ch 9: autonomic nervous system

somatic nervous system

pertaining to the body

voluntary

excitatory

movement, muscle cell excitation

autonomic nervous system

involuntary, unconscious

regulates activity of cardiac muscle, smooth muscle, and glands (visceral organs and blood vessels)

excitatory or inhibitory

two subdivisions:

PNS

SNS

ganglion

group of cell bodies

preganglionic neurons

have cell bodies in CNS

postganglionic neurons

have cell bodies in autonomic ganglia

effector organs

somatic motor: skeletal muscles

autonomic motor: cardiac muscle, smooth muscle, and glands

presence of ganglia

somatic motor: no ganglia

autonomic motor: cell bodies of postganglionic autonomic fibers located in paravertebral, prevertebral (collateral), and terminal ganglia

numbers of neurons from CNS to effector

somatic motor: one

autonomic motor: two

types of neuromuscular junction

somatic motor: specialized motor and plate

autonomic motor: no specialization of postsynaptic membrane, all areas of smooth muscle cells contain receptor proteins of neurotransmitters

effect of nerve impulse on muscle

Somatic Motor: Excitatory only

Autonomic Motor: Either excitatory or inhibitory

type of nerve fibers

somatic motor: fast-conducting, thick and myelinated

autonomic motor: slow conducting; preganglionic fibers lightly myelinated but thin; postganglionic fibers unmyelinated and very thin

effect of denervation

Somatic Motor: Flaccid paralysis and atrophy

Autonomic Motor: Muscle tone & function persist; target cells show denervation hypersensitivity

SNS

fight or flight

norepinephrine (NE)

epinephrine (E)

acetylcholine (ACh)

short preganglionic neurons; long postganglionic neurons

how does SNS prepare body for intense physical activity in emergency

increased heart rate

increased blood glucose concentration

increased blood flow to skeletal muscles

pupil dilation

PNS

rest and digest

ACh

long preganglionic neurons; very short (or within the organ itself) postganglionic neurons

opposite effects compared to sympathetic division

PNS effects

slowed heart rate

dilation of visceral organ blood vessels

increased digestive activity