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)
Pineal gland secretes:
melatonin
Each fold on the cerebrum is a ______.
gyrus
A ______ is a shallow groove between gyri.
sulcus
Sulci (picture):
Fissures
deeper grooves between gyri
e.g. longitudinal fissure separating L/R hemispheres
fissures AND gyri, are formed during embryonic development when the gray matter of the cortex enlarges faster than the deeper white matter
Corpus callosum (hard body)
largest fiber bundle in the brain
communication between hemispheres (commissure)
Tracts of cerebral white matter
- Association tracts: between gyri in same hemisphere
- Commissural tracts: between the corresponding gyri in each hemisphere
- corpus callosum
- anterior commissure
- posterior commissure
- Projection tracts: between (to and from) cerebrum to lower parts of CNS (e.g. brainstem, thalamus etc.)
Basal ganglia
- help regulate initiation and termination of movements and unconscious (inconscient) contractions of skeletal muscle> muscle tone
- action selection: which of several possible behaviors to execute at a given time
- corpus striatum consists of:
- caudate nucleus
- lentiform nucleus consists of:
- globus pallidus
- putamen
- internal capsule separates caudate nucleus and thalamus
- Parkinson’s:
- melanin pigmented dopamine producing neurons of basal ganglia degenerate> affects initiation/termination of movements (tremors, stiffness, involuntary movements)
- Basal ganglia damage also found in persons with OCD, ADHD, etc.
Limbic system
- the emotional or affective (of feelings) brain; aka “emotional brain”
- primary role in range of emotions: pain, pleasure, docility (learning), affection, anger
- its cerebral structures encircle the upper part of the brain:
- hippocampus: convert new info into long term memory; functions as a “gateway” for memory formation
- damage: anterograde amnesia
- amygdala: behavioral patters such as docile behavior, rage, fear (presence/absence), aggression, restlessness
- olfactory bulbs: synapse with the olfactory receptors and mammillary bodies are olfactory relay stations
- cingulate gyrus: integral part which is involved with emotion formation and processing, learning, and memory; coordinates sensory input with emotions, regulates aggressive behavior and mediates emotional responses to pain
- fornix: carries signals from hippocampus to hypothalamus (mamillary body); arches over thalamus
- hippocampus: convert new info into long term memory; functions as a “gateway” for memory formation
Cerebral cortex:
“seat of consciousness”
contralateral (L controls R side of body) control of sensory and motor functions
lateral specialization of cortical function
Broca’s speech area vs. Wernicke’s area
- Broca’s: planning and production of speech
- damage>non-fluent aphasia: inability to properly articulate or form words; know what they want to say but cannot speak
- Wernicke’s: interprets the meaning of speech by recognizing spoken words
- damage:
- fluent aphasia: faulty understanding of spoken (word deafness) and/or written (word blindness) words; produce strings of perfectly good words that have no combined meaning (“word salad)
- damage:
- these (along with other language areas) are located in the L hemisphere in most people
Wernicke’s area:
interprets the meaning of speech by recognizing spoken words
Alzheimer disease:
- disabling senile dementia (the loss of reasoning and ability to care for oneself)
- unknown cause but appears to be a combo of genetic predisposition, environmental, lifestyle factors, and aging
- autopsy:
- loss of neurons: ones that liberate Ach; destruction of neurons of the nucleus basalis is the hallmark of the disease
- beta amyloid plaques: clusters of abnormal proteins deposited outside neurons
- neurofibrillary tangles: abnormal bundles of protein filaments inside neurons in affected brain regions
CN1 and CN2 are entirely sensory
CN8 vestibulocochlear: mostly, almost, all sensory although technically both
CN3, 4, 6, 11, 12: predominantly motor although no CN are exclusively motor throughout their entire length
3, 7, 9, 10: also have autonomic motor axons (part of the PsNS); innervate glands, smooth muscle, and cardiac muscle
CN1 Olfactory
- entirely sensory (smell)
- *olfactory bulb and olfactory tract are not CN1
- olfactory receptors are bipolar neurons
- bundles of axons of the receptors extend through the cribriform plate (ethmoid)
- these bundles are collectively the olfactory nerve
- bundles of axons of the receptors extend through the cribriform plate (ethmoid)
- anosmia: loss of sense of smell
