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Flashcards in A & P - Neuro Deck (75):

vessels under the skull and in the dura

-middle meningeal artery
-branch off of external carotid artery
-feeds meninges


vessels on top of the brain and in the arachnoid

-anterior, middle and posterior cerebral arteries
-branches of the circle of Willis
-feed the brain


5 layers (superficial to deep) of scalp

-connective tissue
-loose areolar tissue


nerve supply of scalp

-supratrochlear and supraorbital: CNV1
-zygomaticotemporal: CNV2
-auriculotemporal: CNV3
-greater, lesser and third occipitals: C2+3 spinal nerves


MENINGES 3 layers



middle meningeal artery tear

-blow to the side of the head
-epidural hematoma
-compresses cerebrum = bad


cerebral vein tear

-elderly who falls and hits head
-subdural hematoma
-compresses cerebrum = bad


cerebral artery tear

-ruptured aneurysm
-Weakened area of arterial wall
-Worst headache of my life
-subarachnoid hemorrhage
-compresses cerebrum = bad


Cerebrospinal Fluid (CSF)

-physical support
-pressure diffuser
-immunological shield
-carries away metabolites
-made in the ventricular system by specialized cells called the choroid plexus
-fills the subarachnoid space
-filters thru subarachnoid granulations into the venous sinus (drainage) system of the brain
-Hydrocephalus is a condition caused by abnormalities of CSF production, flow or drainage.
-CSF is the fluid obtained from a Lumbar Puncture



outermost portion is cortex, containing sulci and gyri and 4 lobes;
split into R+L hemispheres
executive function, personality



contains 2 lobes and 3 peduncles



thalamus + hypothalamus



midbrain + pons + medulla oblongata



a depression or fissure in the surface of the brain



an upfolding of the brain cortex


superior temporal gyrus

Wernicke’s Area, the sensory speech area


angular gyrus

comprehension of visually
presented materials (reading)


inferior frontal lobe

pars triangularis,
Broca’s Area, the
motor speech area


precentral gyrus

primary motor
area, the motor strip


postcentral gyrus

primary sensory area,
the sensory strip


supramarginal gyrus

language perception and processing



-The outside of the brain is gray matter, made up of neuron cell bodies.
-The inside of the brain is white matter, where all the cell body axons travel.
-Axons travel together from cortex to cord as the corona radiata (aka projection fibers).
-Specifically, the motor axons from the corona radiata come together as the internal


internal capsule

-the motor fiber passageway thru the caudate, thalamus and lentiform nucleus, on the way to the midbrain’s crus cerebri.
-Forms the main highway for the main highway for the input and output fibres of the cerebral cortex
-It is “V” shaped on horizontal section with the concavity directed laterally
-Traced below the capsular fibres occupy the crus cerebri of the mid brain, passes through the pons and forms the pyramid of medulla oblogata.
-In the lower medulla about 80% fibres decussate and enter into the cotralateral lateral funiculus of the cord as the lateral cortico-spinal tract.
-18% fibres descend uncrossed as the anterior cortico- spinal tract, which however terminate in the opposite spinal grey matter after crossing in the anterior white commissure
-2% fibres descend and terminate uncrossed in the lateral cortico-spinal tract


Motor fibers

-run down to the crus cerebri, and make their way thru the pons to the medulla.
-Here they are called the pyramidal tracts (pyramid), and they cross (decussate): Left Cortical Fibers cross to the right of the cord, and Right Cortical Fibers cross to the left of the cord.
-Actually, only ~80% cross over, and 20% continues down on the same side. The ones that cross over in the medulla become the cord’s Lateral Corticospinal Tract.
-The ones that stay on the same side become the cord’s Ventral Corticospinal Tract, which crosses over in the cord.



spaces deep within the brain, CSF factory and drainage system


Nerve Fibres of the Cerebrum

1. Association fibres
2. Commissural fibres
3. Projection fibres


Association Fibres

-Fibres connect the cortical areas of the same hemisphere
-Short- connects adjacent gyri
-Long- connects gyri separated from one another by considerable interval, eg:
-Cingulum-: fibres of the limbic lobe and lies within the cingulate gyrus, forms a part of the papez circuit
-Uncinate (arcuate) fasciculus-: hooks around the floor of the stem of lateral sulcus. Connects Broca’s area and the orbital surface of the frontal lobe with the temporal pole


