Peripheral Nervous System Anatomy and Physiology [5] Flashcards
Describe the anatomical projections of the sympathetic and parasympathetic autonomic nervous system and the central control of the autonomic nervous system
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Discuss the concept of “tone” and explain the consequences of the fact that parasympathetic tone predominates at most organs and tissues (exception: sympathetic control of blood vessels)
“Tone” refers to which action predominates based on which component of the nervous system exerts a greater affect at a particular organ. Parasympathetic tone is associated with a state of “rest and digest.” (reduced HR, bronchial smooth muscle constriction, increased GI activity, increased motility of GU system, increased salivation)
Somatic neurotransmitters and receptors
NT: Acetylcholine
Recptors: Muscle-type nicotinic cholinergic receptors (nAChRs)–ionotropic receptors
Parasympathetic neurotransmitters and receptors
NT: Preganglionic: acetylcholine
Postganglionic: acetylcholine
Receptors: Postganglionic: neuronal-type nicotinic cholinergic receptors (nAChRs)–ionotropic receptors
End organ: muscarinic cholinergic receptors (MRs)–GPCRs
Sympathetic neurotransmitters and receptors
NT: Preganglionic: acetylcholine
Postganglionic: norepinephrine
Receptors: Postganglionic: neuronal-type nicotinic cholinergic receptors (nAChRs)–ionotropic receptors
End organ: alpha- or beta-adrenergic receptors—GPCRs
From which neurons is Acetylcholine released from?
Cholinergic neurons
From which neurons is Norepinephrine released from?
Adrenergic neurons
What receptors does acetylcholine interact with?
Cholinergic receptors (nicotinic [N] and muscarinic [M] subtypes)
What receptors does norepinephrine interact with?
Adrenergic receptors (alpha [α] and beta [β] subtypes)
Describe the preganglionic neurons of the Parasympathetic nervous system
Preganglionic neurons release ACh
At the GANGLIA, acetylcholine interacts with the NICOTINIC CHOLINERGIC receptors
(this the same as SNS)
Describe the postganglionic neurons of the Parasympathetic system
Postganglionic neurons release ACh
A the END ORGANS acetylcholine interacts with MUSCARINIC CHOLINERGIC receptors (heart, lungs, GI/GU tract, eye)
Describe the preganglionic neurons of the Sympathetic nervous system
Preganglionic neurons release ACh
At the GANGLIA, acetylcholine interacts with the NICOTINIC CHOLINERGIC receptors
(thi sis the same as PNS)
Describe the postganglionic neurons of the Sympathetic nervous system
Postganglionic neurons release….
- NOREPINEPHRINE at the EFFECTOR organs, which interaction with Alpha1-adrenergic (blood vessels, eye, GI tract) and Beta-adrenergic (B1 on heart, B2 on smooth muscle)
- ACETYLCHOLINE at SWEAT GLANDS which interacts with muscarinic cholinergic receptors
- DOPAMINE at the KIDNEY vascular smooth muscle with interacts with dopamine receptors
On what organs would you find Nicotinic cholinergic receptors?
Voluntary skeletal muscle at the neuromuscular junction
On what organs would you find Muscarinic cholinergic receptors?
Heart, lungs, GI/GU tract, eye
On what organs would you find Alpha1 adrenergic receptors?
Blood vessels, eye, GI tract
On what organs would you expect to find Beta adrenergic receptors?
B1- heart
B2- smooth muscle
Do most organs have single or dual innervation? What is the exception?
Most organs are DUALLY innervated
However, blood vessels receive sympathetic innervation only
Which branch of the autonomic nervous systems exerts predominant control over organs? What is the exception?
Predominant control is almost always exerted by the PARASYMPATHETIC branch
However, control of the vascular tone is done by the sympathetic branch
What are the physiologic actions of the Parasympathetic nervous system?
“Rest and Digest”
- Slowing of HR»_space; lowered BP
- GI motility and secretions, increased nutrient absorption
- Emptying of bladder and rectum (bladder muscle contract)
- Miosis (pupil constriction), focus for near vision
What are the physiologic actions of the Sympathetic nervous system?
“Fight or Flight”
- Accelerated heart rate»_space; rise in blood pressure
- Shift in blood flow from skin and splanchnic regions to skeletal muscles
- Rise in blood glucose
- Dilation of bronchioles and pupils
- Decrease in activity of GI and GU systems
Effects mediated by muscarinic receptors [M] at postganglionc effector organs
- Cardiovascular: decrease HR and AV conduction rate (vasodilation is an indirect effect and not a result of the PNS)
- Respiratory: bronchial muscle contraction
- GI: increase in secretory and motor activity, sphincters relaxed
- GU: relax sphincters, contract detrusor muscle
- Eye: miosis, focus for near vision, outflow of aqueous humor
Effects mediated by nicotinic neuronal receptors [Nn] at autonomic ganglia
- Cardiovascular: chiefly SYMPATHETIC effects; vasoconstriction, tachycardia, elevated BP)
- GI/GU tract: PARASYMPATHETIC effects (nausea, vomiting, diarrhea, vomiting)
Where are the Adrenergic receptor subtypes located?
At the sympathetic postganglionic synapses on effector organs or nerve terminals
