Human Anatomy and Physiology II KAAP310-14S Lectures: Tue Thu 9:30-10:45 Kirkbride 004
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Transcript of Human Anatomy and Physiology II KAAP310-14S Lectures: Tue Thu 9:30-10:45 Kirkbride 004
Department of Kinesiology and Applied Physiology WCR
Human Anatomy and Physiology II KAAP310-15F
Lecture: Kirkbride 004, Tue, Thu 11:00-12:15
Course Web Site www.udel.edu/sakai
William Rose [email protected] Rust 148
Department of Kinesiology and Applied Physiology WCR
Human Anatomy and Physiology II KAAP310-15F
Labs (HSC 228)020 Thu 12:30-2:25 (Jahyun Kim)021 Fri 8:00 – 9:55 (Jahyun Kim)022 Fri 10:10 – 12:05 (Jahyun Kim)023 Fri 12:20 – 2:15 (Joe Watso)
Run: Tuesdays 12:45-1:30, from CSB entrance, 1-2 miles relaxed pace.
Department of Kinesiology and Applied Physiology WCR
Human Anatomy and Physiology IIKAAP310-15F
Grading – see syllabus.
75% Classroom 70%: Ten tests (worst is dropped so nine count) 5%: Clicker
25% Laboratory
Department of Kinesiology and Applied Physiology WCR
Human Anatomy and Physiology IIKAAP310-15F
UD Capture: Recording of what is projected on screen and classroom audio. http://udcapture.udel.edu/2015s/kaap310-010/
Clickers: Register your clicker on Sakai.
Clicker questions: 1 point for answering, 1 more point if correct.
Clicker grade: Full credit if you get 75% or more of the points available. Reduced proportionally if not.
Using more than one clicker is academic dishonesty and may be referred to the Office of Syduent Conduct.
No adjustments for forgotten or broken clickers, low batteries, etc.
Human Anatomy and Physiology IIKAAP310-15F
Tips
This class is not the same as KAAP 309.
Do not rely on memorization.
Understanding physiology requires knowing more than the what or where. You need to understand the why and the how.
Human Anatomy and Physiology IIKAAP310-15F
TipsEveryone will work hard.Read the book, come to class, ask questions.Use the recorded lectures to review and not as
a substitute for coming to class. Use the online resources.
Exam Questions
KnowledgeComprehensionApplication
Knowledge Question________ are chemical messengers that are released in one tissue and transported in the bloodstream to alter the activities of specific cells in other tissues.
A.Hormones
B.Neuropeptides
C.Neurotransmitters
D.Humoral antibodies
E.none of the above
Comprehension QuestionAn activated G protein can trigger A.the opening of calcium ion
channels in the membrane.
B.the release of calcium ions from intracellular stores.
C.a fall in cAMP levels.
D.a rise in cAMP levels.
E.all of the above
Application QuestionDestruction of the supraoptic nucleus of the hypothalamus would have which result?
A.loss of emotional response B.loss of GH secretion C.loss of ADH secretion D.loss of loss of regulatory factor secretionE.loss of melatonin secretion
Endocrine System: Overview
• Acts with the nervous system to coordinate and integrate the activity of body cells
• Influences metabolic activities by means of hormones transported in the blood
• Responses occur more slowly but tend to last longer than those of the nervous system
• Endocrinology
• Study of hormones and endocrine organs
• Controls and integrates
• Reproduction
• Growth and development
• Maintenance of electrolyte, water, and nutrient balance of blood
• Regulation of cellular metabolism and energy balance
• Mobilization of body defenses
Figure 16.1
Pineal glandHypothalamus
Pituitary gland
Parathyroid glands(on dorsal aspectof thyroid gland)Thymus
Thyroid gland
Adrenal glands
Pancreas
Ovary (female)
Testis (male)
Other tissues and organs that produce hormones: adipose cells, thymus, cells in walls of the small intestine, stomach, kidneys, heart
Chemical Messengers
• Hormones: long-distance chemical signals that travel in the blood or lymph
• Autocrines: chemicals that exert effects on the same cells that secrete them
• Paracrines: locally acting chemicals that affect cells other than those that secrete them
• Autocrines and paracrines are local chemical messengers and will not be considered part of the endocrine system
Mechanisms of Hormone Action
• Hormone action on target cells may be to
• Alter plasma membrane permeability of membrane potential by opening or closing ion channels
• Stimulate synthesis of proteins or regulatory molecules
• Activate or deactivate enzyme systems
• Induce secretory activity
• Stimulate mitosis
Chemistry of Hormones
• Two main classes
1.Amino acid-based hormones
• Amino acid derivatives, peptides, and proteins
2.Steroids
• Synthesized from cholesterol
• Gonadal and adrenocortical hormones
1. Water-soluble hormones (all amino acid–based hormones except thyroid hormone)
• Two mechanisms, depending on their chemical nature
1. Water-soluble hormones (all amino acid–based hormones except thyroid hormone)
• Cannot enter the target cells
• Act on plasma membrane receptors
• Coupled by G proteins to intracellular second messengers that mediate the target cell’s response
Hormone (1st messenger)binds receptor.
