Ms. Herrera

Spinal Cord Extends from the foramen magnum of the skull to the first or second lumbar vertebra Comprised of 31 pairs of spinal nerves 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal Extends from the foramen magnum of the skull to the first or second lumbar vertebra

Spinal Cord Anatomy Internal gray matter is mostly cell bodies Dorsal (posterior) horns Anterior (ventral) horns Gray matter surrounds the central canal Central canal is filled with cerebrospinal fluid Exterior white mater—conduction tracts Dorsal Column: contains sensory (afferent) tracts Lateral & Ventral Column: Contains both ascending and descending (motor: efferent tracts)

Peripheral Nervous System (PNS) Comprised of nerves and ganglia (neuronal cell bodies) that are outside the CNS Mixed nerves Both sensory and motor fibers All spinal nerves are mixed Sensory (afferent) nerves Carry impulses toward the CNS Found in sensory structures Motor (efferent) nerves Carry impulses away from the CNS Arise in CSN and include nerves from Somatic and Autonomic division

Cranial Nerves There are a total of 12 that are identified by name and number Mostly serve the head and neck Most are mixed nerves, but three are sensory only Peripheral Nervous System (PNS)

PNS: Spinal Nerves There is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairs Formed by the combination of the ventral and dorsal roots of the spinal cord Named for the region from which they arise

PNS: Spinal Nerves Spinal nerves divide soon after leaving the spinal cord Dorsal rami—serve the skin and muscles of the posterior trunk Ventral rami—form a complex of networks (plexus) for the anterior

PNS: Spinal Nerves

PNS: Autonomic Nervous System A.K.A. involuntary nervous system Motor subdivision of the PNS Consists only of motor nerves Actions: Regulates activities of cardiac and smooth muscles and glands Two subdivisions Sympathetic division Parasympathetic division

PNS: Differences Between Somatic and Autonomic Nervous Systems Somatic Autonomic Nerves one motor neuron Effector organs skeletal muscle Neurotransmitters always use acetylcholine Nerves preganglionic and postganglionic nerves Effector organs smooth muscle, cardiac muscle, and glands Neurotransmitters use acetylcholine, epinephrine, or norepinephrine

Anatomy of the Autonomic Nervous System

PNS: Autonomic Functioning Sympathetic Parasympathetic A.K.A. “fight-or-flight” response Response to unusual stimulus Takes over to increase activities Release acetycholine Remember as the “E” division Exercise, excitement, emergency, and embarrassment “housekeeping” activities Conserves energy Maintains daily necessary body functions Release norepinephrine Remember as the “D” division digestion, defecation, and diuresis