SJSU SP24 BIOL-65 Chapter 16 - Autonomic Nervous System

autonomic nervous system

a motor division of the nervous system that innervates glands, smooth muscle, and cardiac muscle; consists of sympathetic and parasympathetic divisions and functions largely without voluntary control

visceral (organ) motor system

involuntary control of effectors: glands, cardiac muscle, smooth muscle

visceral reflexes

unconscious, automatic, stereotypes responses of visceral effectors to stimuli

sympathetic division

it increases alertness, heart rate, blood pressure, pulmonary airflowm blood glucose concentration, and blood flow to cardaic and skeletal muscle; also reduces blood flow to the skin and digestive tract; referred to as "fight or flight"

parasympathetic division

has a calming effect on many body functions; associated with reduced energy expenditure and normal bodily maintenance, including such functions as digestion and waste elimination; "resting and digesting"

autonomic tone

balance between activity of sympathetic and parasympathetic nervous systems

Preganglionic fiber

begins with a neurosoma in the brainstem or spinal cord; axon extends to an autonomic ganglion somewhere outside the CNS; meets the neurosoma of a second neuron and secretes the neurotransmitter acetylcholine to stimulate the latter; myelinated

postganglionic fiber

from the axon of the second neuron, leaves the ganglion and extends the rest of the way to the target organ or cells; secretes either ACh or norepinephrine; can have excitatory or inhibitory effect on target cells; unmyelinated

Somatic effectors

Skeletal muscle

Autonomic effectors

glands, smooth muscle, cardiac muscle

Somatic control

Voluntary

Autonomic control

Involuntary

Somatic Efferent pathways

one nerve fiber from CNS to effector; no ganglia

Autonomic Efferent pathways

two nerve fibers from CNS to effector; synapse at a ganglion

Somatic effect on target cells

Always excitatory

Autonomic Effect on target cells

Excitatory or inhibitory

Thoracolumbar division

another name for sympathetic division; arises from the thoracic and lumbar regions of the spinal cord; preganglionic neurosomas are in lateral horns of spinal cord; short preganglionic fibers and long postganglionic fibers; sympathetic chain ganglia from cervical to coccygeal levels

Craniosacral division

also known as parasympathetic division; long preganglionic fibers and short postganglionic fibers; terminal ganglia are in or near target organ

enteric nervous system

nervous system of digestive tract; innervates smooth muscle and glands; regulates motility of esophagus, stomach, and intenstines; regulates secretion of digestive enzymes and acid