Neuro Exam 2

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Function of blood flow to the brain

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Provide oxygen, glucose, and other nutrients, removes toxins

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Disruption of blood flow to the brain

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Stroke, brain tissue death, irreversible nervous system damage (tissue dies after four minutes without oxygenated blood, damage after two minutes

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Arteries

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Aorta, main artery: splits into common carotid (internal (anterior cerebral and middle cerebral) and external), vetebral artery, and subclavian artery

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Internal Common carotid artery

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Branch of common carotid, arrives at the base of the brain, provides blood to most of the cerebral cortex, divides into anterior and middle cerebral arteries

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Anterior cerebral

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Points straight up, supplies blood to the medial surface of the cerebral hemisphere (and the motor stip in that area), supplies cognition and motor (frontal cortex, basal ganglia, and limbic system)

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Middle

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Goes out sideways, responsible to blood flow of the lateral surfaces of the cerebrum, supplies the parasylvian region, largest branch, problems can lead to somatosensory problems and speech language function problems

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External Carotid artery

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Supplies face, tongue, and external parts of the head, fairly straight so less prone to blockages

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Subclavian artery

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Forms the arch of the aorta to the common and vertebral arteries

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Vertebral arteries

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Ascend along vertebral column and enter cranium through the foramen magnum, unite at the base of the medulla to form the basilar artery then split to form the posterior cerebral artery

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Basilar artery

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Sends blood to the cerebellum, inner ear, brain stem, occipital lobe, inferior temporal lobe, some of the thalamus, and the mid brain, problems in this area can lead to total blindness

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Posterior cerebral

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Issues often impact the visual field

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Major Blood Supply

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Internal carotid: Telencephalon, Diencephalon Vetebral Arteries: Cerebellum, Diencephalon, Spinal cord, Occipital, Inferior part of temporal lobes

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Circle of Willis

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Joins anterior cerebral, middle, and posterior cerebral arteries using communicating arteries, serves as a saftey mechanism because allows blood flow to the other side (only protects if blockage is before the circle of Willis), connected with anterior and posterior communicating arteries, blood from the internal carotid and basilar artery meet in the posterior communicating artery

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CVA

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Third major cause of death, hematoma is a collection of blood, embolic is a blockage based on a traveling particle like air bubble, fat, blood, etc, thrombotic is a blockage due to narrowing of the arteries (stenosis: narrowing of the artery), hemorrhagic is a bleeding type stroke based on a burts, cut, or aneurism (weaking of the arterial wall)

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Intracerebral hemorrhage

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Bleeding in brain tissue

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Epidural hematoma

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Bleeding between skull and dura

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Subdural hematoma

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Bleeding below the dura

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Eschiemia

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is lack of blood due to embolism or thrombotic stroke

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Necrosis

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Death of tissue

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Infarction

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Area of the brain that undergoes necrosis

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Deficits in ACA legions

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Paralysis, cognitive and emotional changes, apraxia of gait

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Deficits in MCA lesions

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Contralateral hemiplegia (weakness), cortical hypothesia (reduced sensation), heminopsia, aphasia, visual agnosia (inability to make meaning of what you see), aprazia, upper motor dysarthria (muscle weakness)

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Deficits with PCA

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Dyslexia, memory impairments, cortical blindness (loss of vision due to cortex injury, not eye injury, visual agnosia)

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Deficits with the vetebrobasilar system

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Brain stem blood supply (disarthria, dysphagia, locked in syndrome, arousal difficulties), cerebellar blood supply (ataxic dysarthria)

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Blood brain barrier

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Separates vascular system from brain tissue, semi permiable, can prevent some medicines your body needs from passing through, water, co2, glucose and anisthetics pass through, everything else including proteins and antibiotics filtered, slightly less protective in the body, area postream is a thinner area at the medulla that allows more through (controlls vomiting, monitors for toxins and triggers vomiting)

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Sensory System

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Afferent, integrated with brain stem, spinal cord, and cortex, pathways are first, second and third order neurons, general body sensation uses spinal cord and spinal nerves, sensation to head and vocal mechanisms is cranial nerves

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Shrringtons classification of senses

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Exteroceptors, proprioceptors, interoceptors

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Exteroceptors

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Itching, tickling, vision, smell, hearing, superficial touch, tactile (mechanoreceptors, activated by vibration etc), temperature (thermoreceptors, activated by change in temperature), Pain (nocireceptors, activated by tissue damage)

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Proprioceptors

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Deep sensation in muscles and joings, deep pain, provides CNS information for reflexes and muscle movement, found in muscles, tendons, and joint, activated by initation or cessation of movement, muscle spindles (in the belly of muscles), golgi tendon organs (located in insertion of skeletal muscle into the tendons)

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Interoceptors

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Information from the viscera (internal organs)

