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Neurology > Physiology > Flashcards

Physiology Flashcards

1
Q

What is the function of the axon hillock of a neuron?

A

This is at the point where the cell body of a neurone becomes the axon

Site of initiation of ‘all-or-nothing’ signal

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2
Q

What is the function of the axon of a neuron?

A

Conducts action potentials to other neurones (or other cells)

This can occur between the soma and presynaptic terminal (anterograde direction) and vice versa (retrograde direction)

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3
Q

What is the clinical significance of the retrograde direction of travel along an axon of a neurone (presynaptic terminal to soma)?

A

Several virus (e.g. herpes, polio, rabies) exploit retrograde transport to infect neurones (often with devastating effect)

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4
Q

What is the definition of a unipolar neuron?

A

Has one neurite arising from the soma

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5
Q

What is a pseudounipolar neuron and give an example of this kind?

A

A neuron containing one neurite that bifurcates e.g. dorsal root ganglion or peripheral sensory nerve

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6
Q

What is the definition of a bipolar neuron and give an example of this kind?

A

A neuron with two neurites e.g. a retinal bipolar neurone

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7
Q

What is the definition of a multipolar neuron and give an example of this kind?

A

A neuron with three or more neurites e.g. lower motor neurone

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8
Q

What are the four functional regions of all neurones regardless of type?

A

Input

Intergrative

Conductile

Output

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9
Q

What is the resting membrane potential of neurons?

A

-70mV

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10
Q

What is the threshold membrane potential needed to cause an action potential in a neuron?

A

-60mV

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11
Q

What causes the upstroke in membrane potential during a neuronal action potential?

A

Sodium influx via voltage activated Na+ channels

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12
Q

What causes the downstroke in membrane potential of a neuronal action potential?

A

K+ efflux via voltage-activated K+ channels

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13
Q

Why do passive signals not travel along neurons far from their site of origin?

A

The nerve cell membrane is not a perfect insulator so there is current loss across the membrane

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14
Q

What are glial cells?

A

Supportive cells of the nervous system

e.g. Schwann cells (PNS) and oligodendrocytes (CNS)

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15
Q

What are Schwann cells?

A

The main glial cell of the peripheral nervous system, forming the myelin sheath in myelinated axons

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16
Q

What are oligodendrocytes?

A

The main glial cell of the central nervous system, forming the myelin sheaths

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17
Q

Conduction through which is faster: myelinated or non-myelinated axons?

A

Myelinated

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18
Q

What is saltatory conduction?

A

The propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials

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19
Q

What are the nodes of Ranvier?

A

The only place along a myelinated axon that ions are exchanged across the axon membrane, allowing regeneration of action potentials across two peices of the myelinated axon

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20
Q

Is an excitatory response a depolarising or hyperpolarising one?

A

Depolarising

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21
Q

Is an inhibatory response a depolarising or hyperpolarising one?

A

Hyperpolarising

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22
Q

What is the most frequent transmitter in the excitatory synapse in the CNS?

A

Glutamate

23
Q

What are the most frequent transmitters of the inhibitory synapse of the CNS?

A

G-aminobutyric acid (GABA), or glycine

24
Q

What is the function of the matrix of fibrous extracellular protein within the synaptic cleft?

A

Holds the pre- and post-synaptic membranes together across the cleft

25
Q

Which structures on the presynaptic membrane are amino acids and amines released from?

A

Synaptic vesicles

26
Q

What is the response illicited by a stimulus (e.g. mechanical, thermal or chemical) at a sensory neurone terminal?

A

A depolarising/generator potential which is proportional to the intensity of the stimulus

Hermann currents trigger ‘all-or-nothing’ action potential response

This travels along the axon and releases neurotransmitter in quantities proportional to the intenisty of the signal

27
Q

What is adaption in terms of primary sensory neurones?

A

A feature that determines whether they change their firing rate only in response to a stimulus of changing intensity, or fire continuously throughout a constant stimulus

28
Q

Which primary sensory neurones have the greatest conduction velocity, Group I - Group IV and why?

A

Group 1 - most heavily myelinated

29
Q

What is the receptive field [RF] of a primary senory neurone?

