-
# Why is the pons refered to as the "bridge"?
-
* pons means bridge
* refers to the many transvers fibers that cross the anterior surface of the pons
-
# Where is the pons located?
-
* anterior to cerebellum
- * inferior to midbrain
- * superior to medulla oblongata
-
# What structur(es) run through the center and anterior part of the pons?
-
* basilar groove made from transvers fibers
* basilar artery that supplies the Circle of Willis
-
# Which direction do the transverse fibers of the pons travel?
-
* towards the cerebellum
* laterally
-
# What structure connects the brainstem to the cerebellum?
middle cerebellar peduncles
-
# Where are the superior cerebellar peduncles locate?
-
* on posterior side of pons
- * medial to the middle cerebellar peduncles
- * only seen if cerebellum is removed
-
# What are the most posterior structures of the pons not including peduncles in order of medial to latera?
-
* median sulcus
- * median eminance
- * sulcus limitans
- * vestibular area
-
# What structure are the facial colliculi expansions of?
inferior ends of the medial eminences
-
# Where do the vestibular areas get their name?
the vestibular nuclei are deep to these structures
-
# All structures of the posterior pons are the anterior wall of what structure?
the 4th ventricl of the brain
-
# What makes up the trapezoid body?
-
* trapezoid body nuclei
* cochlear nuclei fibers of the pontine-medullary junction
-
# Where do the cochlear nuclei fibers of the pontine-medullary junction decussate?
at the trapezoid body of the pons
-
# Where is basal part of pons located?
anterior to the trapezoid body
-
# What does the basal part of the pons contain?
-
* pontine nuclei
- * corticonuclear fibers (synapse elsewhere)
- * corticospinal fibers (synapse elsewhere)
-
# What synapses to the pontine nuclei in the pons?
corticopontine fibers from the cerebral cortex
-
# Where do the transverse fibers of the pons come from?
the pontine nuclei of the basal part of the pons
-
# What is the structure located posteriorly to the trapezoid body of the pons?
the tegmentum
-
# What nuclei are located in the tegmentum of the pons?
-
* vestibular nuclear complexes
- * facial nucleus
- * abducens nucleus
- * spinal nucleus
- * motor nucleus
-
# What does the vestubular nuclear complex of the pons receive information from?
vestibular information from the vestibulocochlear nerve
-
# How many nuclei make up the vestibular nuclear complexes of the pons, and where in the pons are they located?
-
* four nuclei (lateral, medial, superior, and inferior)
* located anterior to the vestibular area of the posterior surface of the pons
-
# Where is the facial nucleus located in relation to trapezoid bodies? What nerve is it connected to?
-
* posterior to trapezoid bodies
* connected to CN VII (the Facial Nerve go figure)
-
# Where is the abducens nucleus of the pons located?
the posterior tegmentum
-
# What do fibers from the facial nerve loop around before synapsing in the facial nucleus?
-
* the abducens nucleus
* they do this and form the facial colliculi
-
# Where is the spinal nucleus of the trigeminal nerve located, and what is its function?
-
* lateral tegmentum of the pons
* responsible for pain and temperature sensations
-
# Where is the motor nucleus of the Trigeminal nerve (CN V) located?
-
* in the posterior lateral tegmentum of the pons
* only located in the mid-pons area.
