The Brain and Cranial Nerves
what happens in Sleep Stage 4?
(aka slow wave sleep) EEG is dominated by low frequency, high amplitude delta waves; muscles very relaxed, vital signs at lowest lvl, difficult to wake
prefrontal cortex
(frontal association area) the most rostral part of the frontal lobe, integrates information from sensory and motor regions and association areas, creates what we think of as personality
what is REM sleep?
(rapid eye movement sleep), sleep stage 2, eyes move back/forth like watching a movie, EEG resembles waking state but sleeper is hardest to rouse, vital signs increase, brain consumes more O2 than when awake, sleep paralysis especially strong
what three anterior dilations (primary vesicles) doe the neural tube exhibit by the 4th week of an embryo?
*forebrain *midbrain *hindbrain
by week five, the fore/mid/hindbrain subdivide into five secondary vesicles, what are they respectively?
*forebrain- telencephalon, diencephalon *midbrain- does not divide, retains name mesencephalon *hindbrain-metencephalon and myelencephalon
how does signal input to the cerebellum relate to the cerebellar peduncles
*most spinal input enters the cerebellum by the inferior peduncles *most input from the rest of the brain enters by middle peduncles *output travels by superior peduncles
rostral
*towards the nose *for the brain it means "towards the forehead" *in spinal cord and brainstem means "higher"
caudal
*towards the tail *for the brain it means "towards the spinal cord" *in spinal cord and brainstem means "lower"
what are the three purposes the cerebral spinal fluid serve?
1. Buoyancy 2. protection 3. chemical stability
what are the 4 types of brain waves?
1. alpha waves 2. beta waves 3. theta waves 4. delta waves
what percent of adult body weight does the brain make up?
2%
how many nuclei does the thalamus consist of and what are their five groups?
23; anterior, posterior, medial, lateral, and ventral
how many sleep stages are there?
4
what does stimulation of the gratification center of the limbic system produce?
a sense of pleasure or reward
fourth ventricle
a small triangular chamber between the pons and cerebellum, narrows caudally to form the central canal
choroid plexus
a spongy mass of blood capillaries found on the floor or wall of each ventricle
corpus callosum
a thick bundle of nerve fibers found below the longitudinal fissure that connects both hemispheres, has a distinctive C shape in sagittal sections
interventricular foramen
a tiny pore that connects each lateral ventricle to the third ventricle
epithalamus
a very small mass of tissue composed mainly of the pineal gland, the habenula, and a thin roof over the third ventricle
prosopagnosia
cannot remember familiar faces, even his/her own reflection in a mirror
how is the hypothalamus involved in emotional behavior/sexual response?
centers are involved in a variety of emotional responses including anger, aggression, fear, pleasure, and contentment; sexual drive, copulation and orgasm
what is contained in the midbrain?
cerebral aqueduct, continuations of the medial lemniscus and reticular formation, and the motor nuclei of two cranial nerves that control eye movement
neural integration is carried out in the gray matter of the cerebrum, which is found in what three places?
cerebral cortex basal nuclei limbic system
which parts of the brain control the sleep cycle?
cerebral cortex, thalamus, hypothalamus, and reticular formation
what are the three major portions of the brain?
cerebrum cerebellum brainstem
what are fundamental motor functions the neural network of the medulla are involved in?
chewing, salivation, swallowing, gagging, vomiting, respiration, speech, coughing, sneezing, sweating, cardiovascular and gastrointestinal control, head/neck/should movment
what are the components of the limbic system?
cingulate gyrus hippocampus amygdala
Cerebrospinal fluid
clear, colorless liquid that fills the ventricles and canals of the CNS and bathes its external surface
association tracts
connect different regions within the same cerebral hemispheres; link perceptual and memory centers of the brain
blood-brain barrier (BBB)
consists of tight junctions between the endothelial cells (astrocytes and capillaries) that form the capillary walls; ensures that anything leaving the blood must pass through the cells not between them
gracil and cunate fasciculi
continue as two pairs of ridges found posteriorly on the medulla
what are the four bulges of the tectum
corpora quadrigemina superior colliculi -upper pair inferior colliculi- lower pair
commissural tracts
cross from on cerebral hemisphere to the other through bridges called commissures; great majority pass through the large corpus callosum; enable two sides of cerebrum to communicate with each other
what are the two potential points of entry that must be guarded by the brain barrier system?
