17Su11Lec3 - CS17 Neurobiology of Cognition Spring 2011...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
CS17 Neurobiology of Cognition Spring 2011 Lecture 3: Control of Movement Muscles Three types Smooth (internal organs), Cardiac (heart, endogenous activity) and Striate (Skeletal, Facial) Striate : Band of parallel fibers, each fiber made of many cells but acts as unit; Attached by tendons to bones; - Come in Antagonistic Pairs : Flexor moves bone toward body, Extensor move same bone from body Neuro-Muscular Junction (primarily involving Striate Muscles); - Motor Neurons (“Alpha Motor Neurons”) exit Ventral Root of Spine >> Striate muscles - Neuron synapses directly onto muscle, releasing Acetylcholine (ACh), always sufficient to trigger response - Usually 1 axon branches to multiple muscle fibers; the fewer fibers per axon the more precise the control - Like in a neuron , Muscle fiber response is all/nothing depolarization => Na+ and then K+ gates open/close - Ca++ enters muscle cells => triggers energy-requiring process that causes muscle contraction (See below) - Afterward, Ca++ is actively pumped out, and a Na+/K+ Pump repolarizes fiber for next contraction Contractile Mechanism - Within each fiber is a string of Sarcomeres (the contractile units) each consisting of…. Myosin = thick protein filament with knobby bead-like clusters (“Cross Bridges”) along it, and Actin = thin protein filament, a coiled double-strand braid, anchored to muscle - Contraction = Myosin Cross Bridges hook into (grab) coiled Actin, bend to tighten coil, release, repeat - So note, the only active muscle response is contraction – all stretch is passive. Reflexes – Most involve Spinal Cord circuits (i.e. without brain participation) Stretch Reflex - Proprioceptors called Spindles in muscle detect passive stretch of muscle (e.g. while walking, lifting, being tapped on knee by a doctor “testing your reflexes”, etc.) - Axon of Spindle to Spinal Cord, excites Motor Neuron back to same muscle, contracts to counter stretch - Note: this is the only “mono-synaptic ” reflex Golgi Reflex - Proprioceptors called Golgi Tendon Organs in tendons detect intensity of muscle contraction - If contraction is too strong (threatens to tear muscle apart) sends signal to Interneurons in Spinal Cord that inhibit the Motor Neurons causing that contraction, lessening their rate of firing
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 2

17Su11Lec3 - CS17 Neurobiology of Cognition Spring 2011...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online