Wk 2 - Functional Neuroanatomy

Question 1

Neurons differ from other cells in that they are… (x1)

And they serve which three functions?

Answer 1

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

Question 2

Motor neurons are… (x2)

Plus description, location, function

Answer 2

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)

Question 3

Sensory neurons are… (x2)

Plus description, location, function

Answer 3

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

Question 4

Interneurons are… (x2)

Plus description, location, function

Answer 4

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

Question 5

Nine structural features of a typical neuron…

Answer 5

Cell body/soma
Cell membrane
Dendrites
Axon hillock
Axon
Meyelin
Nodes of Ranvier
Buttons
Synapse

Question 6

Function of neuron’s cell body/soma (x1)

Answer 6

Metabolic centre of neuron

Question 7

Neuron’s cell membrane is… (X1)

Answer 7

Semipermeable membran enclosing neuron

Question 8

Dendrites are… (x1)

That…. (x1)

Answer 8

Short processes out of cell body,

Receive most of synaptic contacts

Question 9

The axon hillock is… (X2)

Answer 9

Cone region between cell body and axon,

Previously thought to be originator of signals but now found to happen in initial segment of axon

Question 10

The axon is… (x1)

Answer 10

Long narrow process from cell body

Question 11

Myelin is… (x1)

Answer 11

Fatty insulation around many axons

Question 12

Nodes of Ranvier are… (x1)

Answer 12

Gaps between sections of myelin, where signal is refreshed as it travels

Question 13

Buttons are… (x2)

Answer 13

Ends of axon branches

That release chemicals into synapses

Question 14

Synapses are… (x2)

Answer 14

Gaps between neurons

The chemical transfer space

Question 15

Six structures (+functions) inside the soma

Answer 15

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

Question 16

Two structures (+ functions) inside the synaptic buttons (tubules terminate here)

Answer 16

Synaptic vesicles – smaller packages of neurotransmitter packaged up by golgi apparatus in button
Neurotransmitters – molecules released from active neurons, influencing activity of other cells

Question 17

Neuron cell membrane consists of… (x1)

Which contains… (x2 + functions)

Answer 17

Lipid bilayer
Channel proteins – like fast-acting gates, certain molecules get through when open; and
Signal proteins – allows slower transmission of signal across membrane

Question 18

Four key ions involved in resting membrane potential are?

Answer 18

Na+, K+, Cl-, protein-

Question 19

The resting membrane potential of a neuron is…. (x1 + reasons)

Answer 19

-70mV charge
Less charge inside cell than out, due to relative concentration of ions;
Some permeate membrane more easily than others

Question 20

Four passive, plus one active factors affecting resting potential

Answer 20

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

Question 21

The ionic basis of the resting membrane potential is… (x5)

Answer 21

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

Question 22

Two effects of changes in the post-synaptic potential

Which are result of… (x1)

Answer 22

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

Question 23

Saltatory conduction is… (x1)
And occurs through… (x2)
Resulting in… (x1)

Answer 23

‘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

Question 24

The three phases of an action potential are…

Answer 24

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

Question 25

The absolute refractory period occurs... (x1) | During which time... (x2)

Answer 25

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

Question 26

The relative refractory period occurs... (x1) | During which time... (x2)

Answer 26

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

Question 27

Schwann cells are... (x2)

Answer 27

Glial cells of the PNS | Similar to function of oligodendrocytes (myelin production) in CNS – can guide axonal regeneration

Question 28

Two types of glial cells in the CNS are... (+ functions)

Answer 28

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)

Question 29

Three parts of the synapse that enable neuronal communication are... (+ functions)

Answer 29

Presynaptic terminal – vesicles containing neurotransmitters, receptors for reuptake Junction/gap – NTs ‘float’ briefly after release Post-synaptic terminal – receptors for NTs

Question 30

Exocytosis is... (x1) | Plus differences in small/large vesicles? (x1)

