Neuroanatomy

Question 0

Temporal lobe-left side

Answer 0

Temporal lobe (left side) understanding speech analysis of speech, monitoring speech, reading & writing, verbal memory, letter recognition.

Question 1

functions of lobes (general)

Answer 1

Frontal Lobe-motor strip location, impulsivity, short term memory, emotion, voluntary movement, social functioning, creativity, expressive language.

Temporal Lobe-hearing, long term memory, verbal and written recognition memory, receptive memory, music, initiation of verbal.

Parietal Lobe-sensory strip location, perception, touch(pain & temperature), ability to draw, reading and writing, calculations.

Occipital-Occipital Lobe perception, vision

Cerebellum coordination, balance, ability to judge distance, muscle tone including the muscles required for speech.

Brain Stem-Connects with the spinal cord, reticular activating system, thalmus, hypothalmus, heart rate and blood pressure, smell and taste, eye movement, appetite, vision, balance

Question 2

Temporal Lobe (right side) functions

Answer 2

Temporal Lobe (right side) Decoding nonverbal patterns, visual decoding, Interpreting and remembering visual information.

Question 3

Parietal Lobe (left side) functions

Answer 3

Parietal Lobe (left side) smooth speech, writing skills, understanding math, reading skills, naming of objects, verbal memory.

Question 4

Parietal Lobe (right side) functions

Answer 4

Parietal Lobe (right side) drawing skills

Question 5

Occipital Lobe (left side) functions

Answer 5

Occipital Lobe (left side) object recognition, visual recognition, reading numbers and letters, memory for written information.
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Question 6

Occipital Lobe (right side) functions

Answer 6

Occipital Lobe (right side) attending to left visual field.
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Question 7

Frontal Lobe (left side) functions

Answer 7

Frontal Lobe (left side) speech control, expressive speech, memory for verbal information.

Question 8

Frontal Lobe (right side) functions

Answer 8

Frontal Lobe (right side) Visual memory

Question 9

Parts of a neuron

Answer 9

Cell body
Axon
Dendrites
Myelin sheath

Question 10

dendrites

Answer 10

dendrites Neuron parts that detect the stimulus

Question 11

cell body

Answer 11

cell body-Neuron part that contains most of the cytoplasm and the nucleus.

Question 12

synapse

Answer 12

synapse-Space between two neurons or between a neuron and an effector. This is where neurotransmitters get released.

Question 13

axon

Answer 13

axon Neuron part that sends an action potential(nerve impulse) away from the cell body

Question 14

axon endings

Answer 14

axon endings Ends of axons that contain vesicles with NTs (neurotransmitter)
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Question 15

myelin sheath

Answer 15

myelin sheath Layer of lipid rich(fatty rich) cells wrapped around the axon to prevent electrolyte (Na+, K+) loss

Question 16

effector

Answer 16

effector A muscle or a gland (respond to stimulus) that receives a message from a motor neuron
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Question 17

nodes of Ranvier

Answer 17

nodes of Ranvier Gaps in myelin

Question 18

Dendrites

Answer 18

Dendrites short branches of a neuron that receives stimuli and conduct impulses to the cell body.

Question 19

Cell Body

Answer 19

Cell Body the center of metabolic activity in a neuron, it is where the nucleus and much of the cytoplasm are located

Question 20

Sensory Neurons

Answer 20

Sensory Neurons carry impulses from outside and inside the body to the brain and spinal cord

Question 21

Motor Neurons

Answer 21

Motor Neurons carry response impulses from the brain and spinal cord to muscles or glands

Question 22

interneurons

Answer 22

interneurons connect sensory neurons and motor neurons and carry impulses between them. They are concentrated in the brain and spinal cord

Question 23

Grey matter vs. white matter

Answer 23

The CNS has two kinds of tissue: grey matter and white matter, Grey matter, which has a pinkish-grey color in the living brain, contains the cell bodies, dendrites and axon terminals of neurons, so it is where all synapses are. White matter is made of axons connecting different parts of grey matter to each

Question 24

Grey matter

Answer 24

Grey matter (or gray matter) (lat. Substantia grisea) is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil (dendrites and myelinated as well as unmyelinated axons), glial cells (astroglia and oligodendrocytes) and capillaries.

