Central Nervous System Flashcards
Describe the embryologic origins (primary germ layers) of the brain, beginning with formation of the neural
plate
step 1.) 3rd week - ectoderm thickens and forms neuroplate
and it invaginate, forming the neural groove (surrounded by folds) these folds fuse and develop into the neurotube
some if the folds pinch off and develop the neural crest (which makes the PNS)
neural crest - somites - dermis, muscles and skeleton
- The neural tube - neural tube differentiates into the brain and spinal cord
From what primary germ layer does all nervous tissue originate?
ectoderm
Identify the adult brain structures associated with each of the three primary brain vesicles.
Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)
What single factor can prevent most cases of neural tube defects?
taking folic acid
What are the 3 structural outcomes of the fact that the brain develops within a restricted
space?
1.) surface convolution
sulci - depressions
gyri - elevations and sulci goes between them
Increase surface area so more neurons can pack in and more impulses come through
- ) the way it grows, cerebral hemispheres grow posteriorly and laterally
- ) midbrain and cervical flexures (bending and curves)
What does gray matter comprise? white matter?
gray matter - makes cerebral cortex , short, nonmyelinated axons and neuron cell bodies
white matter - bundles of nerve fibers (tracts) in cns, myelinated
What is meant by the term hemispheric (or cerebral) lateralization? by the term cerebral
dominance?
laterialization - two distinct hemispheres of the brain
dominance - one hemisphere is dominant for language over another (most people are left hemisphere dominant for language, math, etc while right is more abstract thought)
Identify and describe the two most common types of neural tube defects.
- Anencephaly - failure to close ANTERIOR neural tube
2. Spina Bifida - failure to close of the POSTERIOR neural tube
What is the septum pellucidum?
A thin membrane located at the midline of the brain between the two cerebral hemispheres (lateral ventricles)
Name the five lobes of the cerebrum and identify the sulci or fissures that separate one
lobe from another.
Frontal lobe
- Precentral gyrus
- Centeral sulcus
- Postcentral gyrus
Parietal lobe
- Pareto-occipital sulcus
Occipital lobe
-Transverse cerebral fissure
Cerebellum
From partial lobe to temporal lobe theres the lateral sulcus
What is the general function of each of the following cortical areas?
Motor Area’s:
- primary motor cortex - premotor cortex
- Broca’s area (the motor speech area)
- Wernicke’s area
- frontal eye field
Primary motor cortex - Located in the precentral gyrus in the frontal lobe
- contains pyramidal cells which create tracts
Controls voluntary contractions on the opposite side of the body
Premotor movement- Anterior to precentral gyrus in the frontal lobe
- involved in planning movements and in controlling learned, skilled movements
Broca’s area - above lateral sulcus
- functions thoughts to speech
Damage: non fluent aphasia ( when you know what you want to say but cant say it)
Wernicke’s area - posterior part of the left temporal lobe
- involved in comprehension of language (speech and written)
Frontal eye field - located in the frontal lobe
- controls voluntary scanning movement of the eye
Test: Tract by asking patient to read and tract eye movement
What is the general function of each of the following cortical areas?
primary somatosensory cortex somatosensory association area primary visual cortex visual association area olfactory cortex gustatory cortex vestibular cortex visceral sensory area affective language area
- ) primary somatosensory cortex - in postcentral gyrus of each parietal lobe
* receives sensory stimuli from the opposite (contralateral) side of the body
* capable of spatial discrimination (being able to identify what part of the body is stimulated) - ) somatosensory association area -
- ) primary visual cortex
- ) visual association area 5.) olfactory cortex
- ) gustatory cortex
- ) vestibular cortex
- ) visceral sensory area
What is the general function of each of the following cortical areas?
