Ch. 12: The Spine Flashcards
what receives sensory input from receptors?
both brain and spinal cord
both the brain and spinal cord contain ___ centers
reflex
both the brain and spinal cord send motor output to ___
effectors
what is a reflex?
rapid, autonomic response triggered by small stimuli
spinal reflexes are controlled by
the spinal cord
spinal reflexes function without input from the
brain
a CS of the spinal cord has outer __ matter and inner __ matter
white; grey
the adult spinal cord is __ cm
45
the spinal cord ends at
L1-L2
the spinal cord has how many nerves?
31
how many cervical nerves?
8
how many thoracic nerves?
12
how many lumbar nerves?
5
how many sacral nerves?
5
how many coccygeal nerves?
1
structure and location of conus medullaris
cone-shaped end of spinal cord at L1-L2
what is the Filum terminale? Function?
area from tip of conus medullaris to S2. Provides longitudinal support to spinal cord
what is the Cauda equina (horse tail)?
the extended anterior and posterior roots of L2-S5 and the filum terminale
___ pairs of spinal nerves arise from __ spinal cord segments
31; 31
names of spinal nerves are designated by __ and __
region and number
C1 nerves runs ___ the 1st cervical vertebra
above
all vertebrae other than C1 are named for the vertebra ___ (above/below)
above
white matter is made of
myelinated and some unmyelinated axons
gray matter is made of (3)
neuron cell bodies, neuroglia, unmyelinated axons
the central canal contains
CSF
do spinal nerves have axons of sensory or motor neurons?
both!
anterior root contains
axons of motor nuerons
posterior root contains
axons of sensory neurons
posterior root ganglion contains
cell bodies of sensory neurons in posterior root
how many spinal meninges are there? What are they?
- dura matter
- arachnoid matter
- pia matter
in general, what are spinal meninges?
specialized membranes surrounding the spinal cord and connected to cranial meninges
what are the functions of the meninges?
- stability
- shock absorption
- carry blood supply (O2, nutrients, waste)
structure of dura matter
tough, dense collagen fibers running lengthwise to the spinal cord
structure of arachnoid matter
arachnoid membrane of simple squamous and subarachnoid space between AM and pia matter
structure of pia matter
meshwork of elastic and collagen, anchored to neural tissue
the subaracnoid space contains what three things? Funtions of each?
- arachnoid trabeculae – collagen and elastic that anchor to pia
- CSF – shock absorption, diffusion of gas, nut, etc
- blood vessels
where is the epidural space and what is it made of?
between dura and vertebrae; areolar, blood vessels, adipose
what is a lumbar puncture/spinal tap?
taking out sample of CSF
Where is needle inserted in lumbar puncture?
into subarachnoid space, lumbar region below conus medullaris
why is a spinal tap done below conus medullaris?
to avoid spinal cord and thus reduce risk of damage
what are nuclei in grey matter?
functional unit of neuron CB
function of sensory nuclei
receive and relay sensory information
function of motor nuclei
issue motor commands to effectors
gray commissures contain axons that ___
axons that cross from sides to side in the spinal cord
where are gray commissure located?
posterior and anterior to the central canal
white matter is organized in __, which are bundles of __ in CNS
tracts; axons
ascending tracts carry __ information in __ columns
sensory; posterior
descending tracts carry __ commands in __ columns
motor commands; anterior columns
what are the 3 connective tissue layers surrounding the spinal nerves?
- epineurium
- perineurium
- endoneurium
what is the epineurium?
outermost layer; dense network of collagen fibers
what is the perineurium?
middle layer; separates nerve into fascicles
what are nerve fascicles?
bundles of axons
what is the endoneurium
innermost layer; surrounds individual axons
arteris and veins go through the ___ and branch in the ___, and capillaries enter the ___
epineurium, perineurium, endoneurium
each spinal nerve divides into two ___
rami
posterior ramus is responsible for __ (3)
muscles, joints, skin of back
anterior ramus is responsible for __ (3)
lateral and anterior trunk, limbs
which spinal nerves carry out motor output of sympathetic ANS? (Fight/Flight)
T1-L2
what is a dermatome?
specific bilateral area of skin supplied by a pair of spinal nerves
what nerve usually lacks a sensory branch? What does it supply when present?
C1; scalp with C2 and 3
the face is monitored by which nerve?
