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Brainstem and Cerebellum
Terms in this set (31)
(midbrain) is the superior structure
(part of Metencephalon) is the middle structure
(Myelencephalon) is the most inferior part of the structure
1. relay center for nervous input and is responsible for many basic motor and reflex actions.
2. bidirectional passageway for all fiber tracts between the cerebrum and the spinal cord.
develops from the metencephalon and coordinates higher motor and sensory functions.
MEDULLA OBLOGANTA: Three groups of nuclei
A. Pyramids: are two longitudinal ridges on the anterior (ventral) side.
1. They house the motor tracts of the corticospinal tracts.
2. At its most inferior end the axons cross (or decussate) which allow the brain to then control movement of the opposite side.
e.g. the right brain controls motions of the left side of the body.
B. Autonomic Nervous System Centers:
1. Cardiac Center: that regulates heart rate and strength of contraction.
2. Vasomotor Center: controls blood pressure.
Constriction raises blood pressure while relaxation lowers blood pressure.
3. Respiratory Center: regulates breathing rate
4. Other centers: control coughing, sneezing, salivation, swallowing, gagging, and vomiting.
Sensory and Motor nuclei of the Cranial Nerves
Cranial Nerve VIII (Vestibular Cochlear) sends sensory information
Cranial Nerves IX, X, XI, XII provide motor information to muscles of neck, back and pharynx, visceral organs thoracic and peritoneal cavities.
Composed of groups of axons (nerve fiber tracts)
with both motor and sensory abilities that connect the spinal cord and brain.
help control rate and depth of breathing by the autonomic respiratory centers
1. pneumotaxic center: a neural center in the upper part of the pons that provides inhibitory impulses on inspiration--prevents over filling of the lungs
maintains alternately recurrent inspiration and expiration
2. apneustic center: controls the intensity of breathing
Upper Part of Fourth Ventricle
continuous with cerebral aqueduct
(4) - divided into: 2 pairs of sensory nuclei.
Function: Relay stations in the processing pathway of visual and auditory sensations.
(2) visual reflex centers.
Function: visually track moving objects and control reflexes
e.g. such as turning the eyes and head in response to a visual stimulus.
e.g. when you think something is running towards you and you quickly turn towards the motion.
(2) auditory reflex centers.
Function: Control the reflexive turning of the head and eyes in direction of sound.
e.g. when you hear a loud noise and you turn toward the noise.
groups of axons (nerve fiber tracts) on anterior side of mesencephalon
Function: conduct impulses between cerebrum and brainstem.
Mesencephalic (cerebral) Aqueduct
connects 4th ventricle to 3rd ventricle
Right and left hemispheres with folds of cerebellar cortex called folia.
separates anterior and posterior lobe.
connects the hemispheres at the midline
Partitions of Cerebellum
1. outer gray matter
2. Arbor Vitae (white matter)
3. Cerebellar nuclei (gray matter)
Composed of groups of axons (nerve fiber tracts) that connect the cerebellum with the brainstem.
1. Inferior Cerebellar Peduncles: connect medulla oblongata to cerebellum
2. Middle Cerebellar Peduncles: connect pons to cerebellum
3. Superior Cerebellar Peduncles: connect mesencephalon (midbrain) to cerebellum
1. fine tunes skeletal movements (coordination).
2. stores the memories of previously learned movements.
3. adjusts skeletal muscle activity to maintain equilibrium and posture.
4. receives proprioceptive (sensory) information from the muscles and joints (balance)
5. kinesthetic sense (knowing body positions).
Areolar Connective Tissue that tightly adheres to the brain
composed of delicate collagen and elastic fibers. CSF
circulates in the subarachnoid space.
the outer most layer of tissue is composed of two layers.
1. Outer Periosteal Layer: Tough dense irregular connective tissue, superficial and forms the periosteum of the cranial bones (inside).
2. Inner Meningeal Layer: fused to the periosteal layer except where there are dural venous sinuses. These large sinuses drain blood from the brain and transport blood to the internal jugular veins.
Arterial break of meningeal artery. Blood pools between dura and cranium bones. Untreated is certain death.
Usually a venous sinus break. Slow leakage of blood, hard to detect, can also result in death if not treated.
CSF is cerebrospinal fluid: clear, colorless liquid, circulates in the ventricles and subarachnoid space, bathes the exposed surfaces of the CNS and completely surrounds it.
1. buoyancy: brain floats in CSF. Without CSF brain would sink through the foramen magnum.
2. Protection: provides a liquid cushion to protect the neural structures from sudden movements.
3. Environmental Stability: CSF transports nutrients and chemical messengers to the brain, removes waste products. Excess CSF and waste products are eventually
transported into the venous system.
4. Produced continuously: rate of 500 ml/day.
CSF is made in ventricles
by the choroid plexus, composed of
1. layer of ependymal cells (simple cuboidal epithelia cells lining cavities in the brain and spinal cord with cilia on the apical surface) The ependymal cells secrete CSF as formed from the capillaries.
2. capillaries that lie within the pia mater with the ependymal cells surrounding them.
Together these two structures form the CSF that flows through the ventricles and into the subarachnoid space.
CSF circulation occurs through ventricular system
1. left and right lateral ventricles: found in each cerebral
2. third ventricle: space in diencephalon that connects to each lateral ventricle via an interventricular foramen
3. Mesencephalic (cerebral) aqueduct which leads to the
4. fourth ventricle: most CSF here flows into the subarachnoid space by passing through openings in the roof of the fourth ventricle.
5. excess CSF is returned to the venous bloodstream via arachnoid villi
which extend into the dural venous sinuses.
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