Week 5 content (CSF & blood flow, Vision & vestibular system) Flashcards
Three layers of meninges cover the brain and spinal cord
Dura mater, Arachnoid mater, Pia mater
Dura mater
surrounds the brain
- strong outer layer
- firmly bonds to the inside of the skull and inner layer
Arachnoid mater
- delicate membrane loosely attached to the dura
Pia mater
- innermost layer, is tightly apposed to the surfaces of the brain and spinal cord
three spaces of the meninges
subdural, epidural, subarachnoid
where is the subdural space?
between dura and arachnoid
where is the epidural space
between skull and dura
where is the subarachnoid space?
between arachnoid and pia
what are ventricles?
CSF filled spaces inside the brain form a system of FOUR ventricles
pair of lateral ventricles: location, and connected to…
located in the cerebral hemispheres,
- consists of body, atrium, anterior, posterior and inferior horns
- connected to third ventricle by interventricular foramina
third ventricle: location and connected to…
narrow slit in the midline of diencephalon (over thalamus)
-3rd and 4th are connected with cerebral aquaduct
Fourth ventricle: location and connected to…
- located posterior to the pons and medulla and anterior to the cerebellum
- continues to spinal cord
- drains into subarachnoid space
approximately _____ cc’s of CSF in body
150 cc’s
what makes CSF fluid
choroid plexus
CSF formation and circulation route
1) choroid plexuses
2) lateral ventricle
3) ventricular foramina
4) 3rd ventricle
5) cerebral aqueduct
6) fourth ventricle
7) subarachnoid space
8) around brain and spinal cord
9) venous sinuses
10) adrenal system and into capillaries
what does cerebrospinal fluid do?
protects CNS
regulates the content of extracellular fluid
arterial supply to cerebral hemispheres: anterior cerebral artery
medial frontal and parietal lobes, anterior caudate, putamen, anterior limb of internal capsule
arterial supply to cerebral hemispheres: middle cerebral artery
parts of basal ganglia (globus pallidus, putamen, body of caudate), most of lateral hemisphere, genu of internal capsule
arterial supply to cerebral hemispheres: posterior cerebral artery
midbrain, occipital lobe, inferomedial temporal lobe, most of thalamus
weakness in the legs =
occlusion of anterior cerebral artery
weakness in the hands =
occlusion of middle cerebral artery issues
paresis of eye, thalamic syndrome =
occlusion of posterior cerebral artery
What artery supplies the anterior circulation to the brain/body?
internal carotid artery
What artery supplies the posterior circulation to the brain/body?
vertebral artery
outer layer of eye consists of…
sclera, cornea, conjuctiva
middle layer, vascular layer of eye consists of…
choroid, iris, ciliary muscles
inner layer, neural layer of eye consists of…
retina, fovea, optic disk
sclera
touch connective tissue, maintains shape of eye
cornea
transparent, allow light to enter
conjunctiva
thin layer, lubricates the eyes
choroid
filled with blood vessels that bring oxygen and nutrients to the eye (all blood supply)
iris
2 layers of pigmented smooth muscle, regulates the diameter of pupil
ciliary muscles
change the shape of the lens
pupil
hole in the center of iris that allow light to enter
retina
photoreceptors (rods and cones) that detect light waves, conversion of light energy to electric energy (most important)
cones do…
color vision
rods do…
low light levels
fovea
greatest visual acuity; will see the best; high concentration of rods/cones
optic disk
optic nerve and blood vessels supplying the eye pass through the retina- blind spot
Aqueous humor
supplies nutrients to cornea and lens
Vitreous humor
maintains spherical structure of eye (helps with structure of the eye)
nasal retina-nearest the nose
information from the nasal half of each retina crosses the midline in the optic chiasm and projects to the contralateral visual cortex
temporal retina
nearest the temporal bone: information from each temporal half continues ipsilaterally through the optic chiasm to the ipsilateral cortex
left nasal field and right temporal field = _______ visual field
right visual field
left nasal hemiretina and right temporal hemiretina =
right optic tract
the lateral rectus does
abduction (away from the nose)
