are supplied by the pancreaticoduodenal artery.

Pancreatic Hormone-Secreting Cells

• Alpha (α) cells secrete glucagon.
  • Glucagon raises blood glucose (BG) levels.
• Beta (β) cells secrete insulin.
  • Insulin lowers blood glucose (BG) levels.
  • Beta cells make up 70% of the cells within the pancreatic islet.
• Delta (δ) cells secrete somatostatin.
  • Somatostatin inhibits the release of both glucagon and insulin.
• F or pp cells secrete pancreatic polypeptide.
  • Pancreatic polypeptide inhibits somatostatin and digestive enzyme secretion.

Glucose Homeostasis

• Insulin is released by the pancreas in response to high blood glucose levels after meals.
• Insulin promotes glucose uptake by cells and stimulates glycogen formation in the liver, lowering blood sugar levels.
• Glucagon, secreted by the pancreas when blood glucose is low (during fasting or between meals), stimulates the liver to break down glycogen into glucose, increasing blood sugar levels.
• The liver plays a crucial role in glucose homeostasis by storing glucose as glycogen and converting it back to glucose as needed.
• Diabetes mellitus is a condition caused by imbalances in glucose homeostasis regulation, leading to either high blood sugar levels (hyperglycemia) or low blood sugar levels (hypoglycemia).