EXAM 2: Motor System 1

Question 1

feedforward

Answer 1

the anticipatory use of sensory information to prepare for movement

Question 2

feedback

Answer 2

the use of sensory information during or after movement to make corrections either to ongoing movement or to future movements

Question 3

Automatic movements require continuous integration of:

Answer 3

• visual
• somatosensory
• vestibular info
• motor processing

Question 4

In the absence of vision, reaching depends on this to locate objects

Answer 4

• somatosensation

- proprioception

Question 5

What disrupts positioning of limbs in individuals with complete deafferentation?

Answer 5

Loss of somatosensation

Question 6

What does neural activity begin with?

Answer 6

with a decision made in the anterior part of the frontal lobe

Question 7

follow the path of neural activity

Answer 7

• frontal lobe
• motor planning areas activated
• control circuits activated (in UMN tracts)
• UMN tracts deliver signals to interneurons and LMNs
• LMNs transmit signals to skeletal muscles

Question 8

What are control circuits?

Answer 8

consist of cerebellum and basal ganglia

Question 9

What do control circuits do?

Answer 9

• regulate activity in UMN tracts

- activation results in excitation or inhibition of motor neurons

Question 10

UMN tracts deliver signals to

Answer 10

• interneurons

- LMNs

Question 11

classification of UMN tracts

Answer 11

• postural/gross movement tracts
• fine movement tracts
• nonspecific UMNs

Question 12

postural/gross movement tracts control:

Answer 12

automatic skeletal muscle activity

Question 13

fine movement tracts control:

Answer 13

fractionated movements of limbs and face

Question 14

nonspecific UMNs control:

Answer 14

all motor neurons

Question 15

What do LMNs do?

Answer 15

• transmit signals directly to skeletal muscles

- elicit contraction of muscle fibers that move the upper limbs and fingers

Question 16

How is voluntary movement controlled?

Answer 16

top down

• brain
• spinal cord
• muscle

Question 17

properties of skeletal muscle

Answer 17

• excitable
• contractile
• extensile
• elastic

Question 18

t-tubules

Answer 18

• transverse tubules

- projections of muscle cell membranes that extend into the muscle

Question 19

sarcoplasmic reticulum

Answer 19

series of storage sacs for Ca2+ ions

Question 20

myofibrils

Answer 20

individual muscle fibers

Question 21

sarcomeres

Answer 21

arrangement of proteins in a myofibril

Question 22

two protein types in sarcomeres

Answer 22

• structural

- contractile

Question 23

structural proteins of sarcomeres

Answer 23

• Z line
• M line
• titin

Question 24

M line

Answer 24

anchors fibers in center of sarcomere

Question 25

titin

Answer 25

- connects Z line with m line - maintains position of myosin relative to actin - prevents sarcomere from being pulled apart

Question 26

contractile proteins of sarcomeres

Answer 26

- myosin - actin - tropomyosin - troponin

Question 27

contraction

Answer 27

- Produced when active slides relative to myosin | - Repeated attachment, swiveling, and detachment of myosin heads produce contraction of the muscle

Question 28

What do muscles behave like?

Answer 28

springs

Question 29

______ springs generate more resistance to stretch than the same spring when it is _______

Answer 29

- stretched | - shortened

Question 30

What determines total resistance to muscle stretch?

Answer 30

- active contraction - titin - weak actin-myosin bonds

Question 31

muscle tone

Answer 31

resistance to stretch in a resting muscle

Question 32

How is muscle tone assessed?

Answer 32

assessed clinically using PROM

Question 33

When tone is normal, resistance to passive stretch is

Answer 33

minimal

Question 34

Normal resting muscle tone provided by

Answer 34

- titin | - weak actin-myosin bonds

Question 35

weak actin-myosin bonds

Answer 35

- attached, but myosin heads don't swivel | - no muscle contraction, but there is resistance

Question 36

What happens to actin-myosin bonds if muscle is immobile for a prolonged period?

Answer 36

- bonds continually form | - broken by stretching the muscle

Question 37

stretch velocity and actin-myosin bonds

Answer 37

The faster the stretch, the greater the resistance

Question 38

What happens when healthy innervated muscle is continuously immobilized in a shortened position for a prolonged period?

Answer 38

sarcomeres disappear from the ends of myofibrils

Question 39

Why do sarcomeres get lost when immobilized in a shortened position?

Answer 39

Loss of sarcomeres is a structural adaptation to the shortened position so the muscle generates optimal force at the new resting length

Question 40

What happens when a structurally shortened muscle is stretched?

Answer 40

it quickly reaches the limits of its elasticity and is resistant to stretching

Question 41

What happens if a muscle is immobilized in a lengthened position?

Answer 41

the muscle adds new sarcomeres

Question 42

cocontraction

Answer 42

simultaneous contraction of antagonist muscles

Question 43

What does cocontraction do?

Answer 43

- stabilizes joints - UE: enables precise movements - LE: allows individual to stand on an unstable surface