What are extraneural factors affecting the blood supply to the brain?
low or high blood pressure (variable)
What is a thrombis and when may it take place?
a blood clot (narrowing of artery)
in a few minutes or take hours or even days to fully evolve.
what is an embolus?
a traveling blood clot
A _____ may break off from ____ and be carried to other places in the bloodstream. When the embolus reaches an artery too narrow to pass through and becomes _____ blood flow distal to the fragment ___ and the result is ____
a larger thrombus
infarction of distal brain tissue due to lack of nutrients and oxygen.
What does a lack of glucose and oxygen cause?
depletion of the celluar engery stores required to maintain electrical potentials and ion gradients.
What is a penumbra
Tissue around the infarctio that is alive but the function is questionable.
Dark area surrounding dead tissue
In Ischemic (____) brain tisuuse, what happens?
the membrane that surrounds each affected neuron becomes "leaky" and the cell loses potassium and atp the tissues medium for energy exchange.
when a membrane is leaky, what happens?
sends warning to glial cells to clean up biproduct or eat bad cells so they eat up cells and death is the result.
The lower the blockage....
The greater the problem
The blood brain barrier does what?
Protects teh brain from "foreign substances" in the blood that may injure the brain
Protects the brain from hormones and neurotransmitters in the rest of the body
Maintains constant pure environment for the brain.
What is the blood brain barrier?
army of enothielial cells that form wall that only certain things can pass.
What is the arachnoid barrier layer?
the arachnoid barrier later is a part of the arachnoid meningeal layer, it is formed by tight junctions between the endothelial cells of cerebral capillaries in the arachnoid mater.
what did we used to think about the BBB and what do we know now?
We used to think that the only way that a chmical could leave the blood and enter the brain was by being small enough to sneak through the tight junctions,
but now e know that there are myriad molecular passageways embedded in the membrain of the endothelial cells that block some chemicals and actively push others through
Microglia do what?
patrol the brain and spinal cord for invaders that are trying to get in, or thet have alrady succeeded in getting inside. they also look for damaged or cancerous cells and remove them.
What are nerves.
Bundle of peripheral axons that are found in PNS.
Axons that travel together are
What are cranial nerves vs spinal nerves
Cranial nerves are nerves that emerge directly from the brain stem
Spinal nerves emerge from segments of the spinal cord. 2221
How many nerves are involved in speech and swallowing?
There are ___ pairs of cranial nerves
all cranial nerves exit from front of brainstem except
for the IV it exits from the back.
What are UMN
Upper motor neurons originate in the cortex (precentral gyrus)
Axons synapse on cell bodies of lower motor neurons in brainstem and spinal cord.
Cell bodies and axons totally contained within CNS
What are LMN
Originate in the brainstem and spinal cord
Receive information from upper motor neurons
axons synapes on muscle fivers
cell bodies contained with CNS and axons leave CNS
Form a final common pathway for information descending from cerebrum to periphery.
What is the corticobulbar tract, Explain.
A bundle of fibers that go from the cortex to another area of the brain in the spinal nerves
UMN from cortex terminate on LMN nuclei in the brainstem that give rise to CN V, VII, IX, X, XI, and XII
Corticobulbar fibers from each hemisphere project bilaterally to brain stem nuclei (except for parts of CN VII:Facial Nerve)
The corticobulbar tract is ..... (unilateral or bilateral)
UMN travel together in...
LMN travel together as...
What nerves are involved in smell and vision
I, II, II, IV, VI
Describe the Olfactory Nerve
Receptors located in mucous membrane of nose
Together, receptors and their unmyelinated axons comprise CN I
Pass through several holes in cribriform plate of themoid bone
Terminate in olfactory bulbe
information about olfaction processed in temporal lobe
Olfaction is only sense not mediated by thalamus.
The olfactory nerve is not...
mediated by the thalamus like all other sensations.
What is the difference between sensation and perception
Sensation is the physical stimuli and perception is your interpretation of the sensation.
Describe the Optic Nerve
Visual information from retina is carried back to superior colliculus of midbrain on optic tract
From superior colliculus information passed on to lateral geniculate body of thalamus and then to cortex of occipital lobe
Where do the visual fields merge?
Goes to the thalamus and ends up in the cortex of occipital lobe.