-
# What are the boundaries of the medulla oblongata?
-
* superior boundary is pons
* inferior boundary is spinal cord
-
# What are the anterior surface structures of the medulla oblongata?
-
* pyramids
- * anterior median fissure
- * decussation of pyramids
-
# Why are the pyramids of the medulla oblongata named so?
-
* their shape
* pyramidal fibers from primary motor cortex travel through here
-
# What is the main structure of the superior lateral surface of the medulla oblongata?
olives
-
# What do the olives of the medulla oblongata contain?
olivary nuclei
-
# What is the function of the olivary nuclei of the medulla oblongata?
accessory pathway of motor control
-
# What are the posterior structures of the medulla oblongata? (does not line 4th ventricle)
-
* vagal triangle
- * hypoglossal triagle
- * gracile tubercles
- * cuneate tubercles
- * posterior median sulcus
-
# What does the posterior median sulcus of the medulla oblongata separate?
the two gracile tubercles
-
# Where are the two cuneate tubercles located?
lateral to the superior parts of the gracile tubercles
-
# What is the function of the gracile and cuneate nuclei?
-
* part of sensory pathways
- * sensory nerves synaps on nuclei here
- * project fibers up to the thalamus
-
# What nucleus of the pons also travels through the medulla oblongata?
the spinal nucleus of the trigeminal nerve (CN V)
-
# Where does the spinal nucleus of the trigeminal nerve run in the medulla?
-
* posterior-lateral
* continuous with the substantia gelatinosa of the spinal cord gray matter
-
# What is the function of the external, or accessory, cuneate nucleus?
sends information into the cerebellum
-
# What three types of olivary nuclei are there?
-
* main inferior...
- * dorsal...
- * medial accessory...
-
# What is the function of the olivary nuclei of the medulla?
send decussating fibers of voluntary movement to the verebellum through inferior cerebellar peduncles
-
# What nuclei run the length of the medulla oblongata?
-
* nucleus ambiguus
- * solitary tract nucleus
- * dorsal nucleus of the vagus
- * hypoglossal nucleus
-
# What is the function of the nucleus ambiguus of the medulla oblongata and what nerves connect to it?
-
* control muscles of the throat
* CN IX (glosopharyngeal), X (vagus), and cranial root of XI (accessory)
-
# What type of sensation does the solitary tract nucleus receive?
visceral
-
# Where does the solitary tract nucleus receive information?
-
* taste from CN VII (facial), IX (glossopharyngeal), and X (vagus)
- * baroreceptors in carotid sinus
- * chemoreceptors in the carotid body
-
# What is the function of the dorsal nucleus of the vagus (CN X)?
-
* control parasympathetic functions of the vagus nerve throughout body
* receives info from solitary tract nucleus
-
# What is the function of the hypoglossal nucleus?
motor nucleus of the hypoglossal nerve (CN XII)
-
# What is the vestibolonuclear complex of the medulla oblongata?
-
* pontine medullary junction
* deals with vestibulocochlear nerve (CN XIII)
-
# What is the function of the anterior and posterior cochlear nuclei of the medulla oblongata?
receive hearing information from the vestibulocochlear nerve
-
What is the function of the cerebellum?
- integrates proprioceptive info with balance and sight info
- sends inhibitory signals to the nuclei of origin of spinal cord and motor complex
- this fine tunes muscle movements
-
What type of movement does the cerebellum help with?
learned motor movement
-
What structure separates the cerebellar hemispheres?
the vermis
-
What are the three lobes of the cerebellum? (one on each side)
- anterior
- middle
- flocculonodular
-
What structure separates the anterior lobe and the middle lobe of the cerebellum?
the primary fissure
-
What structure divides the middle lobe from the flocculonodular lobe of the cerebellum?
postereolateral fissure
-
What is the function of the horizontal fissure of the cerebellum?
- no real function
- separates the superior and inferior portions of the cerebellum
-
What connects the cerebellum to the posterior brainstem?
- superior
- middle
- inferior cerebellar peduncles
-
What type of fibers is are the middle cerebellar peduncles mostly made of?
- afferent fibers
- travels from pons
-
What type of fibers mostly make up the inferior cerebellar peduncles?
- mostly afferent
- travel from pons, medulla oblongata, and spinal cord
-
What type of fibers make up the superior cerebellar peduncles?
- efferent!
- travel to midbrain and thalamus regions
-
What is the name of the internal white matter in the cerebellum?
arbor vitae (tree of life)
-
What layers make up the cerebellar cortex organization?
