Neuroscience - Module A

Front 1

Orientation in the Nervous System

Back 1

Front 2

Redlich-Obersteiner's

Back 2

- Transitional zone between the CNS and PNS
- Marked by the basal lamina of the surrounding Schwann cell, the myelinating cell of the peripheral nervous system

Front 3

Five parts of the brain

Back 3

During development, the forebrain (prosencephalon: diencephalon and telencephalon) flexes at its junction with the mesencephalon until its rostro- caudal axis corresponds to a line between the frontal and the occipital poles (in the anterior-posterior plane)

Front 4

Telencephalon

Back 4

- Lateral ventricles
- Derived from rostral prosencephalon
- Cerebral hemispheres
- Cerebral cortex
- Basal ganglia
- Foramina of Monro
- Closely tied to olfactory nerves
- Planning, driving of motor activity, perceptual and cognitive functions

Front 5

Diencephalon

Back 5

- Interbrain – derived from the caudal prosencephalon
- Thalamus = relaying, modulating sensory input, cortical activity
- Hypothalamus (and pituitary) = homeostasis
- Subthalamus = motor and sensory
- Epithalamus = endocrine
- 3rd ventricle
- CN II

Front 6

Mesencephalon

Back 6

- Midbrain
- Tegmentum (floor: including cerebral peduncles or crus cerebri)
- Tectum (roof: corpora quadrigemina or superior and inferior colliculi)
- Cerebral aqueduct
- CN III and IV
- Function = motor system, eye movements, alertness/arousal

Front 7

Metencephalon

Back 7

- Derived from the rhombencephalon
- Pons = motor from cortex, respiration, taste, sleep/wake
- Cerebellum (cerebellar hemispheres and vermis) = somatosensory from spinal cord, posture & balance, smoothes and coordinates movement
- Rostral fourth ventricle
- CNs V - VIII

Front 8

Myelencephalon

Back 8

- Derived from the rhombencephalon
- Medulla oblongata = respiration, B.P., motor activity of mouth
- Caudal fourth ventricle
- Foramina of Magendi and Luschka
- Central canal of the medulla is continuous with the spinal central canal
- CNs IX - XII

Front 9

5 parts of brain - MRI

Back 9

Front 10

Cerebral Hemispheres

Back 10

- Cortex, white matter, basal ganglia, amygdala and hippocampal formation
- Divided into: frontal, parietal, temporal, occipital, limbic and insular lobes

Front 11

Layers of the Cerebral Cortex

Back 11

Major portion (about 90%) of the cerebral cortex bears 6 layers, with each distinguishable by a characteristic size

Front 12

Layer I -- Molecular (plexiform) layer

Back 12

- Very few neuronal somata
- Apical dendrites of cells - deeper cortical layers
- Axons passing through or making connections

Front 13

Layer II -- External granular layer

Back 13

- Small granule cells (local interneurons that inhibit other cortical cells) and some slightly larger pyramidal cells
- Communications with ipsilateral cortical areas (via association fibers)

Front 14

Layer III -- External pyramidal layer

Back 14

- Small-to-medium-sized pyramidal neurons projecting from the cortex
- Communications with homotopic contralateral cortices (via commissural fibers)

Front 15

Layer IV -- Internal granular layer

Back 15

- No pyramidal neurons
- Interneurons receiving ascending sensory (thalamocortical) input - projecting to layers II/III
- Dense band of tangential axons that form the outer band of Baillarger, which is hypertrophic and visible to the naked eye in a discrete occipital region (forming the stria Gennari of the striate cortex)

Front 16

Layer V -- Internal pyramidal (ganglionic) layer

Back 16

- Medium-to-very-large pyramidal neurons.
- Major source of cortical output to the brainstem and spinal cord
- Contains a dense band of tangential axons (i.e., inner band of Baillarger)

Front 17

Layer VI -- Multiform layer

Back 17

- Assortment of cell types, including a few pyramidal cells
- Small cells receive input from the thalamus and from cortical layers II, III, and V.
- Axons of the cells in this layer project to superficial cortical layers and also subcortically

