W11. Chapter21. Nervous System Flashcards
1
Q
Nervous System consists of
A
- Brain and spinal cord
- peripheral nervous system (peripheral nerves, autonomic ganglia)
- closely interrelated with the endocrine system and skeletal muscles
2
Q
Brain includes
A
-cerebrum, cerebellum, brain stem. Can be further seperated to the midbrain, pons, and medulla oblongata
3
Q
Largest part of the brain
A
- the cerebrum.
- Is separated into 2 hemespheres, which are connected through a number of commissures, most prominent is corpus callosum
4
Q
What is the giri and sulci
A
- external surface of the brain is arranged into giri, which are separated by invaginations called sulci
- giri is composed predominently by grey matter -cortex
- brain tissue beneat the cortex is called white matter
5
Q
Deep part of the brain
A
- also contain grey areas- form basal ganglia, thalamus, and hypothalamus
- cortex and subcortical gray matter are composed of numerous neurons and support cells
- the axons extend into the white matter where they are mylenated
6
Q
Lobes of the cerebrum
A
- frontal: motor functions, behavior, emotions, intelect
parietal: sensory
temporal: hearing and smelling
occipital: visual
7
Q
What do the basal ganglia do?
A
-supply inhibitory stimuli to skeletal muscles, coordinate skeletal muscle contraction, block unwanted muscle contraction
8
Q
Function of the thalamus
A
- nb for integrating sensory stimuli
- nb determinant for conciousness
9
Q
Function of the hypothalamus
A
- crossroad that connects different parts of the brain
- involved in body functions: bp, temp reg, hr, thirst
- source of neurosecretory substances that stimulate the pituitary to produce tropic hormones- regulating the function of endocrine glands
10
Q
Midbrain, pons, and medullaoblongata
A
- contain numerous mylenated nerve bundles
- regulate elementary body functions
11
Q
Function of the cerebellum
A
- major regulator of motor activities
- receives sensory input from the spinal cord and vestibular organ of the inner ear, as well as motor impulses brom the cerebral cortex
- damage affects coordination of limb and eye movements
12
Q
Components of the spinal cord
A
- consists fo grey and white matter. Grey matter located internal to the white matter, around the central canal
- grey matter has butterfly like shape on cross section, with posterior and anterior horns that consist of neurons and unmyelenated nerve fibers
tracts- p.469
13
Q
Peripheral and Autonomous nervous system
A
p.469
14
Q
The brain is enveloped by
A
-menenges- specialized connective tissue
15
Q
Facts of the Nervous system:
Consists of highly specialized functional units
A
- loss of certain parts of CNS results in certain loss of function defects
- irreversible, since neurons dont regenerate
16
Q
Facts of the nervous system:
CNS is protected by bones of scull and vertebrae
A
- skull encloses the brain and sheilds it
- brain wounds occur if integrety of the skull is disrupted
- vertebrae are linked together by intervertibral disks and tendons that allow for a certain degree of mobility
- spinal cord therefore more suseptible to external trauma
17
Q
facts of the nervous system: Seperation of CNS from remainder of body
A
- by menenges and blood brain barrier
- CNS has an abundant blood supply - which ensures constant supply of energy.
- brain must remain relatively isolated from the metabolic functions of the body that may adversely affect neurons
- blood brain barrier acts like a filter, allowing some pasage of substances from blood to CSF ex. bilirubin does not enter
18
Q
Functions of CSF: Brain
A
- separate brain from meneges
- mechanical buffer between brain and bones of skull
- serves as venue for disposition of waste products and metabolites from the brain. Normally, its composition does not fluctuate much. Ex. neutrophils in menengitis
- Production, flow, and resorption of CSF remains constant. Obstruction can lead to hydocephalus
19
Q
Principal Cells of the CNS
A
- Neurons: non-invading, post-mitotic, permanent cells
- Glial cells: support the neurons, faculative and mitotic, capable of dividing when stimulated
- contains billions of neurons, all of which are formed in prenatal intrauterine life. neurons are long lived cells. Loss of neurons can not be replaced b/c remaining neurons can not divide, and brain does not have reserve. therefore, every lost of brain substance results in permanent defect.
- glial cells: retain capacity for multiplication, and can multiply in response to certain forms of injury. Ex. Gliosis, increased number of glial cells, in repsonse to brain injury. Found around brain tumors, foci of intracerebral hemmorhages, brain infarct.
