CHAPTER 13 TEST REVIEW Flashcards
four main brain regions
Cerebrum
Diencephalon
Brainstem
Cerebellum
Clinical View: Traumatic Brain Injuries
Traumatic brain injury (TBI)
* Acute brain damage occurring as a result of trauma
Concussion
* Most common type of TBI
* Temporary loss of consciousness, headache, drowsiness,
confusion, and amnesia possible
* May have cumulative effect on intellect, personality, mood
Contusion
* Bruising of brain due to trauma
Second impact syndrome (2nd injury before 1st resolves)
* Develop severe brain swelling
Progesterone is possibly therapeutic for TBI
Clinical View: Neural Tube Defects
Serious developmental deformities of brain, spinal cord, meninges
Risk lowered by taking Vitamin B12 and folate in pregnancy
Anencephaly
* Substantial or complete absence of a brain
* Infant dies soon after birth
Spina bifida
* Failure to close caudal portion of neural tube
* Spina bifida cystica
* Almost no formation of vertebral arch; large cyst in back
* Often causes paralysis of lower limbs
* Spina bifida occulta
* Partial defect of bony arch
* Less serious, more common
Clinical View: Epidural and Subdural Hematomas
Epidural hematoma
* Pool of blood in epidural space of brain
* Usually due to severe blow to the head
* Adjacent brain tissue distorted and compressed
* Can lead to severe neurological injury or death unless
bleeding stopped and blood removed
Subdural hematoma
* Hemorrhage in subdural space
* Typically from ruptured veins from fast rotational head
movement
* Compression of brain tissue, occurs more slowly than
epidural hematoma
Clinical View: Meningitis and Encephalitis
Meningitis
* Inflammation of the meninges, typically caused by viral or
bacterial infections
* Symptoms—fever, headache, vomiting, stiff neck
* Pain from meninges sometimes referred to posterior neck
* May result in brain damage and death if untreated
* Bacterial meningitis with more severe symptoms
Encephalitis
* Inflammation of the brain, most often from viral infections
* Symptoms – drowsiness, fever, headache, neck pain, and
may result in death
Clinical View: Hydrocephalus
Pathologic condition of excessive CSF
Often leads to brain distortion
May result from obstruction in CSF restricting reabsorption
May result from intrinsic problem with arachnoid villi
In a young child, head enlarged with possible neurological
damage
May be treated surgically
* Implant shunts that drain CSF to other body regions
Clinical View: Autism Spectrum Disorder
Autism affects 1 in 88 U.S. children
Characterized by social and communication difficulties
Severity varies across autism spectrum
* Best predictors of independent adulthood are intelligence
and communication ability
Specific causes unknown
* Genetic, environmental, and biochemical factors have
been explored
* Males have four times higher incidence than females
* Vaccines found not to be a factor
Clinical View: Epilepsy and Cerebral Lateralization
Epilepsy
* Neurological disorder
* Neurons transmitting action potentials too frequently and
rapidly
* Usually controlled by medications, but may require
surgical removal of part of brain
* In most severe cases, may require hemispherectomy: removal of
side of brain responsible for seizure activity
* Remaining hemisphere able to take over some functions of missing
hemisphere
Clinical View: Cerebrovascular Accident
- Reduced blood supply to part of brain
- Due to blocked arterial blood vessel or hemorrhage
- May cause brain tissue death if prolonged for several
minutes - Symptoms of blurred vision, weakness, headache,
dizziness, walking difficulty - Affects opposite side of body
- Brief episode is a transient ischemic attack (TIA)
Clinical View: Brain Disorders
Headache
* Due to dilated blood vessels in skull or muscle contraction
* Migraine headaches: severe, recurring, often unilateral
* Not true brain disorder, but may accompany them
Cerebral palsy
* Group of neuromuscular disorders
* Result from damage to infant brain before, during, or right
after birth
* Impairment of skeletal muscle, sometimes mental
retardation
Huntington disease
* Hereditary disease affecting cerebral nuclei
* Rapid, jerky, involuntary movements
* Intellectual deterioration
* Fatal within 10 to 20 years after onset
Parkinson disease
* Affects muscle movement and balance
* Stiff posture, slow voluntary movements, resting tremor
* Caused by decreased dopamine production in substantia
nigra
Clinical View: Effects of Alcohol and Drugs on the
Cerebellum
Variety of drugs can impair cerebellar function
* Includes alcohol
* Symptoms
* Disturbance of gait
* Loss of balance and posture
* Inability to detect proprioceptive information
Clinical View: Pathologic States of Unconsciousness
Fainting: brief loss of consciousness
* Often signals inadequate cerebral blood flow due to low
blood pressure
Stupor: arousable only to extreme stimuli
* Accompanies some metabolic disorders, liver or kidney
disease, brain trauma, or drug use
Coma: deep and profound unconsciousness; nonresponsive
* Causes include severe head injury, metabolic failure, CVA,
very low blood sugar, or drugs
Persistent vegetative state: Lack of thought and awareness
but noncognitive brain functions continue
* Some spontaneous movements possible
Clinical View Alzheimer Disease: The “Long Goodbye”
Leading cause of dementia in developed world
Slow, progressive loss of higher intellectual function
Usually starts after age 65
Changes in mood and behavior
Eventual loss of memory and personality
