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1.  Protective structures: Vertebral column and the meninges provide protect the spinal cord and provide physical stability. a. Dura mater, b. Arachnoid,

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Presentation on theme: "1.  Protective structures: Vertebral column and the meninges provide protect the spinal cord and provide physical stability. a. Dura mater, b. Arachnoid,"— Presentation transcript:

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2  Protective structures: Vertebral column and the meninges provide protect the spinal cord and provide physical stability. a. Dura mater, b. Arachnoid, c. Pia mater  Epidural space, subdural space and subarachnoid space 2

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4  Two enlargements: cervical and lumbar  Conus medullaris  Filum terminale  Cauda equina  Posterior (dorsal root) & anterior(ventral) root  Posterior (dorsal root) ganglion  Spinal nerve 4

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6  Anterior median fissure  Posterior median sulcus  Gray and white commissures  Central canal  Anterior, posterior & lateral gray horns  Anterior, posterior & lateral white columns 6

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8  31 pairs; mixed nerves.  Cervical (C1-C8), thoracic (T1-T12), lumbar (L1-L5), sacral (S1-S5) and coccygeal. Connective tissue coverings of spinal nerves:  Epineurium, perineurium and endoneurium:  Fascicles 8

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10  Spinal nerves branch and their braches are called rami: Posterior (dorsal) ramus Anterior (ventral) ramus  Plexuses: a network of axons Anterior rami except T1-T11 form plexuses. 10

11  Formed by the anterior rami of C1-C5.  Phrenic nerves- important nerves from the cervical plexuses. Formed by the anterior rami of C1-C5. Phrenic nerves- important nerves from the cervical plexuses. 11

12  Formed by the anterior rami of C5-C8 & T1.  Supplies the shoulders and upper limbs.  Roots → trunks → divisions → cords → nerves. 12

13 Important nerves that arise from the brachial plexuses are  Axillary nerve  Musculocutaneous nerve  Radial nerve  Median nerve  Ulnar nerve 13

14  Erb-Duchenne palsy (waiter’s tip)- loss of sensation along the lateral side of the arm.  Wrist drop- inability to extend the wrist and fingers. 14

15  Median nerve palsy- numbness, tingling and pain in the palm and fingers.  Ulnar nerve palsy- inability to abduct or adduct fingers  Winged scapula- the arm cannot be abducted beyond the horizontal position. 15

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17  Formed by the anterior rami of L1-L4.  Supplies the anterolateral abdominal wall, external genitals, and part of the lower limbs.  Femoral nerves, obturator nerves. 17

18  Formed by the anterior rami of L4-L5 and S1-S4.  Supplies the buttocks, perineum, and lower limbs.  Gives rise to the largest nerve in the body- the sciatic nerve. 18

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20  Formed by the anterior rami of S4-S5 and the coccygeal nerves.  Supplies a small area of skin in the coccygeal region. 20

21  Dermatome is the area of the skin that provides sensory input to the CNS via one pair of spinal nerves or the trigeminal nerve. 21

22  The name of the tract often indicates its location in the white matter and where it begins and ends.  The white matter contains both sensory and motor tracts. 22

23  A reflex is an automatic, sudden, involuntary response to a stimulus.  When the integration takes place in the spinal cord, the reflex is a spinal reflex. 23

24  The pathway followed by nerve impulses that produce a reflex is a reflex arc.  A reflex arc includes: a. sensory receptor b. sensory neuron c. integrating center d. motor neuron e. effector 24

25 1 SENSORY RECEPTOR (responds to a stimulus by producing a generator or receptor potential) 1 SENSORY NEURON (axon conducts impulses from receptor to integrating center) SENSORY RECEPTOR (responds to a stimulus by producing a generator or receptor potential) 2 1 SENSORY NEURON (axon conducts impulses from receptor to integrating center) SENSORY RECEPTOR (responds to a stimulus by producing a generator or receptor potential) INTEGRATING CENTER (one or more regions within the CNS that relay impulses from sensory to motor neurons) Interneuron SENSORY NEURON (axon conducts impulses from receptor to integrating center) SENSORY RECEPTOR (responds to a stimulus by producing a generator or receptor potential) INTEGRATING CENTER (one or more regions within the CNS that relay impulses from sensory to motor neurons) MOTOR NEURON (axon conducts impulses from integrating center to effector) Interneuron SENSORY NEURON (axon conducts impulses from receptor to integrating center) SENSORY RECEPTOR (responds to a stimulus by producing a generator or receptor potential) INTEGRATING CENTER (one or more regions within the CNS that relay impulses from sensory to motor neurons) MOTOR NEURON (axon conducts impulses from integrating center to effector) EFFECTOR (muscle or gland that responds to motor nerve impulses) Interneuron

26  Causes contraction of a skeletal muscle in response to stretching of the muscle.  Monosynaptic reflex.  Patellar or knee-jerk reflex: Stretching of a muscle →activation of muscle spindles →sensory neuron →spinal cord→motor neuron → muscle contraction.  Ipsilateral. 26

27 1 Stretching stimulates SENSORY RECEPTOR (muscle spindle) Antagonistic muscles relax 1 Stretching stimulates SENSORY RECEPTOR (muscle spindle) SENSORY NEURON excited To brain Spinal Nerve Stretching stimulates SENSORY RECEPTOR (muscle spindle) SENSORY NEURON excited MOTOR NEURON excited EFFECTOR (same muscle) contracts and relieves the stretching Antagonistic muscles relax Motor neuron to antagonistic muscles is inhibited Within INTEGRATING CENTER (spinal cord), sensory neuron activates motor neuron Inhibitory interneuron To brain Spinal Nerve + –

