Neurophys 8 Flashcards
Components of reflex
Sensory receptor
Sensory neuron
Synapse in CNS
Motor neuron
Effector organ
Types of reflex
Monosynaptic - sensory neuron directly synapses w motor neurons
Polysynaptic - one or more Interneurons between sensory and motor neurons
Types of reflexes
Segmental
Intersegmental
Suprasegmental
Segmental arc length
One or a few spinal cord segments
Intersegmental arc lengths
Multiple spinal cord segments
Suprasegmental arc length
Arc involves synapses in the brain
Myotatic reflex
“Stretch reflex”
Muscle stretches to induce muscle contraction & relaxation of contra lateral muscle
Muscle spindle
Sensory organ
Short intramural muscle fibers
Muscle spindle Innervation - sensory
Type 1a - info abt muscle length & velocity of cont
Type 2 - info about muscle length
Muscle spindle Innervation - motor
Gamma motor neurons
Muscle spindle contraction
Extrafusal fibers contract - intrafusal fibers contract
Innervated by gamma motor neurons
Golgi tendon organs location & arrangment
Located in tendons
Innervated by type 1b sensory fibers
Arranged in series w extrafusal muscle fibers
Golgi tendon organs - info
Provide info on degree of muscle contraction
Prevents damage from excessive muscle contraction
Golgi tendon organ - Interneurons
Sensory info carried by group 1b afferent
- inhibits agonist alpha motor neurons (relax)
- excite antagonist alpha motor neurons (contract)
“Inverse myotatic reflex”
Withdrawal reflex function
Polysynaptic
Sensory receptor = nociceptor (pain)
withdrawal reflex action
Flexion of ipsilateral limb
Extension of contra lateral limb (stabilize the body)
Cutaneous trunci reflex - muscle
Sheet of subQ muscle located in thorax
Functions to twitch off insects
Innervated by lateral thoracic nerve (C8-T1)
Contains no muscle spindles
Cutaneous trunci reflex
Stimulation of lateral skin causes skin twitch
Used to localize spinal cord lesions
Myotatic reflex specifics
Sensory organ = muscle spindle
Monosynaptic
Segmental
Occurs in all skeletal muscle (quads, patellar reflex)
Arrangment of muscle spindle
Surrounded by fibrous capsule
Arranged in parallel to extrafusal fibers
Maintains postures
Lesions & reflexes - upper MN
brain, cranial spinal cord
- normal to increased reflexes (hyperreflexia)
- normal to increased muscle tone (spastic paralysis)
Lesions & reflexes - lower motor neuron
Spinal cord, grey matter, nerve
- decreased reflexes (hyporeflexia)
- decreased muscle tone (flaccid paralysis)
Diving reflex involvement
Polysynaptic
Sense organ - touch and thermoreceptors
Afferent nerve - trigeminal (V)
Synapses - brainstem nuclei, including vagus
diving reflex output
Parasympathetic (vagus) to heart
Inhibits respiration and causes bronchoconstriction
