Chapter 16 part 1) Endocrine system

Question 1

Endocrine System Overview

Answer 1

• Acts with nervous system to coordinate and integrate activity of body cells.
  
  • Influences metabolic (cell) activities via hormones in blood
  • Produces a slower but longer lasting effect than the nervous system
• Endorcrinology) study of hormones and endocrine organs.
• Controls and Regulates
  
  • Reproduction
  • Growth and Development
  • Mantienace of electrolyte, water, and nutrient balance in the blood.
  • Regulation of cellular metabolism and energy balance
  • Mobilization of body defenses.

Question 2

Endocrine vs Exocrine glands

Answer 2

• Exocrine Glands
  
  • produce nonhormonal substances (slaiva, sweat)
  • Secrete on membrane suface (ex; skin, tounge)
• Endocrine Glands
  
  • Produce horomones
  • Lack ducts; secrete horomones into surrounding tissue.

Question 3

Endocrine Glands (types)

Answer 3

• Pituitary, thyroid, parathyroid, adrenal, and pineal glands are all endocrine glands
• Hypothalamus) Nueroendocrine organ
  
  • has both nural and endocrine functions
• Pancreas, Gonads, and Placenta
  
  • have exocrine and endocrine functions
• Adipose cells, thymus, cells in small intestine, stomach, kidneys and heat
  
  • all produce horomones

Question 4

Chemical Messangers

Answer 4

• Horomones) Long distance chemical signals
  
  • travel in blood or lymph
• Autocrines) Exert effects on same cells that release them
• Paracrines) Locally acting chemicals that affect cells that surround the secreating cell.
  
  • Autocrines and Paracrines are local chemical messangers that are not considered part of the endocrine system.

Question 5

Chemisty of a Horomone

Answer 5

Two Types

• Amino acid-based hormones
  
  • Amino acid derivatives, peptides, and proteins
  • Cannot pass through plasma membrane
• Steriods
  
  • Synthesized from cholesteral
  • Gonaldal and adrenocortical hormones
  • can pass trhorugh plasma membrane
• Target Cells) Tissues with reponsers for a specific hormone
  
  • Hormones circulate systemically but only target cells are affected.
• Horomone action on Target cells may be to
  
  • Alter plasma membrane permiability/ ion channels
  • Stimulate synthesis or enymes/ protiens
  • Activate/ deactivate enzymes
  • induce secretory activity
  • stimulate mitosis

Question 6

Mechanisms of Hormone Action

Answer 6

• Water-siluable hormones (all amino acid-based hormones except thyroid hormones)
  
  • Act on plasma membrane receptors
  • Act via G protien second messangers (do not enter cell)
• Lipid-Soluable hormones (steriod and thyroid hormones)
  
  • Act on intracellular receptors that directly activate genes
  • can enter the cell

Question 7

Cyclic AMP (second messanger system)

Answer 7

• cAMP signiling mechanism
  
  1. Hormone (first messanger) binds to receptor
  2. Receptor activates a G protien
  3. G protien activates/ inhibits adenylate cyclase
  4. Adenylate Cyclase Converts ATP to cAMP (secnd messanger)
  5. cAMP activated protien kinases that phosphorylaye protiens (add a phospate too)
• Phosphorylation activates some protiens and inhibits other
  
  • can affect a variety of proesses in the target cell
• cAMP is rapidly degraded by enzyme phosphodiesterase
• Cascaded have amplification effect.

Question 8

PIP2- calcium signaling mechanism (second messanger system)

Answer 8

• PIP2-calcium signaling mechanism
  
  1. Hormone-activated G protien releases phospholipase C
  2. Phospholipase C splits membrane protein called PIP2 (Phosphatidyle Inositol Biphosphate) into two second messangers
     
     • Diaclyglycerol (DAG) activated protien kinases
     • Inositol Triposphate (IP3) causes Ca2+ release from intracelluar stores. Ca2+ acts as another messanger
  3. Ca2+ release alters enzyme activity and channles, or binds to regulatory protien calmodulin.
     
     • Calcium boynd calmodulin always amplifys cellular response.

