The Spinal Cord and Reflexes

The Spinal Cord is protected by: Slide 7.44a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Bony Vertebrae  Vertebral ligaments  Meninges  CSF  Blood brain barrier  Muscles Figure 7.16a

Meninges and Meningitis Slide 7.45a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Meninges- cover brain and spinal cord.  Dura mater-’tough mother’  Arachnoid layer- Web-like  Pia mater-clings to inner surface

Spinal Nerves Slide 7.63 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  31 pairs of spinal nerves -1 pair at the level of each vertebrae  8 Cervical,  12 Thoracic,  5 Lumbar,  5 sacral  1 Coccygeal

Spinal Cord Slide 7.52  Extends from medulla to region of L2  Below T12 is the cauda equina (a collection of spinal nerves)  Enlargements- in cervical & lumbar regions (origin for nerves to extremities. Figure 7.18

Examples of Nerve Distribution Slide 7.66 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.23

Spinal Cord Anatomy Slide 7.53a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Exterior white matter/Interior gray  What makes white matter white? Figure 7.19

Spinal Cord and Nerve Anatomy Slide 7.53b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Internal gray matter - mostly cell bodies  Dorsal (posterior) roots-Sensory info to brain  Ventral (anterior) roots- Motor info from brain Figure 7.19

Spinal Cord Anatomy Slide 7.53c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Central canal filled with cerebrospinal fluid Figure 7.19

Pathways from Body to Brain Slide 7.54  Anterolateral spinothalamic pathway:  Pain, temperature, crude touch, pressure, tickle, itch  Posterior column-medial lemniscus pathway:  Sensory proprioception, discriminating touch, weight discrimination, and vibration

Brain integrates & interprets info Response sent down sends response down 2 major pathways: Slide ) Direct (pyramidal) pathway  Sends impulses that cause precise voluntary movements of the skeletal muscles

Response from Brain sent down: Directly to skeletal muscles Indirectly for  autonomic movements  coordinates body movements with visual stimuli,  maintain skeletal muscle tone & pressure, and  regulate muscle tone in response to movements of the head

A Closer Look at the Spinal Cord 4https:// 4 Can Spinal Injuries heal? Yhttps:// Y 0LEVvS2ybJULhgAqX8PxQt.;_ylu=X3oDMTBs a3ZzMnBvBHNlYwNzYwRjb2xvA2JmMQR2d GlkAw-- ?p=youtube+Walking+Again+After+Spinal+Cord +Injury&tnr=21&vid=09CF1BC5EFB74EA49A1 C09CF1BC5EFB74EA49A1C&l=138&turl=http %3A%2F%2Fts4. 0LEVvS2ybJULhgAqX8PxQt.;_ylu=X3oDMTBs a3ZzMnBvBHNlYwNzYwRjb2xvA2JmMQR2d GlkAw-- ?p=youtube+Walking+Again+After+Spinal+Cord +Injury&tnr=21&vid=09CF1BC5EFB74EA49A1 C09CF1BC5EFB74EA49A1C&l=138&turl=http %3A%2F%2Fts4.

What is Spina Bifida? neural tube defect (NTD) - incomplete development of the spinal cord and its protective coverings. Literally means “ open ” or “ split ” spine Also known as Meningomyelocele or mylomeningocele

Who Gets It? Fetuses in first trimester More common for white women than black women. Women who have already given birth to a child with an NTD. Others who may be at risk? 95% of NTD, including Spina Bifida occurs in women who have no personal or family history of NTDs (Spotlight on Spina Bifida)

Cause Still unknown, but seems to be combination of environmental and genetic factors Studies have found that about 400 micrograms of FOLIC ACID (a water soluble vitamin) every day reduces the risk. Many fetuses that developed SB had a lack of folic acid Women are encouraged to take in more folic acid through foods such as eggs, oranges, and dark leafy greens (Spina Bifida).

The Reflex Arc Slide 7.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Reflex – rapid, predictable, involuntary responses to stimuli  Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector Figure 7.11a

Simple Reflex Arc Slide 7.24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.11b, c

Types of Reflexes and Regulation Slide 7.25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Autonomic reflexes  Smooth muscle regulation  Heart and blood pressure regulation  Regulation of glands  Digestive system regulation  Somatic reflexes  Activation of skeletal muscles

Polysynaptic Reflexes- Complex Reflexes Excite some muscles, inhibit others Exmples: Tendon reflex- prevent muscles from ‘over contracting’, which could tear a tendon Flexor/Withdrawal Reflexes- one muscle must relax so another can contract- touching hot stove Crossed Extensor Reflex- step on a thumb tack, reflex happens on opposite side of body

Dermatomes-sensory Myotomes- muscles Shingles follow dermatome ‘lines’