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Pancreatic Hormones and Clinical Manifestations Quiz

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123 Questions

During which stage of the general adaptation syndrome does the body exhibit an increased resistance to stressors?

Stage of resistance

Which hormone interaction is exemplified by one hormone enhancing the response to a second hormone?

Permissive effects

What type of effects can result from the simultaneous action of epinephrine and norepinephrine?

Synergistic effects

In the context of hormone interactions, which term describes the relationship between parathyroid hormone (PTH) and calcitonin?

Antagonistic effects

What is the long-term effect of sustained high levels of insulin on target cells?

Down-regulation

Eicosanoids are signaling molecules that act in a _________ manner to influence neighboring cells.

Paracrine

Which type of hormones penetrate the plasma membrane and bind to intracellular receptors?

Hydrophobic hormones

What is the mode of action for hydrophilic hormones that use cAMP as a second messenger?

Phosphorylate Myosin

Which hormone effect involves increasing the rate of aerobic respiration and protein synthesis?

Thyroid Hormone

What is the role of Na+-K+ ATPase in response to thyroid hormone?

Increases heat generation

Which type of hormones need to bind to cell-surface receptors?

Hydrophilic hormones

Which protein is activated by Gq protein in the G-coupled protein examples given?

Calmodulin

Which hormone is secreted when blood glucose is low and acts on liver cells to release glycogen, increasing blood sugar levels?

Glucagon

What is the primary function of insulin secreted by beta cells in the pancreas after a meal?

Stimulates glucose uptake

Which hormone is responsible for inhibiting growth hormone (GH) secretion after a meal?

Somatostatin

What is the primary function of hyperglycemic hormones in the body?

Raise blood glucose levels

Which organ releases atrial natriuretic peptide to help decrease blood volume and blood pressure?

Heart

What is the primary function of erythropoietin produced by the kidneys?

Produce red blood cells

Which hormones are categorized as fat-soluble steroids derived from cholesterol?

Sex steroids and Corticosteroids

Which hormones are derived from amino acids and catecholamines?

Norepinephrine, dopamine, epinephrine

Which class of hormones includes eicosanoids derived from polyunsaturated fatty acids?

Eicosanoids

What type of hormones act as chemical messengers that travel in the bloodstream?

Endocrine hormones

In cell communication, which mechanism involves signaling chemicals moving from cell to cell through pores in the cell membrane?

Gap junctions allowing direct cell-to-cell signaling

Which type of glands secrete their products through a duct onto an open surface or organ cavity?

Exocrine glands

What is the primary function of eicosanoids in cell signaling?

Act intracellularly to alter target cell metabolism

Which component of the endocrine system is responsible for producing hormones such as thyroid hormones and melatonin?

Pineal gland

What distinguishes endocrine glands from exocrine glands in terms of their secretions?

Endocrine glands have ducts to release products onto surfaces.

What is the precursor molecule that is converted to proinsulin in the endoplasmic reticulum?

Preproinsulin

Which hormone is synthesized from tryptophan instead of tyrosine?

Melatonin

In the synthesis of thyroid hormone, what mineral is required?

Iodine

Which cells absorb iodine from the blood and synthesize thyroglobulin to form T3 and T4?

Follicular cells

What is the composition of T3 (triiodothyronine)?

Combination of DIT and MIT

How are hydrophilic protein hormones typically transported in the bloodstream?

As free, unbound molecules

What is the primary mode of action for hydrophobic hormones such as estrogen, T3, and aldosterone?

Bind to cytoplasmic receptors and activate metabolic pathways

Which organelle is directly affected by thyroid hormone (TH) binding to its receptors?

Mitochondria

What is the primary function of cAMP in the mode of action of hydrophilic hormones like epinephrine?

Produce metabolic reactions

In the G-coupled protein examples given, which protein is responsible for increasing intracellular calcium levels in smooth muscle cells?

Inositol trisphosphate (IP3)

What is the main effect of alpha-2 G-coupled protein on adenylyl cyclase (AC) activity?

Inhibits AC to decrease cAMP levels

Which mitochondria-associated process is directly influenced by thyroid hormone binding to its receptors?