- Molecular layer
- Purkinje cell layer
- Granular layer
-
What makes up the molecular layer of the cerebellar cortex?
- basket cells
- tengential processes of granular cells
- dendritic tree of the Purkinje cells
- stellate cells
-
What is the function of the basket cells of the molecular layer of the cerebellar cortex?
- connect purkinje cells
- isolate firing of the purkinje cells through inhibiting surrounding purkinje cells
-
What makes up the Purkinje cell layer of the cerebellar cortex?
soma, or cell bodies, of the Purkinje cells
-
What type of neuron are Purkinje cells?
Golgi type I
-
What do purkinje cell axons synapse to?
intercerebellar nuclei in the deep white matter
-
What makes up the Granular layer of the cerebellar cortex?
- granular cells' soma
- Golgi cells
-
Where do granular cell axons travel?
- to the molecular layer of the cerebellar cortex
- they then split into parallel processes
- these run parallel to the cortex
-
What is the function of Golgi cells in granular layer of the cerebellar cortex?
inhibitory interneurons that inhibit cells in the granular layer
-
What type of feedback loop do golgi cells of the granular layer of the cerebellar cortex uses?
negative feedback loop
-
What type of fibers bring afferent info to the cerebellum, usually through inferior and middle cerebellar peduncles?
- climbing fibers
- mossy fibers
-
Where do climbing fibers of the cerebellum come from?
olivary nuclei of the medulla oblongata
-
What do the climbing fibers synapse with, and what kind of reaction do they create?
- purkinje cell dendrites
- direcet excitatory influence
-
Where do mossy fibers of the cerebellar cortex come from?
all other inputs to the cerebellum
-
What is the function of mossy fibers in the cerebellar cortex?
- synapse with excitatory granular cells
- synapse with inhibitory Golgi cells
- prevent granular cells from gettin gtoo excited (overstimulated)
-
What type of effect do the granular cells have on purkinje cells?
excitatory
-
What cells make up efferent fibers of the cerebellum?
purkinje cells
-
How do purkinje cells interact with with granular cells?
- with the parallel processes of granular cells
- 200,000 times per Purkinje cell
-
Where do purkinje cells synapse?
- cerebellar nuclei
- some from flocculonodular lobe exit cerebellum directly
-
What is Hypotonia?
- lack of resistance to pressure and motion
- muscle fibers lose definition
-
What is posture problem caused by cerebellum?
stiff legs and shoulders on one side of lesion
-
What is ataxia?
tremors when trying to do fine movements
-
What is dysdiadochokinesia?
inability to perform alternating movements with regularity and repetition
-
What are reflex disturbances?
reflex movements are much larger and continue for a much longer period than usual
-
What is Nystagmus?
- "dancing of the eyes"
- commonly seen in albino patients
-
What is dysarthria?
explosive speech
-
What is the reticular formation?
- network of nerve cells that runs vertically from the spinal cord to the thalamus
- receives sensory input
- gives off efferent fibers that influence most CNS processes
-
What are the columns of the reticular formation?
- one median column
- two medial columns
- two lateral columns
-
With what structure are the reticular formation columns continuous with inferiorly?
spinal cord gray matter
-
Where is the reticular formation located inside the midbrain, pons, and medulla oblongata?
- midbrain: in tegmentum, posterior to substantia nigra, anterior to cerebral aqueduct
- pons: in tegmentum, posterior to trapezoid body
- medulla: near the center
-
Where do afferent projections of the reticular formation come from?
- spinal cord
- cranial nerve nuclei
- cerebellum
- diencephalon
- corpus striatum
- limbic system
- cerebral cortex
-
Where do efferent projections of the reticular formation go to?
- same as afferent
- autonomic nervous system
- red nucleus
- substantia nigra
- tectum of midbrain
-
What are the functions of the reticular formation on skeletal muscle?