Contains numerous cell bodies and relatively few myelinated axons

In living tissue, grey matter actually has a very light grey color with yellowish or pinkish hues, which come from capillary blood vessels and neuronal cell bodies.[2]

Question 25

white matter

Answer 25

consists mostly of glial cells and myelinated axons that transmit signals from one region of the cerebrum to another and between the cerebrum and lower brain centers.
appears pinkish white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries.

Question 26

Grey and white matter- location

Answer 26

White matter forms the bulk of the deep parts of the brain and the superficial parts of the spinal cord. Aggregates of gray matter such as the basal ganglia (caudate nucleus, putamen, globus pallidus, subthalamic nucleus, nucleus accumbens) and brain stem nuclei (red nucleus, substantia nigra, cranial nerve nuclei) are spread within the cerebral white matter.

The cerebellum is structured in a similar manner as the cerebrum, with a superficial mantle of cerebellar cortex, deep cerebellar white matter (called the “arbor vitae”) and aggregates of grey matter surrounded by deep cerebellar white matter (dentate nucleus, globose nucleus, emboliform nucleus, and fastigial nucleus). The fluid-filled cerebral ventricles (lateral ventricles, third ventricle, cerebral aqueduct, fourth ventricle) are also located deep within the cerebral white matter.

Question 27

Cerebellum- overview

Answer 27

cerebellum (“little brain”) is a structure that is located at the back of the brain, underlying the occipital and temporal lobes of the cerebral cortex (Figure 5.1). Although the cerebellum accounts for approximately 10% of the brain’s volume, it contains over 50% of the total number of neurons in the brain.

Question 28

Cerebellum - functions

Answer 28

Modifies the motor commands of the descending pathways to make movements more adaptive and accurate.

Makes postural adjustments in order to maintain balance. Through its input from vestibular receptors and proprioceptors, it modulates commands to motor neurons to compensate for shifts in body position or changes in load upon muscles. Patients with cerebellar damage suffer from balance disorders, and they often develop stereotyped postural strategies to compensate for this problem

coordinate the timing and force of these different muscle groups to produce fluid limb or body movement

Motor learning-adapting and fine-tuning motor programs to make accurate movements through a trial-and-error process

cognitive functions, such as language

Question 29

Cerebellum- gross anatomy

Answer 29

The cerebellum consists of two major parts.

The cerebellar deep nuclei (or cerebellar nuclei) are the sole output structures of the cerebellum.

These nuclei are encased by a highly convoluted sheet of tissue called the cerebellar cortex, which contains almost all of the neurons in the cerebellum. A cross-section through the cerebellum reveals the intricate pattern of folds and fissures that characterize the cerebellar cortex. Like the cerebral cortex, cerebellar gyri are reproducible across individuals and have been identified and named.

Question 30

Cerebellum- lobes and fissures

Answer 30

Divisions of the cerebellum.
Two major fissures running mediolaterally divide the cerebellar cortex into three primary subdivisions.

The posterolateral fissure separates the flocculonodular lobe from the corpus cerebelli, and the primary fissure separates the corpus cerebelli into a posterior lobe and an anterior lobe.

The cerebellum is also divided sagittally into three zones that run from medial to lateral. The vermis (from the Latin word for worm) is located along the midsagittal plane of the cerebellum. Directly lateral to the vermis is the intermediate zone. Finally, the lateral hemispheres are located lateral to the intermediate zone (there are no clear morphological borders between the intermediate zone and the lateral hemisphere that are visible from a gross specimen).

Question 31

Damage to Cerebellum Produces Movement Disorders

Answer 31

Decomposition of movement.
Intention tremor.
Dysdiadochokinesia
Deficits in motor learning.

