Lecture 3 - Peripheral Nervous System Flashcards
What are the 2 types of sensory information? How to differentiate them?
- Somatic = Conscious: pain, proprioception, etc => can be pinpointed to an exact location
- Visceral = Unconscious: coming from viscera/glands => cannot be pinpointed
Which innervates more tissues: sympathetic or parasympathetic?
Sympathetic
List the 5 segments of the spinal cord from superior to inferior.
- Cervical
- Thoracic
- Lumbar
- Sacral
- Coccigeal
Describe the organization of the spinal nerves.
Rootlets => dorsal/ventral roots => spinal nerves => dorsal/ventral rami
What is a ganglia?
Collection of cell bodies in the PNS
What kind of neurons are sensory neurons?
Pseudounipolar
What kind of information does a spinal nerve carry? What do we call this?
Both motor and sensory = mixed nerve
What do the posterior rami supply?
Back intrinsic muscles and skin covering them
What do the anterior rami supply?
Limbs and ventral portion of the body
How many neurons from spinal cord involved in somatic motor innervation?
Single one connecting spinal cord to skeletal muscle
How many neurons from spinal cord involved in visceral motor innervation? What is the exception?
2: preganglionic and postganglionic neurons which synapse at ganglia
Exception: adrenal medulla composed of modified postganglionic neurons and innervated by preganglionic thoracic splanchnic sympathetic neurons
What are the 3 autonomic ganglia of the PNS?
- Paravertebral (chain) ganglia
- Prevertebral ganglia
- Intramural ganglia
Parasympathetic NS: how does the length of the preganglionic neuron compare to the postganglionic neuron? Why?
Longer preganglionic neuron because intramural ganglia are in the walls of the target organs
Sympathetic NS: how does the length of the preganglionic neuron compare to the postganglionic neuron? Why?
Longer postganglionic neuron because paravertebral and prevertebral ganglia are close to spinal cord
Where do the sympathetic preganglionic neurons synapse along the spinal cord? What do we call this?
T1 to L2 spinal segments = thoracolumbar outflow
Where do the parasympathetic preganglionic neurons synapse along the spinal cord? What do we call this?
- Brainstem cranial nerve nuclei (III, VII, IX, X)
- S2 to S4 spinal segments (sacral spinal cord)
Craniosacral outflow
Sympathetic outflow: if neurons only exit at T1-L2, how do we get
sympathetic signals to the top and the bottom of the body?
Along the length of sympathetic outflow (and through the WHOLE spinal column) we have sympathetic chain ganglia (paravertebral ganglia) where many of the sympathetic preganglionic fibers can move (up or down) to various sympathetic chain ganglia all along the length of the spinal cord and will form synapses with postganglionic fibers
How will the regions that can’t be innervated by the Vagus nerve be parasympathetically innervated? What are these 2 regions?
Parasympathetic splanchnic nerves in the sacral spinal cord (S2-S4)
Hindgut and pelvis
Sympathetic stimulation on heart?
- Increased heart rate
2. Increase in force of contraction
Sympathetic stimulation on blood vessels?
Constriction
Sympathetic stimulation on lungs?
Bronchodilation
Sympathetic stimulation on GIT?
- Decreased motility
- Sphincter contraction
- Decreased secretions
Sympathetic stimulation on bladder?
Inhibits urination
Sympathetic stimulation on penis?
Ejaculation
Sympathetic stimulation on skin?
Sweating
Parasympathetic stimulation on heart?
Decreased heart rate
Parasympathetic stimulation on blood vessels?
No effect except in genitalia (dilation) => erection
Parasympathetic stimulation on lungs?
Bronchoconstriction
Parasympathetic stimulation on GIT?
- Increased motility
- Sphincter relaxation
- Increased secretions
Where are the autonomic preganglionic neuron bodies found?
Ventral horns of spinal cord
Describe the sympathetic autonomic motor innervation pathway to the peripheral parts of the body.
