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Physiology 1 > Exam 2: Neurophysiology Part 1 - Muscle Receptors and Central Control of Movement > Flashcards

Exam 2: Neurophysiology Part 1 - Muscle Receptors and Central Control of Movement Flashcards

1
Q

What is a reflex

A

Involuntary, quantitatively unvarying response of the nervous system to a stimulus

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2
Q

Components of a reflex arc (5)

A
  1. Receptor
  2. Sensory Neuron
  3. One or more synapses (interneurons) in the CNS (polysynaptic or monosynaptic reflexes)
  4. Motor Neuron
  5. Target Organ
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3
Q

What do sensory receptors collect and what do they turn them into

A

Environmental signals

Turn them into a cellular response (Action Potential)

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4
Q

What is a primary receptor

A

A neuron with a peripheral ending specialized for stimulus transduction

Ex - retinal photoreceptors

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5
Q

What is a secondary receptor

A

A non-neuronal cell designed for stimulus transduction that affects an adjacent neuron

Ex - hair cell in inner ear

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6
Q

3 different types of reflexes

A

Segmental
Intersegmental
Suprasegmental

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7
Q

Segmental reflex arc

A

Occurs in small segment of spinal cord

Info doesn’t travel to brain - spinal cord deals with info and sends signal to organ

Ex - knee jerk reflex, pupillary light reflex

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8
Q

Intersegmental reflex

A

Info travels to other parts of the CNS - upper spinal cord

Ex - cutaneous trunci reflex

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9
Q

Suprasegmental reflex

A

Requires connection with the brain

Ex - vestibulospinal reflex, proprioceptive positioning reflex

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10
Q

How does CNS control body movement (3)

A
  1. Assessing effect of gravity on body muscles
  2. Determining initial position of body parts to be moved
  3. Detecting any discrepancy between the intended movement and what actually occurred
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11
Q

How does CNS get info about movement

A

Muscle stretch receptors

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12
Q

Types of muscle stretch receptors

A

Muscle spindle

Golgi tendon organ

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13
Q

What type of fibers are in a muscle spindle receptor

A

Intrafusal fibers

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14
Q

How are fibers in the muscle spindle receptor arranged

A

Intrafusal fibers are arranged in parallel with the extrafusal muscle fibers

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15
Q

What does the muscle spindle receptor detect

A

Muscle stretching

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16
Q

How are fibers in the Golgi tendon organ arranged

A

Arranged in series with extrafusal muscle fibers located in the tendon of muscles

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17
Q

What does Golgi tendon organ detect

A

Muscle tension produced by contraction

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18
Q

What types of neurons innervate the muscle spindle receptor

A

Sensory - Ia and II afferent neurons

Motor - gamma motor neuron to intrafusal fibers and alpha motor neuron to same muscle and to an antagonistic muscle

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19
Q

3 effects of muscle spindle receptor activation in the spinal cord

A
  1. EPSP on a-motor neuron returning to same muscle –> muscle contraction
  2. IPSP in a-motor neuron of the antagonist muscle via synapsis with an inhibitory interneuron
  3. Concurrently: y-motor neurons located at the polar ends of intrafusal fibers cause shortening of the spindle’s polar regions –> the spindle receptor thus remains both morphologically and functionally intact
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20
Q

Activity of Ia and II muscle fibers during different muscle phases

A
  1. Static phase
    Ia and II - evenly spaced AP
  2. Dynamic phase - stretch
    Ia - Very active, increased firing rate, lots of AP
    II - Increased firing rate, but not as fast as Ia fibers
  3. Static phase
    Ia and II - Evenly spaced AP, but more than in first static phase
  4. Dynamic phase - shortening
    Ia - Does not produce any AP
    II - Does produce AP but not a lot
  5. Static phase
    Ia - Have AP again, but not a lot in beginning of phase because needs time to get started again after not having any APs
    II - still have AP and are more frequent than in the shortening phase
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21
Q

What happens to the golgi tendon organ during muscle contraction

A

Tension is applied to the golgi tendon organ causing the collagen fibrils to tighten

