ANS pharmacology 1 Flashcards
autonomic nerves innervate
smooth muscle cells, cardiac tissue, exocrine glands
somatic nerves innervate
skeletal muscle cells
connection between CNS and organ in autonomic
pre and pos ganglionic neurons
connection between CNS and organ in somatic
single motor neurone
primary role of autonomic nerves
homeostasis
cardiac output
digestion
blood flow
primary role of somatic nerves
voluntary control
locomotion
posture
respiration
parasympathetic nervous system nerve type
○ Cholinergic nerves
§ Synthesize store and release acetyl choline
pre ganglionic receptors in parasympathetic
○ Ach released from pre ganglionic nerve activates nicotinic cholinoceptors on the cell surface of post ganglionic nerves
post ganglionic receptors in parasympathetic
○ Ach released from post ganglionic nerves activates muscarinic cholinoceptors on surface of effector cells
parasympathetic nerves exist spinal cord at
○ From cranial/sacral nerves
sympathetic nerves exist spinal cord at
thoracic or lumbar nerves
sympathetic pre gangliomic nerve
- Pre ganglionic nerve is cholinergic
sympathetic post ganglionic nerve
- post ganglionic is adrenergic
○ Uses noradrenaline
varicosities
(swellings in nerves
○ Contain vesicles of neurotransmitter, which are released by nerve AP
- Adrenergic nerves
○ Synthesize store and release NA
○ Most sympathetic post ganglionic nerves
- Cholinergic nerves
○ Synthesize store and release Ach
○ All parasympathetic post ganglionic nerves
○ Several sympathetic post ganglionic nerves
acetyl choline works on
choliceptors
2 types of cholinoceptors
nicotinic and muscarinic
3 muscarinic types
M1. M2, M3
M2 cholinoceptors
decrease heart rate
M3 cholinoceptor
contract smooth muscle and secrete glands
2 types adrenoceptors
Alpha beta
a1, a2, B1, B2, B3
4 adrenoceptor agonists
adrenaline and noradrenaline and phenylephrine and salbutamol
adrenaline
§ Stimulates all adrenoceptor subtypes
§ Inactive orally due to extensive metabolism in the GIT and liver
□ Typically given by injection
a1 adrenoceptors
contract vascular smooth muscle
b1 adrenoceptors
increase heart rate and force of contractility
b2 adrenoceptors
relax smooth muscle
adrenaline as local injection
□ High affinity for B2 and lower affinity for a1
low doses binds B2 for vasodilation
high dose binds a1 for vasoconstriction
adrenaline as slow intravenous
◊ Delivers constant levels of adrenaline over time
◊ Increases heart rate
} Stimulates B1 receptors in the heart
adrenaline in intravenous infusion effect on blood pressure
} Increase systolic blood pressure
– Stimulates B1 and increases force of contraction of cardiac muscle
} Decrease in diastolic blood pressure
– Because TPR decreases
adrenaline in intravenous infusion effect on total peripheral resistance
} A1 mediated vasocontraction
} B2 mediated vasodilator effect
– Predominantly in vascular beds of skeletal muscle
– Overrides A1 mediated vasoconstriction in other vascular beds
} Net effect is for TPR to decrease
slow bolus adrenaline
□ Initially high levels which decrease as Adr is metabolised
slow bolus adrenaline affect on total peripheral resistance
® At high doses
◊ Primarily a1 receptor mediated vasoconstriction
◊ Causes increase is diastolic blood pressure
slow bolus adrenaline affect on systolic blood pressure
® Activated B1 adrenoceptors to increase force of contractility
® Increase in mean arterial blood pressure
slow bolus adrenaline affect on heart rate
® Vagus nerve mediates decrease in heart rate as a reflex response to increase in blood pressure
slow bolus adrenaline as concentration decreases
® Vasodilation effect, decrease in total peripheral resistance, increase in heart rate (direct effect of adrenaline)
3 clinical uses of adrenaline
added to local anaesthetic to prolong the action
restores cardiac rhymthm in cardiac arrest
used in cute anaphylactic shock
- Noradrenaline
○ Also inactive orally due to metabolism in the Git and liver
○ Stimulates all AR subtypes except B2
○ Does not cause vasodilation
noradrenaline on heart rate
□ Direct effects of noradrenaline are overridden by vagal cardiac reflexed activated by increase in mean arterial blood pressure
noradrenaline effect on blood pressure
□ Increase in diastolic blood pressure
□ Increase in systolic blood pressure
® Response to activation of B1 force of contractility
noradrenaline effect on total peripheral resistance
Increases due to activation of a1 vasoconstriction in all major vascular beds
2 selective adrenoceptor agonsists
phenylephrine and salbutamol
- Are not extensively metabolised in the gut and the liver
○ Are active orally
- Phenylephrine
○ Activates a1 on vascular smooth muscle
○ Causes vasoconstriction
phenylephrine used for
○ Used clinically for relief of nasal congestion associated with acute and chronic rhinitis
§ Sudafed PE
`
- Salbutamol
○ Activates B2 on smooth muscle of airways, uterus and blood vessels
○ Primary effect is to cause relaxation of smooth muscle
salbutamol used clinically for
○ Used clinically to relieve bronchoconstriction in asthma
salbutamol given as
○ Typically given topically (as aerosol) directly to site of action (airways) rather than orally because
§ A more rapid bronchodilator response is achieved
§ A lower overall dose can be given (less side effects)
antagonism of which receptors is clinically useful
○ A1 - antagonism for hypertension
○ B1 - antagonism in many CV diseases
- Prazosin
○ Selectively binds and inhibits a1 adrenoceptors
antagonist
prazosin used for
○ Used clinically as antihypertensive agent
§ Not first line treatment in hypertension
when to take prazosin
○ May cause dizziness on standing, especially with initial use in the elderly
Taken before bed
tamulosin
§ Tamsulosin used for symptom relief in benign prostatic hypertrophy
§ Relaxes prostatic smooth muscle to improve blood flow
§ Tamsulosin has specific action against a subtype of a1 adrenoceptors