ATP synthesis

Which hormone promotes tissue growth by enhancing amino acid transport into cells and increasing protein synthesis?

Somatotropin

Where does somatotropin stimulate the liver to produce IGF-I and II, leading to protein synthesis?

Liver

Which hormone, secreted by the posterior pituitary gland, targets the kidneys to reduce urine and retain water?

ADH

What is the primary function of melatonin produced by the pineal gland at night?

Regulate sleep patterns

Which gland becomes less active after puberty and secretes hormones that regulate T-lymphocyte development?

Thymus gland

Which hormone released by the thyroid gland promotes calcium deposition and antagonizes parathyroid hormone?

Calcitonin

What is the primary function of aldosterone produced by the adrenal cortex?

Controls electrolyte balance

Which stage of the general adaptation syndrome is characterized by protein breakdown, muscle wasting, and loss of glucose homeostasis?

Stage of Exhaustion

In which disorder does a tumor or lesion destroy a gland leading to inadequate hormone release?

Hyposecretion disorder

Which chemical messenger diffuses from the adrenal medulla to the cortex?

Catecholamines

What is the primary function of Prostacyclin produced by cyclooxygenase?

Inhibits blood clotting and vasoconstriction

Which disorder results in low metabolic rate, weight gain, bradycardia, and constipation?

Thyroid Gland Disorders

What characterizes congenital hypothyroidism in infants?

Low temperature and lethargy

How do hydrophobic hormones like estrogen and T3 typically enter a cell to bind to their receptors?

Directly penetrate the plasma membrane

What is the composition of T4 (thyroxine)?

Two DIT molecules

Which organelle is primarily targeted by thyroid hormone (TH) to increase the rate of aerobic respiration and protein synthesis?

Mitochondria

Which hormone requires the mineral iodine for its synthesis?

Thyroid hormone

What is the primary mode of action for hydrophilic hormones such as epinephrine that utilize cAMP as a second messenger?

Activate adenylate cyclase to produce cAMP

What is the primary storage form of thyroid hormone in the follicular cells?

Thyroglobulin

Which hormones are classified as hydrophobic and require transport proteins for circulation?

Steroids

Which second messenger is typically activated in hydrophilic hormone modes of action, promoting metabolic reactions such as synthesis and secretion?

cAMP

When hydrophilic hormones like epinephrine bind to cellsurface receptors, what is the immediate downstream effect in the mode of action?

Activation of adenylate cyclase

What is the primary function of C-peptide in insulin formation?

Acts as a storage form of insulin

In the context of hydrophilic hormone action, which molecule serves as a common intermediate for activating kinases and enzymes?

cAMP

Which organelle plays a key role in the conversion of proinsulin to insulin?

Golgi complex

Which clinical manifestation is associated with excess cortisol secretion in Cushing syndrome?

Increased appetite and weight gain

What is a common symptom of hyperparathyroidism due to excess parathyroid hormone (PTH) secretion?

Weak, fragile, and deformed bones

What characterizes the role of insulin in diabetes mellitus type II?

Enhances target cell sensitivity to insulin

In what disorder is hypoglycemia a common symptom due to excess insulin secretion?

Hyperinsulinism

What is the main effect of adrenal androgen hypersecretion in adrenogenital syndrome?

Feminizing effects in women

Which hormone imbalance results from inadequate secretion of parathyroid hormone (PTH)?

Hypoparathyroidism

What is the primary role of gap junctions in cell communication?

Allow signaling chemicals to move from cell to cell

In endocrine glands, how are the secretions delivered compared to exocrine glands?

Directly into the bloodstream without ducts

What characterizes the action of paracrine hormones?

Released into interstitial fluid to affect nearby cells

What distinguishes target cells from other cell types in the body?

Absorb and respond to specific hormones

How do eicosanoids primarily influence neighboring cells?

By binding to intracellular receptors

Which mechanism is involved in cell communication when neurotransmitters are released from neurons?

Traveling across synapses to reach adjacent cells

Which organ releases atrial natriuretic peptide to help decrease blood volume and blood pressure?

Heart

Which hormone is responsible for stimulating glycogenolysis, fat catabolism, and promoting the absorption of amino acids for gluconeogenesis?