- atin-gravity muscle tone
- reflex activity
- reciprocal inhibition (flexor vs. extensor)
- respiratory muscle control
- emotion-driven control of facial expression muscles
-
What is wrong if you cannot voluntarily smile, but can if a joke is told?
- you have a lesion blocking smile nerves in the facial nerve
- reticular formation is still working
-
How does the reticular formation affect control of somatic and visceral sensations?
- facilitation or inhibition of sensations
- (tones down sensations like pain)
-
What function does the reticular formation have in the reticular activating system?
- sensory filter of arousal (decides what is important enough to wake you)
- differs the states of wakefulness dependant on activity (auto drive vs. bomb squad)
-
What structures does the spinal cord travel in/through?
vertebral canal of vertebral column
-
From what structures does the spinal cord span?
- foramen magnum
- L1 vetebrae
-
Where is the cauda equina located?
below the spinal cord, starting from L1 and ending in the coccyx
-
What is the first direction nerves of the cauda travel off of the spinal cord?
inferiorly in the vertebral canal, towards the vertebrae that the exit from
-
What structures divide the spinal cord into right and left halves?
anterior and posterior median fissures
-
What surrounds the spinal cord?
- meninges, just like the brain
- dura
- arachnoid
- pia
-
Where does the dura mater end in the spinal column?
S2-ish
-
What are the names of connections in the spinal cord between the pia and arachnoid maters?
- ligamentum denticulatum
- thicken between nerve roots gives toothy appearance
-
What is the name of the collapsed in pia mater that meets with arachnoid and dura mater at S2?
filium terminale
-
Where is the filium terminale found in the verterbral column?
conus medullaris (at L1)
-
How many spinal nerve pairs emerge from each spinal segment?
31
-
What are the structures of the gray matter core in the spinal cord?
- anterior horn
- posterior horn
- commissure
-
What types of neuron cell bodies does the anterior horn of the gray matter spinal cord have?
- alpha-efferent
- gamma-efferent
-
What are the properties of alpha-efferent neuron cell bodies?
- large, multipolar cells
- exit via the anterior spinal root
- innervate extrafusal skeletal muscle
-
What are the properties of gamma-efferent neuron cell bodies?
- small, multipolar cells
- exit from anterior apinal root
- innervate the intrafusal muscle fibers of neuromuscular spindle
- detect stretching info
- cause stronger stress responses by constricting more
-
What are the 3 neuron soma bunches of the anterior horn?
- medial group
- central group
- lateral group
-
Where is the medial group of neuron soma of the anterior horn located?
througout the spinal cord
-
What does the medial group of neuron soma in the anterior horn of the spinal cord innervate?
- neck
- trunk
- intercostal
- abdominal muscles
- (muscles around axis of body)
-
Where is central group of neuron soma in of the anterior horn in the spinal cord located?
-
What does the central group soma of the anterior horn of the spinal cord innervate?
- C1-C6: spinal root of accessory nerve (sternocleidomastoid and trapezius)
- C3-C5: phrenic nerves and diaphragm
- L2-S1: lumbosacral plexus (innervation unknown)
-
Where is the lateral group of the neuron soma in the anterior horn of the spinal cord located?
- cervical area
- lumbosacral area
-
What does the latera group soma of the anterior horn of the spinal cord innervate?
-
What type of cells go into the posterior (dorsal) horn of the spinal cord?
mainly afferent axons from the periphery
-
What are the three sections of the posterior (dorsal) horn of the spinal cord?
- substantia gelatinosa
- nucleus proprius
- nucleus dorsalis
-
Where is the substantia gelatinosa of the posterior horn of the spinal cord located?
the apex of the posterior horn
-
What type of cells interact with each other in the substantia gelatinosa?
- afferent PNS fibers
- Golgi type II neurons
- long descending axons from brain
-
What does the interaction of so many neurons in the substantia gelatinosa of the posterior horn of the spinal cord allow?
sensation to be tempered (heightened or dampened) by sensations from other places or the brain
-
what type of sensation does the nucleus proprius detect/receive?