Receptor
Extracellular fluid
Cytoplasm
G protein (GS)
Cannot enter the target cells. Act on plasma membrane receptors. Coupled by G proteins to intracellular second messengers that mediate the target cell’s response
Receptor-hormonecomplex
Receptorprotein
Cytoplasm
Nucleus
Extracellular fluid
Steroidhormone
The steroid hormonediffuses through the plasmamembrane and binds anintracellular receptor that directly activates genes.
Plasmamembrane
2. Lipid-soluble hormones (steroid/thyroid hormones)
Figure 16.2
Hormone (1st messenger)binds receptor.
Receptoractivates Gprotein (GS).
G proteinactivatesadenylatecyclase.
cAMP acti-vates proteinkinases.
Adenylatecyclaseconverts ATPto cAMP (2ndmessenger).
Receptor
G protein (GS)
Adenylate cyclase
Triggers responses oftarget cell (activatesenzymes, stimulatescellular secretion,opens ion channel,etc.)
Hormones thatact via cAMPmechanisms:
EpinephrineACTHFSHLH
Inactiveprotein kinase
Extracellular fluid
Cytoplasm
Activeproteinkinase
GDP
GlucagonPTHTSHCalcitonin
1
2 3 4
5
Plasma Membrane Receptors and Second-Messenger Systems - cAMP
Plasma Membrane Receptors and Second-Messenger Systems
• cAMP signaling mechanism
• Activated kinases phosphorylate various proteins, activating some and inactivating others
• cAMP is rapidly degraded by the enzyme phosphodiesterase
• Intracellular enzymatic cascades have a huge amplification effect
Plasma Membrane Receptors and Second-Messenger Systems
• PIP2-calcium signaling mechanism
http://www.ruf.rice.edu/~rur/issue1_files/barron.html
•DAG activates protein kinases; IP3 triggers release of Ca2+
•Ca2+ alters enzymes or channels or binds to the regulatory protein calmodulin
PIP2 – phosphatidyl inositol bisphosphate
Other Signaling Mechanisms
• Cyclic guanosine monophosphate (cGMP) is second messenger for some hormones
• Some work without second messengers
• E.g., insulin receptor is tyrosine kinase enzyme that autophosphorylates upon insulin binding docking for relay proteins that trigger cell responses
Figure 16.3, step 5
mRNA
New protein
DNA
Hormoneresponseelements
Receptor-hormonecomplex
Receptorprotein
Cytoplasm
Nucleus
Extracellular fluid
Steroidhormone
The steroid hormonediffuses through the plasmamembrane and binds anintracellular receptor.
The receptor-hormone complex entersthe nucleus.
The receptor- hormonecomplex binds a hormoneresponse element (aspecific DNA sequence).
Binding initiatestranscription of thegene to mRNA.
The mRNA directsprotein synthesis.
Plasmamembrane
1
2
3
4
5
Intracellular Receptors and Direct Gene Activation
Target Cell Specificity
• Target cells must have specific receptors to which the hormone binds
• ACTH receptors are only found on certain cells of the adrenal cortex
• Thyroxin receptors are found on nearly all cells of the body
Target Cell Activation
• Target cell activation depends on three factors
1. Blood levels of the hormone
2. Relative number of receptors on or in the target cell
3. Affinity of binding between receptor and hormone
• Hormones influence the number of their receptors
• Up-regulation—target cells form more receptors in response to the hormone
• Down-regulation—target cells lose receptors in response to the hormone
Hormones in the Blood
• Hormones circulate in the blood either free or bound
• Steroids and thyroid hormone are attached to plasma proteins
• All others circulate without carriers
• The concentration of a circulating hormone reflects:
• Rate of release
• Speed of inactivation and removal from the body
• Hormones are removed from the blood by
• Degrading enzymes
• Kidneys
• Liver
Half-life—the time required for a hormone’s blood level to decrease by half
Interaction of Hormones at Target Cells
• Multiple hormones may interact in several ways
• Permissiveness: one hormone cannot exert its effects without another hormone being present
• Synergism: more than one hormone produces the same effects on a target cell
• Antagonism: one or more hormones opposes the action of another hormone
• Permissiveness: one hormone cannot exert its effects without another hormone being present
• Synergism: more than one hormone produces the same effects on a target cell
• Antagonism: one or more hormones opposes the action of another hormone
