Chapter 5: The Brain Flashcards
The earliest phase of brain development starts in the __________ of pregnancy.
third week
The _________ thickens along the dorsal midline axis of the embryo, to form the _________ . This eventually gives rise to all neural tissue.
ectoderm
neural plate
The neural plate then forms a groove flanked by __________ . As the groove deepens, the superior edges of the neural folds fuse, forming the __________ . The neural tube then detaches from the surface ectoderm and assumes a deeper position.
neural folds
neural tube
During the __________ of pregnancy , the neural tube is formed and starts to differentiate into the CNS. The _______ forms anteriorly and the spinal cord develops from the posterior portion of the neural tube.
4th week
brain
Small groups of neural fold cells migrate laterally from between the surface ectoderm and the neural tube to form the tissue called ____________ . gives rise to sensory neurons and some autonomic neurons.
the neural crest
3 primary brain vesicles:
- Prosencephalon
- Mesencephalon
- Rhombencephalon
Prosencephalon is also known as:
Forebrain
Rhombencephalon is also known as:
Hindbrain
Mesencephalon is also known as:
Midbrain
Once the neural tube is formed, its anterior begins to expand more rapidly than the remaining portion. Now ______________ are marked off. The remainder of the neural tube becomes the _________ .
3 primary brain vesicles
spinal cord
By week 5, the secondary brain vesicles become apparent. The forebrain has divided into the ____________ and the ____________ .
Telencephalon (endbrain)
Diencephalon (interbrain)
The hindbrain has constricted to form the ____________ and the ______________ and the midbrain remains undivided.
metencephalon (afterbrain)
myelencephalon (spinal brain)
What are the 5 secondary brain vesicles?
Telencephalon (endbrain)
Diencephalon (interbrain)
Metencephalon (afterbrain)
Myelencephalon (spinal brain)
Mesencephalon (Midbrain)
The telencephalon sprouts two swellings which expand to become the cerebral hemispheres called __________ .
cerebrum
The diencephalon specializes to form the ___________ , __________ and __________ .
hypothalamus
thalamus
epithalamus
True or False:
- The mesencephalon, metencephalon and myelencephalon become the midbrain, pons and cerebellum and medulla oblongata.
- The midbrain, pons and medulla become the brain stem.
True
The central cavity of the neural tube remains continuous and becomes enlarged in four areas, to form the fluid-filled ________ of the brain.
ventricles
These are the Regions of the Brain. Except:
- Cerebrum
- Pons
- Hypothalamus
- Epithalamus
- Brainstem
- Cerebellum
- Pons
Pons is one of the three parts of the Brainstem. It should be Thalamus.
____________ - Largest and most superior part of the human brain and is composed of ______________ , together they account for about _____ of total brain mass.
Cerebrum
two cerebral hemispheres
83%
Each hemisphere of cerebrum is consists of the:
a) Cerebral cortex
b) Cerebral white matter
c) Basal nuclei
The cerebral hemispheres are marked by elevated ridges of tissue called ______.
Gyri
The cerebral hemispheres are separated by shallow grooves called ______ . Deeper grooves are called _______ which separate large regions of the brain.
Sulci
fissures
The ______________ separates the cerebral hemispheres. The ____________ separates the cerebral hemispheres from the cerebellum.
median longitudinal fissure
transverse fissure
Deep Sulci divide each hemisphere into _______ .
lobes
___________ - separates the frontal lobe from the parietal lobe.
Central Sulcus
______________ - separates the parietal lobes from the occipital lobe.
Parieto- occipital Sulcus
___________ - separates the temporal lobe from parietal and frontal lobes.
lateral sulcus
__________ , which makes up the floor of the lateral sulcus and is covered by parts of temporal, parietal and frontal lobes.
Insula
____________ - Mental processes of all types including sensations, consciousness, memory and voluntary control of movement.
Cerebrum
The Cerebral cortex has specific areas that control specific functions in the body. Which statement is false?
- Frontal lobe controls motor control.
- Parietal lobe controls planning.
- Temporal lobe controls hearing (auditory)
- Occipital lobe controls vision.
Answer: Number 2
Correct: Parietal lobe controls sensory
In 97 % of the population, language areas are located in the ___________ .
left hemisphere
The production of speech occurs in ____________ located in the left frontal lobe, in most people.
