Spinal Cord CH 13
Terms in this set (70)
Length of spinal cord
Extends from foramen magnum to L1
Layers of meninges surrounding spinal cord from superficial to depp
Dura mater, arachnoid mater, pia mater
Space around the spinal cord that consists of fat. Between dura and vertebral column. Allows the administration of drugs into the space (epidural anesthesia).
Dorsal root ganglion
Unipolar sensory neuron
collection of nerve cell bodies in the peripheral nervous system
Sensory Afferent info
Always goes into the dorsal side of the spinal cord
Motor efferent info
Always exists ventral root of spinal cord
Where is the cell body of the sensory neuron located?
Dorsal Root Ganglion
How are tracts named?
By where they start and end
consist of axons that conduct nerve impulses toward the brain
How are tracts (white matter) organized?
Organized into dorsal, ventral, and lateral columns.
How is gray matter organized?
Organized into dorsal and ventral horns
Sensory input (afferent, ascending)
Motor output (efferent, descending)
Tracts carry impulses through descending white columns from the brain.
Direct motor pathway
Motor impulse begins in the pyramidal cell (upper motor neuron) of the precentral gyrus and travels in descending tract to the motor neuron in the anterior gray horn (lower motor neuron)
Lower motor neuron damage, atrophy, loss of reflexes
Upper motor neuron damage, exaggerated deep tendon reflexes, babinski sign.
Braid of interweaving of spinal nerves from different levels to form a particular nerve
How many pairs of spinal nerves are there?
Are spinal nerves part of the PNS or CNS?
Are spinal nerves sensory, motor, or both?
C1-C5, phrenic nerve that supplies the diaphragm
C5-T1, axillary, median (extends thumb, 2nd, and 3rd digits on ventral side), ulnar (extends 4th and 5th digits on ventral side), radial (muscles on dorsal side of arm and hand), and musculocutaneous nerves.
Is there a thoracic plexus?
L1-L4, femoral nerve supplies muscles of the anterior thigh
L4-S4, Sciatic nerve supplies muscles of the posterior thigh and lower leg (hamstrings)
Part of the sacral plexus, innervates the muscles involved in sexual activity and continence.
Area of skin supplied by a specific spinal nerve. Tingling or numbness in a certain area/dermatome can tell you what spinal nerves are specifically affected.
What comes after a dermatome?
Only 1 synapse
2 or more synapses
Receptor and effector are on same side
Receptor and effector on opposite sides
Effector is skeletal muscle. All voluntary
Effector is smooth muscle or cardiac muscle. Involuntary.
Pathway of a reflex
Stretch Reflex Receptor
Muscle Spindle, detects stretching
Stretch Reflex Afferent neuron
Sensory, carry impulses to the spinal cord, enters cord through dorsal root ganglion.
Stretch reflex integration center
Found between sensory and motor, does not include and integration neuron, monosynaptic
Stretch Reflex efferent neuron
Motor, exists through the ventral root
Stretch Reflex Effector
The effector is the skeletal muscle that contracts. Ipsilateral
Patellar Stretch Reflex
occurs when the patellar tendon is tapped and the knee jerks forward in response. Muscle cells in the quadriceps femoris respond to the stretch.
Achilles stretch reflex
occurs when the Achilles tendon is tapped while the foot is dorsiflexed. Gastrocnemius responds.
Golgi Tendon Reflex receptor
Golgi tendon organ. Located within tendon. Detects over contraction
Golgi tendon reflex afferent neuron
Golgi tendon reflex integration
Does include an integration neuron, polysynaptic
If the reflex contains an integration center/neuron, it is...
Golgi tendon reflex Effector
Relaxation, somatic, ipsilateral.
Prevents over stretching
Prevents over contracting
Withdrawal reflex receptor
Nociceptor (pain receptor)
Withdrawal reflex afferent neuron
Withdrawal reflex integration center
Withdrawal reflex efferent neuron
Motor neuron going to muscle
Withdrawal reflex effector
contraction of flexor muscles, ipsilateral,
Crossed extensor reflex
Opposite limb supports body during withdrawal of injured limb
Initiated by skin stimulation
Babinski normal response in adults
Toes curl and pull away
What does a positive babinski sign indicate?
Motor damage, corticospinal tract
What is a positive babinski sign?
Toes fan out, great toe extends.
When is a positive babinski considered normal?
why are all of the reflexes called somatic reflexes
Because they involved skeletal muscle (voluntary).
Examples of autonomic reflexes
Pulling hand off of a hot stove, pupillary reflex, defecation, urination
Why is the pupillary reflex autonomic?
Because it contains smooth muscle
Pupillary reflex receptor
Photoreceptor (rods and cones in retina, optic nerve)
Pupillary reflex afferent neuron
Optic nerve (CN II) carries afferent fibers
Pupillary reflex integration center
The impulse travels to both sides of the midbrain where the nuclei for the oculomotor nerve are located.
Pupillary reflex efferent neuron
Oculomotor nerve (CNIII) carries efferent fibers
Pupillary reflex effector
Constrictor pupillae muscle responds, fibers from medial aspects of each eye cross to the other side, while fibers from the lateral aspect do not cross. Light in one eye causes bilateral response.