Spinal Nerves Reflexes

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

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

Spinal Nerves

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

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

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.

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)

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

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!

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

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

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”

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

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

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.

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

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

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

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

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.

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

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

Spinal Nerves

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

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

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

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

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)

Spinal Nerves Questions?