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Anat Exam 4: The PNS > PNS2 > Flashcards

PNS2 Flashcards

1
Q

What are SSA fibers? Give 3 examples?

A

SSA = Special Somatic Afferents
-Convey information pertaining to those SPECIAL SENSES which relate the Body to the External Environment. i.e. 1. Vision - from retina; 2. Sound - from cochlea; 3. Equilibrium - from labyrinth of the inner ear.

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2
Q

What are SVA fibers? Give 2 examples?

A

SVA = Special Visceral Afferents

  • Convey information related to those Special Senses associated with Ingestion of FOOD.
    i. e. 1. Smell; 2. Food.
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3
Q

What are SVE Fibers? What 4 Cranial Nerves have them?

A

SVE = Special VISCERAL* Efferents

  • Innervate SKELETAL MUSCLE derived from the Pharyngeal Arches.
    1. Trigeminal (CN V); 2. Facial (CN VII); 3. Glossopharyngeal (CN IX); 4. Vagus (CN X)
  • NOTE: GENERAL Visceral Efferents (GVEs) innervate smooth & cardiac muscle. GSAs are the fibers that innervate skeletal muscles throughout the rest of the body
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4
Q

Compare and contrast Lower Motor Neurons and Primary Sensory Neurons and how they relate to Cranial Nerves.

A
  1. Lower Motor Neurons are located in the Motor Group of Cranial Nerve Nuclei where they give rise to Efferent Fibers (GSE, SVE, GVE)
  2. Primary Sensory Neurons are located in Ganglia OUTSIDE the CNS where they give rise to Afferent Fibers that are project to secondary neurons in the dorsal gray of brain stem.
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5
Q

CN I - Olfactory “Nerve” carries Special Visceral Afferents (SVA) fibers mediating the sense of Smell from receptors located where? What are the parts of the olfactory nerve?

A

In the OLFACTORY EPITHELIUM.
-The sensation of smell travels olfactory receptors up through the Cribriform Plate to the Olfactory BULB, to the Olfactory Tract.

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6
Q

Pathology of what structures may impinge the olfactory nerve?

A

Pathology of either the underside of the FRONTAL LOBES or on the floor of the ANTERIOR CRANIAL FOSSA may interfere with normal olfaction by compressing CN I.

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7
Q

Olfactory bulbs lie on what structure? of what bone? In what part of the skull?

A

Olfactory Bulbs lie on the Cribriform Plate of the Ethmoid Bone in the Anterior Cranial Fossa.

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8
Q

T or F? The olfactory mucosa (epithelium) has a very limited distribution in Homo Sapiens?

A

True

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9
Q

What is the Olfactory Mucosa?

A

It’s the area where the Olfactory Receptors will be most dense.

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10
Q

Why is the term “Olfactory Nerve” actually a misnomer?

A

Because there really are two parts to the “olfactory nerve.” There is the PRIMARY OLFACTORY NEURONS found in the Olfactory Epithelium and there are SECONDARY OLFACTORY NEURONS found in the Bulb and Tract.
-Usually the Primary Olfactory (Sensory) neuron is referred to as BUNDLES of AXONS.

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11
Q

What important role do Olfactory Glands play?

A

Olfactory Glands keep the olfactory epithelium (mucosa) moist so that inhaled scents (aromtatic molecules or odorants) can be dissolved and “smelled”

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12
Q

What are Olfactory Cells?

A

They are the PRIMARY Sensory Neurons whose peripheral processes act as the Sensory RECEPTORS that convey signals to the olfactory axons.

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13
Q

The central processes of the olfactory cells, the OLFACTORY AXONS, pierce the cribriform plate in bundles on their way to the Bulb. Are the Olfactory Axons myelinated or unmyelinated?

A

UNMYELINATED

-The olfactory axons are unmyelinated.

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14
Q

CN I fibers are passed from the Bulb to the Tract to CNS Structures concerned with olfaction. What are these structures collectively called?

A

RHINENCEPHALON or “Nose Brain”

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15
Q

What lobe is the site of the Primary Olfactory Cortex?

A

The PIRIFORM LOBE

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16
Q

What are 4 Visceral Responses mediated by olfactory fibers that are not projected to the cortex but are instead projected, via the HYPOTHALAMUS, to the Autonomic Centers?

A
  1. Salivation
  2. Gastric Secretion
  3. Peristalsis
  4. Nausea
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17
Q

What type of head injury generally results in Lesions of CN I?

A

A-P Head Injuries = Head injury resulting from dramatic Anterior-Posterior direction (i.e. Whiplash).

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18
Q

What are the 3 general results of CN I lesions?

-If the Nerve roots are sheared in a particularly bad accident what is another possible injury?

A

Unilateral…

  1. Anosmia - Loss of smell
  2. Hyposmia - partial loss of smell
  3. Smell Distortion
    - If the nerve roots are sheared, the injury may result in CSF Leakage from the sub-arachnoid space, located b/t cribriform plate and bulb, to the nasal cavity resulting in a CSF RHINORRHEA. This CSF ‘runny-nose’ may also produce a metallic taste sensation due to taste buds in the oropharynx.
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19
Q

How do food odorants released while chewing reach the Olfactory Epithelium?