Control of Hormone Release
• Blood levels of hormones
• Are controlled by negative feedback systems
• Vary only within a narrow desirable range
• Hormones are synthesized and released in response to
1. Humoral stimuli
2. Neural stimuli
3. Hormonal stimuli
Humoral Stimuli
• Changing blood levels of ions and nutrients directly stimulates secretion of hormones
• Examples:
Figure 16.4a
(a) Humoral Stimulus
Capillary (lowCa2+ in blood)
Parathyroidglands
Thyroid gland(posterior view)
PTH
Parathyroidglands
1 Capillary blood containslow concentration of Ca2+,which stimulates…
2 …secretion ofparathyroid hormone (PTH)by parathyroid glands*
•Declining blood Ca2+ concentration stimulates the parathyroid glands to secrete PTH (parathyroid hormone)
•PTH causes Ca2+ concentrations to rise and the stimulus is removed
Humoral Stimuli
Figure 16.4b
(b) Neural Stimulus
CNS (spinal cord)
Medulla ofadrenalgland
Preganglionicsympatheticfibers
Capillary
1 Preganglionic sympatheticfibers stimulate adrenalmedulla cells…
2 …to secrete catechola-mines (epinephrine andnorepinephrine)
• Nerve fibers stimulate hormone release
• Sympathetic nervous system fibers stimulate the adrenal medulla to secrete catecholamines
Neural Stimuli
Figure 16.4c
(c) Hormonal Stimulus
Hypothalamus
Thyroidgland
Adrenalcortex
Gonad(Testis)
Pituitarygland
1 The hypothalamus secreteshormones that…
2 …stimulatethe anteriorpituitary glandto secretehormonesthat…
3 …stimulate other endocrineglands to secrete hormones
Hormonal Stimuli• Hormones stimulate other
endocrine organs to release their hormones
• Hypothalamic hormones stimulate the release of most anterior pituitary hormones
• Anterior pituitary hormones stimulate targets to secrete still more hormones
• Hypothalamic-pituitary-target endocrine organ feedback loop: hormones from the final target organs inhibit the release of the anterior pituitary hormones
Nervous System Modulation
• The nervous system modifies the stimulation of endocrine glands and their negative feedback mechanisms
• Example: under severe stress, the hypothalamus and the sympathetic nervous system are activated
• As a result, body glucose levels rise
The Pituitary Gland and Hypothalamus
• “Master gland”, hypophysis, 600 mg (!)
• In hypophyseal fossa, above sella turcica of sphenoid bone
• Posterior pituitary (neurohypophysis)
• Anterior pituitary (adenohypophysis)
Pituitary-Hypothalamic Relationships
• Posterior lobe (neurohypophysis)
• A downgrowth of hypothalamic neural tissue
• Neural connection to the hypothalamus (hypothalamic-hypophyseal tract)
• Nuclei of the hypothalamus synthesize the neurohormones oxytocin and antidiuretic hormone (ADH)
• Neurohormones are transported to the posterior pituitary
Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH).
Oxytocin and ADH are stored in axon terminals in the posterior pituitary.
When hypothalamic neurons fire, action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood.
1
2
3
4OxytocinADH
Posterior lobeof pituitary
Opticchiasma
Infundibulum(connecting stalk)
Hypothalamic-hypophyseal
tract
Axon terminals
Posterior lobeof pituitary
Paraventricular nucleus
Hypothalamus
Supraopticnucleus
Inferiorhypophysealartery
Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary.
Pituitary-Hypothalamic Relationships
• Anterior Lobe (adenohypophysis):
• Originates as an out-pocketing of the oral mucosa
• Hypophyseal portal system
• Primary capillary plexus
• Hypophyseal portal veins
• Secondary capillary plexus
• Carries releasing and inhibiting hormones to the anterior pituitary to regulate hormone secretion
Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary.
In response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus. This in turn empties into the general circulation.
GH, TSH, ACTH,FSH, LH, PRL
Anterior lobeof pituitary
When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus.
Hypophysealportal system• Primary capillary plexus• Hypophyseal portal veins• Secondary capillary plexus
Superiorhypophyseal
artery
Anterior lobeof pituitary
Hypothalamus Hypothalamicneurons synthesizeGHRH, GHIH, TRH,CRH, GnRH, PIH.
A portal system is two capillary plexuses (beds) connected by veins.
