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Neurobiology > Theme 2 > Flashcards

Theme 2 Flashcards

Properties of Nerve cells

1
Q

Name the different cellular compartments in a neurone

A

Dendrites: Receive and process information and bring it to the soma.

Axon: Conducts signals to other neurones via synapses at the axon terminal.

Soma: Cell body

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2
Q

Define the following terms: 1. Ganglion 2. Nerve 3. Nerve tract/pathway

A
  1. Ganglion: group of neurone cell bodies in the peripheral nervous system (PNS).
  2. Nerve: bundle of axons in the PNS.
  3. Nerve tract or pathway: bundle of axons in the CNS.
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3
Q

What is a multipolar neurone? - examples?

A

Neurones that have multiple dendrites emanating from it’s cell body allowing it to receive impulses from multiple neurones Motorneurones & interneurones

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4
Q

What is the function of an interneurone?

A

Communicates between afferent and efferent neurones in the CNS

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5
Q

How is a bipolar sensory neurone different to most neurones?

A

Has two axons, with a cell body in the middle. One axon attaches to the sensory organ, the other communicates with the CNS.

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6
Q

How does myelination of nerve cells differ in the PNS and CNS?

A

CNS: Oligodendrocytes –> provide myelin to several axons PNS: Schwann cells –> provide myelin only to one axon

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7
Q

What proportion of nerve cells are stained by the ‘Golgi Silver Impregnation method’?

A

1%

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8
Q

What are glial cells?

A

nerve cells that do not carry nerve impulses

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9
Q

Where does an axon emerge from a cell body?

A

Axon Hillock

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10
Q

When observed under a microscope, how can you tell the difference between an axon and a dendrite?

A

Dendrites:

  • Spines covering
  • Taper the further they travel from the cell body

Axon: axon will not taper and features no spines.

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11
Q

Why are spines useful for dendrites?

A

Spines increases the SA on dendrites to send somatic information

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12
Q

Why is the diameter of an axon constant?

A

Conduction velocity of impulses of axons depend on the diameter

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13
Q

What are the different Types of connections between axon terminals and postsynaptic cells?

A
  • AXOSOMATIC
  • AXOAXONIC
  • AXODENDRITIC
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14
Q

What are the three axonal transport mechanisms?

A
  • Fast anterograde
  • Slow anterograde
  • Fast retrograde
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15
Q

Define the terms Anterograde & Retrograde

A

Anterograde: Cell body to terminal

Retrograde: terminal to cell body

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16
Q

What type of axonal transport is likely to be used for the transport of organelles or neurotransmitters towards the synaptic terminal?

A

Fast anterograde

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17
Q

Which protein is involved in this type of transport along the microtubule?

A

Kinesin

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18
Q

What type of axonal transport is likely to be used to transport surplus membrane particles and metabolites to the cell body?

A

Fast anterograde

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19
Q

How does Slow anterograde axonal transport work?

A

Moves soluble substances along the axon at two different rates

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20
Q

How are electrical signals generated?

A

All electrical signals are generated by an influx of ions – a change in potential between the two sides of the membrance

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21
Q

What is the Nernst equation used to calculate?

A

Electrical potential across a membrane, when that membrane is permeable to only one ion. Reflects the electrochemical gradient acting on a given ion

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22
Q

How does the Goldman equation expand on the Nernst equation?

A

takes into account different ion species to work out an overall membrane potential

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23
Q

In terms of relative proportion, which ion leak channels are the most frequent in the membrane of a neurone? Na+, K+, or Cl-

A

K+

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24
Q

What type of signal propagation do nerve cells use? How does this allow conduction?

A

Active propagation

Non-decrements: The signal (action potential) does not change with distance

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25
Q

What are the advantageous properties of electrical responses?

A

Graded bigger stimulus = bigger response

Summation multiple stimuli = summed response (2 stimuli in short sequence, will add up)

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26
Q

What gates do Na ions have?

A

internal (h) (inactivation) and external (m) (activation)

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27
Q

What gates do K ions have?

A

n

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28
Q

What are the two type of synapses?

A

Electrical: no chemical transduction involved (bidirectional) Chemical (unidirectional)

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29
Q

What type of synapse is found in Cardiac cells?

A

Electrical synapses

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30
Q

What is a gap junction? What protein forms the structure of a gap junction?