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22
Q

Mechanism of golgi tendon organ

A

APs are sent to the CNS via sensory neuron and induce IPSP in the a-motor neuron returning to the same muscle

Decreased extrafusal muscle fiber contraction

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23
Q

Lower motor neuron

A

a-motor neuron

Cell body and dendrites are located in CNS

Axons extend out through peripheral nerves to skeletal muscles

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24
Q

Upper motor neuron

A

Lies completely in the CNS

Controls the lower motor neuron

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25
Q

Recognizing disease of lower motor neurons (4)

A

Paralysis (no muscle contraction) or paresis (incomplete paralysis)

Atrophy (wasting of skeletal muscle mass distal to lower motor neuron lesion)

Loss of segmental and intersegmental reflexes

Changes in electrical activity of the muscle (observed by electromyogram)

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26
Q

Recognizing upper motor neuron disease (4)

A

Inappropriate movement (due to no control of lower motor neurons if upper motor neurons not functioning)

NO atrophy

Exaggerated segmental reflexes

Normal electromyogram

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27
Q

Define corticospinal

A

Starts in cortex and goes to spinal cord

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28
Q

Motor system functions (4)

A

Maintain posture

Support body against gravity

Provide stable platform for movement

Control voluntary movement and locomotion

29
Q

What results in all movement in animals

A

Flexion and extension of muscles

30
Q

Movement divided into 2 groups

A

Voluntary - learned, conscious, skilled

Involuntary - postural, subconscious, antigravity

31
Q

What is voluntary movement dominated by (flexors or extensors)

A

Flexor muscles

Discrete contraction of muscles located distal to spinal column

32
Q

What is involuntary movement dominated by (flexors or extensors)

A

Extensor muscles

Long-term contraction of large muscles located proximal to spinal column

33
Q

What is needed for muscle fibers to contract

A

Stimulation by an a-motor neuron (lower motor neuron)

34
Q

What is needed for an a-motor neuron to send an AP (2)

A

Signaled to do so by upper descending motor neuron (upper motor neuron)

Signaled to do so by an incoming sensory neuron (reflex arc)

35
Q

Hierarchical organization of the motor system

A

Premotor and supplementary motor cortices - highest

Primary motor cortex

Brain stem

Spinal cord - lowest

36
Q

Can the brainstem induce reflexes

A

Yes
The brain stem is similar to the spinal cord in that it receives sensory information from the head and neck via cranial nerves

37
Q

What is the simplest level in the movement control hierarchy

A

Spinal cord

38
Q

Motor neuron pool

A

Cigar shaped areas extending over few spinal cord segments

Contain the neuronal cell bodies of MN (motor neuron?) units of a given muscle

39
Q

Motor neuron pools of distal muscles location and what kind of movement

A

Located in more lateral parts of ventral horn

Learned skilled movement

40
Q

Motor neuron pools of axial and proximal musculature location and what are muscles for

A

Located more medially in the ventral horn

Posture muscles

41
Q

Where are cell bodies and axons located in the spinal cord

A

Cell bodies are in the grey matter

Axons are in the white matter

42
Q

Where are premotor neurons located and what do they do

A

Located in intermediate zone of ventral horn in spinal column

Activate the lower motor neurons that innervate muscles

43
Q

4 major axon routes from brainstem

A

Vestibulospinal tract

Tectospinal tract

Reticulospinal tract

Rubrospinal tract

44
Q

Which of the 4 major axon routes from brainstem control axial and proximal musculature - involuntary, maintenance of posture

A

Vestibulospinal tract

Tectospinal tract

Reticulospinal tract

45
Q

Which of the 4 major axon routes from the brainstem control distal limb musculature - voluntary, skilled movement

A

Rubrospinal tract

46
Q 
Vestibulospinal tract:
Origin
Sensory input
Information
Function
A

Origin: Cell bodies in vestibular nuclear complex (medulla and pons)

Sensory input: VII cranial nerve (vestibulocochlear nerve) and cerebellum

Information: Position of head and acceleration

Function: Detects disturbances of balance and activates antigravity musculature to counteract

