Chapter 14: The Brain and Cranial Nerves Flashcards
What does the telencephalon walls and cavity turn into?
Walls: Cerebrum
Cavities: Lateral ventricles
What does the diencephalon walls and cavity turn into?
Walls: Thalamus, hypothalamus, and epithalamus
Cavity - Third ventricle
What do the walls and cavities of the Mesencephalon form into?
Walls: midbrain
Cavity: aqueduct of midbrain
What do the walls and cavity of the metencephalon form into?
Walls: pons and cerebellum
Cavity: upper part of 4th ventricle
What do the walls and cavity of the myencephalon form into?
Walls - medulla oblongata
Cavity - Lower part of 4th ventricle
The 4 main parts of the adult brain:
- Brainstem
- Cerebellum
- Diencephalon
- Cerebrum
This brain structure is continuous with the spinal cord and consists of the medulla oblongata, pons and midbrain
The brainstem
What are the 3 components/structures of the brainstem?
The pons
The Mid Brain
The Medulla OblongataW
What main brain structure is posterior the brain stem?
The cerebellum
What main structure is superior the brain stem?
Diencephalon
What are the 3 components of the diencephalon in the brain?
The thalmus, hypothalmus and the epithalmus
This is the largest part of the brain and it is the most superior structure
Cerebrum
Four principle parts of an adult brain and their sub components
*brainstem - pons, midbrain, medulla oblongata
*diencephalon - thalmus, hypothalmus and epithalmus
*cerebrum
*cerebellum
Common layers ofthe cranial meninges
Dura mater
Arachnoid Mater
Pia Mater
What are the two layers of the cranial dura mater?
- Periosteal layer (outer)
- Meningeal layer (inner)
What are the dural venous sinuses
They drain venous blood from the brain and deliver it into the internal jugular veins
What are the three extensions of dura mater that seperate parts of the brain
- Falx cerebri
- Falx cerebelli
- Tentorium cerebelli
What is the function of the falx cerebri?
Seperate the two hemispheres of the cerebrum
What is the function of the Falx Cerebelli?
Seperates the hemispheres of the cerebellum
What is the function of the tentorium cerebelli?
Seperates the cerebrum from the cerebellum
How does the blood mainly flow to the brain?
Through the internal carotid and the vertebral arteriesW
What do the dural sinuses drain into?
The internal jugular vains
What is the percentage of body weight represented by the brain?
2%
What percentage of oxygen and glucose does the brain consume?
20%
How long does an interurption of blood flow to the brain need to be to start impairing neuronal function?
1-2 minutes
How long does the brain need to be totally deprived of oxygen before permanent brain damage develops?
4 minutes
Why does the flow of glucose to the brain need ot be continuous?
There is no glucose stores in the brain
Symptoms of low blood glucose to the brain?
mental confusion, dizziness, convulsions, and loss of consciousness
This strucutre consists mainly of tight junctions that seal together the endothelial cells of the brain blood capillaries and a thick basement membrane that surrounds the capillaries
The blood brain barrier
What types of substances are passable through the blood brain barrier by diffusing across the lipi bilayer of endothelial cell plasma membranes?
lipid soluble substances like steroid hormones, alcohol, barbituates, nicotine, and caffeine
water molecules, 02 and C02
What substance rapidly cross the BBB by facilitated transport?
A few water soluble substances like glucose
What substances often do not pass the BBB
proteins and most antibiotic drugs
A clear, colorless liquid composed primarily of water that protects the brain and spinal cord from chemical and physical injuries
Cerebrospinal Fluid
This is the space the cerebrospinal fluid is found in the brain and spinal cord
The subarachnoid space
The total colume of CSf in an adult
80-150ml
These cations are found in CSF
Potassium, calcium, magnesium, and sodium
These anions are found in CSF
Chloride and HC03-
Other substances found in CSF
Small amount of glucose, white blood cells, protein, urea, lactic acid
These are basically the first and second ventricles, one found in each brain hemisphere of the cerebrum
Lateral Ventricles
This thin membrane separates the lateral ventricles anteriorly
The septum pellucidum
This brain structure is a narrow, slit like cavity, along the midline superior to the hypothalamus and between the right and left halves of the thalamus
Third ventricle
This ventricle is located between the brain stem and the cerebellum
The fourth ventricle
The three basic functions of the CSF in maintaining homeostasis
- Mechanical Protection
- Chemical Protection
- Ciculation
One of these on each side of the brain connects the lateral ventricles to the third ventricle
Interventricular foramen
This structure connects the third ventricle to the fourth ventricle
The mid brain aqueduct
This structure is a network of blood capillaries in the walls of the ventricles and is where the majority of CSF production occurs
The choroid plexuses
These neuroglia cells permit selective transport of water and other substances from within the blood capilliaries, into and from the CSF; the substances must pass through the cell bodies
Ependymal
These structures are found between the ependymal cells that cover the capilliaries of the choroid plexuses and account for the inability of substances to pass directly between the CSF and blood capilliaries
Tight junctions
The ependymal cells create this barrier that protects the brain and spinal cord from potentially harmful blood born substances
Blood-cerebrospinal fluid barrier
Tight junctions of brain capillary endothelial cells creates this barrier
Blood brain barrier
The CSF is produced by the choroid plexuses in the lateral ventricles and then flows…
through the interventricular foramina and into the third ventricle
These are the two narrow, oval openings through which CSF flows from the lateral ventricles to the third ventricle
The interventricular foramina
This part of the third ventricle adds more CSF production
The choroid plexus of the third ventricle located on its superior surface
The CSF then travels down through the aqueduct of the midbrain , passing through the midbrain and into…
The fourth ventricle
In the fourth ventricle, more CSF is added by…
the choroid plexus of the fourth ventricle
How does CSF enter the subarachnoid space from the fourth ventricle?