- fine sensation
- proprioception
- resolution
- vibration
-
What does the nucleus proprius receive fibers from?
posterior white column of the spinal cord
-
Where in the vertical aspect of the spinal column is the nucleus dorsalis (Clark's column) found?
from T1 to L3 of spinal cord
-
What type of soma does the nucleus dorsalis have?
- large neurons
- neuromuscular spindles
- Golgi tendon organs
-
What type of sensation does the nucleus dorsalis receive?
- proprioception
- stretching of muscles
-
What is the function of the Gray commissure in the spinal cord?
- connects the right and left halves of the gray matter of the spinal cord
- decussation of nerve fibers
-
Through what structure does the central canal of the spinal cord run down?
the gray commissure of spinal cord
-
What flows through the central canal of the spinal cord?
CSF
-
In what parts of the spinal cord is the lateral horn present?
-
What is the lateral horn of the spinal column made of?
intermediolateral cell group
-
What is the function of the intermediolateral cell group in the lateral horn of the spinal cord?
- they are preganglionic sympathetic neurons
- the preganglionic sympathetic axons come from these soma
- receives signals directly from the brain
-
What is the intermediomedial cell group of S2 to S4 of the spinal cord?
they give rise to the preganglionic parasympathetic fibers of the sacral plexus
-
What does the amount of gray matter in a section of the spinal cord mean?
- directly deals with how much information goes in and out of that area of the spinal cord
- enlargements in areas where info of arms and legs is received
-
What are interneurons (internuncial neurons) of the spinal cord core?
- inhibitory (usually) neurons that link two longer neurons together
- often used in reflex arc to inhibit the action of antagonistic muscle
-
What are the divisions of the white matter in the spinal cord?
- anterior
- posterior
- lateral columns
- white commissures
-
What is the function of the white commissures?
- there is an anterior and posterior one
- connect right and left halves of the white matter of the spinal cord
- they do not cross the gray commissure
-
What are intersegmental nerve fiber tracts?
reflexes that require movement in more than one spinal segment
-
What type of signals do ascending neuronal pathways carry?
- afferent!
- exteroception
- interoception
- proprioception
-
What is exteroception?
- stimulus that comes from outside the body
- ex: punch in the face, eating something sharp
-
What is interoception?
- stimulus that comes from inside the body
- ex: headache
-
What makes up the afferent signal pathway three neuron chain?
- first-order neuron
- second-order neuron
- third-order neuron
- there are some exceptions (more or less neurons)
-
What are the attributes of the first-order neuron in the afferent signal chain?
- stretches from sensory receptor in periphery to spinal cord
- cell body is in posterior root ganglion
- synapses with second-order neuron
-
What are the attributes of the second-order neuron in the afferent signal chain?
- cell body in spinal cord gray matter (sometimes in medulla)
- usually decussate (with very FEW exceptions)
- ascends to the brain
- with third order neuron in the thalamus
-
What are the attributes of the third-order neurons in the afferent signal chain?
- cell body in the thalamus
- sends axons to specific area of cerebral cortex
-
What are the exceptions of the third-order neurons in the afferent signal pathway?
- some branch to give info to the reticular formation
- some participate in a reflex arc
-
What ascending pathway transmits temperature, pain, light touch, and pressure sensation?
- the spinothalamic/ spinoreticular tract
- also called lemniscal system
- deals mostly with crude sensations, no details or data
-
What type of nerve do first-order neurons of the spinothalamic tract come from?
free nerve endings
-
What side of the spinal cord do first-order neurons of the spinothalamic tract synapse?
- the ipsilateral posterior gray horn
- specifically the substantia gelatinosa
-
How do first-order axons divide when entering the spinal cord?
- ascending
- descending branches
- called postereolateral tract of Lissauer
- these interact with neighboring spinal segments
- this spreads sensory info to other dermatomes
-
What is purpose of pain receptors?
make person aware of damaging stimuli
-
What direction do second-order neurons of the spinothalamic tract immediately do?
