Lecture 3 - The Role Of Efferencekopie and proprioreceptors Flashcards
Discuss Krogh (1913) experiment?
Had 6 subjects cycle on ergometer, ex onset increased ventilation at 1 sec and clearly over first 12 seconds
- this indicates too fast for metabolite, proprioceptors, or increased CO2 production as it fell, therefore by elimination must be cortical irradiation through the CRR generator
Discuss the Galbo (1987) curarisation experiment??
Failed to measure PaCO2 and VCO2, had 10 men perform ergo at 91%VO2 max, followed by partial nmb with tubocurarine..
Handgrip strength and work done was reduced by ~60%
Also breathed 15l/min higher than controls at equiv Vo2
Issue is very small response - dunno if small effect of EK or not enough curare.
Discuss the efferencekopie experiment regarding unilateral weakness???
Innes (1992) - one legged cycle ergometer in 8
Vo2 increased 5x (0.2-1.0) and Ve from 10-30L/min in control of legs with weakness
Same workload achieved in both legs
Breathing during exercise with the weak leg was 8L/min higher and became hypocapnic by 4 mmhg but still trivial.
Discuss the Goodwin & McCloskey (1972) spindle reflex vibration experiments???
Used vibration to measure breathing against isometric contraction of biceps at a constant force.
Tendon vibration did decrease breathing but the difference was minimal but data is very messy i.e., pooled data not shown and the 1 data point shown was in on it
What did Eldridge et al (1985) find???
Had 36 unaesthetised cats and performed electrical stimulation of the subthalamic locomotor region which induced walking.
This stimulation caused an increased Ve, Hr, BP often before locomotion.
No strong evidence in man, not exhaustive of all areas and no anatomical link to respiratory system.
What did Fink and Guz (1995) investigate ??
Used PET to measure relative cerebral blood flow to identify sites of increased neuronal activation during pre and post ex.
Showed increased in relative CBF in contralateral primary motor cortex but no increase in the subthalamic areas as Eldridge predicted.
But, each scan took 15 seconds and it’s a much longer time resolution than that!
Discuss the electrical stimulation experiments in paraplegics of both Adams (1984) and Brice (1988)???
Adams electrically stimulated 18 quads to increase Ve and Vco2 2 fold. - the Ve increase was the same in voluntary and EEL.
Brice (1988) found EEL increased Vex2 in paraplegics - showed a linear relationship between Ve and VCO2 not sig different from intact subjects.
Issue that subjects e.g. AdamS, could just voluntarily increase breathing- such small Ve increases it’s all questionable.
State Harrison et al (1932) findings regarding proprioceptive feedback???
Had 3 subjects and showed active and passive hand opening increased Ve by only 2L/min
Discuss the Comroe (1943 +1944) experiments??
In 1943, had 11 subjects and showed 10-50% increases in ventilation via increases in frequency and Tv. This was abolished in 4/11 when giving a spinal anaesthetic. Method was to hang leg over bench and motor flex knee at 100bpm.
In 1944, had n=16 and showed active moves caused a 57% increase in Ve at 1 min and 13% more at 2 min.
Discuss the key proprioceptor paper; Hutt (1958)??
Had 10 men perform passive movement. Showed Ve increased with the number of joints moved.
Vo2 doubled from 1 joint to contro,
Dose -response just about plausible regarding Ve and number of joints used.
But no proprioceptor exp increase breathing by even 1.5x fold, trivial increases compared to max ex
Is there a drive to breathe from muscle proprioreceptors?? - refer to Fernandes (1990)
Performed an epidural anaesthesia of sensory afferents from T10-11
6 subjects performed bike ergo @ 57% Vo2 until exhaustion - showed this epidural had no effect on Ve or Hr response.
We don’t know if the epidural completely blocked the muscle chemoreceptors muscle pressure response - we can’t be sure all sensory afferents pathways were blocked, since they could voluntarily control muscles below the block.
