Peripheral Nervous System Flashcards
Cranial Nerves (43 cards)
Describe the association of cranial nerves with the brain.
There are 12 pairs of cranial nerves associated with the brain, with two attaching to the forebrain and the rest to the brain stem.
Explain the sensory function of the olfactory nerve.
The olfactory nerve is purely sensory and is responsible for the sense of smell, running from the nasal mucosa to the olfactory bulbs, where it synapses before terminating in the primary olfactory cortex.
Define anosmia and its causes.
Anosmia is the partial or total loss of smell, which can result from a fracture of the ethmoid bone or lesions of the olfactory fibers.
How do optic nerves function in vision?
Optic nerves, which are actually brain tracts, arise from the retinas, pass through optic canals, converge, and partially cross at the optic chiasma, continuing to the thalamus and then to the occipital cortex for visual processing.
What are anopsias and their relation to optic nerve damage?
Anopsias are visual defects that occur when there is damage to the optic nerve, resulting in blindness in the affected eye, or damage beyond the optic chiasma, leading to partial visual losses.
Describe the functions of the oculomotor nerve.
The oculomotor nerve is chiefly a motor nerve that controls four of the six extrinsic eye muscles, raising the eyelid, directing the eyeball, constricting the iris, and controlling lens shape.
Explain the innervation provided by the oculomotor nerve.
The oculomotor nerve provides somatic motor innervation to four eye muscles and parasympathetic innervation to the sphincter pupillae via the ciliary ganglion.
Describe the condition that occurs when the eye rotates laterally at rest.
This condition is known as external strabismus, where the actions of the two extrinsic eye muscles not served by cranial nerves III are unopposed, leading to lateral rotation of the eye.
Explain the symptoms associated with external strabismus.
Symptoms include a drooping upper eyelid (ptosis), double vision, and difficulty focusing on close objects.
How are cranial nerves numbered and named?
Cranial nerves are numbered I through XII and are named from rostral (front) to caudal (back).
What happens in oculomotor nerve paralysis?
In oculomotor nerve paralysis, the eye cannot be moved up, down, or inward due to loss of motor control over the eye muscles.
Describe the pathway of the optic nerve from the retina to the visual cortex.
The optic nerve fibers extend from the retinas, pass through the optic canals, converge at the optic chiasma, continue as optic tracts to the thalamus, and then project to the occipital visual cortex.
How does damage to the trochlear nerve affect vision?.
Damage to the trochlear nerve results in double vision (diplopia) and impairs the ability to rotate the eye inferolaterally.
How is Bell’s palsy treated?
Bell’s palsy is treated with corticosteroids.
Define the role of the abducens nerve in eye movement.
The abducens nerve is primarily a motor nerve that innervates the lateral rectus muscle, allowing for lateral movement of the eye.
What happens in abducens nerve paralysis?
In abducens nerve paralysis, the eye cannot be moved laterally, resulting in the eyeball rotating medially, a condition known as internal strabismus.
What is Bell’s palsy and its characteristics?
Bell’s palsy is characterized by paralysis of facial muscles on the affected side and partial loss of taste sensation, often developing rapidly.
Describe the function of the trigeminal nerve.
The trigeminal nerve supplies motor fibers for mastication and conveys sensory impulses from various areas of the face.
Explain trigeminal neuralgia and its causes.
Trigeminal neuralgia is characterized by excruciating pain caused by inflammation of the trigeminal nerve, often due to a loop of artery or vein compressing the nerve near its exit from the brain stem.
How is trigeminal neuralgia typically triggered?
Triggers for trigeminal neuralgia can include sensory stimuli such as brushing teeth or even a passing breeze hitting the face.
What treatments are available for trigeminal neuralgia?
Several drugs are used to treat trigeminal neuralgia, and in severe cases, traditional or gamma knife surgery may relieve the pain by moving the compressing vessel or destroying the nerve.
Describe the result of nerve destruction in the face.
Nerve destruction results in loss of sensation on that side of the face.
Define the three divisions of the trigeminal nerve.
The three divisions of the trigeminal nerve are Mandibular, Maxillary, and Ophthalmic.
Explain the role of the trigeminal ganglion.
The cell bodies of sensory neurons of all three divisions of the trigeminal nerve are located in the large trigeminal ganglion.
