exam 3 Flashcards
Nervous System (NS)
• The “control system” for our body
• Responsible for all movements involved in speech
production
• Normal functioning NS required for normal speech
• NS disruptions result in abnormal speech
• NS disruptions can also result in language and cognitive
disorders
NS Divisions
- Central Nervous System (CNS)
- brain and spinal cord
- Peripheral Nervous System (PNS)
- somatic system
- cranial and spinal nerves
- autonomic system
- sympathetic division (activating)
- parasympathetic division (dampening)
Brain Tissue: Glial Cells
- Made of connective tissue
- Known as the “supporting cells”
- Four main functions:
- Surround neurons and hold them in place
- Supply nutrients and oxygen to neurons
- Insulate one neuron from another
- Destroy and remove dead neurons (waste)
Brain Tissue: Glial Cells
Astrocytes
Oligodendrocytes
Schwann cells
Microglia
Astrocytes
ost common type; connect blood and
nerve cells
Oligodendrocytes
found in the CNS; forms myelin
sheath (insulation layers that wrap around nerve cells)
Schwann cells
found in the PNS; forms myelin sheath
Microglia
found in CNS; clean up waste and harmful
organisms
Brain Tissue: Neurons
Specialized nerve cells that processes and transmits
information through electrical and chemical signals
The core component of the NS
Basic structure across all neurons
Neuron Structure
• Cell body (or soma): made up of a nucleus surround
by cytoplasm
• Organelles are specialized microstructures located in
the cytoplasm
• Dendrites: short projections that branch off the cell
body; transmit nerve impulses towards the cell body
• Axon: extends off the cell body; transmit nerve
impulses away from the cell body
• Myelin sheath wraps around most axons
• Nodes of Ranvier: interrupt myelin sheath; speed up
rate of nerve transmission
• Terminal branches: axon divides at its endpoint;
branches end in terminal buttons
• Terminal buttons: contain neurotransmitters; the
site of communication from with nerve cells
Neuronal Communication
Synapse: gap between nerve cells
• Axo axonal synapse: synapse between an axon and
another axon
• Axo somatic synapse: synapse between an axon and
cell body (soma)
• Axodendritic synapse: synapse between an axon
and dendrite
• Communication accomplished by neurotransmission
Neurotransmission
An electrochemical process
◦ At rest, more positive ions (Na+ and K+) outside cell and
more negative ions (Cl-) inside cell
◦ Imbalance creates voltage across cell membrane, resting
membrane potential (RMP)
◦ Depolarization: Na+ enters cell, reversing electrical
charge to positive
◦ Repolarization: K+ leaves cell, reverting electrical
charge to negative
Central Nervous System
Protective tissue and fluid that surrounds the brain and
spinal cord
Three layered system:
1. Dura matter: outermost layer; tough connective
tissue; blood vessels
2. Arachnoid matter: delicate tissue; no blood vessels
3. Pia matter: delicate vascular tissue closest to the brain
CNS: Hemispheres
• Left hemisphere and right hemisphere
• Connected by nerve pathways, known as the corpus
callosum
CNS: Cortex
• Outermost layer of brain • “Gray matter” • Convoluted surface, with many folds: • Gyri: raised tissue • Sulci: shallow depressions • Fissures: deep grooves * Increase surface area without increasing space. • Neocortex: 95% of cortex. Responsible for higher order thinking and processing
CNS: Lobes of the Brain
Sulci and fissures separate cortex into four lobes:
1. Frontal
2. Parietal
3. Temporal
4. Occipital
Brodmann areas: 52 functional areas of human cortex
(including areas most important for speech & hearing) *
Caveats to Broadmann’s Area
1.Areas in brain are not completely separated and
boundaries are not precise
2. Identified areas in brain are not the only brain site for a
particular function
3. Lobes in left and right hemispheres are not identical in
either structure or function
Frontal Lobe
• Largest lobe in the brain.
• Motor and higher mental functions:
• Speech and language; Problem solving; Attention; Memory;
Personality and emotion; Symbolic function; Social behavior.
• Areas associated with speech & hearing:
• Motor strip(#4)
• Premotor area & supplementary motor area (#6)
• Broca’s area (#44, #45)
Parietal Lobes
- Sensory functions:
- Touch; Pressure; Pain; Proprioception; Temperature
- Areas associated with speech & hearing:
- Primary somatosensory area (#3, #2, #1)
- Somatosensory association area (#5, #7)
- Angular gyrus (#39)
- Supramarginal gyrus (#40)
Temporal Lobes
- Understanding functions:
- Hearing; Memory; Language (understanding and formulating).
