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143 terms

Neuroscience - Neuroanatomy (lectures 2-8)

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Describe the major components of the CNS
Brain and spinal cord including cranial nerve II (plus the retina) and only the most proximal segments of the remaining cranial and spinal nerves
Describe the major components of the PNS
neuronal and associated non-neuronal cells outside the CNS
Describe the major components of the somatic nervous system (SNS)
Afferent (sensory) and Efferent (motor) components of all the peripheral nerves that communicate between the skin, skeletal muscles, joints and CNS
Describe the major components of the ANS
parasympathetic, sympathetic and enteric nervous systems
What is the boundary between the CNS and PNS
Redlich-Obersteiner's zone near the point of contact between sensory or motor roots and the brain or spinal cord - boundary for each myelinated axon overlaps with its first node of ranvier lying exterior to the brain or spinal cord
What are the 5 parts of the CNS
telencephalon, diencephalon, mesencephalon, metencephalon and myelencephalon
Telencephalon
cerebral hemispheres, basal ganglia, lateral ventricles (foramina of Monro - connects lateral ventricles with third ventricle), closely tied to olfactory nerves
What are the cerebral hemispheres
frontal lobe, parietal lobe, occipital lobe, temporal lobe, limbic lobe and insular lobe
Frontal lobe
MOTOR planning, language, judgment, working (short-term) memory
Parietal lobe
reception and perception of SENSORY information in the body (SOMATOSENSATION)
Occipital lobe
reception and perception of VISUAL information
Temporal lobe
reception and perception of AUDITORY and visual information - hippocampus (memory) and amygdala (emotion and fear)
Limbic lobe
functionally tied to emotion and memory
Insular lobe
varied functions - autonomic and interoceptive
Diencephalon
Thalamus, hypothalamus (and pituitary), Epithalamus, cranial nerve II, mamillary bodies and the third ventricle
Thalamus
modulates and relays sensory and motor information from basal ganglia and cerebellum to cerebral cortex
Hypothalamus
homeostasis and reproduction
Subthalamus
motor and sensory function
Epithalamus
endocrine function
Mesencephalon
midbrain - tegmentum (floor: including cerebral peduncles/crus cerebri), tectum (roof: corpora quadrigemina or superior and inferior colliculi), cerebral aqueduct, cranial nerves III and IV
Midbrain
VISION - contains neurons forming part of the motor system, regulates eye movements, promotes alertness/arousal
Metencephalon
Pons, cerebellum, rostral fourth ventricle, cranial nerves V-VIII
Pons
ventral region relays motor info from cerebral cortex to cerebellum, dorsal region involved in respiration, taste and sleep/wake cycles, regulates motor function
Cerebellum
receives somatosensory info from spinal cord, motor info from cerebral cortex and vestibular info from organs of inner ear - maintains posture and balance, SMOOTHES and coordinates movement by regulating motor centers
Myelencephalon
Medulla Oblongata, caudal fourth ventricle (foramina of Magendi [m for medial] and Luschka [L for lateral] - communicate between fourth ventricle and subarachnoid space, central canal of the medulla is continuous with the spinal central canal), cranial nerves IX - XII
Medulla Oblongata
some nuclei control respiration, BP, motor activity of neck and mouth, other nuclei receive sensory info from chemo and mechanoreceptors
Spinal cord
provides pathway for somatosensory info received from most of the body, carries motor info from brain to control somatic muscles and viscera
What are the layers of the cerebral cortex from dorsal to ventral
1- molecular (plexiform) layer, 2- external granular, 3-external pyramidal layer, 4- internal granular layer, 5- internal pyramidal (ganglionic) layer, 6- multiform layer
I - Molecular (plexiform) layer
very few neuronal somata, axons pass through or make connections, axons arising from this layer often travel parallel to the layer (and pia)
II - External granular layer
small granule cells (interneurons that inhibit) and some slightly larger pyramidal cells, communications with ipsolateral cortical areas (via association fibers)
III - External pyramidal layer
