Block 2 - Sensory and motor neurons

Question 1

What are the 2 types of resistance in neurons?

Answer 1

Longitudinal
Medial

Question 2

What is the ‘perfect’ neuron comprised of in terms of resistance?

Answer 2

High medial resistance
Low longitudinal resistance

Question 3

What is decay defined by?

Answer 3

Space constant and time constant

Question 4

What is space constant? Give an equation

Answer 4

How far the voltage travels
Square root of medial / longitudinal resistance

Question 5

What is time constant? Give an equation

Answer 5

How fast a voltage travels
Medial resistance x medial capcitance

Question 6

What is capacitance?

Answer 6

Tendency of the membrane to store charge

Question 7

How do you increase conduction velocity?

Answer 7

Increase space constant
Decrease time constant

Question 8

What is the resting potential of mammalians?

Answer 8

-60-70 mA

Question 9

What are the actions of hyperpolarisation and depolarisation

Answer 9

H - increases potential, so less likely to fire
D - decreases potential, so more likely to fire

Question 10

How does the sodium-potassium pump work?

Answer 10

For 1 molecule of ATP:
2 x potassium in
3 x sodium out

Question 11

When does voltage gated ion channels open?

Answer 11

When depolarisation reaches threshold

Question 12

What are the 3 states of a sodium channel?

Answer 12

Open
Closed
Deactivated

Question 13

What are the states of a potassium channel?

Answer 13

Open
Closed

Question 14

Describe the process of an action potential.

Answer 14

Cell membrane depolarises
Threshold reached = sodium channels open
Further depolarisation
Adjacent channels open
Potassium channels open slowly
Sodium channels close and temporarily deactivated

Question 15

By which feedback is sodium and potassium controlled?

Answer 15

Sodium - negative feedback
Potassium - positive feedback

Question 16

What does the refractory period ensure?

Answer 16

AP travel in one direction - orthodromic

Question 17

Which electrode depolarises neurons?

Answer 17

Cathode

Question 18

Name 2 rate limiting factors of an AP?

Answer 18

Na+/P+ channels opening and closing
Temperature

Question 19

What is the effect of diameter on neuronal conduction?

Answer 19

Space constant increases
Time constant stays the same

Question 20

Where does passive ionic conduction occur in neurons surrounded by myelination?

Answer 20

Nodes of Ranvier

Question 21

Does myelination increase medial or longitudinal resistance?

Answer 21

Medial

Question 22

What are the slowest types of fibres?

Answer 22

C-fibres - pain fibres

Question 23

In which direction does artificial stimulation of a neurone occur?

Answer 23

Both directions

Question 24

Conduction velocity equation

Question 25

Which conditions are a result of demyelination?

Answer 25

Multiple-sclerosis Guillan-Barre syndrome

Question 26

Process of AP at a neuromuscular junction.

Answer 26

AP stimulates release of neurotransmitter across NMJ AP spreads across sarcolemma and down T-tubules Stimulates release of calcium Calcium binds to troponin and allows formation of cross bridge cycle

Question 27

Where is the cell body of the motor neuron found?

Answer 27

Ventral horn

Question 28

What is a motor unit?

Answer 28

A motor neurone and all the fibres it innervates

Question 29

What 3 factors affects fusion of twitches to produce tetanic force?

Answer 29

Fatigue Temperature Fibre type

Question 30

What are the 2 mechanisms that allows generation of extra force?

Answer 30

Recruiting more motor units Increasing frequency of firing

Question 31

What does high innervation of muscle mean?

Answer 31

Lower of precise control

Question 32

What are fast fibres characterised by in terms of an AP?

Answer 32

Higher resting membrane potential Great sodium channels Faster AP

Question 33

Which type of contraction produce more force, but EMG is smaller?

Answer 33

Eccentric

Question 34

When is force optimal?

Answer 34

When cross-bridge overlap is optimal

Question 35

Why is force well maintained at 50% force?

Answer 35

Greater reserve capacity and recruits additional fibres

Question 36

Why does force reduce at 100%?

Answer 36

No reserve capacity Muscle wisdom

Question 37

What is muscle wisdom?

Answer 37

Build-up of metabolites Suppressing motor neuron firing Decreasing force

Question 38

Why does muscle wisdom occur?

Answer 38

Reduce neuronal fatigue Maintain control of fine skills

Question 39

What is high frequency fatigue and when does it occur?

Answer 39

Caused by high continuous frequency stimulation Recovers immediately Due to failure of AP spreading across sarcolemma and t-tubules

Question 40

What is low frequency fatigue?

Answer 40

Caused by intense exercise Days of recovery Due to damage to the tissue which impairs calcium release from SR

Question 41

What is twitch interpolation?

Answer 41

Increase force = decrease twitch interpolation Increase fatigue = increase twitch interpolation

Question 42

Methods of measuring muscle activity?

Answer 42

EMG AMG Ultrasound

Question 43

How do you measure changes in control due to fatigue?

Answer 43

EMG/AMG