CN V
are dermatome boundaries distinct and absolute?
no, there is overlap
which virus causes shingles and chickenpox?
vericella-zoster (herpes)
the herpes VZV virus acts on ____ and ____
neurons in posterior roots and sensory ganglia
what causes shingles?
it lies dormant in anyone who has had chickenpox and trigger is unknown
sensory information is collected from ___ and delivered to ___ in the spinal cord
periphery; sensory nuclei in spinal cord
the sympathetic nerve collects sensory information from __
visceral organs
the anterior ramus collects sensory information from __ (3)
ventrolateral body surface, body wall, and limbs
the posterior ramus collects sensory information from __
skin and skeletal muscles of the back
the posterior root carries information from __
spinal cord
the anterior root contains axons of the __ and __
somatic, visceral motor neurons
the spinal nerve forms at junction of __ and ___
anterior and posterior roots
the posterior ramus carries contains ___ that carry info to _-
somatic/visceral motor fibers to skin/skeletal muscles of back
the anterior ramus carries information to the __, __, and __
ventrolateral body surface, body wall, limbs
what is the white ramus communicans?
short branch with preganglionic visceral motor fibers to sympathetic ganglia
what is the grey ramus communicans?
postsynaptic fibers to glands/ smooth muscle
sympathetic nerve carries ____ fibers to __
pre/postsynaptic ; thorarcic cavity
what is a nerve plexus?
complex, interwoven nerve network
when is the nerve plexus formed?
during development
how is are nerve plexuses made?
anterior rami of adjacent spinal nerves blend fibers to form plexuses
what are the 4 major plexuses?
- cervical plexus
- brachial plexus
- lumbar plexus
- sacral plexus
the cervical plexus supplies the
neck and diaphragm
the brachial plexus supplies the
pectoral girdle, upper limb
the sacral plexus supplies the
pelvic girdle, lower limb
the cervical plexus is formed by the
anterior rami of C1-C5
the phrenic nerve is formed by
C3 - C5
the phrenic nerve supplies entire nerve supply to
the diaphragm
most nerves of brachial plexus come off ___ and a few originate at the ___
cords; trunks
what are the 5 major brachial plexus nerves?
- musculocutaneous nerve
- median nerve
- axillary nerve
- radial nerve
why is cutaneous nerve distribution to wrist and hand clinically important?
nerve damage can be precisely localized by testing sensory function of the hand
the lumbar and sacral plexuses are formed from
lumbar and sacral segments of spinal cord
the lumbar plexus is formed from the
spinal nerves T12-L4
what is the lumbosacral trunk?
L4 branches contribute to sacral plexus
the sacral plexus is formed by the
spinal nerves L4-S4
what is the sciatic nerve? To which plexus does it belong?
largest, longest nerve in the body. Sacral plexus
what are the 4 nerves supplying the foot and ankle?
- saphenous
- sural
- common fibular
- tibial
what are neural pools?
functional groups of interconnected neurons
what 2 things may neural pools include?
- neurons of various parts of the brain
2. neurons of specific part of CNS
what element of a neural pool reflects its function?
pattern of interaction
the most complex circuits of neural pools are found in the
brain
the simplest circuits of neural pools are found in the
PNS and spinal cord
the simple circuits of neural pools control__
autonomic responses and reflexes
what are the 5 common patterns of neural interaction?
- divergence
- parallel processing
- seriel processing
- reverberation
- convergence
describe divergence
spread information from one neuron/neural pool to several
what does divergence allow for?
broad distribution of specific input
describe convergence
several neurons meet on the same postsynaptic neuron
why can motor neurons experience both conscious and unconscious control?
convergent neural circuits
what is an example of convergence?
voluntary adjustment to breathing
describe parallel processing
several neurons processing the same information simultaneously
what has to happen before parallel processing can occur?
divergence
describe serial processing
transfer of information in steps (1 neuron/pool to the next)
give an example of serial processing
information moving from one part of the brain to the next
describe reverberation
a collateral braches reaches back to the source of the impulse and stimulates it to continue
reverberation involves what type of loop?
positive feedback
reverberation continues until
synaptic fatigue, of inhibitor
reflexes preserve ___ through rapid ___ to organs/systems
homeostasis; adjustments
what are the 5 parts of a reflex arc?
- stimulation of a receptor
- activation of sensory neuron
- information processing in CNS
- activation of motor neuron
- response of peripheral effector
a receptor can be ___ or ___. What do they detect?
specialized cell, or dendrites of sensory neuron. Chemical, physical changes
in the 2nd step of reflex arc, the stimulation of dendrites causes ___, which induces action potentials in sensory neurons. The signal then enters the spinal cord through __
graded potential; sensory neurons; posterior root
in the 3rd step of reflex arc, sensory neurons release __ the induces a ___ postsynaptic potential at the ___
neurotransmitter; excitatory; interneuron
what two things do interneurons do once given an excitatory potential?
create action potentials of motor neurons and send out pain to CNS
motor neurons relese __ that stimulates __ to respond
neurotransmitters; effectors
what 4 things classify reflexes?