small to medium sized pyramidal neurons - communications with homotropic contralateral cortices (commissural fibers)
IV - Internal granular layer
No pyramidal neurons - interneurons receiving thalamocortical (sensory) input, contains Stria Gennari
V - Internal pyramidal (ganglionic) layer
medium to very large pyramidal neurons, major source of cortical (motor) output to brainstem and spinal cord, contains inner band of Baillarger
VI - Multiform layer
assortment of cell types - receive input from thalamus and cortical layers II, III, and V, axons project to superficial cortical layers and subcortically to the thalamus
Interpret the structural and functional features of the cerebral cortex and its connections with other parts of the CNS
Thalamic input (sensory) mainly in layer IV, corticospinal/corticobulbar (motor output) mainly in layer V
Deep within the cerebral white matter are collections of neurons that form the
basal ganglia - helps smooth movement (Huntington's disease)
What are the major components of the basal ganglia
caudate nucleus, putamen, glubus pallidus, subthalmic nucleus
Describe the anatomy of the midbrain
tectum on dorsal side, tegumentum, cerebral peduncles, interpeduncular fossa, cerebral aqueduct, substantia nigra (Parkinson's), medial lemniscus, red nucleus know how to draw
Describe the anatomy of the pons
cerebellar peduncles on dorsal aspect, 4th ventricle in between, corticospinal tract, medial lemniscus
Describe the anatomy of the medulla
olive (olivary nuclei), pyramid (pyramidal tract - crosses over just below medulla), medial lemniscus
Explain the distribution of the white and grey matter at the different spinal levels
white matter is myelinated axons, grey matter is cell bodies of neurons, marked enlargements at C7/8 and within the lumbar cord at L5 - reflect greater numbers of cells at these levels devoted to sensory and motor processing for the arms and legs
Explain the anatomy of the spinal cord
Dorsal horn, ventral horn, ventral sulcus, gracile fasciculus (carries info from lower body "grass"), cuneate fasciculus (info from upper limb), dorsal column (vibration and proprioception), central canal of spinal cord
Describe the structure of a peripheral nerve
myelinated by Schwann cells - nodes of ranvier (lots of ion channels for saltitory conduction), endoneurium (around a single nerve), perineurium (fascicles), epineurium
Which cranial nerve is not a peripheral nerve and what is the significance of this?
CN II - myelinated by oligodendrocytes - no chance of repair
Which cranial nerves have significant sensory functions
I, II, V, VII, VIII, IX, and X (1, 2, 5, 7, 8, 9, 10)
Which cranial nerves have significant motor functions
III, IV, V, VI, VII, IX, X, XI, XII (3-7, 9-12)
Which cranial nerves carry axons of cells belonging to the autonomic nervous system
III, VII, IX, and X (3, 7, 9, 10)
Name 2 important motor pathways from the CNS to the PNS
corticospinal and corticobulbar tract
Name 2 important sensory pathways from the CNS to the PNS
Dorsal column/medial lemniscal system and the anterolateral system (spinothalamic tract)
Corticospinal tract
STARTS in the frontal lobe, ENDS in the ventral horn of the spinal cord to interact with lower motor neurons that will innervate muscle, ROUTE: motor cortex layer 5 (pyramidal cell) -> corona radiata -> internal capsule -> crus cerebri (cerebral peduncles) -> pons -> pyramid -> decussation (cross over to the other side of the body) -> lateral corticospinal tract in spinal cord -> contralateral ventral horn. FUNCTION: activation of motor neurons in spinal cord
Corticobulbar tract
from cortex to brainstem - innervates cranial nerve nuclei
Dorsal column/medial lemniscal system
SENSORY - Vibration, proprioception and touch discrimination
Anterolateral system (spinothalamic tract)
SENSORY - pain and temperature
Transient ischemic attack (TIA)
Temporary lack of blood supply causing an acute loss of cerebral or monocular function - lasts less than 24 hours - caused by circulatory dysfunction - depriving parts of the brain of adequate blood
Reversible Ischemic neurological deficit
a TIA in which- recovery of functions is likely
Stroke (cerebrovascular accident)
rapidly developing loss of cerebral function due to cerebrovascular disturbance. Manifestations are irreversible or partially reversible.
