Laryngeal Neuroanatomy Flashcards
laryngeal function is controlled by..
-PNS and CNS
PNS
cranial and spinal nerves
CNS
brain and spinal cord
white matter
transmits
grey matter
processes
the cortex
CNS
-outer covering of brain formed by nerve cell bodies
-grey matter
-divided into lobes by central sulcus and lateral fissure
-control of all voluntary movement is located in frontal lobe
-
important areas involved in the initiation, planning, and sequencing of all movements:
- primary motor cortex
- premotor cortex
- supplementary motor area
sends impulses to mms
primary motor cortex
planning, organization of movements
premotor cortex and supplementary motor area
cerebrum
CNS
- mass of what matter that forms the bulk of the brain
- consists of many nerve pathways that go up to the cortex and down to other areas
areas of grey matter within the cerebrum
- basal nuclei
- thalamus
- hypothalamus
basal nuclei structure
- clusters of cell bodies
- grey matter
- putamen, globus pallidius, caudate
basal nuclei function
- act as an inhibitory complex for excessive movements
- refines and smoothes movement by inhibiting excessive motor impulses from cortex
thalamus
- area of grey matter made of many different clusters of nuclei
- receives motor nerve projections from BG, cerebellum, cortex
- receives sensory info for every sense except smell
why is thalamus important for sensory integration?
- if we were aware of all sensory input, it would be too much to process
- distracting
- involved with consciousness, alertness, integration of emotional expression into motor activity (connected to limbic system)
cerebullum integrates and regulates…
- movements initiated in other parts of motor system
- contributes to smooth movements
- involved in regulation of balance, posture, muscle tone, coordination of mms groups
Similarities and differences cerebrum vs cerebellum
- both have a cover of grey matter (cerebellum has regular cover, cerebrum has sulci and gyro)
- insides both made of white matter with deep grey matter nuclei
- cerebellum is divided into 3 lobes, 2 hemispheres connected by vermis
aspects of movement regulated by cerebellum
- force
- speed
- range
- timing
- direction
- amount of displacement
periaqueductal grey (PAG) structure
- around liquid grey matter
- diffuse area of grey matter surrounding cerebral aqueduct
- part of ventricular system of brain
- connects 3rd and 4th ventricle
- filled with CSF
- connected to nucleus retroambiguus (NRA)
NRA neurons innervate mms of
tongue, pharynx, soft palate, exhalation, larynx
PAG function
- coordinates basic respiratory and laryngeal motor patterns necessary for speech
- involved in expression of emotion (linked to limbic lobe)
damage in PAG
- results in inability to form a sound (mutism)
- inability to form intent to speak
corticospinal tract (CST)
cortex directly to spine
- arises from areas in the frontal and parietal lobes
- fibers run ipsilaterally primarily
where does CST decussate
pyramids of medulla
CST fibers
80% cross to contralateral side
20% run ipsilaterally
corticobulbar tract (CBT) corticonuclear
cortex to motor nuclei fo specific cranial nerves
together CST and CBT form and control…
the direct/pyradmidial system
-controls fine skilled voluntary movements
damage to CST/CBT
results in weakness, spasticity to the point of paralysis (maybe)
indirect/extrapyramidial tract
circuitous pathway that extends from cortex to brainstem and spinal cord
- interconnected with basal ganglia and cerebellum
- multisynaptic=interconnected with other brain structures
indirect/extrapyramidial tract function
serves to smooth and refine voluntary movement originating in the cortex
indirect/extrapyramidial tract damage
causes excessive movements (PD)
-ticks, tremors, rigidity
pryamidal and extrapyramidal systems together form…
upper motor neuron (UMN)
spinal and cranial nerves form…
the lower motor neuron (LMN)
-aka final common pathway because all the info converges at spinal and cranial nerves
3 branches of vagus nerve important for voice
- pharyngeal
- superior laryngral (SLN)
- recurrent laryngeal (RLN)
pharyngeal branch
innervates mms of velum
SLN
internal (sensory) and external (motor) branches
-innervates cricothyroid
RLN
innervates thyroarytenoid, cricoarytenoid, PCA, and IAs
- asymmetrical left and right sides
- right side loops around subclavian artery and goes up again
- left side loops around aorta
vagus nerve damage
longer on left side (more susceptible to damage)
-congestive heart failure can compress nerves causing some dysphonia, affecting vocal function
laryngeal reflexes
- important for airway protection
- sensory nerve endings: mucosal layers, joints, mms
receptors respond to different stimuli:
and react by…
- touch
- movement
- vibration
- change in air pressure
- chemicals
-initiating tight reflexive closure of laryngeal valves protecting the airway (cough)
two systems controlling vocalization
CBT to nucleus ambiguus (NA)
- allows fine control of VOLUNTARY movements
- important for purposeful speech and voicing
- pathway is not present in other primates
emotional pathway
- nerve fibers project between the limbic system>PAG>NA
- involved in emotional vocalizations: laughter, crying, screaming, coughing
- shared pathways with other primates
