Lower Brain Flashcards
major parts of the brain are
Brain stem
Cerebellum
Diencephalon
Cerebrum
Continuous with the spinal cord
brain stem
Consists of:
Medulla oblongata
Pons
Midbrain
brain stem
Posterior to the brain stem
cerebellum
Superior to the brain stem
Diencephalon
Comprises mainly:
Thalamus
Hypothalamus
Diencephalon
also epithalamus & pineal gland
The cerebrum is supported on the diencephalon and ____
brain stem
largest part of the brain
cerebrum
The cranial meninges are continuous with the ____ meninges of the same name, and have the same basic structure
spinal
meninges
Dura mater (outer) Arachnoid mater (middle) Pia mater (inner)
cranial dura mater has ____ layers, whereas the spinal dura mater has only one
two
An external periosteal layer formed by the ____ covering the internal surface of the cranium
(dura mater)
periosteum
An internal meningeal layer that is ___ with the dura mater covering the spinal cord
(dura mater)
continuous
The two layers are fused together except where they separate to enclose the ____ that drain blood from the brain into the internal jugular vein
(dura mater)
dural venous sinuses
Extensions of the dura mater separate parts of the brain
Falx cerebri
Falx cerebelli
Tentorium cerebelli
separates the two hemispheres (sides) of the cerebrum
Extensions of the dura mater
Falx cerebri
separates the two hemispheres of the cerebellum
Extensions of the dura mater
Falx cerebelli
separates the cerebrum from the cerebellum
Extensions of the dura mater
Tentorium cerebelli
Neurons synthesize ATP almost exclusively from
glucose
Virtually no glucose is stored in the brain
The brain therefore requires a virtually uninterrupted flow of blood to it, and that blood must have sufficient glucose
A ____ protects brain cells from harmful substances and pathogens by preventing many such substances from entering the brain
The BBB can be broken down or disrupted by trauma, certain toxins, and inflammation
blood-brain barrier (BBB)
Lack a BBB
pineal gland
pituitary gland
hypothalamus
area postrema of fourth ventricle
The____ (of the fourth ventricle in the medulla) senses toxins in the blood, that the blood-brain barrier protects other parts of the brain from; it controls vomiting
area postrema
The BBB is formed by a combination of tight junctions of the endothelial cells of brain capillaries and ___
astrocyte foot processes
Some water-soluble substances (such as glucose) cross the BBB by ___
active transport
Other substances cross the BBB very slowly: creatinine, urea, ___
most ions
Some substances do not cross at all: proteins, most ___ drugs
antibiotic
____ substances cross easily: oxygen, CO2, alcohol, most anesthetic agents
Lipid-soluble
Protects the brain and spinal cord against chemical and physical injuries
CSF
Carries oxygen, glucose, and other needed chemicals from the blood to neurons and neuroglia
CSF
Continuously circulates through cavities in the brain and spinal cord, and around the brain and spinal cord in the subarachnoid space (between the arachnoid mater and the pia mater)
CSF
are four CSF-filled cavities within the brain
Ventricles
The lateral ventricles together comprise the __ ventricle
first and second
A thin membrane called the ___ separates the lateral ventricles
septum pellucidum
The ___ is a narrow cavity surrounded by the right and left halves of the thalamus
third ventricle
The ____ is between the brain stem and the cerebellum
fourth ventricle
Mechanical protection, by serving as a shock-absorbing medium that protects the tissue of the brain and spinal cord from physical jolts; CSF also buoys the brain, causing it to “float” in the cranial cavity
CSF contribution to homeostasis
Chemical protection, by providing an optimal ionic composition chemical environment for accurate neuronal signaling
CSF contribution to homeostasis
Circulation, through acting as a medium for exchange of nutrients and waste products between the blood and nervous tissue
CSF contribution to homeostasis
CSF is produced by the ___ in the walls of the ventricles
choroid plexuses
These are networks of capillaries covered by ependymal cells that form CSF from blood plasma by filtration (and some secretion)
The ___ are joined by tight junctions, thereby preventing materials from leaking between the cells, and forcing materials that might potentially enter the CSF to be subjected to ependymal cell selectivity
ependymal cells
CSF is formed in the choroid plexuses of ___ lateral ventricle
each
CSF flows into the third ventricle through two small openings called ___
interventricular foramina
The roof of the ___ ventricle produces more CSF
third
CSF then flows through the ___ and into the fourth ventricle
cerebral aqueduct
A ___ in the fourth ventricle produces more CSF
choroid plexus
From the fourth ventricle, CSF enters the ___ through three openings in the roof of the fourth ventricle: a median aperture, and two lateral apertures (a pair—one on each side)
subarachnoid space
Since the subarachnoid spaces of the brain and spinal cord are continuous, CSF also enters the spinal ___space
subarachnoid
CSF then circulates in the ___ of the spinal cord and the subarachnoid spaces of the brain and spinal cord
central canal
CSF is reabsorbed into the blood through arachnoid __, which project into the CSF circulatory spaces
villi
It is normally reabsorbed as fast as it is formed, meaning the pressure remains constant
Hydrocephalus (hydro = water, cephalus = head) is a condition in which excess ___ builds up in the brain
cerebrospinal fluid
When excess CSF accumulates in the ventricles, CSF pressure rises, causing ___
hydrocephalus
If the condition persists the fluid buildup compresses and damages nerve tissue
Hydrocephalus is most often treated with the surgical placement of a ___ system that diverts the flow of CSF from a site within the central nervous system (CNS) to another area of the body where it can be absorbed as part of the circulatory process.
