Neuro Flashcards
What is sound?
Displacement of air particles following a sinusoidal pattern of compression and rarefaction.
What is the range of hearing for humans?
20Hz -> 20kHz.
What are the four components of the auditory system?
- The outer ear.
- The middle ear.
- The inner ear.
- Central auditory pathways.
What does the outer ear consist of?
- Pinna.
- Ear canal.
- Tympanic memebrane.
What is the function of the pinna?
- Shaped to gather sound waves and direct them into the ear canal.
- Filters out lower frequency sounds.
- Each pinna is unique.
What is the function of the ear canal?
Directs sound waves towards the tympanic membrane.
What happens when sound hits the tympanic membrane?
It vibrates like the surface of a drum and transmits the sound waves deeper into the ear towards the cochlea.
What does the middle ear consist of?
- The ossicles.
- The Eustachian tube.
- Tensor tympani and stapedius muscles.
Describe the ossicles and how they function.
- Malleus (hammer): rests against tympanic membrane, head of the ‘hammer’ connects to incus.
- Incus (anvil): when struck by ‘hammer’ sound waves are transmitted to the stapes.
- Stapes (stirrups): receives sound waves, transmitting them to oval window.
Discuss the importance of the superior and inferior openings of the auditory tube.
- Superior: middle ear cavity.
- Inferior: nasal cavity.
- Therefore, connection of airflow from external environment and middle ear.
- Vital for maintaining equal air pressure either side of the tympanic membrane, preventing pain and rupture.
What is the main role of the tensor tympani and stapedius muscles?
To dampen sound vibrations and reduce perceived volume.
What does the inner ear consist of?
- The cochlea.
- The vestibular system.
What does the cochlea allow us to perceive?
Sound.
What does the vestibular system consist of?
- Semicircular canaks.
- Utricle.
- Saccule.
What does the vestibular system allow us to perceive? Which structures within it allow these perceptions?
Movement - semicircular canals.
Linear acceleration - utricle and saccule.
What are the 2 openings of the cochlea?
Round window and oval window.
What are the 3 components of the cochlea?
- Scala vestibuli.
- Scala media.
- Scala tympani.
Which ionic fluid is found in the scala media?
Perilymph, high in K+.
Which ionic fluid is found in the scala vestibuli and scala tympani?
Endolymph, rich in Na+.
What affect on hearing can ion channel abnormalities have?
Can cause deafness.
Describe the basilar membrane.
- Narrow and stiff at base.
- Wide and floppy at apex.
What is tonotopy and which membrane has this feature?
- The organisation of sound frequencies along an axis.
- Basilar membrane.
- High frequencies detected at base.
- Low frequencies detected at apex.
Where is the organ of Corti?
In the scala media.
Are the basilar and tectorial membranes mobile or fixed in place?
Basilar - mobile.
Tectorial - fixed.
Discuss the importance and basic roles of the hair cells of the organ of Corti.
Inner hair cells - important, mechanical transduction.
Outer hair cells - helpful, fine tuning.
How do the inner hair cells perform mechanical transfuction?
Basilar membrane moves -> inner hair cells move -> activate attached cochlear nerve fibres -> cochlear nerve -> activated central auditory pathway.
What will occur upon loss of inner hair cells?
Deafness.
How do the outer hair cells fine tune sound?
Stiffen basilar membrane either side of the maximum stimulated inner hair cells, to focus on that sound and dampen others.
What will occur upon loss of outer hair cells?
Loss of sharpness of hearing.
What is interaural time difference?
One ear hearing a sound first, as that ear is closer to the sound.
What is interaural intensity difference?
One ear hearing a sound louder, as that ear is closer to the sound.
What type of hearing loss occurs with a defective outer/middle ear?
Conductive hearing loss.
What type of hearing loss occurs with a defective inner ear?
Sensorineural hearing loss.
What are neurons specialised for?
Electrical signalling.
When are neurons mainly formed?
During development, but small areas of the brain may continue making neurons e..g the hippocampus.
Which are formed first; neurons or glia?
Neurons.
What are the two forms of neuronal synapse?
Chemical and electrical.
How do chemical synapses work? Give an example.
Via neurotransmitters e.g. glutamate.
How do electrical synapses work? Give an example.
Via a direct flow of ions e.g. hypothalamus for hormone secretion.
Define neural plasticity.
Changes in neuronal/synaptic structure and function in response to neural activity. It is the basis of learning and memory.
Give an example of neuronal heterogenity.
Neocortex. 6 layers of varying cells/structures.
What is the key role of oligodendrocytes?
Myelinating cells of the CNS.
Describe the role of myelin.
Insulates axon segments, enabling rapid nerve conduction.
Describe the structure of the myelin sheaths.
Interrupted by nodes of Ranvier, to allow saltatory conduction (faster).
Describe microglia.
Resident immune cells of the CNS. Phagocytic.
Describe the origin of microglia.
Originate from yolk sac progenitors that migrate into the CNS, therefore closer to macrophages in origin.
Describe the varying structure of microglia in different states.
Resting state - highly ramified.
Activated - retract processes, become amoeboid.
Give 3 functions of microglia.
- Immune surveillance.
- Phagocytosis.
- Synaptic plasticity.
Describe astrocytes.
Star-like cells, most numerous glial cells in the CNS, highly heterogenous.
Give 5 functions of astrocytes.
- Define brain micro-architecture.
- Envelope / tripartite synapses, buffer K+ etc.
- Metabolic support.
- Neurovascular coupling.
- Proliferate in disease.
Name 3 specialised astrocytes.
- Radial glia.
- Bergmann glia.
- Müller cells.
What are radial glia important for?
Brain development.
What are Bergmann glia important for?
Structure (cerebellum).
What are Müller cells important for?
Providing a scaffold for other cells to form on (retina).
Define motor neurone disease.
Adult-onset neurodegenerative disease, characterised by loss of upper and lower motor neurones.
Define multiple sclerosis.
Autoimmune demyelinating disease, where immune cells attack the myelin sheath of oligodendrocytes.
Give the 4 features of the blood-brain barrier.
- Endothelial cell tight junctions.
- Basement membrane.
- Astrocyte end feet.
- Pericytes.
Give 4 events that the blood-brain barrier is sensitive to.
- Inflammation.
- Hypertension.
- Trauma.
- Ischaemia.
Where can ependymal cells be found?
Lining ventricles and the central canal of the spinal cord.
What is the function of ependymal cells?
- CSF production, flow and absorption.
- Allowing solute exchange between nervous tissue and CSF.
Describe the structure of ependymal cells.
- Epithelial-like.
- Ciliated to facilitate flow,.
What is the main site of CSF production?
Choroid plexus.
How is the choroid plexus formed?
From modified ependymal cells.
What does the term myoclonus refer to? Give an example of a form of myoclonus.
- A quick jerking movement that you cannot control.
- E.g. the hiccups.
Describe the McGurk Effect.
Occurs when the auditory component of one sound is paired with the visual component of another sound, leading to the perception of a third sound.
What % of your brain is far?
60%.
What % are the neocortex and language centres of your brain?
76%.
What are the primitive reflexes?
The reflex actions arising from the brainstem that are typically present in childhood, but not in healthy or neurological intact adults, in response to particular stimuli.
What is the rooting reflex?
Turn head and mouth in direction of stroking of cheek.
What is the sucking reflex?
Sucking objects that touch the lips.
What is the moro (startle) reflex?
Back arches, legs and arms flung out and then brought back towards chest in hugging motion.