- 1. Prepared By:Merin Babu5th Semester B.Pharm 2010Amrita School
of Pharmacy
2. CLASSIFICATIONThe motor (efferent) portion is dividedinto:
Autonomic Nervous system(ANS) Somatic Nervous System(SNS) 3.
AUTONOMIC NERVOUS SYSTEMThe Autonomic Nervous System is dividedinto
two divisions: Sympathetic Nervous System Parasympathetic Nervous
System 4. (CHOLINERGIC RECEPTORS) 5. CHOLINERGIC RECEPTORS
Cholinergic receptors are thosereceptors on which the
neurotransmitter Acetyl Choline binds toproduce the required
biologicalresponses.. These biological responses
includeconstriction of pupil(miosis),decreased heart rate and force
ofcontraction, increased secretions etc. 6. LOCATION OF ACETYL
CHOLINERECEPTORSAcetylcholine is a key neurotransmitter acting
onwide number of functions and tissues. The threemain locations
are: 7. CLASSIFICATION 8. NICOTINIC
RECEPTORSLOCATION:Neuromuscularjunction, autonomic ganglia,
adrenalmedulla and in brain. 9. CLASSIFICATION 10. NM
RECEPTORSLOCATION:At the skeletal neuro muscular junction(NMJ),
post synapticFUNCTION:contraction of skeletal muscles 11. NM
RECEPTORSMECHANISM:Ligand gated ion channel- opening of cation(Na+)
channel (end plate depolarization. 12. NN RECEPTORSLOCATION:At all
autonomic ganglia and at adrenalmedulla, post
synapticFUNCTION:Transmission of impulse through theautonomic
ganglia and firing of post ganglionicneuronSecretion of
norepinephrine andepinepherine from adrenal medulla. 13. NN
RECEPTORSMECHANISM:Ligand gated ion channel- opening of cation(Na+)
channel (end plate depolarization) 14. MUSCARINIC
RECEPTORSCholinergic transmission (acetylcholine-mediated) that
activates muscarinic receptorsoccurs mainly at autonomic ganglia,
organsinnervated by the parasympathetic division of theautonomic
nervous system and in the centralnervous system. 15. MUSCARINIC
RECEPTORSAll muscarinic receptors are G-protein
coupledreceptors.Studies have identified five subclasses
ofmuscarinic receptors: M1,M2, M3, M4, and M5. 16. CLASSIFICATION
17. LOCATION AND FUNCTIONM1, M4 and M5 receptors: CNS. These
receptors areinvolved in complex CNS responses such as
memory,arousal, attention and analgesia. M1 receptors are alsofound
at gastric parietal cells and autonomic ganglia.M2 receptors:
heart. Activation of M2 receptorslowers conduction velocity at
sinoatrial andatrioventricular nodes, thus lowering heart rate. 18.
LOCATION AND FUNCTION M3 receptors: smooth muscle. Activation of
M3receptors at the smooth muscle level producesresponses on a
variety of organs that include:bronchial tissue, bladder, exocrine
glands, amongothers. 19. Adrenergic receptorsThe prime function of
the adrenergic orsympathetic nervous system is to help the
humanbeing to adjust to stress and prepare body for fightand flight
reactions. When exposed to stress the heart rate and thestroke
volume increases thereby increases thecardiac output. 20.
Adrenergic receptors The blood is shifted from the skin , gut
kidney andglands to the heart, skeletal muscles, brain andlungs as
these organs need more blood duringstress. 21.
CLASSIFICATIONAdrenergic receptors can be classified into :Alpha
Receptors1. Alpha-12. Alpha-2Beta Receptors1. Beta-12. Beta-23.
Beta-3 22. LOCATION:Vascular smooth muscles, gut,
genitourinarysmooth muscle , liver. 23. LOCATION:pancreatic
b-cells, platelets, nerveterminals 24. LOCATION:Heart. 25. BETA-2
RECEPTORS:LOCATION:Vascular smooth muscles, bronchial, gutand
genito urinary.RESPONSE:Relaxation. 26. BETA-3
RECEPTORSLOCATION:Adipose Tissue.RESPONSE:Lipolysis 27. All
muscarinic receptors appear to be G- proteincoupled receptors.In
case of M1,M3 and M5 receptors the binding ofthe muscarinic
receptors activate theinositolphosphate(IP3), diacyl glycerol
(DAG)cascade.DAG helps in the opening of the smooth musclecalcium
channels; IP3 releases calcium fromendoplasmic reticulum and
sarcoplasmic reticulum. 28. Muscarinic activation in some tissues
likeheart, intestine inhibits the adenyl cyclase activity.These
include the receptors present on M2 and M4. These produces the
activation and opening ofpotassium channels.Thereby it inhibits the
neuronal calcium levels.These muscarinic effects on cAMP generation
reducethe physiological response of the organ to
stimulatoryhormone. 29. The neuronal nicotinic receptor consists of
alphaand beta subunits only. Each subunit has four transmembrane
segments. Agonist binding to the receptor sites causes
aconformational change in the protein( channelopening) that allows
Na+ and K+ ions to diffuserapidly down their concentration
gradients ( calciumions may also carry charge through the
nicotinereceptor ion channel).Binding of an agonist molecule by one
of the tworeceptors sites increases the probability of
channelopening ;simultaneously binding of the agonist byboth of the
receptors sites enhances openingprobability. 30. Nicotinic receptor
activation causesdepolarization of the nerve cell or neuro
muscularend plate membrane . In skeletal muscle; the depolarization
propagatesacross the muscle membrane and causescontraction. 31.
Alpha-1 receptors are coupled via G proteins inthe family to
phospholipase C. This enzyme hydrolyses
polyphosphoinositidesleading to the formation of inositol
1,4,5triphosphate (IP3) and diacylglycerol(DAG). IP3 promotes the
release of Ca2+ from theintracellular stores which increases the
cytoplasmicconcentration of free Ca2+ and activation ofvarious
calcium dependent protein kinases. 32. Activation of these
receptors may increase theinflux of Ca2+ across the cells
plasmamembrane.IP3 is sequentially dephosphorylated leads tothe
formation of free inositol. DAG activates protein kinase C,
whichmodulates the activity of signalling pathway. 33. Alpha-2
receptors inhibit adenyl cyclase activityand intracellular cyclic
adenosine monophosphate(cAMP) levels to decrease. Alpha-2 receptor
mediated inhibition of adenylcyclase activity is transduced by the
inhibitoryregulatory protein, G1. Alpha-2 receptor agonists cause
plateletaggregation and decrease in platelet cAMP levels. They use
other signaling pathways includingregulation of ion channel
activities and activities ofimportant enzymes involved in signal
transduction. 34. Activation of all three receptor ( beta-1,beta-2
andbeta-3) results in stimulation of adenyl cyclase andincreased
conversion of ATP to cAMP.cAMP is the major secondary messenger of
beta-receptor activation.Eg: liver, beta receptors activation of
glycogenphsphorylase. heart, beta receptors promotes the
relaxationof smooth muscles. 35. THANK YOU