Commissural Fibres

-Connect wide areas of cerebral cortex of the two hemispheres across middle line
-Fibres may be homotopical ie. connect identical areas or heterotopical ie. Connect non-identical areas
-Five sets of commisural bands are present:
-Corpus callosum, ant, hippocampal, habenular, and post commisure,


Corpus Callosum

-Rostrum: consists of fibres connecting the orbital surface
-Genu : consists of fibres(forceps minor) connecting the medial and lateral surfaces of the frontal lobes
-Trunk : consists of fibres connecting wide areas of cerebral cortex
-Splenium : consists of fibres (forceps major) connecting the occipital lobes.
-Makes information stored in the cortex of one hemisphere available to corresponding cortical areas of the opposite hemisphere
-Corpus callosum operates cooperatively at the superficial level
-Anterior commissure unifies the emotional responses of the two sides of the brain


Projection Fibres

-Fibres connect the cerebral cortex with the sub-cortical grey matter of the basal ganglia, thalamus, and with the nuclei of the brain stem and spinal cord
-Corona radiata : fibres from the entire cortex converge to the periphery of the corpus striatum.The fan shaped arrangement of the fibres is called corona radiata
-Traced below the fibres are continuous with the fibres of the internal capsule


Basal Nuclei (Ganglia)

-Sub cortical collection of grey matter in the cerebrum which lie in close relation to internal capsule
-Essential constituents of the Extra Pyramidal System
-Initiates and provide gross control over skeletal muscle movements
-Functionally associated with the subthalamic nuclei (diencephalon) and the substantia nigra (midbrain)


Caudate Nucleus

-Forms an arched band of grey matter in conformity with the curvature of lateral ventricle

Consists of three parts:
-Head-: enlarged anterior end, bulges into the floor of anterior horn of lateral ventricle.
-Body-: continuation of the head backwards, from the level of interventricular foramen of Monro, along the floor of central part of lateral ventricle.
-Tail-: Runs downwards and forwards along the roof of the inferior horn of lateral ventricle.


Lentiform Nucleus

-Biconvex, wedge shaped, mass of grey matter.
-Narrow part of wedge faces medially.
-Divided by an external medullary lamina into an outer large part, the putamen and an inner small part, the globus pallidus.
-The globus pallidus is further subdivided by internal medullary lamina into outer and inner segments.


Amygdaloid Body

-Almond-shaped groups of nuclei
-Located deep within the medial temporal lobes
-Apparently continuous with the tail of caudate nucleus.
-Shown in research to perform a primary role in the processing of memory and emotional reactions, hence functionally more related to the Limbic System.
-Because of the multiple connections, the amygdala has been called the “window” through which the limbic system sees the place of the person in the world.
-Critical center for coordinating behavioral, autonomic and endocrine responses to environmental stimuli, especially those with emotional content.
-Helps in coordinated responses to stress and integrates many behavioral reactions involved in the survival of the individual or of the species, particularly to stress and anxiety.
-Responsible for making the person’s behavioral response appropriate for each occasion


Diseases of Basal Ganglia

-Parkinsons - Direct pathway
-Huntingtons - indirect pathway
-Hemiballism - indirect pathway
-tourette syndrome - indirect pathway
-Wilsons disease - direct pathway


Connections of Corpus Striatum - Direct pathway

-Excitatory input from the cerbral cortex projects to striatal neurons.
-Activated inhibitory neurons in the striatum (GABA neurons), project to and inhibit additional GABA neurons in the internal segment of the globus pallidus.
-The GABA axons of the internal segment of the globus pallidus project to the thalamus (VL)
-The double inhibition leads to a disinhibited effect on the thalamus.
-Net result is an increased level of cortical excitation and the promotion of movement.


Connections of Corpus Striatum - Indirect pathway

-Excitatory input from the cerbral cortex projects to striatal neurons.
-Activated inhibitory neurons in the striatum (GABA neurons), project to and inhibit additional GABA neurons in the external segment of the globus pallidus.
-The GABA axons of the external segment of the globus pallidus project to the subthalamic nucleus.
-The double inhibition leads to a disinhibited effect on the subthalamus, and thus causes excitation of the inhibitory GABA neurons in the internal segment of the globus pallidus.
-The net result of the disinhibition in the indirect pathway results in a decreased level of cortical excitation, and a suppression of unwanted movement.