shunt
A limited number of patients having OBSTRUCTIVE hydrocephalus can be treated with a procedure called ___. Aided by a neuroscope, a small hole is made in the floor of the __ ventricle, allowing the CSF to bypass the obstruction
third ventriculostomy
third
A network of interspersed gray and white matter called the reticular formation extends throughout the
brain stem
DUH
called the vital brain because it regulates functions upon which life is most dependent, and which occur without our voluntary action
Medulla oblongata
control of breathing, heart rate, blood pressure, and reflex centers for coughing, swallowing, & vomiting that respond without cognitive processing
Medulla oblongata
The medulla begins at the ___, and is a continuation of the spinal cord
foramen magnum
White matter of the medulla contains all ascending (sensory) and descending (motor) tracts between the ___ and other parts of the brain
spinal cord
The ___ of white matter on the anterior where the largest motor tracts pass from the cerebrum to the spinal cord
(brain stem)
pyramids are bulges
The pyramids represent the ___ tracts
brain stem
corticospinal
Most of the axons in the left pyramid cross to the right side (___), and vice versa
decussate
This is called decussation of pyramids
The medulla has several ___ (masses of gray matter where neurons form synapses with one another) that control vital body functions
nuclei
Cardiovascular center
Medullary rhythmicity area
The deglutition center
gustatory nucleus
Cochlear nuclei
Vestibular nuclei
Medullary nuclei
(masses of gray matter where neurons form synapses with one another) that control vital body functions
regulates rate and force of the heartbeat and blood vessel diameter
Cardiovascular center
(part of the respiratory center) adjusts the basic rhythm of breathing
Medullary rhythmicity area
____of the medulla promotes swallowing of a mass (bolus) of food that has moved from the mouth into the pharynx (throat)
deglutition center
Other nuclei in the medulla also control…
Coughing, which involves a long drawn and deep inhalation followed by a strong exhalation
Hiccupping, caused by spasmodic contraction of the diaphragm
Sneezing, the spasmodic contraction of breathing muscles that forcefully expel air through the nose and mouth
The vomiting center ___ of the medulla causes vomiting, the forcible expulsion of the contents of the upper gastrointestinal tract through the mouth
(area postrema)
comprises part of the ____ pathway from the tongue to the brain, receiving input from taste buds of the tongue
gustatory nucleus
gustatory
receive auditory input from the cochlea of the ear, and are therefore part of the auditory pathway
Cochlear nuclei
are components of the equilibrium pathway from the inner ear to the brain, receiving sensory information from vestibular apparatus of the inner ear
Vestibular nuclei
Lateral to each pyramid is an oval-shaped swelling called an
olive
inferior olivary nucleus within each olive relays impulses to the cerebellum from the cerebral cortex, red nucleus of the midbrain, and spinal cord proprioceptors ____
that monitor joint and muscle position
The right and left gracile nucleus and cuneate nucleus are in the ___ part of the medulla
posterior
right and left gracile nucleus and cuneate nucleus are associated with sensations of touch, conscious proprioception, ___, and ____
pressure
vibration
First-order sensory neurons having their cell bodies in dorsal roots of the spinal cord ascend in the posterior columns to the posterior nuclei of the medulla
Posterior nuclei
There they synapse with second-order neurons having their cell bodies in the correspondingly-named posterior nucleus of the medulla
Posterior nuclei
second-order neurons ascend to the THALAMUS in a band of white matter called the
medial lemniscus (lemniscus = ribbon)
The medial lemniscus extends through the medulla, pons, and ___
midbrain
tracts of the posterior columns and axons of the medial lemniscus are collectively known as the _____________
posterior column-medial lemniscus pathway
A hard blow to the __ of the head or upper neck can be fatal due to damage to the medulla
back
Damage to the medullary rhythmicity area is especially serious, and can lead to death
Symptoms of injury to the medulla include paralysis and loss of sensation on the opposite side of the body, and irregularities in breathing or heart rhythm
The ___ (=bridge) is superior to the medulla
pons
Consists of both nuclei, sensory tracts, and motor tracts (like the medulla)
pons
It is a bridge that connects one part of the brain with another
pons
Connections provided by the pons between parts of the brain are by bundles of axons, both laterally (connecting the left and right sides of the cerebellum), and vertically (comprising ascending sensory, and descending motor tracts)
Pontine structures
____ nuclei relay signals for voluntary movements from their origin in the cerebral cortex to the cerebellum
Pontine
Nuclei comprising the ___ area and ___ area (in the pons) help control breathing, in conjunction with the medullary rhymicity area of the medulla
pneumotaxic
apneustic
Action of respiratory muscles is controlled by bilateral clusters of neurons in both the medulla oblongata and pons, collectively called the respiratory center and comprising
Medullary rhythmicity area
Pneumotaxic area
Apneustic area
(in the medulla) controls the basic rhythm of respiration, and consists of the inspiratory area and the expiratory area
