Problem 5 Flashcards Preview

Body & Behaviour > Problem 5 > Flashcards

Flashcards in Problem 5 Deck (45)
Loading flashcards...
1

Motor Unit

comprises:

--> motor neuron
--> all of the individual skeletal muscle fibers it innervates

- differ in number of muscle fibers
--> units with fewer fibers have a higher degree of selective motor control (ex. fingers, face)

2

Muscle contraction
(Process)

1. Motor neuron fires

2. ACh is released at neuromuscular junctions

3. ACh activates motor-end-plate on each muscle fiber

4. Contraction of the fibers

3

Fast muscle fiber

contracts + relaxes quickly

--> fatigue quickly because poorly vascularized (few blood vessels - pale)

4

Slow muscle fiber

slower + weaker

--> contraction is more sustained because richly vascularized

5

Flexor

acts to bend or flex a joint

6

Extensor

act to straighten or extend a joint

7

Synergistic Muscles

two muscles whose contraction produces the same movement

8

Antagonistic Muscles

two muscles whose contraction produces opposite movements

ex.: biceps, triceps

9

Isometric Contraction

Contraction of a muscle without movement

--> no change in the length of the muscle

ex.: plank, wall sit (no movement)

10

Dynamic Contraction

Contraction of a muscle resulting in movement

--> change in the length of the muscle

ex.: squats, tricep dips (movement)

11

Principles of the sensorimotor system

3. hierarchally organized
--> the higher the levels of the hierarchy the more complex functions they perform

2. functionally segregated
--> each level is composed of different units each of which perform different functions

3. Information flows down ( Somatosensory S - up )

12

Structure of the Sensorimotor System

1. Association Cortex
- Posterior parietal association cortex
- Dorsolateral prefrontal association cortex

2. Secondary motor cortex

3. Primary motor cortex

4. Brain stem motor nuclei

5. Spinal motor circuits

13

Information transmission in Sensorimotor System

1. Posterior parietal AC supplies Dorsolateral prefrontal AC + Secondary MC with information

2. Dorsolateral prefrontal AC + Secondary MC issue commands based on that information

3. Commands are forwarded to the primary motor cortex

4. Commands are now distributed over four main channels to the spinal sensorimotor circuits

5. Spinal sensorimotor circuits direct the activities of the muscles

14

Role of the Posterior parietal association cortex

integrating the information of

1. the original positions of the parts of the body that are to be moved
2. the positions of any external objects the body is going/might interact with

15

Where does the Posterior parietal AC receive its information from ?

- visual cortex
- auditory cortex
- somatosensory

16

Where does the Posterior parietal AC send its information to ?

Dorsolateral prefrontal cortex and secondary motor cortex

17

Appraxia

disorder of voluntary movement

--> damage to Posterior parietal AC

18

Contralateral Neglect

Disturbance of a patients ability to respond to stimuli on the side opposite to the side of a brain lesion

--> damage to Posterior parietal AC

19

Role of the Dorsolateral prefrontal association cortex

Decision to initiate voluntary movement

20

Role of the Secondary motor cortex

involved in the programming of specific patterns of movement after taking general instructions from the dorsolateral prefrontal AC

--> its neurons become active prior to the initiation of the movement and continue the activity throughout the movement

21

Mirror Neurons

- fire when and individual performs a particular goal directed movement

- or when an individual observes the same goal directed movement performed by others

22

Role of the primary motor cortex

1. Initiating body movements

2. moving body parts independently (ex.: fingers, toes)

Major point of

--> convergence of cortical sensorimotor signals
--> departure of sensorimotor signals from cerebral cortex

23

Somatotopic organization

organization according to the map of the body

ex.: stimulation of the face elicits face movements

24

Astereognosia

Inability to identify objects by touch

--> damage to primary motor cortex

25

Role of the cerebellum

1. motor learning and learning sequences of movements (timing)

2. correcting ongoing movements that deviate from their intended course

26

Role of the Basal Ganglia

habit learning
--> acquired gradually

27

Descending motor pathways

The primary motor cortex sends neural signals via 4 different pathways to the motor neurons of the spinal cord

--> 2 pathways descend into the dorsolateral region of the spinal cord

--> 2 pathways descend into the ventromedial region of the spinal cord

28

Dorsolateral corticospinal tract
(Procedure)

Axons descend directly into the spinal cord

1. Groups of axons descend through medullary pyramids

2. Axons decussate (kreuzen) and continue to descend into the contralateral dorsolateral spinal white matter

=> descend contralateral into distal (far) muscles (e.g.: fingers, toes)

29

Dorsolateral corticorubrospinal tract
(Procedure)

Axons synapse in the brain stem on neurons that in turn descend into the spinal cord

1. Group of axons synapse in the red nucleus of the midbrain

2. Axons decussate and descend trough medulla

3. Some of them terminate in the nuclei of the cranial nerves that control muscles of the face

4. The rest continues to descend into the dorsolateral portion of the spinal cord

=> descend contralateral into distal (far) muscles (e.g.: fingers, toes)

30

Ventromedial Corticospinal tract
(Procedure)

Axons descend directly into the ventromedial areas of the spinal white matter

=> descend ipsilaterally into proximal (near/close) muscles of trunk and limbs