sensory areas:
primary somatosensory cortex somatosensory association area primary visual cortex visual association area olfactory cortex gustatory cortex vestibular cortex visceral sensory area affective language area
- ) primary somatosensory cortex - in postcentral gyrus of each parietal lobe
* receives sensory stimuli from the opposite (contralateral) side of the body
* capable of spatial discrimination (being able to identify what part of the body is stimulated) - ) somatosensory association area - posterior to primary somatosensory cortex
* functions in integrating & interpreting sensory inputs (touch sensations)
3.) primary visual cortex -
extreme posterior tip of occipital lobe at calcimine sulcus
* receives sensory input regarding shape, color , and movement
4.) visual association area- surrounds primary visual cortex in the occipital lobe
*recieves input from the primary visual cortex & the thalamus
TEST: Ask patient to identify object. Eraser —-rubber (incorrect)
- ) primary auditory cortex - located in superior part of temporal lobe, near lateral central sulcus
* receives input from cochlea (hearing part of inner ear) - ) auditory association area- inferior and posterior to the primary auditory cortex
* involved in perception/interpretion of sound (retains memory or sounds and meanings of speech)
5.) olfactory cortex - located in medial aspect of temperol lobe
*recieves input related to smell and acknowledges orders
TEST: smell associated with emotions
- ) gustatory cortex - located above lateral cerebral sulcus
* taste stimuli are recieved (sweet, salty, butter etc) - ) vestibular cortex- located in the posterior insult
* involved in awareness of balance - ) visceral sensory area
* involved in conscious perception of visceral sensation
What is the general function of each of the following cortical areas?
Multimodel association areas (send output to premotor cortex):
anterior association area/prefrontal cortex
posterior association area
limbic association area
anterior association areas/ prefrontal cortex -
involved with intellect, judgement, and personality. sets mood and emotions
posterior association area-
different in L and R cerebral hemisphere
- affective language thought to be in the L hemisphere
limbic association area
in cerebrum and diencephalon
- emotional brain -
What is the reticular formation? Where is it located?
-Maintains cerebral cortical alertness (reticular activation system)
- Filters out repetitive stimuli
- Helps regulate skeletal and visceral muscle activity
what is memory?
the storage and retrieval of information
Identify and describe the main categories of long-term memory
declarative memory (fact), procedural memory (skills), motor memory, and emotional memory
Identify the stages of declarative memory and describe the characteristics of each.
short term and long term memory
Short-term memory allows you to remember small chunks of info to use and never remember again. Long-term memory allows us to store a lot of information in our memory bank to retrieve later
Identify the factors that can influence memory consolidation (i.e., transfer from STM → LTM) and describe their effect.
- Emotional state -
We learn best when we are alert, motivated, surprised, or aroused. Neorepinephrine is a transmitter - Rehearsal - rehearsing or repeating material enhances memory
- Association - associating new information with old memories
- Automatic memory- automatically tracking something subconsciously (when some words stick with you)
Identify and contrast the four frequency classes of brain wave seen in an EEG.
Alpha waves (awake but relaxed) 8-13 Hz
Beta waves - (awake, alert)
(14-30 Hz)
Theta waves (common in children)
Delta waves (deep sleep)
Alpha waves: 8-13 Hz, regular, low amplitude, synchronous, indicate brain is relaxed and wakeful
Beta waves: 14-30 Hz, less regular, higher frequency, occur when mentally alert and concentrating
Theta waves: 4-7 Hz, more irregular, common in children, may appear in adults when concentrating
Delta waves: 4> Hz, high amplitude, seen when asleep or under anesthesia (when RAS is suppresses), indicates brain damage in awake adults
What is the primary EEG wave form during periods when an adult is alert and concentrating and problem-solving? when one is alert and relaxed? during deep sleep?
beta; alpha; delta
What is sleep?
a state of partial unconsciousness from which a person can be aroused by stimulation
What are the two main types of sleep?
Non-rapid eye movement (NREM)
Rapid eye movement (REM)
Identify and describe the characteristics of each of the stages of non-rapid eye movement (NREM) sleep. Be sure to include mention of typical EEG patterns and general physiological characteristics in your descriptions.