Glucagon

What is the primary function of hepcidin in the bloodstream?

Inhibits iron absorption

Which type of hormones are derived from cholesterol and have functional groups attached to a 4-ringed steroid backbone?

Steroids

What is the primary function of pancreatic polypeptide secreted by F cells in the pancreas?

Inhibits GH secretion

Which hormone, when secreted, raises blood glucose levels by acting on liver cells to release glycogen?

Glucagon

What does somatostatin secreted by delta (d) cells do when there is a rise in blood glucose and amino acids after a meal?

Inhibits insulin and glucagon secretion

Which organ produces 15% of erythropoietin, stimulating bone marrow to produce red blood cells?

Liver

What is the precursor molecule that converts into proinsulin in the golgi complex?

Preproinsulin

Which hormone is synthesized from tryptophan instead of tyrosine?

Melatonin

What mineral is required for the synthesis of thyroid hormone?

Iodine

Which molecules form T3 and T4 in the synthesis of thyroid hormone?

MIT and DIT

Which type of hormones are transported in the bloodstream bound to transport proteins?

Steroids and thyroid hormones

What is the composition of Thyroxine (T4) in terms of MIT and DIT molecules?

DIT and MIT

What is the primary role of somatotropin secreted by the anterior pituitary gland?

Stimulates liver to produce IGF-I and II for protein synthesis

During childhood and adolescence, what specific growth process does growth hormone stimulate?

Bone, cartilage, and muscle growth

In adulthood, how does growth hormone primarily affect bone structure?

Enhances bone thickening and remodeling

What is the primary function of oxytocin released by the posterior pituitary gland?

Promotes uterine contractions and milk ejection

Which hormone is predominantly secreted by the pineal gland and plays a role in regulating sleep-wake cycles?

Melatonin

Where is the thymus located in the body?

Superior to the heart

Which layer of the adrenal cortex produces glucocorticoids like cortisol that affect metabolism?

Zona fasciculata (middle)

What is the primary effect of catecholamines released by the adrenal medulla on metabolic rate?

(Increase in metabolic rate)

"Pheochromocytomas" are tumors derived from which cells in the adrenal medulla?

"Chromaffin cells"

"Calcitonin" produced by parafollicular "C" cells primarily affects which of the following?

(Antagonizes parathyroid hormone to decrease blood calcium)

What is the primary role of histamine from mast cells in connective tissue?

Causing relaxation of blood vessel smooth muscle

Which chemical messenger from the adrenal medulla diffuses to the cortex?

Catecholamines

What is the main function of Prostacyclin produced by cyclooxygenase?

Inhibits blood clotting and vasoconstriction

Which disorder results in abnormal bone development, lethargy, and brain damage in infants?

Cretinism

What happens in acromegaly due to hypersecretion of growth hormones?

Thickening of bones and soft tissues

What is the primary function of Thromboxanes produced by cyclooxygenase?

Stimulate vasoconstriction and clotting

What is the long-term effect of sustained high levels of cortisol on the immune system?

Depressed immune function

What characterizes the role of ACTH during the Stage of Resistance in stress response?

Stimulates fat and protein breakdown

How do Leukotrienes influence allergic and inflammatory reactions?

Induce allergic and inflammatory reactions

What is the primary effect of aldosterone during the Alarm Reaction stage?

Retention of sodium and water

What distinguishes the speed of the response between the nervous and endocrine systems?

Nervous system reacts quickly, while the endocrine system reacts slowly.

How do the nervous and endocrine systems differ in their area of effect?

Nervous system has targeted and specific effects, while the endocrine system has general, widespread effects.

What controls homeostasis mechanisms and some endocrine functions?

Hypothalamus

Which chemical functions as both a hormone and a neurotransmitter?

Dopamine

What is the primary function of ACTH (Adrenocorticotropic Hormone)?

Regulates response to stress and stimulates adrenal cortex

Which hormone stimulates production of egg or sperm cells?

FSH (Follicle Stimulating Hormone)

Which hormone mainly stimulates hormone production in females?

LH (Luteinizing Hormone)

Where are hormone receptors located for hydrophobic hormones like estrogen, T3, and aldosterone?