12
3
Anterior Pituitary Hormones
• Growth hormone (GH)
• Thyroid-stimulating hormone (TSH) or thyrotropin
• Adrenocorticotropic hormone (ACTH)
• Follicle-stimulating hormone (FSH)
• Luteinizing hormone (LH)
• Prolactin (PRL)
• All are proteins
• All except GH activate cyclic AMP second-messenger systems at their targets
• TSH, ACTH, FSH, and LH are all tropic hormones (regulate the secretory action of other endocrine glands)
Figure 16.6
Growth hormone
Feedback Inhibits GHRH releaseStimulates GHIHreleaseInhibits GH synthesisand release
Anteriorpituitary
Liver andother tissues
Indirect actions(growth-promoting)
Direct actions(metabolic,anti-insulin)
Insulin-like growthfactors (IGF-1)
ExtraskeletalSkeletal FatCarbohydratemetabolism
Increased cartilageformation and
skeletal growth
Increased proteinsynthesis, andcell growth and
proliferation
Increasedfat breakdown
and release
Increased bloodglucose and otheranti-insulin effects
EffectsEffects
Produce
Hypothalamussecretes growthhormone—releasinghormone (GHRH), andsomatostatin (GHIH)
Initial stimulus
Physiological response
Result
Increases, stimulates
Reduces, inhibits
•Stimulates most cells, but targets bone and skeletal muscle•Promotes protein synthesis and encourages use of fats for fuel•Most effects are mediated indirectly by insulin-like growth factors (especially IGF-1)
Growth Hormone (GH or Somatotropin)
Figure 16.6
Growth hormone
Feedback Inhibits GHRH releaseStimulates GHIHreleaseInhibits GH synthesisand release
Anteriorpituitary
Liver andother tissues
Indirect actions(growth-promoting)
Direct actions(metabolic,anti-insulin)
Insulin-like growthfactors (IGF-1)
ExtraskeletalSkeletal FatCarbohydratemetabolism
Increased cartilageformation and
skeletal growth
Increased proteinsynthesis, andcell growth and
proliferation
Increasedfat breakdown
and release
Increased bloodglucose and otheranti-insulin effects
EffectsEffects
Produce
Hypothalamussecretes growthhormone—releasinghormone (GHRH), andsomatostatin (GHIH)
Initial stimulus
Physiological response
Result
Increases, stimulates
Reduces, inhibits
GH release is regulated by
•Growth hormone–releasing hormone (GHRH)
•Growth hormone–inhibiting hormone (GHIH) (somatostatin)
Growth Hormone (GH or Somatotropin)
Homeostatic Imbalances of Growth Hormone
• Hypersecretion
• In children results in gigantism
• In adults results in acromegaly
• Hyposecretion
• In children results in pituitary dwarfism
Figure 16.7
Hypothalamus
Anterior pituitary
Thyroid gland
Thyroidhormones
TSH
TRH
Target cellsStimulates
Inhibits
Thyroid-Stimulating Hormone (Thyrotropin)
Regulation:
• Stimulated by thyrotropin-releasing hormone (TRH)
• Inhibited by rising blood levels of thyroid hormones that act on the pituitary and hypothalamus
Figure 16.7
Hypothalamus
Anterior pituitary
Thyroid gland
Thyroidhormones
TSH
TRH
Target cellsStimulates
Inhibits
Thyroid-Stimulating Hormone (Thyrotropin)
• Produced by thyrotrophs of the anterior pituitary
• Stimulates the normal development and secretory activity of the thyroid
Adrenocorticotropic Hormone (Corticotropin)
• Secreted by corticotrophs of the anterior pituitary
• Stimulates the adrenal cortex to release corticosteroids
• Regulation of ACTH release
• Triggered by hypothalamic corticotropin-releasing hormone (CRH) in a daily rhythm
• Internal and external factors such as fever, hypoglycemia, and stressors can alter the release of CRH
Gonadotropins
• Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
• Secreted by gonadotrophs of the anterior pituitary
• FSH stimulates gamete (egg or sperm) production
• LH promotes production of gonadal hormones
• Absent from the blood in prepubertal boys and girls
• Regulation of gonadotropin release
• Triggered by the gonadotropin-releasing hormone (GnRH) during and after puberty
• Suppressed by gonadal hormones (feedback)
Prolactin (PRL)
• Secreted by lactotrophs of the anterior pituitary
• Stimulates milk production, slowly and long term
• Regulation of PRL release
• Primarily controlled by prolactin-inhibiting hormone (PIH) (now known to be dopamine)
• Blood levels rise toward the end of pregnancy
• Suckling stimulates PRH release and promotes continued milk production
Adapted from Fahlbusch R: Endocrinol Metab Clin 21:669, 1992. Fauci et al., Harrison's Principles of Internal Medicine, 17th ed. from www.accessmedicine.com.
Transsphenoidal resection of pituitary mass via the
endonasal approach.
“Hypogonadism Due to Pituicytoma in an Identical Twin”
H. H. Newnham & L. M. Rivera-Woll
New Engl J Med 359: 2824, 2008
See here.