-Masses of grey matter around the cavity of third ventricle
Consists of four parts:



-80% of diencephalon
-Superolateral walls of the third ventricle
-Connected by the interthalamic adhesion (intermediate mass)
-Contains several nuclei, named for their location
-Serves as a major sensory relay for information that ultimately reaches the neocortex.
-Motor control areas (basal ganglia, cerebellum) also synapse in the thalamus before reaching the cortex.



-Forms the most ventral and smaller part of the diencephalon
-Its functional importance is out of proportion to its size
-It is composed of numerous nuclei that have afferent and efferent connections with widespread regions of the nervous system namely the
- pituitary gland
- autonomic system
- limbic system.



-Most dorsal portion of the diencephalon
-Consists of pineal body and habenular nuclei
Pineal body:
-Small, highly vascularized structure situated above the posterior commissure
-Attached by a stalk to the roof of the third ventricle
-Contains pinealocytes and glial cells but no neurons
-Pinealocytes synthesize melatonin, serotonin and cholecystokinin
-Melatonin—helps regulate sleep-wake cycles*


Pineal Body-Clinical Correlates

Precocious Puberty
- In young males, pineal lesions may cause precocious puberty.
Pineal Tumors
- May cause obstruction of CSF flow and increased intracranial pressure.
- Compression of the upper midbrain and pretectal area by a pineal tumor results in Parinaud syndrome (impairment of conjugate vertical gaze & bilaterally suppressed pupillary reflex).



-Consists of biconvex mass of grey matter known as subthalamic nucleus
-Is involved in the basal ganglia circuitry (indirect pathway)
-Lesion causes hemiballismus (contralateral flinging movements of one or both extremities)


Functional Areas of the Cerebral Cortex

-Three general areas have been proposed to define the different motor and sensory areas in the brain


Primary motor areas

have direct connections with specific muscles for causing discrete muscle movements


Secondary motor areas

make sense out of the signals in the primary areas, provides patterns of motor activity or programs the sequence of movements


Primary Sensory Areas

detect specific sensations- visual, auditory, or somatic


Secondary Sensory Areas

analyzes the meanings of the specific sensory signals, such as
- interpretation of the shape or texture of an object in one’s hand
- interpretation of color, light, intensity and other aspects of vision
- interpretations of sound tones and sequence of tones in the auditory signals


Association Areas

Receive and analyze signals simultaneously from multiple regions of both motor and sensory cortices
Two important association areas are:
-Lesion of association area could lead to agnosia (inability to know familiar objects or persons).


Parieto-occipitotemporal Association Area

-Provides high level interpretative meaning from all the surrounding sensory areas
-Functional subareas are:
1. Analysis of spatial coordinates of the body
2. Wernicke’s area for language comprehension
3. Angular gyrus for visual processing of words(reading)
4. Area for naming objects


Prefrontal Association Area

-Functions in close association with the motor cortex
-Plans complex patterns and sequences of motor movements.
-Carries out thought processes in the mind
-Is involved in intellect, cognition, recall, and personality
-This function is aided by nerve fibres connecting the parieto-occipitotemporal association area with the prefrontal association area.
-Through this bundle the prefrontal association area receives much preanalyzed sensory information.


Speech Centers

-The dominant centers present four speech centers
Sensory Speech Area
-Wernicke’s area: Area 22 of the superior temporal gyrus comprehends spoken language and recognizes familiar sounds and words
-Area 39 of the angular gyrus stores visual images and recognizes the objects by sight
-Area 40 of the supra-marginal gyrus recognizes the objects with the help of touch and proprioception

Motor Speech Area
- Broca’s area : Area 44 and 45 of inferior frontal gyrus is the expressive speech center.
-The sensory and the motor speech areas communicate with each other by superior longitudinal fasciculus


Lesion of Wernicke’s area (area 22)

produces word deafness
-Patient is unable to interpret spoken words
-Can speak fluently with occasional uses of incorrect and meaningless words


