Unit 3 Flashcards
1
Q
Blood Supplies the Brain with
A
Glucose
Oxygen
and Removes carbon dioxide and metabolic waste
2
Q
Nerve cells do not store glucose or oxygen
A
for more than 4 minutes
3
Q
what happens when the heart stops?
A
no blood flow= no glucose/oxygen= no energy= no sodium/potassium pump= cells explode= loosing brain cells
4
Q
what percentage of your blood does the brain take
A
20%
5
Q
how many ml per second are sent to the brain?
A
750ml
6
Q
how many ml per how many grams of tissue must there be
A
Blood flow must be 50-60 mL per 100g of tissue per minute
7
Q
how much is too little blood flow and what does it result in?
A
Too little blood flow or less than 20 mL per 100g results in impaired functioning
8
Q
blood pressure regulations depends on
A
the needs of the brain
9
Q
Arteries
A
supply blood to the brain
10
Q
Veins
A
carry deoxygenated blood back to the heart and lungs
11
Q
Aorta
A
main artery from the heart
12
Q
2 Major paired blood vessels systems carry arterial blood supply from the heart to the brain
A
Carotid & Vertebral Basilar
13
Q
Vascular Circulation
A
Heart -> Aorta -> Large Arteries -> Arterioles -> Capillaries -> venules -> larger veins -> sinuses -> Jugular vein -> heart
14
Q
Capillaries
A
the end of the arteriole system, only allows blood to flow slowly which lets blood and cell exchange nutrients, Blood Brain Barrier
15
Q
Venules
A
the smallest extension of the venous system connected to capillaries
16
Q
blood brain barrier
A
right between the capillaries and venules
The BBB restricts substances from getting from the bloodstream to nervous tissue
BBB regulates arterial permeablity because CNS capillaries are lined with endothelial cells
Astrocytes also surround the capillaries as added protection
17
Q
anastamosis
A
the end of the capillaries where they meet the veins, this is where the oxygen and nutrients are exchanged
18
Q
strokes are more likely to happen in the
A
arteries
19
Q
carotid system
A
common carotid external carotid internal carotid anterior choroidal ophthalmic
20
Q
common carotid
A
runs up the neck behind the jaw
21
Q
external carotid
A
branches to supply the face, eye, oral and nasal cavities
22
Q
internal carotid
A
MAJOR source of blood to the brain
1. enters brain through the carotid foramen
2. Curves anteriorly and medially into the cavernous sinus
3. Anterior Choroidal – lateral ventricle, internal capsule, basal ganglia, hippocampus, midbrain
4. Opthalmic – supplies the eyeball and ocular muscles
splits into
Anterior Cerebral Artery and Middle Cerebral Artery
23
Q
anterior choroidal
A
lateral ventricle, internal capsule, basal ganglia, hippocampus, midbrain
24
Q
ophthalmic
A
supplies the eyeball and ocular muscles
25
Anterior Cerebral Artery
medial frontal lobe, corpus callosum, caudate nucleus, BG
26
Middle Cerebral Artery
ENTIRE lateral surface,
- frontal, temporal and parietal branches
- broca’s and Wernicke’s area, precentral and postcentral gyrus, primary auditory cortex
site of the most strokes
27
Vertebral Basilar System
Subclavian Arteries -> Vertebral arteries -> Basilar Artery – Circle of Willis
28
Vertebral Arteries
ascends along the cervical vertebral column and enter the cranium through the foramen magnum
29
There are many PAIRED branches of arteries that split off of the vertebral and basilar arteries
From the Vertebral Arteries: which supply the dorsal medulla, CN 9-12, cerebellum
Posterior spinal – 1/3 dorsal spinal cord
Anterior spinal –pyramid decussation, anterior 2/3 of spinal cord
Posterior Inferior Cerebellar Artery (PICA)
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From the Basilar Artery: which supplies the lateral pons, cerebellum, CNs 5, 7, 8, 10
Anterior Inferior Cerebellar Arteries (AICA)
Labyrinthine Artery- a branch of AICA – delivers blood to the cochlea and vestibular apparatus
2. Superior Cerebellar Arteries
3. Posterior Cerebral Arteries (PCA)- anterior and inferior temporal lobe, occipital lobe
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3 arteries that go to the cerebellum
PICA
AICA
Superior Cerebellar Arteries
