ANS anatomy & physiology Flashcards
Two divisions of the Nervous System
Central & Peripheral
3 divisions of the Autonomic nervous system
- SNS
- PSNS
- Enteric
Which is more integral for survival SNS or PSNS?
PSNS - the ability to remove waste and toxins from our body will prob kill us faster than the rare chance we need to run from a bear.
What kind of muscle does NOT receive signals from the autonomic nervous system
Skeletal muscle
What makes up the brainstem? (3)
Midbrain
Pons
Medulla
The SNS originates from which spinal cord levels?
T1-L2 (L3)
“Thoraco-lumbar”
Spinal cord ends ~ L2, so just think that
Sympathetic nervous system efferents have (long/short) preganglionic fibers and (long/short) postganglionic fibers
short pre
long post
Blockade of which ganglion produces horner syndrome?
Stellate (cervicothoracic)
Preganglionic neurons are made up of what kind of nerve fibers?
Lightly myelinated B-fibers
Postganglionic neurons are made up of what kind of nerve fibers?
Unmyelinated C-fibers
The PSNS efferents originate from which cranial nerves and spinal cord levels?
Cranial nerves: 3, 7, 9, 10
& S2-S4
“Craniosacral” system
What part of the spinal cord does the somatosensory division arise from?
The ventral horn
I think you gotta think in terms of the autonomic nervous system
Somatic and visceral innervations
>visceral innervations are plexus’s
>somatic are via spinal nerves that arise from the ventral horn
What part of the spinal cord does the sympathetic division arise from?
The lateral horn of the gray matter
What spinal cord levels contain gray rami?
All of them
The SNS has a ratio of (pre/post)ganglionic to (pre/post) ganglionic nerve ratio of 30:1
post: pre of 30:1
* a lot more postganglionic fibers
The sympathetic trunk divides into what two distribution pathways?
Somatic and Visceral
What sympathetic distribution group travels to effectors via spinal nerves vs plexus’s?
somatic group travel via spinal nerves
visceral group travel via plexus’s
What is the stellate ganglion a result of?
The joining of the inferior cervical ganglion & T1 ganglion
Horners syndrome results from blockade of what?
Stellate ganglion
Does a stellate ganglion blockade result in ipsilateral or contralateral symptoms and what are they? (6)
Ipsilateral
- Ptosis
- Miosis
- Enophthalmos (sunken in eyeball)
- Nasal congestion
- Anhydrosis
- Flushed Skin (flushing skin but no sweat)
(3 eye effects, 1 nose, 2 skin)
(Skin effects of the same sided upper extremity)
What 3 plexus’s do the thoracic viscera receive SNS efferents from?
- Cardiac plexus
- Pulmonary plexus
- Esophageal plexus
SNS efferents to the abdominal and pelvic viscera are delivered by what 4 plexus’s?
- Celiac plexus
- Aortic plexus
- Superior hypogastric plexus
- Inferior hypogastric plexus
ALL preganglionic sympathetic nerve fibers are what type of fibers (A/B/C) and where do they all arise from?
Preganglionic sympathetic nerve fibers = B fibers
Arise from T1-L2
The stellate ganglion provides SNS innervation to what 3 places?
Ipsilateral head, neck, and upper extremity
4 things a stellate ganglion block can be used for.
- Upper extremity sympathetic dystrophy
- Complex regional pain syndrome
- Increase blood flow to the upper extremity
- tx of intractable post-MI pain
A stellate ganglion block is often an unanticipated consequence of what kind of block?
Brachial plexus (interscalene)
Horners syndrome mnemonic
Very Horny PAM
Vasodilation HORNER Ptosis Anydrosis Miosis
Which preganglionic sympathetic nerve fibers transverse the sympathetic trunk and form the Greater Splanchnic Nerves?
T5-T10
```
T1-T4 = Cardiac plexus
(T5-T10 = GSN)
(T10-T11 = LSR SN)
(T12 = LST SN)
~~~
Which ganglion provides efferents to the stomach, liver, gallbladder, and pancreas?
Celiac
Which ganglion provides efferents to the kidney?
Aorticorenal
Which ganglion provides efferents to the small intestine and ascending colon?
Superior mesenteric
Which ganglion provides efferents to the transverse, descending, and sigmoid colon + rectum?
Inferior mesenteric
What ganglion provides efferents to the urinary bladder and reproductive organs?
Pelvic
The intermediolateral nucleus lies within which Rexed’s Lamina?
