Spinal Cord & Peripheral

Nervous System Anatomy

Lesson 6

Dorsal

Ventral

Horns

Spinal Cord

Spinal Cord

Dorsal root ganglion (DRG) Sensory input

Ventral root Motor output ~

Peripheral N. S.

Cranial Nerves - 12 pair Spinal Nerves - 31 pair Somatic Division

Sensory information Body Movement

Autonomic division - Homeostasis regulation ~

Cranial Nerves

Ventral surface of brain Olfactory – frontal lobe Optic – thalamus All others from brainstem

Functions Sensory & motor (head/neck) Homeostasis (abdomen)

Optic nerves NOT part of PNS ~

Spinal Nerves

1 pair for each vertebral segment 8 cervical (C1-C8) 12 thoracic (T1-T12) 5 lumbar (L1-L5) 5 sacral (S1-S5) 1 coccygeal ~

Spinal Nerves

Thoracic nerves relatively small back & ribs

Cervical, lumbar, & sacral: large nerves

rest of the body Dermatomes

Receptive fields of body Overlap redundancy ~

Somatic N. S. - Motor

Spinal Cord

Motor Neuron

Striate muscle nerve-dependent uninterrupted neuron excitatory only

Neurotransmitter Acetylcholine (Ach) ~

Effector

+

Autonomic N. S.

Homeostasis Not nerve-dependent

Effectors Smooth Muscle Cardiac Muscle Glands ~

Autonomic Subdivisions

Sympathetic Emergency, flight/fight

Parasympathetic Conservation / vegetative ~

Effector

Ganglion

Preganglionic neuron

Postganglionic neuron

Autonomic: General Features

ACh

Pharmacology of Autonomic NS

Preganglionic neuron releases ACh Different NT at effectors

Parasympathetic division Acetylcholine (Ach)

Sympathetic division: Norepinephrine (NE) ~

Sympathetic vs. Parasympathetic

Sympathetic ganglia near spinal cord interconnected active together long-lasting effects

Parasympathetic ganglia near effector discrete active independently transient effects

Antagonistic regulation ~

Effector Responses

Effector Sympathetic Parasympathetic

Heart Respiration GI Immune system Iris (radial) (sphincter)

Sweat glands no input

Adrenal glands no input ~

Parasympathetic

Post-Pre-

Sympathetic

Adrenal Glands

ACh

Glands

Smooth muscle

NE

Sympathetic Arousal Syndrome

Fight or flight situations Diffuse sympathetic activation

Adrenal glands releases NE into blood maintains sympathetic arousal

Parasympathetic rebound Stress & health ~