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
What are glutamate & GABA in the brain?
Neurotransmitters
Glutamate - excitatory
GABA - inhibitory
What is the definition of pain?
An unpleasant sensory & emotional experience associated with actual or potential tissue damage
Define referred pain
Sensation of pain is experienced elsewhere to where the stimulus is
What are 2 classifications of pain relating to time?
Acute = <12 weeks, typical Chronic = >12 weeks, longer than expected for stimulus
What are the 2 types of chronic pain?
Cancer
Non-cancer
What are 2 other classifications of pain?
Neuropathic = pain caused by damage/disease affecting somatosensory NS Nociceptive = pain caused by stimulus damaging tissues that is detected by nociceptors, non-neural tissue
What is the method of feeling pain?
- Nociceptors stimulated in an injury
- Tissue damage releases bradykinin & prostaglandin E2, which reduce the nociceptive threshold & increases sensitivity to stimuli
- Nociceptor afferent nerves release substance P, a neurotransmitter that causes long lasting excitatory post-synaptic potential to help sustain the effect of noxious stimuli
Where does the process of pain begin & what tracts does it involve?
Dorsal horns
Lateral spinothalamic tracts
What is a nociceptor?
A sensory neutron found in any tissue capable of experiencing the sensation of pain
What is analgesia?
Selective suppression of pain without any effect on consciousness
eg paracetamol
Doesn’t eliminate sensation
What is an anaesthetic?
Substances which induce insensitivity to pain
Reversible loss of sensation
What are the differences between A delta and C fibres?
A delta - mechanical & thermal; thinly myelinated; larger diameter; sharp acute specific pain; faster
C - mechanical & thermal & chemical; non-myelinated; smaller diameter; diffused dull later pain; slower; 70% of nociceptive fibres
What is periaqueductal grey?
Grey matter around the cerebral aqueduct
Receives input from cortical & sub-cortical areas
Modulates afferent noxious transmission
Primary control centre for descending pain modulation
Has opioid receptors - can result in analgesia
What is the area postrema?
Part of medulla outside BBB
Can detect toxins & act as vomit inducing centre
Densely vascularised without tight junctions
What is the Melzack-Wall pain gate theory?
Non-painful input closes the ‘gates’ to painful input which therefore prevents pain sensation from travelling to the CNS
eg massage, ice packs
Where are the 4 main areas of pain recognition?
Thalamus
Somatosensory cortex
Insula cortex (in lateral sulcus, judges degrees of pain, subjective)
Periaqueductual grey
How do opoids produce their effects?
Occupy receptors on pre-synaptic neurones to cause an inhibitory membrane potential & prevent the release of substance P
What are endorphins?
Naturally occurring peptides that have opiate like effects
What is substance P
Neurotransmitter used for transmission of pain information into CNS
What is a motor unit?
A single alpha neutron & all of the muscle fibres it innervates
What is a motor neurone pool?
A collection of motor neurone innervating a single skeletal muscle
What does a golgi tendon detect?
Changes in muscle tension
What are golgi tendons innervated by & what are they made of?
Sensory 1b neurons
Network of collagen fibres inside a connective tissue capsule
What does a muscle spindle detect?
Stretch of a muscle
What are muscle spindles innervated by & what are they made of?
Sensory 1a neurons
Intrafusal fibres
What is Brown-Sequard syndrome?
Hemisection of spinal cord
What are the symptoms of Brown-Sequard syndrome?
Loss of contralateral pain & temperature (spinothalamic)
Loss of ipsilateral motor & fine touch (descending motor tracts, DCML)
What is the visual pathway?
Eyes > optic nerve > optic chasm > optic tract > lateral geniculate nuclei > optic radiations > primary visual cortex
Which visual fields cross over?
Nasal
What is Meyer’s loop
Travels inferiorly to Baum’s loop through temporal lobe
Carries information from inferior retina (superior visual field)
What lies within the outer eye? (2)
Cornea (clear, protective, refraction)
Sclera (tough, attachment for muscles)
What lies within the middle eye? (3)
Iris (pupil) Ciliary body (produces aqueous humour, alters shape of lens) Choroid plexus (blood supply)
What lies within the inner eye? (1)
Retina (transduction of light)
What are the 10 layers of the retina from superficial to deep?
1) internal limiting membrane
2) nerve fibre (axon of ganglions)
3) ganglion cell
4) inner plexiform
5) inner nuclear
6) outer plexiform
7) outer nuclear
8) external limiting membrane
9) photoreceptor
10) retinal pigment epithelium
What are the differences between rod & cone cells?
