Spinal Cord - Chapter 16 Flashcards
What are the 2 functions of the spinal cord?
(1) pathway for sensory and motor impulses, and(2) responsible for reflexes
What are the names of the 2 longitudinal depressions on the external surface of the spinal cord?
Posterior median sulcus and anterior median sulcus
What are the 5 parts that make up the spinal cord?
Cervical, Thoracic, Lumbar, Sacral, and COccygeal
Which end of the spinal cord begins to narrow?
inferior end
What is the name of the tapering inferior end of the spinal cord?
conus medullaris
What is the name of the groups of projecting axons inferior to the conus medullaris?
cauda equina
Where is the cauda equina located?
inferior to the conus medullaris
What is located within the conus medullaris?
filium terminale
What is the function of the filium terminale?
help anchor conus medullaris to the coccyx
The spinal cord is protect by?
meninges
Arachnoid mater is what?
real space filled with cerebral spinal fluid
cerebral spinal fluid also fills which space?
the subarachnoid space
What are some characteristics of the Pia Mater? (2)
- adheres directly to the spinal cord
- composed of elastic and collagen fibers
What is the function of the Pia Mater?
suspend and anchor the spinal cord laterally to the Dura Mater
What are 2 regions of the spinal cord?
inner gray matter region and outer white matter region
The inner region of the spinal cord is composed of what?
gray matter
The outer portion of the spinal cord is composed of what?
white matter
What shapes does the inner gray matter take in the spinal cord?
butterfly shape
The anterior horns are composed of what?
cell bodies of the somatic motor neurons
The lateral horns are composed of what?
cell bodies of autonomic motor neurons
Which parts of the spinal cord are lateral horns only located?
T1 - L2
Axons of sensory neurons and cell bodies of interneurons make up which horn?
posterior horn
unmyelinated axons of the gray commissure are the communication route between what?
The right and left side
What does the gray commissure house?
a narrow central canal
Each of the 3 regions of the white is called a what?
funiculus
The white matter of the spinal cord is partitioned into 3 funiculi (regions) called what?
- posterior funiculus
- lateral funiculus
- anterior funiculus
How many pairs of spinal nerves are associated with the spinal cord?
31
The spinal nerves contain what types of axons?
motor and sensory axons
Anterior rootlets of the spinal cord merge to form what?
a single anterior root
The anterior root contains what type of axons?
motor axons
The posterior root contains what type of axons?
sensory axon
The spinal nerve splits into branches called what?
rami
Where does the posterior ramus innervate?
deeps muscles and skin of the back
Where does the anterior ramus innervate?
anterior/lateral portions of trunk and upper and lower limbs
Where do the rami communicantes extend?
between the spinal nerve and sympathetic trunk ganglion
What is a dermatome?
a specific segment of skin supplied by a single spinal nerve
All spinal nerves except which one innervates the skin?
C1
Anesthesia in one or more segments of the dermatome map could indicate
potential spinal nerve damage
anterior rami of spinal nerves T1 - T11 are called?
intercostal nerves
Where do the intercostal nerves travel?
in the intercostal space between adjacent ribs
Subcostal nerves which spinal nerves?
T12
Where are the subcostal nerves located?
below the ribs
T1 forms part of which plexus?
brachial plexus
What is the function of the T2 nerves?
innervate intercostal muscles and sensory for axilla and medial surface of arm
What is the function of the nerves T3 - T6?
innervate intercostal muscles and sensory for anterior chest wall
What is the function of the nerves T7 - T12?
innervate intercostal muscles, abdominal muscles, and overlaying skin
What is the nerve plexus?
network of interweaving anterior rami of spinal nerves
What are the 4 principle plexuses?
cervical, trochlear, lumber, sacral plexuses
What is the cervical plexus formed by?
anterior rami of nerves C1 - C4
What do the branches of the cervical plexus innervate?
anterior neck muscles and the head shoulders and neck
What does the phrenic nerve innervate?
the diaphragm
Brachial nerves supply what part of the body?
the upper limbs
Each brachial plexus is formed by what?
C5 - T1
the pectoral girdle and the entire upper limb of one side are innervated by what?
brachial plexus
The roots of the brachial plexus unite to form which trunks?
superior trunk, middle trunk, inferior trunk
The anterior and posterior divisions of each trunk converge to form what?
3 cords
What are the 3 cords of the anterior and posterior division named?
Posterior, Medial, and Lateral cords
The 3 cords form what?
5 major terminal branches
What are the 5 major terminal branches?
axillary nerve, median nerve, musculocutaneous nerve, radial nerve, ulnar nerve
What does the axillary nerve innervate?
deltoid and teres minor
The anterior forearm muscles and thumb muscles are innervated by which nerve?
median nerve
The musculocutaneous nerve innervates what?
anterior arm muscles
The radial nerve innervates which muscles? (3)
posterior arm muscles, posterior forearm muscles, and brachioradialis
The ulnar nerve innervates what?
anterior forearm muscles
What is the Lumbar Plexus formed by?
anterior rami of spinal nerves L1 - L4
The Lumbar Plexus is subdivided into anterior and posterior divisions, what is the main nerve of the posterior division?
femoral nerve
What does the femoral nerve innervate?
anterior thigh muscles
The Lumbar Plexus is subdivided into anterior and posterior divisions, what is the main nerve of the anterior division?
obturator nerve
The obturator nerve innervates what?
medial thigh muscles
The Sacral Plexus is formed from what?
anterior rami of spinal nerves L4 - S4
The Lumbar and sacral plexuses together are also called what?
lumbosacral plexus
The largest, longest nerve in the sacral plexus and the body is the
Sciatic nerve
What are the 2 divisions that make up the sciatic nerve?
Tibial division and common fibular division
What are the main branches of the sciatic nerve?
tibial nerve and common fibular nerve
The common fibular nerve includes which nerves?
deep fibular nerve and superficial fibular nerve
The posterior thigh muscles, posterior leg muscles, and plantar foot muscles are innervated by which nerve?
tibial nerve
The common fibular nerve innervates what?
short head of biceps femoris
which muscles are innervated by the deep fibular nerve?
anterior leg muscles and dorsum foot muscles
superficial fibular nerve innerves which muscles?
lateral leg muscles
What are reflexes?
rapid, autonomic, involuntary reactions of muscles to a stimulus
To initiate a response to sensory input, what is required?
stimulus
What 2 things does a rapid response require?
- few neurons involved
- minimal synaptic response
What does an involuntary response require?
no intent or pre-awareness of the reflex
What is the reflex arc?
the neural wiring of a single reflex
What is the pathway of a reflex arc?
a PNS receptor —> communication with CNS —> ends in a peripheral effector
A reflex arc may be:
- ipsilateral or contralateral
- monosynaptic or polysynaptic
- ipsilateral and polysynaptic
Ipsilateral
same side
contralateral
opposite side
Monosynaptic
one synapse
Polysynaptic
2 or more synapses
The stretch reflex has what type of reflex arc?
monosynaptic
Muscle stretch is monitored by a stretch receptor called what?
muscle spindle
What does a stretch stimulus result in?
muscle reflexively contracting
The Golgi tendon reflex has what type of reflex arc?
polysynaptic
What does the Golgi tendon reflex trigger?
muscle relaxation
The withdrawal reflex has what type of reflex arc?
polysynaptic
The withdrawal reflex triggers what?
flexor muscles to contract in response to stimulus
The crossed extensor has what type of reflex arcs?
polysynaptic and contralateral
What does the crossed extensor trigger?
opposite leg of withdrawal reflex to respond to stimulus
