Neuro 2 Flashcards
Where are the sympathetic cell bodies located?
T1-L2 spinal ganglia
What does the sympathetic NS used as preganglionic neurotransmitter & what is the receptor for this?
ACh
Nicotinic cholinergic receptors
What does the sympathetic NS used as postganglionic neurotransmitter & what is the receptor for this?
Adrenaline
Adrenergic
Where are the parasympathetic cell bodies located?
Sensory ganglia of cranial nerves 3,7,9,10 & spinal nerve ganglia S2-S4
What does the parasympathetic NS use as its preganglionic & postganglionic neurotransmitter and what are the receptors for this?
ACh
Cholinergic
Pre = nicotinic cholinergic
Post = muscarinic cholinergic
What are the 3 main types of neurones?
Unipolar - cell body as projection from axon
Bipolar - cell bodies in middle of axon
Multipolar - cell bodies in centre of dendrites
What are the 3 functional types of neurons?
Afferent - sensory to CNS
Efferent - CNS to tissues
Interneurons - within CNS
What is the CNS myelinated by?
Oligodendrocytes (type of glial cell)
What is the PNS myelinated by?
Schwann cells
What is the purpose of myelination?
Acts as insulating later to prevent movement of Na+ & K+ across axon
Nodes of Ranvier act to propagate action potential faster by saltatory conduction
What moves substances along an axon?
What are the 2 proteins involved in transport & in which direction do they move substances?
Microtubules & proteins
Microtubules made from proteins
Kinesins - transport substances away from cell body (anterograde transport)
Dyneins - transport substances towards cell body (retrograde transport)
What are the 4 main types of glial cell?
Oligodendrocytes - myelination of CNS
Astrocytes - BBB, role in control of brain ECF composition, metabolically support neutrons
Microglia - macrophage like
Ependymal cells - line ventricles & regulate production of CSF
What is the refractory period of an action potential?
The period immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation due to Na+ channels already being open
What is the purpose of a refractory period?
To insure the impulse travels in only 1 direction
What is the speed of an action potential determined by?
Axon diameter
Myelination
What are the 2 structures of the external ear?
Auricle
External acoustic meatus
Where does the middle ear lie?
Within the temporal bone
What are the 4 main parts to the middle ear?
Tympanic membrane
Auditory ossicles - malleus, incus, stapes
Muscles (contract to protect from loud noises) - tensor tympani, stapedius
Auditory tube - middle ear to nasopharynx, equates pressure
What is the tensor tympani innervated by?
Mandibular, CNV3
What is the stapedius innervated by?
Facial, CNVII
Where does the inner ear lie?
Within the petrous part of the temporal bone
What are the 3 main parts of the inner ear?
Bony labyrinth - bone cavities filled with perilymph
Membranous labyrinth - ducts within bony filled with endolymph
Oval window
What are the 3 parts of the bony labyrinth?
Vestibule - central part
Cochlea - houses cochlear duct
Semicircular canals - contain semicircular ducts
What does the spiral lamina do?
Projection from centre of cochlea that divides cochlea into 2 chambers
Scala vestibuli superiorly
Scala tympani inferiorly
What are the 2 parts of the membranous labyrinth?
Vestibular system - semicircular ducts, saccule, utricle
Cochlear duct
What is the purposes of the organ of Corti?
Conversion of pressure changes in cochlea into electrical impulses sent to the brain
What are the differences between the region of the cochlear duct that experiences maximum displacement according to frequency?
Higher - vibration of part closest to oval window
Lower - vibrations travel further along scala vestibule & vibrate more distal sections
What are the hair cells?
Mechanoreceptor cells that have hair-like projections from the top of them (stereocilia)
How do vibrations cause an electrical impulse?
- Stereocilia in contact with tectorial membrane that overlies organ of Corti & remains stationary during vibrations
- Pressure waves cause displacement of basilar membrane
- Hair cells move & sterocilia bend
- Tip links between ends stretched
- Physically opens mechanically-gated ion channels
- Influx of K+ (surrounding endolymph is K+ rich)
- Depolarisation
- Voltage gated Ca2+ channels near base open
- Glutamate released into space between hair cell & afferent neutron fibres
- Form cochlear branch of CNVIII
What is the auditory pathway?
Internal acoustic meatus > ipsilateral cochlear nucleus complex > trapezoid body > contralateral superior olivary nucleus > lateral lemniscus > inferior colliculus > medial geniculate body > primary auditory cortex
I’M AUDITORY
How do the semicircular canals detect acceleration?
The canals move & the endolymph doesn’t
Inside surface of canals move against fluid
Bending of sterocilia
Stimulation of afferent neurons
What are the sterocilia in the semicircular canals ensheafed by?
Cupula, a gelatinous mass
What makes the hair cells more easily subject to gravity in the utricle & saccule?
Calcium carbonate crystals, otoliths
What 3 nuclei make up the vestibular nuclei?
Medial - semicircular canal
Superior - semicircular canal
Lateral - utricle & saccule
What is the function of the basal ganglia?
Controls movements by facilitating & inhibiting
What do the direct & indirect pathways do?
Direct - make & maintain movements
Indirect - inhibits & prevents movements
What are 2 disorders of the basal ganglia?
Parkinson’s disease (not enough dopamine)
Huntington’s disease (too much dopamine)
What is a motor end plate?
A region of muscle fibre’s plasma membrane that lies directly beneath an axon’s terminal plasma membrane
What is a neuromuscular junction?
Junction of axon terminal & motor end plate
What is the difference between synapses & NMJs?
All action potentials in motor neurone usually trigger an AP in muscle fibres
All NMJs are excitatory
What extra-ocular muscles originate from the common tendinous ring?
Rectus x4
Superior oblique
What are the 4 stages of an action potential?
1) resting potential = Na+/K+atpase pump pumps 3Na+ out & 2K+ in; some K+ diffuses out
2) depolarisation = stimulus causes some Na+ channels to open; Na+ influx
3) repolarisation = some K+ channels open & Na+ channels close; K+ diffuse out
4) hyperpolarisation = K+ slow to close; overshoot; helps refractory period
What is a synapse?
A junction between 2 neurons where the electrical activity in the presynaptic neuron influences the activity in the post-synaptic neuron
What are the 2 types of synapse?
Chemical - excitatory, inhibitory, modulatory
Electrical
What is convergence? (synapse)
Many presynaptic neurons influencing one postsynaptic neuron
What is divergence? (synapse)
One presynaptic neurone influences many postsynaptic neuron
What are the 7 stages of transmission across a synapse?
1) AP depolarises pre-synaptic axon terminal membrane
2) Na+ voltage-gated channels open & influx
3) Ca2+ channels open & influx
4) synaptic vesicles fuse with presynaptic axon terminal & release contents by exocytosis
5) neurotransmitters in synaptic cleft & diffuse across
6) bind to receptor proteins on post-
7) ligand gated ion channels open & propagate AP
What are 3 ways of neurotransmitter termination?
Reuptake by astrocyes/presynaptic terminal
Destroyed by enzymes
Diffuse away from site