- decussate at same level of spinal cord
- via the anterior gray and anterior white commissures
-
Which direction do the second-order axons of spinothalamic tract go after decussating?
ascend in the contralateral anteriolateral white column of spinal cord, medulla, pons, and midbrain
-
What name is given to second-order fibers of the spinothalamic tract as they ascend collectively up the medulla?
spinal lemniscus
-
What do spinal lemniscus always refer to?
second-order neurons of the spinothalamic tract that are travelling through the brainstem
-
What does the lateral portion of the anteriolateral white column carry information of?
-
What does the anterior portion of the anteriolateral white column of the spinothalamic tract carry information of?
-
Where do axons of the spinal lemniscus end?
ventral posterolateral nucleus of the thalamus
-
Where do third-order neurons of the spinothalamic tract end?
postcentral gyrus of the cerebrum
-
What type of fibers carry pain sensation in the spinothalamic tract?
- fast pain neurons
- slow pain neurons
-
What is the function of fast pain fibers in the spinothalamic tract?
- ascend directly to the thalamus
- this localizes pain
-
What is the function of slow pain fibers in the spinothalamic tract?
- relay in posterior horn of spinal cord before ascending to reticular formation
- elicits chronic, nauseous, or suffering pain
- pain you can't pinpoint, but have a general feeling of unwellness
- also know as the spinoreticular pathway
-
What is the spinoreticular tract a rare case of how second-order neurons behave?
- they do not decussate!
- travel ipsilaterally
- there are no third order neurons
-
What are the two theories of managing pain?
- Gating theory
- Analgesia system
-
What is the gating theory of pain management?
- strong tactile stimuli can inhibit the pain signals through convergence of neurons in the dorsal gray horn of the spinal cord
- basically: overload the system with all types of receptors will cause pain to be lessoned
-
What is the anlgesia system theory of pain management?
- it releases chemical opiods that descend in rebrospinal tract
- these inhibit spinal neurons that relay pain signals
-
What is the general rule of pain tolerance between men and women?
men can tolerate more pain
-
How do spinovisual reflexes create the correlation of eye reflexes with head movement?
second-order axons of spinal lemniscus branch off and end in superior colliculi of midbrain tectum (spinotectal tract)
-
Where do most pain sensations end?
the somatosensory cortex of the post-central gyrus
-
What part of the nervous system regulates our emotional responses to pain?
cingulate gyrus
-
What part of the nervous system is associated with pain from our internal organs?
insulate cortex
-
What type of sensation do posterior white column tracts transmit?
- fine, discriminitive touch
- pressure
- vibration
- conscious proprioception
-
Where do first-order neurons of the posterior white column tracts begin?
- specialized receptors such as:
- Meissner's corpuscules
- pacinian corpuscules
- neuromuscular spindles
- Golgi tendon organs
-
Where do first-order neurons of the posterior white column tracts travel to?
- directly to ipsilateral posterior white column
- then branch into descending or ascending fibers
-
What nerves of the posterior white column tracts cause the intersegmental reflexes?
- descending fibers of first-order axons
- synapse on spinal cord gray matter neurons
-
What are the two ascending tracts of the first-order neurons of the posterior white column tract?
- Fasciculus gracilis
- Fasciculus cuneatus
-
What side of the spinal cord do first-order fibers of the posterior white column tracts travel to? (ipsilateral or opposite)
ipsilateral side
-
What are the attributes of the fasciculus gracilis?
- runs along entire length of spinal cord
- transmits sensory information from lower limbs, abdomen and lower thorax
-
What are the attributes of the fasciculus cuneatus of the posterior white column tracts?
- only present in upper thoracic and cervical spinal cord
- tranmits sensory info from upper limbs, upper thorax, and neck
-
Where do the axons of the fasciculi gracilis and cueatus end?
