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Chapter 16 Anatomy
Terms in this set (98)
Similarity between the endocrine and nervous system
Both systems work together to maintain homeostasis and both systems use chemicals to communicate with other cells.
difference between the endocrine and nervous system
• Nervous system use neurons that directly affect their target cells through release of neurotransmitters; endocrine system uses hormones secreted into bloodstream to interact with distant cells.
• Nervous system effects are immediate while endocrine effects are seconds to hours or days.
• Nervous system effects are short-lived unless stimulation is repetitive while endocrine effects are longer-lasting.
chemicals are secreted by cells into interstitial fluid; elicits effects from same cell or cell type; thromboxanes (blood clotting); cytokines (WBC's)
chemicals are secreted by cells into extracellular space to affect nearby but different types of cells; histamine (inflammation)
chemicals called hormones secreted by cells into the bloodstream to distant but different types of cells;
Primary organs; examples
have only endocrine functions:
Anterior pituitary, Thyroid gland, Parathyroid, Adrenal cortex, Endocrine pancreas, Thymus
D. Overview of the Endocrine Organs: Endocrine glands (Figure 16.2) Below is a list of functions of the endocrine system (Tables 16.1-16.4). List the organ and hormone(s) that perform each.
Secondary organs; examples
have both endocrine and a variety of non-endocrine functions: heart, kidneys, small intestine, testes and ovaries
secondary endocrine organs: Hypothalamus, Posterior pituitary, Pineal gland, Adrenal medulla; consists of nervous tissue but secretes chemicals that act as hormones (neurohormones)
are the chemical messengers, or chemicals secreted by endocrine glands, that regulate the functions of other cells
process by which target cells produce and display a greater number of receptors in response to a temporary increase in hormone level in blood
Describe how Hormones can affect only certain Target cells
- Hormones are able to affect only particular cells called target cells BECAUSE they contain specific protein receptors to which a particular hormone binds.
- Three-dimensional shapes are highly specific for hormone molecule that they bind and can bind when hormone concentration is extremely low; example of Structure-Function Core Principle
- Receptors are either embedded in plasma membrane or reside within cytosol or nucleus of a target cell
- Hydrophilic hormones are water-soluble, travel as free (unbound) hormones, cannot readily cross plasma membrane so generally interact with receptors found on target cell's plasma membrane; short half-life as they are quickly broken down by enzymes
- Hydrophobic hormones are lipid-soluble, travel as bound hormones to proteins, readily cross the plasma membrane so generally interact with receptors found in cytosol or nucleus; long half-life as they are bound to protein carriers.
process by which target cells decrease number of receptors displayed in response to prolonged exposure to a high level of hormone in blood
amino- acid hormones
consist of one or more amino acids ranging in size from solitary amino acids (amine hormones) to multiple amino acids (peptide hormones), and even complete proteins (protein hormones); generally hydrophilic, binding to plasma membrane receptors
derived from cholesterol; hydrophobic hormones that bind to receptors in cytosol or nucleus
is a portion of the diencephalon and is connected to the pituitary gland by a stalk called the infundibulum.
sits in the stella turcica of the sphenoid bone. It is a gland composed of the following two structurally and functionally distinct components
Anterior pituitary, or adenohypophysis
a true gland composed of hormone- secreting glandular epithelium
- produces many tropic hormones and growth hormones
Posterior pituitary, or neurohypophysis
make up of nervous tissue
- stores ADH and ocytocin produced by the hypothalamus
List 5 Releasing Neurohormones and their effects on the anterior pituitary
1. TRH- increasing thyroid stimulating hormone
2. CRH- increasing ACTH hormone
3. PRH- increase prolactin
4. GnRH- increase LH and FSH
5. GHRH- increase GH
- if anyone knows where this is in the book text me
Hypothalamic-hypophyseal portal system
- Hypothalamic neurons secrete releasing and inhibiting hormones into the hypothalamic capillary bed.
- Hormones travel through portal veins in the infundibulum
- Hypothalamic hormones exit the anterior pituitary capillary bed to bind to receptors on anterior pituitary cells.
- Hypothalamic hormones stimulate or inhibit secretion of hormones from the anterior pituitary cells.
What are the 2 inhibiting neurohormones and their effects on the anterior pituitary?
