PSY 315 Lecture 11 (2/23/2011) (Motor Control) Dr. Achtman PSY 215. Lecture 11 Topic: Motor System Chapter 8, pages

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1 Corrections: No Corrections Announcements: Exam #2 next Wednesday, March 2, 2011 Monday February 28, 2011 we will be going over the somatosensory system, and there will be time left in class to review so come with questions. Lecture Notes: OUTLINE: Neuromuscular junction Proprioception (somatosensory feedback) Cortical control Other brain areas (cerebellum, basal ganglia) PSY 215 Lecture 11 Topic: Motor System Chapter 8, pages Basic circuitry & disorders (Parkinson s, Huntington s Chorea) WHY DO WE HAVE A NERVOUS SYSTEM? Movement control COMPLEXITY OF MOVEMENT CONTROL: What is difficult about the game of chess? Knowing what to move where (cognitive aspect) Actually moving the pieces, using your motor skills, which for most people is not difficult Written by:{lauren Resetarits}, {lreseta9@mail.naz.edu} Page 1 of 9

2 DEVELOPMENT OF THE NERVOUS SYSTEM: 1. The Neuromuscular junction: Neuron attaching to muscle Motor Unit-the motor neuron plus all the muscle fibers which connect to it The Neuromuscular Neurotransmitter is Acetylcholine (ACh) ACh causes a muscle to contract (showing axon and myelin within the PNS) Myasthenia-gravis- an autoimmune disease which affects ACh receptors. The immune system forms antibodies which attack ACh, therefore loss of voluntary movement occurs. It is extremely debilitating o Treatment: Immuno -suppression, cholinesterase inhibitor, which inhibits the breakdown of ACh Written by:{lauren Resetarits}, {lreseta9@mail.naz.edu} Page 2 of 9

3 2. Proprioception: (somatosensory feedback) Helps stabilize posture Helps avoid damage to muscles The motor neuron activates the muscle (arm with bicep shown.) Muscle Spindle-muscle neuron is all wrapped up and when it is stretched it sends a signal up to the spinal cord, which is then sent to the muscle. Golgi Tendon Organ- when the muscle is stretched so is the tendon. A signal is sent to the muscle to relax! (tendon connects muscle with bone) (Spinal cord is top half of picture, muscle is on the bottom) Stretching the muscle=positive feedback Written by:{lauren Resetarits}, {lreseta9@mail.naz.edu} Page 3 of 9

4 3. Cortical Control: Cortex control voluntary movement Primary Motor Cortex is M1: o M1 is the output, which sends the signal down to the spinal cord a.) Premotor Cortex b.) Supplementary Motor Cortex plan sequence of movement c.) Posterior Parietal and motor control Descending Pathways: Motor sensory Brain muscles A. Dorsolateral Tract: carries information about precise voluntary movement o location where axons are traveling o Signals come from M1 and red nucleus and they stay ipsilateral through the midbrain (as seen in the diagram) o At the medulla they cross over which is contralateral (as seen in the diagram) Written by:{lauren Resetarits}, {lreseta9@mail.naz.edu} Page 4 of 9

5 B. Ventromedial Tract: postural movement, controls both sides of the body o Signal starts in M1 and picks up some signals from the thalamus o Then all signals which are ipsilateral, travel down o SOME cross at the medulla o Information is transferred through the brain and spinal cord Written by:{lauren Resetarits}, {lreseta9@mail.naz.edu} Page 5 of 9

6 4. Cerebellum: Contains more neurons than the rest of the brain combined Effects motor movements, through the motor cortex Key role is to establish new motor programs that enable the execution of actions in sequence Damage to the cerebellum impairs perceptual tasks that depend on accurate timing Cerebellum & basal ganglia communicate with motor neurons through the cortex. Basal Ganglia: Plays an important role in learning motor skills, correcting errors, and postural control Applies to a large group of subcortical structures located in the forebrain which include at least: Structures of the Basal Ganglia Include: o Globus pallidus o Putamen o Cortex (PPC) o Thalamus o Motor Cortex o Motorneurons o Substantia Nigra (S.N.) Written by:{lauren Resetarits}, {lreseta9@mail.naz.edu} Page 6 of 9

7 5. Basic Circuitry and Disorders: Signal goes from the motor cortex to the motorneurons The thalamus gets input from the Globus pallidus For the putamen to be excited it needs the cortex and sbstantia Triggering a Movement: At rest, the only thing activated is the Globus pallidus because there is no inhibition The globus pallidus is inhibiting the thalamus If you want to trigger a movement you need an excitatory signal from the cortex and the substantia nigra to activate the putamen The putamen, itself, is excited and sending its inhibitory signal, inhibiting the G.P. Globus Pallidus stops sending the signal because it is inhibited Therefore, the thalamus is no longer inhibited, and it sends its signal to the motor cortex which then sends the signal to the motorneurons Written by:{lauren Resetarits}, {lreseta9@mail.naz.edu} Page 7 of 9

8 6. Diseases of the Basal Ganglia: Parkinson s Disease- o Disruptions in dopamine o Caused by genetic and environmental factors o Cell damage is often very severe before signs of the disease start showing o *When the Substantia Nigra can no longer activate Putamen o The Putamen must have activity from both the S.N. and the cortex, without there will be no movement o Treatment includes L- dopa, once in the brain, it is converted to dopamine and thus can replace the dopamine lost in Parkinson's disease Written by:{lauren Resetarits}, {lreseta9@mail.naz.edu} Page 8 of 9

9 Huntington s Chorea- o When body movements cannot be controlled o Caused by genetics o Damage to the Globus Pallidus, therefore does not send a signal to the thalamus, which in turn is no longer inhibitory. o The thalamus in response sends an excitatory signal to the motor cortex=chorea o Usually diagnosed late in life, after reproduction has occurred For more information: I simply googled L-Dopa to find out more information on it. youtube video of Michael J. Fox who suffers from Parkinson s disease and how he struggles on a daily basis but has gone from actor to activist to find a cure. Real-life example: Parkinson s disease occurs in about 1 in every 500 people and is on the rise. The chances of someone being related to or knowing an individual with Parkinson s is therefore also on the rise, so with time we should all educate ourselves on the facts of Parkinson s disease. Written by:{lauren Resetarits}, {lreseta9@mail.naz.edu} Page 9 of 9