- b/c adult neurons are incapable of dividing, adult brain cancers orginate from glial cells (glioma). In children, malignant cells of neural cell origin originate from undifferentiated precursors of neural cells.
- menenges and blood vessels of the brain can proliferate and cause tumors (menengioma)
20
Q
Facts about the CNS and Diseases
A
- The CNS can be affected by diseases that involve other organs, or by diseases that are unique to the CNS
- especially circulatory, metabolic and infectious
- diseases restricted to the brain may be caused by neurotropic pathogens or b/c of metabolic changes unique to neural cells. Ex. rabies is neurotropic virus which infects only nerve cells. Ex. neurodegeneration in Parkinsons
21
Q
Increased intracranial pressure from cerebral edema may lead to
A
may lead to loss of conciousness, progressing to coma or death
- brain edema may be caused by multiple brain lesions, intracranial hemmorhage, inflammation, and numerous metabolic or circulatory disturbances such as shock
- increased ICP is a life threatening condition
- symptoms depend on the pace
22
Q
A rapid, but gradual increase in ICP withh result in
A
- severe headache that ususally accompanied by vomiting, blurry vision, and loss of conciousness
- these patients usually lapse into a coma, and die of apnea as a result of inhibition of medulary vital centers
23
Q
Death from increased ICP result from
A
- compression of vital centers in the brainstem
- most often, the centers of the medula oblongata are compressed by the edematous tonsils of the cerebellum, which herniates through the foramen magnum
- herniation of the medial portion of the cerebral hemisphere beneath the tentorium cerebilli may compress pons and also cause death
24
Q
Symptoms of CNS dysfunction
A
-some may result from subtle changes in brain cells that can not be recognised microscopically. Ex schizophrenia - no seen pathological changes-occur at subcellular level
25
Q
Developmen of CNS (normally)
A
- CNS develops from the neural plate, which folds and closes into a neural tube extending along the dorsal side of the body axis.
- As the neural tube forms, it becomes internalized and is protected by the overlying skin
- the mesenchyme between the skin and the neural tube is induced to form bone- which gives rise to the skull and vertebrae, which finally encase the spinal cord
26
Q
What gives rise to dysraphic disorders
A
- incomplete fusion of the neural tube, and defective formation of the menenges, calvaria, or vertebrae
- If the calvaria are not formed, and the brain is destroyed in-utero, the malformation is anencephaly.
Milder dysraphic malformations, such as meningocele, myelome-ningocele, and spina bifida, are characterized by a lack of fusion of the posterior bone coverings.
If the meninges protrude through the bony defect, the malformation is called meningocele. I
n myelomeningocele, the protrusion contains not only the meninges, but also a portion of the spinal cord.
Spina bifida is characterized by an absence of vertebral arches, resulting in exposure of the meninges or the spinal cord to the outer world.
Spina bifida may be evident at birth as a deep defect on the lower back, or it may be covered with skin and be inapparent (spina bifida occulta)”
27
Q
Intracrainial Hemmorhages: Classifications
A
- epidural
- subdural
- subarachnoid
- intracerebral
- may be caused by trauma, contusions, rupture of blood vessels (anuerism or HTN), or abnormalities of coagulation (congential or aquired bleeding disorders).
28
Q
Dysraphic Developmental Disorders: Image
A
29
Q
Hematoma: Image
A
30
Q
Epidural Hematoma
A
- located in the space between the scull and the dura, in a space that in under normal circumstances doesnt exist, b/c of close proximity between dura and the skull bones
- develop from ruptured meningeal artery, most often torn by a bone spindle resulting from a fracture of temporal bone
- arterial blood slowly fills the space, and separates the dura from the bone. Takes several hours before large hematomas are formed
- Once 50-60ml, it is large enough to compress the brain and cause coma
- in children, whose bones are not firmly fixated, arterial rupture can occur b/c of traumatic bone displacement
- can be lethal if not recongnized
31
Q
Subdural Hematomas
A
- space between the dura and arachnoid
- normally this space is bridged by thin-walled veins, that can be torn easily by trauma- especially blunt trauma which causes sudden movement of brain in one direction, and the dura in another
- found in boxers, and unattended bed ridden patients
- symptoms are non-specific, headache, but as it enlarges - may cause coma or death
32
Q
Subarachnoid Hemmorhages
A
- located in the space between the arachnoid and the pia (ie-brain surface)
- most often caused by traumatic contusion of the brain, blood leaks into the subarachnoid space from ruptured cerebral blood vessels at the base of the brain
- ruptured aneurisms of the Circle of Willis are another important cause. These congenital berry aneurisms are found in 1-2% of the population, most are silent. Rupture between 30-60yo, can be precipitated by HTN, but most often no obvious cause.
