neuroanatomy (generally)

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NEUROANATOMY

THE BRAIN

4 major parts of the brain:Brain stemCerebellumDiencephalon (thalamus, hypothalamus, epithalamus)Cerebrum

Brain stem

Part of the brain between the spinal cord and the diencephalon.3 structures

Medulla oblongataPons Midbrain

Medulla OblongataMedullas white matter

Ascending (sensory) tractsDescending (motor) tracts

Pyramids formed by the large lateral corticospinal tracts that pass from cerebrum to the spinal cord.

90% axons in the left pyramids cross to the right side, vice versa.

To control voluntarymovements of the limb &trunk.

Decussation of pyramids

Nuclei in medulla

Lateral to the pyramid is olive.

Inferior olivary nucleus. Function: receives input from cerebral cortex, red nucleus of midbrain & SC. Extend axons into cerebellum provides instruction to cerebellum to make adjustments to the muscles activity as we learn new motor skills

Regulate cardiovascular centerRegulate respiratory center medullary rhythmicity area: adjust the basic rhythm of breathingControl reflexes for vomitting (vomitting center), swallowing (degluitition center), sneezing, coughing & hiccuping

Nuclei in posterior part of medulla that associate with the dorsal column medial lemniscus (gracile fasciculus & cuneate fasciculus):

Associate with sensations of touch, pressure, vibration & conscious proprioception Sensory nuclei in the medulla

Gracile nucleusCuneate nucleus

Gustatory nucleus (taste)Cochlear nuclei (hearing)Vestibular nuclei (balance)

PonsLinks different part of the brainServes as a relay station from medulla to higher cortical structures of the brain.Respiratory center + medulla rhythmicity area = control breathing

MidbrainConnects hindbrain & forebrainCerebral peduncle contains paired bundles of axons : axons of corticospinal, corticobulbar & corticopontine tracts conducts nerve impulses from motor areas in cerebral cortex to the SC, medulla & pons.Nerve pathway of the cerebral hemispheres & contains auditory & visual reflex centersControl responses to sight, eye movement, pupil dilation, body movement & hearing

Posterior part (tectum)

Superior colliculiReflex centers for certain visual activitiesInferior colliculiPart of auditory pathway, relaying impulses from the receptors for hearing in the inner ear to the brain

Nuclei of the midbrainNeurons that extend from here release dopamine help control subconcious muscles activitiesRich blood supply & iron-containing pigment in neuronal cell bodies.

Neurons (axons) from cerebellum & cerebral cortex form synapses in red nuclei help control muscular movements

What a physiotherapist should know?

1. There are4 structuresin the midline beginning withM2. There are4 structuresto the side (lateral) beginning withS3. There are4 cranial nervesin themedulla,4in theponsand4above the pons(2 in the midbrain)4. The4 motor nucleithat are in themidlineare those thatdivide equally into 12 except for 1 and 2, that is3, 4, 6 and 12 (5, 7, 9 and 11 are in the lateral brainstem)(the Brainstem rule of 4. Doctor Peter Gates)

Medial StructuresDeficits Motor pathway(or corticospinaltract): contralateral weakness of the arm and legMedial Lemniscuscontralateral loss of vibration and proprioception in the arm and legMedial longitudinal fasciculusipsilateral inter-nuclear ophthalmoplegia (failure of adduction of the ipsilateral eye towards the nose and nystagmus in the opposite eye as it looks laterally)Motor nucleus and nerveipsilateral loss of the cranial nerve that is affected (3, 4, 6 or 12)

Lateral structures Deficits Spinocerebellar pathwayipsilateral ataxia of the arm and leg

Spinothalamic pathway contralateral alteration of pain and temperature affecting the arm, leg and rarely the trunk

Sensory nucleus of the 5th cranial nerveipsilateral alteration of pain and temperature on the face in the distribution of the 5th cranial nerve (this nucleus is a long vertical structure thatextendsin the lateral aspect of the pons down into the medulla)

