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Clinical Measurements > Biopotential, Motor & Sensory Function > Flashcards

Biopotential, Motor & Sensory Function Flashcards

1
Q

What is the soma?

A

Cell body of a neuron

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2
Q

What are dendrities

A

End of neurone to receive information

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3
Q

How many neurons in the brain?

A

10^11

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4
Q

What is the function of the axons?

A

Transmit electrical signal output

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5
Q

How does information travel from 1 neuron to another?

A

Synapses

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6
Q

How do nerve cells survive?

A

Oxidative metabolism only

Die in anaerobic conditions

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7
Q

Can nerve axons regenerate?

A

In PNS, not CNS

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8
Q

How many synapses in an adult?

A

100-500 trillion

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9
Q

Different parts of a neuron

A 
Cell Body (soma)
Cell Membrane
Nucleus
Dendrites
Terminal Branches
Axon
Myelin Sheath
Node of Ranvier
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10
Q

What are the types of neurons?

A

Sensory (afferent)
Motor (efferent)
Interneurons

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11
Q

What do sensory neurons do?

A

Send info from sensory receptors (in skin/nose/eyes/tongue/ears) TOWARDS the CNS

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12
Q

What do motor neurons do?

A

Send info AWAY from CNS to muscles or glands

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13
Q

What do interneurons do?

A

Send info between sensory and motor neurons. Most interneurons are located in CNS

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14
Q

What is the concentration gradient on ions across the nerve cell? How does it work?

A
  • high concentration of K+ on the inside
  • high conc. of Na+ on outside
  • in resting = K+ diffuse through membrane creating a potential difference which limits perfusion
  • typically -70 to -80mV
  • active pump which pumps K+ in and Na+ out of the cell balances diffusion
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15
Q

What is the role of ion selective gates?

A
  • can be controlled (on or off)

- electrically controlled according to membrane potential or chemically

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16
Q

What is the role of the K+ gate?

A
  • allows K+ ions to diffuse out of the cell creating a potential across the membrane
  • acts like a resistor capacitor circuit for small electrical disturbances
  • makes cell more negative = hyperpolarisation
  • makes cells more positive = depolarisation
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17
Q

How is the action potential created?

A
  • depolarisation beyond the threshold (-45mV) occurs
  • this means sodium ion gates open causing further depol -> peaks to +55mV
  • sodium ion gates close
  • potassium ion gates open = hyperpolarisation
  • switch in potential is called an action potential
18
Q

Positive Feedback Process

A
  • after threshold is reached
  • the stimulus causes the sodium ions to open
  • as more sodium ions on the outside, inside is negative so sodium ions rush into the neuron
  • neuron becomes positive = depolarised
  • takes longer for K+ channels to open
  • when they do, K+ rush out = hyperpolarisation
  • sodium channels close at this point
  • action potential goes back to -70 (repolarisation) but actually goes past -70 (hyperpolarisation) as K+ channels stay open for a bit too long
  • gradually concentrations return to resting levels
19
Q

What is the action potential followed by?

A
  • absolute refractory period

- then a relative refractory period

20
Q

How does the action potential get transferred?

A
  • propagation

- action potential at one site of the membrane causes depolarisation in neighbouring regions

21
Q

Nodes of Ranvier

A
  • breaks in myelin sheath allowing action potential to propagate
  • otherwise speed of propagation is limited by membrane capacitance
22
Q

What is the effect of increasing axon diameter?

A
  • increases conductance by r^2
  • increases capacitance by only r
  • hence increases speed
23
Q

How can capacitance be reduced?

A
  • use of an insulating material called the myelin sheath

- Schwann cells wrapped around the axon

24
Q

How do synapses work?

A
  • electrical or chemical
  • most are chemical
  • action potential arrives
  • calcium channels open
  • calcium diffuses into pre-synaptic terminal
  • causes release of neurotransmitter from vesicles
  • neurotransmitter diffuses across synaptic cleft
  • detected at post-synaptic receptors (chemical controlled ion gates)
25
Q

What are the different types of post synaptic potentials?

A
  • excitatory = open sodium channels and depolarise membrane

- inhibitory = increase membrane polarisation

26
Q

What happens to neurotransmitters which do not bind with receptors?

A

Metabolised by enzymes and pulled back into the pre-synaptic terminal through reuptake

27
Q

Neuromuscular Junction

A
  • functions the same way as a inter-neuronal synapse does
  • action potential from motor neuron invokes an action potential in innervated muscle fibre
  • action potential propagates bi-directionally from NMJ in same way as action potential does along a nerve fibre
  • induces a shortening of the muscle fibre
28
Q

Parts of NMJ

A
  • motor nerve fibre
  • myelin
  • axonal terminal
  • Schwann Cell
  • active zone
  • sarcolemma
  • synaptic vesicles
  • basement membrane
  • synaptic cleft
  • region of sarcolemma with Ach receptors
  • junctional folds
  • nucleus of muscle fibre
29
Q

What are the senses?

A
  • touch
  • taste
  • smell
  • sight
  • sound
  • balance
  • temperature
  • position
  • force
30
Q

Simple motor control test

A
  • how is motor control regulated with and without sight
31
Q

Reflex test

A
  • what happens when tendon is tapped
32
Q

What does the motor unit consist of?

A
  • motor neuron
  • NMJ
  • muscle fibres it innervates
  • smallest functional block for control of movement
33
Q

How is force controlled?

A

By changing the frequency of firing of the motor neuron and by recruitment of more motor units, beginning with the smallest

34
Q

Large vs. small motor neurons

A
  • largeer = require more excitation = thicker axons = innervate more muscle fibres
35
Q

Feedback through afferents

A
  • short feedback loops allow for fast involuntary reflexes
  • may be mediated by higher control
  • receptor -> sensory neuron -> integrating centre -> motor neuron -> effector
36
Q

Muscle spindle

A
  • a type of displacement transducer

- regulate muscle length by feeding back directly to alpha motor neurons

37
Q

Gamma motor neuron

A
  • innervate muscle spindles
38
Q

Knee jerk reflex

A
  • monosynaptic

- simplest possible reflex

39
Q

Golgi tendon organ

A
  • type of force transducer

- feeds back negatively to motor neuron to regulate muscle tension

40
Q

How do sensors respond to passive stretch?

A
  • muscle spindles lengthen
  • output a train of action potentials
  • when muscle is activated, spindle is shortened and becomes ‘silent’
41
Q

How do sensors respond to active stretch?

A
  • force is applied to the Golgi tendon organ
  • outputs a train of action potentials
  • activation of the muscle produces the same effect

Clinical Measurements (11 decks)

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