Describe the 5 Steps in the Mechanism of action of Hydrophilic hormones (this is faster than hydrophobic)
a. Hydrophilic hormones binds to its receptor in the plasma membrane.
b. Receptor activates a peripheral protein. (g-protein)
c. Peripheral protein activates an enzyme. (adenylate cyclase)
d. Enzyme catalyzes formation of a second messenger. (cAMP)
e. The second messenger initiates a series of events in the cell that leads to changes in its activation of protein kinases that catalyze transfer of a phosphate group from ATP to another molecule, called phosphorylation.
is made from amino acids, produced primarily in the white adipose tissue, acts on receptors in the hypothalamus, and inhibits appetite by (1) counteracting the effects of feeding stimulants and (2) promoting the synthesis of an appetite suppressant. Leptin belongs to what class of chemical signals? Endocrine. What is the target tissue of leptin? Hypothalamus, white adipose tissue. Leptin is free because it's made from amino acids. Leptin most likely has a short half-life because it is not bound to anything. Progesterone, testosterone, aldosterone, and estrogen have long half-lives. Hydrophilic - lectin. Leptin is most likely acutely secreted because it is secreted after eating with hunger cycle. It has an inhibitory effect because it will synthesize an appetory suppressant.
Describe the 4 Steps in the Mechanisms of action of Hydrophobic hormones
a. Hydrophobic hormones crosses plasma membrane where they interact with intracellular receptors in cytosol or nucleus.
b. Hormone complex enters nucleus and interacts with DNA of target cell acting as transcription factor.
c. mRNA is produced and exits the nucleus.
d. mRNA binds to ribosome and exerts its effects by changing rate of protein synthesis of one or more proteins.
some endocrine cells increase or decrease their secretion in response to secretion of other hormones. Ex: thyroid hormone.
Describe 5 possible effects of hormone actions:
-Stimulate secretion from an endocrine or exocrine cell.
-Activate or inhibit enzymes.
-Stimulate or inhibit mitosis and or meiosis.
-Open or close ion channels in cells' plasma membrane altering its membrane potential.
-Activate or inhibit transcription of genes that code for RNA or proteins.
-First 4 hydrophilic, last one hydrophobic.
many endocrine cells respond to concentration of a certain ion or molecule in blood or extracellular fluid. Ex: parathyroid hormone and calcitonin exhibit humoral regulation.
some endocrine cells respond to signals from nervous system. Ex: norepinephrine and epinephrine.
Many hormones have complimentary actions; each hormone interacts with a different target cell in order to accomplish a common goal. Some hormones (synergists) can act on same target cell to exert same effect; effect is more pronounced with interaction of multiple hormones than any one individual hormone by itself. Ex: growth hormone and testosterone.
Illustrate the 3 main patterns of hormone secretion
1) Chronic hormone secretion- ex: thyroid hormone.
2) Acute hormone secretion- staggered effect, only when needed.
3) Episodic hormone secretion- cyclic, example: menstrual cycle.
Describe the 5 steps in the feedback loop that regulates hormone secretion
a. Stimulus: a regulated physiological variable deviates from its normal range.
b. Receptor: receptors on target cells detect deviation of variable.
c. Control Center: when stimulated (often endocrine cell) increases or decreases its secretion of a particular hormone.
d. Effector/Response: hormone triggers a response in its target cells that moves conditions toward normal range.
e. Homeostatic Range: as the variable returns to normal, feedback to the control center decreases the effector response.
Some hormones called antagonists act on same cells but have opposite effects. Ex: insulin and glucagon.
Stimulates the secretion of other hormones from target tissues. Ex: ACTH, LH, FSH.
induce growth in target cells; note that some hormones have both tropic and trophic effects on target cells. Ex: growth hormone.
hypothalamus releases hormones.
anterior pituitary releases hormones. Tropic hormones.
target organs release hormones.
Effects of the Multi-tiered Negative feedback control of anterior pituitary hormones
hormone levels increase. Effects on other cells- return to normal range.
Describe the widespread effects and regulation of growth hormone.
