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Spinal Cord and PNS

Spinal Cord and PNS. Ventricles of the Brain. Spaces in the brain continuous with the central canal of the spinal cord Filled with CSF. CSF. Specialized capillaries in the pia mater called choroid plexus secrete CSF Clear liquid, similar to blood plasma

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Spinal Cord and PNS

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  1. Spinal Cord and PNS

  2. Ventricles of the Brain • Spaces in the brain continuous with the central canal of the spinal cord • Filled with CSF

  3. CSF • Specialized capillaries in the pia mater called choroid plexus secrete CSF • Clear liquid, similar to blood plasma • More Na+ and less of other dissolved ions • Nutritive and protective, provides a pathway to the blood for waste

  4. Spinal cord • 31 segments, each gives rise to a spinal nerve • Connects PNS to CNS • 2 enlargements give rise to many nerves in those areas • Cervical enlargement • Lumbar enlargement

  5. Internal Anatomy • White matter surrounding a core of gray matter • Resembles a butterfly with wings outstretched • Posterior and Anterior Horns • Gray commissure • Central canal • 3 parts to the white matter – compose tracts • Anterior funiculus • Posterior funiculus • Lateral funiculi

  6. Reflex Arc • Reflex – a series of action potentials coming from a sensory receptor to the brain, then to an effector in response. • For example, stepping on a tack: • Pain receptors send action potential up nerves in leg and spinal cord to brain • Brain sends action potentials down spinal cord and nerves of leg to muscles of the leg • Effectors move the leg • Receptor -> Sensory Neuron -> Interneuron -> Motor Neuron -> Effector

  7. Tracts • Spinal cord like a 2 way street • Ascending Tracts – sensory impulses to the brain • Descending Tracts – motor impulses to effectors • Action potentials can only travel in one direction, therefore spinal cord has neurons oriented in both directions

  8. Plexus • Plexus – a network of nerves • Fibers of various spinal nerves are sorted and recombined in a way that enables fibers associated with a particular peripheral body part to reach it

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