Exam 2 Flashcards
What are the 2 parts of the peripheral nervous system?
Somatic NS- voluntary movement
Autonomic NS- involuntary
What are some similarities between Somatic and Autonomic NS?
both part of PNS
signals received from higher brain levels
integrative neurons provide stimulation/inhibition of both sysytems
What are some differences between Somatic and Autonomic NS?
somatic efferents go directly to their effector; neurons reach all the way to nueromuscular junction
autonomic efferents must synapse in a ganglion
neurons leaving the CNS- preganglionic
neuron that leaves the ganglion- postganglionic
What are integrative neurons?
complexes of neurons of the CNS, they recieve sensory input from multiple locations and throughout time
capable of processing this informatiion and determining the appropriate response
either stim/inhibt the somatic or preganglionic
2 components of the ANS:
sympathetic- fight/flight
parasympathetic- rest/digest
Where do fibers of the sympathetic nervous sysytem originate/terminate?
originate from the thoracic and lumbar spinal cord
enter the paravertebral chain of sympathetic ganglia
some will pass through to join ganglia elsewhere in the body
Give and example of sympathetic nerve fiber and its path:
Adrenal medulla
pregang fibers leave the T/L spinal segments, travel through the paravertebral chain synapse in the adrenal medulla
the cells of the medulla are considered the “post ganglionic” cells and release epinephrine
Post ganglionic symp fibers are LONG/SHORT the distance from ganglia is SHORT/FAR
LONG
FAR
What is meant by the the statement “the sympathetic is extremely reactive, and acts via mass discharge”
Extremely reactive: response to sympathetic stimulation is rapid and can vary moment to moment
Mass discharge: capable of mass action affecting virtually all sympathetic organs at once
Where do parasympathetic neurons orginate?
from nuclei in the midbrain, medulla, and sacral spinal cord
cranial nerves 3, 7, 9 10
Describe pre/post gang fibers of parasymp NS
preganglionic are long, synapse on/within effectors
therefore the post are short
Describe the effect of the sympathetic NS on the Heart
increased heart rate
Describe the effect of the sympathetic NS on the Peripheral Vasculature
constriction- decreases blood flow
Describe the effect of the sympathetic NS on the Skeletal Muscle/organ vascualture
Alpha 1- constriction
Beta 2- dialtion
Describe the effect of the sympathetic NS on the GI
Relaxation of smooth muscle
constriction of sphincter muscles
decreases secretions
Describe the effect of the sympathetic NS on the Bronchioles
Relaxation
Describe the effect of the sympathetic NS on the Urinary Bladder
Beta 2/3 relaxation of bladder body
alpha contraction of bladder trunk and internal sphincter
Describe the effect of the parasympathetic NS on the Heart
decreased heart rate
decreased contractile force
decreased conduction velocity
Describe the effect of the parasympathetic NS on the peripheral vascualture
dilation increases blood flow
Describe the effect of the parasympathetic NS on the skeletal muscle and organ vasculature
dialtion
Describe the effect of the parasympathetic NS on the GI
increases peristalsis
relaxation of sphincter muscles
decreased conduction velocity
Describe the effect of the parasympathetic NS on the bronchioles
constriction
Describe the effect of the parasympathetic NS on the urinary bladder
contraction of bladder body
relaxation of trunk and internal sphincter
What are cholinergic receptors?
activated by acetylcholine
What are the 2 types of cholinergic receptors?
Muscarinic
nicotinic
What are nicotinic receptors and where are they found?
Nicotinic Ach receptors (nAchr) – stimulated by nicotine in addition to Ach
acitvate an Ion Gated Channel
Found at synapse of preganglionic neurons onto the ganglia
Found at synapse of somatic neurons onto effectors
What are muscarinic receptors and where are they found?
Muscarinic Ach receptors (mAchr) – stimulated by muscarine, bethanechol, and pilocarpine in addition to Ach
Found at post ganglionic synapse of parasympathetic fibers onto effectors
G-coupled protein receptor
What are adrenergic receptors and where are they found?
Adrenergic receptors – activated by catecholamines such as norepinephrine or epinephrine
Found at post ganglionic synapse of sympathetic fibers onto effectors
A class of 7 transmembrane receptors who, when bound by agonist, will activate an enzyme cascade, starting with activation of a G protein
What are non-adrenergic, non-choline receptors?
Non-adrenergic, non-cholinergic receptors
Purinergic receptors – stimulated by purines
Found dispersed throughout body – i.e. urinary bladder
Facts about acetylcholine (Ach)
Acetylcholine (Ach)
oCreated by multiple enzymes in a long process
Choline-acetyltransferase is the rate limiting enzyme; the activity of this enzyme will determine the availability of Ach to be released into the synapse
o Acetylcholinesterase digests Ach in the synapse
Breaks it down and transports metabolites back into presynaptic cell for recycling oExcess Ach exposure can be treated with a cholinergic receptor antagonist OR acetylcholinesterase stimulant
Facts about Norepinephrine (NE):
Norepinephrine (NE)
o Classified as a catecholamine
o Tyrosine -> DOPA -> Dopamine -> Norepinephrine
Due to the relation between dopamine and NE, it is not unlikely that a dopamine agonist will likely also stimulate adrenergic receptors that bind NE
Facts about Epinephrine
Epinephrine (Epi)
o NOT identical to NE, thus will have a different effect on adrenergic receptors o More resilient in blood stream – less susceptible to degradation in bloodstream
Alpha-1 Receptors:
Present on vascular smooth muscle for vessels feeding the skin, kidney, viscera, and skeletal muscle
When bound by agonist (i.e. NE):
- Vasoconstriction
*Note, in some locations alpha 1 will be outnumbered by beta 2 receptors; therefore stimulation with agonists of both will result in beta 2 activity
Alpha 2 receptors:
Pre-synaptic ganglia; When activated these will work to auto-inhibit NE release.
Beta 1 receptors:
Present on the SA note, Atria, and Ventricles of the heart
Agonist will induce:
- Increased contractility (contraction strength), heart rate, and conduction velocity
- Overall stimulation of the heart
Beta-2 receptors
Found in a variety of locations:
- Pulmonary airway smooth muscle – bronchioles
a. Leads to dilation of airways – bronchodilation - Vasculature feeding skeletal muscle
a. Vasodilation
b. So, if there are more Beta 2 receptors than alpha 1 on a vessel feeding a skeletal muscle, then stimulation by agonist will result in vasodilation - Presynaptic neurons – within the membrane
a. Leads to auto-stimulation; presynaptic neuron releases NE, then that NE stimulates it to release more NE
What effects do norepinephrine/epinephrine have on the different receptor types?
- Epinephrine (Epi) is an agonist for all 4 subtypes of adrenergic receptors
- Norepinephrine (NE) is only agonistic for alpha 1,2 and beta 1o So stimulation of Beta 2 is limited to circulating Epi
What are the 3 most common catecholamines we talked about?
Epi,
NE
Isoproterol
Clinical application of Epi/NE/Isoproterol in local anesthetic:
- Keep it at the location you give it bc local vasoconstriction via activation of alpha-1 receptors
- Constriction of vasculature,
- HOWEVER- caution, decreased peripheral blood pressure could activate baroreflex, leading to bradycardia
- Also caustion giving in poorly perfused areas- ischemia