cranial nerves Flashcards Preview

HLTH1000 > cranial nerves > Flashcards

Flashcards in cranial nerves Deck (29):

what is the structure of a nerve

- cordlike organ of PNS
- bundle of myelinated / un-myelinated peripheral axons enclosed by connective tissue
- CT: endoneurium, perineurium and epineurium (tough layer)


how are nerves classified (2 ways)

- fibres: mixture of afferent and efferent fibres, and autonomic and somatic
- somatic afferent / somatic efferent
- visceral afferent / visceral efferent
- cranial or spinal


what are afferent sensory receptors

- specialised to respond to change in environment (stimuli)
- results in graded potentials that trigger nerve impulses
- impulse sent to brain where sensation (awareness) and perception (interpretation) occurs


describe the different types of receptors classified by stimulus

- mechano: respond to mechanical force, touch, vibration, stretch, pressure, wall of BV (pressure)
- thermo: changes in temp, sense heat or cold not both
- photo: respond to light (changes in intensity), in retina, made up of cone (body) and rod (projection)
- chemo: chemical changes, blood composition (pH, O2, CO2) - carotid / aortic bodies
- nocic: damaging / 'potential' damaging, extreme temp / pressure, irritating chemicals , do not adapt


describe the different types of receptors classified by location

- extero: stimuli outside body / environment, touch, pressure, pain, temp, special senses
- intero: stimuli arising in body, chemical, tissue stretch, temp, internal viscera / BV
- proprio: stimuli within body, body movement / position, stretch, skeletal muscle, tendons, joints


describe the different types of receptors classified by structure

- general sense: tactile sensation, pressure, stretch, vibration, temperature, pain, modified dendritic ending of sensory neurons, non-encapsulated (free nerve ending, thermo / noicic), encapsulated (nerve ending enclosed in capsule, mechano)
- special sense: vision, hearing, equilibrium, smell, taste, complex sense organs


what are efferent somatic motor and NMJs

- innervate skeletal muscle at NMJ (motor end plate)
- ACh diffuse across cleft, bind with molecules on sarcoma, contraction of muscle


what are cranial nerves / the mnemonic to remember them and their function

- attach to brain and pass through foramen of skull, 1-12
- primarily serve head and neck structures (vagus extends into abdominal / thoracic cavity)
- mixed: both sensory / motor, some have just one
- C1-2: attach to forebrain
- C3-12: attach to brainstem
- nerves: “O, O, O, To Touch And Feel A Girl’s Vagina, Ah Heaven!”
- function: “Some Say Marry Money; But My Brother Says Big Boobs Matter Most”


describe cranial nerve 1

- olfactory nerve
- PF: special sensory (smell)
- O: olfactory bulbs and olfactory cerebral cortex
- PT: olfactory foramina in cribriform plate of ethmoid
- D: receptors of olfactory epithelium
- epithelium: spans 2cm2 each side of nose, extremely sensitive, terminate with cilia, nociceptors
- P: air in nasal cavity, chemicals trapped by mucous, bind with specific receptor, become active, message sent to mitral cell, to CNS, travels to olfactory tract. cerebral cortex


what is olfaction physiology

- odour: 100's of chemicals, 1 stronger = more odour molecules
- cross mucosal layer, bind work via G coupled activation (triggers depolarisation etc)
- smell: dependent on pattern of activation of olfactory receptor neurons
- mitral cell: olfactory tract, terminate in olfactory cortex / limbic system (danger = fight / flight, appetising = salivation)


describe cranial nerve 2

- optic nerves
- PF: special sensory (vision)
- O: diencephalon (thalamus), synapse via optic chiasma
- PT: optic canals of sphenoid, converge, partially cross at optic chiasma (contralateral)
- D: retina of eye
- P: light (posterior retina), nerve fibres / optic nerve stimulated, merge together in optic chiasma, optic tract, bind to lateral geniculate nucleolus of thalamus, optic radiation to visual cortex (aware of vision)


what is vision physiology

- dominant sense (70% of all sensory receptors in eyes)
- nearly 1/2 of cerebral cortex = visual information
- rod = dim light
- cone = big light, nocturnal vision
- bipolar cell: communication with rod and cone cells, connected to and activates ganglion
- provide protection, cushion of fat around bony orbit
- accessory structures: eyebrows, eyelids, conjunctiva, lacrimal apparatus, extrinsic eye muscles


describe the steps in the process of vision

1. transmitters released from rod cone cells to communicated to bipolar cells in retina
2. varying degrees of convergence occur (visual acuity)
3. ganglion cell axons make up the optic nerve
4. two optic nerves combine at optic chiasma, in front of brainstem
5. travel in optic tracts to terminate in nucleus of thalamus (lateral geniculate body)


describe cranial nerve 3

- oculomotor (LR6)(SO4)3
- PF: motor (eye movements), extrinsic eye muscles, adjusts pupil (sphincter pupillae, PS), lens shape / focusing of eye (ciliary muscle)
- O: midbrain
- PT: superior orbital fissures of sphenoid
- D: somatic motor (extrinsic) and visceral motor (intrinsic)
- extrinsic muscles: innervate superior rectus (SR), inferior rectus (IR), medial rectus (MR), inferior oblique (IO- elevation, superior / lateral movement extorsion)
- levator palpebrae superiorois: innervation, moves upper eyelid


