Quiz 2: Neural Bases of Speech, Language and Hearing

What are the major landmarks on a typical neuron?

Cell body (soma), Neurites (thin tube extending from soma), Axon (efferent from cell body)

Dendrite, nucleus, axon, myelin sheath

What is the difference between neurons and neuroglial cells?

Neurons: process information, sense environmental changes, communicate changes to other nuerons.

Neuroglia: Non-nueral support cells

Astrocytes

star shaped, maintain ion balance around neurons, control exchange of materials between blood vessels and neurons.

Oligodendrocytes

Wrap their cytoplasmic processes around neurons to insulate them (myelin)

Microglia

Protective; functional; engulf/clear out microorganisms and debris

Ependymal cells

Line fluid filled cavities of the brain and spinal cord (often ciliated)

What are the four typical steps involved in the synapsing of a neuron?

1. In the presynaptic neuron, electrochemical signal (action potential) initiated with neuron that travels down axon to terminal (buton)

2. Impulse signals the release of chemicals (neurotransmitters) into synaptic cleft.

3. Postsynaptic neuron receives neurotransmitters.

4. Neurotransmitters trigger an action potential in post synaptic neuron.

What is an action potential?

The electric impulse, message delivery system, travels down axon

What are the stages of an action potential?

1. Resting potential

2. Action potential propagation

3. Resting potential returns

Divergence

numerous branchings of axons, increased opportunity for widespread neural impulses, impulses travel along branches to activate all its synapses.

Convergence

All neurons receive info from many other neurons, excitatory and inhibitory, both play large role in nervous system. The reason that the nervous system is able to process things quickly

What is primary vs. secondary neuronal damage?

Primary: neuronal loss, immediate dying of neurons from trauma/ damage

Secondary: degeneration of neurons after primary loss

In what situation are neurons most likely to regenerate? In what situation is this

not likely?

• Neurons lost through disease or trauma are likely not replaced.

• Axonal regeneration- likely occurs in the PNS when peripheral nerve is either crushed or compressed (but not severely damaged)

Anterograde Degeneration

disintegration of myelin sheath

Retrograde degeneration

dissoultion of endoplasm

Trophic effect regarding neurons

Neurons on the CNS can sustain one another.

What are the three categories of sensory receptors and what does each sense?

Exteroreceptors: sight, sound, smell, cutaneous sensation

Proprioceptors: deep somatic sensation beneath the skin

Interoreceptors: viscer; visceral pain and pressure

What is agnosia?

Inability to interpret/ recognize sensory information.

Visual agnosia

inability to recognize objects, colors, pictures

Auditory agnosia

inability to recognize speech/ non speech sounds

Tactile agnosia

inability to recognize objects by touch

Prosopagnosia

inability to recognize faces

How are somatosensory pathways organized

• Enter the CNS

• Cross at the midline

• Ascend to the contralateral sensory cortex

What do first order neurons do?

cranial or spinal nerves, synapse with second order neurons in gray matter of CNS

What do second order neurons do?

Cross the midline, ascends to 3rd order neurons in thalamus

What do 3rd order neurons do?

Ascends from thalamus to cortex.

What role does the thalamus play in sensation?

It is the relay station for sensory information as it travels towards the cortex.

1. Channels projections of sensory info from lower levels of the nervous system to specific cortical areas.

2. Integrates sensorimotor information from basal ganglia, limbic system, and cerebellum to primary and premotor cortices

3. Regulates functions of association cortices and cortically mediated cognitive functions.

What is the primary nerve for sensation in the oral cavity and face?

Trigeminal Nerve (V)

How do sensory receptors in the oral cavity help in speech production and control?

proprioceptive: oral muscles, joints of jaw, membranes of teeth

help with perception of speech and self-monitoring skills

Generally, how does the visual system work?

• Absorbs, projects light into the eyeball

• Transfers light into neural signals

• Send neural information to the brain to be processed

What are the 1st order neurons in the visual system?

Rods and Cones

What are the second order neurons in the visual system?

Bipolar cells

What are the third order neurons in the visual system?

Axons of ganglion cells

Temporal visual association areas

Help with facial recognition

What other important connections does the visual system have to help with integration?

It has connections with the limbic system to help with integration of new visual stimuli and past experiences (memory).

Generally, how does the auditory system work?

• Transfer of mechanical into neural energy

• Sound waves move the tympanic membrane

• Fluid vibrations in the inner ear

• Transfer neural impulses, sent to the brain

What are the 1st order neurons in the auditory system?

acoustic branch

What are the 2nd order neurons in the auditory system?

cochlear nuclei

What are the third order neurons in the auditory system?

MGB

When does auditory information from the left ear reach Wernicke’s area to be processed?

After reaching primary aud cortex in the right hemisphere.

How many pairs of cranial nerves do we have?

12

Cranial Nerve 1

I Olfactory: Smell, sensory

Cranial Nerve 2

II Optic: Vison, sensory

Cranial Nerve 3

III Oculomotor: innervation of muscles to move eyeball, pupil and upper lid, motor

Cranial Nerve Five

V Trigeminal, chewing sensation to face, teeth and anterior tongue, sensory and motor

Cranial Nerve Four

IV Trochlear, innervation of superior oblique muscle of the eye, motor

Cranial Nerve six

VI Abducens, abduction of the eye, motor

Cranial Nerve seven

VII facial, movement of facial muscles, taste salivary glands, motor

Cranial nerve eight

VIII Vestibular acoustic, equilibrium, hearing, sensory

Cranial nerve nine

IX Glossopharyngeal, taste, swallowing, elevation of larynx and pharynx, parotid salivary gland, sensation to posterior tongue, upper pharynx, motor and sensory

Cranial Nerve ten

X Vagus, taste, swallowing, elevation of palate, phonation, parasympathetic outflow to visceral organs, motor and sensory

Cranial nerve eleven

XI Accessory, turning head and shrugging of shoulders, motor

Cranial nerve 12

XII Hypoglossal, movement of tongue, motor

Which are the CNs for speech production and hearing? Which of these are most

important for speech production and swallowing?

V, VII, IX, X, XII

Hearing VIII

Which 2 CNs do not synapse with the brainstem on the way to the cortex?

Olfactory and Optic (I and II)