blood capillaries throughout the brain tissue and capillaries of the choroid plexus
how is CSF produced?
blood plasma is filtered through the capillaries of the brain; ependymal cells modify the filtrate as it passes through them
orexins
brain neuropeptides; act as "sleep switch"; produced by lateral and posterior hypothalamus, strongly stimulate wakefulness and elevated metabolic rate
what do EEG's monitor?
brain waves
cerebral crus
bundle of nerve fibers that connect the cerebrum to the pons and carry the corticospinal nerve tracts
frontal lobe lesions
produce profound personality disorders and socially inappropriate behaviors
Ependyma
produces the CSF; a type of neuroglia that resembles cuboidal epithelium lines the ventricles and canals and covers the choroid plexuses
what are the three kinds of tracts (bundles) of the cerebral white matter?
projection tracts commissural tracts association tracts
olive
prominent bulge found lateral to each pyramid
arachnoid granulations
reabsorb CSF; extensions of the arachnoid menix shaped like little sprigs of cauliflower, protrudes through dura mater into superior sagittal sinus
what percent of blood, oxygen, and glucose does the brain receive/consume?
receives 15% of blood; consumes 20% of O2 and glucose
what to the inferior colliculi do?
receives signals from the inner ear/relays them to other parts of the brain; mediate reflexive head turning to sound; and the tendency to jump at sudden noises
vasomotor center
regulates blood pressure and flow by dilating and constricting blood vessels
how is the hypothalamus involved in food and water intake?
regulates sensations of hunger and satiety.
cardiac center
regulates the rate and force of the heart beat
describe the sleep and consciousness of the reticular formation in the midbrain
reticular formation has projections to the thalamus and cerebral cortex that allow some control over what sensory signals reach the cerebrum and come to our attention
medial lemniscus
ribbon like section formed when the gracile/cuneate nucli synapse with second order fibers that decussate
what are the two directional terms used to describe the CNS anatomy?
rostral and caudal
transverse sinus
runs horizontally from the rear of the head toward each ear.
what does the prefrontal cortex have to do with emotion?
seat of judgment, intent, and control over expression of our emotions; allows us to decide appropriate ways to show our feelings
gray matter (brain)
seat of the neurosomas, dendrites, and synapses; forms a surface layer called the cortex over the cerebrum and cerebellum
how is the hypothalamus involved in hormone secretion?
secrets hormones that control the anterior pituitary gland regulating growth, metabolism, reproduction, and stress response
transverse cerebral fissure
separates the cerebrum from the cerebellum
anterior median fissure
separates the pyramids of the medulla
How are Purkinje cells arranged?
single file with the thick dendritic planes parallel to each other like books on a shelf
circadian rythms
sleep cycles; marked by events that reoccur at intervals of ~24hrs
folia
slender, transverse parallel folds in the cerebral hemispheres; separated by shallow sulci
insula
small mass of cortex deep to the lateral sulcus, visible only by cutting away some of the overlying cerebrum
what substances is the Brain Barrier System (BBS) slightly permeable to?
sodium, potassium, chloride and waste products urea and creatinine
what are the functions of the networks formed by the reticular formation?
somatic motor control cardiovascular control pain modulation sleep and consciousness habituation
dural sinuses
spaces that collect blood that has circulated through the brain
brain barrier system
strictly regulates what can get from the bloodstream into the tissue fluid of the brain
what are the two major superficial dural sinuses?
