Podcast
Questions and Answers
During which stage of the general adaptation syndrome does the body exhibit an increased resistance to stressors?
During which stage of the general adaptation syndrome does the body exhibit an increased resistance to stressors?
Which hormone interaction is exemplified by one hormone enhancing the response to a second hormone?
Which hormone interaction is exemplified by one hormone enhancing the response to a second hormone?
What type of effects can result from the simultaneous action of epinephrine and norepinephrine?
What type of effects can result from the simultaneous action of epinephrine and norepinephrine?
In the context of hormone interactions, which term describes the relationship between parathyroid hormone (PTH) and calcitonin?
In the context of hormone interactions, which term describes the relationship between parathyroid hormone (PTH) and calcitonin?
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What is the long-term effect of sustained high levels of insulin on target cells?
What is the long-term effect of sustained high levels of insulin on target cells?
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Eicosanoids are signaling molecules that act in a _________ manner to influence neighboring cells.
Eicosanoids are signaling molecules that act in a _________ manner to influence neighboring cells.
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Which type of hormones penetrate the plasma membrane and bind to intracellular receptors?
Which type of hormones penetrate the plasma membrane and bind to intracellular receptors?
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What is the mode of action for hydrophilic hormones that use cAMP as a second messenger?
What is the mode of action for hydrophilic hormones that use cAMP as a second messenger?
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Which hormone effect involves increasing the rate of aerobic respiration and protein synthesis?
Which hormone effect involves increasing the rate of aerobic respiration and protein synthesis?
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What is the role of Na+-K+ ATPase in response to thyroid hormone?
What is the role of Na+-K+ ATPase in response to thyroid hormone?
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Which type of hormones need to bind to cell-surface receptors?
Which type of hormones need to bind to cell-surface receptors?
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Which protein is activated by Gq protein in the G-coupled protein examples given?
Which protein is activated by Gq protein in the G-coupled protein examples given?
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Which hormone is secreted when blood glucose is low and acts on liver cells to release glycogen, increasing blood sugar levels?
Which hormone is secreted when blood glucose is low and acts on liver cells to release glycogen, increasing blood sugar levels?
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What is the primary function of insulin secreted by beta cells in the pancreas after a meal?
What is the primary function of insulin secreted by beta cells in the pancreas after a meal?
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Which hormone is responsible for inhibiting growth hormone (GH) secretion after a meal?
Which hormone is responsible for inhibiting growth hormone (GH) secretion after a meal?
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What is the primary function of hyperglycemic hormones in the body?
What is the primary function of hyperglycemic hormones in the body?
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Which organ releases atrial natriuretic peptide to help decrease blood volume and blood pressure?
Which organ releases atrial natriuretic peptide to help decrease blood volume and blood pressure?
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What is the primary function of erythropoietin produced by the kidneys?
What is the primary function of erythropoietin produced by the kidneys?
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Which hormones are categorized as fat-soluble steroids derived from cholesterol?
Which hormones are categorized as fat-soluble steroids derived from cholesterol?
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Which hormones are derived from amino acids and catecholamines?
Which hormones are derived from amino acids and catecholamines?
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Which class of hormones includes eicosanoids derived from polyunsaturated fatty acids?
Which class of hormones includes eicosanoids derived from polyunsaturated fatty acids?
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What type of hormones act as chemical messengers that travel in the bloodstream?
What type of hormones act as chemical messengers that travel in the bloodstream?
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In cell communication, which mechanism involves signaling chemicals moving from cell to cell through pores in the cell membrane?
In cell communication, which mechanism involves signaling chemicals moving from cell to cell through pores in the cell membrane?
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Which type of glands secrete their products through a duct onto an open surface or organ cavity?
Which type of glands secrete their products through a duct onto an open surface or organ cavity?
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What is the primary function of eicosanoids in cell signaling?
What is the primary function of eicosanoids in cell signaling?