GH released periodically throughout day, with peak secretion occurring during sleep. Main function is to regulate growth of various target tissues including skeletal and cardiac muscle, adipose, liver, cartilage and bone; can be either short-term (metabolic) or long-term effects (promote production of insulin-like growth factor) GH increases during exercise, stress, and fasting. Regulated by GHRH and somatostatin in negative feedback loop.
hypersecretion of GH before epiphyseal plates have closed; leads to extremely tall individuals; excess GH also increases size of other tissues such as heart.
hypersecretion of GH after epiphyseal plate closure; most affected are tissues of head, face, hands, feet, s well as liver and heart; progressively distorts these various organs; can lead to heart failure.
a condition of GH hyposecretion; leads to individuals that are short in stature but with otherwise proportional limbs and trunk.
located anterior to the trachea composed of follicular cells that produce and secrete thyroid hormones and parafollicular cells, which produce and secrete calcitonin.
located in posterior surface of thyroid gland and secrete PTH
from their chief cells
- Para means next to or nearby.
symptoms: fatigue, weight gain, bradycardia, constipated, cold intolerance, slow heart rate, low blood pressure, and a goiter. TRH and TSH are decreased.
Thyroid Hormone: Metabolic Regulator
Thyroid hormone derived from the amino acid tyrosine bound to iodine atoms to form either triiodothyronine,( T3) or thyroxine (T4). They are lipid-soluble and bind to nuclear receptors.
Describe 3 Main categories of Effects of thyroid hormone
a. Regulation of metabolic rate and thermoregulation-
TH sets basal metabolic rate (amount of energy required by body at rest) by increasing rate of ATP consumption, increasing gluconeogenesis; heat is generated for core body temperature homeostasis.
b. Promotion of growth and development-
Thyroid hormones are required for normal bone growth, muscle growth, and nervous system development.
c. Synergism with the sympathetic nervous system- TH acts on target cells of sympathetic nervous system and increase or up regulate receptors for sympathetic neurotransmitters; affects regulation of blood pressure, heart rate, and other sympathetic activities.
Thyroid hormone stimulates the synthesis of mitochondria.
Describe the Steps of Thyroid hormone production
- Iodide ions are actively transported into follicle cell and secreted into colloid; converted to iodine atoms that attach to thyroglobulin.
- Thyroglobulin- large thyroid hormone precursor protein; secreted by follicle cells into colloid.
- Iodinated thyroglobulin enters follicle cell by endocytosis and is converted to T4 and T3 by lysosomal enzymes.
- T4 and T3 are finally released into bloodstream.
- Many target tissues can convert T4 to more active T3; T4 lasts longer in blood than T3 so acts as a reservoir for potential T3.
Regulation of thyroid hormone production
of T3 and T4 production is regulated by a negative feedback loop starting with thyrotropin releasing hormone (TRH), made by the hypothalamus, promoting the release of thyroid stimulating hormone (TSH) from the anterior pituitary gland, which stimulates the production of T3 and T4 from the thyroid gland
symptoms: fatigue, weight loss, tachycardia, diarrhea, heat intolerance, disruptions in blood pressure and heart rhythms, development of a goiter and exophthalmos (protruding of eyeballs and enlargement of thyroid gland) T3 and T4 are elevated.
Parathyroid Hormone and Calcitonin
Calcium Ion Homeostasis. Thus, these hormones are antagonists. PTH increases osteoclasts activity. Calcitonin increases activity of osteoblasts.
List the 3 effects of Parathyroid hormone (PTH) secretion.
Chief cells secrete parathyroid hormone and thyroid secretes calcitonin, both of which have opposing effects on calcium ion concentration in blood; keeps this vital ion within a normal range.
3 effects: bone, kidney, and small intestine. Bone: stimulating osteoclasts activity. Kidney: increased reabsorption of calcium. Small intestine: absorb calcium. Hyperparathyroidism would lead to hypercalcemia.
Describe the effect of Calcitonin on bone.
Primary target is osteoclast cells in bone; osteoclast activity is inhibited by presence of calcitonin; allows osteoblast activity. Unopposed osteoblast activity reduces blood calcium ion levels as these ions are taken up into bone matrix.