Broca‟s speech area
It is composed of dendrites and cell bodies of neurons and unmyelinated axons, glia and blood vessels.
Cerebral cortex
Functions of Cerebral cortex:
It enables us to perceive communication, remember, understand, appreciate and initiate behaviour.
The cerebral cortex contains three kinds of functional areas:
Motor areas
Sensory areas
Association areas
_____________ - integrate diverse information for purposeful action.
Association areas
__________ - control voluntary motor functions.
Motor areas
___________ - provide for conscious awareness of sensation.
Sensory areas
True or False:
Each hemisphere is chiefly concerned with the sensory and motor functions of the opposite side of the body.
True
___________ - Deep to the gray matter of the cortex and provides for the communication between cerebral areas and between the cerebral cortex and lower CNS centres.
Cerebral White Matter
What consists the Cerebral White Matter ?
It consists largely of myelinated fibres bundled into large tracts.
_________ - Gray matter areas located deep within the white matter of the cerebral hemispheres.
Basal Nuclei
____________ - fiber tract that connects the two cerebral hemispheres.
Corpus Callosum
What is the functions of Basal Nuclei?
Their functions can overlap with the cerebellum and they play a role in motor and cognition functions.
Egg shaped and makes up 80% of the diencephalon and forms superolateral walls of the third ventricle.
Thalamus
Thalamus is composed of:
It is composed of bilateral masses of gray matter, held together by a midline commissure called the intermediate mass.
Major relay station for the sensory impulses, ascending to the cerebral cortex.
Thalamus
Which Statement regarding Thalamus is False?
- It has many different nuclei which are named for their function.
- Afferent impulses from all senses and all parts of the body, converge on the thalamus and synapse with at least one of its nuclei.
- Within the thalamus, there is an editing process where impulses having to do with similar functions are grouped together and conveyed to the appropriate area.
1
It has many different nuclei which are named for their location.
____________ - It extends from the optic chiasma to the posterior margin of the mammillary bodies .
Hypothalamus
A paired pea-like nuclei that bulge anteriorly from the hypothalamus.
mammillary bodies
Between the optic chiasma and mammillary bodies is the ___________.
infundibulum
Major centre for controlling the Autonomic Nervous System (helps control function of most internal organs). ). Controls hormone secretion by the anterior and posterior pituitary gland. Contains centres for controlling appetite, wakefulness, pleasure, etc.
Hypothalamus
It is the main visceral control centre of the body and is important for body homeostasis.
infundibulum
Chief homeostasis roles of Hypothalamus, Except:
- Parasympathetic control centre - i.e. blood pressure
- Centre for emotional response and behaviour i.e. - perception of pain, pleasure, etc.
- Body temperature regulation
- Regulation of food intake
- Regulation of water balance and thirst
- Sleep-wake cycles
- Control of endocrine system
1
Autonomic control centre
____________ - is the most dorsal portion of the diencephalon and forms the roof of the third ventricle. Extending from its posterior border is the pineal gland.
Epithalamus
__________ - consists of white matter with bits of gray matter, deep to, and scattered throughout it. It provides a pathway for fibre tracts running between higher and lower neural centres.
Brainstem
What are the three parts of brainstem?
a) Midbrain
b) Pons
c) Medulla Oblongata
False statements regarding Overall functions of Brainstem. Except:
- Gray matter functions as autonomic reflex centres (heartbeat, respiration and blood vessel diameter).
- Motor tracts conduct impulses to higher centres of the brain.
- Sensory tracts conduct impulses from the higher centres in the brain to the spinal cord.
Except: number 1
Correct:
- Sensory tracts conduct impulses to higher centres of the brain.
- Motor tracts conduct impulses from the higher centres in the brain to thespinal cord.
_____________ - Located between the diencephalon superiorly and the pons inferiorly. The ventral aspect has two bulging cerebral peduncles that seem to hold up the cerebrum.
Midbrain
Running through the midbrain is the hollow _____________. Surrounding the aqueduct is gray matter that contains nuclei, associated with two cranial nerves - _______ and _______ .
cerebral aqueduct
Oculomotor (lll)
Trochlear (lV)
The white matter also has nuclei scattered throughout. The largest of these is the _______________ which raise four domelike protrusions on the dorsal midbrain surface.
corpora quadrigemina
The superior pair ( _________ ) are visual reflex centres. _________ are part of auditory, from hearing receptors (startle reflex).
superior colliculi
Inferior colliculi
Found between the midbrain and medulla oblongata. Fibre direction course in two different pathways.