Lesion of area 39

results in word blindness
-Inability to read(alexia) and write(agraphia)
-Patient can speak and understand spoken language


Lesion of area 40

produces astereognosis
-Patient is unable to recognise familiar object by touch and proprioception


Motor Aphasia (Expressive aphasia)

Damage to Broca's area. OK comprehension but distorted speech (talking nonsense, patients are aware of this)


Conduction Aphasia

-Damage to arcuate fasciculus connecting the Broca’s and Wernicke’s area - no connection between input and output areas
-Speech is fluent, comprehension is intact but repetition of spoken language is extremely difficult



-Visual area surrounds the calcarine sulcus on the medial surface of the occipital lobe (area 17, also called striate area). Fibers are from lateral geniculate body same side
-Because of the partial crossing, left visual field is projected to right hemisphere and upper visual field is projected to lower wall of cortex (below calcarine line). Macula lutea (the yellow spot) project to posterior one third of the visual cortex.
-Visual association cortex corresponds to area 18, 19. It receives info from area 17, function to relate the image to past visual experience. Lesion of area 18, 19 causes visual agnosia.



-Ventral wall of the lateral sulcus and the superior temporal gyrus (area 41, 42).
-Medial geniculate body is the principal source of fibers that end in auditory cortex. Contralateral ear predominate, same side is also substantial
-Auditory association cortex is at the floor of the lateral sulcus and posterior part of area 22 on the lateral surface of the superior temporal gyrus (also called Werbick’s area). Bilateral destruction of auditory association area causes auditory agnosia, fail to identify previous familiar sounds.



-Taste center is at the inferior end of the postcentral gyrus and extends into insula
-Nerve impulses from taste buds reach gustatory nuclei, then ipsilaterally to the medial division of ventral posterior medial nucleus of the thalamus, then project to cortex by thalamocortical fibers


Limbic System

-The limbic system mediates and controls all aspects of emotional and motivation drives such as desire for food, sex, feelings of anger, rage, love, depression, stress, hallucinations, PTSD
-Consists of interconnected core of cortical and diencephalic structures found on the medial aspect of each hemisphere
-It includes : Hypothalamus-in the center surrounded by two rings of subcortical structures, includes structures of rhinencephalon*
-Inner ring-: septum pellucidum, paraolfactory area, ant nucleus of the thalamus, portions of the basal ganglia, hippocampus and amygdala
-Outer ring-: orbitofrontal cortex, subcallosal gyrus, cingulate gyrus, parahippocampal gyrus and uncus.


Papez Circuit

-Connections of the limbic system is expressed by the Papez circuit
-It begins and ends in the hippocampus
-Axons of hippocampal pyramidal cells converge to form the fornix.
-Fornix projects mainly to the mammillary bodies
-Mammillary bodies in turn project to anterior nucleus of thalamus by way of the mammillothalamic tract.
-The anterior nucleus project to the cingulate gyrus through the anterior limb of internal capsule
-Cingulate gyrus communicates with the hippocampus through the cingulum



-Memory consolidation centre
-The hippocampus is an ancient area of cerebral cortex that has three layers.
-This is located in the medial aspect of the temporal lobe, forming the floor of the inferior horn of the lateral ventricle
-The ant end presents a bulbous extremity marked by a number of grooves, and resembles the paws of an animal, hence called pes hippocampi
-It is produced by the complex infoldings of dentate gyrus, cornu amonis and subiculum.
-On coronal section the hippocampus ic “C” shaped and resembles a ram’s horn.
-Hence the hippocampus is often called Ammon’s horn


Hippocampal Circuits

1. From cingulate gyrus via cingulum
2. From the septal nuclei
3. Commissural fibres from the opposite hippocampus
4. Profuse connections from the para-hippocampal gyrus via the perforant and alvealar path
1. Fornix forms the sole efferent projection fibres
2.Fornix begins as a continuation of alveus*


Hippocampus- its role in memory

-There are several areas involved in explicit memory.
-But the hippocampus plays a critical role in short-term memory, which is absolutely necessary if long-term memory patterns are to be established.
-Lesions of the hippocampus do not affect old, established memories. These lesions affect new declarative learning.
-The hippocampus is not only active in encoding memories but also in retrieval of them. Activation of the hippocampus can be seen in this case of learning about new surroundings and of retrieving directions.


