Intro To PNS Flashcards
What is the sympathetic division of the autonomic nervous system driven by?
The hypothalamus to regulate involuntary functions in the skin and viscera
What is Group A of the peripheral nerves?
I to III or alpha, beta, delta and gamma fibers
Largest and fastest. Up to 20 micrometers
Ex: motor nerves, fusimotor nerves, propioceptive, pressure, touch, temperature and pain fibers
What are Group B peripheral nerves?
Up to 3 micrometers in diameters
Ex: myelinated pre-ganglionic autonomic fibers
What are group C peripheral fibers?
Up to 2 micrometers
Ex: unmyelinted post-ganglionic autonomic, touch and pain fibers
What are the 12 cranial nerves?
- Olfactory
- Optic
- Oculomotor
- Trochlear
- Trigéminal
- Abducent/abducens
- Facial
- Vestibulocochlear/auditory
- Glossopharyngeal
- Vagus
- Spinal accessory
- Hypo gloss all
What are the cranial nerves covered in as they emerge from the foramina or fissures of the skull?
Tubular sheaths derived from the meninges
Where do most cranial nerves emerge from except for cn 4?
Ventral aspect of the brain
What is the sulcus límitans?
The part that turns into the central canal in the embryo
What is the precursor to white matter?
Outer marginal layer
What is the precursor for gray matter
Inner mantle layer
What do the outer and inner marginal zone develop into?
Outer turns into alar plate
Inner turns into basal plate
What does the basal lamina develop into?
Into somatic motor efferent cells (GSE)
What does the alar lamina contain?
Cells that will develop into somatic sensory afferent cells (GSA)
After the basal and alar lamina develop, a group of new cells starts to develop around the sulcus limitans. What will this new group turn into?
General visceral afferents (GVA)
General visceral efferent (GVE)
Another cell type develops between the somatic and GVE/GVA to serve the branchial/pharyngeal apparatus. What will this cell develop into?
Into special visceral afferents (SVA) and special visceral efferent (SVE)
What s the special group of cells that serves the eye and ear?
Special somatic afferent (SSA)
What functional nerve groups are specific to the cranial nerves?
Special somatic afferent (SSA)
Special visceral afferent (SVA)
Special visceral efferent (SVE)
GSA, GSE, GVA and GVE are nerve fibers in all the PNS. What are their functions?
GSA: transmit general sensation from the body to the CNS
GSE: transmite motor impulses from CNS to Body
GVA: transmit sensation from viscera to CNS
GVE (autonomic): transmite secreto motor impulses to smooth muscle, cardiac muscle and glands
What are the function of the nerves fibers only found in cranial nerves?
SSA: convert sensation of vision, hearing/balance to CNS
SVA: convey smell ad taste sensation to the CNS
SVE: transmit motor impulses to muscles of the head and neck
How can you tell if a nerve is traveling to the CNS or away from the CNS?
Afferent: Ascend to CNS
Efferent: Exit CNS
Each spinal nerve contains sensory fibers with cell bodies in what location?
Dorsal root ganglion (GSA and GVA)
Each spinal nerve contains motor fibers with cell bodies in which locations?
Lamina IX (GSE)
Lateral horn = Lamina VII (GVE)
How are c1 to c11 connected to the sympathetic chain via which kind of fibers?
White rammus commicans with pre-ganglionic fibers
After c1-c11 synapse in the spinal ganglion, what kind of fibers are carried and to what location?
Post ganglionic (unmyelinated) to vessels for vasoconstriction, to sweet glands (sudomotor) and to the erector pilorum muscle of hair follicle
What do the dorsal rami innervates?
The integumentum and intrinsic back muscles
What do ventral rami give rise to?
Limb plexuses
E.g. Brachial, sacral
What is the neurovascular plane?
The space between the internal and innermost intercostal muscles where the spinal nerve branches and vessels that supply them are located
What is a reflex and which is the simplest one?
An automatic response mediated by the nervous system
Spinal reflex
What kind of reflex is the spinal reflex?
Monosynaptic.( two nerves and one synapse)
What are some examples of monosynaptic reflexes?
Ankle, knee, biceps and triceps
What does diminution of a reflex indicate?
Disruption of the reflex arc or muscle defect (Lower motor neuron lesion, LMNL)
What does exaggeration of a reflex indicate?
Supra-spinal component is disturbed (UMNL)
What kind of effect does supra-spinal control have on stretch reflex?
Produces a calming influence on the stretch reflex via the anterior horn cells of the spinal cord (alpha motor neuron)
What are some examples of multi-synaptic reflexes?
Abdominal, plantar and anal reflexes
What is the Beevor’s sign?in
The absence of abdominal wall contraction when the skin over the abdomen is lightly stroked
Where can Beevor’s sign be seen?
In parlegics which indicates UMNL
When is the dermatome concept applicable?
A. Low SPINAL anesthesia
B. Herpes zoster
What are the dermatomes of the Cervical nerves?
C1: no skin (both terror and posterior rami supply muscles, e.g. The suboccipital nerve)
C4: from clavicle to angle of Louis
C7: middle finger (thumb is C6, and pinky by C8)
What are the dermatome levels of the Thoracic nerves?