Front 18

Circuitry of Cerebral Cortex

Back 18

- Largest pyramidal cells are found in layer V of primary motor cortex and can make synaptic connections with caudal spinal motor neurons
- Axons of most thalamo-cortical neurons end in layer IV

Front 19

BASAL GANGLIA

Back 19

- Groups of neurons that are concerned with the initiation and organization of movement
- Includes:
- Caudate nucleus
- Putamen
- Globus pallidus
- Claustrum
- Lie close to the lateral ventricles

Front 20

Striatum

Back 20

caudate nucleus + putamen

Front 21

Lentiform nucleus

Back 21

putamen + globus pallidus

Front 22

Thalamus

Back 22

Relays virtually all sensory input to sensory cortices. It also processes output from the basal ganglia and cerebellum to regulate the motor cortex and hence movement.

Front 23

Hippocampus

Back 23

Processes much sensory information that is destined for long-term storage in memory within cortical circuitry.

Front 24

Amygdala

Back 24

Participates in emotional regulation, perhaps assigning an emotional valence to memory.

Front 25

Association White Matter

Back 25

- Myelinated axons carrying information from one cortical region to another within the same cerebral hemisphere contribute to association white matter.
- e.g. Repeating the spoken word typically requires transmission of signals from the left temporal lobe to the left frontal lobe via a band of association white matter called the arcuate fasciculus

Front 26

Commissural

Back 26

- Information must also pass from a cortical zone in one hemisphere to a homotopic site in the opposite hemisphere.
- e.g. Correctly naming an unseen object placed in the left hand requires transmission of information from the right parietal lobe to the left
- The largest cerebral commissure is the corpus callosum

Front 27

Projection

Back 27

- The cerebral cortex must also interact with subcortical sites
- e.g. Somatosensory input reaches the parietal lobe via white matter projections arising from the thalamus.

Front 28

Brainstem

Back 28

Front 29

Spinal Cord

Back 29

Front 30

Spinal Cord Cross–section

Back 30

Front 31

Distribution of White and Grey Matter in Cord

Back 31

- White matter contains myelinated axons carrying commands in descending tracts from the brain to the spinal cord. It also contains ascending axons carrying sensory information from the cord to the brain.
- Grey matter comprises neuronal cell bodies and dendrites. Spinal gray matter may control muscular activity. Other pockets of spinal gray matter process sensory information.

Front 32

Spinal Nerves

Back 32

The typical spinal nerve is formed by the union of dorsal and ventral nerve roots. Since the dorsal root, arising from its dorsal root ganglion, carries sensory fibers and the ventral root carries motor fibers, the unified spinal nerve is functionally mixed.

Front 33

Peripheral Nerve Functions

Back 33

- Carry both sensory and motor information
- Sensory information travels along axons of afferent neurons
- Motor information travels along the axons of the lower
motor neurons innervating skeletal muscle
- All cranial nerves, except CN II, are peripheral nerves

Front 34

Communication between CNS and PNS

Back 34

• Corticobulbar Tract - motor
• Corticospinal (lateral and anterior) tract - motor
• Reticulospinal (lateral and medial) tract - motor
• Rubrospinal Tract – motor
• Vestibulospinal (lateral and medial) Tract - motor
• Dorsal Column/Medial Lemniscal System - sensory
• Anterolateral System (spinothalamic tract) - sensory

Front 35

Corticospinal Tract

Back 35

- Starts in the frontal lobe - relevant cell bodies in layer 5 of the cerebral cortex project their axons to the spinal
- Many fibers forming the corticospinal tract end in the ventral horn of the spinal cord to interact with spinal motor neurons that will innervate muscle.

Front 36

Conventional (Native) X-Ray Imaging

Back 36

Native X-ray diagnostics indirectly show pathologies of the brain and spinal cord

Front 37

Pneumoencephalography

Back 37

a small amount of cerebrospinal fluid is drained and replaced with air. The air travels towards the cranium in an upright patient and will reduce the radiodensity of the ventricles.

Front 38

Cerebral Angiography

Back 38

X-ray representation of blood vessels with contrast medium applied through a catheter.

Front 39

Myelography

Back 39

Contrast agent administered via lumbar puncture.

