Neurology 4 Flashcards
what is the central tube in the middle of the spinal cord called?
central canal
what type of neuron is affected when there is a lesion on the ventral motor neuron?
lower motor neuron
what are the three columns that are present n the spinal cord?
anterior
lateral
posterior
what are tracts?
myelinated axons pathways
what are nucleii?
cell bodies in white matter (CNS)
how many neurons are there between peripheral receptor and the cortex?
3
where do the three neurons synapse from the peripheral receptor to the cortex?
receptor -> grey matter in spinal cord/medulla
(neuron then crosses over to the contralateral side)
medulla -> nucleus in contralateral thalamus
thalamus -> parietal cortex
in which column of the spinal cord do sensory neurons travel in ?
posterior column
how many neurons are involved in pain and temp. detection ?
3
where do pain and temp. neurons cross over to the contralateral side?
at the same spinal level they entered
where do sensory neurons cross over to the contralateral side ?
inferior to the pyramids of the medulla
how many neurons are involved in motor descending tracts of the spinal cord?
2
where do motor neurons originate from?
cerebral cortex and brain stem
where do motor neurons cross over the to contralateral side?
pyramidal decussation in medulla
in which column of the spinal cord do motor neurons travel down?
lateral column
what are the two responsibilities of the lower motor neurons?
muscle tone
reflexes
what happens to the reflex if the lower motor neurons are affected?
absent or reduced
what happens to the reflex if the upper motor neurons are affected and lower motor neurons are intact?
reflexes and tone are exaggerated
can reflexes be monosynaptic ?
yes
is a reflex voluntary ?
no
name a monosynaptic reflex
stretch reflex
name a polysynaptic reflex
flexor reflex
state a 6 stages of the stretch reflex
- the tendon is stretched
- intrafusal muscle fibres are stimulated
- sensory neuron is stimulated
- motor neuron is activated for the agonist and antagonist muscle
- muscle is contracted and relaxed
why are stretch reflexes important?
control muscle tone and posture
during a stretch reflex do the neurons APs travel up to the CNS ?
no
- the neurons stay in the spinal level they entered at
if someone wants to voluntarily contract a muscle do the neurons need to travel up to the CNS?
yes
is muscle tone increased or decreased during sleep?
decreased
are upper or lower motor neurons involved in the stretch reflex and flexor reflex?
lower motor neurons
what happens to the reflexes if the upper motor neurons are damaged ?
the reflexes are exaggerated
there is a lesion at C3 on the left side which results in the- pyramidal tract
spinothalamic tract and
posterior column
being abrupted on the left side.
what would be the sensory and motor lose?
Left side
- paralysis
- loss of touch and vibration
- reflexes are exaggerated
Right side
- loss of temp and pain sensation
(this is because pain/temp nerves cross to the contralateral side as soon as they enter the spinal cord )
are autonomic responses voluntary ?
no
how many neurons are there in the autonomic pathway ?
2
- preganglionic
- postganglionic
what is the outflow of sympathetic and parasympathetic ?
sympathetic = thoracic-lumbar parasympathetic = cranio-sacral
what autonomic response has a long preganglionic neuron?
parasympathetic
how many neurons are in ascending sensory tracts?
3
how many neurons are in descending motor tracts ?
2
