muscle 1.5

Question 1

motor neuron pool

Answer 1

made up of all the motor neurons that supply a given muscle

-cell bodies of the pool for a given muscle are close together either in the ventral horn of the spinal cord or in the brainstem

Question 2

nervous system and muscle system work together to

Answer 2

initiate and control body movement

Question 3

motor control hierarchy - higher centres ***

Answer 3

higher centres : plan a movement according to intention and communicate it with the middle level via command neurons

structures : areas involved with memory, emotions and motivation

Question 4

motor control hierarchy : local level***

Answer 4

specifies tension of particular muscles and angle of specific joints at specific times necessary to carry out the programs and subprograms transmitted from the middle control levels

includes brainstem or spinal cord interneurons, afferent neurons and motor neurons

only get a descending pathway to the spinal cord from the brainstem and the sensory motor cortex, everything else connected through them

Question 5

voluntary movement

Answer 5

movement accompanied by a conscious awareness of what and why we are doing it AND attention is directed to the action

involuntary: do not have these characteristics

all motor behaviour involves voluntary and involuntary actions

Question 6

local control of motor neurons *

Answer 6

• can adjust motor unit activity if there is an unexpected obstacle
• adjustments are done by using information from AFFERENT fibres of the sensory receptors in the muscles, tendons, joints and skin of the body parts to be moved

Question 7

interneurons

Answer 7

• descending pathways will synapse onto an interneuron then onto motor neuron
• compromise 90% of spinal cord neurons
• two different types local and long interneurons
• important for coordinating movements
• act like a switch that enables movement to be turned on and off under command of higher motor centres

Question 8

local interneurons

Answer 8

near the motor neuron they synapse onto

Question 9

long interneurons

Answer 9

extend up or down short distances in the spinal cord and brainstem

used for integrative complex movements like stepping and throwing a baseball

Question 10

local afferent input what do they do and where do they get information from

Answer 10

they monitor

-length and tension of the muscle

-movement of the joints

-effect of movement on the overlying skin

they carry information from sensory receptors located in

• the skeletal muscles controlled by the motor neurons
• in other muscles, such as those with antagonistic actions
• in the tendons joint and skin of body parts affected by the action of the muscle

Question 11

muscle spindles

Answer 11

-monitor muscle length and rate of change of in muscle length

2 kinds of stretch receptors : nuclear chain fiber and nuclear bag fiber

within the nuclear bag and chain fibre we have a static chain and static bag that do stretch within these

Question 12

nuclear chain fiber (static)

Answer 12

kind of muscle spindle stretch receptor that responds to how much a muscle is stretched

• nuclei arranged in a row
• innervated by group 1a and 2 afferents

Question 13

nuclear bag fibres (static and dynamic)

Answer 13

detect the length and velocity

innervated by group dynamic la afferent

nuclei collected in a bag region

when kyries in his BAG hes more dynamic. 1a, length and velocity

Question 14

muscle spindles - gamma motor coactivation **

Answer 14

• gamma motor neurons have a smaller diameter than alpha neurons
• gammas innervate the endings of intrafusal muscle fibres
• when the ends of the intrafusal muscle fibres contract it will put on the muscle spindle to restore that tension preventing it from going slack during shortening

Question 15

intrafusal muscle fibers

Answer 15

the modified muscle fibres within the spindle, activated by gama motor neurons

Question 16

extrafusal muscle fibres

Answer 16

the skeletal muscle that form the bulk of the muscle and generate its force and movement

Question 17

stretch reflex path A

Answer 17

monosynaptic reflex

• important for maintaining balance and posture
• no interneuron, synapses directly on motor neuron

knee jerk tells us afferent fibres that bring the sensory input to the motor neuron and neuromuscular junctions are functioning normally

Question 18

stretch reflex path B

Answer 18

polysynaptic reflex: have at least 1 interneuron between the afferent and efferent neuron

reciprocal innervation: inhibition of motor neurons activating those muscles whose contraction would oppose an intended movement (antagonistic muscles)

Question 19

Stretch reflex path C

Answer 19

activates motor neurons of synergistic muscles

any muscle whose contraction assists the intended motion

eg. quad extends so rectus femoris, vast lat, vast med, and intermed all fire

Question 20

path D

Answer 20

not part of the stretch reflex

-information will ascend to higher centers

important when movement is unfamiliar higher centre can help control (brain)

Question 21

golgi tendon organs

Answer 21

monitors stretch of muscle tendons

-related to how much tension the contracting motor units are exerting and external forces acting on the muscle

are located in the tendons near junction with the muscle

at rest : no activation

muscle stretch : GT activated from tension exerted on tendon

muscle contract : even more activation of GTO via tendon

Question 22

withdrawal reflex

Answer 22

activates flexor muscles and inhibits extensor muscle of the same leg to move away from painful stimulus

opposite reaction in other leg = crossed extensor reflex