- Areas associated with speech & hearing:
- Primary auditory cortex (#41)
- Auditory association area (#42)
- Wernicke’s area (#22)
Occipital Lobe
- Reception and processing of visual information
- Areas associated with speech & hearing:
- Primary visual area (#17)
- Visual association area (#18, #19)
Cerebrum
• Main mass of brain • “White matter” • Myelinated nerve fibers involved in the transmission of information • Deep in cerebrum, are pockets of gray matter: • Basal nuclei • Thalamus • hypothalamus
Cerebrum: Basal Nuclei
• AKA Basal Ganglia
• Composed of the caudate nucleus, globus pallidus,
putamen, and substantia nigra
• Primary functions to regulate motor control (balance,
posture, coordination) and precise voluntary
movements
• Damage to the basal nuclei is seen in conditions like
Parkinson’s Disease and Huntington’s Disease
Cerebrum: Thalamus
• A collection of motor function nuclei and sensory function nuclei. • The “gateway to consciousness” • And a “relay station” • Thalamic nuclei critical to speech and hearing: • Ventral anterior nuclei (VA) • Ventral lateral nuclei (VL) • Medical geniculate body • Lateral geniculate body
Brain Stem
- Midbrain
- Pons
- Medulla
Connects brain to spinal cord
Reflex control (e.g., respiration, body temperature,
swallowing, digestion)
Site of origin for cranial nerves
Reticular activating system: controls alertness
and consciousness
Cerebellum
• White matter mass, overlaid by cortex
• Two hemispheres, connected by nerve bundle
• Ipsilateral control
• Receives sensory information and sends motor
information
• Involved in balance, posture, background muscle tone,
and coordination of voluntary movement
Spinal Cord
Continuous structure, divided into: 1. Cervical (neck) 2. Thoracic (chest) 3. Lumbar (lower back) 4. Sacral (pelvis) 5. Coccygeal (tail bone) Contains cell bodies for the spinal nerves (31 pairs) that run to all muscles in bod
Spinal Cord
• Adult cord 42-45 cm long, 1 cm diameter
• Covered by the meninges
• White matter on outside and gray matter on inside
(reverse)
• Gray matter:
• Butterfly-shape, with anterior and posterior horns
• White matter:
• Funiculi: myelinated sensory and motor pathways bundled into
one large tract; dorsal, ventral, and lateral x2
Cranial Nerves
• 12 pairs
• Transmit information to and from face and neck
regions
• Most cell bodies of CN arise from brain stem (III-XII)
• Numbered according to their order of emergence in
the brain stem
• Six are critical for speech and hearing!!
CN for Speech and Hearing
- CN V: Trigeminal
- CN VII: Facial
- CN VIII: Auditory
- IX: Glossopharyngeal
- X: Vagus
- XII: Hypoglossal
Brain Imaging Classification
- Brain structure (anatomy)
- X-rays (i.e., CT)
- Imaging techniques (i.e., MRI)
- Brain function (physiology)
- Electrical measures
- Biochemical measures
- Physiologic measures
Computerized Tomography (CT)
• X-ray technique.
• Sensitive to tissue density:
• Denser tissue absorbs more radiation à
lighter image
• Brain CT:
• Skull is white (high density)
• Brain matter is gray (intermediate density)
• Cerebral ventricles are black (low density)
• Constructed from lots of scans as x-ray rotates around
head
• Used to define normal and abnormal structures:
• diagnose tumor, head trauma, degenerative disease,
stroke
• Advantages:
• Short imagine times
• Painless (and minimally invasive)
• Extremely accurate images
• Disadvantages:
• Radiation
Magnetic Resonance Imaging (MRI)
• Imaging technique
• Exposure to a very powerful magnet which changes
alignment of hydrogen atoms in organ cellular
structure
• Different tissues within the brain contain different
amounts of water (and hydrogen)—produces tissue
contrast
• Computer transforms information to representation of
structures
• Used to diagnose brain diseases and disorders
• Advantages:
• Does not use ionizing radiation
• Very high degree of spatial resolution
• Depicts anatomy in greater detail than CT: more sensitive and
specific for abnormalities within brain
• Disadvantages:
• Higher cost
• Long imaging times
Imaging Brain Function
Techniques are based on cerebral blood flow, cerebral
metabolism of O2 and glucose, & electrical properties
of neural function
All techniques depend on changing brain activity during
use. Whenever a task is conducted there are local
changes in neural function
Functional Magnetic Resonance Imaging
fMRI
• Measures brain activity by detecting associated changes
in O2 and blood flow
• Hemodynamic response: the increase in regional
blood flow:
• Neural activity uses O2 and requires increased blood flow
to replace depleted O2 levels
• Highlights regions of the brain linked to critical
functions such as speaking, moving, sensing, or planning
• Advantages:
• Safe and non-invasive
• Allows examination of changes in individual brain function
over time or during different activities
• Useful for rehabilitation (document recovery)
• Disadvantages:
• Slow scanning process
• Noisy scanner
