Neurobiology Theme 1

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  • Created by: Splodge97
  • Created on: 19-05-17 10:44
What are visceral responses?
Those induced by the autonomic nervous system (as they occur deeper in the body)
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What is present in the grey matter?
Present at the peripherals of the brain and centrally in the spinal cord; contains cell bodies, dendrites, astrocytes and microglia
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What is present in the white matter?
Located centrally in the brain, laterally in spinal cord; contains microglia, myelinated axons and oligodendrocytes
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What do dorsal and ventral mean?
Dorsal = close to the body's centre. Venral = further from the body's centre.
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What is present at the brainstem?
Nuclei of the cranial nerves and cardiorespiratory centres for survival (as well as reticular system along the back)
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What is the corpus callosum?
Broad white matter tract, interneourones allow two hemispheres to communicate
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What is the action of the thalamus?
Acts as a relay centre for the brain; filters out unnecessary sensory information, transports afferent axons to apropriate cortices. Responsible for central sensitisation.
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What is the hippocampus the site of?
Memory generation and learning (through synaptic plasticity)
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What is the function of the gyri?
Increase surface area of the cortex so more neurones can be held there, increasing intelligence
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What is the function of the frontal gyri?
Involved in motor decisions (where association motor cortices located). Damage impairs cognitive function.
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What is determined at the frontal pole?
Executive decisions and personality. Damage has behavioural/emotional impacts.
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Where is the supraorbital gyrus? What does it control?
In frontal lobe, controls eye movements (performs small amount of visual processing). Damage prevents eye control/generates impulsiveness.
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What is the function of the supra-parietal lobe, angular gyrus and supramarginal gyrus?
Superior parietal cortices - responsible for associating names to visual information, responsible for some visuospatical awareness. Damage causes contralateral sensory neglect.
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What occurs at the occipital pole?
Where central vision processed. Damage causes chronic blindness (though blindsight may occur if association areas still active)
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What are the temporal gyri involved in?
Processing auditory information. Damage causes a loss of speech inhibition (keep talking) or impaired memory of visual material.
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What are primary cortical areas?
Directly related to movement/sensation; association areas connected to them (involved in more complex sensory/motor functions).
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What are multi-modal cortices?
Those with multiple functions (namely association areas adjoined to multiple primary cortices)
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What occurs upon damage to the pre-central gyrus?
Primary motor cortex impaired (involved in execution of movement), causes paralysis or difficulty performing/controlling movement
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What occurs upon damage to the post-central gyrus?
Primary somatosensory cortex damaged, causes sensory neglect on contralateral side
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What is the role of the olfactory cortex?
At the inferior surface of the frontal lobe, processes smell input
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What is the role of the premotor cortex?
Contributes to movement (integrating motor input into the primary motor cortex)
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What are Brodman's areas of the primary somatosensory cortex?
3b = main somatosensory processing. 3a = processes proprioception. 1 + 3b = processes cutaneous sensation. 2 = Tactile/proprioceptive inputs to determine size/shape of objects
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Where is the secondary somatosensory cortex? What is its function?
In superior aspect of lateral sulcus, inferior to primary somatosensory cortex. Involved in higher order sensory functions (sensorimotor and bilateral integration) as well as learning, attention and memory.
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What is the role of the somatosensory unimodal association cortex?
In parietal lobe; linked to primary somatosensory cortex and works with secondary somatosensory cortex so objects can be identified (by integrating sensory/memory information).
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What is the role of the posterior parietal association cortex?
Stretches across parietal and temporal lobes; mulitmodal so has sensory and visual function, allowing the context behind movement to be assessed and passed to the motor cortices.
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What is the role of the visual unimodal assocation cortex?
Across occipital and temporal lobes, has visual function and some auditory (multimodal)
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What is the function of the auditory uunimodal association cortex?
Across temporal and perietal lobes, determines features (pitch/loudness) of sound
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What is the function of the limbic association ares?
Present as part of the temporal lobe within the lateral fissure, regulates emotion
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What and where is Broca's area?
Inferiorly in the frontal lobe, associated with the lateral sulcus. Involved in motor speech processing (controls muscles needed to speak); damage causes aphagia (difficulty with spontaneous speech/speech motor control).
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What and where is Wernicke's area?
In corner of the temporal lobe at the end of the lateral sulcus. Involved in speech comprehension (conversion of thoughts to words); impaired use/development of language if damaged. Arcuate fasciculus (white matter tract) connects to Broca's.
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What is the role of the insular cortex and anterior cingulate cortex?
Present deep in the lateral fissure, part of limbic system (responsible for emotional response to pain)
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What and where is the supplementary motor cortex?
Passes in the central sulcus to run above the corpus callosum in the cingulate gyrus; seen superiorly in the frontal lobe. Involved in anticipation of required movement.
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What occurs in neurulation?
Neural plate forms from the primitive streak of the ectoderm layer --> lateral cells experience greater growth so plate deepens --> superior cells form neural crests --> inferior cells fuse (middle-->cranial-->caudal) to give neural tube
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What are neuropores?