Question 9

Other Signaling Mechanisms

Answer 9

• Cycilic guanosine monophospate (cGMP) is a second messanger for some homones.
• Some work without second messagers
  
  • Ex) Insulin

Question 10

Intracellular Receptors and Direct Gene Activation

Answer 10

• Steroid hormones and thyroid hormone can diffuse into target cells and bind with intracellular receptors
• Receptor-hormone complex enters nucleus and bind to specific region of DNA
  
  • Help initiate DNA transcription to produce mRNA
  • mRNA is then translated into specific protein
    
    • Proteins synthesized have various functions
    • Examples: metabolic activities, structural purposes, or exported from cell

Question 11

Control of hormone release

Answer 11

• Hormone levels in the blood are controlled by negative feeback systems
  
  • Increased hormone effect on target organs can cause decreased hormone release.
  • Levels stay withing a narrow, desirable range
• Endocrine glands stimulated to syntesise and release hormones in response to
  
  • Humoral Stimuli) Changling levels of ions and nutrients
    
    • ex) more Ca2+ in blood stimulates parathyroid hormone
  • Nural stimili) Nerve fibers stimulare hormone release
    
    • ex) sympathetic nervous system activating
  • Horomonal Stimuli) Hormones stimulate other endocrine organs to release their hormones

Question 12

Nervous System modulation

Answer 12

• Nervous system can make adjuctments to hormone levels when needed
  
  • Can modify stimulation or inhibitionof endocrine glands
• The nervous system can overide normal endocrine system functioning
  
  • EX) hypothalamus and sympathetic nervous system overide insulin to allow blood glucose levels to raise in “fight or Flight”

Question 13

Terget Cell Specificty

Answer 13

• Target cells must have specific receptors for the hormone to bind to
• Target cell regulation depends on three facotrs
  
  • Blood levels of hormone
  • Relative number of receptors
  • Affinity of bining between recptor and hormone.
• Ammount of hormone can influence the number of receptors for that hormone
  
  • Up-regulation) more target cells in response to low hormone levels
  • Down-regulation) target cells lose receptors in response to high hormone levels.

Question 14

Hormones in the Blood

Answer 14

• Hormones circulate in blood either free or bound
  
  • Steroids and Thyroid homone are attached to plasma membrnes
  • all others are free
• Concentration of circulating hrormones relates
  
  • rate of release
  • speed of removal in the body
• Hormones can be removed from the blood by
  
  • Degrading Enzymes, kindeys, or the liver
  • Half-life. Time required for hormone’s blood level to decrease in half. (half a minuite to a week)
• Onset of Hormonse activities
  
  • hormones take diffrent times to activate a receptor
  • Duration of a response is usually limited

Question 15

Interations of Hormones at Target Cells

Answer 15

• Permissivensess) one hormone cannot exert its effct without another hormone present
  
  • Reproducive and thyroid hormone are nessecary for the timly development of reproductive structures.
• Synergism) more than onre hormone produces the same effect on a target cell
  
  • causes amplification
  • ex) glucagon and epinephrine both cause liver to release glucose
• Antoganism) One or more homrones apposed the action of another hormone
  
  • EX) Example: insulin, and glucagon: Insulin lowers blood glucose levels, is antagonized by glucagon, which raises blood glucose levels.

Question 16

The Hypothalamus and Pityitary Gland

Answer 16

• Hypothalamus is connected to pituitary gland via a stalk called the indundibulum
  
  • Petuitary gland secretes at least 8 major hormones
• Pituitary gland (hypophysis) seated in the sella turcica of the sphenoid bone. It is the size and shape of a pea
• Two major pituitary gland lobes
  
  • Posterior Pituitary) Composed of a nueral tissue that secreted nuerohoromones
  • Anterior Pituitary) Consists of glandualr tissue.

Question 17

Posterior Pitutary (lobe)

Answer 17

• Mantians nueral connection to hypothalamus via hypothalamic-hypophyseal tract
  
  • Tract arises from neurons in paraventricular and supraoptic nuclei in hypothalamus
  • Runs through infundibulum
• Secrets the hormones
  
  • Oxytocin and Antidiuretic hormone (ADH)
• Can store hormones

Question 18

Anterior Pituitary (Lobe)

Answer 18

• Vascular conection between anterior lobe and hypothalamus
• Hypophesal Portal system componants
  
  • Primary capillary plexus
  • Hypophesal Portal Veins
  • Secondary Capillary Plexus
  • Does not have a nerve system to stimulate, recihormones hormones from hypothalamus

Question 19

Oxytocin

Answer 19

• Strong stimulant of uterine contractions during childbirth
  
  • also acts as a hormonal trigger for milk ejection
  • “Cuddle” hormone
  • both are positive feeback mchanisms
• Released from hypothalamus and is stroed in posterior pituitary

Question 20

ADH (Antidiuretic Hormone) (Vasopressin)

Answer 20

• ADH is released when osmoreceptors detect too much solute
  
  • targets kidney tubukes to absorb more water
  • Inhibited by alchol and other diuretics
• Under certain conditions, such as sever blood loss, exceptionally large amount of ADH are released, causing vasoconstriction and raising blood pressure.