Sympathetic pathwayipsilateral Homers syndrome, that is partial ptosis and a small pupil (miosis)

CN in MedullaDeficits Glossopharyngeal (CN9)ipsilateral loss of pharyngeal sensationVagus (CN10)ipsilateral palatal weaknessSpinal accessory (CN11)ipsilateral weakness of the trapezius and stemocleidomastoid musclesHypoglossal (CN12)ipsilateral weakness of the tongue

CN in PonsDeficits Trigeminal (CN5)ipsilateral alteration of pain, temperature andlight touchon the face back as far as the anterior two-thirds of the scalp and sparing the angle of the jaw.Abducent (CN6)ipsilateral weakness of abduction (lateral movement) of the eye (lateral rectus)Facial (CN7)ipsilateral facial weaknessAuditory (CN8)ipsilateral deafness.The 6th cranial nerve is the motor nerve in the medial pons

CN above PonsDeficits Oculomotor (CN3)impaired adduction, supradduction and infradduction of the ipsilateral eye with or without a dilated pupil. The eye is turned out and slightly downTrochlear (CN4): eye unable to look down when the eye is looking in towards the nose (superior oblique).The 3rd and 4th cranial nerves are the motor nerves in the midbrain

(b) Cerebellum

primarily contains efferent fibers from the cerebellar nuclei, as well as some afferents from the spinocerebellar tract.primarily contains afferents from the pontine nuclei (from motor areas of the cerebral cortex) into cerebellumprimarily contains afferent fibers from the medulla, as well as efferents to the vestibular nuclei

Divisions of the Cerebellum

Functional subdivisions of cerebellumCerebrocerebellum consist of lateral hemisphere& the dentate nuclei.

its extensive connections with the cerebral cortex, via the pontine nuclei (afferents) and the VL thalamus (efferents).

Functions:Planning & timing of movementInvolved in cognitive function of cerebellum

Functional subdivisions of cerebellumVestibulocerebellum consist of theflocculonodular lobeand its connections with thelateral vestibular nuclei,

Functions:Vestibular reflexesPostural maintenance

Functional subdivisions of cerebellumSpinocerebellum Consist of thevermisand theintermediate zones, as well as the fastigialand interposednuclei.

it receives major inputs from the spinocerebellar tract.

Its output projects to rubrospinal, vestibulospinal, and reticulospinal tracts.

involved in the integration of sensory input with motor commands to produce adaptive motor coordination.

What happened when there is damage to the cerebellum?Decomposition of movementIntention tremorDysdiadochokinesia Deficits in motor learning

(c ) Diencephalon (thalamus, epithalamus & hypothalamus)

Extends from the brainstem to the cerebrum & surrounds 3rd ventricle: thalamus, hypothalamus & epithalamusSurrounded by cerebral hemisphere.Contains numerous nuclei involved in wide variety of sensory & motor processing between higher & lower brain.

Thalamus

The intermediate mass (interthalamic adhesion) : a bridge of gray matterThe internal medullary lamina: a vertical Y-shaped sheet of white matterFunctions: to divide right side & left side of thalamus gray matterInternal capsule: pathway for axons connect the thalamus & cerebral cortex.Functions of thalamus:Major relay station for most sensory impulses that reach primary sensory areas of the cerebral cortex from SC & brain stem.Motor function (transmit information from the cerebellum & basal nuclei to the primary motor area of the cerebral cortex)Relays nerve impulses between different areas of the cerebrum & plays a role in maintenance of consciousness.