In the nucleus

Which hormone mode of action involves binding to cell-surface receptors?

Thyroid hormone

What is the primary effect of thyroid hormone (TH) binding to receptors on ribosomes and chromatin?

Enhances protein synthesis

Which second messenger is activated by hydrophilic hormones like epinephrine?

cAMP

What is the downstream effect of activation by alpha 1 G-coupled protein on proteins/enzymes?

Phosphorylation of proteins/enzymes

Which organelle is targeted by alpha 2 G-coupled protein to inhibit adenylate cyclase activity?

Plasma membrane

Study Notes

Hormone Receptors and Action

  • Hormone receptors are located on the plasma membrane, mitochondria, other organelles, or in the nucleus
  • There are thousands of receptors for a given hormone, which binding turns metabolic pathways on or off
  • Hydrophobic hormones (e.g. Estrogen, T3, Aldosterone) penetrate the plasma membrane and bind to intracellular receptors
  • Hydrophilic hormones (e.g. Epinephrine) must bind to cell surface receptors

Thyroid Hormone Effects

  • Thyroid hormone (TH) binds to receptors on:
    • Mitochondria: increases rate of aerobic respiration
    • Ribosomes and chromatin: stimulates protein synthesis
    • Na+-K+ ATPase: generates heat

Hydrophilic Hormones: Mode of Action

  • cAMP as a second messenger:
    1. Hormone binding activates G(s) protein
    2. Activates adenylate cyclase
    3. Produces cAMP
    4. Activates kinases
    5. Activates enzymes
    6. Metabolic reactions: synthesis, secretion, and change in membrane potentials
  • Other second messengers:
    • G-coupled proteins: may use different second messengers in different tissues
    • Examples: alpha 1, alpha 2, IP3, DAG, PKC, calmodulin, MLCK, and myosin

Endocrine System Overview

  • Hormones: chemical messengers secreted into the bloodstream, stimulating a response in another tissue or organ
  • Target cells: have receptors for the hormone
  • Endocrine glands: produce hormones
  • Endocrine system: includes endocrine organs (e.g. thyroid, pineal), hormone-producing cells in organs (e.g. brain, heart, small intestine)

Endocrine vs. Exocrine Glands

  • Endocrine glands: secrete products directly into the bloodstream, no ducts
  • Exocrine glands: secrete products through a duct and onto an open surface or organ cavity

Pancreas

  • Both an exocrine and endocrine gland
  • Endocrine tissue: clusters of endocrine cells called "Islets of Langerhans"
  • Four types of cells that secrete different hormones:
    • Alpha (α) cells: glucagon
    • Beta (β) cells: insulin
    • Delta (δ) cells: somatostatin
    • F cells: pancreatic polypeptide

Pancreatic Hormones

  • Insulin:
    • Secreted after a meal with carbohydrates that raise glucose blood levels
    • Stimulates glucose and amino acid uptake
    • Promotes nutrient storage effect (promotes glycogenesis and lipogenesis)
    • Antagonizes glucagon
  • Glucagon:
    • Secreted when blood glucose is low
    • Acts on liver cells to release glycogen
    • Increases blood sugar
    • Stimulates glycogenolysis, fat catabolism, and promotes absorption of amino acids for gluconeogenesis
  • Somatostatin:
    • Secreted with a rise in blood glucose and amino acids after a meal
    • Inhibits GH secretion
    • Paracrine secretion: inhibits secretion of insulin and glucagon by α and β cells

Endocrine Functions of Other Organs

  • Heart: atrial natriuretic peptide released with an increase in blood pressure
  • Skin: helps produce vitamin D3
  • Liver:
    • 15% of erythropoietin (stimulates bone marrow)
    • Angiotensinogen (a prohormone) precursor of angiotensin II
    • Source of IGF-I (works with GH)
    • Converts vitamin D3 to calcidiol
    • Hepcidin: inhibits intestinal absorption of iron into the bloodstream
  • Kidneys:
    • Produces 85% of erythropoietin
    • Renin converts angiotensinogen to angiotensin I
    • Converts calcidiol to calcitriol (active form of vitamin D)
  • Stomach and small intestines: 10 enteric hormones coordinate digestive motility and secretion
  • Placenta: secretes estrogen, progesterone, and others regulate pregnancy, stimulate development of the fetus and mammary glands