There are 3 openings in the fourth ventricle that the CSF enters the subarachnoid space through
These are the names of the 3 apertures that are openings in the fourth ventricle for CSF to enter the subarachnoid space
1x Median aperture
2x lateral apertures
Once the CSF enters the subarachnoid space, where does it circulate in the brain and spinal cord?
Into the central canal of the spinal cord, and around the surface of the brain and spinal cord in the subarachnoid space
WHat is an arachnoid granulation?
A cluster of arachnoid villi that absorb CSF
These are fingerlike extensions of the arachnoid mater that project into the dural venous sinuses and slowly reabsorb CSF
Arachnoid Villi
At what rate is CSF typically produced and reabsorbed
20mL per hour so 480mL per day
What two things remain constant due to simultaneous production and reabsorption of CSF
The volume of CSF and the pressure of CSF
This is the main location of reabsorption of CSF by arachnoid villi clusters called arachnoid granulations
The superior sagittal sinus
This is a netlike region of interspersed gray and white matter, extending through the brainstem
The reticular formation
These are the 3 structures of the brainstem
- Pons
- Medulla oblongata
- Midbrain
This structure of the brainstem begins at the foramen magnum and extends to the inferior border of the pons; it is continuous with the superior portion of the spinal cord and it forms the inferior portion of the brain stem
the medulla oblongata
The medullas white matter contains all sensory and motor tracts that extend between:
The spinal cord and other parts of the brain
These are bulges of white matter on the anterior aspect of the medulla
The pyramids
The pyramids of the medulla oblongata are formed from what tracts?
The corticospinal tracts that control voluntary movement of the limbs and trunk
What happens to the corticospinal tracts just superior the junction where the medulla and spinal cord join?
90% of the corticospinal tract axons of the left pyramid, cross to the right side, and vice versa right to left
What is the term to describe the crossing over of the corticospinal axons in the pyramid?
Decussation of pyramids
What structure of the medulla oblongata pyramids explains the voluntary control of each side of the body by the opposite side of the brain?
The decussation of pyramids
The medulla contains several of these structures that are collections of neuronal bodies within the CNS
Nuclei
What does some of these nuclei control?
Vital body functions
What does the cardiovascular (CV) center regulate?
Rate and force of heart beat and diameter of blood vessels
What does the medullary respiratory center regulate?
Basic rhythm of breathing
What center of the medulla controls the reflex for vomitting?
The vomitting center
This nuceli in the medulla controls the reflex of swallowing when a mass of food has moved from the oral cavity into the pharynx
Deglutition Center
This reflex is controlled by nuclei in the medulla and involves spasmodic contraction of breathing muscles that forcefully expel air through the nose and mouth
Sneezing
This reflex is controlled by nuclei in the medulla and involves a long-drawn and deep inhalation and the a strong exhalation that suddenly sends a blast of air through the upper respiratory passages
Coughing
This reflex is controlled by nuclei in the medulla and involves the spasmodic contractions of the diaphragm that ultimately result in the production of a sharp sound on inhalation
Hiccuping
These oval shaped swellings are found just lateral to each medulla pyramid
Olives
Where are the inferior olivary nucleus located?
Within the olive, just lateral the pyramids
Where does the inferior olivary nucleus receive input from?
The cerebral cortex, red nucleus of the midbrain and spinal cord
What do the axons of the inferior olivary nucleus that extend into the cerebellum control?