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Which component of the endocrine system is responsible for producing hormones such as thyroid hormones and melatonin?
Which component of the endocrine system is responsible for producing hormones such as thyroid hormones and melatonin?
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What distinguishes endocrine glands from exocrine glands in terms of their secretions?
What distinguishes endocrine glands from exocrine glands in terms of their secretions?
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What is the precursor molecule that is converted to proinsulin in the endoplasmic reticulum?
What is the precursor molecule that is converted to proinsulin in the endoplasmic reticulum?
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Which hormone is synthesized from tryptophan instead of tyrosine?
Which hormone is synthesized from tryptophan instead of tyrosine?
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In the synthesis of thyroid hormone, what mineral is required?
In the synthesis of thyroid hormone, what mineral is required?
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Which cells absorb iodine from the blood and synthesize thyroglobulin to form T3 and T4?
Which cells absorb iodine from the blood and synthesize thyroglobulin to form T3 and T4?
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What is the composition of T3 (triiodothyronine)?
What is the composition of T3 (triiodothyronine)?
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How are hydrophilic protein hormones typically transported in the bloodstream?
How are hydrophilic protein hormones typically transported in the bloodstream?
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What is the primary mode of action for hydrophobic hormones such as estrogen, T3, and aldosterone?
What is the primary mode of action for hydrophobic hormones such as estrogen, T3, and aldosterone?
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Which organelle is directly affected by thyroid hormone (TH) binding to its receptors?
Which organelle is directly affected by thyroid hormone (TH) binding to its receptors?
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What is the primary function of cAMP in the mode of action of hydrophilic hormones like epinephrine?
What is the primary function of cAMP in the mode of action of hydrophilic hormones like epinephrine?
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In the G-coupled protein examples given, which protein is responsible for increasing intracellular calcium levels in smooth muscle cells?
In the G-coupled protein examples given, which protein is responsible for increasing intracellular calcium levels in smooth muscle cells?
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What is the main effect of alpha-2 G-coupled protein on adenylyl cyclase (AC) activity?
What is the main effect of alpha-2 G-coupled protein on adenylyl cyclase (AC) activity?
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Which mitochondria-associated process is directly influenced by thyroid hormone binding to its receptors?
Which mitochondria-associated process is directly influenced by thyroid hormone binding to its receptors?
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Which hormone promotes tissue growth by enhancing amino acid transport into cells and increasing protein synthesis?
Which hormone promotes tissue growth by enhancing amino acid transport into cells and increasing protein synthesis?
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Where does somatotropin stimulate the liver to produce IGF-I and II, leading to protein synthesis?
Where does somatotropin stimulate the liver to produce IGF-I and II, leading to protein synthesis?
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Which hormone, secreted by the posterior pituitary gland, targets the kidneys to reduce urine and retain water?
Which hormone, secreted by the posterior pituitary gland, targets the kidneys to reduce urine and retain water?
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What is the primary function of melatonin produced by the pineal gland at night?
What is the primary function of melatonin produced by the pineal gland at night?
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Which gland becomes less active after puberty and secretes hormones that regulate T-lymphocyte development?
Which gland becomes less active after puberty and secretes hormones that regulate T-lymphocyte development?
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Which hormone released by the thyroid gland promotes calcium deposition and antagonizes parathyroid hormone?
Which hormone released by the thyroid gland promotes calcium deposition and antagonizes parathyroid hormone?
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What is the primary function of aldosterone produced by the adrenal cortex?
What is the primary function of aldosterone produced by the adrenal cortex?
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Which stage of the general adaptation syndrome is characterized by protein breakdown, muscle wasting, and loss of glucose homeostasis?
Which stage of the general adaptation syndrome is characterized by protein breakdown, muscle wasting, and loss of glucose homeostasis?
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In which disorder does a tumor or lesion destroy a gland leading to inadequate hormone release?
In which disorder does a tumor or lesion destroy a gland leading to inadequate hormone release?