Hormone Synthesis

  • Steroid hormones: synthesized from cholesterol
  • Peptides and glycoproteins: synthesized in the RER, further modified in the Golgi complex
  • Monoamines: synthesized from tyrosine (except melatonin, which is synthesized from tryptophan)

Hormone Transport

  • Hydrophilic hormones: transported in the bloodstream, unbound, and water-soluble
  • Steroid hormones: must bind to transport proteins for transport, prolonging half-life
  • Transport proteins in blood plasma: albumin, thyroxine-binding globulin (TGB), and transcortin

Adrenal Gland

  • Cortex: three zones, each producing different hormones
    • Zona glomerulosa: mineralocorticoids (e.g. aldosterone)
    • Zona fasciculata: glucocorticoids (e.g. cortisol)
    • Zona reticularis: sex hormones (e.g. androgens and estrogens)
  • Medulla: chromaffin cells producing catecholamines (e.g. epinephrine and norepinephrine)

Stress and Adaptation

  • General adaptation syndrome: the body's response to stress
  • Three stages:
    1. Alarm reaction
    2. Stage of resistance
    3. Stage of exhaustion

Paracrine Secretions

  • Chemical messengers that diffuse short distances and stimulate nearby cells
  • Examples:
    • Histamine from mast cells in connective tissue
    • Nitric oxide from endothelium of blood vessels
    • Somatostatin from delta cells
    • Catecholamines from adrenal medulla

Eicosanoids

  • Paracrine secretions derived from arachidonic acid
  • Examples:
    • Leukotrienes: mediate allergic and inflammatory reactions
    • Prostacyclin: inhibits blood clotting and vasoconstriction
    • Thromboxanes: stimulate vasoconstriction and clotting
    • Prostaglandins: diverse effects, including relaxation of smooth muscle and stimulation of relaxation of blood vessels

Endocrine Disorders

  • Too much or too little hormone

  • Variations in hormone concentration and target cell sensitivity

  • Examples:

    • Hyposecretion: inadequate hormone release
    • Hypersecretion: excessive hormone release
    • Pituitary disorders: hypersecretion of growth hormones
    • Thyroid gland disorders: congenital hypothyroidism, endemic goiter, toxic goiter, and hypothyroidism### Hormone Synthesis and Transport
  • Insulin formation: preproinsulin is converted to proinsulin in the RER, and then split into insulin and C peptide in the Golgi complex.

  • Monoamine synthesis: all are synthesized from tyrosine, except melatonin, which is synthesized from tryptophan.

  • Thyroid hormone synthesis: composed of two tyrosine molecules, requires a mineral, iodine.

  • T3 and T4 synthesis: follicular cells absorb I- from blood, store in lumen as I-, synthesize thyroglobulin, and store in lumen containing tyrosine.

  • TSH stimulates follicular cells to remove T3 and T4 from thyroglobulin for release into plasma.

  • Hormone transport: monoamines and peptides are hydrophilic, transported in the bloodstream as a water-soluble form.

  • Steroids and thyroid hormone are hydrophobic, must bind to transport proteins for transport.

Endocrine System Overview

  • Hypothalamus and pituitary gland: other endocrine glands, hormones, and their actions.
  • Stress and adaptation: eicosanoids and paracrine signaling.
  • Endocrine disorders: too much or too little hormone.

Endocrine System Components

  • Hormone: a chemical messenger secreted into the bloodstream, stimulating a response in another tissue or organ.
  • Target cells: have receptors for the hormone.
  • Endocrine glands: produce hormones.
  • Endocrine system: endocrine organs, hormone-producing cells in organs.

Endocrine vs. Exocrine Glands

  • Exocrine glands: secrete their products through a duct and onto an open surface or organ cavity.
  • Endocrine glands: secrete their products directly into the bloodstream, no ducts.

Nervous vs. Endocrine System

  • Endocrine system: endocrine organs, hormone-producing cells in organs.
  • Nervous system: brain, spinal cord, and peripheral nerves.