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Arteries go to brain stem
Basilar
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PCA
medial temporal lobe
| occipital
34
MCA
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the lateral sides of the brain
brocha's
weirnicke's
primary motor
primary sensory
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35
ACA
arterial medial of the frontal lobe
36
circle of Willis
A wreath like circle on the ventral side of the brain
Made of communicating arteries (anterior and posterior) that connect the carotid and vertebral basilar systems
Equalizes the blood supply to both hemispheres
Allows for revascularization after damage or stroke
Redundancy or Collateral Circulation
37
Water shed area
these are areas where the END branches of major arteries overlap and have anatomosis
- these areas are very susceptible to low blood flow
38
Venous System
Capillaries -> venules -> large veins -> dural sinuses
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DURAL SINUS
Superior Sagittal Sinus – arachnoid villi/granules
Inferior Sagittal Sinus – inferior margin of falx cerebri
Straight Sinus
Transverse Sinuses – arise from the confluence of sinuses and form the Internal Jugular Veins
Jugular Veins return blood to heart
40
Stroke Risk Factors
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Doubles every 10 years after age 55
HTN
DM
CAD
Obesity
Smoking
Gender and ethnicity
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41
CVAs
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Cerebrovascular Accidents – CVAs or STROKE
The 5th cause of death
Characterized by sudden focal deficits
Classified into 2 types
Occlusive: thrombosis or embolis
Hemorrhagic: bleeding
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42
Thrombotic
an occlusive stroke typically caused by atherosclerosis or hardened arterial walls
- 65% of strokes
43
Embolism
an occlusive stroke caused by a displaced clot
| - 25% of strokes
44
Transient Ischemic Attack – TIA
Ischemia = insufficient blood supply
TIAs = a temporary interruption of blood
Symptoms of stroke but last less than 30 minutes
30% of people who have a TIA will later have a full stroke
45
Hemorrhagic
bleeding or rupturing of weakened vessel walls
Usually due to Hypertension
10-15% of CVAs
Common sites include the thalamus and basal ganglia (Lacunar strokes – lenticuostriate arteries-- little arteries on Choroidal)
Classified by where the blood pools: intracerebral, dural, subdural and subarachnoid
46
Aneurysm
Abnormal dilation of artery
| A sac-like protrusion from a blood vessel or the heart, resulting from a weakening of the vessel wall or heart muscle
47
Lacunar Infarct
Involve small arteries in the Basal Ganglia and Thalamus – Lenticulostriate arteries- branches of the MCA
HTN is greatest cause
Happen abruptly or over the course of days
48
CVA treatment
Tissue plasminogen-activating agents (t-PA)
Mercy Retriever
Craniotomy
Endarterectomy
49
midline shift aka
mass effect
50
sound is created by
molecular vibrations that propogate pressure waves
51
sound is characterized by
frequency and intensity
52
frequency
the speed of the vibration in cycles per second or Hz
The human ear detects sounds from 20-20,000 Hz
Speech occurs in 250-8000 Hz
Most sensitive frequencies are 1,000-3,000
pitch
53
intensity
the amplitude of sound waves – loudness or dB
Sound pressure level SPL is a log ratio of measured sound pressure Px at the tympanic membrane and reference sound pressure Pr
SPL = 20 log Px/Pr
Referenced sound pressure is constant = 20uPa (micropascal) or the pressure that is needed to make 1000Hz just audible
loudness
The human ear hears in a SPL (sound pressure level) range of 0-140dB
Most spoken communication is around 50 - 60 dB
Sounds greater than 140dB cause pain
Loudness and Intensity is not a 1:1 ratio
45.5 dB is need to detect sound at 125Hz and only 8.5 dB is needed at 2000Hz
54
transmission of sound
1. Sound waves are collected by the pinna and directed to the external auditory meatus
2. Sound waves strike the tympanic membrane
