Phyl 1000

Textbook: Neural Reflexes * all neural reflexes begin with stimulus that activates sensory receptor * receptor sends info in form of AP through sensory neurons to CNS * CNS: integrating center that evaluates all incoming info and selects appropriate response * Initiates AP in efferent neurons to direct response of muscles or glands (effectors) * Negative feedback: * Feedback signals from muscle or joint receptors keep CNS continuously informed of changing body position * Feedforward: * Component that allows body to anticipate stimulus and begin response Neural Reflex Pathways Can Be Classified in Different Ways * reflex pathways in NS consist of chains or networks of neurons that link sensory receptors to muscle or glands * classified in several ways: 1. efferent division of NS that controls the response/effector a. somatic motor neurons control skeletal muscles b. autonomic neurons control smooth and cardiac muscles, glands, and adipose tissue 2. CNS location where reflex is integrated (integrating region within CNS) c. Spinal reflexes don’t require input from brain – may be modulated by higher input from brain but integrated in spinal cord d. Cranial reflexes are integrated within brain 3. Whether reflex is innate or learned (time at which reflex develops) e. Innate (inborn) reflexes are genetically determined Ex. Knee jerk rxn f. Learned (conditioned) reflexes are acquired through experience Ex. Pavolv’s dogs 4. Number of neurons in reflex pathway g. Monosynaptic reflexes – have only 2 neurons: one afferent (sensory) and one efferent. Only somatic motor reflexes can be monosynaptic h. Polysynaptic reflexes include 1+ interneurons between afferent and efferent neurons. All autonomic reflexes are polysynaptic because they have 3 neurons: one afferent and 2 efferent * divergence: of pathways allows single