7
Which plexus may be blocked for relief of pain secondary to chronic pancretitis?
Celiac plexus block
What plexus lies at L1?
Celiac plexus
What 3 skin structures receive sympathetic stimulation from spinal nerves?
- Cutaneous arterioles
- Sweat glands
- Piloerector muscles
Which two cranial nerves supply motor innervation to the salivary glands?
Glossopharyngeal
& Facial
T/F: The vagus nerve innervates salivary glands
False!
Which cranial nerve lies within the CNS?
CN2 - Optic nerve
Which cranial nerves provide parasympathetic outflow to target organs/tissues?
3, 7, 9, 10
Cranial Nerve I
Sensory/Motor/Both
Olfactory
Sensory - Nose
Cranial Nerve 2
Sensory/Motor/Both
Optic
Sensory - Eyes
Cranial Nerve 3
Sensory/Motor/Both
Oculomotor Motor- eyes -all ocular muscles except: superior oblique (CN4) & lateral rectus (CN6)
+sphinchter/ciliary muscles & eyelid muscle
Cranial Nerve 4
Sensory/Motor/Both
Trochlear
Motor- eyes
Eye muscle: superior oblique
Cranial Nerve 5
Sensory/Motor/Both
Trigeminal
Both
Cranial Nerve 6
Sensory/Motor/Both
Abducens
Motor- eyes
Eye muscle: lateral rectus
Cranial Nerve 7
Sensory/Motor/Both
Facial
Both
Cranial Nerve 8
Sensory/Motor/Both
Vestibulocochlear
Sensory- Ears
Cranial Nerve 9
Sensory/Motor/Both
Glossopharyngeal
Both
Cranial Nerve 10
Sensory/Motor/Both
Vagus
Both
Cranial Nerve 11
Sensory/Motor/Both
Spinal Accessory
Motor - shoulder shrug
Cranial Nerve 12
Sensory/Motor/Both
Hypoglossal
Motor- tongue
Mneumonic for cranial nerve names
On occasion, our trusty truck acts funny. Very good vehicle anyhow.
Mnemonic for cranial nerve functions
Some say marry money, but my brother says bad business to marry money.
Sensory only cranial nerves (3)
1, 2, 8
Smell, Sight, Sound
Sensory + Motor cranial nerves (4)
5, 7, 9, 10
Paraysympathetic outflow CNs = 3 7 9 10
Which cranial nerve carries parasympathetic innervation to the submandibular, sublingual, and lacrimal glands?
CN 7 - Facial
What are the 5 motor branches of the facial nerve?
Temporal, Zygomatic, Buccal, Mandibular, Cervical
Two zebras bit my car
What is the sensory function of cranial nerve 7?
(Facial nerve)
-anterior 2/3 of the tongue - taste
Between cranial nerves 7 and 9, which ones are mostly sensory vs mostly motor?
7- mostly motor
9- mostly sensory
What kind of receptors lie on the carotid bodies?
Chemoreceptors
What kind of receptors lie on the carotid sinus?
Baroreceptors
What nervous system regulates the activity of our internal organs?
Visceral/Autonomic Nervous system
Which nervous system enables us to interact with our environment?
Somatic
CNS = brain and SC
Peripheral NS = sensory and motor
Motor further divided into ANS (automatic) and somatic (motor, voluntary)
Where do the preganglionic nerve fibers for the oculomotor (cranial nerve 3) originate?
Edinger-Westphal nucleus
The parasympathetic neurons consist of what cranial nerves and spinal cord segments?
CN 3, 7, 9, 10
S2-S4
Another name for the parasympathetic division of the ANS?
Craniosacral system
The parasympathetic efferent pathways consist of (long/short) preganglionic neurons and (long/short) postganglionic neurons
Long pre
Short post
(they have a longer route to travel and don’t enter the sympathetic chain)
White rami only exist in which spinal nerve segments?
T1-L2/3
Which cranial nerve is responsible for miosis?
Cranial nerve 3 - oculomotor
Parasympathetic response
Which cranial nerve is responsible for near vision accommodation?
CN 3- oculomotor
via contraction of the ciliary muscle which releases the tension from suspensory ligaments of the lens
thicker lens = near vision accomodation
What cranial nerve is responsible for tearing?
CN 7 - facial
Stimulation of the lacrimal gland
*Parasympathetic response
Visceral afferents from the heart, lungs, and GI tract are sensed by the vagus nerve and travel to which nucleus?