Question 32

cerebral cortex

Answer 32

cerebral cortex is the outer covering of gray matter over the hemispheres. This is typically 2- 3 mm thick, covering the gyri and sulci.
The neocortex represents the great majority of the cerebral cortex. It has six layers and contains between 10 and 14 billion neurons. The six layers of this part of the cortex are numbered with Roman numerals from superficial to deep. Layer I is the molecular layer, which contains very few neurons; layer II the external granular layer; layer III the external pyramidal layer; layer IV the internal granular layer; layer V the internal pyramidal layer; and layer VI the multiform, or fusiform layer. Each cortical layer contains different neuronal shapes, sizes and density as well as different organizations of nerve fibers.

Question 33

Functional division of cerebral cortex

Answer 33

Functionally, the layers of the cerebral cortex can be divided into three parts. The supragranular layers consist of layers I to III. The supragranular layers are the primary origin and termination of intracortical connections, which are either associational (i.e., with other areas of the same hemisphere), or commissural (i.e., connections to the opposite hemisphere, primarily through the corpus callosum). The supragranular portion of the cortex is highly developed in humans and permits communication between one portion of the cortex and other regions.
The internal granular layer, layer IV, receives thalamocortical connections, especially from the specific thalamic nuclei. This is most prominent in the primary sensory cortices.
The infragranular layers, layers V and VI, primarily connect the cerebral cortex with subcortical regions. These layers are most developed in motor cortical areas. The motor areas have extremely small or non-existent granular layers and are often called “agranular cortex”. Layer V gives rise to all of the principal cortical efferent projections to basal ganglia, brain stem and spinal cord. Layer VI, the multiform or fusiform layer, projects primarily to the thalamus.

Question 34

somatosensory cortex

Answer 34

Primary somatosensory cortex (SI; areas 3,1,2) is located in the post central gyrus. This receives somatotopic input from the VPL and VPM of the thalamus. Histologically, this area would consist of granular cortex. The sensory homunculus includes cortical representation of the body based on the degree of sensory innervation.Damage to the sensory cortex results in decreased sensory thresholds, an inability to discriminate the properties of tactile stimuli or to identify objects by touch

The secondary somatosensory cortex (SII; area 40) is in the lower parietal lobe. This receives connections from the primary sensory cortex and also less specific thalamic nuclei. This responds to sensory stimuli bilaterally, although with much less precision than the primary cortex. Nonetheless, lesions to this area may impair some elements of sensory discrimination.

Question 35

visual cortex

Answer 35

The primary visual cortex (VI; area 17) also called the striate cortex, surrounds the calcarine sulcus. This area has a large granular layer with dense columns of neurons, called ocular dominance columns. Adjacent columns come from the same homonomous portions of the left and right eyes (i.e., portions that detect images from corresponding portions of the visual world). The macula, the most sensitive portion of the center of the retina, is represented at the posterior tip of the occipital lobe. The upper part of the world projects to the lower part of the striate cortex. Lesions of the occipital lobe would cause cortical blindness and difficulty tracking objects.

Question 36

auditory cortex

Answer 36

The primary auditory cortices (AI; area 41) are on the transverse temporal gyri, extending into the lateral fissures. These gyri are situated on the upper part of the superior temporal gyri. There are tonotopic maps for different tones. Unilateral cortical lesions do not effect hearing because of completely bilateral sound representation.

Question 37

primary and secondary motor cortex

Answer 37

The primary motor cortex (MI; area 4) is in the precentral gyrus. This is the origin of most of the corticospinal tract and a large number of cortical bulbar fibers, particularly those controlling motor cranial nerves. This also has projections to the thalamus and basal ganglion. The VL of the thalamus makes significant input to this nucleus and the precentral gyrus also receives significant input from sensory cortical areas as well as from the premotor portions of the cerebral cortex. There is a very well-defined somatotopic organization of the motor cortex and this is the region of cortex from which movements can be generated by the lowest intensity of electrical stimulation. Specific movements tend to be represented (such as elbow flexion) rather than specific muscles. Lesions produce spastic contralateral weakness, which is most prominent in the distal extremities.