superior sagittal sinus and transverse sinus
cortex
surface layer of gray matter over the cerebrum and cerebellum
what are the 3 components of the cerebral peduncles
tegmentum substantia nigra cerebral crus
agnosia
temporal lobe lesion; the inability to recognize, identify, and name familiar objects
what three structures arise from the embryonic diencephalon?
thalamus, hypothalamus, and epithelamus
how is the hypothalamus involved in sleep and circadian rhythms?
the caudal part of the hypothalamus is part of the reticular formation; contains the nuclei that regulate the rhythm of sleep and waking
the first four lobes of the cerebrum are visible, what are they named for?
the cranial bones overlying them
what are the two divisions of the forebrain
the diencephalon and telencephalon
how is the hypothalamus involved in thermoregulation?
the hypothalamic thermostat consists of a collection of neurons, concentrated especially in the preoptic nucleus, that monitor body temperature. when temp deviates too much, the center activates mechanisms to lower/raise body temp
lateral ventricles
the largest and most rostral of the ventricles; form an arc in each cerebral hemisphere
cerebellum
the largest part of the hindbrain and second largest part of the brain as a whole; contains 50% of neurons; right and left cerebral hemispheres
how is the hypothalamus involved in memory?
the mammillary nuclei lie in the pathway of signals traveling from the hippocampus (an important memory center of the brain) to the thalamus
Purkinje cells
the most distinctive cells in the cerebellum; unsually large globose cells that have a tremendous profusion of dendrites compressed into a single plane like a flat tree
what condition arises from the degeneration of neurons in the substantia nigra:
the muscle tremors of Parkinson disease
what does the nervous system develop from and what is it?
ectoderm; the ourter most tissue layer of an embryo
central (periaqueductal) gray matter
encircles the cerebral aqueduct; is involved with the reticulospinal tracts in controlling awareness of pain
diencephalon
encloses the third ventricle and is the most rostral part of the brainstem
projections tracts
extend vertically between higher and lower brain and spinal cord centers and carry information between the cerebrum and the rest of the body
central canal
extends through the medulla oblongata into the spinal cord
Certain unusually prominent sulci divide each hemisphere into how many anatomically/functionally distinct lobes of cerebrum, what are their names?
five; frontal lobe, parietal lobe, occipital lobe, temporal lobe, insula
neural tube
following closure, separates from ectoderm, sinks deeper, grows lateral processes that form motor nerve fibers; lumen becomes central canal of spinal cord and ventricles of brain
what are the three descriptions of mature brain anatomy?
forebrain, midbrain, and hindbrain
hypothalamus
forms the floor and part of the walls of the third ventricle; is the major control center of the endocrine and autonomic nervous system; plays essential role in homeostatic regulations of nearly all organs of the body
neural plate
forms within the first 3 weeks along the dorsal midline of an embryo and sinks into the tissue creating a neural groove
suprachiasmatic nucleus
found in the hypothalamus, controls our 24hr (circadian) rhythm of activity
pyramids
found in the medulla, resemble side-by-side baseball bats, wider at rostral end; separated by the groove anterior median fissure
superior sagittal sinus
found just under the cranium along the median line
deep nuclei
four masses of gray matter in each hemisphere of the cerebellum
what does the superior colliculi do?
functions in visual attention, visually tracking moving objects, reflexes like blinking, focusing, pupillary dilation/constriction, response to visual stimulus
neural crest
gives rise to the two inner meninges (arachnoid/pia mater) and many structures of the nervous system
what are the two components of the brain?
gray and white matter
what are fundamental sensory functions the neural network of the medulla are involved in?
hearing, equilibrium, touch, pressure, temperature, tasts, and pain
sleep spindles
high spikes resulting from interactions between neurons of the thalamus and cerebral cortex
antidiuretic hormone
hormone produced by the hypothalamus that conserves water by reducing urine output; stimulated by dehydration
The nuclei of the hypothalamus include centers concerned with what visceral functions?
hormone secretion autonomic effects thermoregulation food and water intake sleep and circadian rhythms memory emotional behavior/sexual response
osmoreceptors
hypothalamic neurons that monitor osmolarity and stimulate water-seeking and drinking behavior when the body is dehydrated
how is the hypothalamus involved in autonomic effects?