Cranial and caudal, sacks in communication with amnion formed by fusion of neural tube from middle. Cranial closes at 25 days, caudal at 27.
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What do the neural crests form?
Dorsal root ganglia, melanocytes (form melanin), odontoblasts, C cells of thymus (secrete calcitonin), adrenal medulla (secretes catecholamines), autonomic ganglia, tracheal cartilages and Schwann cells
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What is the prosencephalon? What does it form?
Primary brain vesicle representing the forebrain; forms two secondary vesicles, the telencephalon (gives cerebral hemispheres and lateral ventrricles) and diencephalon (gives thalamus and 3rd ventricle).
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What is the mesencephalon?
Primary brain vesicles (doesn't split to form secondary); gives anatomical midbrain and cerebral aqueduct
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What is the rhombencephalon?
Primary brain vesicle representing the hindbrain; splits to form two secondary vesicles, the metencephalon (gives pons, cerebellum and upper 4th ventricle) and myelencephalon (gives medulla and lower 4th ventricle).
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What are neural tube deficits?
Diseases occuring through incorrect formation of the neural tube; exampples are spina bifida, hydrocephalus (end partially fused so fluid on brain) and anencephaly (part of head lacking, associated with Zika virus).
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What is spina bifida?
When fusion of the neural folds doesn't bring mesoderm with it, so the apropriate muscles/skin/bones don't form around the spinal cord
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What are the classifications of spina bifida?
Spina bifida occulta (isn't recognised at birth so lack of caution often causes paralysis), meningocele (sack of CSF accumulates in the meninges) and mylomeningocele (CSF sack formed by meninges has structures in them prone to damage)
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What is the interventricular foramen?
Allows communication (CSF flow) between the lateral ventricles
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Where is CSF generated?
In the choroid plexus (in the lateral and partially in the 4th ventricles, produces 70%) and empendymal cells (produce 30%, line ventricles and central canal of spinal cord)
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What is the cisternae magna?
Enlarged sub-arachnoid space between the under-surface of the cerebellum and posterior surface of the medulla
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What is CSF comprised of?
Traces of proteins, glucose and ions (calcium, sodium, potassium, chloride and magnesium)
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What are the functions of CSF?
Allows brain to float so traction reduced on vessels connected to it, lifting weight from the foramen magnum so the cerebellum doesn't slip through, cushioning brain from impacts, removing waste metabolites and providing a stable ionic environment
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Describe CSF flow to the spinal cord/cisternae magna
Choroid plexus (lateral ventricles) --> 3rd ventricle --> cerebral aqueduct --> lateral aperture --> 4th ventricle (choroid plexus adds more) --> central canal to spinal cord or median aperture then cisternae magna
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Describe CSF flow from the cisternae magna
May travel in sub-arachnoid space around back of cerebellum (entering sigmoid sinus) OR around spinal cord and within the sub-arachnoid space of the frontal lobe (through subarachnoid villi of parietal lobe into superior sgaittal sinus)
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What is proprioception?
Sense of relative position of different parts of the body/limbs, as well as strength/effort used in movement
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Describe A-beta fibres
Sensitive to light touch and proprioception; only present in pulp chamber, activated when food between teeth (myelinated so fast transmission)
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Describe A-delta fibres
Sensitive to noxious stimuli, extend into dentine so first to become inflamed in caries (indicate filling needed), pain short and sharp as myelinated
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Describe C fibres
Responsible for dull aching/burning of slow onset as unmyelinated. Present at root apex so indicate root canal/extraction necessary.
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What occurs in peripheral sensitisation?
Peripheral nociceptors become inflamed, increasing their responsiveness (normal stimuli produce pain, as in allodynia when touch on injury causes pain) or an excessive pain response (as in hyperalgesia, where pain in normal circumstances)
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What stimulates peripheral sensitisation?
Chemicals released by tissue damage/inflammation; namely ATP, histamine, serotonin, cytokines, bradykinin and neuropeptides
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What occurs in central sensitisation?
2nd order neurones that have recieved long term pain signals become sensitised via synaptic plasticity (occurs in the CNS - Rexed's lamina I and II, amygdala, thalamus or anterior cingulate cortex). May increase response strength/cause referred pain.
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What occurs in synaptic plasticity?
In central sensitisation/learning in hippocampus. Frequently activated 2nd order give more glutamate to 3rd order; AMPA + NMDA release mitogen activating factor (PKC and Ca2+ modulating protein activate), acts on transciption factors (more receptors)
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What is atypical pain?
Chronic facial pain without diagnosis; usually because the nerves cross the mid-line (may involve multiple/partial nerves). Example is atypical oligodontia (pain from extraction socket). Can't be treated.
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What is Bell's palsy?
Unexplained (possibly viral) and sudden paralysis on one side of the face. Often improves but one side permanently weakened (risk reduced if steriods in 72 hours). Unlike in stroke, forehead affected and no arm/leg weakening on affected side.
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What is Frey's syndrome?
After removal of part of parotid some parasymathetic secretomotor nerves lost, replaced by nerves supplying the skin so area sweats upon salavation
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What is neuralgia?
