Sensory Systems Flashcards

1
Q

Medial Lemniscal System Pathway General Information

A

Several Pathways
Merge into 1 large pathway
Point to Point somatotopic organization

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2
Q

Ascending Reticular Formation General Information

A

Primitive
Base of everything in nervous system
Input from all receptors
Important for arousal and deep pain

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3
Q

Four Aspects of a Stimulus

A

Modality- What kind of stimulation is it (Mechano, thermal, etc.)
Intensity- Conveyed by temporal summation (increased impulse frequency) and spatial summation (increased number of nerve fibers)
Duration- How long
Location- Where (somatotopic)

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4
Q

Proprioceptive Mechanoreceptors

A

Provide information about the effect of gravity on muscles as well as the differences between actual & intended movements
Provide feedback critical for appropriate CNS control of LMNs

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5
Q

Two types of muscle proprioreceptors

A

Muscle Spindle- Responds in change to length (Buried within muscle)
Golgi Tendon Organ- Responds to tension (on tendon)

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6
Q

Muscle Spindle Receptors

A

Stretch receptor present in most skeletal muscles
Sends information that is processed by the cerebrum via multiple tracts to determine position of body parts and the cerebellum via the spinocerebellar tracts to provide proprioceptive feedback on the position of body in space to help with coordination of movement. Also goes to reflex pathways

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7
Q

Coordinated Movement via Cerebellum

A

To achieve this cerebellum needs information:
Position of limbs via muscle spindles
Position of head and body in space via vestibular system
Intended movement via motor system

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8
Q

Muscle Spindle Anatomy

A

Composed of 4-8 intrafusal muscle fibers enclosed in a fibrous capsule that run in parallel with extrafusal muscle fibers

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9
Q

Extrafusal Muscle Fibers

A

Big muscle fibers (like in quadriceps)
Innervated by alpha motor neuron
Motor unit consists of extrafusal muscle & alpha motor neuron

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10
Q

Intrafusal Muscle Fibers

A

Innervated by gamma motor neuron
Fibers themselves are a proprioceptor. Detect static (chain fibers) and dynamic (bag fibers) changes in length.
Walled off by a fusiform collagen sheath
Ends are contractile area, middle is receptor. Stretch of the ends or extrafusal fibers cause stimulation of receptor.

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11
Q

Muscle Spindle Reflex

A

Muscle is stretched, lengthening intra and extrafusal fibers in parallel
Primary a1 afferent neuron discharges
Monosynaptic reflex arc causes firing of LMN alpha motor neuron in spinal cord
Muscle is shortened and spindles are shut off
So the result of reflex is muscles contraction
Function: Smooths and stabilizes movement

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12
Q

Tendon Reflex

A

Same exact thing as muscle spindle reflex used for neurological exam
Tapping tendon causes rapid/transient muscle stretch

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13
Q

Voluntary Movement

A

Mostly mediated indirectly through gamma motor neuron
Called gamma alpha loop
Gamma motor neuron is tonic

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14
Q

Golgi Tendon Organ

A

Connected in series with muscle fibers
Deformed with muscle contraction or stretch, firing 1b afferent neuron to ascending pathways for proprioception or segmentally for reflex

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15
Q

Golgi Tendon Organ Reflex

A

Safety mechanism for too much tension, relaxes muscle.
Polysynaptic reflex with inhibitory interneuron to inhibit muscle and cause relaxation. Also stimulates antagonistic muscle through a separate interneuron and efferent neuron

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16
Q

Nerve Fibers of Spinal Cord (by diamteter)

A
Large diameter fibers transmit info. about touch, pressure & proprioception
Small diameter (unmyelinated) fibers relay nociception & temperature