Endocrine System Flashcards
Endocrine system acts with nervous system to…
Coordinate and integrate body cells
Endocrine system influences metabolic activities via ___________ transported in blood.
Hormones
Endocrinology
Study of hormones and endocrine organs
Characteristics of the endocrine system:
- Initiates responses slowly
- Long duration responses
- Acts via hormones released into the blood
- Acts at diffuse locations - targets can be
anywhere blood reaches - Hormones act over long distances
Characteristics of the nervous system:
- Neurotransmitters act over very short
distances - Initiate responses rapidly
- Short duration response
- Acts via action potentials and
neurotransmitters - Acts at specific locations determined by axon
pathway
The endocrine system controls and integrates…
- Reproduction
- Growth & development
- Maintenance of electrolyte, water, & nutrient
balance of blood - Regulation of cellular metabolism & energy
balance - Mobilization of body defenses
While exocrine glands produce __________ and ___ have ducts, endocrine glands produce _________ and ____ have ducts.
Exocrine: Non-hormonal substances; DO
Endocrine: Hormones; DONT
What’s the purpose of ducts?
To carry non-hormonal substances to a membrane surface
Examples non-hormonal substances:
Sweat and saliva
List the endocrine organs:
Pituitary, thyroid, parathyroid, adrenal and pineal
Which organ is a neuroendocrine?
Hypothalamus
Which organs have both exocrine and endocrine functions?
Pancreas, gonads, and placenta
Tissues/Organs that produce hormones?
Adipose cells, thymus, and cells in walls of of small intestine, stomach, kidneys & heart
Hormones
- Long-distance chemical signals
- Travel in blood or lymph
Autocrine
Chemicals that exert effects on same cells that secrete them.
Paracrine
Locally acting chemicals that affect cells other than those that secrete them.
Hormones, autocrine, and paracrine are all examples of…
Chemical messengers
Autocrine and paracrine are consider _____ chemical messengers; ____ considered part of endocrine system.
Local; are
The two main classes of hormones are:
Amino acid-based & steroids
Amino-acid-based
Amino acid derivatives, peptides, and proteins
Steroids
Synthesized from cholesterol; gonadal and adrenocortical hormones.
Target cells
Cells that contain receptors for a particular hormone
Hormone action on target cells maybe to:
- Alter plasma membrane permeability, or
membrane potential, or both by
opening/closing ion channels - Stimulates synthesis of enzymes and other
proteins within the cell - Activate/deactivate enzymes
- Induce secretory activity
- Stimulates mitosis
Hormones act in one of two ways, depending on their chemical nature and receptor location. They are…
Water-soluble & lipid-soluble
Water-soluble hormones act on __________, via __________, and ________ enter cell.
Plasma membrane receptors; G protein 2nd messenger; CANNOT
Lipid-soluble hormones act on __________ and _____ enter cell.
Intracellular receptors; CAN
Examples of water-soluble hormones:
All amino acid-based hormones except TH
Examples of lipid-soluble hormones:
TH & steroids
Amino acid-based hormones, except TH, exert effects through…
2nd messenger systems
Two main 2nd-messenger systems:
Cyclic AMP & PIP_2- calcium signaling mechanisms
What’s the 1st step of the cAMP signaling mechanism?
Hormone (1st messenger) binds to receptors
What’s the 2nd step of the cAMP signaling mechanism?
Receptor activates a G protein
What’s the 3rd step of the cAMP signaling mechanism?
G protein activates/inhibits effector enzyme adenylate cyclase
What’s the 4th step of the cAMP signaling mechanism?
Adenylate cyclase converts ATP -> cAMP (2nd messenger)
What’s the final step of the cAMP signaling mechanism?
cAMP activates protein kinases that phosphorylate (add a phosphate) other proteins
After the cAMP signaling mechanism occur, _________ proteins are then either activated/inactivated.
Phosphorylated
cAMP is rapidly degrading by enzyme __________, stopping __________ (Have huge amplification effect).
Phosphodiesterase; cascade
Protein kinases
Enzyme that phosphorylates a protein, resulting in activation/inactivation of the protein.