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Which chemical messenger diffuses from the adrenal medulla to the cortex?
Which chemical messenger diffuses from the adrenal medulla to the cortex?
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What is the primary function of Prostacyclin produced by cyclooxygenase?
What is the primary function of Prostacyclin produced by cyclooxygenase?
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Which disorder results in low metabolic rate, weight gain, bradycardia, and constipation?
Which disorder results in low metabolic rate, weight gain, bradycardia, and constipation?
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What characterizes congenital hypothyroidism in infants?
What characterizes congenital hypothyroidism in infants?
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How do hydrophobic hormones like estrogen and T3 typically enter a cell to bind to their receptors?
How do hydrophobic hormones like estrogen and T3 typically enter a cell to bind to their receptors?
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What is the composition of T4 (thyroxine)?
What is the composition of T4 (thyroxine)?
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Which organelle is primarily targeted by thyroid hormone (TH) to increase the rate of aerobic respiration and protein synthesis?
Which organelle is primarily targeted by thyroid hormone (TH) to increase the rate of aerobic respiration and protein synthesis?
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Which hormone requires the mineral iodine for its synthesis?
Which hormone requires the mineral iodine for its synthesis?
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What is the primary mode of action for hydrophilic hormones such as epinephrine that utilize cAMP as a second messenger?
What is the primary mode of action for hydrophilic hormones such as epinephrine that utilize cAMP as a second messenger?
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What is the primary storage form of thyroid hormone in the follicular cells?
What is the primary storage form of thyroid hormone in the follicular cells?
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Which hormones are classified as hydrophobic and require transport proteins for circulation?
Which hormones are classified as hydrophobic and require transport proteins for circulation?
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Which second messenger is typically activated in hydrophilic hormone modes of action, promoting metabolic reactions such as synthesis and secretion?
Which second messenger is typically activated in hydrophilic hormone modes of action, promoting metabolic reactions such as synthesis and secretion?
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When hydrophilic hormones like epinephrine bind to cellsurface receptors, what is the immediate downstream effect in the mode of action?
When hydrophilic hormones like epinephrine bind to cellsurface receptors, what is the immediate downstream effect in the mode of action?
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What is the primary function of C-peptide in insulin formation?
What is the primary function of C-peptide in insulin formation?
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In the context of hydrophilic hormone action, which molecule serves as a common intermediate for activating kinases and enzymes?
In the context of hydrophilic hormone action, which molecule serves as a common intermediate for activating kinases and enzymes?
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Which organelle plays a key role in the conversion of proinsulin to insulin?
Which organelle plays a key role in the conversion of proinsulin to insulin?
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Which clinical manifestation is associated with excess cortisol secretion in Cushing syndrome?
Which clinical manifestation is associated with excess cortisol secretion in Cushing syndrome?
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What is a common symptom of hyperparathyroidism due to excess parathyroid hormone (PTH) secretion?
What is a common symptom of hyperparathyroidism due to excess parathyroid hormone (PTH) secretion?
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What characterizes the role of insulin in diabetes mellitus type II?
What characterizes the role of insulin in diabetes mellitus type II?
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In what disorder is hypoglycemia a common symptom due to excess insulin secretion?
In what disorder is hypoglycemia a common symptom due to excess insulin secretion?
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What is the main effect of adrenal androgen hypersecretion in adrenogenital syndrome?
What is the main effect of adrenal androgen hypersecretion in adrenogenital syndrome?
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Which hormone imbalance results from inadequate secretion of parathyroid hormone (PTH)?
Which hormone imbalance results from inadequate secretion of parathyroid hormone (PTH)?
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What is the primary role of gap junctions in cell communication?
What is the primary role of gap junctions in cell communication?
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In endocrine glands, how are the secretions delivered compared to exocrine glands?
In endocrine glands, how are the secretions delivered compared to exocrine glands?