Optic nerve exits..
back of eye in orbit and enters cranium via the optic canal (foramen)
Describe the Oculomotor nerve
A motor nerve
nucleus located in midbrain
mediates eyeball movements, pupil constriction, and eyelid elevataion
What are the two components of the oculomotor nerve and their functiosn
somatic motor: controls muscles responsible for precise movement of eyes for visual tracking or fixation
Visceral motor: mediates pupillary light and accomodation reflexes.
the oculomotor nerve exits...
back of eye in orbit and enters cranium via superior orbital fissure.
Describe the troclear nerve
A motor nerve
Nucleus located in the midbrain
Nerve mediates eye movements (damage will cause diplopia or double vision
supplies one extraocular muscle: contralateral superior oblique (moves eye down from medial position)
Only a cranial nerve that exits brain dorsally.
trochlear nerve exits..
back of eye in orbit and enters cranium via superior orbital fissure
Describe the Abducens nerve.
A motor nerve
nucleus located in pons
mediates eye movement
opposit the trochlear nerve
innervates ipsilateral lateral recuts muscle (move eyes out laterally)
Abducens nerve exits..
back of the eye in orbit and enters the cranium via superior orbital fissure.
What cranial nerves are involved in speech, hearing and swallowing
V, VII, VIII, IX, X, IX,XII
Describe the Trigeminal nerve
A mixed nerve
Nucleus located in the pons
A large sensory component:
-Sensation from face and scalp; mucous membranes of mouth, tongue, nose, paranasal sinuses, and gums, teeth most of dura (pain, touch, temperature)
A smaller motor component
-innervates masseter and temporalis muscles (mastication), tensor veli palatini muscle(Eustachian tubes), and tensor tympani muscle of middle ear (dampens sound through middle ear).
How many branches does the trigeminal nerve have and what are they?
Mandibular (sensory and motor)
the branches of the V nerve enter where?
Opthalmic branch enters via superior orbital fissure.
Maxillary branch enters via foramen rotundum
Mandibular branch enters and exits cranium via foramen ovale
When damage occures to the sensory aspect of the CN V...
Numbness or loss of senstion of areas intervated
Absent corneal reflex when affected eye is stimulated (sensory component mediated by opthalmic branc of the ipsilateral trigeminal nerve, Motor component mediated by bilateral facial nerve)
Describe trigeminal neuralgia (V2 and V3)
Mild touch (usually to areas innervated by V2 or V3 produce severe electrical pain
Pain believed to be caused by ephatic transmission (cross talking happening between nerves-result of demyelination)
Damage to CN V motor parts results....
in atrophy of muscles supplied by CN V 3
Masseter and temporalis musch = difficulty with mastication and speech
Tensor veli palatini = impaired opening of eustachian tube
Tensor tympani = heightened sensitivity to sound
Absent jaw jerk reflex = sensory (proprioceptive) and motor (innervation to masseter and temporalis muscles) components mediated by CNV
Describe the facial nerve
often classified as motor nerve but has sensory components also.
nucleus located in pons
Sensory = mediates taste from anterior two-thirds of tongue.
Motor: Innervates all muscles of facial expression including those in forehead, cheeks and lips.
upper part of face: bilateral innervation from UMN
Lower part of face: only ipsilateral (unilateral) innervation from LMN
Supplies stapedius muscle of inner ear
Sends motor impulses to rest of ear (wiggling ears)
There are also parasympathetic fivers fro lacrimation and salivation ( fivers travel to perifpheral ganglion, Postganglionic fibers innervate lacrimal glands and sumbandibular sublingual salivary glands.
The upper part of VII is ____ the lower is ____
Ipsilateral and unilateral
The facial nerve enters and exits cranium via..
internal acoustic meatus
What happens when there is damage to CN VII
Sensory: Diminished taste on anterior two thirds of tongue
Motor: Lacrimal and salivary glands have inability to control lacrimation and salivation
and the stapedius musle has heightened sensitivity to sound.
Facial paralysis depending on where lession is.
A lession on the umn of CN VII causes
weak or paralyzed lower face with a spared forehead.
A lesion of the lmn of CN VII causes
weakness or paralysis of all ipsilateral facial muscles.
Damage to the neuronal cell bodies in the corticobulbar tract of CN VII
means loss of voluntary control over lower muscls of facial expression on the contralateral side.