28  Polysynaptic reflex.  Control muscle tension by causing muscle relaxation when muscle tension is great.  Sensory receptors- Golgi tendon organs.  ↑ Tension applied to the tendon → tendon organ stimulation → nerve impulse → spinal cord →motor neuron causes muscle relaxation and relieves tension. 28

29 1 Increased tension stimulates SENSORY RECEPTOR (tendon) 1 Spinal nerve SENSORY NEURON excited To brain Increased tension stimulates SENSORY RECEPTOR (tendon) Within INTEGRATING CENTER (spinal cord), sensory neuron activates inhibitory interneuron Excitatory interneuron Spinal nerve Inhibitory interneuron SENSORY NEURON excited + To brain Increased tension stimulates SENSORY RECEPTOR (tendon) – + 1 – Within INTEGRATING CENTER (spinal cord), sensory neuron activates inhibitory interneuron Excitatory interneuron Antagonistic muscles contract Spinal nerve MOTOR NEURON inhibited Inhibitory interneuron SENSORY NEURON excited + To brain Increased tension stimulates SENSORY RECEPTOR (tendon) Motor neuron to antagonistic muscles is excited – EFFECTOR (muscle attached to same tendon) relaxes and relieves excess tension Within INTEGRATING CENTER (spinal cord), sensory neuron activates inhibitory interneuron Excitatory interneuron Antagonistic muscles contract Spinal nerve MOTOR NEURON inhibited Inhibitory interneuron SENSORY NEURON excited + To brain Increased tension stimulates SENSORY RECEPTOR (tendon) Motor neuron to antagonistic muscles is excited

30  Polysynaptic reflex  Ipsilateral.  Stepping on a tack (stimulus) → nerve impulse → activation of the interneuron → activation of the motor neuron →muscle contraction →withdrawal of the leg. 30

31 1 Stepping on tack stimulates SENSORY RECEPTOR (dendrites of pain-sensitive neuron) 1 + Stepping on tack stimulates SENSORY RECEPTOR (dendrites of pain-sensitive neuron) SENSORY NEURON excited Stepping on tack stimulates SENSORY RECEPTOR (dendrites of pain-sensitive neuron) SENSORY NEURON excited Within INTEGRATING CENTER (spinal cord), sensory neuron activates interneurons in several spinal cord segments Ascending interneuron Interneuron Descending interneuron Spinal nerve Stepping on tack stimulates SENSORY RECEPTOR (dendrites of pain-sensitive neuron) SENSORY NEURON excited MOTOR NEURONS excited MOTOR NEURON excited Within INTEGRATING CENTER (spinal cord), sensory neuron activates interneurons in several spinal cord segments Ascending interneuron Interneuron Descending interneuron Spinal nerve Stepping on tack stimulates SENSORY RECEPTOR (dendrites of pain-sensitive neuron) SENSORY NEURON excited MOTOR NEURONS excited MOTOR NEURON excited EFFECTORS (flexor muscles) contract and withdraw leg Within INTEGRATING CENTER (spinal cord), sensory neuron activates interneurons in several spinal cord segments Ascending interneuron Interneuron Descending interneuron Spinal nerve

32  Polysynaptic reflex.  Contralateral reflex.  Contraction of muscles that extend joints in the opposite limb in response to a painful stimulus.  Stepping on a tack (stimulus) → nerve impulse →activation of several interneurons → activation of the motor neurons → muscle contraction causing flexion of the leg stepping on a tack & extension on the opposite side. 32

33 1 Withdrawal of right leg (flexor reflex) Stepping on a tack stimulates SENSORY RECEPTOR (dendrites of pain-sensitive neuron) in right foot 1 SENSORY NEURON excited Withdrawal of right leg (flexor reflex) Stepping on a tack stimulates SENSORY RECEPTOR (dendrites of pain-sensitive neuron) in right foot Ascending interneurons SENSORY NEURON excited Spinal nerve Within INTEGRATING CENTER (spinal cord), sensory neuron activates several interneurons Descending interneurons Withdrawal of right leg (flexor reflex) Stepping on a tack stimulates SENSORY RECEPTOR (dendrites of pain-sensitive neuron) in right foot Interneurons from other side 1 + Ascending interneurons SENSORY NEURON excited Spinal nerve Within INTEGRATING CENTER (spinal cord), sensory neuron activates several interneurons MOTOR NEURONS excited Descending interneurons Withdrawal of right leg (flexor reflex) Stepping on a tack stimulates SENSORY RECEPTOR (dendrites of pain-sensitive neuron) in right foot Extension of left leg (crossed extensor reflex) MOTOR NEURONS excited Interneurons from other side 1 + Ascending interneurons EFFECTORS (extensor muscles) contract, and extend left leg SENSORY NEURON excited Spinal nerve Within INTEGRATING CENTER (spinal cord), sensory neuron activates several interneurons MOTOR NEURONS excited Descending interneurons Withdrawal of right leg (flexor reflex) Flexor muscles contract and with- drawright leg Stepping on a tack stimulates SENSORY RECEPTOR (dendrites of pain-sensitive neuron) in right foot Extension of left leg (crossed extensor reflex) MOTOR NEURONS excited Interneurons from other side

34 34 Portions of the above presentation are copy-writed by John Wiley & Sons, Inc. For those portions, all rights are reserved. Reproduction or translation of those portions beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein. Copyright 2009 John Wiley & Sons, Inc.


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