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Anatomy and Physiology 1 Test #4 . Dr. Sturges. By Ian A
Terms in this set (90)
are always SENSORY - carry sensory information up the spinal cord towards the brain
from receptors. Ex: fasciculus gracilis and cuneatus, spinothalamic, spinocerebellar (names generally start with
are always MOTOR - conduct motor impulses down the spinal cord from the brain
towards effectors. Ex: corticospinal, rubrospinal, tectospinal (names end in -"spinal")
which means that the axons will cross to the opposite side, right to left and
left to right. As a result, right side of brain controls movement on left side of body and sensory perception on
left side of body; left side of the brain controls movement on the right side of the body and sensory perception
on the right side.
- between the spinal cord and intervertebral foramina. Have two roots:
Dorsal and ventral roots will merge into the trunk of spinal nerve that will exit the spinal cord through the
Posterior (dorsal) root
- passes posteriorly through the intervertebral foramen towards the back of the spinal
cord and enters the posterior horn. Consists of SENSORY fibers (axons) only. Has the posterior (dorsal) root
ganglion, a thickening which contains the somas of the afferent sensory neurons (these neurons are sensory
unipolar) and is part of PNS. Sensory fibers are also known as afferent fibers.
Anterior (ventral) root
- passes anteriorly toward the front on the spinal cord from the ventral horn of the
spinal cord; has no ganglion. Consists of MOTOR fibers (axons) only. Motor fibers are also known as efferent
part of the spinal nerve AFTER passing through the intervertebral foramen. Divides into rami
(ramus for singular)
Anterior Ramus Innervation
supply the anterior and lateral skin, muscles of the trunk and some form the
Posterior Ramus Innervation
supply the muscles and joints in that local area of the spine and the skin of the
nerves formed by junction of dorsal and ventral roots that innervate the body below the head. There
are 31 pairs and they are all MIXED because they have both sensory and motor fibers.
a collection of axons/nerve fibers found in the PNS.
Define the term reflex
Quick, involuntary, stereotyped reaction of effectors (muscles and glands) to stimulation. This means that ALL
reflexes will require a stimulus, will happen quickly, will be involuntary and happen in the same manner every time
The components in sequence are
2) sensory/afferent neuron
3) integration center
4) motor/efferent neuron
-a specialized structure able to detect a stimulus/signal (can be dendrites of sensory neurons)
- its fibers/axons carry sensory input thru the dorsal root to the dorsal horn of the spinal cord. Usually are the unipolar neurons of the dorsal root ganglion.
- always located in the CNS (brain or spinal cord). Integrates the information and makes
- its fibers carry the motor output from ventral horn through the ventral root to target
organs. Mostly in ventral horns.
- carries out the command (glands secrete, muscles contract, etc.)
Intrinsic (inborn) vs. acquired (learned)
- intrinsic are reflexes we are born with for primitive protection. A baby
will close its eyes when a bright light is introduced, but would not have an acquired reflex to know how to ride a
Somatic vs. visceral
- somatic reflexes involve skeletal muscles (stretch reflex), while
- visceral reflexes deal with
internal organs (blood pressure regulation through baroreceptors)
Monosynaptic vs. polysynaptic
- monosynaptic reflexes have one neural synapse in the reflex arc (stretch
reflex). This is commonly between a primary sensory neuron and a motor neuron. No interneurons are involved,
which makes them faster than polysynaptic.
- Polysynaptic reflexes on the other hand have two or more synapses in
the CNS between three or more neurons in a pathway. Interneurons are involved, so it is slower than the
Ipsilateral vs. contralateral
- ipsilateral reflexes are those where the sensory input and the motor output are on
the same side of the body (the withdrawal reflex).
- Contralateral reflexes are those that have a sensory input on
one side of the body and the motor output is sent to the opposite side of the body (the crossed extensor reflex).
Spinal vs cranial
- in spinal reflexes, the decision (neural integration) is made in spinal cord, involves spinal
nerves (stretch reflex).
