Central Nervous System Flashcards
central nervous system divisions
brain–>forebrain (cerebrum and diencephalon), midbrain (no subdivisions), and hindbrain (pons and cerebellum, medulla oblongata)
spinal chord
spinal chord
- extends from C1 to L1/L2 intervertebral disk
- does not occupy length of entire vertebral canal (stops growing at age 5)
- is the distal part of the neural tube and 43-45cm in length
end of spinal chord
=conus medullaris=cone shaped part @ L1/L2
Spinal segment
Transverse section that gives rise to dorsal and ventral roots
-not on the equivalent vertebral level due to spinal chord being shorter than vertebral column
Lateral horn
Only at spinal segment levels T1-L2, where lateral horn contains sympathetic neurons and S2-S4, where it contains parasympathetic neurons
which cranial nerves arise from the brainstem?
all except I and II
which part of the brain is responsible for keeping you alert and connecting parts of the brainstem?
reticular formation
eg if you hear a noise or the light turns on while you are sleeping, the sensory info goes to RF and it wakes you up
where is the 4th ventricle?
partly in the medulla (lower half) and partly in the pons (upper half)
pontine nuclei
receive motor impulses from cerebrum and pass them to cerebellum
what coordinates visual and auditory reflexes?
superior colliculus+deep nucleus coordinates visual and inferior colliculus controls some auditory reflexes
what is the red nucleus?
- high iron content
- works with cerebellum to smooth movements
- w/out function of red nucleus you would have tremors during movements
substantia nigra
- produces dopamine
- if not producing enough–>Parkinson’s
- resting tremors present (eg pill rolling tremor, can’t hold their head still)
cerebellum functions
coordinates gross and fine movements
controls balance
lesions in cerebellum–>lost balance and wide gate
-also lose ability to perform fine movements repeatedly
what is the white matter in the cerebellum called?
arbor vitae
what connects the cerebellum to the brainstem?
connected to all three parts of brainstem via peduncle pathways (nerve bundles)
superior peduncle (midbrain)
middle peduncle (largest-pons)
inferior cerebral peduncle (medulla)
diencephalon
includes structures surrounding the 3rd ventricle
-thalamus
thalamus
- main part of diencephalon
- relay center for sensory information except smell
hypothalamus
- densely packed nuclei
- main control center for autonomic nervous system
- controls some emotions and anger, hunger, thirst
- regulates endocrine system
pineal gland
-regulates circadian rhythm
main function of lobes of brain
frontal: motor impulses, judgement, personality, mathematics
almost 2 times as big in females
parietal: receives sensory information (mainly from skin through thalamus)
temporal lobe: memory, auditory sensory info
occipital lobe: vision
–each lobe has an archive and they each send past information to frontal lobe-dreams are product of frontal lobe
main function of CSF
=cushions and protects nervous system
epidural space
subdural space
only in spinal chord, mainly fatty tissue
not normal actually spaces but can be in pathological conditions
cushions spinal chord, space where anesthetic substances are injected
subarachnoid space
=real space b/t arachnoid and pia mater that contains
CSF
-150ml capacity for CSF but 500mL produced/day
what is different about the dura mater of the brain from the spinal chord
2 layers-periosteal close to bone and meningeal
-usually together but separate to house sinuses (large veins)
how is CSF drained?
through arachnoid villi in subarachnoid space, which are finger like projections that drain CSF into sinuses (through unidirectional pathways)
-pressure builds up when it can’t be drained-hydrocephalus-and causes coma
what happens in severe infection/inflammation of the meninges?
-meningitis
unidirectional pathways leak blood back into CSF (the wrong way)
where do the cranial nerves pass through?
I-cribiform plate II-optic canal III-superior orbital fissure IV-superior orbital fissure V-superior orbital fissure, rotundum foreman, oval foremen (3 branches-trigemental) VI-superior orbital fissure VII and VIII-internal auditory meatus IX, X, and XI through jugular foregem XII-hypoglossal canal
cranial nerve fibers
no cranial nerve to carry sympathetic fibers
only 4 have parasympathetic
motor and sensory
can be mixed
optic chiasm
optic nerve branches join here and some fibers exchange sides
optic tract continues posteriorly
optic tract
fibers post. to optic chiasm
send senses to lateral geniculate nucleus
why are there vision symptoms w/pituitary tumors?
b/c it’s right @ optic chiasm and encroaches on the optic nerve/tract
occulomotor III nerve
mixed nerve
has motor fibers (supplies extraoccular mm) and parasympathetic fibers (also parasympathetic ganglion “ciliary ganglion”–every cranial nerve that has parasympathetic fibers has a ganglion where a synapse occurs
(constrict pupil)
trochlear nerve IV
pure motor nerve
supplies 1 of the extraoccular mm
Abducens VI
pure motor, supplies 1 extraoccular mm
how precise are the movements of the eyeball?