Preganglionic neuron in ventral horn of spinal cord => anterior root => spinal nerve => white ramus communicans => synapse in paravertebral ganglion (same level/up/down the spinal cord) => postganglionic neuron => gray rami communicans => anterior or posterior ramus
Are there more white or gray rami? Why?
Gray because you only need a white rami at the T1-L2 segment of the spinal cord but gray rami occur anywhere along the spinal cord
Describe the 2 sympathetic autonomic motor innervation pathways to viscera. What does each innervate?
- Cardiopulmonary nerves (thoracic cavity): preganglionic neuron in ventral horn of spinal cord => anterior root => spinal nerve => white ramus communicans => synapse in paravertebral ganglion (same level/up/down the spinal cord) => postganglionic neuron (cardiopulmonary nerves) => viscera
- Splanchnics (abdominopelvic cavity): preganglionic neuron in ventral horn spinal cord => anterior root => spinal nerve => white ramus communicans => paravertebral ganglion (no synapse and same level/up/down the spinal cord) => splanchnic nerve exiting the paravertebral ganglion => synapse in prevertebral ganglion => postganglionic neuron => viscera
Are both pre and postganglionic nerves true splanchnic?
Only preganglionic
Do sacral splanchnic preganglionic neurons come out of the sacral spinal cord?
NOPE, the thoracolumbar one and then travel down the paravertebral chain ganglion to the sacral spinal cord
What do we call the sacral parasympathetic preganglionic neurons?
Pelvic splanchnics
What are the only parasympathetic splanchnics?
Pelvic splanchnics
Where are the intramural ganglia of the parasympathetic NS located?
Generally near target tissues
What kind of innervation do visceral plexuses receive?
Both sympathetic and parasympathetic
What are the 4 basic somatic plexuses?
- Cervical
- Brachial
- Lumbar
- Sacral
From what anterior rami is the brachial plexus formed?
Anterior rami of C5-T1
What 2 parts of the body does the brachial plexus innervate?
- Skin and muscles of upper limbs
2. Muscles that help control upper limbs (in back and shoulders)
What are the 4 brachial plexus terminal nerves? Describe their location.
Anterior side of plexus they form an M:
- Musculocutenous nerve (lateral end of M)
- Radial nerve (posterior to M structure)
- Median nerve (middle of M)
- Ulnar nerve (medial end of M)
Describe the location of the brachial plexus.
Starts at C5, travels down the neck to a region called the axilla (armpit) to T1
What are the 5 regions of the brachial plexus? What does this allow?
- Roots
- Trunks
- Divisions
- Cords
- Branches
Lots of terminal nerves will get contributions from multiple segments of the spinal cord
What 2 parts of the body does the musculocutaneous nerve innervate?
- Entire anterior compartment (including biceps)
2. Skin of lateral forearm
What 3 parts of the body does the radial nerve innervate?
- Triceps
- Posterior forearm muscles
- Overlying skin of both
What 3 parts of the body does the median nerve innervate?
- Forearm: most anterior compartment (except those innervated by ulnar nerve)
- Lateral 2/3rds of the hand: thenar eminence and 2 other muscles
- Overlying skin of hand
What 2 parts of the body does the ulnar nerve innervate?
- Forarm: flexor carpi ulnaris, 1/2 flexor digitorum profundus
- Hand: all intrinsic muscles excepts those innervated by median nerve
- Overlying skin of hand
What nerve is affected when you bump your funny bone?
Ulnar nerve
Where is the braxial plexus located in relation to the axillary artery?
Anterior
Where is the radial nerve located in relation to the axillary artery?
Posterior
What are some causes of superior brachial plexus injuries (C5-6)? How do we classify these?
Excessive increase in the angle between the neck and the shoulder: either trauma or obstetrics
What are causes of inferior brachial plexus injuries (C8-T1)? How do we classify these?