3. The vibration is converted from a pressure wave to mechanical wave (motion) by the middle ear ossicles – malleus, incus, stapes
4. Mechanical energy is converted into Hydraulic energy by the fluid in the inner ear – cochlea – oval window
5. Hydraulic waves stimulate the cochlear hair cells which trigger action potentials to be sent down the vestibulocochlear nerve-CN 8
55
Ossicles
Malleus, Incus and Stapes
Regulate sound transmission to the inner ear by compensating for the difference in how molecules move in air and fluid
Optimize the transmission of sound by increasing force on the oval window
BUT….they limit the frequencies that we can hear because we only hear the frequencies that the bones can transmit
Tensor Tympani
Stapedius
-together these muscles stiffen the ossicles to attenuate sound to protect the cochlea from very intense sounds
56
tensor timpani
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CN V inserts into the malleus
dampens sound (stops mechanical motion when it contracts)
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57
stapedius
CN VII inserts into the stapes
58
CN VII inserts into the stapes
The inner ear is found in the petrous portion of the temporal bone
2 parts
Vestibular Apparatus
Cholear Duct
They are interconnected and filled with fluid - Perilymph
59
Vestibular Apparatus
saccule, utricle, semicircular ducts
60
the cochlea
Mechanical vibrations of sound-converted into hydraulic waves- then into electrical signals
These signals can be transmitted in the form of impulses – action potentials
Is shaped like a snail
It wraps 2.5 times around the modiolus – the central bony core
3 parts
Scala vestibuli
Scala media/cochlear duct
Scala tympani
Stria vascularis
61
Scala vestibul
filled with perilymph - Na
62
Scala media/cochlear duct
filled with endolymph - K
| - contains the Organ of Corti
63
Scala tympani
filled with perilymph – Na
64
Stria vascularis
secretes endolymph
65
Organ of Corti
contains outer and inner hair cells which are the primary receptor cells that mechanically convert movement in the fluid to impulses
Outer hair cells – 3 rows – 12,000
Inner hair cells – 1 row – 3,500
The hair cells run the entire length of the cochlea and project steriocilia which are embedded in the tectorial membrane
66
outer hair cells
connected to the olivocochlear bundle OCB
67
inner hair cells
innervated by cochlear nerve endings
68
organ of corti transmission
The cilia of the hair cells move as waves are produced in the perilymph fluid by the basilar membrane
The displacement of the basilar membrane causes a shearing effect which opens mechanical ion channels in the hair cells allowing K to flow in
After K flows in Ca2+ ion channels open (Ca2+ comes in)
The depolarized hair cells generate the action potential which is then received by the cochlear nerve via a release of glutamate
69
the cochlea is arranged
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in a tonotopic fashion
one-to-one relationship between the location of the hair cell and the tone received/perceived
20 – 20,000 hz
High frequencies in the base
Lower frequencies – near helicotrema
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70
bilateral auditory representation
the auditory cortex in each hemisphere receives input from both ears
but the major input to each hemisphere is from the opposite ear
because of this a lesion in the pathway does not result in a complete loss of hearing but only a mild hearing loss
71
sound localization
we are able to locate the source of sound by a mechanism that compares the difference between when a given sound reaches both ears and difference in intensity between the two ears
mechanisms decides which ear received the sound first and in which ear the sound was more intense
uses intramural time delay
72
tonotopic representation
the tonotopic organization is maintained throughout the auditory pathway (not just the cochlea)
even in the primary auditory cortex (Heschl’s gyrus) the neurons are arranged to receive only set frequencies
73
descending auditory projection
there are fibers that descend (go down) from the auditory cortex to the cochlear hair cells.