The Posterior Pituitary
• Contains axons of hypothalamic neurons
• Stores antidiuretic hormone (ADH) and oxytocin
• ADH and oxytocin are released in response to nerve impulses
• Both use PIP-calcium second-messenger mechanism at their targets
Oxytocin
• Stimulates uterine contractions during childbirth
• Also triggers milk ejection (“letdown” reflex) in women producing milk
• Suckling stimulates oxytocin release: positive feedback loop, with infant completing the loop
• Acts as a neurotransmitter in brain: the love hormone
Antidiuretic Hormone (ADH)
• Hypothalamic osmoreceptors respond to changes in the solute concentration of the blood
• Other name: vasopressin
• If solute concentration is high
• Osmoreceptors depolarize and transmit impulses to hypothalamic neurons
• ADH is synthesized and released, inhibiting urine formation
Antidiuretic Hormone (ADH)
• ADH works at the kidney to control water loss
• If solute concentration is high (sensed by osmoreceptors in the hypothalamus)
• A large amount of ADH is released, inhibiting water loss
• If solute concentration is low
• ADH is not released, allowing water loss
• Alcohol inhibits ADH release and causes copious urine output
Homeostatic Imbalances of ADH
• ADH deficiency: diabetes insipidus. Huge output of urine and intense thirst
• ADH hypersecretion (after neurosurgery, trauma, or secreted by cancer cells)—syndrome of inappropriate ADH secretion (SIADH)
Case Study
History of Present Illness:
Lucia Sanchez is a 24 year-old woman who presented to her physician with a chief complaint of urinary frequency (polyuria) and excessive thirst (polydipsia). Her polyuria began abruptly two weeks prior to her doctor's appointment. Prior to that time, Lucia voided approximately five times per day. She estimated that she was now voiding twenty times per day. Two days prior to her visit to the doctor's office she was advised to collect her urine in order to check its volume in a 24 hour period; her total urine volume measured 12 liters. Lucia also noticed an intense craving for ice water that began at about the same time as her polyuria. If she did not have access to water, she would become extremely thirsty and dizzy. She denied any change in her appetite. She also denied the use of any medications.
Case Study
Case Study
Lucia was hospitalized and underwent an oral dehydration test. She was denied any fluid intake, and doctors carefully analyzed her vital signs and urine output during this process. Because she had been advised to drink a lot of water before coming to the hospital, her initial supine and upright blood pressure were normal. The analysis showed that Lucia was urinating at a rate of approximately 500 cc's per hour; her urine specific gravity remained at 1.001 even though she became dehydrated to the point where she became orthostatic (her blood pressure dropped when she changed from the supine to the upright position).
Case Study
Diagnosis: Central diabetes insipidus
Lucia was given ADH which resulted in a marked decline in her urine output from 500 cc/hour to 70 cc/hour. Nurses administered IV fluids to correct her dehydration. Lucia was discharged and instructed to take desmopressin acetate, an oral form of ADH. This will mimic her physiologic levels of ADH, and help her kidneys retain water.
An overview of the relationships between hypothalamic and pituitaryhormones, and some effects of pituitary hormones on target tissues
Hypothalamus
Indirect Control through Releaseof Regulatory Hormones
Direct Releaseof Hormones
Corticotropin-releasinghormone(CRH)
Thyrotropin-releasinghormone
(TRH)
Growthhormone-releasinghormone(GH-RH)
Growthhormone-inhibitinghormone(GH-IH)
Prolactin-releasing
factor(PRF)
Prolactin-inhibitinghormone
(PIH)
Gonadotropin-releasinghormone(GnRH)
Sensorystimulation
Osmoreceptorstimulation
Regulatory hormones are released intothe hypophyseal portal system for delivery
to the anterior lobe of thepituitary gland.