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What characterizes the action of paracrine hormones?
What characterizes the action of paracrine hormones?
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What distinguishes target cells from other cell types in the body?
What distinguishes target cells from other cell types in the body?
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How do eicosanoids primarily influence neighboring cells?
How do eicosanoids primarily influence neighboring cells?
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Which mechanism is involved in cell communication when neurotransmitters are released from neurons?
Which mechanism is involved in cell communication when neurotransmitters are released from neurons?
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Which organ releases atrial natriuretic peptide to help decrease blood volume and blood pressure?
Which organ releases atrial natriuretic peptide to help decrease blood volume and blood pressure?
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Which hormone is responsible for stimulating glycogenolysis, fat catabolism, and promoting the absorption of amino acids for gluconeogenesis?
Which hormone is responsible for stimulating glycogenolysis, fat catabolism, and promoting the absorption of amino acids for gluconeogenesis?
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What is the primary function of hepcidin in the bloodstream?
What is the primary function of hepcidin in the bloodstream?
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Which type of hormones are derived from cholesterol and have functional groups attached to a 4-ringed steroid backbone?
Which type of hormones are derived from cholesterol and have functional groups attached to a 4-ringed steroid backbone?
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What is the primary function of pancreatic polypeptide secreted by F cells in the pancreas?
What is the primary function of pancreatic polypeptide secreted by F cells in the pancreas?
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Which hormone, when secreted, raises blood glucose levels by acting on liver cells to release glycogen?
Which hormone, when secreted, raises blood glucose levels by acting on liver cells to release glycogen?
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What does somatostatin secreted by delta (d) cells do when there is a rise in blood glucose and amino acids after a meal?
What does somatostatin secreted by delta (d) cells do when there is a rise in blood glucose and amino acids after a meal?
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Which organ produces 15% of erythropoietin, stimulating bone marrow to produce red blood cells?
Which organ produces 15% of erythropoietin, stimulating bone marrow to produce red blood cells?
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What is the precursor molecule that converts into proinsulin in the golgi complex?
What is the precursor molecule that converts into proinsulin in the golgi complex?
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Which hormone is synthesized from tryptophan instead of tyrosine?
Which hormone is synthesized from tryptophan instead of tyrosine?
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What mineral is required for the synthesis of thyroid hormone?
What mineral is required for the synthesis of thyroid hormone?
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Which molecules form T3 and T4 in the synthesis of thyroid hormone?
Which molecules form T3 and T4 in the synthesis of thyroid hormone?
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Which type of hormones are transported in the bloodstream bound to transport proteins?
Which type of hormones are transported in the bloodstream bound to transport proteins?
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What is the composition of Thyroxine (T4) in terms of MIT and DIT molecules?
What is the composition of Thyroxine (T4) in terms of MIT and DIT molecules?
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What is the primary role of somatotropin secreted by the anterior pituitary gland?
What is the primary role of somatotropin secreted by the anterior pituitary gland?
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During childhood and adolescence, what specific growth process does growth hormone stimulate?
During childhood and adolescence, what specific growth process does growth hormone stimulate?
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In adulthood, how does growth hormone primarily affect bone structure?
In adulthood, how does growth hormone primarily affect bone structure?
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What is the primary function of oxytocin released by the posterior pituitary gland?
What is the primary function of oxytocin released by the posterior pituitary gland?
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Which hormone is predominantly secreted by the pineal gland and plays a role in regulating sleep-wake cycles?
Which hormone is predominantly secreted by the pineal gland and plays a role in regulating sleep-wake cycles?
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Where is the thymus located in the body?
Where is the thymus located in the body?
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Which layer of the adrenal cortex produces glucocorticoids like cortisol that affect metabolism?
Which layer of the adrenal cortex produces glucocorticoids like cortisol that affect metabolism?
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What is the primary effect of catecholamines released by the adrenal medulla on metabolic rate?