47
Q

Righting relfex

A

Combination of vestibular, ocular, and muscle spindle organs in neck musculature

These together with the vestibulospinal tract aim to restore normal posture in a falling animal

48
Q

Tectospinal tract:
Origin
Sensory input and information
Function

A

Origin: Superior colliculus (midbrain)

Sensory input and information: Visual, auditory, and somatosensory information about the relative position of stimuli in the environment with respect to the organism

Function: Controls muscles that move the head, reflex orientation of head toward environmental stimuli

49
Q

Reticulospinal tract:
Origin
Sensory input and information
Function

A

Origin: Reticular formation (pons and medulla)

Sensory input and information: Sensory information important for pain perception, respiration, circulation

Function: Antigravity regulation

50
Q

Rubrospinal tract:
Origin
Sensory input and information
Function

A

Origin: Cells of the red nucleus (n. ruber) of midbrain

Sensory input and information: Cerebral cortex and cerebellum

Function: Voluntary control of musculature that participates in skilled movement of the extremities (distal limb flexor musculature)

51
Q

Corticospinal tract

A

Pyramidal tract/motor system

Direct projection from cerebral cortex to spinal cord

Most complex level of motor control

Bypasses brain stem

52
Q

Pyramidal tract (corticospinal tract):
Origin
Function
Characteristic

A

Origin: Cerebral cortex, adjacent to frontal lobe

Function: Responsible for the most elaborate and dexterous voluntary movement

Characteristic: Control over small number of a-motor neurons (fractionation)

53
Q

Lateral corticospinal tract

A

Pyramidal cell axons that cross midline at pyramidal decussation - 75-90%

Skilled, manipulative, voluntary movements

54
Q

Signs of damage to lateral corticospinal tract

A

Signs of damage to this tract rostral to the pyramidal decussation causes weakness of the contralateral side of the body (hemiparesis)

55
Q

What is the pyramidal decussation

A

Medulla - spinal cord border

56
Q

Ventral corticospinal tract

A

Pyramidal cell axons that do not cross midline at pyramidal decussation and remain on the same side of the body - 10-25%

Voluntary control of antigravity muscles

Several axons of the ventral corticospinal tract cross the midline locally in the spinal cord

57
Q

What is the highest level of motor control hierarcy

A

Motor cortices

58
Q

Primary motor cortex (MI)

A

Located rostral to the central sulcus, near the cruciate sulcus

Somatotropic map

59
Q

What is a somatotropic map

A

Shows what part of the brain is important in different body parts

60
Q

What does dorsomedial MI activate

A

Muscles in the caudal part of the body

61
Q

What does the ventrolateral MI activate

A

Muscles of the face

62
Q

What happens after stroke in the Primary motor cortex

A

Humans - hemiparesis

Animals - Proprioceptive positioning reaction is slowed with damaged corticospinal tract neurons

63
Q

Supplementary motor cortex and premotor cortex location and where do axons go

A

Located in frontal lobe

Give rise to axons that project to nuclei of descending brainstem motor pathways

64
Q

Function of supplementary motor cortex

A

Simultaneous movement of limbs in order to accomplish a task

65
Q

Function of premotor cortex

A

Preparatory orientation of the body for the execution of a motor task

66
Q

Example of motor cortices in playing the piano

A

Prefrontal motor cortex - orientation of arms and hands

Supplementary motor cortex - planning and organizing the sequence of finger movements

Primary motor cortex - muscle activation necessary to press a single key

67
Q

Basal ganglia (4)

A

Caudate nucleus and putamen (aka striatum)

Globus pallidus

Substantia nigra

Subthalamic nucleus

68
Q

What do basal ganglia do

A

Receive input from cerebral cortices and project back to premotor and supplementary cortices

Help select appropriate movement pattern while suppressing less appropriate competing patterns

69
Q

Basal ganglia and Parkinson’s

A

Striatum and substantia nigra involved in Parkinson’s
These are needed to pick right movement patterns

Accumulation of a-synuclein –> degradation of striatum and substantia nigra basal ganglia –> loss of dopamine in basal ganglia that control muscle tone and movement

Signs: tremors, rigidity, gait disturbance

Physiology 1 (4 decks)

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