L4- ANS Flashcards
Where are the sympathetic ganglia?
Near the spinal cord
-short pre-ganglionic neuron, long post-ganglionic neuron
Where are the parasympathetic ganglia?
Near the effector organ
-long pre-ganglionic neuron, short post-ganglionic neuron
Why is the adrenal medulla like a post-ganglionic sympathetic neuron?
The adrenal medulla makes and releases epinephrine and norepinephrine into the bloodstream directly to stimulate response
- Post-ganglionic sympathetic neurons also release NE
What are the neurotransmitters used by the parasympathetic and sympathetic neurons, both pre- and post-ganglia?
Parasympathetic:
Pre-Ganglia: ACh
Post-Ganglionic: ACh
Sympathetic:
Pre-Ganglia: ACh
Post-ganglionic: NE (and FEW Ach)
All ANS pre-ganglia neurons release Acetylcholine (ACh)
What receptors are typically found on parasympathetic end organs?
Muscarinic Receptors (Slow)
What TYPE of the receptor is used by the parasympathetic end organs?
G protein Coupled Receptor (GPCR)
-Metabotropic
What receptors are typically found on sympathetic end organs?
Adrenergic Receptors (Fast)
- Alpha-Adrenergic
- α1: Activate phospholipase C -> produces IP3 and diacylglycerol (EXCITATORY)
- α2: Inhibit Adenylyl Cyclase -> decrease cAMP formation (INHIBITORY)
- Beta-Adrenergic (Stimulates adenylyl cyclase: EXCITATORY)
- β1: Inc cardiac rate and force
- β2: Bronchodilation, Vasodilation, relaxation of visceral muscles, muscle tremor
- β3: lipolysis, thermogenesis
Weird exception:
Sweat glands have muscarinic receptors on sympathetic ends
What TYPE of receptor is used by the sympathetic end organs?
G protein Coupled Receptor (GPCR)
-Metabotropic
Where are the receptors that are inhibitory to neurotransmitter released?
ACh inhibitory receptors:
M2, M4 from presynaptic terminal
NE inhibitory receptors:
α2 from postsynaptic terminal
What limits the rates of synthesis of ACh?
Access to Choline/Amount of Choline in the presynaptic terminal
- Choline is charged and most require transporter to cross membrane. Synthesis of acetylcholine depends on availability of Choline inside cell
What limits the rate of synthesis of NE?
The Hydroxylation tyrosine to form Dopa by Enzyme Tyrosine hydroxylase (tetrahydrobiopterin)
- Enzyme occurs in only catecholaminergic neurons
What process terminates the action of ACh?
Hydrolysis of ACh via Acetylcholinesterase
What process terminates the action of NE?
Reuptake of nonrepinephrine to the presynaptic vesicle
- Is target for many first generation drugs
What is Atropine?
Drug that blocks all muscarinic receptors
What is Propranolol?
Drug that blocks all beta-adrenergic receptors
*The transmitter used by postganglionic autonomic neurons and the receptor on which transmitter released from these neurons acts are
a. Norepinephrine/alpha1-adrenergic receptors
b. Norepinephrine/beta-adrenergic receptors
c. Acetylcholine/muscarinic receptors
d. Acetylcholine/nicotinic receptors
e. They are different depending on whether it is sympathetic or parasympathetic
e. They are different depending on whether it is sympathetic or parasympathetic
*The transmitter used by preganglionic autonomic neurons and the receptor on which transmitter released from these neurons acts are
a. Norepinephrine/alpha1-adrenergic receptors
b. Norepinephrine/beta-adrenergic receptors
c. Acetylcholine/muscarinic receptors
d. Acetylcholine/nicotinic receptors
e. They are different depending on whether it is sympathetic or parasympathetic
d. Acetylcholine/nicotinic receptors
*What is the rate-limiting step in the synthesis of acetylcholine?
a. The enzyme tyrosine hydroxylase
b. The production of acetyl-coenzyme A (acetyl-CoA)
c. The update of acetylcholine into the presynaptic neuron
d. The enzyme choline acetyltransferase
e. The uptake of choline
e. The uptake of choline
*The adrenal medulla is like a
a. Preganglionic sympathetic neuron
b. Postganglionic sympathetic neuron
c. Preganglionic parasympathetic neuron
d. Postganglionic parasympathetic neuron
e. All of the above
b. Postganglionic sympathetic neuron
Which receptors mediate neurotransmission in the autonomic ganglia?
A. alpha-adrenergic
B. beta-adrenergic
C. nicotinic-cholinergic
D. muscarinic-cholinergic
E. None of the above
C. nicotinic-cholinergic
What is the transmitter usually found in post-ganglionic sympathetic nerves?
A. norepinephrine
B. acetylcholine
C. nitric oxide
D. epinephrine
E. none of the above
A. norepinephrine
What is the limiting factor in the synthesis of acetylcholine?
A. the activity of tyrosine hydroxylase
B. the concentration of acetyl-CoA
C. the amount of choline in the presynaptic terminal
D. m2 muscarinic receptor stimulation
C. the amount of choline in the presynaptic terminal
What is the rate-limiting step in the synthesis of norepinephrine?
A. The uptake of tyrosine into the neuron
B. The hydroxylation of tyrosine to form DOPA
C. the decarboxylation of DOPA to form dopamine
D. the hydroxylation of dopamine to form norepinephrine
E. none of the above
B. The hydroxylation of tyrosine to form DOPA
A drug that stimulates beta 1 and beta 2-adrenoceptors can be expected to cause:
a. A decrease in heart rate
b. A decrease in total peripheral resistance
c. A constriction of airway smooth muscle resistance
d. A decrease in renin release
b. A decrease in total peripheral resistance
What is the rate-limiting step in the synthesis of epinephrine?
a. Conversion of dopa to dopamine by aromatic L-amino acid decarboxylase
b. Conversion of norepinephrine to epinephrine by
phenylethanolamine-N-methyltransferase
c. Conversion of tyrosine to dopa by tyrosine hydroxylase
d. Conversion of dopamine to norepinephrine by dopamine beta-hydroxylase
e. None of the above
c. Conversion of tyrosine to dopa by tyrosine hydroxylase
The primary neurotransmitter released by postganglionic neurons of the autonomic sympathetic system:
a. Epinephrine
b. Dopamine
c. Dobutamine
d. Norepinephrine
e. Phenylephrine
d. Norepinephrine
In the autonomic nervous system, which receptors are considered (give examples):
- ) Fast
- ) Slow
1. FAST: Ligand Gated Ion Channels
Ex: Nicotinic (ACh)
2. SLOW: Metabotrpic Receptors
Ex: Muscarinic (ACh); Adrenergic (NE, EPI)
