Module 4: Neurology Flashcards
(172 cards)
1
Q
Three types of neurons?
A
Sensory Interneurons Efferent
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Q
Two types of sensory neurons?
A
Psuedounipolar and bipolar
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Q
What are psuedounipolar neurons?
A
Psuedounipolar neurons have a single process called the axon. During development, the dendrites fuse with the axon.
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Q
What are bipolar neurons?
A
Bipolar neurons have two relatively equal fibres extending off the central body.
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Q
Two types of interneurons?
A
Anaxonic and multipolar
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Q
What are anaxonic interneurons?
A
Anaxonic CNS interneurons have no apparent axon
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Q
What are multipolar interneurons?
A
Multipolar CNS interneurons are highly branches but lack long extensions
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Q
What are efferent neurons?
A
A typical multipolar efferent neuron has five to seven dendrites, each branching four to six times. A single long axon may branch several times and end at the enlarged axon terminal
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Q
What cells support neurons? What ratio do they uphold?
A
Glial cells support neurons. The ratio of glial cells to neurons is 50:1
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Q
If an axon is damaged, what occurs?
A
Under some circumstances, the proximal axon may regrow through the existing sheath of Schwann cells and reform a synapse with the proper target
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Q
What is a resting membrane potential determined primarily by?
A
K+ concentration gradient, and the cell’s resting permeability to K+, Na+ and Cl-
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Q
What channels control ion permeability?
A
Gated channels
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Q
Three types of gated channels?
A
Mechanically gated Chemically gated Voltage-gated
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Q
Two types of graded potentials?
A
Sub-threshold and supra-threshold graded potentials
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Q
What is a sub-threshold graded potential?
A
A graded potential starts above threshold (T) at its initiation point but decreases in strength as it travels through the cell body. At the trigger zone, it is below the threshold and therefore does not initiate an action potential
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Q
What is a supra-threshold graded potential?
A
A stronger stimulus at the same point on the cell body creates a graded potential that is still above threshold by the time it reaches the trigger zone, so an action potential results
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Q
What is conduction in action potentials?
A
Conduction is the high-speed movement of an action potential along an axon
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Q
What are the nodes of the axon called in nerves?
A
Nodes of Ranvier
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Q
Can signals in gap junctions be bi-directional?
A
Yes
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Q
What are the excitatory and inhibitory amino acids of the brain?
A
Excitatory: Aspartate Inhibitory: GABA
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Q
What is the excitatory amino acid of the CNS?
A
Glutamate
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Q
How does aspartate excite a brain cell?
A
By depolarising target cells
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Q
How does aspartate inhibit a brain cell?
A
By hyper-polarising target cells by opening Cl- gates
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Q
What enzyme breaks down neurotransmitters?
A
Acetylcholinesterase
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What determines how much of a neurotransmitter is released?
Frequency of action potentials
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What is a divergent pathway?
One pre-synaptic neuron branches to affect a larger number of post-synaptic neurons
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What is a convergent pathway?
Many pre-synaptic neurons provide input to influence a smaller number of post-synaptic neurons
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(Advanced Question) How many capillaries are in the brain?
400 miles worth
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(Advanced Question) What promotes a tight junction in the blood brain barrier?
The astrocyte foot secretes paracrines that promote tight junction formation, and tight junctions prevent solute movement between endothelial cells.
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What is responsible for joining the two halves of the brain? What function does this utilise?
The corpus callosum allows for cerebral laterilisation
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Three structural types of sensory receptors?
Simple Complex Special
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What are simple receptors?
Simple receptors are neurons with free nerve endings. They may have myelinated or unmyelinated axons
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What are complex neural receptors?
Complex neural receptors have nerve endings enclosed in connective tissue capsules
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What are special neural receptors?
Most special senses receptors are cells that release neurotransmitter onto sensory neurons, initiating an action potential
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What are the four main types of sensory receptors?
Chemoreceptors Mechanoreceptors Photoreceptors Thermoreceptors
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What type of receptors are baroreceptors?
Mechanoreceptors
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What type of receptors are osmoreceptors? What do they detect?
Mechanoreceptors - detect cell stretch length
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What determines the amount of space on the somatosensory cortex?
The amount of space on the somatosensory cortex devoted to each body part is proportional to the sensitivity of that part
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(Advanced Question) What gland secretes tears?