these descending fibers provide a feedback mechanism
this feedback is used to refine the auditory impulse
---improves the sound-to-noise ratio allowing sound to be sharper
feedback also enhances our ability to localize sound and attend to certain sounds
Outer cells – connected to the olivocochlear bundle
74
Central Auditory PathwayAscending or Afferent Pathway
1. Vestibulocochlear nerve enters the brainstem at the pontomedullary junction
2. Goes to cochlear nuclear complex – dorsal and ventral nuclei
3. Fibers have ipsilateral and contralateral projections to the superior olivary complex (pons--comparison btw input from both ears beginning to localize sound) trapezoid body
4. Follows to lateral lemniscus (auditory pathway of brainstem from pons to midbrain)
5. Inferior colliculus (midbrain)
6. Thalamus/Medial Geniculate Body
7. Heschl’s gyrus (recognize sound, processes and attends to sounds)
8. Wernicke’s area (assign meaning)
75
The Superior Olivary Complex
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Located in the pons
Receives fibers from the trapezoid body
auditory impulses begin to localize to the contralateral side
at this point a person can begin
to LOCALIZE SOUND
provides a comparison between
input from both ears
judges the differences in time and
intensity of the sound
send the impulses to both hemispheres
```
76
The Lateral Lemniscus
The primary ascending auditory pathway
Connects the superior olivary nucleus to the inferior colliculus of the midbrain
Lateral pons
Receives crossed and uncrossed projections but has more projections from the opposite ear
77
The Inferior Colliculus
contains commissural fibers so it can cross reference and integrate monaural and binaural auditory inputs
begins to integrate the impulses from both ears to help with interpretation of the sound
also plays a part in beginning to integrate auditory information with visual information received by the retina
Sends fibers to the midbrain reticular formation to help in the attentional process for selecting, screening and inhibiting auditory information
78
medial Geniculate body
RELAY STATION for auditory information
directs the auditory impulse to the ipsilateral hemisphere
Projects ventrally and laterally through the lenticular portion of the internal capsule
79
Heschl’s Gyrus
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temporal lobe
primary auditory area
detects auditory impulses
tonotopic organization
site of auditory sensation & perception
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80
wernicke's area
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final stop if it is speech
temporal lobe
concerned with recognition of language
assigns meaning
auditory memory of previous auditory experiences to be used in the future for interpretation
auditory memory of previous linguistic experiences
comprehending spoken language
End point of auditory processing
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81
Descending Auditory Pathway Efferent Pathway
This pathway acts as a ‘cochlear amplifier’ by preprocessing sound and as acoustic protection
Efferent/motor fibers travel down from the superior olivary complex to the cochlea
Travel through the lateral or medial olivocochlear bundle
Lateral – uncrossed to the inner hair cells
Medial – cross to the outer hair cells
When the outer hair cells are stimulated they can amplify the traveling wave which increases the sensitivity of the inner hair
NOTE: This is what is tested during otoacoustic emission OAE tests
82
two functions of the vestibular system
Equilibrium
Eye Fixation
Controlled subconsciously
Regulated by integration of info from the semicircular ducts/canals
83
Vestibular System Anatomy
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Semicircular ducts/canals
Vestibule – Saccule and Utricle
Vestibular Nuclei
Vascular Supply
Vestibular projections
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84
3 semicircular ducts
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Anterior, Posterior, and Lateral
Filled with endolymph
Aligned at right angles to each other – this allows the detection of acceleration of the body in various planes
Connected to vestibule
Utricle and saccule– vestibular sacs
Ampulla – contains cristae
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85
cranial nerves
12- paired CNs
Have specialized functions for vision, audition, gustation, sensation and motor for our face, voice and swallowing
Have sensory or motor functions BUT some CNs have both
CN 1 - olfactory and CN 2- optic are part of the forebrain ALL others are in the Brainstem
Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Spinal Accessory, Hypoglossal
86
CN 1 – Olfactory Nerve
SMELL
Found in the roof of the nasal cavity
Olfactory neurons group together to form the olfactory nerve which travels through the cribriform plate to form the olfactory bulbs on the basal surface of the frontal lobe
