ANS: A pharmaceutical perspective Flashcards
What are the different responses to the changes in the environment?
Rapid- voluntary- somatic nervous system acts on skeletal muscle
- involuntary- ANS acts on the cardiovascular system and other organs ( ANS is the collection and interaction between neuronal groups and fibre connections that control the activity of the heart, visceral organs, blood vessels and glands)
Slow- hormones, NTs, growth factors, cytokines and other factors that cause changes in the gene expression leading to long term adaptation
Nervous System—>
Peripheral nervous system:
a) somatic motor nerve fibres- skeletal
b) autonomic efferent nerve effectors- sympathetic NS/parasympathetic NS/Eneteric NS
Parasympathetic NS
Mainly for digestion, excretion, visual accommodation
Promotes couch potato state
less widespread innervation and effects
decrease HR increase in peristalsis increase in GI and other secretion micturition defaecation
Sympathetic NS
important for ongoing control for CV system and reflex responses to stressful situations
“fright, flight, fight”
more widespread innervation and effects
increase HR and force of contraction sweating bronchodilation increase in blood glucose and free fatty acids pupil dilation
Types of efferent nerve pathways
1) Parasympathetic
2) Sympathetic I
3) Sympathetic II
Parasympathetic
eg Salivary Gland
ACh- preganglionic
Nicotonic receptors
ACh- postganglionic
Muscarinic receptors
Sympathetic I
eg Blood vessel
ACh- preganglionic
Nicotonic receptors
Noradrenaline - postganglionic
alpha and beta receptors
Sympathetic II
Adrenal Medulla
ACh- preganglionic
Nicotonic receptors
Noradrenaline + adrenaline - postganglionic
alpha and beta receptors
Muscarinic receptors
G protein coupled
5 subtypes - M1-M5
eg
M2 - cardiac - decrease cAMP- slows down the heart
M3- smooth muscle and glandular - increases IP3 and DAG- causes contraction of the visceral muscle
Nicotinic Receptors
5 subunits
Muscle receptors
Ganglionic receptors
found in:
non selective cation channels
mainly admits Na+/K+
Causes rapid cell depolarisation
Adrenergic Receptors
Alpha Receptors
Beta Receptors
Alpha Receptors-
2 subtypes
a-1 activates Gq which stimulates IP3/ Ca2+ and DAG 2nd messenger pathways- raises [Ca2+]
a-2 activates Gi which inhibits adenyl cyclase and therefore decreases cellular cAMP to decreases noradrenaline release
Beta Receptors
All activates G3 to increase cAMP
beta-1 main cardiac subtype
beta-2 main vascular and airway subtype
beta-3 found in adipose
NANC
Neither adrenergic or cholinergic
Can occur in ganglionic and post ganglionic synapses, particularly important in CNS neurones and ENS
eg some postganglionic sympathetic fibres release nucleotide gamma and ATP along with NA- for vasoconstriction
some postganglionic parasympathetic fibres release NO and vasoactive intestinal polypeptide along with ACh - vasodilation
Cotransmission
other NTs may be released along with ACh and nA
