Endocrine Physiology Flashcards
What is the function of the endocrine system?
Control systems to maintain homeostasis
How is the endocrine system regulated?
Through a feedback system
What is the basis of the sensitivity of the endocrine system?
Amplification of a signal
Amplification of the signal is described as?
A small amount of hormone can produce a major biological effet
T/F can hormones influence the initiation of a new reaction
False- they can only influence the rate of EXISTING reactions
Can an enzyme be present in the absence of the hormone influencing its reaction?
yes, in basal levels
What are the ductless glands that secrete the products into the blood stream directly?
Endocrine glands
The exocrine glands release products into ducts that lead where?
Lumen of other organs
How do paracrine glands act?
By diffusing the chemical message through interstitial fluid to influence adjacent cells
Give an example of an exocrine gland
Mammary gland
salivary gland
sweat glands
Histamine and Cytokines are chemical messengers associated with which glands?
Paracrine glands
The __________ effect is when a messenger acts on the cell of its own origin to produce an effect on itself.
Autocrine
An example of a substance with an autocrine effect is:
Insulin-Like Growth Factor
Which hormone has a paracrine and an autocrine effect?
Growth hormone
T/F many cell types in endocrine gland tissues can make hormones
False, only one cell type will make the hormones
What is the exception of an endocrine gland that only secretes one hormone?
Parathyroid gland
What body system interacts with the endocrine system to produce the physiological effect?
Nervous system
Neurohormones are derived from?
Nerve cells
The chemical messengers released from the synapse between the nerve and the effector cell is the _____________
Neurotransmitter
List some major endocrine glands
- HT
- Pituitary
- Thyroid
- Parathyroid
- Thymus
- Adrenal
- Pancreas
- Gonads
- Pineal
Define hormone
Chemicals produced by endocrine organs transported by the vascular system to produce an effect on another tissue
Hormones exist in a biological ____________ state
Active
List the 3 classification of hormones based on composition
- Protein
- Steroids
- Gaseous
Protein hormones are subdivided into ___________ and __________
Peptide and Amino acid derivatives
Dopamine, melatonin and epinephrine are ______________ protein hormones (subdivision)
Amino acid
List the classification of hormones based on solubility
Water soluble and Lipid soluble
Which type of soluble hormones are the catecholamines (protein hormones)? An example are Epi and NE
Water soluble hormones
Lipid-soluble hormones, like _______________ and ___________, will go into the cells since their receptor can be in the cytoplasm or in the nucleus
Steroid hormones and Thyroid hormone
Prehormones are protein hormones synthesized in which part of the cells?
Ribosomes
Prohormones are when the prehormones go through what?
Cleavage by the rER
Where do prohormones go to form active hormones?
Golgi apparatus
Where are steroid hormones synthesized?
LIver
T/F Steroid hormones are stored before being released.
False, they are released as they are synthesized
What two ways are hormones released?
Regulated and contstituive
Which type of secretion are protein hormones released?
Regulated - released in bursts when stimulated
When the cell does not store hormones and they are secreted through secretory vesicles it is ______________ secretion.
Constitutive
Which hormone is the ecxeption to the secretion rule?
Thyroid hormone
Why are the (protein) thyroid hormones the exception to the secretion type rule?
Their receptors are intracellular (in nucleus)
Steroid hormones are made from which 2 tissues:
Gonads and adrenal glands
Androgens, estrogen and progestins are example of which type of steroid hormones?
Sex steroids
Mineralcorticoids and Glucocorticoids are made in the ______________
adrenal glands
Give an example of a mineralcorticoid:
Aldosterone
Steroid hormones are derived from what substance?
Cholesterol
What type of enzymes are required for the biosynthesis of steroid hormones?
Oxidative enzymes
What is the 1st limiting step in the synthesis of steroid hormones?
Conversion of cholesterol to pregnenolone
T/F Pregnenolone is a hormone
False
CYP11A1 is the enzyme that converts cholesterol into pregnenolone where in the cell?
Mitochondria
What type of solubility do steroid hormones are classified as?
Lipid-soluble
Where do steroid hormones bind in low affinity for transport ?
Plasma proteins
How are steroid hormones eliminated?
By inactivating metabolic transformations or through excretion
Peptide hormones are (hydrophilic/hydrophobid)
hydrophilic
Where are the receptors for protein hormones?
In the cell surface
Which type of hormone has a shorter half life?
Peptide hormones
Which feedback system most commonly controls hormone secretion?
Negative
What is the controlled variable of hormone control?
Degree of activity of the target tissue
Synthesis, processing, and releasing of hormones require which two steps of the nuclear gene code?
Gene transcription and translation
Which hormones are an example of a positive feedback mechanism?
LH and Oxytocin
Cyclic variations of hormone secretion can be regulated by which factors?
- season
- stage of development
- aging
- day cycle
- sleep
How are water-soluble hormones transported?
Dissolved in plasma
Steroid and Thyroid hormones are transported how?
Bound to plasma proteins and biologically inactive
Define a hormone-receptor interaction
protein binds a ligand with high affinity but low capacity
How can a tissue be a target for a hormone?
It expresses the specific receptor for it
What defines the hormone-receptor interaction?
Equilibrium constant “Kd”; Dissociation
List where hormone receptors can be found
- cell membrane
- cytoplasm
- nucleus
T/F the number of hormone receptors remains constant
False
Water-soluble hormone receptors are found in:
Cell membrane surface
Lipid-soluble receptors are found in:
Nucleus or cytoplasm
Which type of receptors are usually coupled with second messenger systems?
Water-soluble
What is the 1st step of a hormone action?
Binding to the receptor
A molecule that binds the receptor and induces the cascade of reactions is an _______________
agonist
The molecule that binds to the receptor and BLOCKS the binding of the agonist without triggering the intracellular signaling events is the:
antagonist
Describe how receptor occupancy is associated with the maximum biological response
The response can be achieved with an average of <3% occupancy
If the cell has more receptors, is it more or less sensitive to the hormone?
More sensitive
The hormone response element is when a receptor complex (promoter) binds to what?
Sequence of DNA to initiate gene transcription and mRNA formation
Intracellular signaling occurs with the formation of a?
Hormone-receptor complex
Are the lipid-soluble hormone responses usually slow or fast?
slow, because they require gene transcription to evoke a response
What can limit the metabolism of a hormone?
Hormone activity
Metabolic degradation of a hormone occurs via an ______________ process, such as proteolysis, oxidation, reduction, etc.
enzymatic
The liver metabolizes which type of hormones through reduction?
Steroid hormones
Metabolism of _____________ hormones through the removal of iodine molecules.
Thyroid
Hormones that conjugate to water-soluble molecules can yield what substances?
Glucoronides and sulfates
What cleaves protein hormones?
Peptidases
How are hormones measured?
- bioassays
- Chemical methods
- Immunoassays
What can be the causes of endocrine disorders?
- hormone deficiency, excess, or resistance
Which hormone deficiency does NOT cause disease?
Calcitonin deficiency
T/F a hormone excess may be due to a non-endocrine tissue secreting the hormone
true
