1. Adrenergic drugs act on adrenergic receptors and include catecholamines like dopamine, norepinephrine, and epinephrine that are synthesized in the adrenal medulla and neurons.
2. These drugs stimulate either alpha or beta adrenergic receptors. Alpha receptors cause vasoconstriction and increase blood pressure while beta receptors increase heart rate and force of contraction.
3. The sympathetic nervous system, which these drugs act on, is involved in the "fight or flight" response and increases heart rate, blood flow, respiration, and metabolic rate to prepare the body for emergency situations.
4. According to structue –
1. Compounds with 3,4 dihydroxyphenyl nucleus or catechol nucleus – eg dopamine,
Norepinephrine, epinephrine, Isoprenaline
2. Compounds those lack hydroxy groups on phenyl ring – eg. Amphetamine
Ephedrine
6. Site of biosynthesis of catecholamines - adrenal medulla, adrenergic and dopaminergic
neurons,
1. Biosynthesis
2. Storage
3. Release
4. Termination of action
5. Metabolism – 2 enzymes involved – MAO (monoamine oxidase) – deamination
COMT (catechol O- methyltransferase)
7.
8.
9.
10.
11. TERMS
Mydriatic – dilation of eye pupil
Miotic – constriction of eye pupil
Ionotropic – force of contraction of heart
Chronotropic-rate of contraction of heart
13. The sympathetic system prepares the body to meet
emergency demands and is primarily involved with
processes that expend energy. During physical or
emotional stress, the sympathetic division dominates
the parasympathetic system, initiating a series of
activities known as the fight-or-flight response.
In addition, there is activation of the adrenal medulla,
causing secretion of norepinephrine and epinephrine as
hormones to greatly heighten the response.
Effects Of Sympathetic Nervous System
14. Increase blood supply to cardiac muscle (dilate the coronary
artery)
Raised peripheral resistance and blood pressure by
constricting the small artery the skin. In this way increase
blood supply is available for highly active tissue, such as
skeletal muscle, heart and brain.
Constrict the blood vessel in secretory glands of digestive
system
Accelerates blood coagulation because of
vasoconstriction.
Increasing heart beat
Cardiovascular System
15. Respiratory system
Causes smooth muscle relaxation and therefore
dilatation of the airways, especially bronchioles.
Allowing a greater amount of air to enter the lungs
at each inspiration, and increase the respiratory
rate.
Deal with ’fight and flight’ situation.
16. Digestive and urinary system
Liver increase conversion of glycogen to glucose-
glycogenolysis
Stomach and small intestine; smooth muscle
contraction (peristalsis) and secretion of digestive
juices are inhibited, delaying digestion.
Adrenal gland; stimulated to secrete adrenaline and
noradrenaline which potentiate and sustain the effect of
sympathetic stimulation
Urethral and anal sphincter; muscle tone increase,
inhibit micturition and defecation.
Bladder walls relaxes
Metabolic rate increase
17. Eye
Dilating the pupil
Opening the eyes open wide and giving the
appearance of alertness and excitement
Reduces intraocular pressure so used in treatment
of open angle glucoma
Skin
Increase sweat secretion, leading to increased heat
loss from the body
Constrict the peripheral blood vessel increasing
blood supply available to active organs, e.g heart and
skeletal muscle.
