Chapter 13 Part 2) PNS Flashcards
1
Q
Spinal Nerves
A
- We have 31 pairs of Spinal Nerves.
- All are mixed nerves
- Named from the point of origin on the spinal chord
- Supply all body parts except head and part of the neck (cervical nerves)
- Regions
- Cervical Nerves) 8 Pairs (C1-C8)
- The first seven nerves exit superior to C vertebrae
- C8 exits inferior to C7
- C7 has one nerve above and below it
- Thoracic Nerves) 12 pairs (T1-T12)
- Lumbar Nerves) 5 pairs (L1-L5)
- Sacral Nerves) 5 pairs (S1-S5)
- Coccygeal Nerves) 1 Pair (Co1)
- Cervical Nerves) 8 Pairs (C1-C8)
2
Q
Spinal Nerve Roots
A
- Each Nerve is connected to the spinal chord via two roots
- Ventral Roots
- Contain Motor (effrent) fibers from ventral horn motor nuerons
- Innerviate Skeletal muscles
- Dorsal Roots
- Contain sensory (affrent fibers) from sensory nuerons in dorsal root ganglia
- Conduct impules from perpherial receptors
3
Q
Spinal Nerve Branches
A
- Spinal Roots become longer as you go down the chord
- Lumbar and Sacral roots are very long (cauda equina)
- Spinal Nerves are very short
- only extend about 1-2 cm before they branch
- Diffrent branches of Spinal Nerves
- Dorsal Ramus) smaller branch from dorsal roots
- Ventral Ramus) larger branch from ventral roots
- Menigeal Branch) tiny branch that reenters the vertebral canal to innervate menigenes and blood vessels.
- Rami Communicates
- Communicate signals
- contain autonomic nerve fibers that join ventral rami in thoraic region
4
Q
Innervation Of Specific Body Regions
A
- Spinal Nerve Rami and branches supply innervation to entire somatic region (skin and muscle) from neck down
- Dorsal Rami) supply posteior body trunk
- Ventral Rami) Supply rest of the trunk and the limbs
- Diffrences between roots and Rami
- Roots
- are more medial and form the spinal nerve
- Each is purly sensory or purly motor
- Rami
- More distal and form branches
- Carry both sensory or motor fibers
- Roots
- All Ventral Rami (except T2-T12) branch and rejoin to form complicated networks called Nerve Plexuses
- only ventral rami
- Fibers cross over in plexus
- Means one nerve will have more than one fiber type
- damage to one nerve does not mean entire paryalsis.
5
Q
Cervical Plexus
A
6
Q
Brachial Plexus
A
- Gives rise to virtually all of the nerves that innervate the upper limb
- Orginates from Ventral Rami of C5-8 and most of T1 (may also come from C4 or T2)
- Four Major Branches
- Roots) Five Ventral rami rami (C1-T1) form…
- Trunks) Upper, middle and lower trunk unit to form…
- Divisions) Anterior and Posterior, unit to form…
- Cords) Lateral, Medial, and Posteior
7
Q
Five Important Nerves of the Brachial Plexus
A
- Cords of brachial plexus give rise to nerves of the upper limb. There are 5 important ones
- Axillary) Innerviates Deltiod, Teres minor, and skin and joint capsule of the shoulder
- Musculocutaneous) Innerviates Biceps Brachii, Brachialis, coracobrachialis, and skin of lateral forearm
- Median) Innerviates skin, most Flexors, forarm Pronators, Wrist and Finger Flexors, and Thumb oppostion muscles
- Ulnar) Innervates Flexor muscles, and skin of medial hand.
- Radial) Innercates essentially all extensor muscles, supinators, and posteiror skin of limb
8
Q
Injuries to Brachial Plexus
A
- Brachial Plexus) common injury
- severe injuries can weaken or paralize the entire upper limb
- Injuries may occur if upper limb is pulled to hard which streatches the plexus
- Median Nerve) injury makes it difficult to use thumb and pointer finger to pick up small objects
- Carpal Tunnel) median nerve is compressed
- Ulnar Nerve) Damage can lead to sensory loss or paryalsis
- Can’t make a fist
- Funny Bone) spot where nerve rest against medial epicondyle
- Radial Nerve) Damage results in wrist drop, or inabiluty to extend wrist.
9
Q
Lumbosacral Plexus
A
- Lumbar and Sacral Plexuses have signifigant overlap
- Create Lumbosacral plexus
- serve mostly the lower limbs
- Also sneds some branches to the abdomen, pelvis, and buttocks
10
Q
Lumbar Plexus
A
- Arises from L1 to L4
- Innervates thigh, abdominal wall, and psoas muscle.
- Important Nerves
- Femoral Nerve) innervates quadriceps and skin of anterior thigh and medial surface of leg
- Obturator Nerve) passes through the obturator foramen to innervate adductor muscles.
11
Q
Sacral Plexus
A
- Arises from L4-S4
- Serves the buttock, lower limb, pelvic structres and perinuem
- Sciatic Nerve
- Longest and thickest nerve of the body
- Innervates hamstring muscles, adducot magnus, and most muslces in leg and foot
- Composes of the Tibial and Common Fibular Nerve
12
Q
Injuries to Lumbosacral Plexus
A
- Femoral Nerve) Damage can be caused by a herniated disc of spine
- Oburator Nerve) Impared nerve can cause pain in the medial thigh
- Sciatical) Stabbing, radiating pain over the course of the sciatic nerve
- Leg cannot be flexed because hamstrings are paralyzed
- Foot and Ankle cannot move at all and drop into permenant plantar flexion called footdrop
- Tibial nerve (of siatic) paralyzes calf muscles
13
Q
Anterolateral Thorax and Abdominal Wall
A
- Ventral Rami of T1-T12 nerves are intercostal nerves that supply muscles of the ribs, anterilateral thorax, and abdominal wall
- Also supply skin
14
Q
Back Innerviation
A
- Innerviated by Dorsal Rami of many branches
- Each branch innervates a stript of muscle
15
Q
Dermatomes
A
- Area of Skin Innercated by a single spinal nerve
- all spinal nerves except C1 innervates the skin in some way
- In patients with spinal chord injures damaged nerves can be pinpointed by determining damaged dermatome