medullary rhythmicity area
When the inspiratory center is active, it generates nerve impulses to the ____ intercostal muscles and the diaphragm, resulting in inspiration
external
During normal quiet breathing, absence of inspiratory impulses from the inspiratory center relaxes inspiratory muscles, resulting in exhalation due to __ elastic recoil of the lungs and thoracic wall
passive
___ center neurons are inactive during quiet breathing. During forceful breathing, impulses from the expiratory area are sent to the internal intercostal muscles and abdominal muscles. Contraction of these muscles causes forceful exhalation
Expiratory
The ___ area turns off the inspiratory area before the lungs become too full
pneumotaxic
The ___ area prolongs inhalation by sending stimulatory impulses to the inspiratory area
apneustic
The pneumotaxic area and the apneustic area coordinate the transition between inhalation and exhalation
The vestibulocochlear (VIII) nerve has nuclei in two parts of the ___
brain stem, pons and medulla
The ___ has sensory axons that end in the vestibular nuclei in the pons (although some enter the cerebellum via the inferior cerebellar peduncle)
vestibular branch
The ___ has sensory axons that end in nuclei in the medulla oblongata
cochlear branch
Axons of motor neurons in both branches project from the pons to respective hair cells in the semicircular canals and ___
spiral organ
Midbrain is also termed the
mesencephalon
Connects the pons to the diencephalon (thalamus, hypothalamus, etc.)
Midbrain
It consists of both nuclei and tracts (like the medulla and pons)
pair of tracts containing axons of motor neurons that conduct nerve impulses from the cerebral cortex to the spinal cord (corticospinal), medulla (corticobulbar), and pons (corticopontine), as well as axons of sensory neurons that extend from the medulla to the thalamus
cerebral peduncles
big tract of descending motor neurons
contains two pairs of rounded elevations collectively called the corpora quadrigemina (= quadruplets)
(midbrain)
tectum
___ passes through the midbrain, connecting the third ventricle above with the fourth ventricle below
cerebral aqueduct
Comprise the superior colliculi and inferior colliculi
Corpora quadrigemina
are reflex centers for visual reflexes and for visually tracking moving objects
(Corpora quadrigemina )
superior colliculi
part of the auditory pathway as well as reflex centers for auditory stimuli
(Corpora quadrigemina )
inferior colliculi
This is the center responsible for involuntary turning of the head when an object is detected “out of the corner of the eye”
Superior colliculi
Provide some of the neural circuitry that contributes to movement of extrinsic eye muscles for tracking moving images. Circuits extend from retina of the eye to superior colliculi, then to extrinsic eye muscles
Various visual reflexes:
Pupillary reflex: adjusts size of the pupil
Accommodation reflex: shape of lens for close and distant viewing
Part of the auditory pathway that relays impulses from hearing receptors in the inner ear to the thalamus
Inferior colliculi
center responsible for the startle reflex, which is the involuntary turning of the head in response to an unexpected sound
Inferior colliculi
Large darkly pigmented nuclei that release dopamine
Helps control subconscious muscle activities
Loss of these neurons is associated with Parkinson disease
Substantia nigra
nucei in midbrain
Reddish due to rich blood supply and iron-containing pigment in neuron cell bodies
Axons from cerebellum and cerebral cortex synapse with the red nuclei, functioning in the coordination of muscular movements
Red nuclei
The rubrospinal tract originates in the red nucleus
The red nucleus controls crawling of babies and swinging of arms in normal walking. It and the rubrospinal tract are primarily involved in control of large muscles of the shoulder and arm, with sparse control over the hands, but not fine control of the fingers which is performed by the corticospinal tract. It does not affect the lower limbs since the rubrospinal tract terminates in the superior thoracic region of the spinal cord
red nuclei
midbrain
Much of the brainstem consists of small clusters of neuronal cell bodies along with small bundles of myelinated axons
This fairly extensive region of interspersed gray and white matter in the brain stem is termed the
reticular formation
The main function of neurons that descend from the ____ is to help regulate muscle tone (the slight degree of contraction that occurs in normal resting muscles)
reticular formation
Part of the reticular formation called the ____ consists of sensory axons that help maintain consciousness and participate in awakening from sleep
reticular activating system (RAS)
Second-largest part of the brain
But half of the neurons
cerebellum
The surface has many ridges, or convolutions, called ___ (leaves)
(cerebellum)
folia
The central constricted area is termed the ___ (worm)
The lateral lobes are the cerebellar hemispheres
vermis
The cerebellar ___ is gray matter, also exhibiting the foliar ridges
The white matter forms the ___ (tree of life)
cortex
arbor vitae
____ are bundles of white matter comprising axons that conduct impulses between the cerebellum and other parts of the brain
Cerebellar peduncles
There are three pairs of cerebellar peduncles: superior, middle, and inferior
CEREBRAL peduncles are ___ structures that conduct nerve impulses from the cerebrum to the spinal cord, medulla, and pons.