Describe Bell's Palsy LMN
Acute unilateral facial nerve paralysis
Thought to be caused by inflammation of CN VII
Treated with anti-inflammatory or antiviral drugs.
Damage to a LMN of CN VII means
there is paralisis on whole side of face.
A sensory nerve with the nucleus located in the medulla
Has two branches: cochlear branch (hearing), and vestibular branch (balance)
The vestibulochochelar nerve enters the cranium via...
the internal acoustic meatus.
What happens when there is damage to the CN VIII
Cochlear branch: unilateral or bilateral hearing loss that depends on locatio nof lesion (along peripheral or central auditory pathway) Possible tinnitus
innervates stylopharyngeus muscle that elevates pharynx during a swallow.
Parasympathetic fibers for salivation, fivers travel to a peripheral ganglion, postganglionic fivers innervate parotid salivary gland
Describe the sensory component of IX
Supplies pain, temerpature and tactile information from posterior one-third of tongue, mucosa of upper pharynxx including velum and tonsils, eustachian tube and middle ear.
Supplies carotid sinus baroreceptors and carotid body chemoreceptors which monitor blood pressure and blood oxygen concentration.
Posterior 1/3 of tongue
The carotid sinus receptors help ...
mediate bp by receiving sensory information and sending that information to the brain.
The glossopharyngeal nerve enters and exits..
via jugular foramen.
That happens when there is damage to CN IX
Motor: difficulty swallowing and controlling salivation
Sensory: loss of senstation to areas, loss of taste on posterior one third of tongue (hard to test clinically)
Absent gag reflex,
Normally tocuing either side of the posterior pharynx leads to bilateral contration of muscles and bilateral elevation of the soft palate. Sensory component mediated by ipsilateral glossopharyngeal nerve, motor component mediated by bilateral vagus nerves.
Describe glossopharyngeal neuralgia
Like trigeminal neuralgia
sudden paroxysms of severe electric pain in back and side of throat
pain can spread down from side of neck to front of ear to back of mandible
Describe CN X
A mixed nerve
Nucleus located in medulla
What is the motor component of the vagus nerve
innervates soft palate, pharynx, larynx and esophagus
There are also parasympathetic fibers projecting to thracic and abdominal viscera
three branches: Palatal (glossopalatine and levator veli palatine)
Allow you to interpret sensory information and make response to it.
The primary somatosensory cortex is
postcentral gyrus of parietal lobe (allows conscious awarenss of sensation and the ability to localize it :where the sensation is from)
The somatosensory area is
behind it (BA 5 & 7)
the meaning of what is being felt
Smell (olfactory sense)
Deep in temporal love along medial surface
Primary motor areas (precentral gyrus of frontal lobe)
Precise, conscious or voluntary movement of skeletal muscles
Their axons: from massive pyramidal or corticospinal tracts descend through brain stem and spinal cord
cross to contralateral (the other side) in brainstem.
BA 44 and 45
specialized motor speech area at base of pre central gyrus just above lateral sulcus in only one hemishere usually the left
word articultion and the movements necessary for speech
Damage to brocas area means...
expressive language deficits (could be receptive too) or if can still speak words are right but difficult to understand.
Complex movements associated with highly processed sensory info; also planning of movements
voluntary movements of eyes.
frontal eye fields
The primary visual cortex area handles info from contralateral retina (right visual field-->left side)
Receives input from the optic tract via the thalamus (LGN)
If the primary visual cortex is damaged
functinally blind because no conscious awareness of sight
Visual association area
Rreceives projections from area 17, process stimulus features including form, color, and motion.
What are the two visual systems in the occipital cortex?
"where" pathway (dorsal)
-Occipital to temporal
-Object recognition (object naming)
Primary Auditory Cortex
Auditory association area: interpretation of auditory input.Has shown to be modality independent language deficit.
Damage to 41/22
has shown to cause comprehension deficits for deaf individuals b/c auditory processing has been linked to comprehension.
Association Areas do what?
Control our ability to understand sensory information and coordinate a response.
somatic sensory association area
visual association area
somatic motor association area
Interpretation will be individualized even when the stimulus is the same.