Posterior lobeof pituitary gland
Kidneys
Males: Smoothmuscle in ductusdeferens andprostate gland
Females: Uterinesmooth muscle andmammary glands
Melanocytes (uncertainsignificance in healthyadults)
Ovariesof femaleTestes
of maleMammaryglands
Bone, muscle,other tissues
Thyroidgland
Adrenalglands
Adrenal cortex Anterior lobe ofpituitary gland
ACTH
TSHGH
PRLFSH LH
MSH
OXT
ADH
Liver
Somatomedins
Glucocorticoids(steroid
hormones)
Thyroidhormones
Inhibin Testosterone Estrogen Progesterone Inhibin
Thyroid Gland
• Consists of two lateral lobes connected by a median mass called the isthmus
• Composed of follicles that produce the glycoprotein thyroglobulin
• Colloid (thyroglobulin + iodine) fills the lumen of the follicles and is the precursor of thyroid hormone
• Parafollicular cells produce the hormone calcitonin
Figure 16.8
Thyroid Hormone (TH)
• Actually two related compounds
• T4 (thyroxine); has 2 tyrosine molecules + 4 bound iodine atoms
• T3 (triiodothyronine); has 2 tyrosines + 3 bound iodine atoms
Affects virtually every cell in body
• Major metabolic hormone
• Increases metabolic rate and heat production (calorigenic effect)
• Plays a role in
• Regulation of tissue growth
• Development of skeletal and nervous systems
• Reproductive capabilities
Figure 16.9, step 7
To peripheral tissues
T3
T3
T3
T4
T4
Lysosome
Tyrosines (part of thyroglobulinmolecule)
T4
DIT (T2)Iodine
MIT (T1)
Thyro-globulincolloid
Iodide (I–)
RoughER
Capillary
Colloid
Colloid inlumen offollicle
Thyroid follicle cells
Iodinated tyrosines arelinked together to form T3
and T4.
Iodideis oxidizedto iodine.
Thyroglobulin colloid isendocytosed and combinedwith a lysosome.
Lysosomal enzymes cleaveT4 and T3 from thyroglobulincolloid and hormones diffuseinto bloodstream.
Iodide (I–) is trapped(actively transported in).
Thyroglobulin is synthesized anddischarged into the follicle lumen.
Iodine is attached to tyrosinein colloid, forming DIT and MIT.
Golgiapparatus
1
2
3
4
5
6
7
Transport and Regulation of TH
• T4 and T3 are transported by thyroxine-binding globulins (TBGs)
• Both bind to target receptors, but T3 is ten times more active than T4
• Peripheral tissues convert T4 to T3
Figure 16.7
Hypothalamus
Anterior pituitary
Thyroid gland
Thyroidhormones
TSH
TRH
Target cellsStimulates
Inhibits
• Negative feedback regulation of TH release
• Rising TH levels provide negative feedback inhibition on release of TSH
• Hypothalamic thyrotropin-releasing hormone (TRH) can overcome the negative feedback during pregnancy or exposure to cold
Regulation of TH
Homeostatic Imbalances of TH
Figure 16.10
• Hyposecretion in adults—myxedema; endemic goiter if due to lack of iodine
• Hyposecretion in infants—cretinism
• Hypersecretion—Graves’ disease
• Autoimmune disease: body produces antibodies that activate TH-secreting cells by mimicking TSH
• Exophthalmos
Parathyroid Glands
• Four to eight tiny glands embedded in the posterior aspect of the thyroid
• Contain oxyphil cells (function unknown) and chief cells that secrete parathyroid hormone (PTH) or parathormone
• PTH—most important hormone in Ca2+ homeostasis
Figure 16.11
(b)
Capillary
Chiefcells(secreteparathyroidhormone)Oxyphilcells
Pharynx(posterioraspect)
Thyroidgland
Parathyroidglands
Trachea
Esophagus
(a)
Usually four (up to eight) tiny glands embedded in the posterior aspect of the thyroid
Parathyroid Glands
Osteoclast activityin bone causes Ca2+
and PO43- release
into blood
Hypocalcemia(low blood Ca2+)
PTH release fromparathyroid gland
Ca2+ reabsorptionin kidney tubule
Activation ofvitamin D by kidney
Ca2+ absorptionfrom food in small
intestine
Ca2+ in blood
Initial stimulus
Physiological response
Result
PTH is most important hormone for calcium homeostasis
Increases blood calcium levels 3 ways
Homeostatic Imbalances of PTH
• Hyperparathyroidism due to tumor
• Bones soften and deform
• Elevated Ca2+ depresses the nervous system and contributes to formation of kidney stones
• Hypoparathyroidism following gland trauma or removal
• Results in tetany, respiratory paralysis, and death if untreated
• Cortex
Kidney
• Medulla
Adrenal gland
Capsule
Zonaglomerulosa
Zonafasciculata
Zonareticularis
Adrenalmedulla
(a) Drawing of the histology of the adrenal cortex and a portion of the adrenal medulla
Med
ulla
Cort
ex
• Paired, pyramid-shaped organs atop the kidneys
• Structurally and functionally, they are two glands in one
• Adrenal medulla—nervous tissue; part of the sympathetic nervous system
• Adrenal cortex—three layers of glandular tissue that synthesize and secrete corticosteroids
