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Peripheral Nervous System Chapter 14. Spinal Nerves 31 pairs of spinal nerves are connected to the spinal cord – Numbered according to the portion of.

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Presentation on theme: "Peripheral Nervous System Chapter 14. Spinal Nerves 31 pairs of spinal nerves are connected to the spinal cord – Numbered according to the portion of."— Presentation transcript:

1 Peripheral Nervous System Chapter 14

2 Spinal Nerves 31 pairs of spinal nerves are connected to the spinal cord – Numbered according to the portion of the vertebral column at which they exit 8 cervical nerve pairs 12 thoracic nerve pairs 5 lumbar nerve pairs 5 sacral nerve pairs 1 coccygeal nerve pair – All spinal nerves carry both motor and sensory fibers so they are designated as mixed nerves

3 Structure of Spinal Nerves Ventral and dorsal roots join to form spinal nerves Each spinal nerve branches into a dorsal ramus and ventral ramus. (plural = rami)

4 Dermatomes & Myotomes

5 Dermatomes Dermatome: a skin surface area supplied by sensory fibers of a given spinal nerve

6 Myotome Myotome: a skeletal muscle or group of muscles that receives motor axons from a given spinal nerve

7 Cranial Nerves

8 Olfactory Nerve (I) – Sensory – Sense of smell Optic Nerve (II) – Sensory – vision Oculomotor Nerve (III) – Motor – Eye movements, regulation of pupil size Trochlear Nerve (IV) – Motor – Eye movements

9 Cranial Nerves Trigeminal Nerve (V) – Mixed – Sensations of head and face, proprioception – Chewing movements Abducens Nerve (VI) – Motor – Abduction of eye Facial Nerve (VII) – Mixed – Taste – Facial expressions, secretion of saliva & tears Vestibulocochlear Nerve (VIII) – Sensory – Balance, equilibrium, hearing

10 Cranial Nerves Glossopharyngeal Nerve (IX) – Mixed – Sensations of tongue, reflex control of blood pressure & respiration – Swallowing movements, secretion of saliva Vagus Nerve (X) – Mixed – Sensations and movements of organs supplied (ex: slows heart, increases peristalsis, contracts muscles for voice production) Accessory Nerve (XI) – Motor – Shoulder movements, turning head movements, movement of viscera, voice production Hypoglossal Nerve (XII) – Motor – Tongue movements

11 Cranial Nerves Acronyms Names: On Old Olympus’ Tiny Tops, A Friendly Viking Grew Vines And Hops Functional Classification: Some Say ‘Marry Money’; But My Brother Says ‘Bad Business, Marry Money’

12 Reflexes A reflex is the action that results from a nerve impulse passing over a reflex arc – A predictable response to a stimulus – Conscious or unconscious – Somatic Reflexes Skeletal muscle contraction – Autonomic Reflexes Contraction of smooth or cardiac muscle; glandular secretion

13 Somatic Reflexes of Clinical Importance In certain diseases or after trauma to the nervous system certain reflexes may be abnormal Testing of reflexes is a valuable diagnostic tool

14 Stretch Reflexes Knee jerk or patellar reflex – Extension of lower leg in response to tapping patellar tendon – L2-L4 segments of the spinal cord Ankle jerk or Achilles reflex – Plantar flexion of the foot in response to tapping the Achilles tendon – S1-S2 segments of the spinal cord

15 Stretch Reflexes Biceps Reflex – Flexion at the elbow in response to tapping the brachii tendon – C5-C6 segments of the spinal cord Triceps Reflex – Extension at the elbow in response to tapping proximal to the elbow – C6-C7 segments of the spinal cord

16 Cutaneous Reflexes Cutaneous reflexes result from stimulation of the skin receptors Babinski Reflex – Reflex in response to stimulation of the outer portion of the sole of the foot (make a ‘J’ from the heel along the lateral edge through the ball of the foot) – Infant (to 1 ½ yrs): extension and fanning of toes – Children & adults: plantar flexion – Change in response due to corticospinal tract becoming fully myelinated – A + babinski’s in an adult means destruction to the corticospinal tract

17 Cutaneous Reflexes Abdominal Reflex – Drawing in of the abdominal wall in response to stroking the side of the abdomen – T9-T12 spinal nerves and segments of the spinal cord


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