Sympathetic Nervous System Receptor Mechanisms

Question 1

what type of nerves are sympathetic nerves?

Answer 1

adrenergic neurones so they produce NA

Question 2

what does NA target?

Answer 2

adrenergic/adrenoreceptors

Question 3

adrenergic receptors are a subtype of what receptors?

Answer 3

GPCRs

Question 4

what are the 2 types of adrenergic receptors?

Answer 4

α and β adrenergic receptors

Question 5

what are α-adrenergic receptors more potent to?

Answer 5

NA> Adr

Question 6

what are the 2 types of α-adrenergic receptors and what do they bind to?

Answer 6

• α1-adrenergic receptors: binds to phospholipase C

- α2-adrenergic receptors: binds to adenylate cyclase

Question 7

what are the physiological effects of the 2 α-adrenergic receptors?

Answer 7

• α1-adrenergic receptors: vascular SM contraction

- α2-adrenergic receptors: inhibition of transmitter release

Question 8

what are the 3 types of β-adrenergic receptors and what do they bind to?

Answer 8

they too bind to adenylate cyclase

Question 9

what are the physiological effects of the β-adrenergic receptors?

Answer 9

• β1-adrenergic receptors: main cardiac effects

- β2-adrenergic receptors: vascular dilation/airway relaxation

Question 10

describe how α1-adrenergic receptors work

Answer 10

• results in the narrowing of the vascular lumen
• α1a is associated w the α11 subunit
• α11 interacts w PLC which cleaves PIP2 to IP3
• IP3 binds to the receptor on ER to cause release of Ca2+ which results in muscle contraction

Question 11

how do α2a work?

Answer 11

• decreases the amount of cAMP activated
• means that less PKA activated
• means less Ca2+ channels opened so cause a smaller release of Ca2+
• leads to an inhibition of transmitter released

Question 12

how do β1a work?

Answer 12

• the increase the amount of cAMP activated: in cardiac increased rate and force of contraction and increases the rate of relaxation
• cAMP binds to the SAN and AVN which leads to faster depolarisation so contraction increases
• cAMP interacts w PKA which turns on Ca2+ channels so more Ca2+ released which increases contraction and force
• PKA also activate K+ channels so increases rate of relaxation
• PKA also interacts w Ca2+ uptake channels so increases rate of the reaction

Question 13

what are the β1a and β2a effects on SM?

Answer 13

• relaxes SM: airways
• used to relieve asthma
• increased cAMP causes more Ca2+ to be released and increase in K+ channel activity
• that leads to a decrease in myosin light chain kinase activity so there is a decrease in contraction

Question 14

which type of adrenergic receptors do SM express?

Answer 14

both α and β receptors