Reflex arcs, DTR, clonus, tonic reflexes

monosynaptic reflex arc

receptor (MS) to 1a afferents to excitatory contraction of extrafusal agonist mm

disynaptic reflex arc

Ia fiber branches to inhibitory interneuron to antagonist mm

grading deep tendon reflexes

0-absent

+: hypoactive (diminished)

++:normal

+++:brisk (increased)

++++:hyperactive (clonus)

continuum of tone

hypertonic---normal----hypotonic

what do you use modified Ashworth scale for

move people to elongate mm, feeling resistance as soon as you elongate. This only categorizes hypertonicity

Deep tendon reflexes are what type of arc

monosynaptic reflex arc

DTR activates what

Ia phasics (due to quick on/off of tendon tap)

-responsible for tone

-responsible for clonus

Hypertonic

uncontrolled or uninhibited reflex arc activity

-likely have damaged inhibitory descending tracts or cortical areas

-UMN injury

hypotonic

under facilitated reflex arc activity

-likely have damaged facilitatory descending tracts or cortical areas

-UMN or LMN injury

clonus

sustained monosynaptic reflex arc

LMN

peripheral nerves, nerve root at spinal cord

UMN

damage to spinal cord or cortex (brain)

Tonic reflexes are a resistance to

stretch

how to assess tonic reflexes

modified ashworth scale

0=typical

1,-4 for increased tone/hypertonicity

no grade for hypo