- it can move a fraction of a degree
- 3 cranial nerves control muscles that move it
- the nerves lose sensitivity after a fraction of a second and it makes a tiny movement that allows light to focus on different parts of the retina
trigeminal V nerve
3 branches, sensory and motor fibers (sensory ganglion trigeminal ganglion)
- opthalmic branch V-1: pure general sensory for eyeball (pain, temp, touch)
- maxillary branch (middle) V-2-pure sensory-nasal cavity, part of skin of the face
- mandibular branch-teeth and tongue general sense-mixed motor and sensory (deep muscles involved in mastication)
- V supplies sensory for all areas of the face
facial VII nerve
mixed sensory, motor, parasympathetic
- geniculate sensory ganglion
- sensory fibers mostly for taste
- motor fibers supply superficial facial mm (for facial expressions)
- pterygopalatine and submandibular parasympathetic ganglion
- parasympathetic supply 2 salivary glands, and lacrimal gland (tears)
vestibulocochlear VIII
- vestibular branch from vestibular part of inner ear
- senses balance and equilibrium
- cochlear branch from cochlea picks up sense from hearing
glossopharyngeal IX
- mixed sensory, motor, and parasympathetic
- ignore motor b/c supplies insignificant muscle
- sensory superior and inferior ganglion
- supplies fibers for pharynx and back of tongue (gag reflex)
- otic parasympathetic ganglion
- parasympathetic fibers innervate parotid salivary gland
- some fibers distributed to carotid body and carotid sinus (chemo receptors for blood content and pressure)
vagus X nerve
only nerve that leaves head and distributes fibers to structures below
- largest parasympathetic nerve in body and has sensory and motor fibers
- superior and inferior sensory ganglions
- motor fibers distributed to pharyngial muscles (pharynx)
- parasympathetic ganglia (viseral ganglia) located in walls of target organs
- parasympathetic fibers distribute in thorax (heart, lungs) and organs in abdomen (through celiac plexus and hypogastric plexus)
- -(many branches, including cardiac branches–>cardiac plexus and then heart)
Accessory XI
pure motor nerve
-supplies trapezius and sternocleidomastoid
Hypoglossal XII nerve
pure motor
innervates muscles in the tongue (19)
dorsal column-medial lemniscal pathway
-ascending sensory pathway, collects fine touch and proprioceptive info
1st order neuron in DRG
2nd order in medulla, crosses body
3rd in thalamus
spinocerebellar pathway
ascending pathway, connects spinal chord and the cerebellum
1st order in DRG
2nd in dorsal horn–>cerebellum (no decussation)
injury to the left sid e of the spinal chord (medial lemniscus pathway)
- if the left side is injured before the decussation, the same side limb will be affected
- if the injury is above it, the right side will be affected
spinothalamic pathway
- ascending pathway for pain and temperature senses from different parts of the body
- 1st order in DRG
- 2nd order in dorsal horn
- deccusation anterior to central canal
- 3rd order in thalamus
- there are two (one of each side)
syringo myelia (central canal expands)
-central canal expands and pushes into spinothalamic pathway–>both sides of the body are effected b/c there is one on each side
pyramidal-lateral and ventral corticospinal pathway
axons of upper motor neuron pass through cerebral peduncle and pons into medulla
- all fibers pass through pyramid of medulla, then…
- 80% of fibers deccusate at the medulla and descend on contralateral side in lateral column as lateral corticospinal tract:
- the rest of the fibers descend in the anterior column
differences in lateral and ventral corticospinal tract
axons enter dorsal horn and pass impulse to a second motor neuron in anterior horn of spinal chord which distributes axons to muscles
- anterior fibers decussate at the spinal chord and synapse to a lower motor neuron in anterior horn
- lateral supplies mostly mm of limbs
- anterior supplies mostly mm of torso, head and neck
ALS affecting the R side of the spinal chord
(injury involved both pathways)
R side limbs movements will be affected b/c lateral has already done decussation
L side trunk mm will be affected
white matter in the brain
- comissural fibers connect different hemispheres
- associated fibers connect different areas of the same hemisphere
- projection fibers connect cortex to lower brain and spinal chord
CSF leaves 4th ventricle how
median aperature and lateral aperature x 2
CSF enters subarachnoid space via these 3 openings
how is CSF produced
choroid plexus produces CSF inside all 4 ventricles from blood plasma from venus sinuses
extensions of dura mater
falx cerebri partially separates hemispheres
tentorium cerebelli separates cerebellum and occipital lobe
falx cerebelli separates two lobes of cerebellum
main function=to hold venous sinuses
extrapyramidal pathways
responsible for subconcious control of movement like posture