A

They climb posteriorly from the Pharynx through the Choanae, rather than through the nostrils.

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20
Q

What type of nerve fibers does the olfactory nerve, CN I, contain?

A

SVA Fibers. Carries sensory information from the nose to the cortex (rhinencephalon) and autonomic centers.

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21
Q

What type of nerve fibers does the Optic Nerve, CN II, contain?

A

SSA Fibers. Carry sensory information from the photoreceptors of the retina to the thalamus (lateral geniculate nucleus) and brainstem (midbrain) nuclei.

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22
Q

What are the photoreceptors of the retina?

A

Rods and Cones

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23
Q

How do Rods and Cones transduce light energy? How does this signal get to the Optic Nerve?

A

Rods and Cones convert light energy into an Electrical Signal, which passes to Bipolar Cells (the primary sensory neurons in the visual pathway) and then Ganglion cells. The axons of these Ganglion Cells form the Optic Nerve.

24
Q

What are bipolar cells?

A

The primary sensory neurons in the visual pathway.

25
Q

After coursing through the OPTIC CANALS, the Optic Nerves end Grossly at the level of what?

A

The OPTIC CHIASM, on the Chiasmatic Groove, where decussation of fibers occurs.
Note: Crossing fibers here are vulnerable to lesions of the pituitary gland and the ventral diencephalon.

26
Q

Why is the OPTIC NERVE (CN II) technically not a nerve?

A

It is actually a WHITE MATTER TRACT of the CNS. because

  1. Like CN I, it is comprised of axons of secondary (Ganglion axons), rather than primary (Bipolar Cells), receptor neurons.
  2. Upon leaving the LAMINA CRIBROSA the optic nerve is covered by CNS myelin (why called ‘white’), bathed in CSF, & ensheathed by the 3 mininges (dura, arachnoid, & pia).
27
Q

CN II is formed where & by what?

A

Optic nerve is formed at the OPTIC DISK by the Ganglion Cell Axons that converge there.

28
Q

Swelling of the Optic Nerve, PAPILLEDEMA, may result from increased pressure in what meningeal space?

A

SUBARACHNOID SPACE

29
Q

What branch of the Opthalmic Artery passes through the optic nerve into the eye? What is special about the branches of this branch?

A

The CENTRAL RETINAL ARTERY

-The branches of the central retinal artery are END ARTERIES.

30
Q

What halves of the retinas cross the midline at the Optic Chiasm?

A

The NASAL HALVES of the retinas, receiving inputs from the Temporal Visual Fields, cross the line at the Optic Chiasm.

31
Q

Most axons in each optic tract terminate where?

A

LATERAL GENICULATE NUCLEUS of the THALAMUS.

-Note: Geniculate b/c BENT - like bent knee

32
Q

Axons that don’t terminate in the Lateral Geniculate Nucleus go where? Why?

A

Some project to the Brainstem (Midbrain) Nuclei to provide visual input to reflex maintenace of Balance, Eye Position, & Control of Size of the Pupil.

33
Q

Visual inputs project to the PRIMARY VISUAL CORTEX surrounding the CALCARINE Fissure in what lobes of the brain?

A

The OCCIPITAL LOBES.

34
Q

Differentiate b/t Prechiasmatic, Chiasmatic, and Postchiasmatic lesions to CN II.
-A lesion in either of these sites will result in what?

A
  1. Prechiasmatic - Lesion to Retina or Optic Nerve.
    - Lesion –> Blindness in 1 eye
  2. Chiasmatic - Lesion to Optic Chiasm.
    - Lesion –> Tunnel Vision
  3. Postchiasmatic - Lesions to Optic Tract, LGN, or Optic Radiations.
    - Lesion –> Blindness on one side (note: not 1 eye)
35
Q

CN VIII - The Vestibulocochlear Nerve contains what type of nerve fiber? What is it’s job?

A

SSA Fibers that convey sensory input concerning Sound from the COCHLEA and Equilibrium from the Semi-Circular Canals of the VESTIBULAR SYSTEM. Note: Name of nerve (vestibulocochlear) tells you what systems it interacts with!

36
Q

The Vestibulocochlear nerve arises from the sulcus b/t the Pons and the Medulla and travesl laterally at the Cerebello-Pontine Angle to enter what skull foramena?

A

The INTERNAL ACOUSTIC MEATUS.

Note: The internal acoustic meatus also transports the facial nerve CN VII.

37
Q

Within the Internal acoustic meatus what is the relative positions CNs VII and VIII?

A

CN VII lies w/in the groove separates the vestibular and cochlear divisions of CN VIII.

38
Q

Acoustic Neuromas compromise acoustic perception by compressing what nerves?

A

CN VII and CN VIII as they enter the Internal Acoustic Meatus

39
Q

In what bone of the skull are the organs of hearing and balance embedded in?