Answer 30

``` 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 ```

Question 31

Directed synapses are when... (x1) | Eg (x1)

Answer 31

Neurotransmitter release and receptor sites are in close proximity Axoaxonic synapses

Question 32

Non-directed synapses are when they are... (x1) Which allow the release of... (x1) Eg (x1)

Answer 32

Not connected to other neurons, just release into space Larger, slower acting neurotransmitters - dopamine, epinephrine, seratonin String of beads synapses

Question 33

Three possibilities for released neurotransmitters | Consideration of which is important because... (x1)

Answer 33

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

Question 34

Two most common types of synapse, | Plus three others (+ descriptions or function)

Answer 34

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)

Question 35

Two general types of neurotransmitters (+ description and egs)

Answer 35

Neurotransmitters – small molecules, small vesicles bundled in synapse, Eg glutamate, GABA, acetylcholine, norepinephrine Neuropeptides – large molecules, large vesicles bundled in soma, Eg Substance P,

Question 36

Relationship of myelin and MS (x1) | Plus symptoms/impacts (x6)

Answer 36

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

Question 37

Myesthenia gravis is... (x2) Plus symptoms/impacts (x5) And treatment (x1)

Answer 37

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

Question 38

Two types of neurotransmitter/ligand receptors, (+functions)

Answer 38

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

Question 39

Two mechanisms for neurotransmitter deactivation in synapses

Answer 39

Reuptake | Enzymatic degradation

Question 40

Autoreceptors on the presynaptic membrane serve to.. (x2)

Answer 40

Regulate neurotransmitter release - | Detecting too much during reuptake = telling cells to produce less, and vice versa

Question 41

Four classes of small molecule/fast-acting neurotransmitters (+ egs)

Answer 41

Amino acids Monoamines Acetylcholine Unconventional NTs

Question 42

Single class of large molecule/slow-acting neurotransmitters, (x 5 subclasses, )plus egs

Answer 42

``` Neuropeptides Pituitary peptides – release hormones, which are slow acting neuropeptides/NTs Hypothalamic peptides Brain-gut peptides Opioid peptides Misc. peptides Eg Substance P, endorphins ```

Question 43

Chain of dopamine and nerepinephrine productions (x6)

Answer 43

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)

Question 44

Chain of seratonin production (x3)

Answer 44

Amino acid tryptophan becomes Serotonin (both indolamines)

Question 45

Seven steps of neurotransmitter action

Answer 45

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

Question 46

Neurotransmitter agonists... (x1) | Plus two egs

Answer 46

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

Question 47

Neurotransmitter antagonists... (x1) | Plus 2 egs

Answer 47

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

Question 48

Six agonistic drug actions on neurotransmitters

Answer 48

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

Question 49

Five antagonistic drug actions on neurotransmitters

Answer 49

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

Question 50

The Pulfrich Illusion occurs when... (x1) | Producing...(x1)

Answer 50

Swinging pendulum is viewed with a filter placed over one eye Illusory rotation in depth (circle rather than side to side)

Question 51

Three components of the Pulfrich illusion

Answer 51

Filter/lens Simple harmonic motion of pendulum Stereoscopic vision

Question 52

Effect of dimming filter/lens in Pulfich illusion... (x2)

Answer 52

Dims the image falling on retina of covered eye | Equals slowing of signal from retina to binocular regions of brain (faster for brighter images)

Question 53

Effect of simple harmonic motion on Pulfrich illusion (x5)

Answer 53

``` 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 ```

Question 54

Effect of stereoscopic vision on Pulfrich illusion (x3)

Answer 54

Two eyes get slightly different image Brain combines these into single percept Important for depth perception

Question 55

Uncrossed disparity is... (x3) Contributing to the (x1) Remember by thinking that... (x1)

Answer 55

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

Question 56

Crossed disparity is... (x3) Contributing to the (x1) Remember by thinking that... (x1)

Answer 56

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

Question 57

Left-to-right pendulum motion, with left eye filtered, leads to the Pulfrich illusion when...(x2)

Answer 57

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)

Question 58

Right-to-left pendulum motion, with left eye filtered, leads to the Pulfrich illusion when...(x2)

Answer 58

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)

Question 59

The combination of left-to-right and right-to-left swings of the pendulum in the Pulfrich illusion lead to the impression of... (x1)

Answer 59

A clockwise elliptical travel path

Question 60

If you filtered the right eye in a Pulfrich illusion... (x3)

Answer 60

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

Question 61

Seven monocular depth cues

Answer 61

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

Question 62

Four egs of amino acid NTs

Answer 62

Glutamate, aspartate, glycine, GABA

Question 63

Two classes of monoamine NTs

Answer 63

Catecholamines and indolamines

Question 64

Three egs of catecholamines (monoamines)

Answer 64

Dopamine, epinephrine, norepinephrine

Question 65

An eg of an indolamine (monoamine)

Answer 65

Seratonin

Question 66

Two classes ofUnconventional NTs

Answer 66

Soluble gasses and endocannabinoids

Question 67

Two egs of soluble gasses (unconventional NTs)

Answer 67

Nitric oxide, carbon monoxide

Question 68

An eg of an endocannabinoid (unconventional NT)

Answer 68

Anandamine