The premotor cortex (area 6) is immediately anterior to the motor cortex and has many of the same connections as the motor cortex. However, most of its output is to the motor cortex, with a smaller output to the brain stem and the spinal cord. This region receives input from the sensory association cortex as well as feedback from the basal ganglia via the VA and VL of the thalamus. Electrical stimulation of this area tends to produce more complex movements and at a higher stimulus intensity than the simple movements from MI. Lesions produce less severe weakness but greater spasticity than patients with isolated precentral gyrus lesions.
The supplementary motor area (MII, superiomedial part of area 6) is a part of the premotor cortex that extends onto the medial side of hemisphere. This projects to the primary motor cortex, basal ganglia, thalamus and brain stem and also has connections with the contralateral supplementary motor area. This area becomes active before movement and is felt to be involved in initiation of motion. Lesions of this area can cause inability to initiate motions, called abulia.

Question 38

frontal eye fields in cerebral cortex

Answer 38

The frontal eye fields (inferior area 8) are located just inferior and rostral to the premotor cortex. Activity in this region results in conjugate horizontal eye movement of the eyes away from the stimulus. This receives input from the medial dorsal nucleus of the thalamus as well as other areas of the cerebral cortex. It makes output to the superior colliculus and the PPRF. Lesions of this area initially block voluntary movement away from the side of lesions, although patients will slowly compensate for this deficit.
The occipital eye fields are located in the visual association cortex. This projects to the frontal eye fields as well as to the pontine nuclei to generate smooth pursuit eye movements. Lesions will produce difficulty in fixing on a target and also will produce abnormalities in optokinetic responses.

Question 39

Language cortex

Answer 39

There are areas of particular importance of the cerebral cortex. The receptive language area, Wernicke’s (area 22) area is in the upper temporal lobe, extending back to the supramarginal (area 40) and angular (area 39) gyri. Lesions produce receptive aphasia with problems understanding spoken and written language.
Lesions of the opercular and triangular portions of the inferior frontal gyrus (areas 44 and 45), called Broca’s area in the dominant hemisphere, produce expressive or motor aphasia. These patients have difficulty in generating spoken or written language.
In the nondominant hemisphere, lesions of the regions of the brain that are analogous to Wernicke’s and Broca’s areas affect the ability to understand or to generate inflections of voice, respectively.

Question 40

Prefrontal cortex

Answer 40

The orbitomedial prefrontal cortex is involved in impulse control, personality, reactivity to the surroundings and mood. A particular area, the anterior cingulate gyrus (areas 24 and 25; subcallosal and subgenual regions) appears to be most associated with mood (particularly depression and mania). While laterality is not as well recognized in the prefrontal cortex as it is in language, there does appear to be some laterality, with lesions of the dominant cortex tending to produce depression and, of the nondominant hemisphere tending to produce mania.

The frontal lobes connect to all other cortical regions through association fibers. It receives particularly strong input from limbic cortex, amygdala and septal nuclei, areas involved in emotional responses. Patients with lesions in this area are often referred to as having a changed personality.

Question 41

Brain stem

Answer 41

brainstem is the region of the brain that connects the cerebrum with the spinal cord. It consists of the midbrain, medulla oblongata, and the pons. Motor and sensory neurons travel through the brainstem allowing for the relay of signals between the brain and the spinal cord. The brainstem coordinates motor control signals sent from the brain to the body. The brainstem also controls life supporting autonomic functions of the peripheral nervous system.

Question 42

Brain stem functions

Answer 42

Alertness, arousal, breathing, blood pressure,digestion, heart rate, and other automatic functions

Relays info between peripheral nerves and spinal cords to the other parts of the brain

Question 43

Mid brain

Answer 43

mesencephalon or midbrain is the portion of the brainstem that connects the hindbrain and the forebrain.

Controls responses to sight, eye Mvmt, pupil dilation, body, Mvmt, hearing

The mesencephalon consists of the tectum and tegmentum.