Underlying cause unknown
* Significance of beta amyloid plaques and tau tangles is
debated
No cure, some medications to help slow course
Seems identifiable with positron emission tomography (PET)
Loss of sense of smell may be an early sign of the disease
Clinical View: Amnesia
Partial or complete loss of memory
Usually temporary and affecting only a portion of experiences
Causes
* Psychological trauma
* Direct brain injury
Type and degree of recovery
* Depends on part of the brain damaged
Damage to thalamus and limbic structures, especially
hippocampus, disrupts or prevents formation of new
memories
Clinical View: Dyslexia
Inherited learning disability
Problems with single-word decoding
Individuals with trouble reading, writing, and spelling
Level of reading competence below expected intelligence
Improvement in some individuals with time
May be form of disconnect syndrome
* Impaired transfer of information through corpus callosum
embryology of the brain
Primary brain vesicles
form by late 4th week from
cranial neural tube
* Forebrain =
prosencephalon
* Midbrain
=mesencephalon
* Hindbrain =
rhombencephalon
secdoary brain vesicles form
by 5th week
* Telencephalon
* Diencephalon
* Mesencephalon
* Metencephalon
* Myelencephalon
gray/white matter
Gray matter made of neuron cell bodies, dendrites, and
unmyelinated axons
White matter consists of myelinated axons
meninges
Three connective tissue layers
Separate and support soft tissue of brain
Enclose and protect blood vessels supplying the brain
Help contain and circulate cerebrospinal fluid
From deep to superficial
* Pia mater
* Arachnoid mater
* Dura mater
ventricles
Cavities within the brain
Lined with ependymal cells
Contain cerebrospinal fluid
Connect with each other and with spinal cord’s central
canal
Four ventricles within brain
Two lateral ventricles
Third ventricle
Fourth ventricle
CSF-characteristics/formation
Clear, colorless liquid surrounding CNS
Circulates in ventricles and subarachnoid space
Functions:
* Buoyancy – reduces brain’s apparent weight by 95%
* Protection – provides a liquid cushion
* Environmental stability – transport of nutrients / wastes and
protects against fluctuations
CSF-formation
Formed by choroid plexus in each ventricle
* Layer of ependymal cells and blood capillaries (within pia)
* Blood plasma is filtered through capillary and modified by
ependymal cells
* Compared to plasma, CSF has more Na+, Cl–; less K+, Ca2+,
glucose
* In addition, ependymal cell secretions and interstitial fluid
from subarachnoid space help make up CSF
CSF is continually formed and reabsorbed
* Excess CSF flows into arachnoid villi and drains into
dural venous sinuses
* An arachnoid granulation is a collection of these villi
BBB
Functions of blood-brain barrier (BBB)
* Regulates which substances enter brain’s interstitial fluid
* Helps prevent neuron exposure to harmful substances
* Drugs, wastes, abnormal solute concentrations
* Note: some drugs can pass and affect the brain (for example,
alcohol
BBB composed of specialized capillaries
* Endothelial cells are connected by many tight junctions
* Walls have a thick basement membrane
* Wrapped by perivascular feet of astrocytes
BBB reduced in certain locations for functional reasons
* Choroid plexus needs to produce CSF
* Hypothalamus and pineal gland need to secrete hormones
Motor areas
- Housed within frontal lobes
- Primary motor cortex located in precentral gyrus
- Also called somatic motor area
- Controls skeletal muscle activity on opposite side of body
- Project contralaterally (opposite side) within brainstem or spinal cord
- The controlled body regions map as a motor homunculus
- Distorted proportions of the body reflect amount of cortex dedicated to
each part - For example, hands are large on homunculus because large area of
brain controls their precise movements
Motor speech area (Broca area)
* Located in inferolateral portion of left frontal lobe (in most people)
* Controls movements for vocalization
* Frontal eye field
* On superior surface of middle frontal gyrus
* Regulates eye movements needed for reading and binocular vision
* Premotor cortex (somatic motor association area)
* Located anterior to premotor cortex
* Coordinates learned, skilled activities
sensory areas
Primary somatosensory cortex
* Located in postcentral gyrus of parietal lobes
* Receives somatic sensory information from
* Proprioceptors, touch, pressure, pain, temperature receptors
* Areas of the body sending input can be mapped as a sensory
homunculus
* Distorted proportions reflect the amount of sensory information collected
from that region
* Large regions for lips, fingers, genital regions
Somatosensory association area
* Immediately posterior to postcentral gyrus (in parietal lobe)
* Integrates touch information allowing us to identify objects by fee
Primary visual cortex
* Located within occipital lobe; receives, processes, stores visual
information
Visual association area
* Surrounds primary visual cortex; integrates and interprets color,
form, to allow identification/recognition of things (for example,
faces)
Primary auditory cortex
* Located within temporal lobe; receives, processes, stores auditory
information
Auditory association area
* Located in temporal lobe; integrates and interprets sounds
Primary olfactory cortex
* Located within temporal lobe
* Receives, processes, stores odor information
Primary gustatory cortex
* Located within insula
* Receives, processes, stores taste information