The nucleus of the tractus solitarius (NTS)
What kind of nerve fibers compose most of the visceral afferent nerves?
Non-myelinated C fibers or
lightly myelinated A-delta fibers
Which cranial nerve afferents are implicated in the baroreceptor response for the maintenance of blood pressure?
CN 9 - Carotid Sinus
& CN 10- Aortic Arch
Which cranial nerve afferents are implicated in the chemoreceptor response for the control of ventilation?
CN 9 - Carotid Body
& CN 10 - Aortic arch
What is known as the parasympathetic neurotransmitter?
Acetylcholine
What does it mean if a nerve fiber is cholinergic
It produces acetylcholine
All preganglionic neurons in the ANS (both PSNS & SNS) use what as their primary neurotransmitter across all autonomic ganglia?
Acetylcholine
What are 2 potent inhibitors of ganglionic a3B4 autonomic cholinergic receptors?
Volatile anesthetics & Ketamine
-Signal can’t get across to propagate up to the brain
Where does acetylcholine synthesis occur at?
In the presynaptic nerve terminal
What antagonizes calcium at the presynaptic nerve terminal?
Magnesium
(explains why mag can cause muscle weakness or enhance NMB…. no calcium, no acetylcholine released, less stimulation of post-ganglionic fibers to affect muscle contraction)
Are nicotinic receptors ionotropic or metabotrophic?
ionotropic
What differentiates adult from fetal nicotinic ACh receptors?
adult has an E subunit
fetal has a y subunit
What are the parasympathetic receptors found in the heart?
M2 cholinergic receptors
GI- inhibit adenylyl cyclase
What receptors mediate bronchoconstriction?
M3 cholinergic recetpros
Gq- activate phospholipase C
What kind of receptors are located pre-synaptically and work as a negative feedback loop to inhibit the release of further acetylcholine?
M2 receptors
What enzyme catalyzes the synthesis of Acetylcholine?
Choline AcetylTransferase
ChAT
What is another name for en passant synapses?
Neuroeffector junctions
What NT stimulates sweat glands? What receptor does it attach to?
Sympathetic or parasympathetic response?
Acetylcholine from post-synaptic sympathetic neurons onto M3 receptors
*This is the only post-ganglionic sympathetic neuron that secretes ACh (instead of NE)
GPCR for Alpha 1
Gq
GPCR for Alpha 2
Gi
GPCR for Beta 1
Gs
GPCR for Beta 2
Gs
Activation by NE of which presynaptic receptor can increase the release of NE/Epi (Positive feedback loop)?
Presynaptic Beta 2
Activation by NE of which presynaptic receptor can inhibit further release of NE?
Presynaptic Alpha 2
Activation by ACh of which presynaptic receptor can inhibit further release of ACh?
Presynaptic M2
Activation by ACh of which presynaptic receptor can increase the release of ACh (positive feedback loop)?
Presynaptic nicotinic Nn
Which sympathetic post-ganglionic neurons are actually cholinergic, what do they secrete, and what receptors do they bind to?
Exocrine sweat glands
-ACh is secreted and binds to M3 muscarinic receptors
Contraction of which muscle of the iris causes mydriasis? What NT/Receptor? SNS or PSNS?
Dilator Pupillae (Radial) (radical dilator)
NE > Alpha 1
SNS
(T1 > superior cervical ganglion > NE > alpha 1)
Contraction of which muscle of the iris causes miosis? What NT/Receptor? SNS or PSNS?
Sphincter pupillae (Circular) (circular sphincter)
ACh > M3
PSNS
(CN3 > ACh > M3)
What heart tissue shows little to no response from ACh?
ventricular muscle (myocytes)
Which brain region is most important for the coordination and control of ANS output?
Hypothalamus
What is the single most important integrator of autonomic and endocrine function?
The hypothalamus
What is the major lower brain stem command center for visceral control?
The nucleus tractus solitarius (NTS)
Where is the hypothalamus located?
at the base of the brain, above the pituitary gland
8 Things the Hypothalmus helps regulate?
- Autonomic function with eating
- Thermoregulation
- Circadian rhythms
- Water balance
- Emotions
- Sex drive
- Reproduction
- Motivation
Which lower brainstem structure receives visceral afferents from cranial nerves 7, 9, & 10?
The nucleus tractus solitarius
Mnemonic for the 6 cardiac reflexes?
3 Bees in the CV… Ouch!
- Baroreceptor
- Bainbridge
- Bezold- Jarish
- Chemoreceptor
- Valsalva
- Occulocardiac
What is the purpose of the baroreceptor reflex?
