Chapter 14: Autonomic Nervous System

Somatic Nervous System

Innervates skeletal muscles

Single, thick myelinated axon

Releases ACh; Always stimulatory

Autonomic Nervous System

Innervates cardiac muscle, smooth muscle, & glands

Two-neuron chain

Preganglionic release ACh; Postganglionic release norepinephrine; Either stimulatory or inhibitory

Parasympathetic Division

Rest-and-digest

Promotes maintenance functions and conserves energy

Decrease heart rate, blood pressure, relaxed

Short-lived, highly localized

Sympathetic Division

Fight-or-flight

Mobilizes body during activity

Increase heart rate, dry mouth, sweat, dilated pupils

Longer-lasting, bodywide effects

Dual Innervation

Innervation of an organ by both sympathetic and parasympathetic divisions

Divisions cause opposite effects

Parasympathetic Fibers

Craniosacral; Origionate in brain and sacral spinal cord

Long preganglionic, short postganglionic

Sympathetic Fibers

Thoracolumbar; Originate in thoracic and lumbar regions of spinal cord

Short preganglionic, long postganglionic

Oculomotor Nerves (III)

Control smooth muscle of eye

Cause pupils to constrict and lenses to bulge for focusing on near objects

Vagus Nerves (X)

Serve all thoracic and abdominal viscera

Visceral Reflex Arc

Two consecutive neurons in the motor pathway

Cholinergic Fibers

ACh is released

All ANS preganglionic axons

All parasympathetic postganglionic axons

Adrenergic Fibers

Norepinephrine is released

Almost all sympathetic postganglionic axons, except sweat glands

Nicotinic Receptors

Found on postganglionic neurons, and neuromuscular junction skeletal muscles

Always stimulatory; Opens ion channels

Muscarinic Receptors

Found on all effector cells & parasympathetic target organs

ACh effect can be excitatory or inhibitory of cardiac muscle

Cardiac slows heart rate; Smooth increases motility

Facial Nerves (VII)

Stimulate large glands in head

Nasal and lacrimal glands, submandibular and sublingual salivary glands

Glossopharyngeal Nerves (IX)

Stimulate parotid salivary glands

Alpha 1

Constricts blood vessels of skin and viscera

Beta 1

Increases heart rate and contractility

Beta 2

Dilates bronchioles and blood vessels to skeletal muscle

Adrenal medulla, sweat glands, arrector pili muscles, kidneys, and almost all blood vessels

Which target organs are not dually innervated