- In cranial reflexes - decision (neural integration) is made in the brain, involves cranial
Stretch reflex (patellar reflex, knee jerk)
- helps maintain equilibrium and posture. Is monosynaptic and ipsilateral. Depends on muscle spindles to send the sensory signal about the stretch of the muscle. As the muscle gets stretched, it contracts in response. Maintains increased tonus and feeling stiffer than an unstretched muscle.
Flexor (withdrawal) reflex
this is a quick contraction of flexor muscles which results in retracting or withdrawing the limb from a possibly dangerous stimulus (stepping on glass). Is polysynaptic and ipsilateral.
o Pain receptors send a message from the site of injury to the spinal cord through sensory neurons activating interneurons. Interneurons signal the motor neurons. Motor neurons excite the flexor muscle to contract and withdraw the limb.
- contraction of extensor muscles in the opposite limb from the one being withdrawn. Is
polysynaptic and contralateral.
o Pain receptors send a message from the site of injury to the spinal cord through sensory neurons. Sensory nerve fibers cross from the injured (stimulated) side of the body to the contralateral side of the spinal cord. Here they synapse with interneurons that signal the motor neurons. Motor neurons excite the extensor muscles in the opposite limb to the one being injured/withdrawn.
- is commonly known as a knee-jerk reflex and is an example of a stretch reflex. When a physician strikes
the patellar ligament (it connects the patella to the tibia and is the continuation of the patellar tendon, which attaches the quad muscle to the patella) with a hammer, it stretches the quad muscle. Stretch is detected by muscle spindles and is carried by the sensory fibers in the femoral nerve to the dorsal horn of spinal cord (L4). In the spinal cord, the sensory fiber synapses with a motor neuron directly (monosynaptic reflex). The motor neuron then sends the motor output to the quadriceps muscle on the same side (ipsilateral), which contracts in response and extends the knee (jerks the knee
upward). The quad muscle is an extensor muscle.
Propose how specific reflexes would be used in clinical assessment of nervous system function
Reflexes can be used to test specific muscle groups and specific spinal nerves.
Positive result on stretch reflexes (for posture) indicate:s
1. The sensory and motor connection between the muscle and SC is intact
2. Strength of response indicates degree of excitability of SC by impulses descending from higher centers
Consistently abnormal reflexes can indicate damage to the nervous system or muscles, as reflexes can be normal,
hypoactive, or hyperactive.
Hypoactive/absent: in peripheral nerve damage, chronic diabetes mellitus, coma, neurosyphilis
Hyperactive: in lesions of corticospinal tract.
There are three neurons found in the ascending tracts that carry sensory signals to the CNS.
1) First-order neurons are found in the dorsal root ganglion (unipolar): they detect stimuli and forward it to the spinal cord or brainstem.
2) Second-order neurons are mostly found in the dorsal horns: they forward the signal on to the thalamus of diencephalon
3) Third-order neurons are found in the thalamus: they carry the signal the rest of the way to the cerebral cortex's sensory region (ex: post-central gyrus/sensory homunculus for touch, pressure, pain, etc.)
The correct sequence for information processing in ascending tracts is: receptor for general senses-first order sensory neuron in dorsal root ganglion-second order sensory neuron in dorsal horn (mostly)-third order neuron in thalamus-postcentral
gyrus of parietal lobe.
= loss of sensory function (can be partial or complete), inability to feel. Sensory input is conducted to the spinal cord via the dorsal root, so any damage to the dorsal root ONLY will cause loss of sensory function ONLY (the ability to conduct sensory input to the spinal cord and then the brain for interpretation will be affected), but maintain the
ability to contract muscles (intact motor output). Symptoms of sensory loss: tingling, numbing, etc.
Remember that damage to any part of an ascending tract will lead to paresthesia. That includes damage to receptors, parts of brain that interpret sensory information like postcentral gyrus or dorsal horn damage in spinal cord.
Upper motor neurons
: the starting place of efferent (motor) signals, like the neurons of the corticospinal tract.
Most are located in the cerebral cortex (precentral gyrus) and have a long axon that synapses on a lower motor
Lower motor neurons
: the starting place of axons that synapse on the effector (skeletal muscle). Most are located
in ventral horns of spinal cord.