CN2 Optic
- entirely sensory (vision)
- optic tract (after the chiasm) vs. optic nerve (before chiasm)
- myelinated axons that conduct nerve impulses for vision
- retina:
- rods and cones: light sensitive cells
- relay signals to bipolar cells which convey the impulses to ganglion cells:
- these form the optic nerve and those same axons continue on to form the optic tract
- relay signals to bipolar cells which convey the impulses to ganglion cells:
- rods and cones: light sensitive cells
CN3 Oculomotor
- controls:
- extrinsic eye muscles minus SO4 and LR6
- intrinsic eye muscles: R3; ciliary muscle (lens) and sphincter pupillae (iris)
- parasympathetic innervation to intrinsic eye muscles (ANS fibers)
- innervates levator palpebrae superioris: muscle of upper eyelid
CN4 Trochlear
- SO4
- trochlea: pulley-like loop through which the tendon of the SO muscle passes
- “down and out”: SO moves the eyeball inferiorly and laterally
CN V Trigeminal
- largest of CN
- isolated from other CN
- emerges from pons
- sensory:
- face, head, tactile sensation of anterior ⅔ tongue
- motor:
- mastication
- small motor root: supplies muscles of mastication
- sensor
- large sensory root:
- ophthalmic (V1)
- maxillary (V2)
- mandibular (V3)
- large sensory root:
CN6 Abducens
- LR6
- aka abducent
CN7 Facial
- motor:
- somatic motor axons innervate muscles of:
- facial expression
- stylohyoid, posterior belly of diagastric
- stapedius muscles
-
parasympathetic innervation (ANS fibers) to:
- lacrimal glands
- nasal glands
- saliva production: sublingual and submandibular glands
- somatic motor axons innervate muscles of:
- sensory:
- taste buds in anterior ⅔ of tongue (special sense)
- Branches:
- temporal
- zygomatic
- buccal
- mandibular
- cervical
CN8 Vestibulocochlear
- formerly known as acoustic or auditory nerve
- vestibular branch: equilibrium (balance)
- cochlear branch: hearing
CN9 Glossopharyngeal
- sensory:
- taste and tactile sensation for posterior ⅓ tongue
- baroreceptors in carotid sinus and chemoreceptors in carotid bodies
- motor:
- parasympathetic innervation to parotid gland>salivation (ANS fibers)
CN10 Vagus
- longest CN
- sensory:
- taste , touch, pain, temp., proprioception from epiglottis and pharynx
- monitoring of BP, O2, CO2
- motor:
- somatic control: swallowing, coughing, voice production
-
parasympathetic innervation (ANS Fibers):
- smooth muscle of GI, secretion of digestive fluids
- slowing of the HR
CN11 Accessory
- motor:
- voluntary muscles used in swallowing
- trapezius and sternocleidomastoid
CN12 Hypoglossal
- motor:
- tongue movement
- all intrinsic muscles of tongue
- all extrinsic muscles of tongue EXCEPT: palatoglossus
- tongue movement
Spinal cord (picture):
- continuation of medulla; extends from foramen magnum and terminates as the conus medullaris (IV disc, between L1-2)
- filum terminale: extension of pia mater that arises from the conus medullaris to anchor the spinal cord to the coccyx
- cauda equina: nerves from inferior portion of spinal cord continue as fine strands within the vertebral canal
Meninges of spinal cord:
- continuous with the meninges of the brain
- Dura mater:
- forms a sac from the level of the foramen magnum to the second sacral vertera
- epidural space: between the wall of vertebral canal and dura mater
- contains a cushion of fat and connective tissue
- Arachnoid mater:
- subdural space: between dura mater and arachnoid mater
- contains interstitial fluid
- subdural space: between dura mater and arachnoid mater
- Pia mater:
- contains blood vessels that supply spinal cord
- subarachnoid space: between arachnoid mater and pia mater
- contains CSF
Spinal cord gray matter(internal anatomy):
- Anterior horns:
- contain cell bodies of somatic motor neurons and motor nuclei that provide nerve impulses for the contraction of skeletal muscles
- Lateral horns:
- contain cell bodies of ANS motor neurons that regulate activity of smooth muscle, cardiac muscle, and glands
- only present in the thoracic, upper lumbar, and sacral segments
- T1-L2
- S2-S4
- Posterior horns:
- contain somatic and ANS sensory nuclei
- Gray commissure:
- connects gray matter of left and right sides
- Central canal: continuous with the 4th ventricle in the medulla and extends the length of the spinal cord
Spinal cord white matter (internal anatomy):
- tracts: myelinate axons of CNS
- anterior (ventral) white column
- posterior (dorsal) white column
- lateral white column
Spinal cord roots and nerves:
- dorsal root: sensory
- anterior root: motor
- spinal nerves:
- once a spinal nerve=PNS
- 31 pairs