Question 21

Diabetes Inspidus

Answer 21

• Defined by a huge uric output, ADH defficency due to damage to hypothalamus or posterior pituitary
  
  • Urine is large water content
  • person must stay well hydrated

Question 22

Syndrome of inappropriate ADH secretion (SIADH)

Answer 22

• Hypersecretion of ADH
  
  • retention of fluid, headache, disorentation
  • Managment required fluid restriction and blood sodium monitering

Question 23

Anterior Pituirary Hormones

Answer 23

• All 6 are peptide hormones
• All (except GH) activate cells via cAMP messaging
• All (but two) are tropins that regulate secretion of other hormones
  
  • TSH, ACTH, FSH, and LH

Question 24

Growth Hormone

Answer 24

• Produced by Sommatotropic cells
• Direct Actions on Meatabolism
  
  • Increases blood levels of fatty acids for use as fuel
  • Increases amino acid uptake for protein synthesis(increases protein synthesis)
  • Decreases rate of glucose uptake and metabolism
  • (conserving glucose, anti-insulin effect)
  • In liver, it encourages the glycogen breakdown and glucose release to blood (anti-insulin effect)
• Indirect Actions on Growth)
  
  • Mediated growth with insulin-like growth factors (IGFs)
  • GH triggers liver, skeletal muscle, and bone to produce IGF
  • IGF stimilates growth.
• Regulation of Growth Hormone
  
  • Growth horomone-releasing hormone (GHRH)
    
    • Stimulated GR release, triggered by low blood GH/ glucose or high amino acid levels
  • Growth Hormone -Inhibibiting Hormone (GHIH)
    
    • Ihibits GR rlease due to increased GR or IGF
  • Ghrelin) hunger hormone that stimulated GH release.

Question 25

homeostatic Imbalances of Growth Horomone

Answer 25

* Hypersecretion of GH is usually caused by anterior pituitary tumor * In children results in gigantism, Can reach heights of 8 feet (2.4m), but has relatively normal body proportions. * In adults results in acromegaly (=enlarged extremities), Overgrowth of hands, feet, and face * Hyposecretion of GH * In children results in pituitary dwarfism, May reach height of only 4 feet (1.2 m), have fairly normal body proportions * In adults usually causes no problems

Question 26

Thyroid-Stiumulating Hormone (TSH) (Thyrotropin)

Answer 26

* produced by thyrtropic cells of anterior pituitary * Stimulates normal development and secretory activity of the thyroid * Release triggered by thyrotropin-releasing hormone (TRH) from hypothalamus * Inhibited by rising blood levels of thyroid hormones

Question 27

Adrenocorticotropic Hormone (ACTH) (Corticotripin)

Answer 27

* Secretetd by corticotropic cells * ACTH stimulated adrenal cortex to release corticosterioids * Regulation of ACTH release * Triggered by hypothalamic corticptroponin-releasing hormone (CRH) in daily rhythm * Highest levels in the morning

Question 28

Gonadotropins

Answer 28

* Both Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH) are refered to as gonadotropins. * Secreted by gonadotropic cells of anterior pituitary * FSH) stimulated production of gametes * egg or sperm * LH promotes production of gonadal hormones (testosterone/ estrogen) * absent from prepubesent children * Regulation of Gonadotoppin release *

Question 29

Prolactin (PRL)

Answer 29

* Secreted by prolactin cells of anterior pituitary gland * Stimulates milk production in females * role not understood in males * Regulation of PRL primarily controlled by prolactin- inhibiting hormone (PIH), which is Dopamine * PIH prevents release of PRL until needed * decreasing levels lead to lactation * Increased Estrogen levels stimulate PRL * Reason behind breast swelling and tenderness just before the menstrual cycle (but PRL is so brief, the breast do not produce milk) * Blood levels rise toward the end of pregnancy

Question 30

Hyperprolactinemia

Answer 30

* Clinical signs include inappropriate lactation, lack of menses, infertility in females, and impotence in males * most common abnormality of anterior pituitary tumors.