Endocrine Flashcards
Indicate important differences between hormonal and neural controls of body functioning.
Neural control of the body is a very fast electrical or chemical signal that last for a short
period of time.
Generally, one neuron only controls a few cells , with strength depending on
the number of action potentials .
Endocrine control of the body is a slow chemical signal that can last as long as
hormone levels remain in the body .
Hormones can control organs or parts of the body,
with
strength of response depending on the amount of hormone released
compare the 3 classes of hormones peptides , steroids , and
amino acid derivatives) according to how they are synthesized ,
stored ,
released ,
and transported , along with their mechanism of action .
peptide hormones are short chains of amino acids that are synthesized in advance and stored in secretory
vesicles .Upon stimulation of the tell , peptide hormones are released by exocytosis , and can be freely transported
in the plasma because they are monomers of proteins .
When they reach their target cell , peptide hormones bind to
membrane receptors and activate the second messenger systems.
Steroid hormones are derivatives of cholesterol la tipid) that are synthesized as needed .
They cannot be stored due to
being lipophilic ,
but when the cell is stimulated , are released by simple diffusion .
Steroid hormones must be transported in
the blood bound to plasma proteins .
When they reach target cells , these hormones easily cross the membrane and bind to
either cytoplasmic or nuclear receptors to alter gene transcription.
amino acid derived hormones are 1 or 2 A- As that act as hormones . The 2 main Ats these hormones come from are
tyrosine and tryptophan.
Tyrosinederived hormones include thyroid hormones , which are synthesized in advance
* bind to nuclear receptors only
and stored in vesicles ,
but are released ,
transported ,
and act as steroid hormones. Catheadamies are also tyrosine
derived and are synthesized ,
stored , released , and transported like peptide hormones.
Tryptophan -
derived hormones
also are synthesized ,
stored , released , and transported like peptide hormones.
Describe the relationship between hypothalamus and the
pituitary gland
The pituitary gland is directly connected to the hypothalamus by the hypophyseal stalk.
some cell bodies where hormones are created are in the hypothalamus while their axons project
into the pituitary gland . Hormones created in the hypothalamus can stimulate or inhibit
pituitary hormones .
The hypophyseal portal system allows hypothalamic hormones to travel directly to the
pituitary w/o circulating the blood stream
Compare the anterior and posterior pituitary
the anterior pituitary is made of glandular tissue and synthesizes hormones to be released in response to
secretion of hypothalamus hormones.the posterior pituitary is made of nervous tissue . It does not synthesize
hormones ,but stores hypothalamic hormones until their stimulated release by an Action potential
Hypothalamic hormones released from the posterior pituitary:
ADH /Vasopressin :
elevate blood pressure by retaining fluid
oxytocin :
milk ejection in breastfeeding female
Hypothalamic hormones released from the anterior pituitary:
corticotropin releasing hormone (CRH) :
stimulates release of ACTH from anterior Pituitary
growth hormone releasing hormone (GHRH):
stimulates release of GH from anterior Pituitary
growth hormone inhibiting hormone (GHIH) :
inhibits release of GH
gonadotropin hormone
releasing hormone (GnRH): stimulates release of gonadotropin hormones
LH and FSH from anterior Pituitary
thyrotropin releasing hormone (TRH): stimulates release of TSH and / or prolactic from Anterior Pituitary
dopamine : inhibits release of prolactin from anterior pituitary
Describe the reflex pathway of oxytocin and ADH, explaining
the mechanisms that control their release ,
their target organ
responses , and their cellular mechanisms of Action.
ADH is stimulated by 10W systemic blood pressure .
It is target to the kidney tubule to signal for an
increased retention of water to elevated the blood pressure . Normal BP inhibits ADH.
