REFLEXES

Reflexes – RAPID, INVLOUNTARY RESPONSES TO CERTAIN STIMULI e.g. pulling your hand off a hot object. Many are there to protect you. Stimulus detected by receptors – impulse sent along sensory neurone to CNS – sent through relay neurone in the CNS which relays it to a motor neurone – to an effector e.g. a muscle contracts.  A REFLEX ARC

SIMPLE REFLEXES INCREASE THE CHANCE OF SURVIVAL – finding food, sheltering from predators, finding a mate. Human simple reflexes include: bright light – pupil gets smaller to avoid damage. Newborn babies will suckle stimulated by touching the lips. 

REFLEXES CAN BE MODIFIED BY THE BRAIN. A response can be overridden by a neurone between the brain and the motor neurone of the reflex arc e.g. not dropping a hot dinner plate. REFLEX RESPONSES CAN BE LEARNED an animal can learn to produce the same response to a different stimulus e.g. Pavlov’s dogs – they drooled when they smelt food and later when they heard the bell.  This is a CONDITIONED REFLEX