15.1 Somatic vs Autonomic

two parts of the nervous system

CNS and PNS

CNS

• brain

• spinal cord

two parts of the PNS

• somatic

• autonomic

somatic nervous system and its two parts

consciously perceived or controlled

• somatic sensory

• somatic motor

somatic sensory

detects signals

somatic motor

sends signals from CNS to skeletal muscles

autonomic nervous system

• organs

• below conscious level

• maintains homeostasis

• fight or flight

motor neurons of somatic NS

• single motor neuron from CNS to skeletal muscle fibers in somatic nervous system

• myelinated

• large diameter

• releases ACH from synaptic knob to excite muscle fiber

motor neurons of autonomic nervous system

has two lower motor neurons

1. preganglionic neuron

2. ganglionic neuron

preganglionic neuron

• myelinated

• cell body within brainstem or spinal cord

• releases ACH from knob to excite 2nd motor neuron

ganglionic neuron

• cell body within autonomic ganglion

• very thin, unmyelinated axons to cardiac muscle, smooth muscle, or gland

• releases ACH or NE from knob to either excite or inhibit effector

neuronal convergence

multiple preganglionic neurons synapsing on one ganglionic neuron

neuronal divergence

one preganglionic neuron synapsing with numerous ganglionic neurons

hypothalamus

command center for autonomic fxns, emotions

brainstem

major ANS reflex centers

spinal cord

ANS reflex centers for defecation and urination