ses 4 Flashcards
what is the location of cell bodies of lower motor neurons
lamina IX
Where are the gamma neurons found and what is their function
in the spinal cord and they increase sensitivity of stretch reflexes
define motor unit
A lower motor neuron and all the muscle fibres it supplies
define reflex
Involuntary, unlearned, reputable, automatic reaction to specific stimuli that does not require involvement of the brain
How is the length of the muscle detected
muscle fibres (intrafusal) are located in the middle of the muscle and sense changes in length firing with stretch
what is the reflex arc
neural path\y involved in reflex; receptor=>afferent fibre=>integration centre=>efferent fibre=> effector
Define stretch reflex
hardwired connection between LMN and afferents of muscle-length senses organs
what does myosynaptic/ myotatic reflex refers to
single synapse involved with single jerk, descending inhibition of multi synaptic reflexes
where is the information sent with eliciting of a reflex
brain via dorsal column, cerebellum via spino-cerebellar tract, spinal motor neuron
what stimulates hyperreflexia
sleep, alcohol consumption
what stimulates hyporeflexia
inhibition from descending pathways
What reflexes can be elicited in upper limb and what nerve roots do they test
biceps and brachioradial =>C5/6; triceps => C6/7
What reflexes can be elicited in lower limb and what nerve roots do they test
Quadriceps reflex =>L3/4 and Achilles S1/2
What is the flexor reflex
It is a complex set of reflexes mediated in response to a noxious stimulus that allows coordinated response, polysynaptic
What is the muscle tone like in development
low in-utero, absent in new born
Name some extrapyramidal signs
pill rolling trauma, choreiform movements, Parkinsonian gait, loss of facial expression, cog-wheel rigidity, intention trauma, Dysdiadochokinesis
what is Dystonia
sustained muscle contractions cause twisting and repetitive movements or abnormal postures
what is the cause for extrapyramidal signs
Damage to basal ganglion
what are the causes of pyramidal signs
upper motor lesions
what are the signs of +ve Babinski sign
dorsiflexion of hallux and funning out of the toes
what does the Romberg’s tests tests
positive => loss of balance especially with closed eyes
what are the common signs of LMN lesions
fasciculation, hyporeflexia, atrophy, reduced power, sensory loss
what are the common signs of UMN lesions
hyperreflexia, weakness, reduced atrophy, pronator draft, +ve Babinski and Romberg’s tests deficit in half’s/quarters
What portion of the nerve can be affected and what is the prognosis for each
cell body => irreversible ; axon=> some potential to re-grow
When does tonic synaptic inhibition of alpha-motor neurons occurs and why is it important
REM sleep avoids extraocular and respiratory muscles. Stop acting out of the dreams
what is the role of gamma neurons
modulation of alpha fibres=> activation increases tone
name a drug that can induce Parkinsonism
Haloperidol, CO poisoning
what is cerebellar ataxia
problem with movement execution
What are the pyramidal signs
extensor planter reflex, hyperreflexia, clasp-knife rigidity
what causes outflow incontinence
Automatic bladder=> lesion of S2-4 => nocks out pudendal and parasympathetic supply to the bladder
What is automatic reflex bladder
spinal cord damage above sacral region leading to reflex voiding (hyper-reflexia)
What is a result of spinal cord damage above T10 on the bladder
all of the innervation lost => constant dripping of urine
what is a Hemiparetic gait
pyramidal damage => rigidity associated walk with leg extended and circumducted