CEREBELLAR peduncles are ___ structures that conduct impulses between the cerebellum and other parts of the brain.
anterior
posterior
The main function of the ____ is to evaluate how well movements initiated by motor areas in the cerebrum are actually being carried out, by comparing what was intended with what is actually being done
cerebellum
When discrepancies are detected it sends feedback signals to motor areas of the cerebral cortex, thereby providing for smooth, coordinated movement
cerebellum
___ is also the main region of the brain that regulates posture and balance
cerebellum
The ____ mediate unconscious refinements of skeletal muscle movements
(cerebellum)
anterior and posterior lobes
The ____ lobe contributes to equilibrium and balance
cerebellum
floculonodular
an inability to coordinate muscular movements
Ataxia
describes a symptom of incoordination associated with cerebellar infections, injuries, diseases, or degenerative changes
Ataxia
Speech patterns are abnormal due to uncoordinated speech muscles
Comprises: Thalamus Hypothalamus Epithalamus Subthalamus
Diencephalon
Surrounds the third ventricle
Extends from brain stem to cerebrum
Diencephalon
Makes up most of the diencephalon
Consists of paired oval masses of gray matter organized into nuclei, plus some white matter tracts
Thalamus
The two halves (of dienchepalon) are connected across the third ventricle by a bridge of gray matter called the
intermediate mass
main relay station for most sensory impulses that reach the primary sensory areas of the cerebral cortex from the spinal cord, the brain stem, or the midbrain
thalamus
sorting out and information editing process occurs wherein impulses having similar functions are grouped together and relayed to the appropriate area of the sensory cortex and cortical association centers
thalamus
also contributes to regulation of autonomic activities and maintenance of consciousness
a thick band of white matter lateral to the thalamus which separates the thalamus and caudate nucleus from the lentiform nucleus
internal capsule
small portion of the diencephalon located inferior to the thalamus
controls many body activities, and is a major regulator of homeostasis
Hypothalamus
serve as relay stations for reflexes related to the sense of smell
Mammillary bodies
the major structure of concern for the tuberal region
infundibulum
It is the stalk that connects the pituitary gland to the hypothalamus
main visceral control center of the body, and is one of the major regulators of homeostasis. Few tissues in the body escape its influence
hypothalamus
has an important involvement with the pituitary gland. The pituitary gland is an endocrine gland that exerts major control over other endocrine glands, so it is the “boss” over much of the endocrine system. The hypothalamus is the “boss” of the pituitary, so in effect it is the “bosses boss.”
hypothalamus
Glucose level
Osmotic pressure (osmoreceptors)
Temperature of blood flowing through the hypothalamus
Various hormones (insulin, for example)
Control of the autonomic nervous system
Production of hormones
Regulation of emotional and behavioral patterns
Regulation of eating and drinking
Control of body temperature
Regulation of circadian rhythms and states of consciousness
Functions of the hypothalamus
comprises the habenular nuclei and pineal gland, and is superior and posterior to the thalamus
epithalamus
are involved in olfaction, especially emotional responses to odors
(Epithalamus)
Habenular nuclei
secretes the hormone melatonin, and is part of the endocrine system
(Epithalamus)
The pineal gland
small area containing tracts and the paired subthalamic nuclei, lying immediately below the thalamus
subthalamus
It works with other structures of the brain to control body movement