Question 44

medulla oblongata

Answer 44

medulla oblongata is a portion of the hindbrain that controls autonomic functions such as breathing, digestion, heart and blood vessel function, swallowing and sneezing. Motor and sensory neurons from the midbrain and forebrain travel through the medulla. As a part of the brainstem, the medulla oblongata helps in the transferring of messages between various parts of the brain and the spinal cord

The medulla oblongata is involved in several functions of the body including:
Control of Autonomic Functions
Relay of Nerve Signals Between the Brain and Spinal Cord
Coordination of Body Movements

Directionally, the medulla oblongata is inferior to the pons and anterior to the cerebellum.

Question 45

Pons

Answer 45

In Latin, the word pons literally means bridge. The pons is a portion of the hindbrain that connects the cerebral cortex with the medulla oblongata. It also serves as a communications and coordination center between the two hemispheres of the brain. As a part of the brainstem, the pons helps in the transferring of messages between various parts of the brain and the spinal cord.

Functions:Arousal, Controlling Autonomic Functions, Relaying Sensory Information Between the Cerebrum and Cerebellum
Sleep

Directionally, the pons is superior to the medulla oblongata and inferior to the midbrain. Sagittally, it is anterior to the cerebellum and posterior to the pituitary gland.

Question 46

Spinal cord

Answer 46

The spinal cord is composed of nervous tissue. The interior of the spinal cord consists of neurons, nervous system support cells called glia, and blood vessels.

The axons that link the spinal cord to the muscles and the rest of the body are bundled into 31 pairs of spinal nerves, each pair with a sensory root and a motor root that make connections within the grey matter. These nerves must pass between the protective barrier of the spinal column to connect the spinal cord to the rest of the body. The location of the nerves in the spinal cord determine their function.

Question 47

Neuron

Answer 47

Neurons are the basic unit of nervous tissue. They are composed of a cell body and projections that extend from the cell body that are able to conduct and transmit nerve signals. These projections are axons (carry signals away from the cell body) and dendrites (carry signals toward the cell body). The neurons and their dendrites are contained within an H-shaped region of the spinal cord called “grey matter.” Surrounding the grey matter area is a region called “white matter.” The white matter section of the spinal cord contains axons that are covered with an insulating substance called myelin. Myelin is whitish in appearance and allows electrical signals to flow freely and quickly. Axons carry signals along descending and ascending tracts away from and toward the brain

Neurons are classified as either motor, sensory, or interneurons. Motor neurons carry information from the central nervous system to organs, glands, and muscles. Sensory neurons send information to the central nervous system from internal organs or from external stimuli. Interneurons relay signals between motor and sensory neurons. The descending tracts of the spinal cord consist of motor nerves that send signals from the brain to control voluntary and involuntary muscles. They also help to maintain homeostasis by assisting in the regulation of autonomic functions such as heart rate, blood pressure, and internal temperature. The ascending tracts of the spinal cord consist of sensory nerves that send signals from internal organs and external signals from the skin and extremities to the brain. Reflexes and repetitive movements are controlled by spinal cord neuronal circuits that are stimulated by sensory information without input from the brain.

Question 48

Spinal column

Answer 48

spongy spinal cord is protected by the irregular shaped bones of the spinal column called vertebrae. Spinal vertebrae are components of the axial skeleton and each contain an opening that serves as a channel for the spinal cord to pass through. Between the stacked vertebrae are discs of semi-rigid cartilage, and in the narrow spaces between them are passages through which the spinal nerves exit to the rest of the body. These are places where the spinal cord is vulnerable to direct injury.