The correct sequence for information processing in descending tracts is: upper motor neuron in precentral gyrus of frontal lobe (mostly)-lower motor neuron in ventral horns (mostly)-effectors (skeletal muscle).
= loss of motor function (can be partial or complete), inability to contract skeletal muscles. Motor output is carried to the effectors (skeletal muscles) via the ventral root from the motor neurons of the ventral horn. Damage to the
ventral root ONLY will result in loss of motor function ONLY (inability to contract the muscles, but maintain the ability to feel (sensory input is intact)). Symptoms of motor loss: no movement (can be paraplegia or quadriplegia).
Remember that damage to any part of a descending tract will lead to paralysis. That includes damage to precentral gyrus in the brain, parts of brain that conduct descending tracts (like pons and medulla), or ventral horn damage in spinal cord.
If we damaged the spinal nerve AFTER it exits the intervertebral foramen, we would have a loss of both sensory and motor function, since spinal nerves are mixed.
- the crossing over of fibers/axons in the tracts from one side to another. This occurs in ascending
and descending tracts.
Because of decussation:
The left side of the brain receives sensory information from the right side of the body; the right side of the brain receives sensory information from the left side of the body. Sensory information for general senses is interpreted in postcentral gyrus of parietal lobe.
The left side of the brain controls the right side of the body; the right side of the brain controls the left side of the body. Motor information for skeletal muscle contraction begings in precentral gyrus of frontal lobe.
a. In strokes, if damage happens on the right side of the brain: patients cannot "feel" on the left side of the body=paresthesia and cannot move=paralysis the left side of the body.
b. In strokes, if damage happens on the left side of the brain: patients cannot "feel" on the right side of the body=paresthesia and cannot move=paralysis the right side of the body
Spinal cord is part of CNS and is protected by bone in the vertebral canal. Has three functions:
Decision making in spinal reflexes (such as the withdrawal reflex)
Sensory input - carrying sensory information up, through ascending tracts from receptors to the brain.
Motor output (controls motor responses) - carrying motor information down, through descending tracts from the brain to
contains somas, dendrites, and synapses. Little myelin=grey in color. Site of information
processing=neural integration. Found in nuclei, cortex, and ganglia.
contains nerve fibers (axons) that can be sensory or motor. Abundance of myelin=white in color.
Carry signals from one part of the CNS to another=conduction/communication. Found in columns and tracts.
List the regions of the brain and their components
Cerebrum - newest and largest part of the brain (83% of the brains volume), most rostral part of brain composed of the right and left cerebral hemispheres, separated by the longitudinal fissure. Each cerebral hemisphere houses one lateral ventricle. Responsible for higher brain functions like reasoning, speech, logic, etc.
Cerebellum (little brain) - the second largest region of the brain; is found caudal to the cerebrum.
Diencephalon - houses the hypothalamus, thalamus, epithalamus and the 3rd ventricle.
Brainstem is the oldest, most primitive part of the brain, consists of midbrain, pons, and medulla oblongata (listed from the most rostral to the most caudal)
Describe the orientation of the brain relative to bones of the skull, including directional terms such as caudal and rostral
The brain as a whole is located deep to the frontal, parietal, temporal and occipital bones of the skull. The brain is subdivided into lobes based on the bones of the skull that overlap these parts of the brain and carry the names of the associated bones. Two directional terms are used in identifying the position of different parts of the brain (rostral=closer to the forehead and caudal=closer to cauda equine)
Describe the relationship between different components of the brain, using directional terms such as caudal and rostral
(Practice assignment 1 on the brain worksheet)
Medulla oblongata is rostral to the spinal cord and caudal to the pons
Pons is rostral to medulla oblongata and spinal cord and caudal to mesencephalon, diencephalon, cerebrum
Mesencephalon is rostral to pons, medulla and spinal cord, but caudal to diencephalon and cerebrum
Diencephalon is rostral to mesencephalon, pons, medulla and spinal cord and caudal to cerebrum
Cerebrum is rostral to all other structures of the brain
Contrast the relative position of gray matter and white matter in the spinal cord with the corresponding arrangement of
gray and white matter in the brain.
Spinal cord: gray matter is located in the center of the spinal cord and is deep to the white matter.