Stage 1: Relaxation; alpha waves; easy to arouse
Stage 2: Irregular EEG with sleep spindles; arousal is more difficult
Stage 3: Theta and delta waves; vital signs decline
Stage 4: Dominated by delta waves; arousal is difficult; bedwetting, night terrors, and sleep walking may occur
Describe the characteristics of rapid eye movement sleep, including mention of typical EEG pattern and general physiological characteristics in your description.
alpha waves, skeletal muscles actively inhibited, most dreaming occurs
Describe the pattern of NREM and REM sleep over one sleep period (i.e., during one night).
First 30-45 minutes: pass through first 2 stages of NREM
After 45 minutes: go to stages 3 and 4
After 90 minutes: onset of REM
Cycles every 90 minutes
Identify and describe the structures and/or materials which protect the brain & spinal cord.
Bone (skull and vertebrae), meninges (three connective tissue membranes that lie just external to the CNS organ), and cerebrospinal fluid
What are the functions of the meninges?
1) cover and protect CNS
(2) protect blood vessels and enclose venous sinuses (3)contain cerebrospinal fluid
(4) form partitions in the skulli
List the meninges and spaces in order (from superficial to deep, or vice versa).
Dura mater, arachnoid mater, and pia mater
Name the dural septa and tell where each is located.
falx cerebri: attaches to crista galli; dips into longitudinal fissure
falx cerebelli: runs along vermis of cerebellum; inferior to falx cerebri
tentorum cerebelli: estenda into transverse fissure between cerebral hemispheres and cerebellum
In what meningeal space does CSF circulate?
subarachnoid space beneath arachnoid membrane
What are the dural venous sinuses? How are they formed? In what part of the CNS are they located? What is their function?
Spaces that are formed by the periosteal and meningeal layers of the dura mater. They collect venous blood from the brain and direct it into the internal jugular veins of the neck
Which of the meninges adheres to the surface of the brain & spinal cord?
pia matter
What is the function of CSF?
reduces brain weight to prevent it from being crushed, provides nourishment, protects brain and spinal cord from trauma
Describe the structure & function of a choroid plexus. Where are the choroid plexuses located?
makes csf
clusters of thin-walled capillaries enclosed by Pia mater and a layer of ependymal cells. They line the roofs of ventricles and filter tissue fluid from the blood. They are joined by tight junctions and have ion pumps to modify the filtrate.
What cells produce CSF?
ependymal cells in the choroid plexus
Describe the path of CSF circulation, beginning at the lateral ventricles.
beginning at the lateral ventricles.
- produced by choroid plexus of each ventricle
- flows through ventricles and into subarachnoid space
- flows through subarachnoid space
- absorbed unto dural venous sinuses through arachnoid granulations
What is the function of the arachnoid granulations?
absorb CSF into venous blood of the dural venous sinus
What structural features create the blood-brain barrier?
tight junction between capillary endothelial cells maintained by bulbs of astrocytes and pericytes
What is the function of the blood-brain barrier?
Maintains the brain’s stable environment through diffusion and specific transport mechanisms
What is a concussion? Distinguish between concussion and contusion.
concussion - temporary altered brain function after a blow to the head.
contusion- a serious concussion that bruises the brain and leads to permanent brain damage
Distinguish between CVAs (cerebrovascular accidents or strokes) and TIAs (transient ischemic attacks). What is the effect of each on brain function?
CVAs occur when blood circulation to a brain area is blocked and brain tissue dies (ischemia), leading to hemiplegia. TIAs are temporary episodes of ischemia.
Describe the general structure of the spinal cord, with reference to size, the gray matter, white matter, meninges and spaces.
42 cm (17 inches) long and 1.8 cm (0.75 inches) thick.
Dura mater is single layered. Epidural space with fat and veins between vertebrae and spinal dura mater. CSF is in subarachnoid space.
Spinal cord tapers in conus medallions and film terminal (covered in pia mater)/ Gray matter is in the core and white matter is on the sides.
