Autonomics 2 Flashcards
Primary neurotransmitter of the adrenergic system?
norepinephrine
Are the levels of norepinephrine controlled by positive or negative feedback?
negative feedback
What enzymes are able to breakdown norepinephrine? (2)
- COMT (methylation in the synapse)
- MAO (deamination in the presynaptic neuron)
What adrenergic receptors are part of the sympathetic nervous system?
alpha-1, alpha-2, beta-1, beta-2, beta-3
Which adreneric receptor (AR) is unique and why?
alpha-2 (a2), it is an autoreceptor on the presynaptic neuron
What NTs are secreted from the adrenal medulla and in what ratio?
epinephrine (80%) and norepinephrine (20%)
Can the adrenal medulla make epinephrine?
yes
Two organs that are special cases in sympathetic signalling?
adrenal medulla and sweat glands
Adrenal medulla
Ach release and binds to nicotinic receptors on the adrenal medulla which releases epi and NE into the bloodstream to travel and act on target organs
Sweat Gland Special Case
ACh binds to nicotinic receptors on postganglionic fiber then those release ACh (NOT norepinephrine) and bind to muscarinic receptors on sweat glands
Effect of Sympathetic System on Heart
increase heart rate and blood pressure
Effect of Sympathetic System on Bronchioles
bronchial dilation
Effect of Sympathetic System on Eyes
dilation of pupil by contracting the RADIAL muscles of the iris
Effect of Sympathetic System on Blood Vessels
constricts blood vessels, increase blood pressure
Effect of Sympathetic System on Stomach and Intestines
decrease GI motility by relaxing smooth muscle and contracting the sphincter
Effect of Sympathetic System on Bladder
relax detrusor and contract sphincter
Sympathetic Receptor in the Heart
beta-1 (b1)
Sympathetic Receptor in the Eye
alpha-1 (a1)
Sympathetic Receptor in the Lungs
beta-2 (b2)
Sympathetic Receptor in Stomach and Intestines
beta-2 (b2) (and a1 to constrict the sphincters)
Sympathetic Receptor of the Urinary Detrusor
beta-3 (b3)
Sympathetic Receptor of Urinary Sphincters
alpha-1 (a1)
Sympathetic Receptor of Salivary Glands
alpha-1
Receptor of the Adrenal Medulla
Nicotinic (N)
Main Sympathetic Receptor in Arteries and Veins
alpha-1 (also b2 to a smaller extent, as it is a vasodilator)
Which sympathetic receptors are responsible for contraction/acceleration?
alpha-1 and beta-1 (a1 and b1)
Which sympathetic receptors are responsible for relaxation?
beta-2 and beta-3 (b2 and b3)
Phentolamine
alpha-1 blocker used to reverse epinephrine effetcs (prevents vasoconstriction so b2 takes over)
Sympathomimetic
drugs that partially or completely mimic the actions of epinephrine or norepinephrine
Is epinephrine selective?
no (non-selective)
problem: wanting to iincrease blood pressure in an animal with cardiac disease
Example of an a1 receptor agonist?
Phenylepinephrine
Phenylepinephrine
can increase blood pressure without effects on the heart, not inactivated in the synapse by COMT (longer duration)
Example of a b1 receptor agonist?
Dobutamine
How do alpha-2 receptor agonists work?
activates the presynaptic receptor to decrease release of norepinephrine (negative feedback)
Are alpha-2 receptor agonists sympathetomimetic?
no, because they do not activate adrenergic signals (only inhibitory G proteins)
What type of G protein always activates?
S type
Examples of b2 receptor agonists and their function
terbutaline and albuterol, used for coughing and bronchospasms
Indirect acting sympathomimetics
stimulate release, prevent uptake, or prevent breakdown of norepinephrine
Sympatholytic drug
inhibit the adrenergic signal