Pons
_________ run longitudinally and complete the superior-inferior pathways between higher brain centres and the spinal cord; and the _____________ relay communication between the motor cortex and the cerebellum.
Deep fibres
superficial ventral fibres
Several cranial nerve pairs issue from the pons nuclei such as _____, _____, and _____. .
CN V
CN VI
CN VII
It contains the respiratory centre to help maintain the normal rhythm of breathing.
Pons
This is the most inferior part of the brainstem. It blends into the spinal cord at the level of the foramen magnum of the skull. It also helps to form the ventral wall of the fourth ventricle.
Medulla Oblongata
Important visceral motor nuclei found in the medulla include:
a. The cardiovascular centres
b. Respiratory centres
c. Various other centres which regulate activities, (like vomiting, sneezing, swallowing.)
This is the second largest part of the brain and is located dorsal to the pons and medulla.
Cerebellum
Cerebellum processes:
It processes inputs received from the cerebral motor cortex, various brainstem nuclei and sensory receptors.
Overall functions of Cerebellum:
Helps control muscle contractions to produce co-ordinated movements so that we can maintain balance, move smoothly and sustain posture.
They arise from expansions of the lumen of the embryonic neural tube. They are continuous with each other and with the central canal of the spinal cord.
Ventricular System of the brain
Ventricular System of the brain are filled with __________ and lined by __________ .
cerebrospinal fluid
ependymal cells
The four ventricles in the Brain:
Two lateral ventricles
Third ventricle
The fourth ventricle
___________ - are large C-shaped chambers. Each one is located deep within a cerebral hemisphere.
Two lateral ventricles
Two lateral ventricles are anteriorly lie close together but separated by the thin ____________ (median membrane).
septum pellucidum
__________ - is found in the Diencephalon. It communicates with the lateral ventricles via the ______________ .
Third ventricle
interventricular foramen
____________ - is connected to the third ventricle via the cerebral aqueduct that runs through the Midbrain.
fourth ventricle
Where is the fourth ventricle can be found?
It is found dorsal to the Pons and superior Medulla and is continuous with the central canal.
Three openings that connect the fourth ventricles to the subarachnoid space :
the paired lateral apertures
the median aperture
What secretes the cerebrospinal fluid?
CSF is mostly secreted by the choroid plexuses of the ventricles
___________ - fills the ventricles and the sub-arachnoid spaces of the brain and spinal cord.
Cerebrospinal Fluid
_____________ - Capillary knot that hangs down from the roof of each ventricle (except 4th ventricle) and forms CSF.
Choroid Plexuses
Choroid Plexuses are clusters of broad thin-walled capillaries enclosed by a layer of modified ependymal cells ( ________________ ) lining the ventricles.
cuboidal epithelial cells
The ________________ are joined by tight junctions and have ion pumps that allow them to modify filtrate, by actively transporting only certain ions across their membranes into the CSF pool.
choroid plexuses ependymal cells
What is the consistency of the CSF?
The consistency of CSF is similar in composition to blood plasma (from which it arises). It contains less protein than blood plasma but more Vitamin C and the ion concentration is different.
Functions of Cerebrospinal Fluid, Except:
- help to cleanse the CSF by removing waste products and other unnecessary solutes.
- effectively reduces the brains weight by 97%
- protects the brain from crushing under its own weight.
- protects the brain and spinal cord from blows and other trauma.
- It also helps to nourish the brain.
- aids as antimicrobial agent that prevent infections.
Except: number 6
Not a function of CSF.
The CSF composition is important in the :
control of cerebral blood flow and breathing and also transports hormones along the ventricular channels.
Trace the Flow of CSF from the lateral ventricles through the fourth ventricle.
CSF leaves the lateral ventricles - interventricular foremina - 3rd ventricle - cerebral aqueduct - 4th ventricle ( most of the CSF enters the sub-arachnoid space via the lateral and medial apertures in the walls of the fourth ventricle )
Most CSF flows into the _________ and _____________. It also flows superiorly through the _______ and ________ on the medial and superolateral surfaces of the cerebral hemispheres.
interpeduncular
quadrigeminal
cisterns
sulci fissures
CSF passes into the extension of the subarachnoid space around the cranial nerves, the most important being the __________ .
optic nerve
The constant motion of the CSF is aided by :
the long microvilli of the ependymal cells lining the ventricles.