A

The region that when stimulated with an adequate stimulus causes a response in that neurone

e.g the part of the periphery that the neurone supplies

30
Q

What are the two components of a lower motor neurone and their function?

A

Alpha motor neurones innervate the bulk of fibres within a muscle that generate force

Gamma motor neurones innervate the muscle spindle

31
Q

What is a motor neurone pool?

A

The collection of alpha motor neurones that innervates a single muscle

32
Q

What two principle mechanisms determine the force generated by muscle contraction?

A

Frequency of action potential discharge of the motor neurone

The recruitment of synergistic motor units

33
Q

What is significant about the distribution of cell bodies of alpha motor neurones in the ventral horn?

A

LMNs innervating axial muscles medial to those innervating distal muscles

LMNs innervating flexors dorsal to those supplying extensors

34
Q

What is the difference between fast and slow skeletal muscle types?

A

Difference lies in time taken for myosin ATPase to split ATP to provide energy for cross bridge building

This is reflected in time taken to reach peak tension

35
Q

What are the characteristics of Type 1, Slow oxidative skeletal muscle fibres?

A

ATP from oxidative phosphorylation

Fatigue resistant

Slow contraction and relaxation

Dark colour due to high myoglobin concentration

36
Q

What are the characteristics of Type IIa, fast oxidative skeletal muscle fibres?

A

ATP from oxidative phosphorylation

Fast relaxation and contraction

Fatigue resistant

Quite red and reasonably well vascularised

37
Q

What are the characteristics of Type IIx, fast oxidation skeletal muscle fibres?

A

ATP from glycolysis

Fast contraction

Not fatigue-resistant

Pale and poorly vascularised

38
Q

What is a myotactic reflex?

A

Stretch reflex - a muscle contraction in response to stretching within the muscle

39
Q

What are the components of a muscle spindle?

A
  • fibrous capsule
  • intrafusal muscle fibres (note extrafusal fibres generate muscle force)
  • sensory afferents (Ia class, myelinated and very fast conducting) that innervate the intrafusal fibres
  • gamma motor neurone efferents that innervate the intrafusal fibres
40
Q

What are muscle spindles?

A

Sensory receptors within the belly of a muscle that primarily detect changes in the length of this muscle

They convey length information to the central nervous system via sensory neurons

41
Q

What is the process of the monosynaptic arc of the myotactic reflex?

A
  1. Stretch of muscle spindle
  2. Activation of Ia afferent
  3. Excitatory synaptic transmission in spinal cord (monosynaptic)
  4. Activation of alpha motor neurone
  5. Contraction of homonymous muscle
42
Q

How do the intrafusal muscle fibres work during voluntary movement?

A

Work in coordination to contract and relax with extrafusal fibres

43
Q

What are golgi tendon organs?

A

Golgi tendon organs are located at the junction of muscle and tendon and detect changes in muscle tension

44
Q

What is the function of golgi tendon organs?

A

They act in series with extrafusal fibres to protect muscle from overload e.g. weightlifting and maintain optimal muscle tension

45
Q

Which glial cells are found in the CNS?

A

Astrocyte

Oligodendrocyte

Microglial cells

Ependymal cells

46
Q

Which glial cells are found in the PNS?

A

Schwann cells

Satellite cells

47
Q

How do astrocytes contribute to the blood brain barrier?

A

Through vascular foot processes which surround the capillary, creating a physical barrier

48
Q

Where are satellite cells found?

A

Peripheral nervous system surrounding autonomic and sensory neurons

49
Q

Which glial cells create myelin sheath?

A

Schwann cells and oligodendrocytes

50
Q

What is the difference between Schwann cells and oligodendrocytes?

A

Schwann cells - PNS and encapsulate one segment of myelin

Oligodendrocytes - CNS and encapsulates multiple segments of myelin

51
Q

What do microglial cells do?

A

Act similarly to macrophages and provide immune support for the CNS

52
Q

What do ependymal cells do?

A

Filter blood to form CSF

53
Q

Where can ependymal cells be found?

A

Choroid plexus

Neurology (17 decks)

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