What causes the cervical and lumbar enlargements?
nerves serving the upper and lower limbs arise
Where are the cell bodies of motor neurons located?
ventral horns
What is located in the dorsal root ganglia?
cell bodies of associated sensory neurons
In what segmental levels of the cord are the lateral horns located?
thoracic and superior lumbar segments
Name and identify the location of the four functional zones of gray matter (present on each side of the cord).
gray commissure - encloses central canal
dorsal horn - contains interneurons that run down length (posterior)
ventral horns - contains mostly somatic motor neurons (anterior)
lateral horns - cell bodies of autonomic motor neurons for visceral organs (lateral in thoracic and superior lumbar segments)
Describe the organization of the white matter of the cord.
Tracts with ascending fibers, descending fibers, and transverse fibers; bilateral
Name the neurons which comprise the ascending (i.e., sensory) pathways. Where are the cell bodies of each type of neuron located?
First-order neurons - dorsal root or cranial ganglion
Second-order neurons - dorsal horn or medullary nuclei
Third-order neurons - thalamus
Identify the nonspecific ascending pathways.
the anterior and lateral spinothalamic tracts
Locate the first-, second-, and third-order neurons of the spinothalamic tracts. Where do these tracts decussate?
decussate immediately at or near their level of canal entry
What type of sensory information is carried by the anterior spinothalamic tract? by the lateral spinothalamic tract?
anterior - crude touch, pressure, tickle, itch, and pain
lateral - pain and temperature
Identify the specific ascending pathways.
dorsal column-medial lemniscal pathway
- broken down into fasciculus cuneatus and fasciculus gracilis
Locate the first-, second-, and third-order neurons of the fasciculus cuneatus and fasciculus gracilis. Where do these tracts decussate?
First-order: skin
Second-order: medulla
Third-order: thalamus
decussate in medulla
What type of sensory information is carried by the fasciculi cuneatus? by the fasciculi gracilis?
conscious proprioceptor, fine and discriminative touch, pressure, and vibration
Locate the first- and second-order neurons of the anterior and posterior spinocerebellar tracts. Explain why these tracts carry sensory information from one side of the body to the ipsilateral side of the cerebellum.
They either do not decussate or decussate twice
What type of sensory information is carried by the spinocerebellar tracts?
coordinate skeletal muscle
Name the two neurons that comprise the somatic motor pathways. Where are the cell bodies of each type of neuron located?
upper motor neurons (in subcortical motor nuclei)
lower motor neurons (ventral horn of cord or cranial nerve nuclei of brain stem)
Identify and describe the direct (pyramidal) tracts, including location of upper and lower motor neurons of the tract and level at which decussation occurs.
Pyramidal neurons ar precentral gyrus; descend to spinal cord or CN nuclei without synapsing. Decussate in medulla
What type of efferent information is carried by the lateral corticospinal tracts? by the anterior corticospinal tracts? by the corticobulbar tracts?
lateral - muscles of extremities
anterior - muscles of neck and trunk
coritcobulbar - precise, voluntary movements of face and mouth
Determine possible signs/symptoms of a patient with a neural tube defects
Anencephaly - diagnosed in utero; total or partial absence of brain, skull, and scalp; totally vegetative child; most die in utero or a few hour after birth
Spina bifida - incomplete formation of vertical arches; failure to close of posterior neural tube; indicated by sacral dimple or patch of hair; varying degrees of severity from paralysis, bowel and badder dysfunction, and normal life
Determine the appropriate techniques to assess cerebral functional sensory areas, specifically the visual, olfactory and vestibular cortices.
Visual
- to test frontal eye field, give patients a paragraph and track how their eyes follow the words
- to test primary visual cortex, give patients an eye chart
- to test visual association area, give patients Snellen and additional eye assessments
Olfactory
- to test olfactory cortex, ask patients to close one nostril and both eyes and put something under their nostril to smell/identify
Vestibular Cortex
- have patients walk while checking for symmetry, posture, balance, and freedom of movement (heel to toe, on toes, and on heels)
- Romburg exam: have them stand still with eyes closed with your arms around them to check for swaying (equilibrium
