Wk 2 - Functional Neuroanatomy Flashcards
Neurons differ from other cells in that they are… (x1)
And they serve which three functions?
Excitable - conducting electrical signals, communicating through chemical signals
Reception – of info from neighbouring neurons
Conduction – integration of info from adjacent neurons
Transmission – of signal to adjacent
Motor neurons are… (x2)
Plus description, location, function
Multipolar efferent neurons, that move toward central organ or point – messages from the brain/spinal cord to muscles/organs
Length of fibres - Short dendrite, long axons
Location - Dendrites and cell body located in spinal cord, axon outside spinal cord
Function - Conducts impulse to an effector (muscle or gland)
Sensory neurons are… (x2)
Plus description, location, function
Unipolar afferent neurons, move away from central organ/point – messages to brain/spinal cord from receptors
Length of fibres - Long dendrites, short axon
Location - Cell body and dendrite outside of spinal cord, cell body is in a dorsal root ganglion
Function - Conduct impulse to spinal cord
Interneurons are… (x2)
Plus description, location, function
Typically pictured with short/no axon, that relays message form sensory neurone to motor neuron
Make up the brain and spinal cord
Length of fibres – short dendrites and short or long axon
Location – entirely within the spinal cord or CNS
Function – interconnect sensory with appropriate motor neuron
Nine structural features of a typical neuron…
Cell body/soma Cell membrane Dendrites Axon hillock Axon Meyelin Nodes of Ranvier Buttons Synapse
Function of neuron’s cell body/soma (x1)
Metabolic centre of neuron
Neuron’s cell membrane is… (X1)
Semipermeable membran enclosing neuron
Dendrites are… (x1)
That…. (x1)
Short processes out of cell body,
Receive most of synaptic contacts
The axon hillock is… (X2)
Cone region between cell body and axon,
Previously thought to be originator of signals but now found to happen in initial segment of axon
The axon is… (x1)
Long narrow process from cell body
Myelin is… (x1)
Fatty insulation around many axons
Nodes of Ranvier are… (x1)
Gaps between sections of myelin, where signal is refreshed as it travels
Buttons are… (x2)
Ends of axon branches
That release chemicals into synapses
Synapses are… (x2)
Gaps between neurons
The chemical transfer space
Six structures (+functions) inside the soma
Endoplasmic reticulum – folded membranes that holds ribosomes that produce proteins (neurotransmitters)
Cytoplasm – clear internal fluid of cell
Golgi complex – membranes that package large protein molecules into vesicles
Tubules – carry material throughout neurons/vesicles of proteins down to synapses over a period of days
Nucleus – spherical DNA-containing structure
Mitochondria – sites of aerobic (oxygen-consuming) energy release
Two structures (+ functions) inside the synaptic buttons (tubules terminate here)
Synaptic vesicles – smaller packages of neurotransmitter packaged up by golgi apparatus in button
Neurotransmitters – molecules released from active neurons, influencing activity of other cells
Neuron cell membrane consists of… (x1)
Which contains… (x2 + functions)
Lipid bilayer
Channel proteins – like fast-acting gates, certain molecules get through when open; and
Signal proteins – allows slower transmission of signal across membrane
Four key ions involved in resting membrane potential are?
Na+, K+, Cl-, protein-
The resting membrane potential of a neuron is…. (x1 + reasons)
-70mV charge
Less charge inside cell than out, due to relative concentration of ions;
Some permeate membrane more easily than others
Four passive, plus one active factors affecting resting potential
Random motion
Differential permeability of membrane
Electrostatic pressure – similar to magnetism, like repels like
Concentration gradients – high dissipates to low
Energy-using process: Sodium-potassium pump
The ionic basis of the resting membrane potential is… (x5)
Cl- ions are in status quo – concentration pressure matches electrostatic
Na+ is pushed in by 12mV of combined electrostatic and concentration gradient
K+ have 20mV so balance is maintained by expelling it
Pump holds resting potential by pumping 2 K in for every 3 Na out
Changes in the resting potential make it more or less likely to fire
Two effects of changes in the post-synaptic potential
Which are result of… (x1)
Becoming less negative is excitatory (EPSP)
Slightly more negative in inhibitive – shuts off action or reduces likelihood of firing (IPSP)
Thousands of signals at same time – are summed either spatially or temporally, and enough excitatory trigger action potential
Saltatory conduction is… (x1)
And occurs through… (x2)
Resulting in… (x1)
‘Skipping’ conduction in myelinated axons, which is refreshed at each stage
Passive conduction occurs, instantly and decrementally, along each myelin segment
New action potential generated at each node of ranvier
Instant conduction along segments = faster than un-myelinated axons
The three phases of an action potential are…
Rising phase: membrane reaches threshold, opens ion channels = massive depolarisation
Repolarisation, then
Hyperpolarisation as potassium channels slower to close, during which you get:
Absolute refractory period, and
Relative refractory period
The absolute refractory period occurs… (x1)
During which time… (x2)
During hyperpolarisation, from 1-3ms
Potential is so negative that no amount of stimulation will cause action potential.
