Control Of Body Movement Flashcards
Neural Reflex - Efferent Divisions (2)
Somatic or autonomic
Neural Reflexes - CNS Location for Info Processing (2)
Cranial or Spinal
Neural Reflexes - Time at which reflex develops in life (2)
Innate or Learned
Neural Reflexes - Number of neurons in loop (2)
Monosynaptic or polysynaptic
Skeletal Muscle Reflexes - Input
Proprioceptors
- joint movement
- muscle tension & length
Skeletal Muscle Reflexes - CNS Job
To determine if Muscle should contract or relax
Skeletal Muscle - Output
Based on CNS decision
- somatic motor neuron = ONLY contraction
- NO inhibitory neurons that synapse on skeletal Muscle
- can only inhibit contraction at interneurons in IC
Skeletal Muscle Reflex Pathway
Stimulus=Joints, muscle tension, & muscle length
Sensor=Proprioreceptors
Input=Sensory Neuron
IC=CNS (need interneurons to block signal and stop contraction)
Output=Efferent Neurons (somatic motor)
Target=Skeletal Muscle
Response=Cellular (synapses fire on muscle fibers and they contract)
Systemic=muscle contracts
Proprioceptors (3 types)
- The Muscle spindle
- The golgi tendon organ
- Joint receptors
The Muscle spindle
Proprioceptor that detects muscle length
The golgi tendon organ function
Proprioceptor that detects muscle tension
Joint receptors
Proprioceptor that detects changes in the bone position
Stretch Receptors
Signal the brain about muscle length
Intrafusal fibers
Where the Muscle spindle is; gamma motor neurons
Extrafusal Fibers
Normal contractile muscle fibers; alpha motor neurons
Muscle tone
Tonic activity
Alpha-gamma coactivation
Keeps the spindle stretched when the Muscle contracts
The Stretch Reflex
Stimulus=muscle stretches/lengthens
Sensor=Proprioceptors in Muscle spindle
Input=increased afferenr signals to spinal cord through sensory neuron
IC=spinal cord
Output=increased efferent output through alpha motor neurons
Target=muscle fibers
Response=Muscle contracts
Negative feedback pathway=firing rate of afferent sensory neuron decreases
The golgi tendon organ
- The junction of Muscle fibers and tendons
- afferent input from golgi tendon excites inhibitory interneurons (which reduce/end muscle contraction)
Pathway
Stimulus=tension on tendon activates sensory neuron
Sensor=proprioceptors
Input=sensory neuron -> dorsal root ganglia
IC=spinal cord
- sensory neuron stimulates interneuron
- interneuron inhibits motoneuron
*since signal is blocked by inhibitory interneurons, no output, no target, or cell response. STOPS AT IC (negative feedback)
Joint receptors
- found in joint capsules and ligaments around joints
- respond to joint movement velocity, joint position, inflammation, & pain.
- works with vestibular apparatus to help w balance and movement
3 types of movement
- Reflex
- Voluntary
- Rhythmic
Reflex movement
- Least complex; integrated mainly in spinal cord
Ex: knee jerk, cough - Postural Reflexes
Postural Reflexes
Maintain body position as we stand/move; brain stem integration
Voluntary movement
-most complex; integrated in cerebral cortex
Ex: playing piano
Rhythmic movement
- intermediate complexity; integration in spinal cord and cerebral cortex
- Central Pattern Generators (CRG’s)
- > interneurons: take over so you don’t have to think about moving anymoreEx: walking, running
3 factors that influence movement
- the number of spinal cord segments needed
- the use of upper or lower motor neurons
- section of the CNS controlling movement (IC location)
Number of spinal cord segments - segmental
- The Reflex only passes through a small portion of the spinal cord
Ex: quadriceps stretch Reflex “knee jerk Reflex”
Number of spinal cord segments - intersegmental
- the reflex passes through many segments of the spinal cord or brain
Ex: vestibulospinal Reflexes for balance and posture
Segmental “simpler Reflex”
Stimulus=instrument pressure
Sensor=mechanoreceptors
-joint receptors
-golgi tendon organ
-Muscle spindle
Input=sensory neuron
IC=spinal cord
Output=somatic motor neuron (SMN) sends signal to quads
-SMN signal blocked by inhibitory neurons so hamstring relaxes (no signal)
Target=muscle fibers
Response=muscle contraction or relaxation
Flexion Reflexes (crossed extensor Reflex)
Stimulus=stepping on a pin
Sensor=nociceptor
Input=sensory neuron
IC=spinal cord & brain (vestibular balance)
Output= alpha motor neurons
Target=muscle fibers
Response=
-painful leg=extensors inhibited, flexors contract; moving foot away from painful stimulus
-opposite leg=extenders contract as weight shifts to leg, flecked inhibited
Lower Motor Neuron
“Alpha Neuron”
- Cell body in CNS and axon synapses on skeletal Muscle fibers
Upper Motor Neurons
- Lie entirely within CNS (interneurons)
- Control lower motor neurons
(Voluntary and Rhythmic)
White Matter
Myelinated axons
- Bundles of axons knows as tracts
Ascending tract
Carry sensory info to the brain
Ex: dorsal, external lateral
Descending Tract
Carry efferent (motor) signals from brain to spinal cord
Ex: central, interior lateral
Medial Tract
- Controls axial & proximal muscles
• tectospinal tract
• vestibulospinal Tract
• reticulospinal tract
- Originate in brain stemTectospinal Tract
- head orientation to environmental stimuli
Ex: someone slams a door during an exam & everyone looks up
Vestibulospinal Tract
- Muscle control against gravity
Ex: balancing
Reticulospinal Tract
- Controls muscle tone in axial and proximal muscles
Ex: muscle tone; muscle spindle
Lateral Tract
- Controls distal muscles
Ex: rubrospinal tract
Rubrospinal Tract
- Voluntary muscle control
- implicated in control of skilled, repetitive movement
- more developed in humans than animals
Corticospinal Tract
- Controls most skilled voluntary muscle movements
- Connexts motor cortex in parietal lobe of the brain with lower motor neurons