Brain: gray matter is located in the center, surrounded by white matter, but then there is an additional layer of gray matter (cortex) superficial to the white matter. The brain also has collections of gray matter (nuclei) within its white matter.
- an external layer of gray matter (somas of neurons) in the brain, newest part of the brain
- a collection of gray matter (somas of neurons) usually located within the white matter, in CNS. Ex:
basal nuclei, nuclei of cranial nerves
shallow groove (central sulcus, lateral sulcus, posterior median sulcus)
- groove, deeper than a sulcus (longitudinal fissure, anterior median fissure)
- a "bump" on the surface of the brain (precentral or postcentral gyrus)
- part of the brain underlying a cranial bone (frontal, parietal, occipital and temporal lobes)
- prominent landmark, vertical groove, separates the frontal lobe from the parietal lobe
- prominent landmark (also called Sylvian fissure or lateral fissure), horizontal grove, separates
frontal and parietal lobes from temporal lobe.
- deep longitudinal groove separating the two cerebral hemispheres from one another on the
surface of the brain. Has falx cerebri in it.
- the "bump" rostral to the central sulcus. Primary motor area (beginning of the corticospinal
tract). Motor homunculus.
- the "bump" caudal to the central sulcus. Primary (somato) sensory area for general senses and
taste. Sensory homunculus.
- located rostral to the central sulcus and is the part of the brain located under the frontal bone. Has
the precentral gyrus = primary motor area. Neurons in this gyrus form the motor homunculus and regulate movement of different muscle groups of the body. On the left, has Broca's area that is responsible for producing speech. Functions: movement, speech, decision making and personality.
-located caudal to the frontal lobe and to the central sulcus and is the part of the brain located under the parietal bone. Has the postcentral gyrus =primary somatosensory area of the brain. Neurons in this gyrus from the sensory homunculus and are responsible for sensory perceptions of all general senses (like touch and temperature, etc.) plus one special sense-taste. On the left, has part of Wernicke's area that interprets speech. Functions: sensory interpretation.
- found caudal to the parietal lobe. Function: visual processing.
- the most inferior lobe, inferior to the lateral sulcus. Functions: hearing and memory.
- small mass of cortex deep to the lateral sulcus and can only be found by retracting the cerebrum
covering it. Less is known about its function because of its location.
is found in the postcentral gyrus of the parietal lobe. It is the primary somatoSENSORY area
of the brain and represents a map of the body, where different parts of the body are projected in different places within this map. Parts of the body that have more sensitivity (like the face) have larger areas of projections, since they require more neurons to process information.
is found in precentral gyrus of frontal lobe. It is the primary MOTOR area of the brain and represents a map of the body, where each neuron is responsible for moving a certain part of the body. Parts of the body that have fine movements will have larger areas on motor homunculus, since one motor neuron will innervate less skeletal muscle fibers.
Knowing each map can help diagnose possible brain damage locations from the lack of motor or sensory
For ex: damage to the entire left precentral gyrus will result in paralysis on the right side of the body;
damage to the entire right precentral gyrus will result in paralysis on the left side of the body.
Similarly, damage to the entire left postcentral gyrus will result in loss of sensory function on the right side of the body; damage to the entire right postcentral gyrus results in loss of sensory function on the left side of the body.
Cerebral hemispheric lateralization
- each hemisphere is specialized in how information is processed, but both work together.
- LEFT hemisphere: speech and written language, the sequential and analytical reasoning, science
and math; it breaks information into fragments and analyzes it linearly
- RIGHT hemisphere; imagination, insight, musical and artistic skill, perception of patterns and
spatial relationships, comparison of sights, sounds, smells, and tastes, analyses information holistically.
Corpus callosum (white matter)
- is a large fiber tract (millions of axons) located deep in the longitudinal fissure; it is a commissural tract as it connects the left and right hemispheres of the cerebrum and allows the left side to knows what the right side is doing = interhemispheric communication.
Functionally, the cortex has three types of areas:
Motor - areas responsible for motor output (ex: muscle contraction). Primary motor area is the precentral gyrus (beginning of the corticospinal tract) of frontal lobe aka motor homunculus. When neurons in these areas fire, certain groups of muscles can contract.