Activated phospholipase C splits membrane protein, ________, into two 2nd messengers: ___________ & ___________
PIP_2-; DAG; IP_3
Diacylglycerol (DAG)
Activates protein kinases
Inositol triphosphate (IP_3)
Causes CA^2+ release from intracellular storage sites.
__________ act as another 2nd messenger in _____________________
Calcium ions; PIP_2- calcium signaling mechanism.
Ca^2+ alters ____________ and ________, or binds to regulatory protein _________
Enzyme activity; channels; calmodulin
In other signaling mechanisms, ________________, is a 2nd messenger for selected hormones.
Cyclic guanosine monophosphate (cGMP)
Other hormones work without a 2nd messenger system, an example of this can be:
Insulin receptor is a tyrosine kinase enzyme that autophosphorylates upon insulin binding.
___________ provide docking sites for relay proteins that trigger cell responses.
Activated tyrosine kinase
What’s the 1st step of the Direct Gene Activation mechanism.
Lipid-soluble steroid hormones & TH can diffuse into target cells and bind with intracellular receptors
What’s the 2nd step of the Direct Gene Activation mechanism.
Receptor-hormone complex enters nucleus
What’s the 3rd step of the Direct Gene Activation mechanism.
Receptor-hormone complex binds a specific DNA region
What’s the 4th step of the Direct Gene Activation mechanism.
Binding initiates transcription of the gene to mRNA
What’s the 5th step of the Direct Gene Activation mechanism.
The mRNA directs protein synthesis
Blood levels of hormones are controlled by…
Negative feedback system
Negative feedback
Increased hormone effects on target organs can inhibit further hormone release.
Blood levels vary within ________, __________
Narrow; desirable range
Hormone releases are triggered by…
Endocrine gland stimuli & nervous system modulation
Endocrine glands are stimulated to synthesize and release hormones in response to one of three stimuli:
Humoral, neural, & hormonal
Humoral stimuli
Changing blood levels of ions and nutrients directly stimulate secretion of hormones.
________ blood Ca^2+ concentration stimulates parathyroid glands to secrete ____
Declining; PTH
___________ causes Ca^2+ concentrations to rise, and stimulus is removed.
Parathyroid hormone
Neural stimuli
Nerve fibers stimulate hormone release.
Sympathetic nervous system fibers stimulate ___________ to secrete ___________
Adrenal medulla; catecholamines
Hormonal stimuli
Hormones stimulate other endocrine organs to release their hormones.
____________ hormones stimulate release of most anterior pituitary hormones
Hypothalamus
______________ hormones stimulate targets to secrete still more hormones
Anterior pituitary
Hormones from final target organs inhibit release of ___________ hormones
Anterior pituitary
Hypothalamic-pituitary-target
Endocrine organ feedback loop
Nervous system modulation
Nervous system can make adjustments to hormone levels when needed & can override normal endocrine controls.
Example of the nervous system overriding normal endocrine controls:
Under severe stress, hypothalamus and sympathetic nervous system override insulin to allow blood glucose levels to increase (Prepare body for “Fight or Flight”)
Target cell activation depends on three factors:
- Blood levels of hormones
- Relative number of receptors on/in target cell
- Affinity (strength) of binding between receptor
and hormone
Target cell specificity
Target cells must have specific receptors to which hormones bind.
______ receptors are found only on certain cells of adrenal cortex, but _________ receptors are found on nearly all cells of body.
ACTH; thyroxin
Up-regulation
Target cells form more receptors in response to low hormone levels.
Down-regulation
Target cells lose receptors in response to high hormone levels.
What’s the purpose of up/down regulation.
Controls the hormone levels and ensures that its balanced.
Concentration of circulating hormone reflects:
- Rate of release
- Speed at which it is inactivated and removed
from body
Steroids and thyroid hormone are attached to…
Plasma proteins
Hormones can be removed from blood by:
Degrading enzymes, kidneys, or liver.
Half-life
Time required for level of hormone in blood level to decrease by half.
