Ch 13 PNS Reflexes Reflexes Reflexes reflex arc

Ch 13 PNS & Reflexes

Reflexes

Reflexes reflex arc – neural pathways of reflexes § reflex – rapid, predictable, involuntary response to stimuli - somatic reflex i. all reflexes of skeletal muscles i. e. ) patellar reflex - autonomic reflex i. smooth muscle, heart, glands i. e. ) salivary reflex; pupillary reflex; digestion; elimination; blood pressure; sweating

– reflex arc • spinal reflexes have 4 elements/components v so all reflexes have a minimum of four (4) elements since spinal is the simplest of reflexes § two neuron reflex arc (4 components) 1. sensory receptor 2. afferent neuron (sensory) 3. efferent neuron (motor) 4. effector organ § involves one synapse

II. Nervous Tissue: Structure & Function – reflex arc • cranial reflexes have 5 elements/components – three (3) neuron reflex (5 components/elements) same as 2 neuron reflex except: - an interneuron between afferent and efferent neurons (in the brain or spinal cord) - involves 2 synapses - more synapses, more delay – longer for the reflex to happen - Involves brain to evaluate & make right decision – but still very fast reflex

• some reflexes involve only spinal cord neurons – without brain involvement • others involve the brain – to evaluate and make “right” adjustments

Ch. 13: PNS & Nerves Spinal Nerves • define/notate info. on the following terms related to spinal nerves 1. 2. 3. 4. 5. 6. mixed nerve – plexus – lumbar plexus – sacral plexus – brachial plexus – intercostal nerves –