Sense receptor stimulation can send signal to spinal cord and then to muscle or gland, resulting in involuntary action {reflex, nerve}|. Stimulus can cause innate, immediate response in muscle or gland. Reflex has only one synapse between muscle or tendon touch receptor and motor neurons to muscle. Brain, body, local excitability, and previous reflex responses can affect reflexes.
types
Stretch reflexes relate to muscle tension, posture, and locomotion. Flexion reflexes follow painful skin stimuli. Reflexes {suprasegmental reflex} can be for one vertebra only {segmental reflex} or for all vertebrae above vertebra. Reflexes {intrasegmental reflex} can involve only one spinal segment. Reflexes {intersegmental reflex} can involve several spinal segments. Reflexes can involve spinal cord, cerebellum, and medulla oblongata. Cerebellum and midbrain automatically control muscle movements {synergy, reflex}. Striatum controls muscles automatically and by association. Neocortex exerts voluntary and regulatory control {state variable}.
Thumb pressed into newborn-foot bottom causes foot and toes to flex {ankle clonus}.
Reflexes {arm reflex} can be in newborns.
Scratching a newborn's foot from toe to heel causes big toe to go up and toes to spread {Babiniski reflex}. In infants, stroking foot side causes big-toe raising. Babiniski reflex disappears at eighteen months old. Adult apes have Babiniski reflex, to grasp tree branches with toes.
Baby reacts to red rattle {Brazelton sensory test}. Baby eyes look ahead during spinning and return to center when spinning stops. Baby can hear bell ring with both ears.
If small object irritates eye, eyelid reflexively closes {blink reflex}.
Reflexes {crossed extension reflex} can be suprasegmental and happen after flexion.
Insects and vertebrates have fast reflexes {escape reflex} to leave situation.
Reflexes {eye reflex} can be in newborns.
Reflexes {eyelid closing reflex} can be in newborns.
Pain causes muscle flexion {flexion reflex}.
Reflexes {inverse stretch reflex} {inverse myotactic reflex} {Golgi tendon reflex} {clasp-knife reflex} can override stretch reflex but is slower because it has two synapses. It works with stretch reflex to maintain posture.
Touching male inner thigh can cause penis erection and testes raising {inner thigh reflex}.
Tapping newborn chin causes masseter muscle to contract {jaw-jerk}.
Avoiding or fleeing is a reflex {large moving object reflex} to large moving objects.
Newborns can react to head-position fast change by extending arms and fingers to side and then in front {Moro reflex}. Moro reflex lasts until six months old.
A one-synapse reflex {stretch reflex} {myotactic reflex} maintains posture and muscle tone. Stretch reflexes relate to muscle tension, posture, and locomotion. Stretch reflexes maintain posture by contracting muscles if they stretch out. Stretch reflex control allows sitting up and other behaviors, after sense organs establish reflexes with motor neurons. Standing, crawling, sitting, walking, and running use spinal-cord reflex circuits, which connect to cerebrum and cerebellum.
Reflexes {necking reflex} can be in newborns.
New stimulus causes attention and turning toward stimulus {orientation reflex} {orienting response}, with increased brain electrical activity, reduced blood flow to extremities, changed skin electrical resistance, increased adrenal steroid hormones, and overt motor activity. Behavior interruption, perception discrepancy, or unexpected stimuli can cause animals to turn toward changes, have more sensitization, and concentrate more. Orienting reflex is automatic and involuntary, not cognitive. It involves acetylcholine neurons. It precedes attention. It processes up to 2000 information bits [Koffka, 1935] [Köhler, 1969] [Palmer, 1999].
ACTH prolongs orientation reflex, and glucocorticoids dull it.
orientation sense
Orienting response precedes slower process {orientation sense} that gathers information about time, place, and person to recognize object. Orientations {shifter circuit, orientation} can be automatic but voluntary and cognitive. Circuits process 50 information bits with each glimpse. Orientation places objects in scenes in short-term memory {pop-out, orientation}, using motion, depth, texture, and color cues.
Eye pupil can open {pupil dilation reflex}|.
Reflexes {pupillary reflex} can be in newborns.
Newborns have reach-and-grasp reflex arm and hand movement {reach-and-grasp reflex}.
Animals can make themselves upright reflexively {righting reflex}.
Touching mouth corner causes newborns to turn and try to suck {rooting response}.
Stimulating a skin point makes same-side leg scratch that point {scratch reflex}. Scratch reflex is suprasegmental.
Jawed vertebrates snap at food {snapping at food reflex}, if small objects move in vision field.
Fear increases startle response {fear-potentiated startle response} {startle response, reflex} {startle reflex}.
Cerebellum and midbrain can coordinate muscle movements {synergy, movement}.
A tendon tap can cause muscle contraction {tendon jerk}. Tendon jerk is simplest and fastest mammalian reflex.
Newborn resists being pulled into sitting position {traction reflex}.
Newborns turn in direction of voices from behind curtains, moving both hands and face {voice reflex}.
After sticking pin into foot sole, newborn foot and leg withdraw {withdrawal reflex}.
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Date Modified: 2022.0225