The duration of response is usually limited:
- Ranges from 10 seconds to several hours
- Effects may disappear rapidly as blood levels
drop, but some may persist for hours at low
blood levels
Hormones have different response times, some…
Are immediate, can take hours to days (especially steroids), and are inactive until they enter target cells
________, _____, and __________ are dependent on whether the hormone is water or lipid soluble
Half-life; onset; duration of hormone activity
Characteristics of water-soluble hormones:
- All amino acid-based hormones except TH
- All other endocrine glands
- Stored in secretory vesicles
- Free in plasma when transported
- Half-life shorter in blood
- Mechanism of action at target cell usually act
through 2nd messenger systems - Receptors located on plasma membrane
Characteristics of lipid-soluble hormones:
- All steroid hormones and TH
- Adrenal cortex, gonads and thyroid
- Not stored in secretory vesicles
- Bound to plasma proteins when transported
- Half-life longer in blood
- Mechanism of action at target cell activates
genes causing synthesis of new proteins - Receptors located inside cells
Permissiveness
One hormone cannot exert its effects without another hormone being present.
Synergism
More than one hormone produces same effects on target cell, causing amplification.
Antagonism
One or more hormones oppose(s) action of another hormone.
Example of permissiveness
Reproductive hormones need TH to have effect.
Example of antagonism
Insulin & glucagon
Example of synergism
Glucagon & epinephrine both cause liver to release glucose
Hypothalamus is connected to pituitary gland (_________) via stalk called ______________
Hypophysis; infundibulum
Posterior pituitary
Composed of neural tissue that secretes neurohormones
Posterior lobe, along with infundibulum make up the ____________
Neurohypophysis
Anterior pituitary (adenohypophysis)
Consists of glandular tissue
Posterior lobe is ______ tissue derived from a ____________ of brain.
Neural; downgrowth
Posterior lobe secretes two neurohormones called…
ADH & oxytocin
ADH & oxytocin are stored in _________ in posterior pituitary and are released into blood when ____________
Axon terminals; neurons fire
Posterior lobe maintains neural connection to hypothalamus via ________________
Hypothalamic-hypophyseal tract
Hypothalamic-hypophyseal tract arises from neurons in _____________ and ___________ in hypothalamus.
Paraventricular; supraoptic nuclei
Anterior lobe is ________ tissue derived from an out pocketing of ___________
Glandular; oral mucosa
Vascularly connected to hypothalamus via hypophyseal portal system consisting of:
Primary capillary plexus, hypophyseal portal veins, & secondary capillary plexus
Hypothalamus secretes ___________ hormones to anterior pituitary to regulate hormone secretion
Releasing/inhibiting
Posterior pituitary consists of ____________ of neurons from hypothalamic neurons.
Axon terminals
What are the two hypothalamic neurons:
Paraventricular & supraoptic
__________ produce antidiuretic hormone (ADH)
Supraoptic neuron
____________ produce oxytocin
Paraventricular neuron
What is the similarity and difference between oxytocin and ADH?
Both have 9 amino acids, but differ in 2
What are the functions of oxytocin?
- Strong stimulant of uterine contractions
released during birth - Also acts as hormonal trigger for milk ejection
Oxytocin uses ___________ when it acts as a neurotransmitter in the brain.
PIP_2- calcium 2nd messenger system
Both the functions of oxytocin are ___________ mechanisms
Positive feedback
Hypothalamus contains ___________ that monitor solute concentrations
Osmoreceptors
If solution concentration in the hypothalamus is too high…
Posterior pituitary triggered to secrete ADH
ADH targets kidney tubules to…
Reabsorb more water to inhibit or prevent urine formation
ADH release is triggered by…
Pain, low BP, & drugs
High concentrations can cause ___________, so also called __________
Vasoconstriction; vasopressin
ADH inhibited by…
Alcohol & diuretics
Diabetes insipidus
ADH deficiency due to damage to hypothalamus or posterior pituitary; must be kept hydrated
Syndrome of inappropriate ADH secretion (SIADH)
Retention of fluid, headache, disorientation; fluid restriction; blood sodium level monitoring
List 6 hormones that are considered peptide hormones
Growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin
List 4 hormones that are considered tropic hormones
TSH, ACTH, FSH, LH
All peptide hormones but ________ activate target cells via cAMP 2nd-messenger system
GH
Tropic hormones (tropin)
Hormones that have other endocrine glands as their target.
GH is also know as __________ and is produced by ____________
Somatotropin; somatotropic cells