This area is remodeled during adolescence until the age of 25; it coordinates the brain/body and inter-personal world as a whole
Executive funcitoning (working memory)
5,7,39,40 are found in the parietal lobes, what do they do?
In addition to processing sensory information (123) the parietal lobe is responsible for spatial cognition as well as some aspects of reading and writing.
What happens when damage occures on right superior parietal?
Damage here causes neglect (hemi-inattention)
Lesion to the parietal love (usually RH) individuals do not respond to meaningful information presented to the side opposite of the brain lesion. They do not process the left field.
40 & 39 are found in the parietal lobes, what do they do?
Alexia with agraphia
Alexia without agraphia
Reading and writing.
Acquired disorder of reading due to brain damage
Acquired disorder of writing due to the brain damage
Cannot read, but can write and understand words spelled alloud.
Visual stimuli goes from 17-__- to ___ to ___ to 4 for verbal output.
What are the areas involved in processing auditory information and semantics (the what)
What is Heschel's gyrus?
41 aka primary auditory cortex
processing auditory stimuli
projects to BA 42 for more detailed analysis of auditory information.
What is agnosia.
Bilateral lesion to occipital temporal cortex- inability to recognize objects
Cannot recognize object presented in visual modality, but can recognize objects when presented in auditory/tactile modality
Bilateral/unilateral lesion to occipital-temporal cortex (FFA) -inability to recognize familiar faces.
Damage to posterior area in temporal lobe means
they don't have multiple representations of the same item.
Involved in semantics/word meaning
comprehension of auditory/visual languag
What is aphasia?
acquired disorder of language due to brain damage.
Brodmann areas 6,8,9,10,11,44,45
In addition to outputting motor information (4) the frontal lobe is involved in higher cognitive functions (executive function, planning, reason) as well as the coordination of motor movements for the production of speech sounds and syntax.
Programming motor sequences (6)
Frontal eye fields (8) involved in planning eye movements.
involved in executive functioning, reasoning and judging
What is frontal lobe dysfunction
apathetic/indifferent, difficulty changing strategies, social disinhibition, perseveration or repetition of an old behavior despite a demand for a new behavior.
involved in language output.
lesion in 44 or 45
results in slow effortful speech with prominent articulatory errors.
What are the subcortical structures>
The thalamus AKA does what
process and relay sensory information
the relay station of the brian
processes all sensory information (except smell)
Projects motor information to cortex
Plays a role in memory.
What is the input and output for thalamus
input: sensory tracts (except olfactory)
output: projects to the cortex and other subcortical regions
Integration of motor information from cerebellum and basal ganglia
There are how many thalamic nuclei?
What do lesions to the ventral posteriomedial nucleus and ventral posterolateral nucleus cause
loss of all forms of sensation, including light touch, tactile localization and discrimination and muscle joint sense from the opposite side of the body.
What is Korsakoff's syndrom
Damage dorsomedial nucleus of the thalamus and the mammillary bodes
meager content in conversation
what are two groups of structures that form a cohesive functional unit
what is the limbic system
is a complex set of brain structures in the telencephalon and diencephalon that lies on both sides of the thalamus, right under the cerebrum
It directly connects the lower and hight brain functions
It influences emotions, the visceral responses to those emotions, motivations, mood and sensations of pain and pressure.
Your ability to have and interpret behaviors
What structures are in the limbic system?
Describe the hippocamus...
what results from damage here?
involved with converting recent memory to long term memory.
injury to both amygdala nucleus and the hippocampus produces a greater memory loss than injury to either one alone.
Describe the function and what happens with lessions for the Amygdala.
Processing emotion and memory
Learned emotional responses (mainly fear)
-tameness-reduced emotional excitability
-normalization of behavior in patients with severe urbach-wiethe disease.
What is a fornix?
fiber bundle that carries part of the outflow of the hippocampus to the mammillary bodies.
Describe the function of the hypothalamus
A collection of nuclei with a variety of functions
controles the release of 8 major hormones by the pituitary gland (just inferior to the hypothalamus
control of food and water intake
sexual behavior and reproduction
circadian rhythm and daily cycles of physiological state and behavior
mediation of emotional responses.