hypothalamus is a major integrating center for the ANS; sends descending fibers to lower brainstem nuclei that influence heart rate, blood pressure, GI secretion and motility, and pupillary diameter
delta waves
in awake infants, adults in deep sleep; predominance in awake adults indicates serious brain damage
short association fibers
in the association tract, connect different gyri within a single lobe
long association fibers
in the association tract, connect different lobes of a hemisphere to each other
circumventricular organs
in the third and fourth ventricles where the barrier is brain barrier is absent and the blood has direct access to the brains neurons
what is special about pyramidal cells
include output neurons, the only cerebral neurons whos fibers leave the cortex and connect with other parts of the CNS
describe the cardiovascular control of the reticular formation in the midbrain
includes the cardiac and vasomotor centers of the medulla oblongata
sleep paralysis
inhibition of muscular activity
where does the input and output to the cerebellum process?
input to the cerebellum goes to the cortex, all of its output comes from the deep nuclei
what can be the result of injury to the reticular formation?
irreversible coma
cerebrum
is about 83% of the brains volume and consists of a pair of half globes called the cerebral hemispheres
what is important to note about the diencephalon of an embryo?
it exhibits a pair of small cuplike optic vesicles that become the retinas of the eyes
what is important to note about the telencephalon of an embryo?
it has a pair of lateral outgrowths that later become the cerebral hemispheres
what is the general chemical make up of CSF?
it has more sodium and chloride, but less potassium, calcium, and glucose, and has very little protein compared to blood plasma
how can the Brain Barrier System be a hindrance?
it is an obstacle to the delivery of medications such as antibiotics and cancer drugs, complicating treatment of brain diseases
the hypothalamus produces two hormones that are stored in the posterior pituitary gland, what are they involved with?
labor contractions, lactation, and water conservation
white matter (brain)
lies deep to the gray matter in most of the brain; tracts of the spinal cord connect parts of the brain as well as the spinal cord
frontal lobe
lies immediately beind the frontal bone, extends to the central sulcus; is chiefly concerned with voluntary motor functions, motivation, foresight, planning, memory, mood, emotion, social judgement, and aggression
parietal lobe
lies under the parietal bone, starts at central sulcus-extends to the parieto-occipital sulcus; is the primary site for receiving and interpreting signals of general senses, for taste, and some visual processing
special senses
limited to the head and some employ relatively complex sense organs; vision, hearing, equilibrium, taste, and smell
basal nuclei
masses of cerebral gray matter buried deep in the white matter, lateral to the thalamus; often called basal ganglia
what is the connective tissue that envelopes the brain and lies between nervous tissue and bone?
meninges
what happens in Sleep Stage 3?
moderate to deep sleep, beginning ~20min in, sleep spindles occur less often, t/d waves appear, muscles relax vital signs fall
what does the reticular formation consist of?
more than 100 small neural networks defined less by anatomical boundaries than by their use of different neurotransmitters
pyramidal cells
neuron found in the cerebral cortex; tall and conical, apex points to brain surface and has thick dendrite with many branches, base give rise to horizontally oriented dendrites and axon that pass into white matter
stellate cells
neurons found in the cerebral cortex; have spheroidal somas with dendrites projection in all directions for short distances; concerned with receiving sensory input and processing information on local levels
Is the limbic system found in only one location in the brain?
no, all of the structures of the limbic system are bilaterally paired, there is a limbic system in each cerebral hemisphere
is there a brain-CSF barrier?