The lacrimal gland
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(Advanced Question) What duct connects the eyes to the nasal cavity?
The nasolacrimal duct
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What is the pupil?
An opening that widens and shrinks when pupillary muscles contract
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What is the iris?
The coloured ring of pigment around the eye
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What are the two chambers in the eye?
One is in front of the lens and is filled with an aqueous humor covered by the cornea The second is behind the lens and is a larger, vitreous chamber filled with a vitreous body
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What is vitreous?
Glass-like
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What is the retina?
The retina layer lines the back of the eye and contains photoreceptors
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What is the blind spot in the eye called? Where is it?
The optic disk (blind spot) is the location where neurons join into the optic nerve
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Where do optic nerves cross over?
In the optic chiasm
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Where does the optic tract end?
At the visual cortex in the occipital lobe
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How does the eye produce vision?
Light enters the eye, focused on the retina by the lens Photoreceptors transduce light energy into electrical signals Neural pathways process electrical signals into visual images
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What does the size of the pupil modulate?
The amount of light that reaches the photoreceptors
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What is the pupil's reflex called? What type of reflex is it?
The pupillary reflex is a consensual reflex
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What is the pupillary reflex?
Light in one eye causes constriction in the other eye
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What are the differences between parasympathetic and sympathetic fibres in the eye?
Constriction occurs in response to parasympathetic fibres in bright light Dilation occurs in response to sympathetic nervous system in dim light
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Where does light entering the eye refract?
At the cornea and lens
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What influences refraction?
The angle at which light meets the lens
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Two types of lens? What type of lens is the eye lens?
Concave lens Convex lens (eye)
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What does a concave lens do?
Scatters light rays
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What does a convex lens do?
Causes light rays to converge
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What is the focal length of the lens?
The focal length of the lens is the distance from the centre of the lens to the focal point
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What is a photon?
A discrete packet of energy
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What is light?
A photon with a certain portion of electromagnetic spectrum
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What is accommodation?
A process by which the eye adjusts lens shape to keep objects in focus
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Where is the near point of accommodation?
The closest distance at which the lens can focus on an object
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How does the lens keep an object in focus as it moves closer?
It becomes more rounded
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Why can a close object be blurry?
The light rays are no longer parallel. The lens and its focal length have not changed, and thus the light beam is not focused on the retina
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What is the difference between myopia and hyperopia?
Myopia is when the focal point falls in front of the retina Hyperopia is when the focal point falls behind the retina
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What is a loss of accommodation called in vision?
Presbyopia
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What is astigmatism?
A distorted image usually caused by a cornea that is not a perfectly shaped dome
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What is phototransduction?
Converts light energy into electrical signals. Has photoreceptors
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Where does most acute vision occur?
At the macula and fovea
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What is the macula?
Increased density of nerves in the eye
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What is fovea?
Part of the eye with the clearest vision as neurons are pushed aside
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Where is the blind spot? Why is it blind?
The optic disk is the blind spot as it has no photoreceptors
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What are the two types of photo receptors?
Rods and cones
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What are photoreceptors formed from?
They are modified ganglion cells that contain melanopsin to respond to changing light cues
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What do cones detect in the eye?
Red blue and green light
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What pigments do rods contain?
Rhodopsin
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(Advanced Question) Percentage of men and women who are colour-blind? What is the most common colours to be colour-blind with?
1 in 12 men are colour-blind and 1 in 200 women are colour-blind. Most common is green and red
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What type of neurons do photoreceptor cells converge in?
Bipolar neurons
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How do photoreceptors cell signal process?
Multiple bipolar neurons converge into one ganglion cell and amacrine cells modulate information between bipolar and ganglion cells.
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What is binocular vision?
The central portion of the visual field is in the binocular zone - processed to give 3d vision
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What is the opposite of the binocular zone?
The monocular zone - the portion of the visual field association only with one eye
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What are black and white images that are degraded and difficult to interpret?
Mooney images
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What are sound-waves?
Sound waves are alternative peaks of compressed air and valleys where the air is less compressed
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How are sound waves distinguished?
By their frequency, measured in hertz (Hz)
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How is amplitude measured?
In decibels (dB)
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What separate the middle and inner ear?
The oval and round window
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What directs sound waves into the ear?
The pinna
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What is the membrane that encapsulates the malleous of the ear?
