Nervous System Flashcards
Central Nervous System
Consists of brain and spinal cord. Develop from neural tube in embryo
Peripheral Nervous System
Composed of all nervous structures outside the CNS that conned the CNS to the body. Develop from neural crest cells and as outgrowths of CNS
Gray matter
Containing cell bodies, consists of an outer portion of brain
White matter
Made of axons forming tracts and pathways, inner portion of brain
Ventricles
Spaces filled with cerebrospinal fluid
Meninges
3 connective tissue coverings that surround, protect, and suspend the brain and spinal cord with the cranial cavity and vertebral canal respectively
Dura mater
Thickest and most external of the meninges coverings
Arachnoid mater
Against the internal surface of the dura matter
Pia mater
Adherent to the brain and spinal cord
Somatic part of CNS
Innervates structures derived from somites in embryo, mainly involved with receiving and responding to information from the external environment
Visceral part of CNS
Innervates organ systems in the body and other visceral elements such as smooth muscle and gland in peripheral regions of body. Mainly concerned with detecting and responding to information from the internal environment
Motor neurons develop from
cells within the spinal cord
Sensory neurons develop from
neural crest cells
Proprioception
Sense of determining the position and movement of the musculoskeletal system detected by special receptors in muscles and tendons
Somatic sensory neurons
Carry information (temperature, pain, touch, and proprioception) from the periphery into the CNS. Called somatic sensory afferents or general somatic afferents
Somatic motor fibers
Carry information away from the CNS to skeletal muscles. Called Somatic motor efferents or general somatic efferents
Dermatome
Area of skin supplied by a single spinal cord level or on one side by a single spinal nerve
Muscle moving shoulder joint are innervated mainly by spinal nerves from spinal cord levels
C5 and C6
Muscles moving elbow are innervated mainly by spinal nerves from spinal cord levels
C6 and C7
Muscles in the hand are innervated mainly by spinal nerves from spinal cord levels
C8 and T1
Myotome
Region of skeletal muscle innervated by a single nerve or spinal cord level. Most individual muscles of body are innervated by more than one spinal cord level, so the evaluation of myotomes is usually accomplished by testing movements of joints or muscle groups
Autonomic division of PNS consists of
sympathetic and parasympathetic parts
Visceral sensory neurons arise from
neural crest cells, send processes medially into the adjacent neural tube and laterally into regions associated with the developing body (general visceral afferent fibers)
Visceral motor neurons arise from
cells in lateral regions of the neural tube, send processes out of the anterior aspect of the tube (general visceral efferent fibers)
Preganglionic motor neurons and fibers
Visceral motor neurons located in spinal cord and their axons
Postganglionic motor neurons and fibers
Visceral motor neurons located outside the CNS and their axons
Ganglion
Cell bodies of visceral motor neurons outside the CNS often associate with each other in a discrete mass
Nerves in cranial region that visceral components exit
CN III, VII, IX, and X (4 of 12 cranial nerves) (parasympathetic)
Nerves in spinal cord that visceral components exit
Spinal cord levels T1 through L2 (sympathetic) and S2 to S4 (parasympathetic)
Sympathetic system
innervates structures in peripheral regions of the body and viscera
Parasympathetic system
More restricted to innervation of the viscera only
White ramus communicans
Carries pregagnlionic sympathetic fibers and appears white because the fibers it contains are myelinated. Connects anterior rami of T1 to L2 to sympathetic trunk
Gray ramus communicans
Connects sympathetic trunk or a ganglion to the anterior rams and contains the postganglionic sympathetic fibers. Appears gray because nonmyelinated. Positioned medial to the white rams communicants. Associated with all spinal nerves
Preganglionic sympathetic fibers that enter a paravertebral ganglion or the sympathetic trunk through a white rams communicants may take the following four pathways to target tissues:
- Preipheral sympathetic innervation at the level of origin of the preganglionic fiber.
- Peripheral sympathetic innervation above or below the level of origin of the preganglionic fiber. (may/may not have visceral motor input directly from spinal cord i.e. other than T1-L2)
- Sympathetic innervation of thoracic and cervical viscera (mainly from spinal cord levels T1-T5 innervate cranial, cervical, and thoracic viscera.) Synapse with post ganglionic motor neurons in ganglia and then leave medially.
- Sympathetic innervation of the abdomen and pelvic regions and the adrenals (without synapsing in sympathetic trunk to form splanchnic nerves derived from spinal cord levels T5 to L2, generally connect with sympathetic ganglia around roots of major arteries that branch from the abdominal aorta. Some pass through system to adrenal gland where synapse directly with cells of adrenal medulla)
Paravertebral sympathetic trunk
Extends entire length of vertebral column, made of ascending and descending fibers together with all the ganglia
Superior cervical ganglion
Highest ganglion in the neck, all sympathetics passing into the head have preganglionic fibers that emerge from spinal cord level T1 and ascend in the sympathetic trunks to the highest ganglion in the neck