Makes sure info only goes in one direction
The relative refractory period occurs… (x1)
During which time… (x2)
During hyperpolarisation, from 3-4.5 ms)
Potential is still negative, but can fire if given extra stimulation. Important because rate of firing is info for gauging stimulus intensity
Schwann cells are… (x2)
Glial cells of the PNS
Similar to function of oligodendrocytes (myelin production) in CNS – can guide axonal regeneration
Two types of glial cells in the CNS are… (+ functions)
Oligodendrocytes – extensions from cell body are rich in myelin, create sheath, provide structural integrity
Astrocytes (stars) – gave glials the rep for being structural support; clean up debris through phagocytosis (engulfing waste and metabolising it)
Three parts of the synapse that enable neuronal communication are… (+ functions)
Presynaptic terminal – vesicles containing neurotransmitters, receptors for reuptake
Junction/gap – NTs ‘float’ briefly after release
Post-synaptic terminal – receptors for NTs
Exocytosis is… (x1)
Plus differences in small/large vesicles? (x1)
First stage of chemical transmission Small vesicles (produced in button) released quite quickly, larger vesicles form the soma take a few action potentials to fully deploy
Directed synapses are when… (x1)
Eg (x1)
Neurotransmitter release and receptor sites are in close proximity
Axoaxonic synapses
Non-directed synapses are when they are… (x1)
Which allow the release of… (x1)
Eg (x1)
Not connected to other neurons, just release into space
Larger, slower acting neurotransmitters - dopamine, epinephrine, seratonin
String of beads synapses
Three possibilities for released neurotransmitters
Consideration of which is important because… (x1)
Taken up by pre-synaptic receptors
‘Destroyed in the gap, before getting to post-synaptic receptors
Taken up by post-synaptic receptors
Drugs influence one of these three processes
Two most common types of synapse,
Plus three others (+ descriptions or function)
Axodendritic (axon terminal buttons on dendrites)
Axosomatic (axon terminal buttons on soma / cell body)
But also
Dendritic spines (axon terminal buttons on spines of dendrites)
Dendrodendritic – dendrite to dendrite, and often bidirectional transmission
Axoaxonic – (presynaptic facilitation/inhibition of that button on the post-synaptic neurone)
Two general types of neurotransmitters (+ description and egs)
Neurotransmitters – small molecules, small vesicles bundled in synapse, Eg glutamate, GABA, acetylcholine, norepinephrine
Neuropeptides – large molecules, large vesicles bundled in soma, Eg Substance P,
Relationship of myelin and MS (x1)
Plus symptoms/impacts (x6)
Autoimmune disease, result of poor neural transmission - normally saltatory becomes detrimental along axon.
Visual – blurred and double, nystagmus, ‘flashes’
Motor – weakness, slurred speech, muscle wastage, poor posture, tics
Sensory – numbness, tingling, pain
Coordination and balance
Cognitive – short and long term memory, forgetfulness, slowed recall
Death - once spreads to vital organs
Myesthenia gravis is… (x2)
Plus symptoms/impacts (x5)
And treatment (x1)
Autoimmune disease – Immune system destroys Ach receptors
Signal formation and transmission is fine, issues in synapse with muscle
Extreme fatigability
Fluctuating muscle weakness
Problems chewing (dysphagia) and talking (dysarthria)
Respiratory weakness
Anticholinesterase inhibitors - increase/prolong effects of ACh
Two types of neurotransmitter/ligand receptors, (+functions)
Ionotropic – associated with ligand-activated ion channels; very fast
Metabotropic – associated with signal proteins and G proteins; slower; may travel just inside, or may go all the way to influencing DNA
Two mechanisms for neurotransmitter deactivation in synapses
Reuptake
Enzymatic degradation
Autoreceptors on the presynaptic membrane serve to.. (x2)
Regulate neurotransmitter release -
Detecting too much during reuptake = telling cells to produce less, and vice versa
Four classes of small molecule/fast-acting neurotransmitters (+ egs)
Amino acids
Monoamines
Acetylcholine
Unconventional NTs
Single class of large molecule/slow-acting neurotransmitters, (x 5 subclasses, )plus egs
Neuropeptides Pituitary peptides – release hormones, which are slow acting neuropeptides/NTs Hypothalamic peptides Brain-gut peptides Opioid peptides Misc. peptides Eg Substance P, endorphins
Chain of dopamine and nerepinephrine productions (x6)
Tyrosine – an amino acid and precursor that converted to
L-Dopa – which then synthesises
Dopamine, which is converted by enzymes into
(all first three are catecholamines)
Norepinephrine (noradrenalin), converted by enzyme to
Epinephrine (adrenalin)
Chain of seratonin production (x3)
Amino acid tryptophan becomes
Serotonin
(both indolamines)
Seven steps of neurotransmitter action
Synthesised from precursors
Stored in vesicles
Those that leak destroyed by enzymes
Action potential cause vesicle to fuse with membrane, release NT
Binding with autoreceptors inhibits further release
Binding to post-synaptic receptors