Question 49

Vertebra of spinal cord

Answer 49

Cervical vertebrae (1-7) located in the neck
Thoracic vertebrae (1-12) in the upper back (attached to the ribcage)
Lumbar vertebrae (1-5) in the lower back
Sacral vertebrae (1-5) in the hip area
Coccygeal vertebrae (1-4 fused) in the tail-bone

Question 50

Spinal nerves

Answer 50

Cervical spinal nerves (C1 to C8) control signals to the back of the head, the neck and shoulders, the arms and hands, and the diaphragm.
Thoracic spinal nerves (T1 to T12) control signals to the chest muscles, some muscles of the back, and parts of the abdomen.
Lumbar spinal nerves (L1 to L5) control signals to the lower parts of the abdomen and the back, the buttocks, some parts of the external genital organs, and parts of the leg.
Sacral spinal nerves (S1 to S5) control signals to the thighs and lower parts of the legs, the feet, most of the external genital organs, and the area around the anus.
The single coccygeal nerve carries sensory information from the skin of the lower back.

Question 51

Meninges

Answer 51

the meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous

Question 52

Dura mater

Answer 52

The dura mater (literally, “tough mother”) is the dense, leathery membrane covering and protecting the brain and spinal cord. The dura mater is a sac (aka thecal sac) that envelops the arachnoid mater. It surrounds and supports the dural sinuses (also called dural venous sinuses, cerebral sinuses, or cranial sinuses) and carries blood from the brain toward the heart. There are many ways the dura can become damaged, including severe head injury, tumor ingrowth (meningioma), or a surgeon’s need to open the dura for access to the brain or spinal cord during invasive surgical procedures.

The two layers of dura mater run together throughout most of the skull. Where they separate, the gap between them is called a dural venous sinus. These sinuses drain blood and cerebrospinal fluid from the brain and empty into the internal jugular vein.

Question 53

Arachnoid mater

Answer 53

It is interposed between the two other meninges, the more superficial and much thicker dura mater and the deeper pia mater, from which it is separated by the subarachnoid space. The delicate arachnoid layer is attached to the inside of the dura and surrounds the brain and spinal cord. It does not line the brain down into its sulci (folds), as does the pia mater, with the exception of the longitudinal fissure, which divides the left and right cerebral hemispheres. Cerebrospinal fluid (CSF) flows under the arachnoid in the subarachnoid space. The arachnoid mater makes arachnoid villi, small protrusions through the dura mater into the venous sinuses of the brain, which allow CSF to exit the subarachnoid space and enter the blood stream

Question 54

corpus callosum

Answer 54

The corpus callosum is a thick band of nerve fibers that divides the cerebrum into left and right hemispheres. It connects the left and right sides of the brain allowing for communication between both hemispheres. The corpus callosum transfers motor, sensory, and cognitive information between the brain hemispheres.

Functions: Communication Between Brain Hemispheres, Eye Movement, Maintaining the Balance of Arousal and Attention, Tactile Localization

Directionally, the corpus callosum is located underneath the cerebrum at the center of the brain.

Question 55

hippocampus

Answer 55

hippocampus is the part of the brain that is involved in memory forming, organizing, and storing. It is a limbic system structure that is particularly important in forming new memories and connecting emotions and senses, such as smell and sound, to memories. The hippocampus is a horseshoe shaped paired structure, with one hippocampus located in the left brain hemisphere and the other in the right hemisphere. The hippocampus acts as a memory indexer by sending memories out to the appropriate part of the cerebral hemisphere for long-term storage and retrieving them when necessary.

Functions: Consolidation of New Memories, Emotional Responses
Navigation, Spatial Orientation

Directionally, the hippocampus is located within the temporal lobes, adjacent to the amygdala.

Question 56

thalamus

Answer 56

The thalamus is a large, dual lobed mass of grey matter buried under the cerebral cortex. It is involved in sensory perception and regulation of motor functions. The thalamus is a limbic system structure and it connects areas of the cerebral cortex that are involved in sensory perception and movement with other parts of the brain and spinal cord that also have a role in sensation and movement. As a regulator of sensory information, the thalamus also controls sleep and awake states of consciousness.

Functions: Motor Control, Receives Auditory, Somatosensory and Visual Sensory Signals, Relays Sensory Signals to the Cerebral Cortex
Controls Sleep and Awake States

Question 57

What is CSF and where is it found”

Answer 57

Cerebrospinal fluid (CSF) is a clear colorless bodily fluid found in the brain and spine. It is produced in the choroid plexus of the brain. It acts as a cushion or buffer for the brain’s cortex, providing a basic mechanical and immunological protection to the brain inside the skull, and it serves a vital function in cerebral autoregulation of cerebral blood flow.