Oxytocin ,
a peptide hormone, is stimulated to release in response to baby suckling on breast. They target the smooth muscle in the breast , and bind to membrane receptors that activate the GCPR-PLC pathway that signal for the milk to eject
List the hormones secreted by the anterior pituitary and
give their functions + reflex pathways
adrenocorticotropic hormone (ACTH) :
stimulated to release by CRH and targets the adrenal
medulla . Works directly to affect metabolism (Stress)
Follicle Stimulating Hormone (FSH) stimulated to release by GnRH + targets gonads. useful in reproductive.
growth hormone (GH) /somatotropin : stimulated to release by GHRH and inhibited by GHIH,
targeting the liver and other organs.at stimulates glucose
conservation and bone growth .
thyroid stimulating hormone (TSH):
stimulated to release by TRH ,
targeting the thyroid gland , TSH
stimulates the thyroid to produce T3 and T4
prolactin :
stimulated directly by the hypothalamus .prolactin targets the breast tissue to stimulate
milk production.
Prolactin is inhibited by dopamine.
Describe growth hormone secretion patterns, how GH is transported ,
where receptors are ,
how it creates a cellular response , and
its metabolic effects.
Growth hormone (GH) is secreted through exocytosis in response to GHRH and travels thru the blood freely in the plasma . It has receptors in the liver that when bound , release IGF -1 . IGF - 1 targets
almost all tissues to stimulate growth and energy conservation .
Describe the anatomy of the thyroid gland and identify the
hormones secreted by the distinct cell types
The thyroid is a butterfly -
shaped gland composed of follicular cells that secrete T3
and T4 , surrounding an open follicle. Parafollicular c-cells surround the follicular cells and
produce calcitonin.
Identify the process and control factors of thyroid hormone
biosynthesis and storage
Na+K+ ATPase creates a concentration gradient for Na+ to enter paired with I- on the basolateral membrane of the follicular cell. I- then exits
on the apical side using a CI- I - exchanger. I - + I - = I3 which pairs with thyroglobulin precursor that contains tyrosine packaged by the Golgi .
To attached to newly made DIT, MIT, T3 , T4 enters into a colloid droplet through pinocytosis , cleaves off MIT + DIT and T3,T4 is secreted out into a capillary
Describe secretion of thyroid hormones , how they are transported,
where receptors are ,
how a cellular response is created ,
and
metabolite effects .
Thyroid hormone T4 is made in advance and stored in vesicles . When stimulated to release , T4 →T3 and is released by exocytosis .
Thyroid hormones travel in blood bound to TBG , with receptors all
throughout the body. This causes increase of Na+ K+ ATPase activity by producing more of the enzyme . This causes increased
metabolism and O2 use .
Neural Control
Long distance
Electrical and Chemical
Very fast
Usually short acting
Each neuron targets one/few cells
All APs same; stronger signal indicated by increased frequency
Endocrine Control
Long distance
Chemical
Slower
Responses longer lasting
Hormones go throughout entire body
Stronger stimulus indicated by more hormone
Autocrine signal
Acts on cell that secreted it
Paracrine signal
Acts on cells in vicinity of cell that secreted it
Endocrine signal
Travels through the blood to a distant target, where it has an effect at very low concentrations
hormone
a chemical signal used in the body at low concentration.
Target cell
the destination of the hormone
receptor
a protein on or in the cell in which the hormone can bind to
Hormone Classes
Peptide
Steroid
Amino acid-derived
Peptide Hormones
Synthesized in advance and stored in secretory vesicles
Released by exocytosis
Freely dissolve in plasma
Short half life
Bind to membrane receptors
Activate 2nd messenger systems/gene transcription
Steroid Hormones
Synthesized when needed; not stored
Released by diffusion
Bind to plasma proteins for blood transport
Longer half life
Bind to intracellular receptors
Activate gene transcription
Amino Acid Derived - (Tyrosine derived) Thyroid hormone
Properties same as steroid hormone except:
Precursor is made in advance and stored in vesicles
Binds to nuclear receptors
Amino Acid Derived - (Tyrosine derived) Catecholamines
