CTR - 9 - Endocrine Flashcards
What is an autocrine? Examples…
Chemicals which expert effects on the same cells which secrete them
Example: growth factors (cytokines, interleukins)
What is a paracrine? Examples…
Locally acting chemicals which affect nearby cells.
Example: histamine, prostaglandins, growth factors, blood coagulation factors
T or F? Cytokines can be endocrine, paracrine or exocrine.
True!
Give an example of a primary lingered, agonist, and antagonist?
At NMJ:
Primary Ligand = acetylcholine
Agonist = nicotine
Antagonist = curare
What is a primary ligand?
Chemical which has a physiological response on the receptor - activates a response from the receptor
What is an agonist?
A chemical which activates a response from that receptor - but introduced (mimics primary ligand)
What is an antagonist
Primary antagonist = physiological role to inhibit receptor
Drug molecule = similar binding entity (mimics primary antagonist)
Define a hormone.
Chemical secreted by glands, travels through blood or lymph over long distances and act by binding to specific receptors on/in target cells to produce a response.
Give some examples of amino acids based hormones.
Thyroxin, calcitonin, insulin, FSH, LH, TSH, glucagon, epinephrine, ACTH
Where are steroid hormones released from? Synthesised from?
Gonads and adrenal cortex. Synthesised from cholesterol
What are the three ways hormones can act on target cells
- Alter channel permeability (acts on pre-existing channels)
- Acts through second messenger system (alters pre-existing protein activity)
- Activate specific genes to cause formation of new proteins
What are eicosonoids? Examples
Biologically active lipids - local, hormone like activity
Leukotrienes
Prostaglandins
What three factors affect the strength of a hormonal response?
1 - blood levels of the hormone (rate of synthesis, release and elimination)
2 - relative number of receptors on target cell
3 - affinity of receptors for hormone
How can receptor numbers be changed?
Up-regulation
- target cells form more receptors (when hormone levels are low
Down-regulation
- target cells lose receptors (when hormone levels are high)
What are the three types of hormone interaction?
Permissiveness
Synergism
Antagonism
What is permissiveness? example
One hormone cannot exert its effects without another hormone being present
Example: thyroid hormone is required for hypothalamic, pituitary and gonadal hormones for sexual development
What is synergism? example
More than one hormone produces the same effects on a target cell, but the combined effect is greater than the sum of individual effects
Example: glucagon/adrenaline/cortisol act together to raise blood glucose
What is antagonism? example
One or more hormones oppose the action of another hormone.
Example: insulin lowers blood glucose, glucagon raises blood glucose
What are the three types of stimuli for hormonal release? What is each? Example.
Humoral stimuli (changing blood levels of ions/nutrients) Example: low blood calcium stimulates PTH
Neural stimuli (nerve fibres stimulate hormone) Example: neural stimulation of adrenal medulla releasing catecholamines
Hormonal stimuli (tropic hormones) Example: hormones from hypothalamus stimulate anterior pituitary
How are hormones removed?
Inactivation - via enzymatic activity
Degradation - (especially by liver)
Excretion (via kidneys)
Why can urine tests be conducted for hormone levels?
Hormones are excreted by the kidney - into urine
What effects can hormones have? (5)
Alter plasma membrane permeability Stimulate protein synthesis (incl enzymes) Activate/deactivate enzymes Induce secretory activities Stimulate mitosis
ACh binds to ________
cholingergic receptors
NE binds to ________
adrenergic receptors
What is muscle tone?
slightly constriction of blood vessels
NE binding to alpha receptors ______
contracts smooth muscle = vasoconstriction
NE binding to beta receptors _______
inhibits smooth muscle contraction = vasodilation (indirectly relaxes muscle)
Beta receptors for muscle tone are more often found near __________
Alpha receptors for muscle tone are more often found near __________
Beta = the heart/vital organs. Alpha = non-essential tissues/organs