Sensory - areas responsible for interpreting the sensory input (ex: touch). Primary somatosensory area is the postcentral gyrus of parietal lobe aka sensory homunculus. Neurons in these areas allow us to feel pain, temperature changes, touch, etc.
Association - areas that help primary areas achieve their goal. Ex: occipital lobe interprets visual information (information coming from the eyes), but the association area in the occipital lobe helps us identify what we see. If we look at letter "A", association area helps us identify it as letter "A" and not "C" or "B".
- areas responsible for motor output (ex: muscle contraction). Primary motor area is the precentral gyrus (beginning of the corticospinal tract) of frontal lobe aka motor homunculus. When neurons in these areas fire, certain groups of muscles can contract.
- areas responsible for interpreting the sensory input (ex: touch). Primary somatosensory area is the postcentral gyrus of parietal lobe aka sensory homunculus. Neurons in these areas allow us to feel pain, temperature changes, touch, etc.
- areas that help primary areas achieve their goal. Ex: occipital lobe interprets visual information (information coming from the eyes), but the association area in the occipital lobe helps us identify what we see. If we look at letter "A", association area helps us identify it as letter "A" and not "C" or "B".
Describe the location and functions of the medulla oblongata
Located in the brainstem caudal to the pons and rostral to the spinal cord, 3-4 cm long
Forms part of the floor of the 4th ventricle
Has the pyramids=a place where the corticospinal tracts decussate
Has the respiratory center = involuntary control of breathing
Has the cardiac center= controls heart rate and strength of heart contraction
Has vasomotor center=control of blood vessels (blood pressure regulation)
Has nuclei of the last 4 cranial nerves (XII, XI, X, IX)
The medulla oblongata is suppressed by depressant drugs
Describe the location and functions of the Pons
It is located rostral to the medulla oblongata and caudally to the mesencephalon
Forms part of the floor of the 4th ventricle
Consists of thick stalks called the cerebellar peduncles that connect the pons to the cerebellum
Most important function is to be a bridge and allow ascending and descending tracts to travel up and down
Has nuclei of the 4 cranial nerves (VIII, VII, VI, V)
Important regulator of sleep and the REM cycle, arousal, controlling autonomic functions, and relaying sensory
information between the cerebrum and cerebellum
Describe the location and functions of the Midbrain
Located rostral to the pons and caudal to the diencephalon
Contains the cerebral peduncles anterior (house the corticospinal tracts), tegmentum (communication with cerebellum for fine motor control), and the tectum posterior (with corpora quadrigeminna).
- corpora quadrigemina consist of four bulges: the upper pair called the superior colliculi and the lower pair called the inferior colliculi
Has a channel in the center called cerebral aqueduct surrounded by the periaqueductal gray matter. The cerebral aqueduct connects the 3rd ventricle with the 4th ventricle.
Involved in fine motor control through the black substance=substantia nigra. Lack of dopamine here causes Parkinson's disease.
Involved in vision and eye movement (cranial nerve III and IV)
Describe the location and functions of the diencephalon
Located rostral to the midbrain and caudal to the cerebrum
Forms the walls and floor of the 3rd ventricle
Has 3 parts with different functions
-Epithalamus - contains pineal gland to secrete melatonin (sleep regulation, more melatonin makes you sleepy)
-Thalamus - is a collection of gray matter (nuclei), a sensory gateway to the cortex of the brain=post-office of the brain. Has the last (third order) neuron of sensory tracts. Most sensory signals pass through the thalamus before reaching final destinations in the brain (postcentral gyrus).
-Hypothalamus - a neuroendocrine organ; main visceral (autonomic) control center-controls heart rate, blood pressure, GI tract movement; regulates the endocrine system, as it produces hormones that control the pituitary gland, but also makes its own hormones such as ADH and oxytocin; responsible for thirst, hunger, temperature regulation (our thermostat) and emotions (rage, pleasure) since it is part of the limbic system.