Regulation of calcium ion homeostasis:
Regulation involves a negative feedback loop that maintains calcium ions with a normal range and proceeds in the following manner
Describe each step:
a. Stimulus: blood calcium ion level decreases below range.
b. Receptor: chief cells in parathyroid gland detect a low blood calcium level.
c. Control center: chief cells increase PTH secretion.
d. Effector/Response: effects of PTH on target cells increase blood calcium ion concentration.
e. Homeostatic range and negative feedback: blood calcium ion level returns to normal range; negative feedback to chief cells decreases PTH secretion.
decrease in mineral density of bone.
outside of adrenal gland. Located on top of kidneys
middle or outside of adrenal gland. Located on top of kidneys.
hypothalamic-pituitary adrenocortical axis. (HPA)
Production of steroid hormones from three zones of cortex is partially regulated by a multi-tiered negative feedback loop
main role is to help mediate body's response to stress; cortisol (hydrocortisone) is most potent glucocorticoid.
high potassium levels
low sodium levels
Hormones of the Adrenal Medulla
are derived from nervous tissue and secrete catecholamines called epinephrine and norepinephrine. Epinephrine or adrenaline combines with adrenergic receptors.
Describe the 4 effects of Aldosterone and its regulation
1. Maintains concentrations of extracellular sodium and potassium ions within their normal ranges critical to functioning of muscle cells and neurons.
2. Regulates extracellular fluid volume: effects on sodium ions in kidney tubule cells create a concentration gradient that favors movement of water by osmosis from fluid in those tubules to extracellular fluid and blood.
3. Maintains blood pressure through renin-angiotensin-aldosterone system (RAAS); functions to increase blood pressure.
4. Maintains acid-base homeostasis; activates hydrogen ion pumps, lowering H+ concentration (pH) of blood, preserving slightly alkaline pH.
5. Regulation by decreased Na+ levels, increased K+ and H+ levels, and low blood pressure.
C. Describe the effects of Cortisol and its regulation
1. stimulates liver cells to synthesize enzymes involved in gluconeogenesis (production of new glucose molecules from amino acids and fatty acids); increase blood glucose levels.
2. induces breakdown of proteins in skeletal muscle; releases free amino acids into blood
3. acts on adipocytes to release fatty acids into blood
4. potent anti-inflammatory that decreases levels of certain leukocytes.
hypersecretion from adrenal cortex or Iatrogenic Cushing's syndrome- disorder caused by long-term administration of glucocorticoid- containing products.
releases fatty acids; moon facies; "buffalo hump"
-Hyposecretion of both cortisol and aldosterone
- bronzing of skin.
Regulation of the adrenal medulla includes the sympathetic nervous system and the
Describe the 6 effects of epinephrine
- Increase rate and force of heart contraction.
- Dilate bronchioles and lungs.
- Constrict blood vessels supplying skin, digestive organs, and urianr organs: increases blood pressure.
- Dilate blood vessels supplying skeletal muscles.
- Dilate pupils.
- Decrease digestive and urinary functions.
Describe the Structure of the Pancreas
It is a retroperitoneal gland located around the loop of the duodenum. It is 2 organs in one. It is exocrine organ for digestive enzymes and pancreatic islets.
alpha cells that will raise blood sugar because it is secreted when blood sugar is low. Target cells are cells of liver, muscle tissue, and adipose. Formation of fuel molecules called ketone bodies in liver that accumulate low blood pH called ketonosis.
beta cells, lowers blood sugar and is released when blood sugar is high. It will stimulate the production of glucose receptors so we can take glucose into the cell. Primary antagonist of glucagon. Stimulates responses in target cells of liver, cardiac muscle, and skeletal muscle.
blood glucose levels are too low.
- blood glucose levels are too low; can be caused by elevated insulin levels; symptoms- weakness, dizziness, rapid breathing, nausea, and sweating.
blood glucose levels are too high.
-common cause of chronic hyperglycemia is Diabetes Mellitus.
type 1 diabetes
juvenile onset, insulin dependent, and an autoimmune disease. Disease caused by destruction of beta islet cell tht produce and secrete insulin. Target cells are unable to take in circulating glucose. Glucose is overproduced in liver because of unopposed actions of glucagon; glucagon also elevates level of ketone bodies in blood. Diabetic ketoacidosis. Leads to glucose and ketones in urine.
type II diabetes
non-insulin dependent. Disease in which insulin's target tissues become insensitive to insulin (insulin resistance). Results in hyperglycemia and accompanying characteristic signs and symptoms, such as glycosuria, polyuria, and polydipsia; hereditary and obesity.
