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ANP1106 > Lecture 3: Sensorimotor System > Flashcards

Lecture 3: Sensorimotor System Flashcards

1
Q

Describe Somatic Division of the PNS

A

Skin
Muscles
Joints –> Brain
Brain –> Muscle

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2
Q

Describe the Autonomic Division of the PNS

A

Involuntary functions: Heart, smooth muscles, gut and glands
visceral sensations
Motor control if viscera, vascular system and exocrine glands
sympathetic and parasympathetic

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3
Q

Describe the Spinocerebellar Pathway
Sensory Information
Conscious Sensation
First Synapse
Second Synapse
Third Synapse

A

SI: Muscle and Tendon Stretch
CS: NO
FS: Spinal Cord/Dorsal Horn
SS: Cerebellum
TS: -

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4
Q

Describe the Dorsal Column-Medial Lemniscal Pathway
Sensory Information
Conscious Sensation
First Synapse
Second Synapse
Third Synapse

A

I: Fine Touch, vibration, proprioceptors
CS: Yes
FS:Medulla Oblongata
SS: Thalamus
TS: Somatosensory Cortex

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5
Q

Describe the Spinothalamic
Sensory Information
Conscious Sensation
First Synapse
Second Synapse
Third Synapse

A

I: Pain, temperature, course touch, pressure
CS: Yes
FS: Spinal Cord/Dorsal Horn
SS: thalamus
TS: Somatosensory Cor

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6
Q

In which direction do Descending Pathways send impulses?

A

Deliver efferent impulses from the brain to the spinal cord

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7
Q

Name to the 2 groups of descending pathways.

A
  1. Direct Pathways: pyramidal tracts
  2. Indirect Pathways: all others
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8
Q

Which 2 neurons do motor pathways involve?

A
  1. Upper motor neurons:
    • pyramidal cells in the primary cortex
  2. Lower motor neurons
    • ventral horn motor neurons
    • innervates skeletal muscles
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9
Q

Describe direct (pyramidal) pathways

A

impulses from pyramidal neurons in precentral gyri pass through pyramidal (lateral and ventral corticospinal) tracts

Descend directly without synapsing until axon reaches end of tract in spinal cord

in spinal cord, axons synapse with interneurons (lateral tract) or ventral horn motor neurons (ventral tract)

Direct pathway regulates fast and fine skilled movements

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10
Q

Describe Indirect pathways (multineronal)

A

Complex and multi synaptic

Includes Brain stem, motor nuclei and all motor pathways, except pyramidal pathways

These pathways regulate: axial muscles that maintain balance and posture

Muscles controlling coarse limb movements

Head, neck and eye movements that follow objects in visual field

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11
Q

What occurs at the Neuromuscular Junction

A

ACh is released from the presynaptic terminal
- muscle is depolarized
- end potential spreads to adjacent areas of the sarcolemma
- Action potential triggers muscle contraction

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12
Q

Explain Inborn (intrinsic) Reflex

A

Rapid involuntary, predictable motor response to stimuli
- maintain posture, control visceral
activities
- Can be modified by learning and
conscious effort

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13
Q

Explain Learned (Acquired) Reflexes

A

results from practice and repetition
- driving skills

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14
Q

What are the 5 Basic Components of all Reflex Arcs

A
  1. Receptor
  2. Sensory Neuron
  3. Intergration Center
  4. Motor Neuron
  5. effector
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15
Q

Explain Somatic Reflex

A

Active skeletal muscles

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16
Q

Explain Autonomic (visceral) reflexes

A

Activate visceral effectors (Smooth or cardiac muscles or gland)

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17
Q

Explain Somatic Spinal Reflex

A

Occur without direct involvement of high brain centers
- the brain is still advised of a spinal reflex activity, which may have an effect on the reflex

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18
Q

What is testing Somatic Reflexes Clinically important?

A

Assess conditions of the nervous system
- If exaggerated, distorted or absent - it may indicate degeneration or pathology of specific nervous system regions

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19
Q

What are the most common Somatic Reflex assessed?

A

Stretch
Flexor
Superficial Reflexes

20
Q

Describe Muscle Spindles

A

Composed of 3-10 modified skeletal muscle fibers called Intrafusal muscle fibers that are enclosed in a connective tissue capsule

21
Q

What is missing from Central Regions of Intrafusal Fibers?