Lobotomy
Surgical removal of the frontal cortex has been tried as a treatment for severe mental illness but resulted in unwanted complications (epilepsy, abnormal personality, lack of social inhibition); this procedure has yielded to the administration of psychoactive drugs
Phineas Gage had damage to his frontal lobe, explain what his symptoms may be
His personality deteriorated, yielding a vulgar, impulsive, emotionally reactive and unreliable drifter
X-ray native
X-rays are most useful for looking at diseases of the skull, e.g. internal erosion of the skull may indicate an expanding neoplasm.
Pneumoencephalography
a small amount of CSF is removed replaced by air - used to study ventricles - painful and dangerous - rarely used
Cerebral Angiography
contrast medium is injected through a large artery into either the carotid or vertebral artery. Looking for vascular abnormalities of the brain - arteriovenous malformations, aneurysms, stenosis, vascular obstructions, angioma (vascular tumor)
Digital Subtraction Angiography (DSA)
Radiographs with contrast medium are digitally subtracted; only vascular structures remain - better contrast (DYE APPEARS DARK). Indication for stenosis, abnormalities, occlusion of cerebral arteries
Myelography
inject contrast medium into subarachnoid space(lumbar puncture) to image the spinal cord - Detects intraspinal tumor or herniated disk
CT scan
X-ray source is rotated - gives axial slice. Can resolve white and grey matter, blood, cerebrospinal fluid and FRESH BLOOD (hemorrhages); indications - hemorrhages (increased intracranial pressure + head trauma with skull fractures), infarctions, abscesses, tumors
Epidural Hematoma
rupture of middle meningeal artery - looks like a biconvex disk on a CT - Lucid interval (talk and die)
Subdural hematoma
veins that traverse the meningeal layer of the dura from the subarachnoid space (bridging veins) are ruptured - large crescent shape - behavioral changes
Subarachnoid Hematoma
ruptured artery in space between arachnoid and pia (subarachnoid) - dendritic pattern on a CT - Thunderclap headache
T1 weighted MRI
Detects fatty tissues - CSF is black, good differentiation between white and grey matter. Infarctions are visible, can see perforations in the blood brain barrier when using contrast medium (gadolinium)
T2 weighted MRI
Detects watery tissues - CSF is white, weak definition between white and grey matter. Shows edema and other neuropathologies - MS (plaques of demyelination), AIDS (degeneration in encephalopathy), brain abscesses
Positron Emission Tomography (PET)
Use F-deoxyglucose (short half life) to show metabolism in the brain; used in epilepsy, Parkinson's, Brain atrophy. Disadvantages - need cyclotron to produce radiotracers
Single Photon Emission Computed Tomography (SPECT)
distribution of radioactive isotopes (99m Tc or 123 J), measurement with gamma camera to show perfusion in the brain; can give information on cerebral blood flow.
Operculum
lid that covers the insula (part of the frontal, parietal and temporal lobes
What gyri constitutes the limbic lobe
cingulate gyrus around the corpus callosum
Where is CN I
telencephalon (olfactory bulb, olfactory tract, olfactory cortex)
Where is CN II
diencephalon (optic chiasm/tract, lateral geniculate body
Where is CN III
Mesencephalon (Ventral - interpeduncular fossa)
Where is CN IV
Mesencephalon (Dorsal - caudal to inferior colliculi)
Where is CN V
Metencephalon (pons)
Where is CN VI
Metencephalon (ponto-medullary junction)
Where is CN VII
metencephalon (cerebellopontine angle)
Where is CN VIII
metencephalon (cerebellopontine angle)
Where is CN IX
myelencephalon (postolivary sulcus)
Where is CN X
myelencephalon (postolivary sulcus)
Where is CN XI
myelencephalon (postolivary sulcus)
Where is CN XII
myelencephalon (medulla, preolivary sulcus - between olive and pyramid)
Brodmann's Area 3, 1, 2
Primary somatosensory cortex (postcentral gyrus)
Brodmann's Area 4
Primary motor cortex (precentral gyrus)
Brodmann's Area 17
Primary visual cortex (back of occipital lobe)
Brodmann's Area 22
Wernicke's receptive speech area (left hemisphere, posterior portion of 22 including planum temporal - part of superior temporal gyrus)