The regulate the activity of cerebellar neurons
These two nuclei are found in the posterior part of the medulla oblongata; they each synapse with the two tracts in the posterior columns of the spinal cord that have similar names; are associated with sensations of touch, pressure, vibration, and conscious proprioception
Gracile nucleus
Cuneate nucleus
These two tracts form synapses with the gracile and cuneate nuclei
The gracile and cuneate fasciculus
Information travels up the gracile and cuneate fasciculus and then to the gracile and cuneate nuclei. Then postsynaptic neurons relay the sensory information to:
The thalamus on the opposite side of the brain.
The sensory information travels the axons to the thalmus in a band of white matter called:
the medial leminscus
The medial lemniscus is a white band of matter that travels through:
the medulla, pons and midbrain to the thalamus
The posterior column-medial lemniscus pathway is composed of??
The tracts of the posterior columns and the axons of the medial lemniscus
What nucleus is a part of the pathway from the tongue to the brain and receives gustatory information from taste buds of the tongue
The gustatory nucleus of the medulla
This nuclei of the medulla are part of the auditory pathway from the inner ear to the brain and receive auditory input from the cochlea of the inner ear
Cochlear Nuclei
This nuclei of the medulla and the pons is a component of the equilibrium pathway from the inner ear to the brain and receives information associated with equilibrium from proprioreceptors int he vestibular apparatus of the inner ear
Vestibular Nuclei
The medulla also contains nuclei associated with these 5 pairs of cranial nerves:
- vestibulocochlear (VIII) nerves
- Glossopharyngeal (IX) Nerves
- Vagus (X) nerves
- Accessory (XI) Nerves
- Hypoglossal (XII) nerves
This cranial nerve receives sensory input and provides motor output to the cochlea of the internal ear; hearing related impulses
Vestibulocochlear (VIII) nerve (8)
This cranial nerve nuclei found in the medulla relays sensory and motor information related to taste, swallowing, and salivation
The glossopharyngeal nerve (IX)
This cranial nerve has its nuclei in the medulla that receives sensory impulses from and provide motor impulses to the pharynx, larynx, and many thoracic and abdominal viscera
The vagus nerve (X)
The cranial portion of these nerves are part of the Vagus Nerve (X); nuclei in the medulla are the origin for nerve impulses that control swallowing via the vagus nerves
Accessory Nerves (cranial portion) (XI)
The nerves associated with these nuclei in the medulla are origin for nerve impulses that control tongue movements during speech and swallowing
The hypoglossal nerve (XII)
This brainstem structure lies directly superior to the medulla oblongata and anterior the cerebellum; it is about 2.5cm long and also consists of both nuclei and tracts
The PONS
Also means bridge; it is the bridge that connects parts of the brain with one another
What do the bundles of axons in the pons connect or bridge??
The right and lift sides of the cerebellum; some are part of the ascending sensory tracts and descending motor tracts
Two major structural components of the PONS
the ventral region
The dorsal region
The ventral region of the pons forms:
a large synaptic relay station
What are the scattered gray centers in the ventral region of the pons called/
Pontine nuclei
What does the numerous white tracts entering and exiting the pontine nuclei do?
They each provide a connection between the cerebral cortex (outer layer) to the opposite hemisphere of the cerebellum
What does this complex circuitry of the pontine nuclei and white matter tracts do?
Play an essential role in coordinating and maximizing the efficiency of voluntary motor output throughout the body
What is the dorsal region of the pons composed of?
Ascending sensory and descending motor tracts as well as the nuclei of cranial nerves
Where are the nuclei of cranial nerves in the pons located
IN the dorsal region
This structure within the pons coordinates with the medulla respiratory center to help control breathing
the pontine respiratory group
What four cranial nerves have their nuclei in the pons?
- Trigeminal nerve s(V)
- Abducents (VI) nerves
- Facial (VII) nerves
- Vestibulocochlear (VII) Nerves
These cranial nerves whose nuclei are in the pons, receive sensory impulses for somatic sensations from the head and face and provide motor impulses that govern chewing
Trigeminal (V) Nerves
This set of cranial nerves has it’s nuclei in the pons and provides motor impulses that control eyeball movement
Abducens Nerve (VI)
This set of cranial nerves has it’s nuclei in the pons and receives sensory impulses for taste and provide motor impulses to regulate the secretion of saliva and tears and contraction of muscles of facial expression
The facial (VII) nerve
This set of cranial nerves has it’s nuclei in the pons and receives sensory impulses from and sends motor impulses to the vestibular apparatus and convey impulses related to balance and equilibrium
The vestibulocochlear nerves (VIII)
What is the mesencephalon?
The midbrain
Where is the midbrain found?
Between the diencephalon and the pons
How big is the midbrain
2.5 cm like the pons