Pancreas

  • Is both exocrine and endocrine.
  • Endocrine tissue: clusters of endocrine cells called "Islets of Langerhans".
  • Islets include 4 types of cells that secrete different hormones:
    • Alpha (a) cells: glucagon.
    • Beta (b) cells: insulin.
    • Delta (d) cells: somatostatin.
    • F cells: pancreatic polypeptide.

Pancreatic Hormones

  • Insulin: secreted after a meal, stimulates glucose and amino acid uptake, and nutrient storage.
  • Glucagon: secreted when blood glucose is low, acts on liver cells to release glycogen, and increases blood sugar.
  • Somatostatin: secreted with a rise in blood glucose and amino acids, inhibits GH, and paracrine secretion inhibits insulin and glucagon.

Endocrine Functions of Other Organs

  • Heart: atrial natriuretic peptide, released with an increase in BP.
  • Skin: helps produce D3.
  • Liver: 15% of erythropoietin, angiotensinogen, and IGF-I.
  • Kidneys: 85% of erythropoietin, renin, and calcidiol.
  • Stomach and small intestines: 10 enteric hormones, coordinate digestive motility and secretion.
  • Placenta: secretes estrogen, progesterone, and others, regulates pregnancy, and stimulates development of the fetus and mammary glands.

Hormone Classification

  • Fat-soluble: steroids, derived from cholesterol.
  • Water-soluble: peptides and glycoproteins, and monoamines.
  • Steroids: sex steroids, corticosteroids, and calcitriol.
  • Peptides and glycoproteins: OT, ADH, and most of the anterior pituitary hormones.
  • Monoamines: catecholamines, and thyroid hormones.

Oxytocin and ADH

  • Oxytocin: causes uterine contractions and milk ejection.
  • ADH: targets kidneys, increases water retention, and reduces urine.

Growth Hormone and Aging

  • Childhood and adolescence: bone, cartilage, and muscle growth.
  • Adulthood: increase osteoblastic activity, and appositional growth affecting bone thickening and remodeling.
  • Blood concentration: higher during deep sleep, after high protein meals, and after vigorous exercise.

Posterior Pituitary Hormones

  • ADH: targets kidneys, increases water retention, and reduces urine.
  • Oxytocin: causes uterine contractions and milk ejection.

Pineal Gland

  • Produces serotonin by day, and converts it to melatonin at night.
  • Melatonin: suppresses in SAD, and increases in PMS.

Thymus

  • Located in the mediastinum, superior to the heart.
  • Involution after puberty.
  • Secretes hormones that regulate development and later activation of T-lymphocytes.

Thyroid Gland

  • Anatomy: largest endocrine gland, high rate of blood flow.
  • Thyroid hormones: T3 and T4, produced by thyroid follicles, and stimulate the body's metabolic rate.

Parathyroid Glands

  • Produce parathyroid hormone, which increases blood Ca2+ levels.

Adrenal Gland

  • Adrenal cortex: produces corticosteroids, and adrenaline.
  • Adrenal medulla: produces catecholamines.

Adrenal Cortex

  • Zona glomerulosa: produces mineralocorticoids, and aldosterone.
  • Zona fasciculata: produces glucocorticoids, and cortisol.
  • Zona reticularis: produces sex hormones.

Adrenal Medulla

  • Produces catecholamines, and stimulates the sympathetic nervous system.
  • Increases alertness, anxiety, or fear.

Endocrine Disorders

  • Hyposecretion: inadequate hormone release, leading to various disorders such as diabetes insipidus, and thyrotoxicosis.
  • Hypersecretion: excessive hormone release, leading to various disorders such as acromegaly, and Cushing's syndrome.

Endocrine Disorders

  • Thyroid gland disorders: congenital hypothyroidism, myxedema, endemic goiter, toxic goiter, and hyperthyroidism.
  • Parathyroid disorders: hypoparathyroidism, and hyperparathyroidism.
  • Adrenal disorders: Cushing's syndrome, and adrenogenital syndrome.
  • Diabetes mellitus: signs and symptoms, types, and pathology.
  • Hyperinsulinism: causes, and symptoms.