Front 40

CT

Back 40

- X-rays pass from a rotating source around the head (or
other body part), with unabsorbed X-rays reaching a rotating detector
- After a rotation, the X-ray source and detectors are moved to a new plane, creating a new slice (tome).
- CT can differentiate bone, white matter, gray matter and fresh blood
- Infarctions and intracranial hemorrhages are readily detected by CT

Front 41

Epidural Hemorrhage

Back 41

- Biconvex accumulation of blood

Front 42

Subarachnoid Hemorrhage

Back 42

Blood in the subarachnoid space

Front 43

Subdural Hemorrhage

Back 43

- Reflect trauma-induced tearing of the dura or tiny cerebral veins that traverse the dura
- Crescent shape

Front 44

MRI - T1

Back 44

- Strong in fatty tissue
- CSF = dark
- T1 MRI differentiates gray-white and shows detail
- Infarctions are visible

Front 45

T1 MRI with Contrast

Back 45

Paramagnetic gadolinium reveals perforations in the blood brain barrier, such as those surrounding tumors

Front 46

T2 MRI

Back 46

- CSF = bright white.
- Weak differentiation of white and gray.
- Edema and neuropathology

Front 47

T2-weighted MRI

Back 47

A specialized MRI scan called FLAIR may better reveal lesions from multiple sclerosis than a standard T2-weighted scan.

Front 48

Comparison of T1, T1 w/Contrast and T2-Weighted

Back 48

Front 49

Positron Emission Tomography (PET)

Back 49

- Evaluation of the distribution of radioactive isotopes by a computational method (like CT, MRI) to show metabolism (e.g., glucose) in the brain.
- Radiotracer (e.g., 18F-deoxyglucose -- short half-life) is taken up by the neurons like glucose but not metabolized accumulation (marker for glucose metabolism).

Front 50

Single Photon Emission Computerized Tomography (SPECT)

Back 50

- Evaluation of the distribution of radioactive isotopes by a computation method (like CT, MRI) to show perfusion in the brain
- NOT metabolism
- Injection of a radiotracer, for instance 99mTc or 123I.

Front 51

Spinal Cord

Back 51

Front 52

Lateral Surface of the Brain

Back 52

Front 53

Insula

Back 53

Front 54

Olfactory Cortex

Back 54

Front 55

Fornix

Back 55

Front 56

Ventricular system

Back 56

Front 57

Epidural Hemorrhage

Back 57

Epidural hemorrhages
commonly reflect the
traumatically induced
rupture of meningeal
arteries (e.g., middle
meningeal artery), with a
fractured bone cutting the
vessel. During the episode,
blood forces the stiff
periosteal dura to separate
from the skull, yielding a
characteristic biconvex
mass adjacent to the fracture. Pressure arising from the accumulating blood compresses/distorts the brain. Dangers typically peak within hours of arterial involvement but may go unrecognized.

Front 58

Subdural Hemorrhage

Back 58

Subdural hemorrhages
commonly reflect trauma-
induced ruptures of the
delicate veins that traverse
the meningeal layer of the
dura from the subarachnoid
space. Bleeds arising from
tearing of the meningeal
dura are also subdural.
Because the pressure in the
venous system is much
lower than in the arterial
system, crescent-shaped
subdural masses of blood
often develop slowly before manifestations arise (e.g., hours-to-weeks).

Front 59

Subarachnoid
Hemorrhage

Back 59

Many arteries reside between the arachnoid and pia mater (surrounded by CSF within the subarachnoid space). These vessels may rupture with trauma or spontaneously (in cases of aneurysm). The leaking blood assumes a tree-like appearance, while following the sulci.

Front 60

Intracerebral Hemorrhages

Back 60

ntracerebral hemorrhages reflect rupture of intraparenchymal branches of subarachnoid arteries, such as the lenticulostriate arteries (indicated by black box), which branch from the middle cerebral artery, supplying the internal capsule and basal ganglia.