Describe the location and functions of the cerebellum
The cerebellum is located caudal to the cerebrum and has its own two cerebellar hemispheres separated by the vermis
Forms the roof of the 4th ventricle
Has anterior and posterior lobes
Has an external layer of gray matter known as the folia (wrinkles on the surface)
Has an inner layer of white matter resembling a tree called arbor vitae
Cerebellum receives signals from the motor cortex and sensory receptors, coordinates force, direction and the extent of muscle contraction strength; it compares intentions with the physical output, and maintains posture.
Cerebellum is connected to the brainstem through cerebellar peduncles and tegmentum
Major part in coordinating movement, necessary in riding a surfboard
Describe the location and functions of the limbic system
It is a functional system in the brain as it consists of multiple components that are part of other structures of the
brain, but all carry out a similar function
Some components are: the amygdala, basal nuclei, fornix, mammillary body, cingulate gyrus, and the hippocampus
It is the emotional brain: feeling sad for our friends' sickness
Associates different smells with different memories
Involved in memory, emotions
Describe the location and functions of the reticular activating system
Aka reticular formation
It is a functional system of the brain: it consists of a group of neurons scattered all throughout the brainstem. The pathway begins in the medulla, extends into the pons, through the midbrain and sends "projections" to the cortex
Receives input from most sensory systems and keeps the cortex alert; as such, one of its functions is to determine the general level of arousal (consciousness)
Responsible for habituation (ability to block out erroneous signals and filter sensory information )
It is inhibited by alcohol and sleep-inducing drugs or traumas to brainstem
Disorders of the RAS is called ADHD with an inability to focus on certain activities for long times. Treated with Adderall that arouses, stimulates the brain and can lead to serious adverse effects like insomnia and dependence
Describe how the bones of the skull protect the brain
The intricate overlapping of the bones of the skull forming sutures (synarthroses) provides the best protection for the delicate tissue forming the brain, while the vertebral column encases the spinal cord.
List the meninges of the brain and spinal cord and identify the outer, middle and inner layer
Both the brain and spinal cord have three meninges: dura mater (most external), arachnoid mater (middle), and pia mater (most internal).
They work together to protect the nervous tissue, blood vessels and enclose venous sinuses (to drain blood with waste), contain the CSF and form partitions in the skull
In the brain, Dura is a double layer membrane. The outer layer called periosteal layer is attached to the inner surface of bones of the skull; the inner layer called meningeal layer forms partitions to separate parts of the brain. For ex: the meningeal layer forms the falx cerebri located in the longitudinal fissure that separates the two cerebral hemispheres from one another. The two layers form irregular spaces between, called sinuses (ex: superior sagittal sinus, but there are many other sinuses). They are used to drain venous blood. In the brain there is no space between the periosteal layer of the Dura and the bones of the skull.
In the spinal cord, Dura is a single layer that forms the Dural sheath (a sock-like structure surrounding the spinal cord). In the spinal cord, there is a space between the Dura and the vertebrae (vertebral canal). This space, the EPIDURAL space, is filled with adipose tissue, is well vascularized and is used for epidural anesthesia.
- loose spider web-like lining of Dura mater, similar in brain and spinal cord. Participates in forming the subarachnoid space.
Has arachnoid villi - projections that protrude through the Dura into the superior sagittal sinus and allow the Allow the subarachnoid space to return of CSF into circulatory system.
They are crucial structures in drainage of CSF.
Pia mater-most internal
- a highly vascularized, very delicate layer that clings tightly to the brain and spinal cord. It forms the denticulate ligaments along the length of the spinal cord (attaching the spinal cord to vertebral column),
as well as the filum terminale (a ligament that anchors the spinal cord to coccyx).
List and identify the location of hollow structures in the brain (ventricles) and spinal cord (central canal).
The brain has four major hollow structures called ventricles that are filled with CSF: they communicate with each other, with the space in the spinal cord and the subarachnoid space.