The CSF occupies the subarachnoid space (the space between the arachnoid mater and the pia mater) and the ventricular system around and inside the brain and spinal cord. It constitutes the content of the ventricles, cisterns, and sulci of the brain, as well as the central canal of the spinal cord

Question 58

Where is CSF produced?

Answer 58

The brain produces roughly 500 mL of cerebrospinal fluid per day. This fluid is constantly reabsorbed, so that only 100-160 mL is present at any one time.

Ependymal cells of the choroid plexus produce more than two thirds of CSF. The choroid plexus is a venous plexus contained within the four ventricles of the brain, hollow structures inside the brain filled with CSF. The remainder of the CSF is produced by the surfaces of the ventricles and by the lining surrounding the subarachnoid space.

Question 59

How is CSF produced?

Answer 59

Ependymal cells actively secrete sodium into the lateral ventricles. This creates osmotic pressure and draws water into the CSF space. Chloride, with a negative charge, maintains electroneutrality and moves with the positively-charged sodium. As a result, CSF contains a higher concentration of sodium and chloride than blood plasma, but less potassium, calcium and glucose and protein.[2]:519–520 [1]:764

Question 60

How does CSF circulate thru the brain?

Answer 60

CSF circulates within the ventricular system of the brain. The ventricles are a series of cavities filled with CSF that reside within the brain. The majority of CSF is produced from within the two lateral ventricles. From here, the CSF passes through the Interventricular foramina (of Monro) to the third ventricle, then the cerebral aqueduct (of Sylvius) to the fourth ventricle. The fourth ventricle is an outpouching on the posterior part of the brainstem. From the fourth ventricle, the fluid passes through three foramen to enter the subarachnoid space. It passes through the Foramen of Magendie on the midline, and two Foramen of Luschka laterally. The subarachnoid space covers the brain and spinal cord.

The CSF moves in a pulsatile manner throughout the CSF system with nearly zero net flow.[citation needed]

Question 61

How is CSF reabsorbed or return to the brain?

Answer 61

It had been thought that CSF returns to the vascular system by entering the dural venous sinuses via the arachnoid granulations (or villi). However, some[3] have suggested that CSF flow along the cranial nerves and spinal nerve roots allow it into the lymphatic channels; this flow may play a substantial role in CSF reabsorbtion, in particular in the neonate, in which arachnoid granulations are sparsely distributed. The flow of CSF to the nasal submucosal lymphatic channels through the cribriform plate seems to be especially important.[4]

Question 62

What is CSF made of?

Answer 62

The CSF contains approximately 0.3% plasma proteins, or approximately 15 to 40 mg/dL, depending on sampling site,[5] and it is produced at a rate of 500 ml/day. Since the subarachnoid space around the brain and spinal cord can contain only 135 to 150 ml, large amounts are drained primarily into the blood through arachnoid granulations in the superior sagittal sinus. Thus the CSF turns over about 3.7 times a day. This continuous flow into the venous system dilutes the concentration of larger, lipid-insoluble molecules penetrating the brain and CSF.[6]

Question 63

What is CSF pressure?

Answer 63

CSF pressure, as measured by lumbar puncture (LP), is 10-18 cmH2O (8-15 mmHg or 1.1-2 kPa) with the patient lying on the side and 20-30cmH2O (16-24 mmHg or 2.1-3.2 kPa) with the patient sitting up.[7] In newborns, CSF pressure ranges from 8 to 10 cmH2O (4.4–7.3 mmHg or 0.78–0.98 kPa). Most variations are due to coughing or internal compression of jugular veins in the neck. When lying down, the cerebrospinal fluid as estimated by lumbar puncture is similar to the intracranial pressure.

Question 64

What is the function of CSF?