T4: nipple
T7:epigastrium
T10:umbilicus
What are the dermatome levels of the Lumbar and Sacral nerves?
L1:groin/supra-pubic/penis/anterior scrotum - Labium majus/upper buttock
S1: ankle/lateral side of dorsi mark of foot
S3: sitting areas of buttock/posterior scrotum - labium majus
S4: perianal skin
What is the extensor of the arm innervated by?
C7 & c8
How do the moto neurons (ANS) run from their nuclei to muscle?
Rum from the motor nuclei of cranial nerves or anterior horn cells of the spinal cord uninterruptedly to the motor end plate of skeletal muscle
What system is involved in the fight/flight response and the freeze/dissociate response?
ANS
What controls the ANS?
Regulated by the hypothalamus which is in the diencephalon just above the midbrain
What are the autonomic functions?
Respiration
CARDIAC regulation (center)
Vasomotor activity (dilation/constriction)
Reflexes such as sneezing, swallowing, vomiting and coughing
Where does the hypothalamus receive regulatory input for its ANS functions?
The limbic system
Where does the motor component of the ANS connect to?
Cardiac muscle
Smooth muscle
Glands
Describe the ANS innervation of motor neurons
A two neuron pathway
- A pre-ganglionic neuron cell body in the CNS
- A post-ganglionic cell body in a peripheral ganglion of the PNS
What are the two components of the ANS?
Sympathetic
Parasympathetic
What are the two parts of the sympathetic nervous system?
- The sympathetic trunks/chains that stretch from the base of skull to the coccyx
- The splanchnic/visceral nerves and their ganglia
Where is the pre-ganglionic cell body of the sympathetic nervous system?
Lateral horn/intermediolateral column (IMLC) of spinal cord with a thoracolumbar outflow (T1-L2)
Where does the pre-ganglionic neuron of the sympathetic travel from hypothalamus?
Travels along the anterior horn cells to the sympathetic chain/trunk with spinal nerve of that segment of the spinal cord, where these sympathetic axons have one of 3 choices.
What are the 3 options of sympathetic nerves when they reach their segment of the spinal cord?
- Synapse at the level they enter or go up/down to a different level in the sympathetic chain/trunk
- Leave the chain/trunk to a pre-vertebral/pre-aortic ganglion as a splanchnic nerve
- Leave the sympathetic chain/trunk with certain cells of the adrenal/supera-renal medulla (modified ganglion)
Where must sympathetic nerve fiber which rise along the sympathetic chain arch?
The head and neck through the cervical ganglia
Where must the sympathetic fibers that descend along the sympathetic trunk reach?
The pelvis/perineum nod lower limbs through the lumbar and sail ganglia of the sympathetic chain
How many cervical ganglia are there?
3
Why are there only 3 cervical ganglia?
The superior cervical ganglion is composed of a fusion of the first four
The middle cervical ganglion is composed of a fusion of the fifth and sixth
The inferior cervical ganglion is formed by a fusion of the 7th and 8th nerves
What is the stellate ganglion?
A fusion of the inferior cervical ganglion and the first thoracic ganglion.
How are the sympathetic ganglion numbered when they are connected to the corresponding nerve by white (distal) and gray rami communicantes.
By the corresponding spinal nerve with which it is associated
What are the two parts of the white Ramos communicantes?
- Pre-ganglionic myelinated fibers whose cell body is in the lateral horn/intermediolateral column (GVE)
- “Hitch hiking” visceral afferent (GVA) fibers whose cell bodies are located in the dorsal root ganglion (DRG)
Where are the cells bodies of the grey rim communicantes located?
Sympathetic chain/trunk
What kind of fibers does the grey ramus commicans contain ?
Only unmyelinted post-ganglionic sympathetic (GVE) fibers
What do the grey ramus commicantes supply?
- Blood vessels (vasoconstrictor)
- Sweat glands (sudomotor)
- Erector pilorum muscles of hair follicle (pilomotor)
What part of the body receives both white and grey rami commincantes connecting them to the sympathetic chain?
All the thoracic and upper two lumbar spinal nerves (T1-L2 =thoracolumbar outflow)
What spinal nerves only array grey rami commicantes?
Above T1 and below L2
The visceral part of the sympathetic nerves in the cervicals are called what?
Cardiac nerves
What nerves supplement the cardiac nerves?
Visceral nerves from upper thoracic ganglia (T1-2)
What do the splanchnic nerve pierce?
The thoracic diaphragm
What are the splanchnic nerves?
- Visceral nerves
1. Greater splanchnic nerves (T5-9)
2. Lesser splanchnic nerves(T10-11)
3. Least splanchnic nerves(T12)
4. Lumbar splanchnic nerves (L1-L2)
Where does the greater splanchnic nerve synapse?
In the celiac ganglia, at the root of celiac trunk/artery
Where does the lesser splanchnic nerves synapse?
In the superior mesenterio glangion, at the root of the superior mesenteric artery
Where does the least splanchnic nerve synapse?
