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3.2 Neurology > Physiology (Peters) > Flashcards

Physiology (Peters) Flashcards

1
Q

What is the role of a dendrite?

A

Receive inputs from other neurones

Convey graded electrical signals passively to the soma

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2
Q

What is the role of the cell body (soma)?

A

Intergrate incoming electrical signals that are conducted passively to axon hillock

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3
Q

What is the role of the axon hillock and initial segment?

A

The site of initiation of the “all or none” action potential

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4
Q

What is the role of the axon?

A

To conduct output signals as action potentials to presynaptic terminal.

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5
Q

If the axon mediates transport of materials between the soma and presynaptic terminal what is this called?

A

Anterograde

Opposite direction is retrograde

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6
Q

What occurs at the synapse?

A

Point of chemical communication between neurones

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7
Q

What is the clinical importance of retrograde transport of material?

A

Several viruses (herpes, polio, rabies) can exploit this transport to infect neurones

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8
Q

Where are unipolar neurones (one neurite) usually found?

A

Peripheral autonomic system

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9
Q

Where are pseudounipolar (one neurone that bifurcates) neurones usually found?

A

Dorsal root ganglion

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10
Q

Where are bipolar (two neurites) neurones usually found?

A

Retina

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11
Q

Where are multipolar neurones (three or more neurites) usually found?

A

Lower motor neurones

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12
Q

What are the four functional regions of the neuron?

A

Input
Intergrative
Conductile
Output

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13
Q

What type of neurone transmits information from skin to dorsal horn of spinal cord?

A

Sensory neuron

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14
Q

What type of neurone transmits information from ventral horn to spinal cord to skeletal muscle?

A

Motor neurone

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15
Q

What type of neurone transmits information between neurones in CNS

A

Local interneurone

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16
Q

What type of neurone transmits information from dorsal of spinal cord to brain structures?

A

Projection neurones

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17
Q

Describe the action potential

A 
Stimulus arrives
Membrane passively depolarised up to a point where Na channels open
Threshold is reached
Na enters cells
Upstroke of membrane potential so fast
Cascade of opening of Na channels
Positive feedback 
Reaches +40 at the same time voltage K are open but slight delay
Allows membrane potential to decrease
Afferent hyper-polarisation
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18
Q

What happens to the strength of the passive signal as it travels from it’s site of origin along the axon?

A

Strength of signal diminishes

Passive signals do not spread far due to loss across the membrane

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19
Q

Opening of which ion channel causes depolarisation of the membrane?

A

Na channel

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20
Q

What two factors will determine how long the distance that the current will spread?

A

Membrane resistance

Axial resistance of axoplasm

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21
Q

How can passive current spread be increased?

A

Increasing axon diameter

Add insulating material

22
Q

Which cell provides myelin in the PNS?

A

Schwann cells

23
Q

Which cell provides myelin in the CNS?

A

Oligodendrocytes

24
Q

Many Schwann cells surround a single axon and only one oligodendrocyte surround many axons. True/False?

A

True

25
Q

Conduction in myelinated axons is much slower/faster than in non-myelinared axons of the same diameter?

A

Faster!

26
Q

What is the name of the site that action potentials ‘jump’ to and from?

A

Node of Ranvier

27
Q

Name two demyelinating disorders

A 
Multiple sclerosis (CNS)
Guillian-Barré (PNS)
28
Q

What are the 3 morphological classes of synapses?

A

Axodendritic (Most common)
Axosomatic
Axoaxonic (Least common)

29
Q

What is commonly the transmitter for excitatory synapses in the CNS?

A

Glutamate

30
Q

What are the three major amino acid neurotransmitters in the CNS?

A

Glutamate, GABA and glycine

31
Q

What is commonly the transmitter for inhibitory synapses in the CNS?

A

GABA

32
Q

What are the sensations covered by the somatosensory system?

A 
Fine discriminatory touch 
Proprioception
Thermosensation
Nociception (Pain)
Pruriception (Itch)
33
Q

What are 3 divisions of the somatosensory system?

A

Exteroceptive- cutaneous senses
Proprioceptive- posture and movement from sensors in muscle, tendons and joints
Enteroceptive- internal state of body (autonomic function closely linked)

34
Q

What are the 3 neurones that comprise the somatosensory pathway?

A

1st order neurone in PNS (primary sensory afferent)
2nd order neurone in CNS (projection neurone)
3rd order neurone in CNS (projection neurone)
Somatosensory cortex

35
Q

How does a stimulus (mechanical, thermal or chemical) elicit a depolarising receptor potential?

A

Stimulus opens cation selective ion channels in peripheral terminal or primary sensory afferent

36
Q

What is modality?

A

Primary afferent neurones are especially ‘tuned’ to respond to a specific type of energy (stimulus) that normally excited them

37
Q

What is meant by threshold?

A

Relates to the intensity of a stimulus required to excite a sensory unit

38
Q

What do low threshold mechanoreceptors sense?

A

Fine discriminatory touch

39
Q

What do low threshold thermoreceptors sense?

A

Cold, cool, indifferent warm and hot

40
Q

What do high threshold units (nociceptors) sense?

A

High, noxious (potentially damaging), not low intensity stimuli

41
Q

What do high threshold mechanoreceptors (mechanical nociceptors) sense?

A

High intensity mechanical stimuli

42
Q

What do thermal nociceptors sense?

A

Extreme degrees of heat (>45C) or cold (<10-15C)

43
Q

What do chemical nociceptors sense?

A

Substances in tissue (inflammation, prostaglandins, bradykinin, serotonin, histamine etc)

44
Q

What is adaptation?

A

Changing of firing rate in response to a stimulus of changing intensity

45
Q

What are factors that differ between primary sensory afferent fibres?

A

Axon diameter
Extent of myelination
Conduction velocity
Associated sensory receptor

46
Q

Name the groups of primary sensory afferent fibres from thickest to thinnest

A

Group 1–>Group IV

Aα, Aβ, Aδ, C

47
Q

What is the sensory receptor for Aα fibres?

A

Proprioceptors of skeletal muscle

48
Q

What is the sensory receptor for Aβ fibres?

A

Mechanoreceptors of skin

49
Q

What are the sensory receptors for Aδ fibres?

A

Pain and temperature

50
Q

What are the sensory receptors for C fibres?

A

Temperature, pain, itch

3.2 Neurology (9 decks)

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