Lateral ventricles (two) - each located in one cerebral hemisphere
3rd ventricle - formed by the diencephalon
4th ventricle - floor formed by medulla and pons and roof formed by cerebellum
Central canal - in the center of gray commissure of the spinal cord
Subarachnoid space - space between the arachnoid and the pia, filled with CSF that bathes the brain and spinal cord
Define the term cerebrospinal fluid (CSF) and list some of its component
- It is a clear colorless bodily fluid filling the spaces of the brain and spinal cord. It is produced in the choroid plexus located in the ventricles of the brain and it's a filtrate of blood. CSF has more Na and Cl, and less K, Ca, proteins and glucose than blood plasma.
Buoyancy - allows the brain to "feel" lighter in weight and protects from damage
Protection - prevents the brain from striking the skull in a blow to the head (not absolute protection)
Chemical stability -regulates the chemical environment.
Describe the production and circulation of the cerebrospinal fluid within the central nervous system (include choroid plexus, lateral ventricles, 3rd and 4th ventricle, interventricular foramina, cerebral aqueduct, lateral and median apertures)
Produced - about 500ml/day, about 2/3rds from the choroid plexuses and the rest from ependymal lining of the brain ventricles and the subarachnoid space. CSF continually flows through the openings in CNS (ventricles in brain and central canal in spinal cord) and around CNS, but only about 150 ml of CSF fills the ventricles and central canal of spinal cord at any given moment, since CSF is reabsorbed (drained) constantly with the help of arachnoid villi. If reabsorption is affected, hydrocephalus can develop.
CSF starts its production in the lateral ventricles (located in each cerebral hemisphere), passes through the interventricular foramen into the 3rd ventricle (located in diencephalon) which adds more CSF. It then flows through the cerebral aqueduct (located in mesencephalon) into the 4th ventricle (formed by pons, medulla and cerebellum). The 4th ventricle adds more CSF. From the 4th ventricle, a part of CSF passes into the central canal of the spinal cord, but most passes through the median and lateral apertures into the subarachnoid space. With the help of arachnoid villi, it drains from the subarachnoid space into the superior sagittal sinus of the brain and is returned into blood circulation.
Practice assignment 4 from brain worksheet
Discuss the role of arachnoid villi in the reabsorption of the CSF
Arachnoid villi protrude into the superior sagittal sinus and drain the CSF from the subarachnoid space back into blood circulation
Describe the structural basis and importance of the blood brain barrier (BBB)
BBB consists of endothelium of capillaries (with tight junctions), basal lamina (basement membrane), and the astrocytes
It is a barrier with selective permeability to protect and maintain a constant environment for neurons. It allows H2O, glucose, CO2, caffeine, and nicotine to freely pass.
It is absent in the circumventricular organs in the 3rd and 4th ventricles for (ex: in the hypothalamus, responsible for vomiting responses)
= inflammation of the meninges. Can be bacterial or viral, Infection by nose and throat, affects pia mater & arachnoid. Disease of infancy and childhood mostly (3 months- 2 years), although bacterial meningitis can cause outbreaks on college campuses. High fever, stiff neck, headache, drowsiness, rash, coma
= also known as "water on the brain", is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid (CSF) in the ventricles of the brain. This may cause increased intracranial pressure inside the skull
and progressive enlargement of the head, convulsion, tunnel vision, and mental disability. Hydrocephalus can also cause
death. Although it does occur in older adults, it is more common in infants.
= referred to as a cerebrovascular accident (CVA), cerebrovascular insult (CVI), or colloquially brain attack. It is the loss of brain function due to a disturbance in the blood supply to the brain.
This disturbance is due to either ischemia
(lack of blood flow as in a clot) or hemorrhage. In most cases, the symptoms affect only one side of the body (unilateral).
Depending on the part of the brain affected, the defect in the brain is usually on the opposite side of the body. However, since these pathways also travel in the spinal cord and any lesion there can also produce these symptoms, the presence of
any one of these symptoms does not necessarily indicate a stroke. Symptoms of stroke appear suddenly.
Watch for these symptoms and be prepared to act quickly for yourself or on behalf of someone you are with:
-Sudden numbness or weakness of the face, arm, or leg, especially on one side of the body.
-Sudden confusion, trouble talking, or understanding speech.
-Sudden trouble seeing in one or both eyes.
-Sudden trouble walking, dizziness, or loss of balance or coordination.
-Sudden severe headache with no known cause.
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