Septal Area

-Includes neurons of subcallosal area and septal nuclei of septum pellucidum
-Forms a significant cell station of the limbic system
-Is connected to amygdaloid body through stria terminalis.
-Has extensive reciprocal connections with the hippocampus (via dorsal fornix),and Hypothalamus & midbrain reticular formation (via medial fore brain bundle)
-Electrical stimulation of septal areas inhibits aggression and produces pleasure reaction


Synopsis of isolated functions of limbic system

- Amygdala – aggression or fear response
-Hippocampal formation- arousal response
-Amygdala & Hippocampus – Recent memory
-Septal areas – inhibits aggression and produces pleasure reaction
-Reward centers- septal areas, hippocampus, hypothalamus
-Punishing centers- mid brain tegmentum, certain areas of thalamus and hypothalamus.



-The Microprocessor of the CNS
-The cerebellum processes input from other areas of the brain, spinal cord and sensory receptors to provide precise timing for coordinated, smooth movements of the skeletal muscular system.
-A stroke affecting the cerebellum may cause dizziness, nausea, balance and coordination problems.
-The Cerebellum connects to the rest of the CNS thru the pons via peduncles (superior, middle and inferior). -These large “arms” of the cerebellum wrap around into the pons.



The midbrain contains:
1. Anterior (in front of cerebral aqueduct)
cerebral peduncles (or crus cerebri):
huge collection of axons (descending
motor fibers) called the corticospinal
tracts, coming from the internal
capsule, going to the medulla
substantia nigra: reward, addiction and
movement (abnl in Parkinson’s)
2. Posteriorly (behind the cerebral aqueduct):
Corpora Quadrigemina (4 bodies)
2 superior colliculi
2 inferior colliculi
CN3+4 nucleus and fibers
(CN4 is the only CN which
comes from the post aspect of
the stem)
3. descending corticospinal tracts, and
ascending spinothalamic and dorsal
column tracts are passing thru



The pons contains:
1. nuclei responsible for respiration
2. nuclei responsible for sleep, bladder control and equilibrium
3. CN5-9 nucleus and fibers responsible for face sensation, face expression, eye lateral mov’t, hearing and taste (CN 5,7,9)
4. descending corticospinal tracts, and ascending spinothalamic and dorsal column tracts are passing thru
-the pons is fed by the basilar artery
and its tiny branches


Medulla Oblongata

The medulla contains:
1. pyramidal tracts (or corticospinal tracts) + pyramid (or pyramidal decussation)
2. olive = a group of gray matter assoc. with equilibrium
3. cardiac, respiratory, vomiting, vasomotor and autonomic centers = control of involuntary functions, such as RR, HR, BP!
4. CN 10/11/12 nuclei and fibers
5. medial lemniscus = dorsal column info comes up to medulla and becomes the med lemniscus, which decussates and continues higher to the thalamus
6. descending corticospinal tracts, and ascending spinothalamic and dorsal column tracts are passing thru
-medulla is mainly fed by the anterior spinal
artery (ASA), the PICA and the vertebral arteries


Spinal Cord Tracts

-specific areas of the cord where certain axons are grouped together, travelling as a “tract” of axons. -This happens in the outside parts of the cord, in the white matter. Remember, axons are myelinated = white.
3 main tracts
1. Corticospinal Tract: descending motor input aka Pyramidal Tracts
2. Dorsal Columns: ascending sensory input
3. Spinothalamic Tract: ascending sensory input



-CNS to PNS.
-Transmits motor commands from motor cortex, thru spinal cord, to ventral roots.
-80% crosses in medulla and continues down as Lateral CST to distal extremity muscles.
-20% continues down as Ventral CST to trunk and proximal extremity muscles.



-PNS to CNS. sensory
-Transmit vibrioception, proprioception and light touch from the periphery, thru the medulla’s medial lemniscus, thru the thalamus,
to sensory cortex.
-Crosses in the medulla’s lemniscal



-PNS to CNS.
-Transmits pain and temperature thru the cord,
thru the thalamus, to the sensory cortex.
-Crosses in the cord, usually one level higher than which it enters.