- the nuclei gracilis and cuneatus of the posterior medulla oblongata
- synapse on second-order neurons here
-
The soma of the nucleus gracilis and cuneatus are what?
second-order neurons of the posterior white column tracts
-
The soma of the nucleus gracilis and cuneatus give off axons called what?
internal arcuate fibers
-
What are the attributes of the internal arcuate fibers of the posterior white column tracts?
- decussate in the medulla bolongata via sensory decussation
- ascend in the medial lemniscus through medulla, pons, and midbrain
- end in ventral posterolateral nucleus of thalamus
- synapse on third-order neurons
-
What is the spinal lemniscus?
2nd order neuorns of the spinothalamic tract traveling through brainstem
-
What is the medial lemniscus?
2nd order neurons of the fasciculus gracilis and cuneatus tracts traveling through the brainstem
-
What is the lateral lemniscus?
2nd order neurons carrying hearing info traveling through the brainstem
-
What is the Trigeminal lemniscus?
2nd order neurons from the trigeminal nerve tha have their cell bodies in the trigeminal nucleus
-
Where do 3rd order axons of the of the posterior white column tract travel?
- through internal capsule
- through corona radiata
- terminate on postcentral gyrus, primary somatosensory cortex
-
What does the ascending pathway to the cerebellum transmit?
muscle joint proprioceptive data
-
How many ascending pathways from the spinal cord to the cerebellum are there?
4
-
Where do first-order neurons of the ascending cerebellar pathways synapse?
the nucleus dorsalis of the posterior gray horn in spinal cord
-
Where do second order neurons of the ascending cerebellar pathway synapse?
- mossy fibers travel directly from the nucleus dorsalis to the cerebellar cortex
- some synapse with neurons in the olivary nuclei
- from olivary nuclei to cerebellar cortex is third-order fibers, or climbing fibers
-
What info do descending spinalt tracts carry?
- efferent signals from the brain to spinal cord
- allow muscle and glandular activity
-
What is the general course of descending tracts of the CNS?
upper motor neurons to lower motor neurons
-
Where do upper motor neurons start?
- neuronal soma in cerebral cortex (largest amount)
- deep cerebral and brainstem nuclei
-
Where do upper motor neurons synapse in the spinal cord?
anterior gray horn of the spinal cord
-
At what structure in the CNS do many descending neurons decussate?
medulla oblongata
-
Where do lower motor neurons have their soma?
anterior gray horn of the spinal cord
-
Where do lower motor neurons exit from the spinal cord?
anterior spinal root
-
What are end destinations of lower motor neurons?
-
What Cranial nerves are considered lower motor neurons?
3-12
-
What is the function of interneurons in descending tracts of CNS?
- don't always exist
- receive tons of info from different tracts
- compare info
- send signal to lower motor neuron
-
Can lower motor neurons receive info from multiple sources?
yes; it is called converging input
-
What are symptoms of an injury to a lower motor neuron?
- flaccid paralysis
- atrophy of muscle
- muscular fasciculation (twitching)
- loss of reflexes
- muscular contraction because of atrophy
- degeneration (invoked stimulus causes nothing
-
What are the names of the specific descending tracts?
- corticospinal tract
- reticulospinal tract
- tectospinal tract
- rubrospinal tract
- vestibulospinal tract
-
What info does the corticospinal descending tract send?
efferent info that controls voluntary, skilled movements
-
What are the upper motor neurons of the corticospinal tract?
pyramid cells from the cerebra cortex
-
Where do 2/3 of fibers in the corticospinal descending tract come from?
precentral gyrus (primary or secondary motor centers)
-
Where do 1/3 of fibers of the corticospinal descending tract come from?
postcentral gyrus
-
What is the function of the descending postcentral gyrus fibers of the coticospinal tract?
help modulate sensory input
-
What is the pathway of travel of the pyramid axons of the corticospinal tract?