The tympanic membrane
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What tool is used to view the tympanic membrane?
An otoscope
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What is the term for light on surface of the tympanic membrane called?
A cone of light
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First step to transmissions through the ear?
Sound waves strike the tympanic membrane and become vibrations
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What happens when the middle ear bones' vibrate?
The stapes is attached to the membrane of the oval window. Vibrations of the oval window create fluid waves within the cochlea.
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What happens when the vibrations of the oval window create fluid waves within the cochlea?
The fluid waves push on the flexible membranes of the cochlear duct. Hair cells bend and ion channels open, creating an electrical signal that alters neurotransmitter release.
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What happens once neurotransmitters are released within the tympanic duct?
Neurotransmitter release onto sensory neurons create action potentials that travel through the cochlear nerve to the brain.
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What happens once action potentials travel through the cochlear nerve to the brain?
Energy from the waves transfers across the cochlear duct into the tympanic duct and is dissipated back into the middle ear at the round window.
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Where is the perilymph?
In the vestibular and tympanic duct
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Where is the endolymph? What is it secreted by? What is it similar to?
Endolymph is in the cochlear duct. It is secreted by epithelial cells and is similar to intracellular fluid.
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Where is the organ of Corti?
In the cochlear duct
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What is the organ of Corti?
Hair cell receptors and support cells that sit on a basilar membrane and are partially covered by tectorial membranes, which bend stereocililia on non-neural hair cells
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How does both sides of the brain hear sound?
At the medulla the nerves cross, so each part of the brain can processed both ears
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Three types of hearing loss?
Conductive Central Sensorineural
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What is conductive hearing loss?
No transmission through either external or middle ear
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What is central hearing loss?
Damage to neural pathway between ear and cerebral cortex or damage to cortex itself
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What is sensorineural hearing loss?
Damage to structures of inner ear
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How does a cochlea implant work?
It channels sound to bypass the damaged parts of the cochlea and directly stimulate the auditory nerve
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Two parts of the vestibular apparatus?
The semicircular canals and the maculae
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What are the semicircular canals?
Detect rotational acceleration; are filled with endolymph and have christae at the end that detect acceleration
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What are maculae?
Contains otolith crystals that move in response to gravitational force. Detect linear acceleration and the head position
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Where does the equilibrium project to?
The cerebellum
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What does movement of endolymph push?
The gelatinous capula and activates the hair cells
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Where do the oldfaction pathways first lead to?
The thalamus
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With the exception of olfaction, all sensory pathways first travel to the \_\_\_\_, which acts as a relay and processing station
Thalamus
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What is the difference between a preprohormone and a prohormone?
A preprohormone is the precursor protein to one or more prohormones, which are in turn precursors to peptide hormones
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What are the four main touch receptors of the skin?
Meissner's corpuscle Merkel cells Pacinian corpuscle Ruffini endings
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What do Meissner's corpuscles do?
They response to low-frequency vibrations and fine touch
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What do Merkel cells do?
They response to light touch
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Out of the four main touch receptors of the skin, which are found towards the basal lamina and what are superficial?
Superficial: Meissner's corpuscle Merkel cells Ruffini endings Pacinian corpuscles are deeper
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What does the Pacinian corpuscle do?
Have a vibrational-detecting role
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What do Ruffini endings do?
Ruffini endings are slow adapting, encapsulated receptors that respond to skin stretch and are present in both the glabrous and hairy skin
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How many axons can oliogendrocytes and schwan cells wrap around?
Oliogendrocytes can wrap around up to 50 axons, while schwan cells are limited to only one axon
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Difference between a neurotransmitter and neuromodulator?
Generally speaking, a neurotransmitter is a chemical used for neuron to neuron communication, whereas a neuromodulator is a chemical that affects the neurotransmission of a whole group of neurons
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What do merkel receptors sense?
They sense steady pressure and texture
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What do meissner’s corpuscles respond to?
Flutter and stroking movements
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What does the posterior semicircular canal do?
Tilting the head to left or right shoulder on frontal plane
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What does the superior semicircular canal do?
Senses the nodding of head, as in saying yes
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What does the horizontal semicircular canal do?
Sense the rotation of your head, as if you’re saying no
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What are the hair cell/receptors between the vestibular and cochlea duct called?
Organ or Corti
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