motor function/movement relies on the overall plan and constant sensory feedback through the
SENSORIMOTOR SYSTEM. ➞ output - motor cortex (left hemisphere section controls the
body's right side) 》input - sensory cortex (left hemisphere section receives input from the body's
right side) 🟆categories of movement🟆voluntary movements (under volitional control) -
purposeful, goal-directed movements • reflexes (automatic) - involuntary, stereotyped, rapid
movements • rhythmic motor patterns - repeating patterns of movement mediated by central
pattern generators (ex: respiration, walking) 🟆principles of motor function🟆 1. hierarchal
organization - association cortex at the highest level (complex processing), muscles at the
lowest (simple processing) 2. sensory feedback is essential - most motor output is guided by
sensory input 3. the motor system learns (motor learning) - the process by which motor
programs are created and modified; a learned, fixed sequence of movement 🟆muscle🟆skeletal
- approximately 40% of human body weight • cardiac - muscle in the heart; involuntary pumping
of blood • smooth - digestive system; involuntary digestion • sarcopenia - age related muscle
loss • flexors - bend a joint (i.e. biceps) • extensors - straightens a joint (i.e. triceps) 》
antagonistic= when two muscles cause opposite movements (i.e. biceps & triceps) •
synergistic= when two muscles contract and cause the same movement 🟆motor neuron &
motor unit in muscle🟆 motor unit - consists of a single motor neuron and the myofibers
(muscle tissues) muscle fibers it innervates (controls); all fibers in the same motor unit contract
when the motor neuron fires • motor pool - all of the motor units controlling the same muscle •
muscle fiber - there are fast muscle fibers + slow muscle fibers • innervation ratio - number of
muscle fibers per motor unit; determines movement precision 》low ratio/small motor unit =
precise movements • high ratio/large motor unit = coarse, less precise movements》
neuromuscular junction - the connection between the terminal end of a motor neuron and the
motor end-plate of the muscle fiber: action potential in motor neurons releases acetylcholine in
the terminal, causing muscle to contract 🟆proprioception🟆 proprioceptive system -
somatosensory subsystem; monitors information about the position of different parts of the
body; transmitted via specialized sensory receptors (proprioceptors) in muscle… 1. muscle
spindles - embedded in muscle tissue; respond to changes in muscle length • muscle-spindle
feedback circuit - muscle spindle: receptors and it's intrafusal muscle… the intrafusal muscle
is innervated by intrafusal motor neuron > the intratrafusal motor neurons adjust the length of
intrafusal muscle to maintain appropriate degree of muscle tension 2. golgi tendon organs -
embedded in tendons; respond to changes in muscle tension; protect muscle from being over
stretched🟆spinal circuits for reflexes🟆 reflex - a response to a stimulus that does not require
the involvement of consciousness 1. stretch reflex - occurs when the length of a muscle is
suddenly extended: automatically retracts in response to passive stretching (i.e. patellar
tendon/knee jerk reflex) i. monosynaptic reflex (only involves one synapse) ii. afferent neuron
brings sensory signal to spinal cord iii. efferent neuron sends motor command; muscle contracts
2. withdrawal reflex - occurs when you touch something painful; different from stretch reflex in
which the circuit is not monosynaptic; involves interneurons i. reciprocal innervation - some
sensory neurons excite excitatory interneurons, while some excite inhibitory interneurons i.e.
excitatory interneuron - contraction of bicep & i.e. inhibitory interneuron - relaxation of triceps 3.
recurrent collateral inhibition - a negative feedback loop that prevents rapid, repeated firing of
the same motor neuron i. motor neuron branches (collateral axon) onto interneuron (renshaw
SENSORIMOTOR SYSTEM. ➞ output - motor cortex (left hemisphere section controls the
body's right side) 》input - sensory cortex (left hemisphere section receives input from the body's
right side) 🟆categories of movement🟆voluntary movements (under volitional control) -
purposeful, goal-directed movements • reflexes (automatic) - involuntary, stereotyped, rapid
movements • rhythmic motor patterns - repeating patterns of movement mediated by central
pattern generators (ex: respiration, walking) 🟆principles of motor function🟆 1. hierarchal
organization - association cortex at the highest level (complex processing), muscles at the
lowest (simple processing) 2. sensory feedback is essential - most motor output is guided by
sensory input 3. the motor system learns (motor learning) - the process by which motor
programs are created and modified; a learned, fixed sequence of movement 🟆muscle🟆skeletal
- approximately 40% of human body weight • cardiac - muscle in the heart; involuntary pumping
of blood • smooth - digestive system; involuntary digestion • sarcopenia - age related muscle
loss • flexors - bend a joint (i.e. biceps) • extensors - straightens a joint (i.e. triceps) 》
antagonistic= when two muscles cause opposite movements (i.e. biceps & triceps) •
synergistic= when two muscles contract and cause the same movement 🟆motor neuron &
motor unit in muscle🟆 motor unit - consists of a single motor neuron and the myofibers
(muscle tissues) muscle fibers it innervates (controls); all fibers in the same motor unit contract
when the motor neuron fires • motor pool - all of the motor units controlling the same muscle •
muscle fiber - there are fast muscle fibers + slow muscle fibers • innervation ratio - number of
muscle fibers per motor unit; determines movement precision 》low ratio/small motor unit =
precise movements • high ratio/large motor unit = coarse, less precise movements》
neuromuscular junction - the connection between the terminal end of a motor neuron and the
motor end-plate of the muscle fiber: action potential in motor neurons releases acetylcholine in
the terminal, causing muscle to contract 🟆proprioception🟆 proprioceptive system -
somatosensory subsystem; monitors information about the position of different parts of the
body; transmitted via specialized sensory receptors (proprioceptors) in muscle… 1. muscle
spindles - embedded in muscle tissue; respond to changes in muscle length • muscle-spindle
feedback circuit - muscle spindle: receptors and it's intrafusal muscle… the intrafusal muscle
is innervated by intrafusal motor neuron > the intratrafusal motor neurons adjust the length of
intrafusal muscle to maintain appropriate degree of muscle tension 2. golgi tendon organs -
embedded in tendons; respond to changes in muscle tension; protect muscle from being over
stretched🟆spinal circuits for reflexes🟆 reflex - a response to a stimulus that does not require
the involvement of consciousness 1. stretch reflex - occurs when the length of a muscle is
suddenly extended: automatically retracts in response to passive stretching (i.e. patellar
tendon/knee jerk reflex) i. monosynaptic reflex (only involves one synapse) ii. afferent neuron
brings sensory signal to spinal cord iii. efferent neuron sends motor command; muscle contracts
2. withdrawal reflex - occurs when you touch something painful; different from stretch reflex in
which the circuit is not monosynaptic; involves interneurons i. reciprocal innervation - some
sensory neurons excite excitatory interneurons, while some excite inhibitory interneurons i.e.
excitatory interneuron - contraction of bicep & i.e. inhibitory interneuron - relaxation of triceps 3.
recurrent collateral inhibition - a negative feedback loop that prevents rapid, repeated firing of
the same motor neuron i. motor neuron branches (collateral axon) onto interneuron (renshaw
