1. Spinal Nerves Reflexes

2. Spinal Nerves Reflexes
Objectives:
Learn the structure of a spinal nerve
Learn the branches of a spinal nerve
Learn the four plexuses in the body and what they innervate
Differentiate between intrinsic and acquired reflexes
Learn the basics of a stretch reflex arc

3. Spinal Nerves Gray Matter Ventral Horns Dorsal Horns Spinal Nerve
Covered by perineurium
Exits via IVF
Spinal nerves have several branches

4. Spinal Nerves

5. Spinal Nerves The two main branches of a spinal nerve are the...
Dorsal Ramus
Innervates the postural muscles of the back and the skin of the back
Ventral Ramus
Ventral rami form plexuses

6. Spinal Nerves A Plexus is a complicated interlacing nerve network
There are four plexuses in the body:
The Cervical Plexus: C1-C4
The Brachial Plexus: C5-T1
The Lumbar Plexus: L1-L4
The Sacral Plexus: L4-S4
All plexuses give rise to named nerves. ONLY VENTRAL RAMI form plexuses

7. Spinal Nerves Hilton's Law:
The nerves that innervate a joint also innervate the muscles that move the joint and supplies sensation to the skin around the joint.

8. Spinal Nerves
Cervical Plexus: From the ventral rami of C1-C4 spinal nerve roots
Superficial Branches:
Lesser occipital (C2, C3)
Greater Auricular (C2, C3)
Trans. Cervical (C2, C3)
Supraclavicular (C3, C4)

9. Spinal Nerves
Cervical Plexus: From the ventral rami of C1-C4 spinal nerve roots
Deep Branches:
Ansa Cervicalis (C1-C3)
Phrenic Nerve (C3-C5)

10. Spinal Nerves Brachial Plexus Every anatomy student's nightmare.
A complicated mess of nerves that arise from C5- T1
We'll break it down from proximal to distal:
And no, you won't be responsible for every nerve!

11. Spinal Nerves Brachial Plexus:
REAL (5) TEXANS(3) DRINK(6) COLD(3) BEER(5)

12. Spinal Nerves Brachial Plexus:
Long Thoracic Nerve (C5- C7) Innervates Serratus Anterior
Can be cut during mastectomy
“Winged Scapula”

13. Spinal Nerves Brachial Plexus:
Axillary Nerve (C5, C6): Innervates Deltoid, Teres Minor
Can sometimes be damaged in childbirth
Erb Duchenne's Palsy
“Waiter's Tip”

14. Spinal Nerves Brachial Plexus: Musculocutaneous Nerve (C5-C7)
Innervates the muscles of the Brachium
Also implicated in Erb Duchenne's Palsy

15. Spinal Nerves Brachial Plexus:
Median Nerve (C5-T1): Innervates muscles of the anterior forearm; flexors of the wrist and hand.
Implicated in Carpal Tunnel and Pronator Teres syndrome

16. Spinal Nerves Brachial Plexus:
Radial Nerve (C5-T1): Innervates the entire musculature of the posterior brachium and antebrachium
All extensors of the elbow, wrist, and hand are innervated by the Radial nerve.

17. Spinal Nerves Brachial Plexus:
Ulnar Nerve (C8, T1): Innervates the majority of the intrinsic muscles of the hand and thumb.
“Funny Bone”

18. Spinal Nerves Lumbar Plexus (L1-L4)
Responsible for the innervation of the superior aspect of the lower limb.

19. Spinal Nerves Iliohypogastric (L1): Skin of the upper abdomen
Ilioinguinal (L1): Skin of the lower abdomen
Genitofemoral (L1,L2): Cremasteric reflex in males, mons pubis and labiae majora in females
Femoral (L2, 3, 4): Hip flexors, knee extensors
Obturator (L2, 3, 4): Adductors of the hip

20. Spinal Nerves
Sacral Plexus: Responsible for innervation of the posterior and distal lower extremity.
Innervates hip extensors and knee flexors, movers of the foot and ankle

21. Spinal Nerves Sciatic Nerve: L4-S3 Largest nerve in the body
Doesn't directly innervate anything.
Has no pain fibers
“Sciatica” is actually nerve root pain and is often mis-diagnosed.
Gives rise to two branches:
Tibial and Common Fibular nn.

22. Spinal Nerves Tibial Nerve: L4-S3
Posterior leg muscles, plantar flexors of the foot and ankle. Skin of posterior leg, sole of foot
Sensory supply to skin of posterior leg

23. Spinal Nerves Common Fibular: L4-S2 Has two branches;
Superficial Fibular
Innervates the muscles of the lateral cruris
Responsible for eversion and plantar flexion of the foot
Deep Fibular
Innervates the muscles of the anterior cruris
Responsible for Dorsiflexion of the foot

24. Spinal Nerves

25. Spinal Nerves Dermatomes:
An area of skin innervated by a single spinal nerve.
Mapped out with great accuracy
An excellent clinical tool to evaluate the level of injury in a patient

26. Spinal Nerves Motor endings and motor activity:
The only things I want you to know...
Acetylcholine is the neurotransmitter used to move muscles
Acetylcholinesterase breaks down ACH, keeps the muscle from tetany
Myasthenia Gravis

27. Spinal Nerves Reflex Arcs: Two general types of reflexes
Intrinsic reflexes
Learned reflexes
All reflexes have a sensory component and motor component.

28. Spinal Nerves Reflex Components: Five components
Receptor: Site of stimulus that starts the reflex
Sensory Neuron: Carries the stimulus information to the spinal cord
Integration Center: Where the sensory information gets transferred to the motor component of the reflex. Usually in the spinal cord. Reflexes will either be monosynaptic or polysynaptic. Simple reflexes are monosnaptic.
Motor Neuron: Carries information from the integration center to the effector organ
Effector: Muscle fiber or gland that responds to reflex impulses
If reflexes act on skeletal muscle it's a somatic reflex

29. Spinal Nerves Stretch reflex:
The Golgi Tendon Organs and Muscle Spindle Cells are responsible for this reflex
The stretch reflex functions to keep us upright without our having to think about it
As the Muscle Spindles are stretched, the associated muscle is stretched. This information is sent to the spinal cord to tell the associated skeletal muscle to contract.
As the muscle contracts, the antagonist muscle relaxes (reciprocal inhibition)

30. Spinal Nerves
Questions?