Absorption of CSF: The main site is into the venous system through the ______________ and through tiny protrusions of ___________ into the walls of the __________________ .
arachnoid granulations
arachnoid villi
dural venous sinuses
____________ are protective coverings of the brain and spinal cord
Meninges
Three connective tissue membranes that lie just external to the CNS. They cover and protect the CNS and blood vessels of the CNS.
Dura mater
Arachnoid mater
Pia mater
Meninges that is middle, web-like layer.
Arachnoid mater
Meninges that is tough and the outer layer .
Dura mater
Meninges that is innermost, delicate layer,
Pia mater
The arachnoid mater is separated from the __________ by ___________ .
dura mater
subdural space
Beneath the arachnoid mater is the _______________ that is filled with cerebrospinal fluid.
sub-arachnoid space
Pia mater is the delicate tissue layer that clings tightly to the surface of the _______ and _________ .
brain
spinal cord
What are the Two layers of Dura mater?
superficial layer
meningeal layer
_____________ - forms the outer most covering of the brain and continues as the dura mater of the spinal cord.
meningeal layer
____________ - is attached to the inner surface of the skull and forms the periosteal layer.
superficial layer
Superficial and meningeal layers are fused together except in areas:
In areas where they separate to enclose dural sinuses.
The blood supply to the brain comes from the __________ and ____________ which lie in the subarachnoid space.
internal carotid
vertebral arteries
____________ - arise in the neck from the ________________ which ascend vertically to the base of the skull and enter the cranial cavity through the carotid canals in the temporal bones.
internal carotid arteries
common carotid arteries
Within the carotid canals, the carotid arteries change direction passing anteriorly and medially. They run forward through the ________________ .
cavernous sinus
What are the temporal branches of the internal carotids?
the anterior and middle cerebral arteries
Near the termination of the internal carotid arteries they join to the _______________ by the ________________ , completing the cerebral arterial circle around the ______________ .
posterior cerebral arteries
posterior communicating arteries
interpeduncular fossa
____________ :Begin in the root of the neck as the first branches of the first part of the _____________. .
Vertebral Arteries
subclavian arteries
The left vertebral artery is larger than the right. The arteries pass through the _______________ of the first six cervical vertebrae.
transverse foremina
The _____________ of the vertebral arteries perforate the dura and arachnoid and pass through the foramen magnum.
sub-occipital parts
The vertebral arteries unite at the ___________ of the pons, to form the ___________ .
caudal border
basilar artery
Often referred to as the anterior circulation of the brain:
The anterior and middle cerebral arteries
It is called the posterior circulation of the brain.
The vertebrobasilar arterial system and branches
The basilar artery divides into two ________________ . Each cerebral artery supplies a surface and pole of the brain.
posterior cerebral arteries
Artery that supplies most medial superior surfaces of the brain and frontal pole.
Anterior cerebral artery
Artery that supplies the inferior surface of the brain an occipital pole.
Posterior cerebral artery
Artery that supplies the lateral surface of the brain and temporal pole.
Middle cerebral artery
Also known as Circle of Willis:
Cerebral arterial circle
Where is Circle of Willis can be found?
Found at the point of the base of the brain between the four arteries that supply the brain (vertebrals and internal carotids).
This circle is formed by the posterior cerebral artery, posterior communicating artery, internal carotid artery, anterior cerebral artery and anterior communicating artery.
Cerebral arterial circle (Circle of Willis)
True or False:
The cerebral artery circle gives rise to numerous small branches to the brain.
True
Venous blood from the superficial and deep veins of the brain, enter the dural venous sinuses which drain into the internal jugular veins. The cerebral veins on the superolateral surface of the brain, drain into the superior sagittal sinus.
Venous Drainage of the Brain
True or False:
Cerebral veins on the posteroinferior aspect drain into the straight, transverse and superior sinuses, along with the superior cerebral veins and transverse sinuses.
True
The total CSF volume is about ______ and is replaced every _______ ; therefore, __________ are formed daily.
150ml
3 to 4 hours
900 - 1200 ml