A

myofilaments and are non contractile

22
Q

What do the end regions of the intrafusal muscle fibers contain

A

actin and myosin myofilaments and can contract

23
Q

End regions of the intrafusal muscle fiber contain actin and myosin and can contract
True or False?

24
Q

What are Regular Effector Fibers of the muscles called?

A

Extrafusal Muscle Fibers

25
What are the two types of afferent endings in muscle spindles
1. Anulospiral Endings (Primary sensory) 2. Flower Spray Endings (secondary sensory)
26
Describe the Anulospiral Ending of the Muscle Spindle
Primary sensory endings that wrap around the spindle and are stimulated by rate and degree of stretch
27
Describe Flower Spray Endings
Secondary sensory endings that are small axons at spindle ends and are stimulated by degree of stretch only
28
Describe the Contractile End Regions of Muscle Spindles
They are innervated by gamma efferent fibers that help maintain spindle sensitivity
29
What are Extrafusal Fibers innervated by?
alpha efferent fibers of large alpha motor neurons
30
What are 2 ways that muscles spindles are excited
1. external stretch: external force lengthens entire muscle 2. internal strectch - gamma motor neurons stimulate spindle ends by contracting and stretch the stretch results in increased rate of impulses to the spinal cord
31
What is the knee-jerk reflex?
is a stretch reflex that keeps knees from bucking when you stand upright
32
Explain the purpose of Stretch Reflex
Maintains muscle tone in large postural muscles and adjusts it reflexively
33
How does the stretch reflex work?
stretch activates muscle spindle sensory neurons synapse directly with alpha motor neurons in spinal cord alpha motor neurons cause extrafusal muscle of stretched muscle to contract
34
What is Reciprocal Inhibition
occurs with muscle stretch afferent fibers synapse with interneurons that inhibit alpha motor neurons of antagonistic muscles ex. in patellar reflex, stretched muscle (quads) contracts
35
All stretch reflexes are (2):
1. monosynaptic 2. ipsilateral (motor activity is on same side of body)
36
What do Positive Reflex Reactions tell you?
1. proves that sensory and motor connections between muscle and spinal cord are intact 2. Strength of response indicates degree of spinal cord excitability
37
Explain Tendon Reflexes
involves poly synaptic reflexes helps prevent damage due to excessive stretch important for smooth onset and termination of muscle contraction produces muscle relation (lengthening) in response to tension
38
How do muscles reposnd to strecth in tendon reflexes?
Muscle relaxation (lengthening) - contraction or passive stretch activates tendon reflex - afferent impulses transmitted to spinal cord - information transmitted simultaneously to cerebellum and used to adjust muscle tension
39
What is Reciprocal Activation?
contracting muscle relaxes and antagonist muscle contracts
40
Explain the Flexor (withdrawal) Reflex
it is initiated by painful stimulus and causes autonomic withdrawal of threatened body part - ipsilateral and polysynaptic - protective and important to survival - Brain can override - knowing that a finger prick is coming for a blood test, you brain can tell you body not to pull away
41
What is the Crossed-Extensor Reflex
occurs with flexor reflexes in weight-bearing limbs to maintain balance - ipsilateral withdrawal reflex and contralateral extensor reflex causing the stimulated side to withdraw (flex) and contralateral side to extend - stepping barefoot on broken glass causes the damaged leg to withdraw and the opposite leg to extend to support weight shift
42
Superficial Reflexes
are elicited by gentle cutaneous stimulation of area
43
why are superficial reflexes important?
signal problems in upper motor pathways or cord-level reflex arcs
44
What are the two best known superficial reflexes?
1. Plantar Reflex 2. Abdominal Reflex
45
Describe the Plantar Reflex
Tests the integrity of cord from L4 to S1 Stimulus: the lateral aspect of sole of foot Response: downward flexion of toes Damage: motor cortex or corticospinal tracts causes abnormal response known as Babinskis Sign
46
What is Babinskis Sign
Signifies damage to the motor cortex or corticospinal tracts - Hallux dorsiflexes; smaller toes fan laterally - Norma in infancy to age 1 because myelination is still incomplete
47
Abdominal Reflexes
Tests integrity of cord from T8-T12 Stimulus: Strokeing skin of lateral abdomen above, below or to the side of the umbilicus Response: contraction of abdominal muscles and movement of imbilicus toward stimulus vary in intensity from one person to another and is absent when sprticospinal tract lesions are present

ANP1106 (10 decks)

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