Rods - light, more abundant, better sensitivity
Cones - colour & visual acuity
What is the levator palpebral superioris innervated by?
Oculomotor CNIII
What is the purpose of the round window of the ear?
Allows fluid in the cochlea to move
What are the 3 scala of the middle ear?
Scala media
Scala tympani
Scala vestibuli
What are the differences between inner and outer hair cells?
Inner = one row, afferent fibres, transmit auditory stimuli Outer = more numerous, 2/3 rows, efferent fibres, modulate inner hair cells
What are the 7 main parts of the basal ganglia?
Putamen Subthalamic nucleus Substantia nigra Hypothalamus Globus pallidus (madia & lateral) Thalamus Caudate nucleus
What does the striatum do?
Caudate & putamen
Main target input of basal ganglia
Releases GABA
Inhibitory (rostral)
What is the lentiform nucleus made up of?
Globus pallidus & putamen
What does the globus pallid us do?
Output source to thalamus
What does the subthalamic nucleus do?
Communicates with globus pallidus
Caudal
What does the substantia nigra do?
In tegmenjtum
Releases dopamine
Caudal (excitatory)
What are the 7 main parts of the limbic system?
Cingulate gyrus Thalamus Fornix Hypothalamus Mamillary body Hippocampus Amgdala
What is the Papez circuit?
Neural circuit for the control of emotional expression
What are the components of the Papez circuit?
Hippocampal formation → fornix → mammillary bodies → anterior thalamic nucleus → cingulum → hippocampal formation
What is the fornix?
Pathway of nerve fibres that transmit information from hippocampus to mamillary body
What is the role of the hippocampus?
Involved in learning, memory & recollection of spatial relationships
What is the role of the parahippocampal gyrus?
Helps modify expression of emotions
What is the role of the amygdala?
Influences behaviour & fear
What is the mamillary body?
Tiny nucleus acting a a relay station of information from the fornix to the thalamus
What are the 4 cerebellar nuclei?
Dentate
Emboliform
Globose
Fastigi
What is the role of the cerebellum?
Coordinates voluntary movement
Balance
Equilibrium
Muscle tone
What connects the cerebellum to the midbrain?
Peduncles
What are the 3 lobes of the cerebellum?
Anterior
Posterior
Floculonodular
What are the fissures of the cerebellum?
Primary - between anterior & posterior
Horizontal - makes lateral & posterior margins of hemisphere
Posterolateral - between floculonodular & posterior
What joins the hemispheres of the cerebellum at the midline?
Vermis
What are the functional divisions of the cerebellum?
Cerebrocerebellum (neocerebellum
Spinocerebellum (paleocerebellum)
Vestibulocerebellum (archicerebellum)
What does the cerebrocerebellum do, is made up of & inputs from?
Planning movements, motor learning, trajectory
Lateral hemispheres
Input from pons via peduncle
What does the spinocerebellum do, is made up of & inputs from?
Regulating body movement, muscle tone, posture
Vermis
Spinocerebellar tracts via peduncles
What does the vestibulocerebellum do, is made up of & inputs from?
Controlling balance & ocular reflexes
Flocculonodular lobe & fastigi nuclei
Input from vestibular nuclei via peduncles
What are the 3 arteries that supply the cerebellum?
Superior cerebellar
Anterior inferior cerebellar
Posterior inferior cerebellar
What are the 3 peduncles?
Superior - midbrain
Middle - pons
Inferior - medulla
What are the 3 layers of the cerebellar cortex from superficial to deep?
Molecular
Purkinje
Granule
What are the 2 inputs to the cerebellar cortex?
Mossy fibres - from middle peduncle, inform of voluntary motor input, synapse with granule cells, have parallel fibres
Climbing fibres - from inferior peduncle, convey muscle proprioception & vestibular inputs
What is the output from the cerebellar cortex?
Purkinje cell axons - from dentate nucleus > superior peduncle > thalamus
What are the symptoms for cerebellar damage?
'DANISH' Dysmetria (inability to judge distance) Ataxia (staggering) Nystagmus (abnormal eye movements) Intention tremor Slurred speech Hypotonia (weak muscles)
What are the 3 primary brain vesicles?
Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)
What are the 5 secondary brain vesicles?
Pros -> telencephalon & diencephalon
Mes -> mesencephalon
Rhomb -> metencephalon & myelencephalon
What do each of the primary brain vesicles from?
Pros - cerebrum; thalamus
Mes - midbrain
Rhomb - cerebellum & pons; medulla
