EXAM 2: Motor System 1 Flashcards Preview

7303 Neuroanatomy > EXAM 2: Motor System 1 > Flashcards

Flashcards in EXAM 2: Motor System 1 Deck (43):
1

feedforward

the anticipatory use of sensory information to prepare for movement

2

feedback

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

3

Automatic movements require continuous integration of:

- visual
- somatosensory
- vestibular info
- motor processing

4

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

- somatosensation
- proprioception

5

What disrupts positioning of limbs in individuals with complete deafferentation?

Loss of somatosensation

6

What does neural activity begin with?

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

7

follow the path of neural activity

- 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

8

What are control circuits?

consist of cerebellum and basal ganglia

9

What do control circuits do?

- regulate activity in UMN tracts
- activation results in excitation or inhibition of motor neurons

10

UMN tracts deliver signals to

- interneurons
- LMNs

11

classification of UMN tracts

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

12

postural/gross movement tracts control:

automatic skeletal muscle activity

13

fine movement tracts control:

fractionated movements of limbs and face

14

nonspecific UMNs control:

all motor neurons

15

What do LMNs do?

- transmit signals directly to skeletal muscles
- elicit contraction of muscle fibers that move the upper limbs and fingers

16

How is voluntary movement controlled?

top down
- brain
- spinal cord
- muscle

17

properties of skeletal muscle

- excitable
- contractile
- extensile
- elastic

18

t-tubules

- transverse tubules
- projections of muscle cell membranes that extend into the muscle

19

sarcoplasmic reticulum

series of storage sacs for Ca2+ ions

20

myofibrils

individual muscle fibers

21

sarcomeres

arrangement of proteins in a myofibril

22

two protein types in sarcomeres

- structural
- contractile

23

structural proteins of sarcomeres

- Z line
- M line
- titin

24

M line

anchors fibers in center of sarcomere

25

titin

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

26

contractile proteins of sarcomeres

- myosin
- actin
- tropomyosin
- troponin

27

contraction

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

28

What do muscles behave like?

springs

29

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

- stretched
- shortened

30

What determines total resistance to muscle stretch?

- active contraction
- titin
- weak actin-myosin bonds

31

muscle tone

resistance to stretch in a resting muscle

32

How is muscle tone assessed?

assessed clinically using PROM

33

When tone is normal, resistance to passive stretch is

minimal

34

Normal resting muscle tone provided by

- titin
- weak actin-myosin bonds

35

weak actin-myosin bonds

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

36

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

- bonds continually form
- broken by stretching the muscle

37

stretch velocity and actin-myosin bonds

The faster the stretch, the greater the resistance

38

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

sarcomeres disappear from the ends of myofibrils

39

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

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

40

What happens when a structurally shortened muscle is stretched?

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

41

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

the muscle adds new sarcomeres

42

cocontraction

simultaneous contraction of antagonist muscles

43

What does cocontraction do?

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