Adrenal (Suprarenal) Glands
Figure 16.13a
• Cortex
Kidney
• Medulla
Adrenal gland
Capsule
Zonaglomerulosa
Zonafasciculata
Zonareticularis
Adrenalmedulla
(a) Drawing of the histology of the adrenal cortex and a portion of the adrenal medulla
Med
ulla
Cort
ex
Adrenal Cortex
mineralocorticoids
glucocorticoids
sex hormones, or glucocorticoids
Mineralocorticoids
• Regulate electrolytes (primarily Na+ and K+) in ECF
• Importance of Na+: affects ECF volume, blood volume, blood pressure, levels of other ions
• Importance of K+: sets RMP of cells
• Aldosterone is the most potent mineralocorticoid
• Stimulates Na+ reabsorption and water retention by the kidneys; elimination of K+
Mechanisms of Aldosterone Secretion
1. Renin-angiotensin mechanism: decreased blood pressure stimulates kidneys to release renin, triggers formation of angiotensin II, a potent stimulator of aldosterone release
2. Plasma concentration of K+: Increased K+ directly influences the zona glomerulosa cells to release aldosterone
3. ACTH: causes small increases of aldosterone during stress
4. Atrial natriuretic peptide (ANP): inhibits renin and aldosterone secretion, to decrease blood pressure
Figure 16.14
Primary regulators Other factors
Blood volumeand/or blood
pressure
Angiotensin II
Blood pressureand/or blood
volume
K+ in blood
DirectstimulatingeffectRenin
Initiatescascadethatproduces
Kidney
Hypo-thalamus
Heart
CRH
Anteriorpituitary
Zona glomerulosaof adrenal cortex
Enhancedsecretionof aldosterone
Targetskidney tubules
Absorption of Na+ andwater; increased K+ excretion
Blood volumeand/or blood pressure
Inhibitoryeffect
Stress
ACTH Atrial natriureticpeptide (ANP)
The RAAS Song
• Aldosteronism—hypersecretion due to adrenal tumors
• Hypertension and edema due to excessive Na+
• Excretion of K+ leading to abnormal function of neurons and muscle
Glucocorticoids (Cortisol)
• Cortisol (hydrocortisone) is the only significant glucocorticoid in humans
• Released in response to ACTH, patterns of eating and activity, and stress
• Prime metabolic effect is gluconeogenesis—formation of glucose from fats and proteins
• Promotes rises in blood glucose, fatty acids, and amino acids – saves glucose for brain
• Keep blood sugar levels relatively constant
• Maintain blood pressure by increasing the action of vasoconstrictors
Homeostatic Imbalances of Glucocorticoids
• Hypersecretion—Cushing’s syndrome
• Depresses cartilage and bone formation
• Inhibits inflammation
• Depresses the immune system
• Promotes changes in cardiovascular, neural, and gastrointestinal function
• Hyposecretion—Addison’s disease
• Also involves deficits in mineralocorticoids
• Decrease in glucose and Na+ levels
• Weight loss, severe dehydration, and hypotension
Figure 16.15
Gonadocorticoids (Sex Hormones)
• Most are androgens (male sex hormones) that are converted to testosterone in tissue cells or estrogens in females
• May contribute to
• The onset of puberty
• The appearance of secondary sex characteristics
• Sex drive
• Estrogens in postmenopausal women
Adrenal Medulla
• Chromaffin cells secrete epinephrine (80%) and norepinephrine (20%)
• These hormones cause
• Blood vessels to constrict
• Increased HR
• Blood glucose levels to rise
• Blood to be diverted to the brain, heart, and skeletal muscle
• Epinephrine stimulates metabolic activities, bronchial dilation, and blood flow to skeletal muscles and the heart
• Norepinephrine influences peripheral vasoconstriction and blood pressure
Adrenal Medulla
• Hypersecretion
• Hyperglycemia, increased metabolic rate, rapid heartbeat and palpitations, hypertension, intense nervousness, sweating
• Hyposecretion
• Not problematic
• Adrenal catecholamines not essential to life
Figure 16.16
Short-term stress More prolonged stress
Stress
Hypothalamus
CRH (corticotropin-releasing hormone)
Corticotroph cellsof anterior pituitary
To target in blood
Adrenal cortex(secretes steroidhormones)
GlucocorticoidsMineralocorticoids
ACTH
Catecholamines(epinephrine andnorepinephrine)
Short-term stress response
1. Increased heart rate2. Increased blood pressure3. Liver converts glycogen to glucose and releases glucose to blood4. Dilation of bronchioles5. Changes in blood flow patterns leading to decreased digestive system activity and reduced urine output6. Increased metabolic rate
Long-term stress response
1. Retention of sodium and water by kidneys2. Increased blood volume and blood pressure
1. Proteins and fats converted to glucose or broken down for energy2. Increased blood glucose3. Suppression of immune system
Adrenal medulla(secretes amino acid-based hormones)