A

The Petrous part of the TEMPORAL BONE. “Petrous Pyramid.”

Note: Semi-circular canal lies in the Arcuate Eminence on top of the petrous pyramid

40
Q

The interval separating the Membranous Labyrinth and the Bony Labyrinth is filled with what CSF like fluid?

A

PERILYMPH

41
Q

The membranous labyrinth contains what type of fluid?

A

ENDOLYMPH

42
Q

The membranous Labyrinth is divided into what 3 parts?

A
  1. Utricle & Saccule
  2. Semicircular Canals (Sight of Vestibular innervation)
  3. Cochlear Duct (Sight of Cochlear innervation)
43
Q

The Cochlear Nerve carries the SSA fibers for hearing. It is composed of the Central Processes of Neurons in the What?

A

The cochlear nerve is composed of the Central Processes of Neurons in the SPIRAL GANGLION that is within the Cochlea.

44
Q

What type of fluid is contained in the 3 Scalas of the Cochlia (Scala Vestibuli, Scala Media & Scala Tympani)? What role does each Scala play?

A
  1. Scala Vestibuli: Contains PERILYMPH. It is the Perilymph in the scala vestibuli that transmits fluid waves, caused by the stapes moving in & out of the Oval Window, that vibrates the Basilar Membrane of the ORGAN OF CORTI, stimulating the hair cells in the Cochlear Duct.
  2. Scala Media = Cochlear Duct. Contains ENDOLYMPH. Also contains Organ of Corti, which stimulates the hair cells.
  3. Scala Tympani: Contains PERILYMPH. The perilymph in the Scala Tympani is responsible for dampening vibrations passes by the basilar membrane of the Organ of Corti.
45
Q

The Organ of Corti, w/in the Cochlear Duct, stimulates HAIR CELLS that do what?

A

The Hair Cells transmit action potentials to Bipolar Neurons whose Cells Bodies are in the SPIRAL GANGLION.

46
Q

What is the PLACE PRINCIPLE?

A

The Place Principle states that stimulation of hair cells in different areas along the basilar membrane results from different frequencies of sound. i.e. High pitch sound stimulate hairs at the base of the cochlea and low pitch sounds at the apex.

47
Q

The cochlear nuclei are TONOTOPICALLY organized. What does this mean? What signals are transmitted in the Anterior and Posterior Cochlear Nuclei?

A

Tonotopically means the cochlear nuclei are organized by the frequency of the sound signals they carry.

  • Anterior Cochlear Nuclei has LOW Frequency signals
  • Posterior Cochlear Nuclei has HIGH Frequency signals
48
Q

Acoustic Inputs follow the lateral sulcus and eventually project to where for final processing?

A

Acoustic inputs project to cortex in the TEMPORAL LOBE.

49
Q

Processing of Acoustic Imports begins, before reaching the final destination of the temporal lobe, in the Brainstem. What kind of processing happens in the brainstem?

A

Time of Arrival and Intensity is analyzed in the brainstem. Differences b/t left and right ears are analyzed allowing localization of sound sources. Also causes Stapedius and Tensor Tympani muscles to tense to protect cochlea from loud sounds.

50
Q

What role do the Stapedius and Tensor Tympani Muscles play in protecting the Cochlea?

A

The Stapedius and Tensor Tympani muscles are attached to the Stapes and Malleus respectively in the middle ear. Thanks to Brainstem Pathways, the muscles contract reflexively to protect the cochlea from loud sounds and decrease the volume of one’s own speech.

51
Q

What is the responsibility of the Vestibular Nerve?

A

Controls Posture, Balance & Equilibrium.

52
Q

What is the Vestibular Nerve composed of?

A

Central Processes of Bipolar Neurons in the VESTIBULAR GANGLION.

53
Q

OTOLITHIC ORGANS within the Maculae of the Utricle and Saccule detect what?

A

Otolithic Organs detect linear acceleration and motion due to Gravity and translational movement. This sensory information is conveyed from the MACULAE to the Vestibular Ganglion.

54
Q

SEMICIRCULAR CANALS detect what information that is conveyed from the AMPULLAE to the Vestibular Ganglion?

A

Semicircular Canals detect changes in angular motion and rotary acceleration of the head in any direction relative to the vertical during quiet stance. This info is then conveyed from the ampullae to the Vestibular Ganglion

55
Q

What are 3 causes and 6 symptoms of CN VIII Lesions?

A

Causes
1. Viral Labyrinthitis (middle ear infection)
2. Meniere’s Disease (imbalance of endolymph)
3. Acoustic Neuroma (benign tumor of Schwann Cells)
Symptoms
1. Sensorineural Deafness (Specifically related to Cochlear Nerve defects)
2. Tinnitus (Ringing, whistling or boomin in ear
3. Dizziness
4. Vertigo (false perception of motion)
5. Nausea & Vomiting
6. Nystagmus (rhythmic oscillation of the eyeballs) producing OSCILLOPSIA (=jumping of visual env’t)

Anat Exam 4: The PNS (7 decks)

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