- development (innate/acquired)
- nature of response (somatic/visceral)
- complexity of circuit (mono/poly synaptic)
- processing site (Brain or spine)
what are innate reflexes?
basic neural impulses youve had since birth
innate reflexes appear in a predictable sequence from __ to __
simplest to most complex
what are acquired reflexes?
rapid automatic learned motor responses that enhance with repetition
what are somatic reflexes?
involuntary control of skeletal muscles
what is an example of somatic reflex?
withdrawal reflex
what are visceral reflexes?
control involuntary effectors (Smooth, cardiac, glands, glands, adipose tissue)
monosynaptic reflexes involves sensory neuron synapses ___ with motor neurons
directly
polysynaptic reflexes involve sensory neuron synapses ___ with motor neuron
indirectly
which synaptic reflexes have interneurons?
polysynaptic
are mono or polysynaptic reflexes faster?
monosynaptic
processing of the spinal reflexes occurs in the
spinal cord
intersegmental reflexes involve ___ of spinal cord
multiple segments
processing of cranial reflexes occurs in the
brain
what is the best know monosynaptic reflex?
stretch reflex
the stretch reflex automatically regulates __
skeletal muscle length
what stimulus activated stretch reflex?
increasing muscle length
what is the response of the stretch reflex?
to contract muscle
give an example of the stretch response?
patellar reflex
____ act as the sensory receptors for stretch reflex
muscle spindles
muscle spindles are made of
intrafusal muscle fibers
what are intrafusal muscle fibers?
bundles of small, specialized skeletal muscle fibers
intrafusal muscle fibers are supplied by __ neurons
both sensory and motor
muscle spindles are surrounded by muscle fibers that maintain ___ and can __ the whole muscle
muscle tone; contract
the ___ motor neuron innervates each muscle spindle
gamma
gamma motor neurons alter __ in intrafusal fibers; allowing CNS to increase/decrease ___
tension; muscle tone
stretched length stimulates ___ from __
more frequent action potentials from sensory neuron
compressed length stimulates __
inhibition of sensory neuron ; motor neuron not stimulated, decrease muscle tone
postural reflexes function
help maintain normal, upright position
balance is maintained by many muscle groups doing what?
working in opposition
leaning forward stimulates stretch receptors in __ which __
calf muscles; contract to pull you back
postural adjustments are usually
unconscious
strongest withdrawal reflexes are stimulated by
painful stimuli
withdrawal reflexes can be stimulated by
stimulus from touch or pressure
withdrawal reflexes are versatile because
sensory neurons activate many pools of interneurons
distribution and strength of response depend on
intensity and location of stimulus
flexor reflex is a type of __reflex
withdrawal
flexor reflex affects
muscle of a limb
give an example of flexor reflex
pain stimulus of grabbing hot pan
sensory neurons in the flexor reflex activate __ in the spinal cord
interneurons
interneurons in the flexor reflex stimulate motor neurons in __ resulting in ___ and ___
anterior gray horns; contraction of flexor muscles and reciprocal inhibition
what is reciprocal inhibition?
keeps extensors relaxed (blocks opposition)
stretch and withdrawal reflexes use ___ reflex arcs; which means sensory and motor are on __ side of the body
ipsilateral; the same
crossed extensor reflexes involve __- reflex arcs
contralateral
contralateral reflexes involve
an additional motor response occurs on the opposite side of the stimulus
crossed extensor reflexes are coordinated with __
flexor reflexes
in crossed extensor reflexes: flexion of affected side is accompanied by __
extension on the opposite side
give an example of crossed extensor reflexes
step on something sharp, before flexor lifts hurt foot, crossed extensor reflex straightens opposite limb to hold the weight
what reflexes control autonomic actions involved in complex movements (walking and running)
polysynaptic reflexes
what are the five properties of the polysynaptic reflexes?
- involve pools of interneurons which may be excitatory / inhibitory
- involve multiple spinal segments that may activate muscle groups in many areas
- involve reciprocal inhibition that coordinates movement and reduces resistance
- have reverberating circuits that prolong motor response
the ____ can facilitate or inhibit motor neurons / interneurons involved in a reflex
brain
facilitation is called
reinforcement
___ maneuver facilitates patellar reflex
Jendrassik
biceps, triceps, ankle-jerk reflexes are ___ reflexes that are each controlled by specific ____
stretch ; spinal segemnts
the babinski reflex involves
stroking the lateral side of sole triggers extension of hallux and spreading of toes
the babinski reflex occurs due to
lack of inhibition by descending moror fibers
the babinski response disappears as
descending pathways develop
what is the plantar reflex?
in adults, stroking bottom lateral side of foot causes toes to curl
what is the abdominal reflex?
stroking of skin produces reflexive twitch an ab muscles; moving navel towards stimulus
the abdominal reflex depends on facilitation of
descending tracts
