Chapter 13: The Spinal C13: The Spinal Cord and Nerves and Reflexes
How many neurons are typically found in an ascending pathway between the receptor and the brain?
3
How many spinal nerves are there in order from superior (top) to inferior (bottom)?
8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal
How many spinal nerves are in each region of the spinal cord in order from superior to inferior?
8,12,5,5,1
What is a nerve?
A cord of nerve fiber bundles bound together by connective tissue
What is a reflex?
A stereotyped, involuntary response to a stimulus
What is a muscle spindle?
A type of stretch receptor embedded in skeletal muscle
In which disease does sclerosis of the lateral spinal cord occur, with destruction of motor neurons?
Amyotrophic lateral sclerosis
Where does the spinal cord arise from the medulla oblongata?
At the foramen magnum
What is the white matter of the spinal cord?
Bundles of myelinated and unmyelinated axons found superficial to the gray matter
Choose all that are nerve plexuses of the body.
Cervical Lumbar Sacral Brachial
The anterior rami of spinal nerves form which nerve plexuses?
Cervical, lumbar, sacral
The spinal cord contains ascending and descending nerve fibers that send information between the CNS and the periphery. This illustrates which function of the spinal cord?
Conduction
Which tract will have its origin and destination of opposite sides of the body?
Contralateral
In which reflex does a contralateral extensor muscle contract?
Crossed extension
What factor accounts for the fact that the right side of the brain communicates with the left side of the body, and vice versa?
Decussation
What is an area of skin innervated by a spinal nerve called?
Dermatome
Within the spinal cord, which tracts carry motor signals down from the brain?
Descending
Place the meninges in order from superficial (at the top) to deep (at the bottom).
Dura Mater Arachnoid Mater Pia mater
True or false: Severing a sensory nerve root will completely deaden sensation from a dermatome.
False
In a sensory pathway, which neuron detects the stimulus and transmits the signal to the spinal cord or brainstem?
First order
Where is the origin of sensory signals carried by the cuneate fasciculus?
From vertebra T6 and up
Which tract will have its origin and destination on the same side of the body?
Ipsilateral
In an adult, the spinal cord ends at which vertebra?
L1
In descending tracts, which motor neuron innervates the target organ?
LOWER
In descending pathways, the upper motor neurons synapse with which motor neurons in the brainstem or spinal cord?
Lower
Which are a series of fibrous connective tissue membranes covering the central nervous system?
Meninges
A reflex arc that consists of only one synapse between two neurons is called a(n) ______________ reflex arc.
Monosynaptic
Which type of reflex arc consists of only an afferent neuron and an efferent neuron?
Monosynaptic
Within the spinal cord, what type of information do the descending tracts carry?
Motor
What is a reflex involving one or more interneurons called?
Polysynaptic
Choose all that are functions of the spinal cord.
Reflexes Locomotion Conduction
A reflex that occurs in response to excessive tension on a tendon is called a(n) _________ reflex.
Tendon
A reflex in which a contralateral extensor muscle is contracted is called a ________ extension reflex.
crossed
Because the nerve tracts of the spinal cord undergo ___________ , the right side of the brain communicates with the left side of the body, and vice versa.
decussation
A reflex involving one or more interneurons is a monosynaptic reflex.
false
In a sensory pathway, the ____________ order neuron detects the stimulus and transmits the signal to the spinal cord or brainstem.
first
Which nerve tracts do not decussate?
ipsilateral
Fibers from the cuneate fasciculus end on the which side of the medulla oblongata?
isplateral
Which motor neurons (which are the motor neurons connecting the brainstem and spinal cord to muscle fibers) of the descending pathway innervate skeletal muscle?
lower
The poliovirus destroys which neurons in the brainstem and anterior horn of the spinal cord?
motor
A _________ is a cordlike organ composed of numerous nerve fibers (fascicles) bound together by connective tissue.
nerve
What does contralateral mean?
on the opposite side of the body
What does ipsilateral mean?
on the same side of the body
Which pathways are made up of three neurons?
sensory
Which reflex occurs in response to excessive tension on a tendon?
tendon
How many neurons are found in a descending tract?
two
In descending pathways, which motor neurons have their somas in the cerebral cortex or brainstem?
upper
The matter that is composed of myelinated and unmyelinated axons and is superficial to the gray matter of the spinal cord is called_______ matter.
white