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BRAINSTEM

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farah bella

on 5 November 2014

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Transcript of BRAINSTEM

B
R
A
I
N
S
T
E
M

PONS
Medulla Oblongata
MIDBRAIN
Located between medulla(caudally) and midbrain(rostrally)
The cortocospinal tract are more diffuse in the pons
The medial lemnicus is still situated at midline
The spinothalamic tract and the descending hypothalamic fibers continue to course together in lateral pons
Lateral lemnicus carry the bulk of ascending auditory fiber from both cochlear nuclei to inferior colliculi in midbrain
Vascular supplies
BASILAR ARTERY
Paramedian branches to median pontine region
Short circumferential branches supply anterolateral pons
Long circumferential branches run laterally over the surfaces of the pons to the anastomose
Anterior inferior cerebellar artery (AICA) first branches of basillar artery that supply inferior pons
Superior cerebellar artery (SCA) supplies cerebral cortex, white matter, and central nuclei
Medial Pontine Syndrome
contralateral hemiplegia of arms and

leg
contralateral loss
ipsilateral rectus muscle paralysis
paralysis of conjugate gaze
corticospinal fiber in basilar pons
medial lemniscus
abducens nerves fiber
pontine gaze center
Lateral Pontine Syndrome
Ataxia
Deafness
Contralateral loss of pain and temperature sense from body
Ipsilateral paralysis of facial ms. and masticatory ms.
cerebral peduncles
vestibular and cochlear nuclei and nerves
anterolateral system
facial and trigeminal motor nuclei
Medulla Oblongata
-Superior to the spinal cord, inferior part of the brain stem.
-Medulla's white matter contains all sensory(ascending)tract and motor(descending) tract that extend between spinal cord and other part of the brain.
- Receives its blood supply from several arteries, including the anterior spinal artery, posterior inferior cerebellar artery, and the vertebral artery's direct branches.
Cuneate
fasciculus
Gracile
fasciculus
Peduncle:Contain fibre. nerve impulse conduct between the superior part& inferior of the brain&spinal cord.
-Ascending sensory axons of the garcile and cuneate fasciculus are two tract in dorsal columns of the spinal cord.
-Relay sensory information to the thalamus on the opposite site of the brain.
-Dorsal column tracts synapse in their associated nuclei cross over in medulla then enter the medial leminiscus(midbrain)
thalamus.
Pyramids: Formed by the large corticospinal tracts that passes the cerebrum to the spinal cord. It control voluntary movement of the limbs and trunk.

Decussation of pyramids: Explains why each side of the brain control voluntary movement on the opposite side of the brain.

Inferior olivary nucleus: Provide instructions that the cerebellum uses to make adjustment to muscle activity.
Inferior Medulla.
-Anterolateral to the nucleus cuneatus.
-Convey pain and temperature information to the face.
Medial longitudinal fasciculus
-near the center of inferior medulla
-Coordinates eye and head movements via connections between the vestibular nuclei, spinal accessory nucleus and the nuclei that control eye movement.
Inferior Medulla
Receives visceral and taste afferent information.
Receives auditory and vestibular information via cranial nerve 8
-Sends ascending impulse through the brain stem and to higher function.
-controls autonomic functions, relay of nerve signals and body movement coordination.
-Cardiovascular center: Regulate rate&force of heartbeat and the diameter of blood vessels.
-Respiratory center(medullary rhythimicity area):
Adjust basic rhythm of breathing.
-Nuclei in the medulla also control reflexes for vomitting,swallowing,sneezing,coughing and hicupping.
-Contains components of sensory pathways for gustation(taste), audition(hearing), and equilibrium(balance)

Functions
5 pairs of cranial nerves:

1.Vestibulocochlear(VIII) nerves
2.Glossopharyngeal(IX) nerves
3.Vagus(X) nerves
4.Accessory(XI) nerves
5.Hypoglossal(X11)nerves
Clinical Conditions:
-Damaged to the medullary rhythimicity area can rapidly lead to death.
-Alcohol overdose can suppresses the medullary rhythmicity are,cause death.
-Cranial nerve malfunctions:
i)paralysis and loss of sensation on the opposite site of the body.
ii)Irregular breathing and heartbeat.
MESENCEPHALON
located between the diencephalon(thalamus and hypothalamus) and brain stem.
it can be found ventral to the cerebral cortex
short portion of the upper brain stem and connects higher brain centres with the lower centres and the spinal cord.

the cerebral aqueduct joint the third and forth ventricles.(small canal through the midbrain).
REGIONS OF MIDBRAIN

BASIS PEDUNCULI
MIDBRAIN TEGMENTUM
MIDBRAIN TECTUM
anteriorly, it formed by the cerebral peduncles and adjacent nucleus, the substantia nigra.
the substantia nigra is one of the nuclei in the basal ganglia circuit.
middle region of the midbrain
cantains verticle sensory tracts, superior cerebellar peduncle, red nucleus, pedunculopontine nucleus,and the nuclei of cranial nerves III and IV.
posterior region of the midbrain
contain the pretectal area and the colliculi
involved in pupillary, consensual, and accommodation reflexes ofe th eyes
INFERIOR COLLICULI
relay auditory information from the cochlear nuclei to the superior colliculus and to the medial geniculate body of the thalamus.
SUPERIOR COLLICULI
involve in reflexive eye (part of the visual system)and head movements
These inputs are concerned with controlling movements of the eyes.
blockage of cerebral aqueduct
Cerebral aqueduct is one of the narrowest parts of ventricular system.
In congenital hydrocephalus, or tumors of midbrain, aqueduct may be blocked which blocks the flow of CSF.
clinical condition:

Horizontal section of upper midbrain
junction of pons and midbrain
substantia nigra
These neurons project to the caudate nucleus and putamen of the basal ganglia in the forebrain
Degeneration of the pars compacta of the substantia nigra is associated with Parkinson’s disease
Other non pigmented subdivision of the substantia nigra is called the pars reticulata
Pars reticulata is considered to be a functional homologue of the medial segment of the globus pallidus which is also part of the basal ganglia.

red nucleus
sphere of the grey matter
receive information from the cerebellum and cerebral cortex and project to the cerebellum, spinal cord and reticular formation
Controls arm movement
oculomotor complex (nuclei of cranial nerve III)
anterior to the cerebral aqueduct
supplying efferent somatic fibers to the extra ocular muscle
supplying parasympathetic control of pupillary sphincher and the ciliary muscle.
nucleus of the trochlear nerve(cranial nerve IV)
inferior to the oculomotor compex
innervate the superior oblique muscle that moves the eyes
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