Spinal Cord Anatomy Quiz

Introduction

• The chapter focuses on identifying and describing the spinal cord and spinal nerves.
• It details the functions of the spinal cord and spinal nerves and how they manage homeostasis.
• It explains spinal reflex arcs.

Functions of the Spinal Cord

• Processes reflexes.
• Integrates EPSPs and IPSPs.
• Conducts sensory impulses to the brain and motor impulses to effectors.

Spinal Cord Anatomy

• The spinal cord is protected by bone (vertebrae), connective tissue (meninges), and cerebrospinal fluid.

Protection of the Spinal Cord

• Protected by bone (vertebrae).
• Protected by connective tissue (meninges).
• Protected by fluid (cerebrospinal fluid).

Meninges

• The meninges are composed of three layers.
• Dura mater
• Arachnoid mater
• Pia mater

External Anatomy of the Spinal Cord

• The spinal cord begins as an extension of the medulla oblongata at the foramen magnum and ends at the level of L2.
• The spinal cord has two enlargements, one in the cervical area (C4-T1) and another in the lumbar area.
• Cervical enlargement deals with sensory input and motor output to the upper extremities.
• Lumbar enlargement deals with motor output and sensory input to and from the legs.
• The spinal cord has a conus medullaris from which the filum terminale arises to anchor the cord to the coccyx.
• The cauda equina are the roots of the lower spinal nerves that angle down alongside the filum terminale.

External Spinal Cord Anatomy (Roots)

• Two bundles of axons, called roots, connect each spinal nerve to the cord, using rootlets as their smaller bundles.
• The posterior (dorsal) root and rootlets carry only sensory axons to the CNS.
• Each posterior root has a swelling (posterior or dorsal root ganglion), and cell bodies of sensory neurons reside it.
• The anterior (ventral) root and rootlets carry motor neuron axons from the CNS to the muscles and glands.

Epidural Anesthesia

• A common procedure for women in labor.
• A needle is placed between the bones of the posterior spine until it only penetrates the ligamentum flavum while remaining superficial to the dura mater.
• Local anesthetic is used to provide pain relief, even for a cesarean section.

Lumbar Puncture

• A needle inserted into the subarachnoid space to extract CSF, diagnose meningitis and other CNS diseases or to instill a drug.
• CSF and pressure measurements are conducted.

Spinal Nerves (1 of 2)

• Spinal nerves connect the CNS to sensory receptors, muscles, and glands.
• There are 31 pairs of spinal nerves.
• Anterior and posterior roots attach a spinal nerve to the spinal cord.

Connective Tissue Covering of Spinal Nerves

• Each spinal nerve has three layers: epineurium, perineurium, and endoneurium.
• These connective tissue layers support nerve fascicles and individual nerve fibers.

Peripheral Nerves

• Spinal nerves are pathways between the spinal cord and body regions.
• Nerves in fascicles covered by the perineurium and sheathed by epineurium.

Peripheral Nerve Arrangement

• 31 pairs of spinal nerves
• Cervical nerves: 8 pairs (C1-C8)
• Thoracic nerves: 12 pairs (T1-T12)
• Lumbar nerves: 5 pairs (L1-L5)
• Sacral nerves: 5 pairs (S1-S5)
• Coccygeal nerve: 1 pair

Branches of a Spinal Nerve

• Spinal nerves quickly split into rami (branches): anterior ramus, posterior ramus, and rami communicantes.
• Rami communicantes connect to sympathetic ganglia.

Dermatomes

• Certain parts of skin are supplied by specific spinal nerves.
• Dermatomes carry somatic sensory nerve impulses to the brain

Cervical Plexus (1 of 3)

• Supplies skin and muscles of the head, neck, superior shoulder and chest, and diaphragm

Cervical Plexus (3 of 3)

• Deep branches are largely motor and include the phrenic nerve.
• Phrenic nerve supplies the diaphragm

Brachial Plexus (1 of 6)

• Almost the entire nerve supply to the shoulders and upper limbs.
• A lesion of the median nerve can lead to carpal tunnel syndrome.

Brachial Plexus (2 of 6)

• Provides almost the entire nerve supply to the shoulders and upper limbs.

Brachial Plexus (3 of 6)

• Some common injuries to the brachial plexus include Erb-Duchenne palsy (waiter's tip) and median nerve palsy.

Nerve Plexuses

• Long thoracic nerve supplies serratus anterior muscle.
• Injury to the long thoracic nerve results in a winged scapula.

Nerve Plexuses

• Some common injuries to the brachial plexus include erb's palsy and ulnar nerve palsy.