- bleeding into subarachnoid space associated with high mortality
- if recognised, berry aneurisms can be tx. surgically
33
Q
Intracerebral Hemmorhage
A
- common complication of head trauma
- contusion of brain and rupture of intracerebral blood vessels
- non-traumatic causes include stroke, leukemia and other clotting disorders
34
Q
Cerebrovascular Disease
A
- 3rd most common cause of death and most crippling disease in the USA
- Most common clinical manifestation is stroke
- Stoke: ischemic (85%-r/t atherosclerosis or thromboembolic occlusion of the cerebral arteries), (15% hemmorhagic, complicaton of htn).
- Atherosclerosis: narrowing may be gradual or may be sudden, may be widespread or localized lesions.
35
Q
Cerebrovascular Disease: Global Ischemia
A
- widespread atherosclerotic narrowing of entire cerebrovascular system develop multiple foci of ischemic necrosis
- such lacunar infarcts cause minor neurologic deficits, but over time will cause mental deterioration
- cardiac failure or other forms of vascular collapse, results in widespread infarcts
- these hypoperfusion infarcts located in parasagital cortex
- hypoperfusion leads to laminar necrosis of the deeper zones of the grey matter. -Blood does not get to the deep areas
- If blood flow restores, patients can recover with only minor deficits.
But even minor CVAs can have a cumulative effect
36
Q
Most common cause of cerebral infarct
A
- thrombocclusion of an atherosclerotic artery
- thromboemboli of heart chambers or valves the second most common cause
-
37
Q
Cerebral Infarct: Pathologic changes in the brain
A
- depends on time that has elapsed between onset of occlusion
- ischemic brain liquifies and ichemic part undergoes necrosis
- encephomalacia is the softening of the brain, may remain pale or may be red from collateral circulation and transform into a hemmorhagic infarct
- red infarcts are more common after cerebral embolization with arterial thromboemboli because these infarcts are more readily perfused from asdjasent non-infarcted vessels
- brain tissue is edematous. During phase of maximal cerebral swelling, the patients are at risk of dying
- within a few days, swelling goes down, and patients have a better chance of surviving. Margins of the viable tissue become vascularized
- necrotic tissue is removed by scavenger cells
- infarct turns into a fluid filled cavity (pseudocyst)
- brain infarcts cannot heal, and the neurological deficits caused by them are permanent
38
Q
Clinical Presentation of Cerebral Infarct
A
- Depends on location
- Occlusion of middle cerebral artery is most common cause, contralateral hemiplegia, sensory loss on the same side of the body, bilateral symmetric loss of vision in half of the visual fields, with eyes deviating to the side of the lesion.
- Global aphasia occurs if the infarct occurs in the dominant hemisphere
39
Q
Treatment of Stroke
A
- life supportive measures
- brain edema: corticosteroids, dehydrating hyperosmolar agents that drain fluid from brain into circulation
- physical therapy as part of long term rehab, OT
40
Q
Location of Infarcts: Image
A
41
Q
Prognosis with stroke: %
A
- 80% of people survive initial stroke
- 60% are alive 3 years after
- 25% chance of having another stroke
42
Q
Intracerebral Hemmorhage
A
- in patients with no vascular abnormalities, most often caused by arterial htn
- ruptured small vessels that have been damaged mechanically by HTN
- most common sites are basal ganglia (2/3)
- Cerebellar or pontine account for rest
- Intracerebral hemmorhage results in a well circumscribed hematoma that is visible on CT. They are surrounded by edematours brain tissue. Infarct turns into a pseudocyst, containing hemosiderin-laden macrophages.
46
Q
Head injury:image
A
53
Q
Bacterial Infections: Image
A
70
Q
Degenerative Diseases: Image
A
