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ANP1106 > Sensorimotor System > Flashcards

Sensorimotor System Flashcards

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1
Q

What is an inborn (intrinsic) reflex?

A

A rapid, involuntary, predictable motor response to a stimulus

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2
Q

Give two examples of inborn reflex functions

A

Maintaining posture
Regulating visceral activities

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3
Q

What are learned (acquired) reflexes?

A

Reflexes developed through practice/repetition (e.g., driving skills

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4
Q

What are the 5 components of all reflex arcs?

A

Receptor
Sensory neuron
Integration center
Motor neuron
Effector

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5
Q

What is the receptor’s role?

A

Detects the stimulus

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6
Q

What does the sensory neuron do?

A

Carries afferent signals to the CNS

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7
Q

What is the motor neuron’s function?

A

Carries efferent signals from CNS to effector

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8
Q

What are the two functional classifications of reflexes?

A
  • Somatic reflexes (active skeletal muscle)
  • Autonomic/visceral reflexes (activate smooth/cardiac muscle, glands)
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9
Q

Where are spinal reflexes processed?

A

Spinal cord (without direct involvement of higher brain centers)

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10
Q

What are the 3 most clinically tested reflexes?

A

Stretch reflexes
Flexor reflexes
Superficial reflexes

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11
Q

What two types of proprioceptive input smoothly coordinate skeletal muscles?

A

Muscle length (info sent from muscle spindles)
- Muscle tension (info sent from tendon organs)

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12
Q

What are muscle spindles composed of?

A

3-10 modified muscle fibers (intrafusal fibers) in an enclosed connective tissue capsule

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13
Q

What does the central and end region of intrafusal fibers contain?

A

Central: lack myofilaments and are non contractile
End: contain action and myosin myofilaments and can contract

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14
Q

Extrafusal?

A

Regular effector fibers of muscles

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15
Q

What are the two types of sensory endings in spindles?

A

Anulospiral (primary) endings: ending wrapping around spindle&raquo_space; stimulated by rate and degree of stretch

Flower spray (secondary) endings: small axon of spindle ends&raquo_space; stimulated by stretch only

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16
Q

What efferent fibers innervate spindle contractile end regions?

A

Gamma (γ) efferent fibers: help maintain spindle sensitivity

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17
Q

What fibers innervate extrafusal muscle fibers?

A

Alpha (α) efferent fibers of large alpha motor neurons

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18
Q

What are the two ways to stretch muscle spindles?

A

External stretch (external force lengthens whole muscle)
Internal stretch (γ motor neurons stimulate spindle ends to contract ; stretching spindle)

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19
Q

What happens when spindles are stretched?

A

Increased rate of signals to spinal cord

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20
Q

what occurs during activation of of alpha motor neurons?

A

Only extrafusal muscle fibers contract. Spindle becomes slack and no APs. Unable to signal further length changes

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21
Q

What occurs during coactivation of a-y?

A

Both extrafusal and intrafusal muscle shorten. Tension is maintained and single change in length

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22
Q

Give an example of a clinical stretch reflex

A

Patellar (knee-jerk) reflex

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23
Q

Why is the stretch reflex important for posture?

A

Prevents joint buckling (e.g., keeps knees from collapsing when standing)

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24
Q

all stretch reflexes are ______?

A

monosynaptic and ipsilateral (motor
activity is on same side of body)

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25
What is reciprocal inhibition?
afferent fibers synapse with interneurons that inhibit alpha motor neurons of antagonistic muscles. Eg: patellar reflex, stretched muscle (quadriceps) contracts, and antagonists (hamstrings) relax
26
What type of reflex arc do tendon reflexes use?
Polysynaptic reflexes
27
What is the protective function of tendon reflexes?
Prevents muscle/tendon damage from excessive tension
28
How does the tendon reflex respond to increased tension?
Causes muscle relaxation (lengthening)
29
What happens to antagonists during a tendon reflex?
Reciprocal activation (antagonist contracts)
30
Where is tendon reflex info sent for coordination?
Cerebellum (to adjust muscle tension)
31
What stimulus triggers flexor reflexes?
Painful stimuli
32
Can the brain override flexor reflexes? Example?
Yes (e.g., tolerating a blood draw despite pain)
33
What type of reflex arc do flexor reflexes use?
– Ipsilateral and polysynaptic ▪ Many different muscles may be called into play, so needs to be polysynaptic
34
When does the crossed-extensor reflex occur?
With flexor reflexes in weight-bearing limbs
35
What are the two components of this reflex?
Ipsilateral flexion (withdrawal) Contralateral extension (balance)
36
Example of crossed-extensor reflex?
Stepping on glass → injured foot withdraws, opposite leg extends
37
Superficial reflexes are _______
elicited by gentle cutaneous stimulation of area
38
Superficial reflexes signals problems in ___________
upper motor pathways or cord-level reflex arcs
39
Planter reflex tests integrity of ___________
L4 to S2
40
How is the plantar reflex tested and what is the response?
Stimulus: Stroking lateral sole of foot Response: downward flexion of toes
41
What is Babinski’s sign?
damage to motor cortex or corticospinal tracts. Abnormal response: hallux dorsiflexes, toes fan (indicates CNS damage), Incomplete myelination of corticospinal tracts in infants
42
What spinal levels are tested in abdominal reflexes?
T8–T12
43
How are abdominal reflexes stimulated and what is the response?
stimulus : Stroking abdominal skin near umbilicus Response: contraction of abdominal muscles and movement of umbilicus toward stimulus
44
Clinical significance if abdominal reflexes are absent?
Suggests corticospinal tract lesion
45
What types of sensory info do first-order neurons carry in this pathway?
Touch, proprioception, vibration
46
Where do first-order neurons terminate?
Medulla oblongata
47
Where do second-order neurons originate?
Dorsal horn of spinal cord, Nucleus cuneatus/gracilis (medulla)
48
Where do second-order neurons send impulses?
Thalamus (for most pathways) Cerebellum (for proprioception)
49
Where are third-order neuron cell bodies found?
Thalamus
50
Where do third-order neurons project?
Somatosensory cortex
51
What are the two groups of descending motor pathways?
Direct (pyramidal) pathways Indirect (extrapyramidal) pathways
52
How many neurons are in motor pathways?
Two (upper and lower motor neurons)
53
Where are upper motor neuron cell bodies located?
Pyramidal cells in motor cortex Subcortical motor nuclei
54
Where are lower motor neuron cell bodies located?
Ventral horn of spinal cord, innervating skeletal muscle
55
What is the origin of direct pathways?
Pyramidal neurons in precentral gyri (primary motor cortex)
56
What are the two pyramidal tracts in direct pathway?
Lateral corticospinal tract Ventral corticospinal tract
57
Where do pyramidal tract axons synapse?
spinal cord. Lateral tract: Spinal interneurons Ventral tract: Ventral horn motor neurons
58
What movements do direct pathways control?
Fast, fine, skilled movements (e.g., finger dexterity)
59
Why are indirect pathways called "multineuronal"?
- Involve multiple synapses , complex - include brainstem nuclei and all motor pathways except pyramidal pathways
60
What are 3 key functions of indirect pathways?
Posture/balance (axial muscles) Coarse limb movements Visual tracking movements (head, eye, neck movements)

ANP1106 (8 decks)

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