Neuroscience - Neuroanatomy (lectures 2-8)

Created by lcoghill 

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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)

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