A quick response to short-term BP regulation
Reflex- quick! let me fix this! –> proceeds to drop BP and HR and make you wanna vomit and pass out
What cardiac reflex is responsible for the increase in cardiac output (increased HR and inotropy) as a result of persistent hypoxemia?
Chemoreceptor Reflex
What are the afferent and efferent limbs of the oculocardiac reflex?
afferent limb = cranial nerve 5 (trigeminal)
efferent limb = cranial nerve 10 (vagus)
Another name for a feedback loop
Reflex arc
What 3 key areas receive the bulk of sensory information from the body?
Hypothalamus
Spinal Cord
brainstem
What is a ganglion?
A relay site where the preganglionic nerve synapses with the postganglionic nerve.
Which cardiac reflex is considered a high-pressure arterial reflex vs a low-pressure cardiopulmonary reflex?
High-pressure arterial reflex = BRR
low-pressure CP reflex = Bainbridge
Which volatile anesthetic impairs the baroreceptor reflex the least?
Isoflurane
Has mild Beta-1 Agonist properties –> BP doesn’t drop as low, reflex not as significant
Where is the carotid sinus located?
At the origin of the ICA, right below where the ICA and ECA bifurcate
What does the nerve of herring innervate?
The carotid sinus
> converges with the glossopharyngeal (9) to send afferent impulses to the nucleus tractus solitarius in the medulla
What 2 procedures may elicit the baroreceptor reflex?
- CEA > pressure from manipulating the carotid sinus
2. Mediastinoscopy > pressure on the transverse aortic arch
How do volatile anesthetics affect the baroreceptor reflex?
Volatile anesthetics decrease the HR response to the baroreceptor reflex in a dose-dependent fashion.
T/F Phenylephrine is a catecholamine
False
What cardiac reflex slows the HR in the setting of profound hypovolemia (decreased preload)
Bezold- Jarisch
> heart slows in an attempt to allow the heart to fill
What cardiac reflex increases the heart rate in response to venous congestion (increased preload)
Bainbridge
> try to promote forward flow
What is the chemoreceptor reflex stimulated by?
Hypoxia and hypercarbia
What does stimulation of the chemoreceptor reflex result in?
Increased minute ventilation and increased SNS tone
Triad of symptoms that characterizes the Bezold-Jarisch reflex
- Bradycardia
- Hypotension
- Coronary artery vasodilation
What reflex may be initiated secondary to autotransfusion during childbirth and rapid administration of IVF?
Bainbridge
What reflex is elicited with profound hypotension, massive hemorrhage, and shoulder arthroscopy + regional anesthetic + sitting position
Bezold-Jarisch
What is the strongest stimulus at peripheral chemoreceptors?
Hypoxia
Response to acute hypoxia vs persistent
Acute = PSNS -> decreased HR and contractility (attempts to slow down to get more o2 to the heart, heart contracts less to try and preserve what o2 is there)
Persistent hypoxia = SNS activation (oh shit, cant fix this issue, let me speed up and get as much o2 out to the tissues as I can)
Two causes of vasovagal reflex/syncope?
- Psychologic stress
2. Peritoneal stretching/distension
Does a retrobulbar block cause or prevent the oculocardiac reflex?
both
Factors that worsen the severity of the oculocardiac reflex (3)
Hypoxia
Hypercarbia
Light anesthesia
3 steps in treating oculocardiac reflex
- ask surgeon to stop
- 100% fio2, ensure adequate ventilation, deepen anesthetic
- anticholinergic
Which brainstem center is known as the vasopressor or vasomotor center?
Rostral ventrolateral medulla (RVLM)
S/S & cause of Cushing’s triad
- Bradycardia
- HYPERTENSION
- Irregular respirations
*in response to increased ICP
What is shivering diminished by? (3)
NMB, old age, and NM diseases
Thermoregulation in newborns and infants occurs how?
By nonshivering thermogenesis via norepinephrine
Forced expiration against a closed glottis results in what reflex?
Valsalva
Which receptor mediates dilation of coronary arteries?
Beta 2
What kind of muscle is smooth muscle (3)
blood vessels, GI walls, bladder wall
The two somatomotor peripheral motor neuron types
A-motor neurons & Y- motor neurons
A-alpha & A-gamma
Where do the cell bodies of afferent sympathetic nerve fibers lay?
In the dorsal root ganglia