Brodmann's Area 41, 42
Primary auditory cortex (Superior temporal gyrus)
Brodmann's Area 44, 45
Broca's motor speech area (left hemisphere, pars opercularis [44] and pars triangularis [45])
Uncus
mediates olfaction - can easily compress midbrain structures under pathological conditions
Explain the basic anatomy of the fornix
column, body, crus, fimbriae
What gyri make up the limbic lobe
cingulate gyrus and parahippocampal gyrus
What are the 4 layers of cranial meninges
2xDura (with dural venous sinuses inbetween), arachnoid (avascular) and pia (highly vascular)
Intracerebral Hemorrhages
rupture of intraparenchymal branches of subarachnoid arteries such as the lenticulostriate arteries (branches of the MCA supplying the internal capsule and basal ganglia)
What part of the meninges stabilizes the spinal cord
extensions of the pia mater - Denticulate ligaments
Describe the arterial supply to the brain, brainstem
Circle of Willis - Anastamotic (know pictures on 6-12 about what areas of the brain are supplied by which artery)
Describe the arterial supply to the spinal cord
2 posterior spinal arteries supply dorsal and lateral aspect, one anterior spinal artery supplies the ventral side - both anterior and posterior arteries have anastamotic connections, forming an arterial vasocorona
Epidural anesthesia
injection of anesthetics into the epidural space causes conduction block of adjacent spinal nerves
Aneurysm
local dilation of the wall of an artery (majority occur near branch points), dilation can cause severe compression of adjacent cranial nerves, rupture can have serious consequences
Embolism
occlusion of a vessel by a clot, cells, gas, etc - this may interrupt blood supply, leading to tissue death
Describe likely functional losses arising from obstructions of the arterial supply to the cerebral hemispheres, brainstem and spinal cord
know Brodmann's areas; know what each lobe does and which arteries supply them
Define the factors that influence blood flow in the CNS
Cerebral vessels can change their diameters (autoregulation) - brain arterioles constrict when high BP and dilate when BP is low so that cerebral blood flow is constant. Arterioles dilate when arterial CO2 is raised, constrict when arterial O2 or pH is raised
What are the 4 parts of the lateral ventricle
Anterior (frontal-lobe) horn, body (corpus - frontal and parietal lobes), posterior (occipital lobe) horn, inferior (temporal-lobe) horn
What constitutes the floor and lateral wall of the anterior horn of the lateral ventricle
head of the caudate nucleus
What forms the anterior wall of the inferior horn of the lateral ventricle
amygdala
Describe the ventricular system of the brain
lateral ventricles -> interventricular foramina of Monro -> third ventricle -> cerebral aqueduct -> fourth ventricle -> central canal of spinal cord
How does the fourth ventricle communicate with the subarachnoid space
2 foramina of Luschka (lateral - near the cerebellopontine angle) and the foramen of Magendie (at the caudal midline)
Apply the knowledge about the sites of CSF production and drainage
production = ependymal cells in choroid plexus in the lateral, third and fourth ventricle (NOT THE CEREBRAL AQUEDUCT). Drained into vascular system through arachnoid villa
Explain the circulation of CSF
from lateral ventricles through interventricular foramina of Monro -> third ventricle -> cerebral aqueduct -> fourth ventricle -> small amounts into central canal, rest is drained into subarachnoid space through 2 foramina of Luschka (laterally) and the foramen of Magendie (medially) -> follows SA space and returns to vascular system through arachnoid villa
Explain the main chemical and physical characteristics of CSF
clear, colorless, low in glucose, protein, K+, Ca2+, and cells; high in Na+, Cl-, Mg2+. Used for Buoyancy, shock absorption, chemical stability, reduction of ischemia and prevents traction on nerves and vessels
What is normal intracranial pressure (ICP)
65-200 mm H2O (5-15 mm Hg)
Non-communicating (obstructive) hydrocephalus
results from obstruction of interventricular foramina, cerebral aqueduct or the foramina of Luschka or Magendie - causes enlargement of the undrained ventricle