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Photoreceptors

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Respond to light and vision

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Chemoreceptors

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Respond to smell and taste

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Thermoreceptors

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Respond to temperature change

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Mechanoreceptors

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Respond to movement

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Nocireceptors

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Respond to pain

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Neuronal ordering: First order

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In the periphery (in the ganglia), distal axons of cell bodies that receive sensory input, information enters the spinal cord through the dorsal root ganglia

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Neuronal ordering: Second order

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In the dorsal grey matter of spinal column, grouped into tracts, where information crosses over (decussates) for contralateral organization, goes all the way to the thalamus

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Neuronal ordering: Third order

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From the thalamus to the internal capsule to the cerebral cortex

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Doral column lemniscus system

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Fine touch, pressure, vibration, proprioception (fasciculus gracilis: sensation on lower half of body, fasciculus cuneatus: sensation on upper half of body)

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Anterolateral system

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Crude touch, pain, temperature (lateral spinothalamic tract: decussates where it enters the spinal cord, anterior spinothalamic tract)

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Lesion in lateral ventral gray matter or brain stem level

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Results in loss of sensation on the opposite side below the injury

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Damage to dorsal root ganglia

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Loss of sensation on ipsilateral side below injury

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Reflex Arc

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Allows rapid response to stimuli, involves sensory neuron, interneurons (relay neuron that connects sensory and motor neurons), motor neurons, relay occurs at the level of the spinal cord, not the cortex

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Sclera

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White of the eye

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Cornea

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Covers the iris and the pupil, transparent, anterior part of the eye, cornea and lens refract light

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Iris

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Colored portion of the eye, muscle portion, relaxes and contracts to keep light in or keep light out

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Lens

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Focuses light onto the retina at the back of the eye, made up of multiple layers of protein

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Retina

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Rods and cones are photoreceptors (rods help with perception of dim light, night vision, black white and gray, and detect movement and shape. Cones help with visual acuity, color vision (red, green, and blue), and function in daylight), rods and cones synapes with first order neurons

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Fovea

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Center of the macula (which is the center of the retina), fovea has the greatest concentration of cones and the most acute vision

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Optic disc

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Where retinal fibers come together to enter the optic nerve

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Aqueous humor

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Anterior to pupil, filled with CSF like fluid

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Vitreous humor

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Gelatinous substance that gives the eye its shape

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Visual Pathway

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Optic nerve travels posteriorly, at the optic chiasm some contralateral and some ipsilateral fibers, continue on to lateral geniculate body of the thalamus then to optic cortex. Some fibers terminate at midbrain in the superior colliculus which mediates reflexes to vision, head, and neck movement

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Visual Field

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Area outside in the world that you see

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Retinal field

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What is projected onto the retina

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Temporal and Nasal fibers

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Fibers temporal to the fovea in the RF connect to the cortex ipsilaterally, fibers nasal to the RF connect to the cerebral cortex contralaterally, in the occipital lobe everything is upside down and backwards in relation to the VF

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Binocular vision

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Information from the retinal field of each eye, merge into one image, contributes to depth perception

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Monocular vision

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Portion of the VF seen only in one eye

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Diplopia

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Double vision, improper coordination of the eyes, caused by problems with muscle control

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Lesions anterior to optic chiasm

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Loss of vision in the same eye

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Lesion posterior to optic chiasm

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Loss of visual field on opposite side in both eyes

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Color vision problems

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Protanopic (lacks red cones, trouble with red green discimination), Deuteranopic (lacks green cones, trouble with red green discrimination), Tritanopic (lacks blue cones, trouble with blue green discrimination), generally genetic but can be from other like anoxia

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Reflexes

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Pupillary reflex (constriction of pupil), accommodation reflex (bending or turning light wave, presbyopia: decreased ability to bend light wave)

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Visual Cortex

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Primary visual cortex is the striate cortex (Brodman’s 17), Association areas are also known as the extra striate cortex and include connections to inferior temporal lobe and posterior parietal lobe (18 and 19)

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Agnosia

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Failure to know (visual agnosia is a legion in the extra striate cortex supplied by the posterior cerebral artery)

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Apperceptive visual agnosia

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Inability to percieve, cannot recognize objects, copy objects, match shapes, visual acuity color and motion are preserved

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Associate visual agnosia

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Perception occurs but cannot attatch meaning, cant name what the object is but can demonstrate how to use it

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Prosopagnosia

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Difficulty recognizing familiar faces

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Hemispatial agnosia

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Visual neglect on one side of the body

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Alexia without agraphia

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Cant comprehend written information but can still write

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Homonymous hemianopsia

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Loss of half of the VF in both eyes on the same side, can occur with or without neglect (occurs with lesions along the optic tract after the optic chiasm)

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Cortical visual impairment

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Damage to the bilateral visual cortex (not the eyes), can possibly detect movement or shapes but mostly blind, some people (mostly childre) can improve