Nerve Plexuses

• Median nerve injury can result in numbness, tingling, and pain in the palm and fingers.
• Carpal tunnel syndrome is a common type of median nerve injury, associated with motions of the hand and typing on a computer keyboard.

Lumbar Plexus (1 of 4)

• Its components include iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves.

Lumbar Plexus (2 of 4)

• Includes components such as iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral and obturator nerves.

Lumbar Plexus (4 of 4)

• The femoral nerve is the largest nerve of the lumbar plexus.
• The obturator nerve supplies the adductor muscles of the hip.

Sacral Plexus

• The sciatic nerve is the largest nerve in this plexus.

Sacral Plexus and Coccygeal Plexus

• Composed of the S4, S5, and coccygeal spinal nerves.
• The components include the superior and inferior gluteal nerves and the nerve to the quadratus femoris and inferior gemellus

Sacral Plexus (2 of 6)

• Contains the tibial and common fibular nerves (part of the sciatic nerve), and other, smaller nerves.

Sacral Plexus (5 of 6)

• The sciatic nerve is composed of the tibial and common fibular nerves.

Spinal Cord Physiology

• White matter tracts conduct nerve impulses to and from the brain.
• Gray matter receives and integrates information used in spinal reflexes.

Sensory and Motor Tracts

• Various tracts in the white matter of the spinal cord conduct sensory and motor information.

Reflexes and Reflex Arcs

• A reflex is a speedy, involuntary response to a stimulus.
• Reflexes use the gray matter of the spinal cord as an integrating center.

Reflexes Interactions Animation: General Components of a Reflex Arc

• Sensory receptors respond to stimuli producing a generator or receptor potential
• Sensory neuron carries impulses from receptor to integration center.
• Integrating center (within CNS) relays impulse from sensory to motor neuron.
• Motor neuron transmits impulses to effectors.
• Effectors are muscle or glands responding to motor impulses.

Reflex Arcs: Vocabulary Terms

• Ipsilateral: same side; Contralateral: opposite side; Monosynaptic: one synapse
• Polysynaptic: multiple synapses; Reciprocal innervation: simultaneous contraction of one muscle, and relaxation of its counterpart.

Stretch Reflex

• Causes a muscle to contract due to being stretched.
• The sensory receptor is the muscle spindle.
• Sensory neuron axons are excited by being stretched and transmit impulses to the spinal cord.
• A motor neuron stimulates the same muscle and relieves the stretching (the effector).
• Antagonistic muscles have reduced activity during the reflex.

Tendon Reflex

• Causes a muscle to relax as a response to a stretching stimulus on the tendon.
• The sensory receptor is the Golgi tendon organ.
• The sensory neuron axons transmit impulses to inhibitory interneurons located in the spinal cord.
• Inhibitory interneurons inhibit the motor neuron activity to the muscle attached to the same tendon.
• Extensor muscles are activated throughout this reflex, which relieves excess tension on the tendon.

Flexor (Withdrawal) Reflex

• Causes a limb to withdrawal in response to stimuli that causes pain or injury.
• Interneurons transmit impulses to motor neurons involved in flexor muscle contraction.
• Impulses to flexor muscles are activated, which withdraws the affected limb.
• This causes reciprocal innervation with antagonist muscle inhibition.

Crossed-Extensor Reflex

• Helps maintain balance during a withdrawal reflex.
• Contraction of these muscles balances opposing forces.
• Opposite limbs are activated—flexion in one limb accompanies extension in the other limb.

Reflexes

• Important spinal reflexes, such as the patellar reflex and the Achilles reflex, are discussed.

Reflexes

• The Babinski reflex, a crucial diagnostic reflex, is covered

Disorders (1 of 4)

• Traumatic injuries can lead to monoplegia, paraplegia, hemiplegia, and quadriplegia.

Disorders (2 of 4)

• The extent of paralysis after a spinal cord injury depends on the location of the injury.
• The severity of the injury can result in loss of function from neck down or varying degrees of arm and chest muscle control.

Damage to the Cord

• "Transection" damages ascending and descending spinal cord tracts (partially or completely).
• Transection may occur in a vehicle or diving accident, leading to the occurrence of paralysis depending on the injury's location.

Disorders

• Spinal cord compression (caused by bone, blood, pus, tumor, or ruptured disk).
• Degenerative diseases (multiple sclerosis and amyotrophic lateral sclerosis [ALS].
• Shingles—caused by herpes zoster virus, resulting in painful, skin discolorations and blisters
• Poliomyelitis—caused by poliovirus, resulting in paralysis.

Test your knowledge on spinal cord anatomy, functions, and related medical procedures. This quiz covers important topics such as the meninges, spinal nerve pairs, and lumbar punctures. Ideal for students in anatomy or medical courses.