Occurs when upper limb is suddenly pulled superiorly causing stretching of the armpit: either trauma or obstetrics
Nerves affected by superior brachial plexus injuries?
C5 and C6
Nerves affected by inferior brachial plexus injuries?
C8 and T1
What does the lumbosacral plexus control?
Everything that moves the lower limbs
What are 4 nerves of the lumbosacral plexus?
- Femoral
- Obturator
- Sciatic
- Pudendal
What is the biggest nerve of the body?
Sciatic nerve
What part of the body does the femoral nerve innervate?
Anterior thigh
What part of the body does the obturator nerve innervate?
Medial thigh
What are the 2 branches of the sciatic nerve and what does each innervate?
- Tibial nerve: posterior leg and foot
2. Common fibular nerve: anterior and lateral leg, foot
What is another name for the common fibular nerve?
Peroneal nerve
What 2 parts of the body does the pudendal nerve innervate?
- Perineum
2. Skin of external genitals
What is the perineum?
Area between the anus and the scrotum or vulva
What is a spinal nerve?
Portion where the anterior and posterior roots meat = very short portion
What is another name for the intrinsic back muscles?
Deep back muscles
Why do the intrinsic back muscles have a different innervation than the rest of the skeletal muscles?
Different embryological origin than all other skeletal muscles in the body
Purpose of intrinsic back muscles?
Maintaining posture
Does a synapse occur in the dorsal root ganglia?
NOPE
What is another name for preganglionic neuron?
Presynaptic neuron
Where do the posterior and anterior rami lead to?
Limbs and superficial parts of the body
What are 3 other names for the sympathetic chain ganglia?
- Paravertebral ganglia
- Paravertebral trunks
- Sympathetic ganglia
Are cardiopulmonary nerves true splanchnics?
Not technically, because postganglionic
What are the 4 types of splanchnics and what do they each innervate? What kind of innervation does each provide?
- Thoracic (sympathetic): foregut and midgut of abdomen, adrenal glands, kidneys
- Lumbar (sympathetic): hindgut of abdomen, pelvis
- Sacral (sympathetic): pelvis
- Pelvic (parasympathetic): pelvis and hindgut
Do sympathetic thoracic splanchnic innervates viscera in the thorax?
NOPE!! Cardipulmonary nerves take care of that
Describe the pathway of the innervation of the adrenal medulla.
Preganglionic neuron in ventral horn of thoracolumbar spinal cord => anterior root => spinal nerve => white ramus communicans => paravertebral ganglion (no synapse) => splanchnic nerve exits => prevertebral ganglion (no synapse) => synapse on adrenal medulla
Where does vagus nerve innervation start and end?
Starts at foregut and ends after midgut
Can a plexus be somatic or visceral?
YUP
Are visceral plexuses both sympathetic and parasympathetic?
YUP
What is another name for the pudendal nerve?
Shameful nerve
Do both the nerves of the sympathetic innervation of the periphery and the viscera both use the paravertebral ganglia to travel up and down the spinal cord?
YUP
Describe the parasympathetic autonomic motor innervation pathway to the hindgut and pelvis.
Preganglionic neuron in ventral horn of sacral spinal cord (S2-S4) => anterior root => spinal nerve => anterior ramus => pelvic splanchnics => prevertebral ganglion (no synapse) => intramural ganglion => postganglionic neuron => viscera
Describe the parasympathetic autonomic motor innervation pathway to the foregut and midgut.
Vagus nerve => prevertebral ganglion (no synapse) => intramural ganglion => postganglionic neuron => viscera
Where are abdominal PREvertebral ganglia located in the abdomen?
Around the aorta near the major unpaired branches to the digestive tract (celiac, SMA, and IMA)
What is an example of a visceral plexus?
Plexus on the aorta from splanchnic nerve innervation = prevertebral plexus
What 3 nerves are located anterior to the axillary artery? List them from lateral to medial
- Musculocutaneous
- Median
- Ulnar