Front 61

Internal Carotid

Back 61

The internal carotid arteries ascend through the deep neck, the carotid canals of the petrous bones, and the cavernous sinus. They emit the ophthalmic and posterior communicating arteries. They divide, terminating as the anterior and middle cerebral arteries

Front 62

Vertebral arteries

Back 62

- 1st branches of the subclavian arteries
- Ascend through the transverse foramina of the upper 6 cervical vertebrae and enter the skull through the foramen magnum
- Emit the posterior inferior cerebellar arteries (PICA), which usually spawn the posterior spinal arteries
- The vertebral arteries then emit the anterior spinal artery before unifying to form the basilar artery

Front 63

Basilar Artery

Back 63

- Gives rise to the anterior inferior cerebellar arteries (AICA).
- The superior cerebellar arteries arise from the basilar artery, just before to its bifurcation

Front 64

Anterior and middle cerebral arteries

Back 64

Anterior and middle cerebral arteries are the terminal divisions of the internal carotid artery - reach ventral surface of brain just lateral to the optic chiasm

Front 65

Inferior View of Vessels

Back 65

Front 66

Middle Cerebral

Back 66

- Middle cerebral artery extends laterally in lateral fissure over the insula, sending branches to the lateral aspect of frontal, temporal, and parietal lobes
- Emits lenticulostriate arteries - basal ganglia and the internal capsule
- These arteries are particularly vulnerable to rupture and are a major source of intracerebral (periventricular) hemorrhage.

Front 67

Blood Supply - Lateral View

Back 67

- e.g. Occlusion of the left middle cerebral artery often yields language deficits, as this artery normally supplies cortical regions subserving verbal and literal elements of speech

Front 68

Arterial Supply of the Spinal Cord

Back 68

Two posterior spinal arteries supply the dorsal and lateral aspect of the spinal cord, and one anterior spinal artery supplies the ventral cord

Front 69

Epidural anesthesia

Back 69

olutions of anesthetics can be injected into the epidural space where they cause conduction block of adjacent spinal nerves.

Front 70

Epidural (extradural) hemorrhage:

Back 70

- Results from trauma to the side of the head where the skull is relatively thin and vulnerable to fracture
- Damage to the underlying vessel, the middle meningeal artery, causes the dura mater to separate from the inner aspect of the bone

Front 71

Aneurysm

Back 71

- Local dilation of the wall of an artery
- The majority occur near branches of vessels (mostly the internal carotid artery or its branches).

Front 72

Third Ventricle

Back 72

- Thin vertical cavity, occupying the midline between the diencephalic hemispheres
- Roof = choroid plexus and the body of the fornix
- Lateral walls = thalami, hypothalami, and subthalami
- Basal hypothalamic structures = floor
- Lamina terminalis and anterior commissure = anterior wall
- Epithalamus = posterior wall

Front 73

4th Ventricle

Back 73

It is connected to the third ventricle by the mesencephalic cerebral aqueduct, which is frequently involved in obstructive hydrocephalus.

Front 74

Choroid Plexus

Back 74

- Rich network of blood vessels of the pia mater that projects into each ventricle to form a semi-permeable filter between arterial blood and the CSF
- Layer of ependyma covers the plexus and lines the ventricles
- Stretches within the lateral ventricles from the temporal horn through the interventricular foramen into roof of the third ventricle

Front 75

CSF

Back 75

- Clear and low in glucose, protein, K+, Ca++ and cells relative to serum.
– CSF is high in Na+, Cl- , and Mg++ relative to serum
- 140mL = normal

Front 76

Circulation of CSF

Back 76

1. Lateral ventricles - 3rd ventricle via interventricular foramina (of Monro)
2. 3rd ventricle - cerebral aqueduct
3. Cerebral aqueduct - 4th ventricle
4. Small amounts of CSF trickle between the fourth ventricle and the central canal
5. Exits 4th ventricle into the subarachnoid space via the foramina of Luschka (lateral) and Magendie (medial)
- Extraventricular CSF follows the subarachnoid space.

Front 77

Reabsorption of CSF

Back 77

- Returns to the venous system through small membranous villi, the arachnoid granulations, located along the superior sagittal sinus
- Arachnoid villi react to pressure gradients between the subarachnoid space and venous system to form one- way valves, ensuring the unidirectional movement

Front 78

Sinuses

Back 78