Speech Reading Guides 7&8

Advantages that result due to swallowing at lung volumes that are LARGER than the resting size of breathing apparatus, but still in midrange:

1. Postswallow expirations are easily driven by the repsiratory recoil pressure

2. No need to exert inspiratory muscular pressure to brake excessive positive recoil pressure that prevails at larger lung volumes

3. The abductors force exerted on the vocal folds by the descent of diaphragm is minimized

Difference between apnea and dyspnea

Apnea is brief period of breath holding, dyspnea is caused by apnea and is breathing discomfort

Range of time apneic interval usually lasts and what most of variability can be attributed to:

Typically 1 second (can be less or more), variables are bolus volume and variability in the onset of apnea relative to the eating or drinking event

Advantages of UES and intrinsic larynx muscles both being innervated by RLN of CN X

Strong neural link between actions that serve to protect the airway and actions that allow substances to pass into esophagus- COORDINATION OF NORMAL SWALLOW

Disadvantage of UES and pharynx muscles being innervated by RLN CN X

Damage to the recurrent branch of vagus nerve can have serious consequences for both voice production and swallowing

2 major regions within CNS that are responsible for the control of swallowing

Brainstem and cortical/subcortical areas

Sources of Afferent input that are critical to the generation of a normal swallow :

Info related to: muscle length and rate of length change, muscle tension, joint position and movement, surface deep pressures, surface deformation, temperature, taste, and noxious smell

Breathing behavior in single swallow

Single swallows are produced within a single breathing cycle (usually during the expiratory phase)

Swallowing in the supine position:

Hyoid bone moves a greater distance anteriorly, velum moves a smaller distance posteriorly, pharyngeal transport phase is LONGER, pharyngeal pressure is more positive, UES pressure reaches its nadir slightly earlier, bolus flows through UES faster, peristaltic waves in esophagus are slower and stronger, pressure in LES is higher, pressure in nasopharyngeal region is higher and more supine compared to more upright positions

Cortex

Visible surface tissue, the most complex and sophisticated part of the brain

Gyri

Ridges or hills of the cortex

Dips in between the gyri

Sulci or fissures (fissures means a particularly deep sulcus)

Main difference between brain of humans and brain of animals:

Humans have relatively deep and numerous sulci defining the cortical surface. MORE CORTICAL CELLS

Hidden cortical surface

2/3 is hidden . They are infoldings of the cortical surface , forming hidden walls of tissue that contribute to a greater volume of cortical cells in the human brain

Understand the size of cortical tissue devoted to different regions/structures of the body

Cells at the top of the cortex control the bottom part of the body; a disproportionate number of cells in the primary motor cortex are devoted to control of the structures that play a major role in speech production and swallowing

Location of Broca's area

Inferior frontal gyrus on the lateral surface of the left frontal lobe and immediately above the front end of the sylvian fissure

Role of Broca's area

Planning and organization of motor behavior required for speech production. Speech expression is controlled

Specific names of the descending projection tracts

Corticobulbar , corticospinal, corticothalamus

2 major somatosensory pathways for stimuli sensed below the neck

Posterior column-medial leminiscal tract and anterolateral tract

Posterior column-medial Leminiscal tract

Carries information on fine touch, vibration, and joint position

Anterolateral tract

Carries information on pain, temperature, and crude touch

Where do upper motor neuron lesions occur

Cortical motor neurons or in axons they issue prior to making synapses with motor neurons in the Brainstem or spinal cord

Where do lower motor neuron lesions occur

Those occurring in the nuclei of the Brainstem or motor cells of the spinal cord, or in the axons they issue and the peripheral nerves in which those axons travel , or even at the location of the nerve-muscle fiber connection

Results of upper motor neuron lesions

Result in muscles with excessive muscle tone while at rest and hypersensitive reflexes

Results of lower motor neuron lesions

Loss of muscle mass (wasting or atrophy), small muscle twitches visible to the naked eye (called fasciculations), and in some cases low muscle tone at rest .

In both upper and lower motor neuron lesions, the affected muscles tend to be

WEAK