7 Spinal reflexes

7 Spinal reflexes - SPINAL REFLEX page 1 INTRODUCTION TO...

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SPINAL REFLEX AC Brown page 1 A7a INTRODUCTION TO REFLEXES A. Characteristics 1. simple, stereotyped motor responses to sensory stimuli 2. generally involuntary, but sometimes can be influenced by voluntary input 3. do not require conscious perception B. Anatomical Elements 1. sensory endings 2. afferent neurons 3. integration center (involves synapses) 4. efferent neurons 5. motor structures C. Physiological Description 1. initiating stimulus 2. motor action 3. role in body function SPINAL REFLEXES A. Anatomical Elements 1. Sensory endings: various, depending upon the reflex 2. Afferent neurons: sensory neurons, cell bodies in the dorsal root ganglia, enter the spinal cord in the dorsal roots 3. Integration center: spinal cord 4. Efferent neurons: motoneurons, cell bodies in the ventral horn of the spinal cord, leave the cord in the ventral roots; generally large, myelinated motor neurons termed alpha motoneurons 5. Motor structures: skeletal muscle, cardiac muscle, smooth muscle, secretory glands
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SPINAL REFLEX AC Brown page 2 A7a SPINAL REFLEXES (continued) Note: Upon spinal cord section, these are the only motor responses remaining below level of spinal cord transection (but note cerebral dominance in humans, encephalization , and spinal shock -- temporary depression of spinal reflexes following section) Note: There are similar reflexes in the head region, except that (1) the afferent neurons are in certain cranial nerves and their cell bodies are in cranial nerve ganglia; (2) efferent motor neuron axons travel in certain cranial nerves and their cell bodies are in the brain; and (3) the integration centers are in the brain stem (medulla, pons,
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7 Spinal reflexes - SPINAL REFLEX page 1 INTRODUCTION TO...

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