Autonomic Flashcards
Parasympathetic preganglionic axons leave the CNS through the
Cranial nerves and sacral spinal nerve roots. Craniosacral.
Long preganglionic axon, short post.
Sympathetic preganglionic axons leave the CNS through the
Thoracic and lumbar spinal nerves. Short preganglionic axons –> Sympathetic chain –> Long post
Parasympathetic
- Location of ganglia
- Preganglionic fiber branching
- Distribution
- Type of response
- Within or near effector organs.
- Minimal branching
- Limited distribution
- Discrete response. Will only activate 1 effector organ.
Sympathetic
- Location of ganglia
- Preganglionic fiber branching
- Distribution
- Type of response
- Close to spinal cord.
- Extensive branching
- Wide distribution.
- Diffuse response. Might activate multiple effector organs.
Is the somatic nervous system gangliated?
No. Cell body is in the spinal cord at all levels.
Axon extends to skeletal muscle that it innervates.
Synapse between somatic neuron and skeletal muscle is called
NMJ
Effector cells
Cells innervated by a motor neuron or postganglionic neuron.
Why might there be some cells that possess receptors for ANS or somatic NT but are not innervated by neurons
Respond to the NT released in blood stream.
Ex: NE released into the blood.
PNS
Divided into the ANS and Somatic system.
ANS is divided into enteric, parasympathetic and sympathetic and innervates smooth muscles/cardiac muscles/glands.
Somatic system innervates skeletal muscles during voluntary movements and sensory info (pain/touch)
What is the basal activity of pre and post ganglionic neurons?
Non-zero. Not on or off. Always modulated. Generation of AP occurs in the absence of input from CNS or pregang axons.
How is ACh synthesized, released into synapse, and removed?
Synthesized in the axon terminal from acetyl Co-A and choline by choline acetyltransferase.
Transported into vesicles and released into the synapse following an AP.
Can either bind to pre-ganglionic receptor to downgrade release of ACh or to post-ganglionic receptor to initiate a cellular response.
Terminated by acetylcholinesterase, which breaks ACh into choline and acetate.
How many molecules of Ach can acetylcholinesterase bind at a time
1
Cholinergic synapses
Muscarinic: Parasympathetic effector cell synapse.
Nicotinic: All ganglionated synapses of the ANS. Activation always causes excitation.
NMJ is nicotinic.
Muscarinic cholinergic receptors
desensitization?
On/off speed?
Do NOT exhibit desensitization. Constant activation causes constant amplitude of response.
Slow on/slow off.
Effects of muscarinic activation Eye Exocrine glands Heart GI Bladder Respiratory Blood vessels
Eye:
Miosis
Contraction of ciliary muscles = near vision
Exocrine glands:
Increased secretions- tears, saliva, mucous in stomach
Heart:
Decreased heart rate= decreased CO and BP
GI tract:
Increased muscle tone
Increased peristaltic activity
Bladder:
Contraction of detrusor muscle
Relaxation of internal sphincter muscle.
Respiratory:
Constriction of bronchioles and increase in mucous secretion. Breathing is more difficult, but you don’t need as much when resting/digesting,
Blood vessels:
Dilation through non-innervated receptors.
Nicotinic Cholinergic receptor
Desensitization?
On/off rate
Rapid form of desensitization. Constant activation will result in diminished response over time. Binding still occurs, but is as if the receptor has come unplugged (tachphylaxis)
Fast on/fast off.
Two subtypes of cholinergic receptors
Ng (neurons/ganglia)
-Activation induces increased frequency of AP generation in post synaptic neurons.
Nm (skeletal muscle fibers- NMJ)
-Activation of Nm receptors induces action potential generation in and contraction of skeletal muscle fibers.
Muscarinic receptors and affinity for ligands high to low
High Muscarine ACh Nicotine Low
Nicotinic receptors and affinity for ligands high to low
High Nicotine ACh Muscarine Low
How is NE synthesized, released, and removed?
NE is synthesized in the axon terminal. Tyrosine is transported in from the extracellular space and converted to DOPA by tyrosine hydroxyls. DOPA Is converted to dopamine by aromatic amino acid decarboxylase.
Dopamine is put in storage vesicles and converted to NE by dopamine beta hydroxyls. Then released.
Removed from synapse by reuptake into the axon terminal and repackaged. Can be metabolized by MAO (monoamine oxidase) and then diffuse into surrounding tissue,
Acetylcholinesterase is active where
MAO is active where
In the synaptic terminal
In the pre-synaptic neuron
Adrenergic receptors (4 major sub-types)
Post synaptic: A1, B1, B2
Pre synaptic: A2.
Adrenergic receptors are coupled to its effector mechanism through ______
on/off speed?
Desensitization?
Through a GPCR
Slow on/slow off.
Can be desensitized
Which receptor can NOT be desensitized
Muscarinic cholinergic.
Nicotinic cholinergic and adrenergic can be desensitized.