Answer 64

CSF serves several purposes:

1. Protection from brain injury
2. Buoyancy- the net weight of the brain is suspended in CSF
3. Chemical stability
4. Prevents brain ischemia
5. Clearing waste

Question 65

What is the circle of Willis?

Answer 65

The Circle of Willis is a part of the cerebral circulation and is composed of the following arteries:[2]

Anterior cerebral artery (left and right)
Anterior communicating artery
Internal carotid artery (left and right)
Posterior cerebral artery (left and right)
Posterior communicating artery (left and right)
The basilar artery and middle cerebral arteries, supplying the brain, are not considered part of the circle.

Question 66

What is the anterior cerebral artery (ACA)?

Answer 66

The anterior cerebral artery (ACA) is one of a pair of arteries on the brain that supplies oxygenated blood to most medial portions of the frontal lobes and superior medial parietal lobes. The two anterior cerebral arteries arise from the internal carotid artery and are part of the Circle of Willis.

The left and right anterior cerebral arteries are connected by the anterior communicating artery.

Question 67

What is the function of anterior cerebral artery?

Answer 67

Areas supplied by the anterior cerebral artery include:

The medial surface of the frontal lobe by the medial orbito-frontal artery, and parietal lobes
The anterior four- fifths of the corpus callosum
Approximately 1 inch of the lateral surfaces of frontal and parietal lobes, next to the medial longitudinal fissure
Anterior portions of the basal ganglia and internal capsule
Olfactory bulb and tract

Question 68

Symptoms of occlusion of Anterior cerebral artery

Answer 68

Paralysis or weakness of the contralateral foot and leg due to involvement of Motor leg area
Cortical Sensory loss in the contralateral foot and leg
Gait apraxia Impairment of gait and stance
Abulia akinetic mutism, slowness and lack of spontaneity
Urinary incontinence which usually occurs with bilateral damage in the acute phase
Frontal Cortical release reflexes: Contralateral grasp reflex, sucking reflex, gegenhalten(paratonic rigidity)

Question 69

Anterior communicating artery

Answer 69

The anterior communicating artery connects the two anterior cerebral arteries across the commencement of the longitudinal fissure. Sometimes this vessel is wanting, the two arteries joining together to form a single trunk, which afterward divides; or it may be wholly, or partially, divided into two. Its length averages about 4 mm, but varies greatly. It gives off some of the anteromedial ganglionic vessels, but these are principally derived from the anterior cerebral artery.

Question 70

Aneurysms of the anterior communicating artery

Answer 70

Aneurysms of the anterior communicating artery are the most common circle of Willis aneurysm[1] and can cause visual field defects such as bitemporal hemianopsia,[2] psychopathology and frontal lobe pathology.[3]

Question 71

internal carotid artery

Answer 71

The internal carotid artery is major paired artery, one on each side of the head and neck, in human anatomy. They arise from the common carotid arteries where these bifurcate into the internal and external carotid arteries; the internal carotid artery supplies the brain, while the external carotid nourishes other portions of the head, such as face, scalp, skull, and meninges.

Question 72

posterior cerebral artery (PCA)

Answer 72

posterior cerebral artery (PCA) is one of a pair of blood vessels that supply oxygenated blood to the posterior aspect of the brain (occipital lobe) in human anatomy. It arises near the intersection of the posterior communicating artery and the basilar artery and connects with the ipsilateral middle cerebral artery (MCA) and internal carotid artery via the posterior communicating artery (PCommA).

Question 73

Stroke- Pca

Answer 73

Stroke
Contralateral loss of pain and temperature sensations.
Visual field defects (contralateral hemianopia with macular sparing).
Prosopagnosia with bilateral obstruction of the lingual and fusiform gyri.
Superior Alternating Syndrome (Weber’s syndrome)
Contralateral deficits of facial nerve (only lower face, upper face receives bilateral input), vagus nerve and hypoglossal nerve
Ipsilateral deficit of oculomotor nerve
Horner’s Syndrome
Signs and symptoms:Structures involved