Receives input: the hypothalamusSends output: the limbic systemFunctions: emotions & memoryReceive input: the limbic system& basal nucleiSend output: cerebral cortexFunctions: emotions, learning, memory & cognitionLateral group nucleiReceives input: the limbic system, superior colliculi & cerebral cortexSends output: the cerebral cortex.Functions: expressions of emotionsFunctions: Help integrate sensory informationReceives input: the basal nucleiSends output: motor areas of cerebral cortexFunctions: plays a role in movement controlReceives input:the cerebellum & the basal nucleiSends output: motor areas of cerebral cortexFunctions: plays a role in movement controlRelays impulses for somatic sensations: touch, pressure, vibartion, itch, tickle, temperature,pain & proprioception from face & body to the cerebral cortex.Relays impulses for sight from retina to the primary visual area of the cerebral cortex.Relays auditory impulses for hearing from the ear to the primary auditory area of cerebral cortex

Intralaminar nuclei (within the internal medullary lamina)Connects with the reticular formation, cerebellum, basal nuclei & wide areas of the cerebral cortex.Function: - Arousal (activation of the cerebral cortex from the brain stem reticular formation)- Integration of sensory & motor informationMidline nucleus a thin band adjacent to the 3rd ventricleFunctions: memory & olfactionReticular nucleus lateral aspect of the thalamusFunctions: monitors, filters & integrate activities of other thalamic nuclei.

Body temperatureWater balance/stressShivering GI tractsatietyFeeding Body clockWater balanceBlood pressureHypothalamus

Important functions of the hypothalamus:Control of the ANSProduction of hormonesRegulation of emotional & behavioral patternsRegulation of eating & drinkingControl of body temperatureRegulation circadian rhythms& states of consciouness

Epithalamus The pineal glandPart of endocrine system secretes hormone melatoninMore melatonin liberated during darkness promote sleepinessIf taken orally melatonin contribute to the bodys clock setting by inducing sleep & helping the body to adjust jet lagThe Habenular nucleiInvolved in olfaction (emotional responses to odors)

(d) Cerebrum

Primarily of myelinated axons in 3 types of tracts:Association tracts conduct nerve impulses between gyri in the hemisphere.(b) Commisural tracts (corpus callosum, anterior commissure & posterior commisure) conduct nerve impulses from gyri one cerebral hemisphere to corresponding gyri in otherCerebral hemisphere.(c ) Projection tracts conducts nerve impulsesfrom cerebrum to lower part of CNS (thalamus,brainstem /SC) of from lower parta of the CNSTo the cerebrum.

Also known as cerebral cortex.Gyri : foldsFissures: the deepest groovesSulci: the shallower grooves between foldsLongitudinal Fissue: prominent fissures that divide brain into cerebral hemisphere

Basal Nuclei / Basal Ganglia receive input from cerebral cortexProvide output to motor parts of the cortex via the medial & ventral group nuclei of thalamusMajor function: To help regulate initiation and termination of movementGlobus pallidus: helps regulate muscle tone required for specific body movementsControl subconscious contraction of skeletal musclesInitiate and terminate cognitive processes (attention, memory, planning & act with limbic system to regulate emotional behaviors

The Limbic Systememotional brainFunctions:Promotes range of emotions, including pleasure, pain, docility, affection, fear & anger.Works together with cerebrum for memory functions damage to the limbic system cause memory impairment

Primary Motor AreaVoluntary contractions of specificBrocas speech areaSpeaking & understanding languageCVA can still have clear thoughts but unable to form words.Premotor areaStorage of motor patternFrontal eye field areaScanning movements of the eyesPrefrontal cortexConcentration, elaboration of thought, judgement, inhibition, personality, emotional traits.Bilateral damage of the area rude, inconsiderate, incapable of accepting advice, moody, inattentive, less creative.

The primary auditory area auditory perception & receives information for soundPrimary Olfactory areaReceives impulse for smell & olfactory perceptionFacial recognition areaStores information about faces & allow to recognize people by their facesWernickess areaTranslate words into thoughtCVA-able to speak but cannot arrange words in coherent fashion.

Primary Visual AreaReceives visual information & visual perception

Visual Association AreaAllow to recognize & evaluating what is seen

Primary somatosensory area receives nerve impulses for touch, pressure, vibration, itch, tickle, temperature, pain, proprioception.

Primary gustatory areaGustatory perception & taste discrimination

Somatosensory association determine exact shape & texture of an object by feeling itTo determine the orientation of the objectTo sense the relationship of one body part to anotherEnable to compare current sensation with previous experiences