Severe, damage/irritation causes intermittent/excruciating pain. Commonly trigeminal neuralgia, usually unilateral pain upon touch to one dermatome. Often no cause, may be solved by removing nerve obstruction.
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What are the signs of stoke?
Facial paralysis (not occurring the forehead), slurred speech and arm/leg weakening on affected side
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What are the causes of stroke?
85% due to cerebral artery blockage, 15% due to intrachranial haemorrhaging (rapidly through atheroma or slowly through angioma).
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What is a berry aneurysm?
Lesions of abnormally dilated blood vessels filled with blood; develop slowly, burst to cause a sudden bleed.
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What are astrocytes?
Abundant CNS cells with a star shape; act as glial support cells which provide brain with structure and nutrients. Also monitor pH, inactivate/activate certain neurones and form scar tissue.
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What are microglial cells?
Small immunological cells of CNS, necessary as immune cells can't cross blood brain barrier (so brain pool for viruses); they initiate an inflammatory response
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What are oligodendrocytes?
Supporting myelinating cells of the CNS, encapsulate pairs of 50-100 neurones
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What are embryonic CNS stem cells?
Derive cells of the CNS (except microglia which come from hematopoietic stem cells so are mesodermal in origin). Differentiate into neural progenitors (form nerurones) or glial progenitors (form astrocytes or oligodendrocyte progenitors).
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What can oligodendrocyte progenitors form?
Oligodendrocytes or, when acting as adult stem cells post-natal, neurones or astrocytes
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Describe the arrangement of the blood-brain barrier
Tight junctions between endothelial cells of the blood vessels in the brain, second barrier of astrocytes (attached by their end-feet) which filter further (so very selective). Similar arrangement between the vesicles and CSF.
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What is the circle of Willis? Why is it prone to damage?
Arrangement of internal carotid, vertebral and basilar arteries which supply the brain; ensures blood flow continues to one side if damaged. Susceptible to atheroma/angioma as thin/weak walls, also exposed on brainstem.
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What does the opthalmic artery supply?
Branch of the internal carotid, supplies the retina and dura mater (including the arachnoid mater and pia mater)
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What does the posterior communicating artery supply?
Branch of the internal carotid, supplies the thalamus, hypothalamus and hippocampus
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What does the anterior cerebral artery supply?
Branch of the internal carotid, supplies the medial cerebral hemispheres and parts of the frontal and parietal lobes
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What does the middle cerebral artery supply?
Branch of the internal carotid, serves the leteral cerebral hemispheres, parts of the temporal/occipital/parietal lobes, basal ganglia and internal capsule
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What results from damage to the middle cerebral artery?
Hemipariesis (unilateral paralysis as one primary motor cortex damaged), inattention/sensory neglect (as somatosensory cortex damaged), visual field deficit (as visual association cortex damaged) or dysphagia (when Broca's/Wernicke's damaged)
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What does the superior cerebellar artery supply?
Branch of the basilar artery which supplies part of the pons and midbrain as well as the superior cerebellum
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What does the anterior inferior cerebellar artery supply?
Branch of the basilar artery which supplies the ventral and inferior cerebellum and parts of the pons
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What do the pontine arteries supply?
Four branches of the basilar artery, project a short distance to the pons
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What does the labyrinthine artery supply?
A branch of the basilar artery which supplies the cochlea and semi-circular canals
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What does the posterior cerebral artery supply?
A branch of the basilar artery which supplies the midbrain, thalamus and parts of the temporal and medial lobes of the cerebral hemispheres
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What does the anterior spinal artery supply?
A branch of the vertebral artery, supplies the medial medulla and superior spinal cord
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What does the posterior inferior cerebellar artery supply?
Branch of the vertebral artery supplying the lateral medulla and the posterior cerebellum
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What occurs in TACS (total anterior circulation strroke)?
Large stroke in anterior/middle cerebral artery areas, usually through middle cerebral artery blockage. Causes unilateral weakness, sensory deficit (of face, arm and leg), homonymous hemianopia (vision issues), dysphagia and visuospatial disorder
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What occurs in PACS (partial anterior cirrculation stroke)?
Cortical stroke to anterior/middle cerebral artery areas but only due to partial artery damage (so symptoms same as TACS but fewer/less severe)
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What occurs in POCS (posterior circulation syndrome)?
Posterior arteries are blocked leading to cerebellar/brainstem syndromes, loss of consciousness or isolated homonymous hemianopia (less severe visual issues)
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What occurs in LACS (lacunar syndrome)?
Subcortical stroke due to small vessel damage causing loss to the internal capsule/pons. Results in unilateral weakness, sensory deficit, pure sensory stroke (equal face/arm/leg dysfunction) or ataxic hemipariesis (reduced cerebellar/motor function)
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What causes vascular occlusions?
Bursting of smaller arteries to the brain, causing localised/less severe symptoms; for example damage to the posterior cerebellar artery reduces visual function
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What is locked in syndrome?
Serious vascular occlusion causing complete paralysis of all voluntary muscles (except the extraocular muscles, as nerves supplying these only in the brain). Results from damage to the pontine arteries (since most CNS neurones pass through the pons).
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