2 Figure 10-1 Motor commands from the brain have been modified by a variety ofexcitatory andinhibitory controlsystems, includingessential feedbackfrom sensoryafferent neurons,along with visionand balance cues(not shown).
3 Figure 10-2 Side and cross-sectional views of some of the neural components regulating motor commands.Altered processing abilities in these componentscan cause motor problems such as Parkinsonism.
5 Figure 10-3 Examples of the categories of information and their underlying neuronal substrates modifying theproduction of motor commands from the brain.
6 Figure 10-4 Acting on local reflex circuits and by relaying impulses to the brain,muscle spindles andGolgi tendon organsprovide informationabout muscle positionand stretch in orderto finely regulate thespeed and intensityof muscle contraction.
7 Regardless of the reason for a change in length, the stretched spindle in scenario (a) generates a burst of action potentials as the muscle is lengthened; in scenario (b), the shortened spindle produces fewer action potentials from the spindle.
8 Figure 10-6Tapping the patellar tendon lengthens the stretch receptor in the associated extensor muscle in the thigh; responses include:compensatory contractionin that muscle (A and C),relaxation in the opposing flexor (B), and sensory afferent delivery to the brain.Note: NMJ = neuromuscular junction
9 Activation of Golgi tendon organs Activation of Golgi tendon organs. Compared to when a muscle is contracting, passive stretch of the relaxed muscle produces less stretch of the tendon and fewer action potentials from the Golgi tendon organ.
10 Figure 10-8Contraction of the extensor muscle on the thigh tenses the Golgi tendon organ and activates it to fire action potentials. Responses include:Inhibition of the motorneurons that innervate thismuscle (A), and excitationin the opposing flexor’s motor neurons (B).Note: NMJ = neuromuscular junction
11 1 2 3 Figure 10-9 Pain sensory afferents detect pain in foot and The neural components of the pain-withdrawal reflex in this example proceed as follows:Pain sensory afferentsdetect pain in foot andsend action potentials viadorsal horn of spinal cord.Interneurons in the cordactivate extensor muscleson the “pained” side ofthe body and flexormuscles on the oppositeside of the body.Muscles move body awayfrom painful stimulus.12Could alter to show 1, 2, 3 in sequence3Figure 10-9
12 Figure 10-10 Extensive neural networks between the major “motor areas” of the cerebral cortex permitfine control of movement, utilizing sensory andintentional signals to activate the appropriatemotor neurons at an appropriate level of stimulation.Figure 10-10
13 The location and relative size of the cartoon body- Somatotopic MapThe location and relative size of the cartoon body-shapes represent the location and relative numberof motor-related neurons in the cerebral cortex.
14 Figure 10-12 Efferent motor commands from the cerebral cortex are contralateral or “crossed,” meaning that theleft cortex controlsthe muscles onthe right side ofthe body (andvice versa),whereas thebrainsteminfluencesipsilateral(same side)motor activity.Figure 10-12
15 Figure 10-13 Motor activity must be informed about the body’s center of gravity in order to make adjustmentsin the level of stimulation to muscles whosecontraction prevents unstable conditions (falling).