the medial rectus does
adduction (towards the nose)
the inferior rectus does
down movement of eye
superior rectus does
up movement of eye
inferior oblique does
extorsion (ER-upper pole of the eye outward), elevation, and abduction
- rolling of eyes
superior oblique
intorsion (IR), depression, and abduction
-looking @ nose
what 3 nerves control the eye movements
CN III, IV, VI
lateral rectus is innervated by
CN VI (abducens)
medial rectus is innervated by
CN III (oculomotor)
inferior rectus is innervated by
CN III (oculomotor)
superior rectus is innervated by
CN III (oculomotor)
inferior oblique is innervated by
CN III (oculomotor)
superior oblique is innervated by
CN IV (Trochlear)
oscillopsia
bouncing gaze - reflex is messed up; not muscles
gaze stabilization
keeping the position of the eyes stable during head movements to ensure that the environment does not appear to bounce
direction of gaze
directing the gaze at visual targets
eye movements: conjugate
both eyes move in the same direction (up, down, left, right)
- finger towards nose
Eye movements: vergence
eyes move toward the midline or away from the midline (cross-eyed)
- finger away from nose
saccades is
fast eye movements to switch gaze from one object to another
smooth pursuits is
eye movements that are used to follow a moving object
gaze jumping from finger to finger is an example of
saccades
gaze when following a pencil is an example of
smooth pursuits
reading a book is which type of gaze
mixture of saccades and smooth pursuits
vestibular information is essential for
postural control, especially during movements of head
vestibular information assists with
eye movements to keep the visual field stable with head motion to allow clear vision
outer ear (air filled) parts and job
pinna and external auditory meatus
directs sound waves into the auditory canal
middle ear (air filled) parts and job
- tympanic membrane (separates inner ear from middle ear)
- 3 auditory ossicles, oval window and round window
- amplification of sound waves to transmit them from air to fluid environment
inner ear (fluid filled) parts and job
- associated with hearing (cochlea) and equilibrium (semicircular canals)
- vestibulocochlear nerve contains afferents for hearing and equilibrium
pathway of sound**
peripheral vestibular system is made up of
semicircular canals and otolith organs
semicircular canals are
anterior, posterior, and lateral canals
otolith organs are
utricle and saccule
hair cells are embedded in a gelatinous mass called the
cupula
each of the 3 semicircular canals opens into the
utricle
bony labyrinth
contains the 3 semicircular canals, cochlea and 2 otoliths.
- filled with perilymphatic
membranous labyrinth
thin layer of tissue suspended within the bony labyrinth and contains endolymphatic fluid
anterior canal detects which movement of the head?
detects the rotation of head up and down, YES motion, sagittal plane
posterior canal detects which movement of the head?
detects the rotation of head up and down to side, coronal plane (circling head)
lateral canal detects which movement of the head?
detects the rotation of head from side to side, no motion, transverse plane
macula is
- hair projecting from hair cells are embedded in a gelatinous material
- atop gelatinous material are otoliths
- are NOT sensitive to rotation but responds to head position relative to gravity (acceleration and deceleration
vestibular nuclei is located
at the pons
where does information from the semicircular canals and otolith organs go?
from the vestibular nerve to the vestibular nuclei in the pons and medulla, and to the flocculonodular lobe in the cerebellum
one major function of the vestibular nuclei is to…
coordinate movements of the eyes and head to allow for stable visual fixation during head movement
vestibular apparatus
part of the inner ear that detects position and movement of the head; it consists of the semicircular canals, saccule, and utricle
otolithic organs
anatomic site of sensory receptors (utricle, saccule) that respond to head position relative to gravity and to linear acceleration and deceleration of the head
vestibular nuclei
site of synapse between the first- and second-order neurons that convey information about head position and head movement