- corona radiata
- porterior limb of internal capsule
- cerebral peduncle of midbrain
- anterior pons
- anterior medulla
-
What is the function of the branching of descending axons in the medulla oblongata?
- provides nuclei of other systems with info regarding voluntary movement that is about to take place
- allows for appropriate signals to occur
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The pyramids of the medulla oblongata are formed from?
axons of pyramid cells
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Where do 80% of descending pyramid axons decussate?
inferior border of the medulla, conveniently named decussation of the pyramids...
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Is the coticospinal tract decussation inferior or superior to the fascuculus gracilis and fasciculus cuneatus decussation?
inferior
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What structure do contralateral corticospinal tracts travel through after decussating?
- lateral white column of spinal cord
- terminate in the anterior gray horn of spinal cord
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What would an injury to the corticospinal tract above the decussation cause?
muscular paralysis on the contralateral side
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Where do 20% of non-decussating fibers travel in the corticospinal tract?
- the ipsilateral anterior corticospinal tract in the anterior white column of the spinal cord
- these then decussate at the spinal level
- terminate on the anterior gray horn
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What would an injury to the anterior corticospinal tract cause?
contralateral motor defect
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What is the Babinski reflex?
- injury or incomplete upper motor neuron myelination
- tickling foot reaction should be clinching toes and pulling foot away
- when damaged, toes just spread
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What is the superficial abdominal reflex?
- normal - scratch skin over abs, abs muscles will contract
- if uppermotor neuron is damaged there is no contraction
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What is the cremaster reflex?
- normal - stroking medial side of male thigh will make scrotum ascend
- upper motor neuron injury will cause no movement in cremaster muscle
- only works on males...
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What is the function of the reticulospinal tract?
- encourage (excitatory) or inhibit voluntary movement and reflex activity
- not a prime-mover
- purely supportative
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whatis the pathway of the reticulospinal tract?
axons from reticular formation that descend in spinal cord to lower motor neurons
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What other tracts are included in the reticulospinal tracts?
descending autonomic tracts
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What does the descending autonomic tract influence?
sympathetic and parasympathetic neurons of hte intermediolateral and intermediomedial nuclei of spinal cord
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What is origin and pathway of the testocpinal tract?
- superior colliculus
- medial longitudinal fasciculus
- entire length of spinal cord in anterior white column
- most fibers decussate before leaving midbrain
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The medial longitudinal fasciculus connects nuclei of what cranial nerves?
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What is the function of the tectospinal tract?
- connect head with vision
- moves the head with eyes
- postural reflexes as a respones to visual stimuli
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Why are the spinotectal sensory pathway and the tectospinal pathway connected?
so the spinotectal tract can turn on the tectospinal tract
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Where do the axons of the rebrospinal tract come from?
soma of red nucleus in the midbrain tegmentum
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When do rebrospinat tract axons decussate?
immediately in the midbrain
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What is the pathway of the rubrospinal tract?
- mibrain
- pons
- medulla
- lateral white column of spinal cord
- anterior gray horn interneurons
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What is function of rebrospinal tract?
- allows cerebrum and cerebellum to indirectly affect muscles
- flexors facilitated
- extensors (antigravity muscles) inhibited
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Where does vestibulospinal tract get info from?
- vestibular portion o fhte inner ear
- cerebellum
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What is the pathway of the vestibulospinal tract?
- descends in anterior white column of spinal cord
- synapse on anterior gray horn interneurons
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What is the function of the vestibulospinal tract?
- maintain balance by facilitating extensors and inhibiting flexors
- opposite of rebrospinal tract
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What is spinal shock syndrome?
injury to spinal cord causes functions below injury to be depressed for a time
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What are symptoms of spinal shock syndrome?
- flaccid paralysis
- sensory impairment
- reflex depression
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What symptoms occur in recovery of spinal shock syndrome?
- spastic paralysis
- exaggerated reflexes (loss of descending tract influence)
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