Chapter 13: Central Nervous System (CNS)

Chapter 13 Central Nervous System (CNS) · brain and spinal cord Peripheral Nervous System (PNS) · cranial nerves and spinal nerves Spinal Cord · made of nervous tissue · contains spinal nerves that communicate with peripheral organs · the spinal cord ends between vertebrae L1 and L2 (conus medullaris) · 31 segments · contains both grey matter (neuron cell bodies) and white matter (myelinated axons) · posterior median sulcus (shallow groove) · anterior median fissure (deep groove) · internal passageway (central canal) that contains CSF Spinal Roots and Ganglia · roots = axons · ganglia = cell bodies · Posterior (dorsal) root: sensory neuron axons (info to CNS) · Anterior (ventral) root: motor neuron axons (info to effectors) · Posterior and anterior roots pass through intervertebral foramen information comes in through the back and out through the front (dorsal → ventral) Protection of Spinal Cord · epidural space (filled with adipose tissue and blood vessels) · 3 spinal meninges ① Dura mater ② Arachnoid mater ↳ subarachnoid space holds CSF ③ Pia mater · there is NO space between dura mater and arachnoid mater Spinal Nerves and Rami · 31 spinal nerves ↳ 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal nerve · mixed nerve: contains both motory and sensory nerves (afferent and efferent fibers) · Spinal nerves form branches to carry motor and/or sensory information between CNS and PNS ↳ posterior ramus: sensory and motor innervation to skin and back muscles ↳ anterior ramus: body wall, organs, limbs (everything else) ↳ rami communicantes (in T1-L2) -white ramus communicans -grey ramus communicans · spinal nerves supply specific regions called dermatomes Autonomic ganglia Postganglionic Preganglionic White Matter · divided into 3 columns ↳ posterior white column ↳ anterior white column ↳ lateral white column · tract: a bundle of axons in the CNS that relay the same type of information in the same direction · Ascending tract: carries sensory into toward the brain · Descending tract: conveys motor commands to the spinal cord Myelinated axons Gray Matter · "H" or butterfly shape around central canal · masses of grey matter in the CNS are called nuclei Info enters through the back · posterior horns contain somatic and visceral sensory nuclei Motor info leaves through front · anterior horns contain somatic motor nuclei · lateral horns contain visceral motor nuclei Cell bodies and interneurons Dermatomes · dermatome: a specific bilateral region of the skin surface monitored by a single pair of spinal nerves ↳ you do not need to know which nerve/ region controls what You should understand this process: Nerve Plexuses · nerve plexus: a network of nerves and where they start to branch off · 4 Spinal nerve plexuses: ↳ cervical plexus ↳ brachial plexus ↳ lumbar plexus ↳ sacral plexus (should know most names based on regions of the body) Reflexes Reflex Arc: · reflex arc: the route followed by nerve impulses ② Activation of sensory neuron + relays to CNS the spinal cord ④ Activation of a motor neuron · reflex: an immediate involuntary motor response ① Activation of sensory receptor · Monosynaptic reflex: involves a single segment of ③ Information processing in CNS · Polysynaptic reflex: integrates motor output ⑤ Response by the peripheral effector from several spinal segments Classification of Reflexes: