1
Q
Cortical reflexes
A
- Hopping
- Placing
2
Q
Midbrain/Brainstem reflexes
A
- Suckling
- Vestibular
- Righting
- Yawn
- Head/eye mvmts
3
Q
Spinal reflexes
A
- Stretch (myotatic)
- Golgi tendon
- Crossed extensor
4
Q
How to tell b/w reflex and volitional mvmt?
A
Speed!
5
Q
Components of intrafusal fibers in muscle spindle?
A
Motor and sensory
6
Q
Sensory portion of intrafusal fibers?
A
- NOT contractile
- Portion sensitive to length
- 2 sensors (nuclear bag fiber and nuclear chain fiber)
7
Q
Primary afferent in intrafusal fibers
A
- Ia fiber (large and myelinated)
- innervates both nuclear bag and nuclear chain
- Sensitive to length of muscle and how fast length is changing
8
Q
Secondary afferent in intrafusal fibers
A
- Group II fiber (smaller, myelinated)
- innervates ONLY nuclear chain
- Sensitive to length of muscle ONLY
9
Q
Motor Efferent of intrafusal fibers
A
- Gamma MN innervates
- Controls length of muscle
- same histo as skeletal m.
10
Q
What happens when the intrafusal muscles are contracted?
A
Sensory portion is stretched –sensory portion is more sensitive to superimposed stretch
*Overall length is NOT changing though
11
Q
Characteristics of myotatic reflex pathway?
A
- Contraction(shortening) of stretched muscle
- Protects muscle from tearing
- Initiated by muscle spindle
- Monosynaptic/segmental
12
Q
Characteristics of Golgi tendon reflex?
A
- Sudden/abrupt relaxation of contracted m.
- Protects muscle from damage d/t excess force
- Initiated by GTO
- Polysynaptic/segmental
13
Q
GTO
A
- Innervates tendon
- Bare nerve endings
- APs increase with increased tension
- Ib fiber to SC
14
Q
Spinal Shock
A
- d/t transection of SC
- All reflexes abolished, even w/ intact circuit
- Hyperpolarization of spinal neurons d/t loss of excitatory input from cortex
15
Q
Decorticate Posturing
A
- Flexed UE
- Extended LE
- Common cause = CVA @ internal capsule
16
Q
Decerebrate posturing
A
- Contraction of all anti-gravity muscles (UE extended)
- ## Loss of input from all structures rostral to pons/caudal to red nucleus
17
Q
Rigidity
A
- Resists motion in all directions d/t maintained muscle contraction
- Continuous activation of gamma MNs
18
Q
Spasticity
A
- Resists motion in a given direction d/t hyperactive myotatic reflex
- Continuous activation of gamma MNs (contracts intrafusal muscles – lengthens nuclear bag/chain
19
Q
Spasticity and reflexes
A
- Brainstem facilitory region ACTIVATES gamma MNs (spindle more sensitive)
- spontaneously active
- Brainstem inhibitory region INHIBITS gamma MNs (spindle less sensitive)
20
Q
Spasticity and cortical damage
A
- Brainstem inhibitory region is lost … brainstem facilitory region predominates – uncontrolled brainstem facilitory region have stretch reflexes that fight passive motion
Neuro 2 Exam
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Decks in class (4)
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