Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
I. Anatomy II. Physiology Spinal Cord 1 The Spinal Cord & Spinal Nerves Together with brain forms the CNS Functions 1. spinal cord reflexes 2. integration (summation of inhibitory and excitatory) nerve impulses 3. highway for upward and downward travel of sensory and motor information 2 I. II. Anatomy 1. Protective Structures 2. External 3. Internal 4. Spinal Nerves a. Covering b. Distribution c. Dermatomes Physiology Spinal Cord 3 Spinal Cord Protection 1. vertebral column 4 Structures Covering the Spinal Cord 2. Membrane A. Dura mater - dense irregular CT tube Subdural space filled with interstitial fluid B. Arachnoid = spider web of collagen fibers A. Subarachnoid space = CSF C. Pia mater thin layer covers BV denticulate ligs hold in place 5 External Anatomy of Spinal Cord Flattened cylinder 16-18 Inches long & 3/4 inch diameter In adult ends at L2 In newborn ends at L4 Growth of cord stops at age 5 1. Cervical enlargement 2. upper limbs Lumbar enlargement lower limbs 6 Inferior End of Spinal Cord 1. Conus medullaris 2. 3. Filum terminale thread-like extension of pia mater stabilizes spinal cord in canal Caudae equinae (horse’s tail) 4. cone-shaped end of spinal cord Conus medullaris dorsal & ventral roots of lowest spinal nerves Spinal segment area of cord from which each pair of spinal nerves arises Filum terminale 7 Spinal Cord & Spinal Nerves Spinal nerves begin as roots Posterior Root (Sensory) 1. Dorsal or posterior root is incoming sensory fibers dorsal root ganglion (swelling) = cell bodies of sensory nerves 2. Ventral or anterior root is outgoing motor fibers Anterior Root (Motor) 8 Gray Matter of the Spinal Cord Central canal continuous with 4th ventricle of brain Gray matter is shaped like the letter H or a butterfly contains neuron cell bodies, unmyelinated axons & dendrites paired dorsal and ventral gray horns lateral horns only present in thoracic spinal cord gray commissure crosses the midline 10 White Matter of the Spinal Cord White matter covers gray matter Anterior median fissure deeper than Posterior median sulcus Anterior, Lateral and Posterior White Columns contain axons that form ascending & descending tracts 11 Spinal Nerves 31 Pairs of spinal nerves Named & numbered by the cord level of their origin 1. 8 pairs of cervical nerves (C1 to C8) 2. 12 pairs of thoracic nerves (T1 to T12) 3. 5 pairs of lumbar nerves (L1 to L5) 4. 5 pairs of sacral nerves (S1 to S5) 5. 1 pair of coccygeal nerves Mixed sensory & motor nerves 12 A Nerve Plexus Joining of ventral rami of spinal nerves to form nerve networks or plexuses Found in neck, arm, low back & sacral regions No plexus in thoracic region intercostal nn. innervate intercostal spaces T7 to T12 supply abdominal wall as well 16 Cervical Plexus Ventral rami of spinal nerves (C1 to C5) Supplies parts of head, neck & shoulders Phrenic nerve (C3-C5) keeps diaphragm alive Damage to cord above C3 causes respiratory arrest 17 Phrenic Nerve 18 Brachial Plexus Ventral rami from C5 to T1 Supplies shoulder & upper limb Passes superior to 1st rib & under clavicle Axillary n. = deltoid & teres m. Musculocutaneous n. = elbow flexors Radial n. = shoulder & elbow extensors Median & ulnar nn. = flexors of wrist & hand 19 Branches off Brachial Plexus 20 Lumbar Plexus Ventral rami of L1 to L4 Supplies abdominal wall, external genitals & anterior/medial thigh Injury to femoral nerve causes inability to extend leg & loss of sensation in thigh Injury to obturator nerve causes paralysis of thigh adductors 22 Branches of Lumbar Plexus Notice: Femoral and Obturator nerves Found anterior and medial to hip joint 23 Sacral Plexus Ventral rami of L4-L5 & S1-S4 Anterior to the sacrum Supplies buttocks, perineum & part of lower limb Sciatic nerve = L4 to S3 supplies post thigh & all below knee Peroneal nerve injury produces foot drop or numbness Tibial nerve injury produces calcaneovalgus (loss of function on anterior leg & dorsum of foot) 24 Branches of Sacral Plexus 25 Sciatic Nerve Branches Notice: Common Peroneal nerve and Tibial nerve behind the knee Notice: Sciatica pain extends from the buttock down the leg to the foot may be sign of herniated disc 26 Dermatomes & Myotomes Each spinal nerve contains both sensory & motor nerve fibers Dermatome area of skin supplied by one spinal nerve overlap prevents loss of sensation if one damaged sensory anesthesia requires 3 spinal nerves to be blocked Skin on face supplied by Cranial Nerve V 27 I. Anatomy II. Physiology 1. Tracts 2. Reflexes a. Stretch b. Tendon c. Flexor d. Crossed Extensor Spinal Cord 29 Tracts of the Spinal Cord Function of tracts 1. highway for sensory & motor information 2. sensory tracts ascend 3. motor tracts descend Naming of tracts indicates position & direction of signal example = anterior spinothalamic tract impulses travel from spinal cord towards brain (thalamus) found in anterior part of spinal cord 30 Location of Tracts inside Cord Motor tracts Sensory tracts pyramidal tract (corticospinal) spinothalamic tract extrapyramidal tract posterior column spinocerebellar 31 Function of Spinal Tracts two-point discrimination, pressure and vibration pain, temperature, deep pressure 32 Function of Spinal Tracts voluntary movements, posture & muscle tone, equilibrium 33 Spinal Reflexes Automatic response to change in environment Integration center for spinal reflexes is gray matter of spinal cord Examples somatic reflexes result in skeletal muscle contraction autonomic (visceral) reflexes involve smooth & cardiac muscle and glands. heart rate, respiration, digestion, urination, etc Note: cranial reflexes involve cranial nerves 34 Reflex Arc Specific nerve impulse pathway 5 components of reflex arc 1. receptor 2. sensory neuron 3. integrating center 4. motor neuron 5. effector 4 important somatic spinal reflexes 1. stretch, 2. tendon, 3. flexor(withdrawal) 4. crossed extensor reflexes 35 Illustration of the Stretch Reflex 37 Illustration of Tendon Reflex 40 Flexor (withdrawal) Reflex Step on tack (pain fibers send signal to spinal cord) Interneurons branch to different spinal cord segments Motor fibers in several segments are activated More than one muscle group activated to lift foot off of tack 41 Crossed Extensor Reflex Lifting left foot requires extension of right leg to maintain one’s balance Pain signals cross to opposite spinal cord Contralateral extensor muscles are stimulated by interneurons to hold up the body weight Reciprocal innervation when extensors contract flexors relax, etc 42