cranial nerves Flashcards
1
Q
what is the structure of a nerve
A
- cordlike organ of PNS
- bundle of myelinated / un-myelinated peripheral axons enclosed by connective tissue
- CT: endoneurium, perineurium and epineurium (tough layer)
2
Q
how are nerves classified (2 ways)
A
- fibres: mixture of afferent and efferent fibres, and autonomic and somatic
- somatic afferent / somatic efferent
- visceral afferent / visceral efferent
- cranial or spinal
3
Q
what are afferent sensory receptors
A
- 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
4
Q
describe the different types of receptors classified by stimulus
A
- 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
5
Q
describe the different types of receptors classified by location
A
- 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
6
Q
describe the different types of receptors classified by structure
A
- 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
7
Q
what are efferent somatic motor and NMJs
A
- innervate skeletal muscle at NMJ (motor end plate)
- ACh diffuse across cleft, bind with molecules on sarcoma, contraction of muscle
8
Q
what are cranial nerves / the mnemonic to remember them and their function
A
- 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”
9
Q
describe cranial nerve 1
A
- 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
10
Q
what is olfaction physiology
A
- 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)
11
Q
describe cranial nerve 2
A
- 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)
12
Q
what is vision physiology
A
- 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
13
Q
describe the steps in the process of vision
A
- transmitters released from rod cone cells to communicated to bipolar cells in retina
- varying degrees of convergence occur (visual acuity)
- ganglion cell axons make up the optic nerve
- two optic nerves combine at optic chiasma, in front of brainstem
- travel in optic tracts to terminate in nucleus of thalamus (lateral geniculate body)
14
Q
describe cranial nerve 3
A
- 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
15
Q
describe cranial nerve 4
A
- trochlear (LR6)(SO4)3
- PF: motor (eye movements)
- O: midbrain
- PT: superior orbital fissure of sphenoid
- D: innervates extrinsic eye muscle superior oblique (SO)