In aortico-renal ganglion/plexus, at the root of renal artery
Where does the lumbar splanchnic nerve synapse?
In the inferior mesenteric ganglion at the root of the inferior mesenteric artery
How are the visceral branches of the sympathetic chain able to reach the foregut, mid-gut, hind-gut and their derivatives/adnexae?
From the roots of the ventral and lateral branches of the abdominal aorta (celiac trunk, superior mesenteric artery and inferior mesenteric after, renal artery)
The cervical ganglion gives vascular supply to which large vessels?
Carotid an vertebral arteries
The thoracic ganglia give vascular supply to which of the large vessels?
Thoracic aorta and major branches
The lumbar ganglia gives vascular branches to which of the large vessels?
Abdominal aorta and branches
The sacral ganglia gives vascular branches to which of the large vessels?
Iliac arterial system
How is the sympathetic branches of the limb supplied?
The vascular branches run with the somatic nerves of the limb (median, ulnar or sciatic nerves). Along the line they go off to their designated vessels distally.
Afferent fibers associated with visceral pain and with conscious reflex activities (visceral afferents) are what kind of neurons?
Pseudo unipolar with their bodies in the dorsal root ganglion (DRG)
How do afferent fibers that hitch hike on sympathetic reach the spinal nerves?
Via white ramus commicantes
Damage to the white rami commincant fibers (GVE) may also damage what fibers?
Visceral pain fibers
What is raynaud’s phenomenom?
Exaggerated vascular response to cold temperatures or emotional stress
When is sympathetic removal done?
When there is excessive activity to a particular part of the body
How can the sympathetic outflow to the upper limb be cut off? (Cervical region)
- Root of the neck
- Through the third intercostal space via axillary
- Trans-thoracic approach
How can sympathetic supply be cut of in the lumbar region?
An extra-peritoneal approach thoroughly the appropriate flank may be used
What is the parasympathetic division of the ANS limited to?
Viscera
What parts of the viscera appear to only receive sympathetic innervation?
Supra-renal glands and gonads
Where are the parasympathetic functions located?
In the cranial and sacral regions of the spinal cord
Which Cranial nerves have parasympathetic supply?
CN3: occulomotor
CN7: facial
CN9: glossopharyngeal
CN10: Vagus
What sacral nerves carry parasympathetic nerve supply?
Pelvic Splanchnic Nerve (S2-S4)
For each function of the parasympathetic in the cranial nerves, there will be. . .
- A nucleus containing the pre-ganglionic cell bodies located in the brain stem. These neurons are activated in response to commands from the hypothalamus
- At least one ganglion outside the CNS that contains the cell bodies of the post-ganglionic neurons
- A set of targets
What is the path of the parasympathetic fibers in CN3?
The axons from pre-ganglionic neurons in the Nucleus of Edinger-Westphal in the midbrain exit in CN3 and synapse on the post-ganglionic neurons in the ciliary ganglion.
What do the CN3 parasympathic fibers regulate?
The ciliary muscle nod sphincter pupillae of the eye
What is the path of the parasympathetic fibers of CN 7?
Axons from the superior salivatory nucleus in the pons exit in CNVII to synapse on 2 different peripheral ganglia: pterygopalatine and submandibular ganglia
What do the parasympathetic fibers of CN7 innervates?
Lacrimal and submandibular and sublingual salivary glands
What is the path of the parasympathetic fibers of CN9?
From the inferior salivatory nucleus in the medulla oblongata exit in CNIX and synapse on postganglionic neurons in the otic ganglion in the infratemporal fossa.
What do the parasympathetic fibers of CN9 innvervate?
Secretion of the parotid gland
What accounts for the activation of the 3 glands in the cranial region?
The superior and inferior salivatory nuclei
What is the pathway of the parasympathetic fibers of CN X?
Emerge from the large dorsal motor nucleus in the medulla oblongata descend in the vagus nerve to innervates viscera in the head/neck, thorax and part of the abdomen.
Where are the pre-ganglionic neurons of the pelvic splanchnic nerve?
Lateral horn of the spinal cord (IMLC)
How is the hypogstric plexus which innervates the viscera of the pelvic/perineum and the hind-gut as far as the transverse colon form?
From pelvic splanchnic nerve S2-S4 (para) and the hypogastric nerve (symp)
Where do visceral afferent from parasympathetic have their cell bodies? ( they run with glossopharyngeal and vagus)
Inferior ganglion of these cranial nerves (homologue of DRG)
Where do the central processes of parasympathetic afferent fibers pass to and what do they control?
To the nucleus of tractus solitarios which connects the brain stem nuclei and higher centers for reflex control of the heart rate, blood pressure, respiratory rate and gastrointestinal activity.
Where are the visceral afferent (para) fibers that accompany the splanchnic nerves have their cell bodies?
In the DRG of S2-S4 sacral nerves
Some of the fibers of para afferent visceral fibers control what reflex? (From splanchnic nerves)
Urinary bladder and anal sphincter reflexes
Besides the ANS what other component does the hypothalamus control?
Neuroendocrine system (homeostasis)
What tract does the hypothalamus utilize?
Descending tracts of the reticular formation