Describe the role between the hypothalamus and temperature regulation
When body temperature is elevated, neurons in the anterior part of the hypothalamus turn on mechanisms for heat dissipation
With a lesion = hyperthermia
When body temperature is depressed, neurons in the posterior part of the hypothalamus are responsible for heat production
With a lesion= hypothermia
Describe the cingulate gyrus
Recieves input from the thalamus and neocortex
highly influential in linking behavioral outcomes to motivation
This role makes the cingulate cortex highly important in disorders such as depression and schizophrenia
It plays a role in executive function
For schizophrenia, the tx is...
blocking limbic receptors to dopamine acceptors
Alzheimer's disease is an abnormality in the
Rabies virus attacks
The hippocamus and infected patients show changes in emotional state.
Describe the basal ganglia
Functional network of structures connecting the cerbreal cortex and thalamus
the basal ganglia are associated with a variety of functions including, voluntary motor control, procedural learning relating to routine behaviors or habits
The basal gangia is made of the
Striatum (caudate nucleus and putamen)
Where is the basal ganglia?
Found on both sides of the thalamus, outside and above the limbic system but below the cingulate gyrus and within the temporal lobe.
Describe the Caudate nucleus
C shaped gray matter lateral to the thalamus:
1: head: continouus with the putamen or lentiform nucleus
body: forms the floor of the body of the lateral ventricle.
tail: terminates in the amygdaloid nucleus.
Describe the Putamen
the putamen lies just under and behind the front of the caudate
It appears to be involved in coordinating automatic behaviors such as riding a bike, driving a car, or working on an assembly line.
Problems with the putamen may account for the syndrome of Tourette's
Describe the Globus Pallidus
Located just inside the putamen with an outer part and an inner part
It receives inputs from the caudate and putamen and provides outputs to the substantia nigra (function is to control eye movements)
Describe the motor pathway
Thalamus--resting state, inhibits movement (neurotransmitters called GABA tell neurons to fire) Released from inhibition-->cortical activation-->movement
Inhibitied-->cortex not activation ---> no movement.
What are the 2 pathways that control movement through the BG... Describe both.
Direct pahtway (excitatory to movement)
-disinhibit thalamus--->activates cortex ---->movement (if you damage this your overly disinhibit the thalamus)(end state is hyperkinetic)
0Inhibitory to movement
-Inhibits thalamus --->inactiveated cortex -->No movement (end state is hypo kinetic)
*These two systems have competing effects of movement- so there is a balance between the two systems.
Describe cause of parkinsons disease and symptoms
steady loss of the dopaminergic function of the substantia nigra pars compacta
is a disease of the elderly and usually presents as a spontaneous intracerebral hemorrhage rather than as a transient focal neurological syndrome
What are risk factors of a stroke?
High cholesterol (hyperlipidemia)
Transient ischemic attacks.
What is the effect of hypertension on large vessels?
predisposes to accelerated formation of plaque
more common to formation of plaque (atheroma) in large arteries
What is the effect on small vessels?
deep areas of brain recieve their blood supply from end arteries, hypertension results in damage to small vessel wall and eventually occlusion resulting in infarction of a small area which at post mortem is visible to the naked eye as a small hole. May reuslt in aneurysms in basal ganglia and when they burst massive bleeding is the result.
what are the three major pathological processes stroke is caused by?
Thrombosis: a blood clt forms within a blood vessel in the brain
Embolus: a blood clot forms within the heart or a major blood vessel of the brain (outside brain or major artery)
Bleed: hemorage, weakness of artery and blood leaks out.
Often, only two groups are considered.
1. thrombo-embolus- infarctions
What is a lacunar?
A very small blood vessel of the brain progressively narrows until completely occluded.
For the purposes of stroke, the brain is divided into what two areas?
Anterior circulation: the part of the brain which recieves blood supply from the carotid circulation which therefore includes the territory of the middle cerebral artery and the anterior cerebral artery.
Posterior circulation: the region of the brain which receives its blood supply from the vertebral, basilar and posterior cerebral arteries.
MCA infarction involves...
cortical branches and deep perforating leticulo-striate arteries.
Emboli(objects) derive from the following sources.
heart: left atrium and ventricle (fif patient foramen ovale, then right sided circultion also
Aorta: Atheroma of the aorta may five raise to emboli
Carotid: This gives rise to platelet-fibrin emboli or cholesterol emboli and is probably the commonest cause of embolisation to the brain.