A

Protein pores that bridge the gap between two cells Connexin

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31
Q

What is the advantage of electrical synapses?

A

NO synaptic delay

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32
Q

What are the two types of neurotransmitter receptors?

A

Ionotrophic: directly linked to an ion channel which opens when neurotransmitter attaches

Metabotrophic: activates a G-protein which then activates an ion channel

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33
Q

Step by step of a neurotransmitter release

A
  1. AP in presynaptic neurone
  2. Ca ions into synaptic bulb
  3. Release of neurotransmitter by exocytosis
  4. Binding of neurotransmitter to postsynaptic
  5. Opening of ion channels on post synaptic
34
Q

Which protein cuts a vesicle from the membrane?

A

Dynamin

35
Q

Which protein coats vesicles involved in the exocytosis of neurotransmitter into the synaptic cleft?

A

Clathrin

36
Q

What is an EPSP?

A

Excitatory Post-Synaptic Potential

37
Q

What are the conduction properties of an AP and an EPSP?

A

AP = Non-decremental

EPSP: decremental

38
Q

What is temporal summation?

A

Adding together of EPSP’s by firing at the same presynaptic terminal at a high frequency to generate an action potential.

39
Q

What is Spatial Summation?

A

Adding together of EPSP’s generated by firing of two or more presynaptic neurones simultaneously to generate an action potential in the post-synaptic neurone

40
Q

What is an IPSP? When may IPSP be required?

A

Inhibitory Post-synaptic Potential Inhibition of motor neurones for antagonistic muscles

41
Q

What are the different order neurones?

A

First order neurone carry signals from the periphery to the spinal cord

Second order neurone carry signals from the spinal cord to the thalamus

Third order neurone carry signals from the thalamus to the primary sensory cortex

42
Q

Define Afferent & Efferent Nerves

A

Afferent: Towards CNS

Efferent: Away from CNS

S - ensory

A - fferent

M - ptor

E - fferent

43
Q

What is the nerve classification of Motor and sensory nerves? Where are their cell bodies found? Are they always Myelinated?

A

Motor = Multipolar - ventral root ganglion –> Myelinated

Sensory = Unipolar - Dorsal root ganglion –> Myelinated, unmyelinated

44
Q

In terms of types of nerve cells, how do the Roman numeral and letter system of classifying nerve fibres differ?

A

Numerals - Sensory neurones

Letters - Sensory and motor neurones

45
Q

As you go down the Numerals table, what fibre property changes?

A

↓Diameter

↓ Conduction

46
Q

Which RN fibre is responsible for:

  1. Slow pain
  2. Fast Pain
A
  1. III
  2. IV
47
Q

What is crude touch?

A

non discriminate nature of touch – something is touching us but do not know where or what is is

48
Q

What is fine touch?

A

can tell what it is

49
Q

In the letter system of classifying nerve cells, which type of fibre has the slowest conduction velocity?

A

C

50
Q

Which type of nerve fibre is responsible for solely the Golgi Tendon Organ?

A

Ib fibre

51
Q

What fibres are part of the Parasympathetic nervous system?

A

C & B

52
Q

What fibres are part of the Sympathetic nervous system?

A

Aa & Ay

53
Q

Define Perception

A

Interpretation of sensation (in cortex)

54
Q

Define somatic

A

Relating to the body

55
Q

Proprioceptors

A

helping to understand where the limbs are in terms of space

56
Q

What’s the 3 main classification types of Sensory receptors?

A
  1. Microscopic Features
  2. Receptor location and activating stimuli
  3. Type of stimulus detected
57
Q

What is a Nociceptor?

A

pain receptors

58
Q

Define Decussation?

A

crossing over

59
Q

What are the Spinal pathways?

A

Pain/temp: Anterolateral

Fine touch/Proprioception: Dorsal column medial lemiscus

60
Q

What are the Trigeminal Pathways?

A

Pain/temp: Trigeminothalamic

Fine touch/Proprioception: Double Trigeminothalamic

61
Q

What is the Dorsal Column-Medial Lemniscus pathway?

Where does it synapse and cross over?

What thalamus nucleus does it synapse in?

A
  1. Enters dorsal root
  2. Ascends dorsal column - ipsilaterally
  3. Synapses in medulla, gracile & cuneate nucleus and crosses over
  4. Ascends to synapse in thalamus: Ventral Posterior Lateral Nucleus
  5. Ascend to sensory cortex (Post Central gyrus)
62
Q

How do fibres from Dorsal Column-Medial Lemniscus travel up the spinal cord the the medula?

