AP1 Exam 3 Flashcards
Major parts of the brain (picture):
Cerebrum
Diencephalon
Brainstem
Cerebellum
Layers of the meninges:
- Dura mater:
- external periosteal layer
- internal meningeal layer
- extensions separate parts of the brain:
- falx cerebri: L/R hemisphere of cerebrum
- falx cerebelli: L/R hemispheres of cerebellum
- tentorium cerebelli: separates the cerebrum from cerebellum
- Arachnoid mater:
- Pia mater
Which parts of the brain lack the BBB?
area postrema: vomiting center
hypothalamus
pituitary gland
pineal gland
BBB
lipid-soluble things gross easily (e.g. anesthetic agent, ETOH, O2, CO2)
some water-soluble substances cross the BBB by active transport (e.g. glucose)
some substances gross slowly (Cr, Urea, most ions)
CSF:
produced by choroid plexus in ventricles: networks of cap. covered by ependymal cells that form CSF from blood plasma;
ependymal cells are joined by tight junctions which prevent materials from leaking between the cells (ependymal cell selectivity>they choose what is allowed into the CSF)
reabsorbed (as fast as its produced=CSF pressure remains constant) into the blood through the arachnoid villi which project into the CSF circulatory spaces
Ventricles of the Brain
Lateral: 1st and 2nd ventricles
Third: narrow cavity surrounded by the R/L halves of thalamus
Fourth: between brain stem and cerebellum
CSF circulation and production:
produced in choroid plexuses of each ventricle; each ventricle produces CSF
lateral ventricle>third>through cerebral aqueduct>fourth>central canal of spinal cord AND subarachnoid spaces of brain and spinal cord
Hydrocephalus is a condition in which ______ builds up in the brain.
CSF
treated with a shunt: CSF drains into another part of the body (typically to the heart or peritoneal cavity)
in case of obstructive hydrocephalus, a third ventriculostomy can be performed: small hole is made in the floor of third ventricle to allow CSF to bypass the obstruction
What are the components of the brain stem?
- Midbrain
- Pons
- Medulla oblongata
*reticular formation
Medulla oblongata
- Medulla oblangata:
- aka vital brain>functions of life
- begins at the foramen magnum
- continuation of spinal cord
- pyramids: bulges of white matter contains all tracts (ascending/descending) between brain and spinal cord
- decussation: most axons in the pyramids cross to opposite side
- medullary nuclei:
- CV center
- Medullary rhythmicity area: part of resp. center>adjust rhythm of breathing
- inspiratory and expiratory area
- deglutition center: swallowing
- gustatory nucleus: taste
- cochlear nuclei: receives auditory input
- vestibular nuclei: equilibrium
- vomiting center (area postrema)
- misc.: coughing, hiccupping, sneezing
- olives: lateral to each pyramid; relays impulses to the cerebellum from cerebral cortex, red nucleus of midbrain, and spinal proprioceptors (monitor muscle and joint position)
Pons
- bridge that connects one part of the brain to another
- contains nuclei and tracts just like the medulla
- tracts:
- vertical: L/R cerebellum
- lateral: ascending/descending
- nuclei:
- relay signals for voluntary movements from their origin in cerebral cortex to the cerebellum
- pneumotaxic area: turns off the inspiratory area before the lungs become too full
- apneustic area: prolongs inhalation by sending stimulatory impulses to the inspiratory area
- tracts:
Control of respiration
- medullary rhythmicity area
- pneumotaxic area
- apneustic area
CNVIII; Vestibulocochlear nerve
has nuclei in two parts of the brain stem: pons and medulla
vestibular branch: has sensory axons that end in the vestibular nuclei in the pons
cochlear branch: has sensory axons that end in nuclei in the medulla oblongata
axons of motor neurons in both branches project from the pons to respective hair cells in the semicircular canals and spiral organ
Midbrain
- aka mesencephalon
- connects the pons to the diencephalon
- consists of nuclei and tracts (just like pons and medulla)
- nuclei:
- substantia nigra
- darkly pigmented nuclei that release dopamine
- subconscious muscle activities
- loss of neurons associated with Parkinsons
- red nuclei
- axons from cerebellum and cerebral cortex synapse with the red nuclei
- rubrospinal tract originates in the red nucleus
- function in the coordination of muscular movements
- controls crawling of babies and swinging of arms in normal walking
- substantia nigra
- nuclei:
- cerebral peduncles (anterior structures)
- contain axons of motor neurons that conduct motor neurons that conduct nerve impulses from the cerebral cortex to the spinal cord
- contain axons of sensory neurons that extend from the medulla to the thalamus
- tectum: two pairs of rounded elevations collectively calls the corpora quadrigemina
- superior colliculi: involuntary turning of head when something is detected “corner of eye”
- reflex centers for visual reflexes and visually tracking moving objects
- pupillary reflex: size of pupil
- accommodation reflex: shape of lens for close/far sight
- reflex centers for visual reflexes and visually tracking moving objects
- inferior colliculi
- superior colliculi: involuntary turning of head when something is detected “corner of eye”
- cerebral aqueduct passes through midbrain
Reticular formation
fairly extensive region of interspersed gray and white matter
small clusters of neuronal cells bodies along with small bundles of myelinated axons throughout the brainstem
main function is to regulate muscle tone
reticular activating system (RAS): sensory axons that help maintain consciousness and participate in awakening from sleep
Cerebellum
- cerebellar cortex is gray matter; also exhibits the foliar ridges
- arbor vitae forms white matter (inside)
- functions:
- cerebral peduncles (posterior structures): 3 pairs (superior, middle, inferior); conduct impulses between cerebellum and other parts of the brain
- cerebral hemispheres (two): anterior and posterior lobes; mediate unconscious refinements of skeletal muscle movements
- floculonodular lobe: equilibrium and balance
Blindfolded people with ______ cannot touch the tip of their nose with a finger because they cannot coordinate movement with their sense of where a body part is in space.
ataxia
Diencephelon components:
Thalamus (makes up majority)
Epithalamus
Hypothalamus
Pineal gland (actually part of epithalamus)
surrounds the third ventricle
Thalamus
Major relay station for sensory impulses
the two halves connected by bridge of gray matter across the third ventricle called intermediate mass
Hypothalamus
major regulator of homeostasis (controls pituitary gland)
mammillary bodies: serve as relay stations for reflexes related to the sense of smell
infundibulum (tuberal region): stalk that connects pituitary to hypothalamus
Receptors which monitor many important parameters such as temp., hormone levels, etc.
Specific functions such as control of ANS, circadian rhythm, etc.
Epithalamus
Habenular nuclei: olfaction (especially emotional responses to odors)