no, because it is important to allow exchanges between the brain tissue and CSF
theta waves
normal in children, drowsy/sleeping adults; predominance in awake adults suggests emotional stress or brain disorder
beta waves
occur in the frontal/parietal region; accuentuated during mental activity and sensory stimulation
alpha waves
occur in the parietooccipital area; present when a person is awake and resting, suppressed during specific sensory stimulation, and absent during sleep
suprachiasmatic nucleus
one control center for sleep; does not induce sleep/waking but regulates the time of day one sleeps; some nerve fibers of the eye go here instead of visual cortex
narcolepsy
one experiences excessive daytime sleepiness and fatigue and may often fall asleep at work or school with abnormally quick onset of REM sleep, orexins are blocked
what happens in Sleep Stage 1?
one feels drowsy, eyes close, begins to releax, thoughts come/go, drifting sensation, awakens easily if stimulated; EEG is dominated by alpha waves
retrograde amnesia
one is unable to recall things they knew before brain injury
anterograde amnesia
one is unable to store new information due to brain injury
arcuate nucleus
one nucleus in the hypothalamus that contains receptors for hormones that increase/reduce hunger/energy expenditure, exert long term control over body mass
what happens in Sleep Stage 2?
one passes into light sleep; EEG declines in frequency but increases in amplitude, exhibits 1-2sec. sleep spindles
describe the pain modulation of the reticular formation in the midbrain
one route by which pain signals from the lower body reach the cerebral cortex; is the origin of descending analgesic pathways
memory function of hippocampus
organizes sensory and cognitive experiences into a unified long-term memory, learns from sensory input while experience is happening, but has short memory
contralateral neglect syndrome
parietal lobe lesion can cause person to become unaware of objects or even their own limbs on the other side of the body
memory function of amygdala
plays role in emotional memory
memory function of cerebellum
plays role in learning motor skills
midbrain
developed from the mesencephalon of the embryo; a short segment of brainstem that connects the hindbrain and forebrain
pons
developed from the metencephalon of an embryo; broad anterior bulge rostral to the medulla
telencephalon
develops chiefly into the cerebrum
what are the major components of the brain stem from rostral to caudal?
diencephalon midbrain pons medulla oblongata
tegmentum
dominated by the red nucleus-connections go mainly to and from the cerebellum collaborating in fine motor control
cerebellar peduncles
two pairs of thick stalks on the posterior of the pons; connect the cerebellum to the pons and midbrain; carry signals to and from the cerebellum
cerebral peduncles
two stalks of the anterior midbrain that anchor the cerebrum to the brain stem; each has 3 main components
respiratory centers
two; regulate the rhythm and depth of breathing
what is one of the special functions of the descending analgesic pathways?
under certain circumstances, the nerve fibers in these pathways act in the spinal cord to deaden ones awareness of pain
temporal lobe
under the temporal bone, separated by the parietal lobe by a deep lateral sulcus; concerned with hearing, smelling, learning, memory, and aspects of vision/emotion
what does stimulation of the aversion center of the limbic system produce?
unpleasant sensations such as fear or sorrow
what is the name for the four internal chambers of the brain?
ventricles
what substances is the Brain Barrier System (BBS) highly permeable to?
water, glucose, lipid soluble substance like O2, CO2, alcohol, caffeine, nicotine and anesthetics
arbor vitae
when white matter exhibits a branching, fernlike pattern in the sagittal section of the cerebellum
what composes most of the volume of the cerebrum?
white matter, composed of glia and myuelinated nerve fibers
where is cerebrospinal fluid formed?
~40% is formed in the subarachnoid space; ~30% by the lining of the brain ventricles; 30% by the choroid plexuses
what is special about pyramidal cells axons?
they have collaterals that synapse with other neurons in the cortex or in deeper regions of the brain
what is one of the functions of the limbic system
they play significant roles in emotion and memory, most structures have centers for both gratification and aversion
gyri
thick folds found in the cerebral hemispheres, they are separated by shallow grooves called sulci; allows for greater amount of cortex to fit in the cranial cavity
blood-CSF barrier
at the choroid plexuses; formed by tight junctions between ependymal cells
occipital lobe
at the rear of the head, caudal to parieto-occipital sulcus and underlying the occipital bone; principal visual center of the brain
amnesia
defects in declarative memory (ability to describe past events), not procedural memory (ability to tie your shoes)
how many agreed upon brain centers are classified as basal nuclei and what are they?
