PSYCH261 Lecture Notes - Lecture 8: Extrafusal Muscle Fiber, Golgi Tendon Organ, Alpha Motor Neuron

87 views7 pages
Control of Movement
Types of Vertebrate Muscles
1. Smooth muscles – control digestive system and other organs
2. Skeletal (Striated) muscles – movement of the body in relation to the environment
3. Cardiac muscles – control the heart
Muscles
-Effectors: e.g., the hands (distal) or neck (proximal)
oEyes – effectors for vision
-Skeletal muscles – attached to bones by tendons
oFlexion: movement of a limb toward the body (contraction of flexors)
oExtension: movement of a limb away from the body (contraction of extensors)
oFlexors and extensors can work in antagonistic ways (one contracts – shortens, the other relaxes –
antagonistic muscles)
Skeletal (striated) Muscles
Motor Unit
-Extrafusal muscle fiber – responsible for force exerted by contraction of
skeletal muscle
-Alpha motor neuron – serves several fibers (from 10 to 100)
Skeletal Muscular Contraction
-Alpha motor neuron originates in the brainstem and spinal cord; exits
via the ventral root
-It synapses with muscle fiber at the motor endplate – the synapse is
the neuromuscular junction
-Terminal button releases ACh  endplate potential (depolarization)
Ca2+ entry  contraction
Skeletal Muscle Contraction
-1 fiber = bundle of myofibrils
-1 myofibril = overlapping strands of actin and myosin filaments (striated muscle)
-sarcomere = contractile unit of striated muscle tissue
-actin attached to myosin cross bridges  rowing movements  contraction
Sensory Feedback Directly from Muscle
-Intrafusal muscle fibers (muscle spindles) – are specialized sensory organs and functions as muscle length
detector
ofibers are stretched when muscle lengthens
osensory ending is stretch receptors
-Gamma motor neuron – allows small contraction of intrafusal fibers to modify sensitivity of fiber’s afferent
ending to stretch
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 7 pages and 3 million more documents.

Already have an account? Log in
Sensory Feedback from Tendons
Golgi Tendon Organ
-Contain stretch receptors
-Sensitive to how hard the muscle is pulling on the bone through the
tendon (muscle tension/stress)
-Degree of stretch coded by firing rate
Monosynaptic Stretch Reflex
-Simplest level of motor integration
-Knee jerk or patellar reflex
-Tapping on patellar tendon stretches quadriceps which contracts,
kicking your foot out
-Time from tap to jerk (~50 msec) is too short to involve the brain
-(Bottom right picture)
-(top left picture)
-weight moves forearm downward  muscle lengthens
-afferent axons of muscle spindle detect muscle lengthening  fire AP to spinal cord
-stimulate alpha motor neuron  muscle contracts
-arm goes back to initial position
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 7 pages and 3 million more documents.

Already have an account? Log in

Get access

Grade+
$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
1 Booster Class
Class+
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
1 Booster Class