Deactivation through reuptake/enzymatic degradation
Neurotransmitter agonists… (x1)
Plus two egs
Increase/facilitate activity of NT
Cocaine – catecholamine agonist; blocks reuptake, preventing activity of NT from being turned off – amplifies effect
Benzodiazepines – GABA agonists; bind to GABA molecule and increases binding of GABA; works as muscle relaxants, anticonvulsants – GABA is inhibitory, so effect becomes prolonged and amplified
Neurotransmitter antagonists… (x1)
Plus 2 egs
Reduce the effects of NT
Atropine – Ach antagonist; binds and blocks muscarinic receptors – many of these metabotropic receptors are in brain; high doses disrupt memory; the active in bella donna
Curare – Ach antagonist; bind and block nicotinic receptors – the ionotropic receptors at neuromuscular junction; causes paralysis
Six agonistic drug actions on neurotransmitters
Increasing synthesis of NTs
Increase NT numbers by destroying degrading enzymes
Increase release from buttons
Bind to/block autoreceptors
Bind to post-synaptic receptors to activate or increase NT effect
Block deactivation through reuptake/degradation
Five antagonistic drug actions on neurotransmitters
Block synthesis of NT molecules
Cause leakage from vesicles (= destruction by enzymes)
Block release from buttons
Activate autorreceptors, inhibit NT release
Block post-synaptic receptors
The Pulfrich Illusion occurs when… (x1)
Producing…(x1)
Swinging pendulum is viewed with a filter placed over one eye
Illusory rotation in depth (circle rather than side to side)
Three components of the Pulfrich illusion
Filter/lens
Simple harmonic motion of pendulum
Stereoscopic vision
Effect of dimming filter/lens in Pulfich illusion… (x2)
Dims the image falling on retina of covered eye
Equals slowing of signal from retina to binocular regions of brain (faster for brighter images)
Effect of simple harmonic motion on Pulfrich illusion (x5)
Stationary pendulum at top of swing, until gravity overcomes inertia Accelerates to bottom of swing Peak acceleration just before bottom Gravity decelerates pendulum on upswing Momentarily stationary at other side
Effect of stereoscopic vision on Pulfrich illusion (x3)
Two eyes get slightly different image
Brain combines these into single percept
Important for depth perception
Uncrossed disparity is… (x3)
Contributing to the (x1)
Remember by thinking that… (x1)
When images of objects located further away than the fixation point APPEAR
Further to the left in space to the left eye, and
Further to the right in space to the right eye
Pulfrich illusion
To change your fixation point, you’d have to ‘uncross’ your eyes
Crossed disparity is… (x3)
Contributing to the (x1)
Remember by thinking that… (x1)
When images of objects located nearer than the fixation point APPEAR
Further to the right in space to the left eye, and
Further to the left in space to the right eye
Pulfrich illusion
To change your fixation point, you’d have to ‘cross’ your eyes
Left-to-right pendulum motion, with left eye filtered, leads to the Pulfrich illusion when…(x2)
Left eye signal is delayed, causing object to look increasingly further away as it accelerates and increases uncrossed disparity toward maximum at bottom of swing
Uncrossed disparity decreases as object decelerates on the upward swing, with images matching again at stationary point (before starting right-to-left swing)
Right-to-left pendulum motion, with left eye filtered, leads to the Pulfrich illusion when…(x2)
Left eye delay causes image to lag behind that of right eye, signalling crossed disparity and object appearing closer as it accelerates to maximum at bottom of swing
Crossed disparity decreases as object decelerates on the upward swing, with images matching again at stationary point (before starting right-to-left swing)
The combination of left-to-right and right-to-left swings of the pendulum in the Pulfrich illusion lead to the impression of… (x1)
A clockwise elliptical travel path
If you filtered the right eye in a Pulfrich illusion… (x3)
Left-to-right motion = crossed disparity = illusory forward arc
Right-to-left motion = uncrossed disparity = illusory backward arc
Combination = illusory motion in an anti-clockwise ellipse
Seven monocular depth cues
Occlusion - objects covering another seem closer
Linear perspective - converging parallel lines signal distance
Retinal size - distant objects project smaller image
Texture gradient - finer on distant objects
Light scatter - distance equals blue/hazy
Motion parallax - moving head gives perspective change
Shape from shading - we assume light from above
Four egs of amino acid NTs
Glutamate, aspartate, glycine, GABA
Two classes of monoamine NTs
Catecholamines and indolamines
Three egs of catecholamines (monoamines)
Dopamine, epinephrine, norepinephrine
An eg of an indolamine (monoamine)
Seratonin
Two classes ofUnconventional NTs
Soluble gasses and endocannabinoids
Two egs of soluble gasses (unconventional NTs)
Nitric oxide, carbon monoxide
An eg of an endocannabinoid (unconventional NT)
Anandamine