three; caudate nucleus, putamen, globus pallidus; collectively called the corpus striatum for their striped appearance
what effects could lesions on the cerebellum have?
deficits in coordination and locomotion; sensory, linguistic, emotional and other nonmotor functions; difficulty identifying different views of a three-dimensional objects as belonging to the same object
granule cells
tiny densely spaced cells that are the most abundant type of neuron in the entire brain
what is the primary function of the mammillary nuclei
to relay signals from the limbic system to the thalamus.
cerebral aqueduct
a canal that passes down the core of the midbrain and leads to the fourth ventricle
cerebral cortex
a layer covering the surface of the hemispheres; constitutes ~40% of the mass of the brain and contains 14-16 billion neurons
reticular formation
a loose web of gray matter that runs vertically through all levels of the brainstem;
inferior olivary nucleus
a major relay center for signals going from many levels of the brain and spinal cord to the cerebellum
third ventricle
a narrow median space inferior to the corpus callosum; receives fluid from the interventricular foramen
neural fold
a raised fold along each side of the neural groove in embryo; they roll toward each other and fuse creating the neural tube
neocortex
about 90% of the human cerebral cortex is this six layered tissue
medulla oblongata
all nerve fibers connecting the brain to the spinal cord pass through; formed from the embryos myelencephalon; begins at the foramen magnum extends rostrally to the groove between the medulla and pons
brainstem
all of the brain except the cerebrum and cerebellum
limbic system
an important center of emotion and learning; is a ring of structures on the medial side of the cerebral hemisphere, encircling the corpus callosum and thalamus
thalamus
an ovoid mass perched at the superior end of the brainstem beneath the cerebral hemispheres; each side of the brain has one; has major influence on motor control
cerebrum
developed from the embryonic telencephalon; is the seat of your sensory perception, memory, thought, judgement, and voluntary motor actions
substantia nigra
dark gray to black nucleus pigmented with melanin; motor center that relays inhibitory signals to the thalamus and basal nuclei preventing unwanted body movement
which nervous system is active during REM sleep?
the parasympathetic
hippocampus
the part of the limbic system found in the medial lobe
the amygdala
the part of the limbic system immediately rostral to the hippocampus, also in the temporal lobe
cingulate gyrus
the part of the limbic system that arches over the top of the corpus callosum in the frontal and parietal lobes
tectum
the part of the midbrain posterior to the cerebral aqueduct; rooflike; exhibits four bulges
mammillary bodies
the posterior humps on the hypothalamus; each contains three to four mammillary nuclei
describe the habituation of the reticular formation in the midbrain
the process in which the brain learns to ignore repetitive, inconsequential stimuli while remaining sensitive to others.
memory consolidation
the process in which the hippocampus plays a memory repeatedly while one is sleeping so that the cerebral cortex (a slow learner) forms the longer lasting memory needed
lentiform nucleus
the putamen and globus pallidus together because they form a lens-shaped body; involved in motor control
cognition
the range of mental processes by which we acquire and use knowledge
describe the somatic motor control of the reticular formation in the midbrain
the reticulospinal tracts of the spinal cord adjust muscle tension, relays signals from the eyes and ears, enable eyes to track/fixate objects, produce rhythmic signals to muscles of breathing/swallowing
sulci
the shallow grooves separating the gyri of the cerebral hemispheres
primary sensory cortex
the sites where sensory input is first received and one becomes conscious of a stimulus, association areas are adjacent where sensory information is interpreted
cerebral hemispheres
the two half globes of the cerebrum, each is marked by thick folds called gyri
longitudinal fissure
the very deep median (midline) groove that separates the right and left hemispheres
vermis
the worm like bridge that connects the right and left cerebral hemispheres
what do circumventricular organs allow to happen
they enable the brain to monitor and respond to fluctuations in the blood glucose, pH, osmolarity and other variables