A

Travel via 2 fibre bundles (in dorsal columns)

Cuneate fasciculus - upper

Gracile fasciculus - lower

63
Q

What is the Anterolateral system?

Where does it synapse and cross over?

What thalamus nucleus does it synapse in?

A

Enters dorsal column

Synapse & crosses over in spinal cord –> Thalamus

synapses in Ventral posterior lateral nucleus

64
Q

What is the Pain/temp Trigeminothalamic pathway?

A

Enters pons through trigeminal ganglion, synapses & crosses over

Synapses in Thalamus: Ventral posterior medial nucleus

65
Q

What is the Fine touch/Proprioception Trigeminothalamic pathway?

A

Double:

Enters pons through trigeminal ganglion

Decends to Rostral Medulla & other to Medulla

Synapse and cross over

Synapses in Thalamus: Ventral posterior medial nucleus

66
Q

What is a noxious stimuli?

A

anything that can cause harm to the body

67
Q

What are pain receptors?

A

Nociceptors - Free nerve endings

68
Q

Which two types of fibres relay pain sensation, and how does the type of pain differ?

A

A-Delta fibres: Sharp Fast pain —> Myelinated

C-Fibres: Slow, Dull ache —> Non-myelinated

69
Q

What do C-fibres respond to?

A

Mechanical stimulation (same as A-delta)

+ substances from Damaged tissue –> chemicals being released & Cytokines from immune cells

70
Q

Where do C fibres & A-delta fibres synapse?

A

A-Delta: synapse in the top (1 lamina) and further down in the grey matter (5 lamina)

C-fibres: generally in the top layers (1 & 2 lamina)

71
Q

What is Peripheral Sensitisation?

A

Lowering of sensation = threshold lowered = responsiveness increased

72
Q

List some chemicals responsible for increased sensitisation of Nociceptors following damage or inflammation to the body.

A
  • ATP
  • Histamine
  • Serotonin (5-HT)
  • Cytokines
  • Bradykinin
  • Neuropeptides
73
Q

Which cell surface receptors on the postsynaptic membrane are responsible for increased central sensitisation of pain?

A

AMPA and NMDA

74
Q

How does increased stimulation of these receptors increase the central sensitisation of pain?

A
  • Increased activity of pathways
  • Activating receptors
  • Nerve cells increase calcium levels
  • Activate secondary messenger system
  • Triggers transcription factors
  • Up regulate certain proteins
  • Adds more receptors to membranes

more receptors = more responsiveness to released neurotransmitters = strengthening synapse

75
Q

What does the gate theory of pain suggest about the inhibition of pain pathways?

A

Pain pathways can be inhibited by the activation of (touch) A-alpha, and A-beta (Ia, Ib, and II) pathways in the same area. E.g. rubbing an injury makes it feel better.

76
Q

What is Deafferentation?

A

Changes to the pathways, could be a reason for chronic pain

77
Q

What is referred pain?

A

Feeling pain away from area of damage, caused by a convergence of pain pathways to one neuron that travels to the thalamus - have the same neuron, so brain can’t tell where the pain is coming from

78
Q

What is the function of the descending centrifugal pathway?

A

Pain inhibition from central control points in the CNS.

79
Q

List some neurotransmitters that activate the descending centrifugal pathway

A
  • Enkephalin
  • Endorphin
  • Dynorphin
  • Serotonin
  • Glutamate
80
Q

How do opioids reduce pain sensations?

A

Inhibits the pathways that inhibit the centrifugal pathway of pain inhibition (double negative action)

81
Q

What are the main decending pathways?

A

Lateral corticospinal tract:

  • Voluntary control of distal musculature

Anterior corticospinal tract:

  • Voluntary control of proximal musculature

Reticulospinal tracts (pontine and medullary):

  • Regulate flexor reflexes and initiate patterned activity e.g. locomotion

Rubrospinal tract:

  • Motor control
  • excitation of flexor muscles

Vestibulospinal tracts:

  • Lateral - maintaining of balance and posture

Medial - maintaining of head position and fixation of gaze

Tectospinal tract:

  • control head movements in response to visual stimuli

Neurobiology (3 decks)

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