Olfactory cells are only found in mammals and are replaced every 30-60 days
ANOSMIA – impaired ability to smell
87
CN 2 – Optic Nerve
VISION
Damage anywhere
Along the pathway results
In visual field deficits
Homonymous hemianopia- one whole nerve not sending signal
Visual closure- ability to "connect the dots" in an image
Figure Ground Discrimination- differing positive and negative ground
88
CN 3 - Oculomotor
MIDBRAIN – at the level of the superior colliculus
4 ocular muscles
Superior rectus – up and in
Medial rectus - adducts
Inferior rectus – down and in
Inferior oblique – up and out
Levator palpebrae superioris – your eye lid
Reflexes of the eye, lens and light accommodation
Damage – diplopia – double vision
89
CN 4 - Trochlear
Midbrain- at the level of the inferior colliculi
Enters the ocular orbit with CN 3 to innervate the superior oblique muscle
Superior oblique = down and out
Contributes to ocular movement
Damage results in Diplopia – double vision
90
CN 5 – Trigeminal
Mixed nerve
Pons
Mediates pain, temperature, touch, and proprioception for mastication for the face, head, oral and nasal cavities, anterior 2/3rds of the tongue, anterior pinna, anterior external auditory meatus and external surface of the tympanic membrane
91
CN 6 - Abducens
3rd nerve that contributes to eye movement
Pons
Innervates the Lateral Rectus Muscle – moves the eye laterally
Damage – eye will deviate in
Damage to the Eye gaze center (MLF) where CN 3,4, and 6 receive input from the vestibular system results in inability to conjugate eye movement/focus
The motor portion controls muscles of mastication
Internal and external pterygoid, temporalis and masseter
Other muscles include: mylohyoid, anterior belly of the digastric, tensor veli palatine and the tensor tympani
Damage
Sensory – peripheral sensory nerve = loss of sensation on the same side
Tic douloureux/trigeminal neuralgia- chronic pain on the face treatment = severing the nerve
Motor – damage results in flaccid paralysis of muscles on the same side and the jaw deviates toward the injury
92
CN 7- Facial
Mixed motor and sensory
Pons
Motor: function relevant to speech: muscles of facial expression and stapedius
Depressor anguli oris, depressor labii inferioris, levator anguli oris, mentalis, orbicularis oculi, orbibularis oris, platysma, risorius, buccinators and zygomaticus
Sensory: taste to the anterior 2/3 of the tongue
Damage: droop/dysarthria
93
CN 8 - Vestibulocochlear
Medulla and pons
Mediates equilibrium and hearing
Damage
Cochlear – hearing loss types depends on location
Vestibular – balance disorders, vertigo, nystagmus
94
CN 9 - Glossopharyngeal
Mixed motor and sensory
medulla
Motor functions relevant to speech: stylopharyngeus and superior pharyngeal constrictor
Sensory functions relevant to speech: pharynx, tongue, eustachian tube, middle ear, gag reflex, ALSO – the carotid body
* Responsible for Touch and Taste from the posterior 1/3 of tongue
Damage:
reduced pharyngeal sensation, reduced gag, and reduced pharyngeal elevation during swallow
seldom damaged alone, usually together with CN 10 vagus
95
CN 10 Vagus
90% sensory and 10% motor:
Medulla
Controls muscles for phonation and swallowing
Also controls cardiac muscles, smooth muscles of the esophagus, stomach and intestines
mediates general sensation, pain, tension and temperature from the pharynx, larynx, thorax, abdomen, heart, bronchi, esophagus and carotid sinus
large part of the parasympathetic system – mediates your visceral response
innervates muscles of the pharynx, larynx, soft palate (except the tensor palatini) and upper esophagus
**Has several branches
96
Pharyngeal branch of 10
Pharyngeal constrictor muscles except stylopharyngus (CN 9)
Superior, middle and inferior constrictors,
All velum muscles except tensor veli palatini (CN V)
levator palate, palatoglossus
97
Superior laryngeal branch of 10
Internal - is sensory from mucous membranes of larynx, epiglottis, base of tongue, and aryepiglottic folds
External - is motor to the cricothyroid (pitch)
98
Recurrent laryngeal branch of 10
Intrinsic muscles of larynx (except cricothyroid) and sensory to the vocal cords
Left side wraps around the aorta
99
CN 11 – Spinal Accessory
Motor Nerve
medulla and ventral horn of C1-C5
innervates the sternocleidomastoid and the trapezius muscles
Damage: leads to weak head rotation and inability to shrug shoulders
100
CN 12 Hypoglossal
Motor Nerve
medulla
Controls tongue movements by regulating intrinsic and extrinsic (all except palatoglossal, which is controlled by CN X) tongue muscles.
Reminder:
Extrinsic muscles: genioglossus, styloglossus, and hyoglossus.
Intrinsic muscles: Superior & inferior longitudinal, transverse & vertical
Damage: atrophy, weakness and fasiculations of the tongue