Endocrine System Pathology

  • Acute pathology: cells cannot absorb glucose, rely on fat and proteins.
  • Chronic pathology: chronic hyperglycemia leads to neuropathy, and cardiovascular damage.### Communication in Nervous and Endocrine Systems
  • Nervous system uses both electrical and chemical signals, while endocrine system uses only chemical signals
  • Nervous system reacts quickly (1-10 msec) and stops quickly, while endocrine system reacts slowly (seconds or days) and effects may persist for weeks
  • Nervous system adapts quickly to long-term stimuli, while endocrine system response persists
  • Nervous system has targeted and specific effects on one organ, while endocrine system has general and widespread effects on many organs

Overlapping Functions

  • Some chemicals function as both hormones and neurotransmitters (NE, cholecystokinin, thyrotropin-releasing hormone, dopamine, and ADH)
  • Some hormones are secreted by neuroendocrine cells (neurons) like oxytocin and catecholamines
  • Both systems have overlapping effects on same target cells (NE and glucagon cause glycogenolysis in liver)
  • Systems can regulate each other (neurons can trigger hormone secretion, and hormones can stimulate or inhibit neurons)

Hypothalamus and Pituitary Gland

Hypothalamus

  • Regulates homeostasis mechanisms and some endocrine functions
  • Shaped like a flattened funnel and forms floor and walls of third ventricle

Pituitary Gland

  • Suspended from hypothalamus by stalk (infundibulum) and housed in sella turcica of sphenoid bone
  • Diameter of 1.3 cm
  • Anterior pituitary (adenohypophysis) arises from hypophyseal pouch (outgrowth of pharynx)
  • Posterior pituitary (neurohypophysis) arises from brain

Embryonic Development and Histology of Pituitary Gland

Pituitary Gland Anatomy and Hormones

  • Anterior pituitary hormones: FSH, LH, TSH, ACTH, PRL, and GH
  • Posterior pituitary hormones: oxytocin and ADH

Control of Pituitary

  • Anterior lobe control: releasing hormones and inhibiting hormones of hypothalamus
  • Posterior lobe control: neuroendocrine reflexes (hormone release in response to nervous system signals)

Feedback from Target Organs

  • Negative feedback: target organ hormone levels inhibit release of tropic hormones
  • Positive feedback: stretching of uterus triggers OT release, causing more contraction and stretching of uterus, until delivery

Pituitary Hormones - Anterior Lobe

  • Tropic hormones target other endocrine glands
  • FSH targets gonads
  • LH mainly stimulates hormone production in females and testosterone secretion in males
  • TSH stimulates growth of thyroid and secretion of thyroid hormones
  • ACTH regulates response to stress and stimulates adrenal cortex to secrete corticosteroids
  • PRL stimulates milk synthesis in females and LH sensitivity and testosterone secretion in males
  • GH (growth hormone) affects growth and metabolism

Hormone Receptors

  • Located on plasma membrane, mitochondria, other organelles, or in nucleus
  • Thousands of receptors for a given hormone, binding turns metabolic pathways on or off

Hormone Mode of Action

  • Hydrophobic hormones (estrogen, T3, aldosterone) penetrate plasma membrane and bind to intracellular receptors
  • Hydrophilic hormones (epinephrine) bind to cell surface receptors

Thyroid Hormone Effects

  • TH binds to receptors on mitochondria, increasing rate of aerobic respiration
  • TH binds to receptors on ribosomes and chromatin, increasing protein synthesis
  • TH stimulates production of Na+-K+ ATPase, generating heat

Hydrophilic Hormones: Mode of Action

  • Use cAMP as a second messenger (epinephrine)
  • Hormone binding activates G(s) protein, which activates adenylate cyclase, producing cAMP
  • cAMP activates kinases, which activate enzymes, leading to metabolic reactions

Hydrophilic Hormones: Mode of Action (Cont.)

  • Other second messengers: G-coupled proteins, alpha 1 and alpha 2
  • Alpha 1 uses Gq, PLC, PIP2, DAG, PKC, and IP3
  • Alpha 2 uses Gi, inhibiting adenylate cyclase, decreasing cAMP and PKA

Test your knowledge on pancreatic hormones and clinical manifestations related to catecholamines secretion. Learn about the functions of different types of cells in the endocrine tissue of the pancreas.

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