Describe the steps of the negative feedback loop if blood glucose INCREASES
a. Stimulus: blood glucose level increases above normal range, in response to feeding or hormones such as cortisol.
b. Receptor: beta cells of pancreas detect increased glucose concentration
c. Control center: beta cells increase glucagon secretion; beta cells decrease insulin secretion.
d. Effector/Response: glucagon triggers breakdown of glycogen (glycogenosis) into glucose and formation of new glucose (glucoeogenosis)
e. Homeostatic range and negative feedback: as the blood glucose level returns to normal , feedback to beta cells decreases insulin secretion.
Describe the steps of the negative feedback loop if blood glucose DECREASES
a. Stimulus: blood glucose level decreases below its normal range.
b. Receptor: alpha cells of the pancreas detect the decreased blood glucose concentration.
c. Control center: alpha cells increase glucagon secretion.
d. Effector/Response: breakdown of glycogen into glucose, formation of new glucose.
e. Homeostatic range and negative feedback: as the blood glucose level returns to normal, feedback to alpha cells decreases glucagon secretion.
Pineal Gland secretes Melatonin
epithalamus, of the diencephalon of the brain, secretes the neurohormone, related to light and dark cycles, main target tissues are the sleep-regulation centers in the reticular formation of the brainstem, where it appears to adjust the sleep-wake cycle in some individuals.
Thymosin and Thymopoietin: location where T-lymphocytes mature; paracrine signals
Sex Hormones: The testes and ovaries are the primary male and female reproductive organs or gonads, respectively. The gonads are responsible for the production of gametes, sperm in males, and ova, or eggs, in females. These produce sex steroid hormones responsible for gamete production and other functions.
Adipose tissue: Leptin
Adipocytes produce the protein hormone which is able to cross the blood-brain barrier where it interacts with neurons in the hypothalamus, its main target tissue. The action of leptin is to induce satiety.
The heart: Atrial Natriuretic Peptide (ANP):
cardiac muscle cells contain stretch-sensitive ion channels that open more widely when the blood volume inside the heart increases. ANP triggers vasodilation, an increase in vessel diameter, and enhances excretion of Na+ ions from the kidneys, decreasing blood volume and lower blood pressure.
The kidneys: Erythropoietin (EPO):
stimulates RBC production with decreased oxygen conc.
- Conversion of vitamin D to its active form under the influence of parathyroid hormone
vital component of the renin-angiotensin-aldosterone system (RAAS), which maintains blood pressure.
A. Hormonal Control of Fluid Homeostasis: ADH, aldosterone, and ANP are involved in fluid homeostasis
have to secrete some hormones to keep us from being dehydrated: fluid homeostasis. Contributes to low blood pressure. ADH- secreted when water levels are low to cause posterior pituitary to secrete ADH, ADH is affected by kidneys and kidneys reabsorb water. Aldosterone- increased with low levels of water. Causes us to reabsorb sodium, secreted when blood pressure is low. ANP- atrial natriuretic peptide, which tells you tis a protein. Secreted when blood volume is high. Secreted by right atrium.
Hormonal Control of Metabolic Homeostasis:
Thyroid hormone, insulin and glucagon and catecholamines are involved in metabolic homeostasis.
at rest while fasting
thyroid hormones determine basal metabolic rate.
at rest while feeding
feeding causes increased blood glucose levels that increase insulin secretion.
Insulin and leptin both promote
satiety in hypothalamus
catecholamine's control metabolic rate and glucagon secretion increases; sympathetic nervous system increases catecholamine secretion from adrenal medulla.
Hormonal Response to Stress: Putting It All Together: The Big Picture
1. Exercise stresses the body.
2. Hypothalamus releases GnRH and CRH.
Sympathetic nervous system is activated.
3a. ACTH triggers release of cortisol, aldosterone, and catecholamine's.
3b. Sympathetic NS triggers release of glucagon.
4a. Aldosterone increases Na+ and h20 retention in the kidneys, increasing blood pressure.
4b. GH, cortisol, catecholamines, glucagon trigger an increased release of metabolic fuels from the liver and adipose tissues.
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