Positron Emission Tomography (PET)
• Quantifies the distribution of a radioactive tracer in
brain
• Inhaled substance (oxygen, nitrogen, carbon, & fluoride)
• Eliminates from body in 6-24 hours
• Amount of tracer in area of interest will depend on
the regional cerebral blood flow (rCBF)—related to
neural activity
• More active, absorb more tracer
• Inactive, absorb less tracer
• Color-coded representation:
• Red = high levels of activity
• Purple/black = little/no activity
• Advantages:
• Short scan time
• Disadvantages:
• High radiation exposure
• Decreased spatial resolution compared to other
techniques
Electroencephalography (EEG)
Records the electrical potentials (activity) generated by
the brain via electrodes placed on the scalp
• Computerized techniques allow quantification of the
activity (qEEG)
• Analyzed by Fourier analysis, shows dominant
frequencies of brain activity
• Event-related potentials (or EP) are brain potentials in
response to a stimulus
EEG and EP
Advantages:
• Relatively inexpensive
• Excellent temporal resolution
• records brain activity in response to specific stimulus
• Disadvantages:
• Averages electrical brain signals, preventing precise
specification of underlying neural structures
Transcranial Magnetic Stimulation (TMS)
Magnetic field produced by coils placed on the head
creates a current & stimulates cortical neurons to fire
• Examines neurotransmission along nerve tracts
TMS
• Useful for evaluating and treating neurological
disorders e.g., Parkinson’s disease, Multiple Sclerosis
• Also useful for depression
• Advantages:
• Safe and noninvasive
• Disadvantages:
• Rare occurrence of induced seizures and syncope
(fainting)
Near-infrared spectroscopy
NIRS
Measures oxygenated and deoxygenated areas in the
brain with diodes (hemoglobin concentration changes
can be detected through the near infrared light)
NIRS
- Advantages:
- Portable
- Can be used with infants
- Some wireless instrumentation available
- Engage in functional activities
- Disadvantages:
- Only measures cortical areas
- Potentially painful
- Difficulty with individuals who have hypersensitivities
Brain Imaging Techniques in COMD
• Application for disorders of speech, language and hearing
disorders.
• Assists with diagnosis:
• Provides an index of brain function in neurological disorders
e.g., CVA, Parkinson’s Disease, Alzheimer’s Disease, MS, etc.
• Assist with treatment:
• Evaluate efficacy of treatment over time.
• Compare different
Current studies (NIRS)
• Stuttering • Concussion • Performance on attention and memory tasks before and after concussion was the same • Neural activation before and after concussion differed • Conversational Studies • Acoustic patterns • Neural patterns
Current studies
NIRS and Eye-tracking
26 Current studies (NIRS and Eye-tracking) • Agent Rest • Syntactic processing • Verbal working memory • Reading and Comprehension • Bilingualism • Different patterns of activation compared to bilinguals • Different patterns of activation depending on age of exposure to second language
Stuttering/Fluency Disorders
• PET, SPECT, qEEG have shown differences in rCBF
between non-fluent and fluent speakers
• Findings have suggested that a complex neural network
of structures does not function normally in non-fluent
individuals
Parkinson’s Disease (PD)
Brain imaging used to diagnose and treat PD. Also to
measure progression and severity of disease
• PET shows degeneration in substantia nigra (early
detection) and increased metabolism in basal nuclei
• fMRI shows reduced activation in the supplementary
motor area and motor cortex
• EP has been used to monitor cognitive changes associated
with PD
Outer Ear
- Pinna (or auricle):
• Flap on outside of head - External auditory meatus (or ear cannel)
• Tube leading from pinna to ear drum
Outer Ear: Pinna
• Made of flexible elastic cartilage, as well as a soft lobule (lobe) on inferior portion. • Attached to head via ligaments. • Primary function: • Direct sound waves into the ear canal • Secondary functions: • Assists with localization of sound (two pinnae) • Protects entrance to ear canal
Outer Ear: External Auditory Meatus
Leads from pinna to tympanic membrane.
• Made of bone (medial) and cartilage (lateral).
• Inside lined with layer of epidermis and lateral portion
contains glands that secrete cerumen and cilia.
• Protects middle and inner ear.
• Lubricates ear and protect insects entering.
• Moves dust and small particles out of the ear.
Tympanic Membrane (TM)
• Also known as ear drum.
• Thin, semi-transparent membrane separating outer and
middle ear.
• Concave shape, with tip (umbo) facing middle ear.
• Vibrates when sound (acoustic pressure) waves hit it.
• Converts pressure waves to mechanical vibration via
connection with malleus.
Middle Ear
1. Tympanic cavity (or tympanum) and epitympanic recess (or attic) 2. Ossicles: three small connected bones: Malleus Incus Stapes 3. Eustachian tube 4. Muscles Tensor tympani Stapedius Mi