Communicating Hydrocephalus
impaired CSF absorption (arachnoid villa) - causes enlargement of all ventricles
Dural venous sinuses
spaces between two layers of dura in the brain, drainage of the blood from the brain is chiefly into these sinuses - no valves and usually triangular in shape, don't usually collapse because of fibrous dura
Name the 3 sources that the sinuses receive their blood
cerebral veins (great anastamotic vein into superior sagittal sinus, small anastamotic into transverse sinus, great cerebral vein of Galen drains into straight sinus), diploic veins - lie between layers of cranial bone, emissary veins - connect extracranial and intracranial veins
What are the unpaired dural venous sinuses
Superior sagittal sinus, inferior sagittal sinus, straight sinus and occipital sinus
What are the paired dural venous sinuses
Transverse sinuses, cavernous sinuses, sigmoid sinuses, sphenoparietal sinuses and the superior and inferior petrosal sinuses
List and identify the veins of the spinal cord
posterior median, 2 posterior lateral, anterior median and 2 anterolateral. Internal venous plexus of Batson is between dura and periosteum - VALVELESS
Localize the circumventricular organs
Pineal gland, Area postrema, Neurohypophysis, organum vasculosum, subfornical organ, subcommisural organ, median eminence of third ventricle (floor)
Pineal gland
Mediating circadian rhythms, melatonin
Area postrema
Body/fluid homeostasis, emetic physiology - VOMITING CENTER
Neurohypophysis
posterior pituitary
Organum vasculosum of the Lamina Terminalis (OVLT)
fluid and electrolyte balance
Subfornical organ
thirst regulating
Subcommisural organ
secrete various glycoproteins into the CSF
Median eminence of third ventricle
hypophysiotrophic hormones converge before they are conveyed into the pituitary gland
Thrombosis of the dural sinus
Caused by complication of infection, or in diabetic patients - cortical phlebothrombosis may occur in non-infectious conditions such as during the hypercoagulable state that follows childbirth
Explain the importance of the development of the brainstem
alar plates (afferent) get pushed laterally -> Motor CN's are medial, afferent CN's are lateral (mixed in-between)
Describe the surface structures of the midbrain
Ventral - peduncles, interpeduncular fossa and CN III; dorsal - superior (vision) and inferior (auditory) colliculi (corpora quadrigemina) and CN IV; Lateral - Cerebral peduncles and CN IV
Describe the surface structures of the pons
Ventral - basilar groove, middle cerebral peduncles, CN V-VIII; dorsal - superior cerebellar peduncles, middle cerebellar peduncles, sulcus limitans, rostral (ponitine) rhomboid fossa; lateral - cerebellar peduncles
Describe the surface structures of the medulla
ventral - anterior median fissure, pyramids, pre/post olivary sulcus, olives, CN IX - XII; dorsal - caudal (medullary) rhomboid fossa, hypoglossal and vagal trigones, obex and gracile and cuneate tubercles; lateral - pyramids, olives, pre/postolivary sulci, cuneate tubercle
Dorsal columns - medial lemniscal system
afferent - mediates tactile discrimination, vibration and fine touch
Spinothalamic tract (anterolateral system)
afferent - mediation of pain and temperature
Central tegmental tract
afferent - gives dopamine and monoamines to other structures
Lateral lemniscus tract
afferent - auditory
Recognize the names of afferent cerebellar pathways
dorsal and ventral spinocerebellar, cuneocerebellar, olivocerebellar, pontocerebellar, vestibulocerebellar, reticulocerebellar tracts
What arteries supply the midbrain
PCA, ACA and SCA
What arteries supply the pons
ponitine arteries (from basilar)
What artery supplies the inner ear and CN VIII
labyrinthine artery
What arteries supply the medullar
PICA and ACA
Wallenberg's (lateral medullary) syndrome
occlusion of PICA - ipsolateral facial anesthesia (spinal nucleus of trigeminal), contralateral extrafacial anesthesia (anterolateral system), ipsolateral ataxia/uncoordination (inferior cerebellar peduncle), vertigo and nystagmus (vestibular nuclei), dysarthria/dysphasia (CN IX and X), Horner syndrome (disruption of hypothalamo-spinal fibers)