Describe the subarachnoid hemorrahage
Rupture of a cogenital malformation the berry aneurysm. These are most commonly found in the region of the circle of willis and its neighboring vessels, one important syndrome is that of a posterior communicating artery aneurysm which gives rise to complete third nerve palsy with pupil dilation
Describe a hypertensive bleeds
these typically occur in the basal ganglia and give raise to a massive hemorrhage causing coma and contra-lateral hemiplegia. The may also occur more superficially.
this disorder of elderly people giving raise to hemorrhage hemorrhage particularly in the posterior regions of the brain.
What is an arteriovenous Malformations
are defects of the circulatory system that are generally believed to arise during embryonic or fetal develompent or soon after birth (can be anywhere in spinal cord or brain.)
A middle cerebral artery infarct
results in contralateral hemiparesis
contralateral upper motor neuron facial weakness
contralateral sensory loss
higher function cortical impairment - will be aphasia if left MCA infarction and possibly a neglect syndrome if right MCA infarftion.
loss of visual field in on the same side as weakness. (homonymous hemianopia: blind spot in right visual field of both eyes)
Anterior cerebral artery Infarction
Classically this causes weakness of the leg
damage to medial frontal lobe and cingulate gyrus you get akinetic mutism: patient who is extremely apathetic and often will not move unless forced to do so.
Weakness of right lower limb (right side of face spared and right upper limb less affect
Speech disturbance (dysphasia)
Apraxia of left side of body (inability to properly execute movements despite normal strength)
Disturbance of bladder control
Confusion initially, later personality change may occur
depends on where the blockage or hemorage is as to the size of the watershed area.
Deep or proximal strokes cause ischemia in the thalamus and or midbrain as well as in the cortex
involve only cortical structures
if on the left, a patient with acute vision loss in the right half of the visual field.
Describe the Infarct of the basilar artery
Obstruction usually causes death quickly-
Posterior cerebral artery
loss of half of the field of vision on the side opposite to the stroke
Ischemic injury to the thalamus may result in unpleseant burning pain over opposite side of body (thalamic syndrome)
vertigo at onset
cerebellar incoordintion of arm and leg on the same side.
Loss of pain and temperature sense of the half of the face that is on the same side as the stroke, and of the trunk and limbs on the side opposite to the stroke
difficulty in swallowing and speaking.
Describe horner's syndrome
small pupil, mild drooping of eyelid and lack of sweating of face on same side as stroke)
Caused by occlusion of a single deep penetrating artery arising directly from the circle of willis.
looks like swiss cheese in brain.
What are the 5 syndromes of lucunar strokes
Pure motor stroke: face arm or leg
Ataxic heiparesis: hours or day honest- legs mostly
Dysarthria/clumsy hand: hand weakness
Pure sensory stroke: numbness or unpleasant sensation
Mixed sensorimotor stroke: ipsilateral sensory impairment with weakness or paralysis.
Which is most common
Pure motor stroke/hemiparesis
What are 5 stroke scales used
Glascow coma scale: 1= dead to 5=good recovery
Barthel index 0-100 100 being good
Modified Rankin Scale 0=no symptoms 6- death
Hunt Hess Scale I= good V= Coma or death
NIH stroke scale - very very in-depth.
What is tratment of acute stroke patients?
urgent general supportive care
Management of serum glucose
Management of hypertension
Magagement of brain edema
The aim of treatment of the acute stroke is to
limit the extent of ischemia or to reverse the process completely.
What is recombinant tissue plasminogen activator?
tPA is a thrombolytic or a “Clot Buster” drug. This clot buster is used to break-up the
clot (by breaking down proteins used to form the clot) that is causing a blockage or
disruption in the flow of blood to the brain and helps restore the blood flow to the
area of the brain. It has a high risk of associated bleeding. TPA may only be given
within 3 hours of the onset of the stroke and if a CT Scan has excluded a bleed or a
large stroke. Large infarcts are excluded, because they have a high risk of becoming
Prevention of emboli
Heart: anti-coagulation is given routinely for atrial fibrillation, particularly if associated with mitral valve lesions, or if clot is seen in the left atrium or ventricle on echocardiograph
What is the treatment for bleeds?
Hypertensive basal ganglia bleeds are generally untreatable
AVMs and Berry Aneurysms are treated surgically before rupture.