Properties same as peptide hormone
Examples
Dopamine
Epinephrine
Norepinephrine
Tryptophan-derived
Melatonin
Properties like peptide hormones
Anterior Pituitary
Glandular tissue
Synthesizes and releases hormones in response to hypothalamic hormones
Posterior Pituitary
Nervous tissue
Stores hormones synthesized in hypothalamus & releases them in response to APs
Hypothalamic Hormones
Synthesized in hypothalamus but stored in/released from posterior pituitary
Synthesized in hypothalamus and released into hypophyseal portal system
Hypothalamic Hormones
Posterior Pituitary
Synthesized in hypothalamus but stored in/released from posterior pituitary
ADH
Oxytocin
Antidiuretic Hormone (ADH)
Class: peptide hormone
Stimulus for release: decreased blood pressure
Half-life: ~15 minutes
Target cells: kidney tubule
Receptor: GPCR (cAMP pathway)
Response at target: increased water reabsorption by kidney
Organismal response: increased blood pressure
Oxytocin
Class: peptide hormone
Stimulus for release (in nursing women):
baby suckling (signal to hypothalamus)
Half-life: ~4 minutes
Target cells: smooth muscle cells of breast ducts
Receptor: GPCR (PLC pathway)
Response: milk ejection
Hypothalamic Hormones
Anterior Pituitary
Synthesized in hypothalamus and released into hypophyseal portal system to control release of anterior pituitary hormones
CRH
Dopamine
GHIH/Somatostatin
GHRH
GnRH
TRH
All are peptide hormones
except dopamine
Adrenocorticotropic Hormone (ACTH)
Stimulus from hypothalamus: CRH
Cells secreted by: corticotropes
Target: Adrenal cortex
Follicle Stimulating Hormone (FSH)/ Luteinizing Hormone (LH)
Stimulus from hypothalamus: GnRH
Cells secreted by: gonadotropes
Target: gonads
Growth Hormone (GH)/
Somatotropin
Tonic release
Stimulus from hypothalamus: GHRH
Inhibition from hypothalamus: GHIH
Cells secreted by: somatotropes
Transport in blood: free and bound to protein
Half life: 18 minutes
Target: Liver (and many other cells)
Receptor: tyrosine kinase receptor
Action at target:
Liver- produces IGF-1 that goes to bones and other organs to increase growth and function
Adipose – lipolysis
Muscles – increases protein synthesis
Overall – conserves glucose
Organismal response: Growth, especially of bones
Use of lipids for energy
Thyroid Stimulating Hormone (TSH)
/Thyrotropin
Stimulus from hypothalamus: TRH
Cells secreted by: thyrotropes
Target: Thyroid gland
Receptor: GPCR (cAMP)
Action at target: produce TH
Prolactin
Regulation from hypothalamus: dopamine inhibits
Cells secreted by: lactotropes
Target: breast tissue
Action at target: milk production
Hormonal Imbalances
Too much hormone being produced
Too little hormone being produced
Receptor problems
Decreased number
Decreased sensitivity
Genetic disorder that leads to non-functional protein
Hormonal Disorders
Primary disorders
Problem with end organ function
Secondary disorders
Problem with organ higher up in pathway
Growth Hormone Metabolic Effects
Liver- produces IGF-1 that goes to bones and other organs to increase growth and function
Adipose – lipolysis
Muscles – increases protein synthesis
Overall – conserves glucose
Liver
produces IGF-1 that goes to bones and other organs to increase growth and function
Adipose
lipolysis
Muscles
increases protein synthesis
Overall
conserves glucose
Too little GH
In children: dwarfism
Too much GH
In children: gigantism
In adults: acromegaly
Thyroid Gland & Hormones
C-cells
Calcitonin
Cuboidal epithelial cells (follicular cells)
Thyroid hormone
T3-triiodothyronine
T4-thyroxine
Thyroid Hormone
Secretion and Action
Class: amino acid-derived (tyrosine)
Stimulus for release: released tonically; TSH
Transport in blood: most bound to TBG (thyroxine binding globulin)
Half-life: T3 – 1 day; T4 – 1 week
Target cells: throughout body
Receptor: TR (nuclear receptor)
Response at target: increase Na+/K+-ATPase activity by producing more of the enzyme
Organismal response: increased metabolism and oxygen use
Feedback: T3 and T4 have negative feedback on hypothalamus and anterior pituitary
Hypothyroidism (myxedema)
Iodine deficiency
Idiopathic
Congenital leads to cretinism
Hyperthyroidism
Graves’ Disease (production of TSIs)
Toxic goiter (production of TH)
Thyroid adenoma (production of TH)