Preganglionicsympatheticfibers
Spinal cord
Nerve impulses
Pineal Gland
• Small gland hanging from the roof of the third ventricle
• Pinealocytes secrete melatonin, derived from serotonin
• Melatonin may affect
• Timing of sexual maturation and puberty
• Day/night cycles
• Physiological processes that show rhythmic variations (body temperature, sleep, appetite)
Pancreas
• Triangular gland behind the stomach
• Has both exocrine and endocrine cells
• Acinar cells (exocrine) produce an enzyme-rich juice for digestion
• Pancreatic islets (islets of Langerhans) contain endocrine cells
• Alpha () cells produce glucagon (a hyperglycemic hormone)
• Beta () cells produce insulin (a hypoglycemic hormone)
Pancreatic islet
• (Glucagon- producing) cells
• (Insulin- producing) cells
Pancreatic acinarcells (exocrine)
Glucagon and Insulin
• Effects of Glucagon
• Major target is the liver, where it promotes
• Glycogenolysis—breakdown of glycogen to glucose
• Gluconeogenesis—synthesis of glucose from lactic acid and noncarbohydrates
• Release of glucose to the blood
• Effects of insulin
• Lowers blood glucose levels
• Enhances membrane transport of glucose into fat and muscle cells
• Inhibits glycogenolysis and gluconeogenesis
• Participates in neuronal development and learning and memory
Insulin Action on Cells
• Activates a tyrosine kinase enzyme receptor
• Cascade leads to increased glucose uptake and enzymatic activities that
• Catalyze the oxidation of glucose for ATP production
• Polymerize glucose to form glycogen
• Convert glucose to fat (particularly in adipose tissue)
Figure 16.18
Liver
Liver
Tissue cells
Stimulates glucose uptake by cells
StimulatesglycogenformationPancreas
Pancreas
Insulin
Bloodglucosefalls tonormalrange.
Stimulatesglycogenbreakdown
Bloodglucoserises tonormalrange.
Glucagon
Stimulus Bloodglucose level
Stimulus Bloodglucose level
GlycogenGlucose
GlycogenGlucose
Factors That Influence Insulin Release
• Elevated blood glucose levels – primary stimulus
• Rising blood levels of amino acids and fatty acids
• Release of acetylcholine by parasympathetic nerve fibers
• Hormones glucagon, epinephrine, growth hormone, thyroxine, glucocorticoids
• Somatostatin; sympathetic nervous system
Homeostatic Imbalances of Insulin• Diabetes mellitus (DM)
• Due to hyposecretion or hypoactivity of insulin
• Three cardinal signs of DM
• Polyuria—huge urine output
• Polydipsia—excessive thirst
• Polyphagia—excessive hunger and food consumption
• Fats used for cellular fuel lipidemia; if severe ketones (ketone bodies) from fatty acid metabolism ketonuria and ketoacidosis
• Untreated ketoacidosis hyperpnea; disrupted heart activity and O2 transport; depression of nervous system coma and death possible
• Hyperinsulinism:
• Excessive insulin secretion; results in hypoglycemia, disorientation, unconsciousness
Table 16.4
Ovaries and Placenta
• Gonads produce steroid sex hormones
• Ovaries produce estrogens and progesterone
• Estrogen responsible for:
• Maturation of female reproductive organs
• Appearance of female secondary sexual characteristics
• With progesterone causes breast development and cyclic changes in the uterine mucosa
• The placenta secretes estrogens, progesterone, and human chorionic gonadotropin (hCG)
Testes
• Testes produce testosterone that
• Initiates maturation of male reproductive organs
• Causes appearance of male secondary sexual characteristics and sex drive
• Is necessary for normal sperm production
• Maintains reproductive organs in their functional state
Other Hormone-Producing Structures
• Heart
• Atrial natriuretic peptide (ANP) reduces blood pressure, blood volume, and blood Na+ concentration
• Gastrointestinal tract enteroendocrine cells
• Gastrin stimulates release of HCl
• Secretin stimulates liver and pancreas
• Cholecystokinin stimulates pancreas, gallbladder, and hepatopancreatic sphincter
Other Hormone-Producing Structures• Kidneys
• Erythropoietin signals production of red blood cells
• Renin (an enzyme) initiates the renin-angiotensin mechanism
• Skin
• Cholecalciferol, the precursor
of vitamin D
• Adipose tissue
• Leptin is involved in appetite control, and stimulates increased energy expenditure
• Adiponectin – enhances sensitivity to insulin
Other Hormone-Producing Structures• Skeleton (osteoblasts)
• Osteocalcin prods pancreatic beta cells to divide and secrete more insulin, improving glucose handling and reducing body fat
• Thymus
• Thymulin, thymopoietins, and thymosins are involved in normal the development of the T lymphocytes in the immune response