describe cranial nerve 4

- trochlear (LR6)(SO4)3
- PF: motor (eye movements)
- O: midbrain
- PT: superior orbital fissure of sphenoid
- D: innervates extrinsic eye muscle superior oblique (SO)


describe cranial nerve 5

- trigeminal (largest CN)
- 3 divisions: ophthalmic (V1), maxillary (V2), mandibular (VS)
- PF: mixed (sensory / motor)
- O: sensory nuclei in pons
- PT: V1 (superior orbital fissure), V2 (foramen rotundum), V3 (foramen ovale)
- D: V1 (S, cornea, nasal cavity, forehead, eyelid, eyebrow, nose), V2 (S, lower eyelid, upper lip, gums, teeth, cheek, nose, palate, pharynx), V3 (B, lower gums, teeth, lips, palate, tongue)


describe cranial nerve 6

- abducens (LR6)(SO4)3
- PF: motor (eye movements)
- O: pons
- PT: superior orbital fissure
- D: primary innervation of lateral rectus muscle (abduct)
- damage = cross eyed


describe cranial nerve 7

- facial
- PF: mixed (sensory / motor)
- O: extends from pons nuclei
- PT: internal acoustic meatus to canals leading to stylomastoid foramina
- D: S (taste, anterior 2/3 of tongue), M (facial expression, proprioception, lacrimal (tear / nasal mucous gland)
- P: pons, temporal bone, runs within bone, exits stylomastoid foramen into 5 major branches


what are the neural codings for taste

- humans: localisation of receptors = some regions are more sensitive to certain tastes
- receptors: communicate with single afferent system, perception of taste = complex
- bitter - posterior
- sour - lateral
- sweet - central / anterior
- salty - lateral / anterior


describe the sensation of taste

- primary sense organ
- taste buds: 10000 in lingual papillae (projections), bud = 40-100 epithelial cells
- sweet (sugars, alcohol, AA)
- salt (metal ions)
- sour (hydrogen ions)
- bitter (alkaloids, quinine, nicotine)


what is the gustatory pathway (tongue)

- facial nerve (anterior 1/3) and glossopharyngeal (posterior 2/3)
- solitary nucleus of medulla (PsNS = saliva / gastric secretion)
- thalamus to gustatory cortex of parietal lobes / limbic


what are facial nerve disorders

- bells palsy
- facial nerve affected by infections (herpes simplex 1), tumours and injuries
- unilateral facial paralysis, drooping eye / mouth, loss of nasolabial fold, tears / saliva drip, some loss of taste sensation
- not permanent, generally resolves itself depending on cause


describe cranial nerve 8

- vestibulocochlear (auditory)
- PF: special sensory nerve of balance / equilibrium (vestibular) and hearing (cochlear)
- O: vestibular and cochlear nuclei of pons and medulla oblongata
- PT: internal acoustic meatus of temporal bones
- D: monitor receptors of internal ear


describe the auditory pathway to brain (right)

- not all fibres from each ear cross over to other side of brain, impulses from both ears
1. sound waves vibrate tympanic membrane, auditory ossicles vibrate = amplify pressure
2. impulses go to cochlear duct vibrating basilar membrane / deflecting hair
3. spiral ganglion of cochlear nerve transmit to brainstem
4. synapses occur at 2 cochlear nuclei (medulla)
5. axons go to lateral lemniscus to inferior colliculus (midbrain)
6. travels to and synapse at MGN (medial geniculate nucleus) of thalamus
7. travel to primary auditory cortex = awareness of sound


describe cranial nerve 9

- glossopharyngeal
- PF: mixed
- O: medulla oblongata
- PT: jugular foramina (between occipital / temporal)
- D: S (posterior 1/2 of tongue), M (swallowing muscles, parotid salivary gland)


describe cranial nerve 10

- vagus ('wanders' into thoracic / abdominal cavity, heart and lungs)
- PF: mixed, widely distributed
- O: medulla oblongata
- PT: jugular foramina (between occipital / temporal)
- D: S (pharynx, auricle, external acoustic meatus, diaphragm, visceral organs) M (palate, pharynx, digestive, respiratory, cardiovascular), carotid and aortic bodies


describe cranial nerve 11

- accessory
- PF: motor (neck / upper back)
- O: motor nuclei of spinal cord and medulla
- PT: jugular foramina (between occipital / temporal)
- D: internal branch (muscles of palate, pharynx, larynx) and external branch (sternocleidomastoid / traps)


describe cranial nerve 12

- hypoglossal
- PF: motor (tongue)
- O: motor nuclei of medulla
- PT: hypoglossal canals of occipital bone
- D: inferiorly to tongue, extrinsic muscles of tongue, proprioceptor impulses (chewing, swallowing, speech)


list the 12 cranial nerves

- olfactory
- optic
- oculomotor
- trochlear
- trigeminal
- abducens
- facial
- vestibulocochlear
- glossopharyngeal
- vagus
- accessory
- hypoglossal