What is the primary effect of catecholamines released by the adrenal medulla on metabolic rate?
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"Pheochromocytomas" are tumors derived from which cells in the adrenal medulla?
"Pheochromocytomas" are tumors derived from which cells in the adrenal medulla?
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"Calcitonin" produced by parafollicular "C" cells primarily affects which of the following?
"Calcitonin" produced by parafollicular "C" cells primarily affects which of the following?
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What is the primary role of histamine from mast cells in connective tissue?
What is the primary role of histamine from mast cells in connective tissue?
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Which chemical messenger from the adrenal medulla diffuses to the cortex?
Which chemical messenger from the adrenal medulla diffuses to the cortex?
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What is the main function of Prostacyclin produced by cyclooxygenase?
What is the main function of Prostacyclin produced by cyclooxygenase?
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Which disorder results in abnormal bone development, lethargy, and brain damage in infants?
Which disorder results in abnormal bone development, lethargy, and brain damage in infants?
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What happens in acromegaly due to hypersecretion of growth hormones?
What happens in acromegaly due to hypersecretion of growth hormones?
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What is the primary function of Thromboxanes produced by cyclooxygenase?
What is the primary function of Thromboxanes produced by cyclooxygenase?
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What is the long-term effect of sustained high levels of cortisol on the immune system?
What is the long-term effect of sustained high levels of cortisol on the immune system?
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What characterizes the role of ACTH during the Stage of Resistance in stress response?
What characterizes the role of ACTH during the Stage of Resistance in stress response?
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How do Leukotrienes influence allergic and inflammatory reactions?
How do Leukotrienes influence allergic and inflammatory reactions?
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What is the primary effect of aldosterone during the Alarm Reaction stage?
What is the primary effect of aldosterone during the Alarm Reaction stage?
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What distinguishes the speed of the response between the nervous and endocrine systems?
What distinguishes the speed of the response between the nervous and endocrine systems?
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How do the nervous and endocrine systems differ in their area of effect?
How do the nervous and endocrine systems differ in their area of effect?
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What controls homeostasis mechanisms and some endocrine functions?
What controls homeostasis mechanisms and some endocrine functions?
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Which chemical functions as both a hormone and a neurotransmitter?
Which chemical functions as both a hormone and a neurotransmitter?
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What is the primary function of ACTH (Adrenocorticotropic Hormone)?
What is the primary function of ACTH (Adrenocorticotropic Hormone)?
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Which hormone stimulates production of egg or sperm cells?
Which hormone stimulates production of egg or sperm cells?
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Which hormone mainly stimulates hormone production in females?
Which hormone mainly stimulates hormone production in females?
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Where are hormone receptors located for hydrophobic hormones like estrogen, T3, and aldosterone?
Where are hormone receptors located for hydrophobic hormones like estrogen, T3, and aldosterone?
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Which hormone mode of action involves binding to cell-surface receptors?
Which hormone mode of action involves binding to cell-surface receptors?
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What is the primary effect of thyroid hormone (TH) binding to receptors on ribosomes and chromatin?
What is the primary effect of thyroid hormone (TH) binding to receptors on ribosomes and chromatin?
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Which second messenger is activated by hydrophilic hormones like epinephrine?
Which second messenger is activated by hydrophilic hormones like epinephrine?
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What is the downstream effect of activation by alpha 1 G-coupled protein on proteins/enzymes?
What is the downstream effect of activation by alpha 1 G-coupled protein on proteins/enzymes?
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Which organelle is targeted by alpha 2 G-coupled protein to inhibit adenylate cyclase activity?
Which organelle is targeted by alpha 2 G-coupled protein to inhibit adenylate cyclase activity?
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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:
- Hormone binding activates G(s) protein
- Activates adenylate cyclase
- Produces cAMP
- Activates kinases
- Activates enzymes
- 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:
- Alarm reaction
- Stage of resistance
- 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
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Description
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.
