Figure 15.1

The ANS and Visceral Sensory Neurons

Terms

• Synapse – junction between 2 neurons that communicates the message from the presynaptic neuron to the postsynaptic neuron

• Ganglion (pl. ganglia) – a cluster of neuronal cell bodies in the PNS

• Preganglionic neuron – cell body lies within the CNS - its axon, the preganglionic fiber synapses with the 2nd motor neuron, the ganglionic neuron, in a peripheral autonomic ganglion

• Postganglionic fiber (axon) of the ganglionic neuron extends to the visceral organs

• Issue from different regions of the CNS

• Sympathetic - aka the thoracolumbar division

• Parasympathetic – aka the craniosacral division

Figure 15.3

Anatomical Differences

Anatomical Differences• Length of postganglionic fibers: sympathetic are

long and parasympathetic are short

• Branching of axons: sympathetic axons are highly branched to influence many organs while parasympathetic axons have few branches so have a localized effect

• Sympathetic release norepinephrine (adrenergic)

• Parasympathetic release acetylcholine (cholinergic)

Anatomical Differences

Figure 15.4a

Anatomical Differences

Figure 15.4b

Neurotransmitters • Cholinergic fibers release the

neurotransmitter ACh– All ANS preganglionic axons– All parasympathetic postganglionic axons

• Adrenergic fibers release the neurotransmitter NE– Most sympathetic postganglionic axons– Exceptions: sympathetic postganglionic fibers

secrete ACh at sweat glands and some blood vessels in skeletal muscles

Parasympathetic and Sympathetic Nervous System:

• A subdivision of the PNS• Not under conscious control• Controlled by medulla oblongata and

hypothalamus• PNS supplies stimulation via motor

nerves to smooth and cardiac muscle and to glands

Biofeedback:• Conscious control of ANS• Ex. Yoga, meditation• Monitoring devices useful for:

- epilepsy- digestive problems- chronic headaches- high blood pressure- generalized stress- anxiety- insomnia

• Sympathetic• Parasympathetic

CNS ganglionUnmyelinated motor neuron

Myelinated motor neuron

effector

Work antagonistically

Neurotransmitter is norepinephrine“fight or flight”

E = exercise, excitement, emergency, and embarrassment

Fight or flight adaptive effects include: • increased cardiac activity, increased blood

pressure, dilation of skeletal muscle blood vessels• constriction of blood vessels in skin• dilation of pupil• inhibition of gut and urinary bladder contractions• increase in blood glucose and free fatty acid levels• dilation of bronchial smooth muscle  • secretion of viscous saliva • sweating• lower threshold for reticular formation activation• liver produces glucose to provide energy for muscle

contraction.

neurotransmitter is acetylcholine

D = digestion, defecation, diuresis (urinating)

Parasympathetic activation results in: • decreased cardiac activity• secretion of watery saliva and stimulation of GI

secretions• contraction of urinary bladder• increased insulin and glucagon secretion• bronchiole constriction

Sites of synapses between pre and postsympathetic ganglia

• sympathetic trunk ganglia - located from base of skull to

coccyx• prevertebral ganglia

- innervates organs below the diaphragm

Site of synapses between pre and post parasympathetic ganglia

• terminal ganglia- Located close to or within the

wall of a visceral organ

• when there is no escape route or no way to win– causes massive activation of parasympathetic division– loss of control over urination and defecation

Paradoxical fear

Parasympathetic Cranial Nerves• Oculomotor nerve

– ciliary ganglion in orbit

– ciliary muscle & pupillary constrictor muscle inside

eyeball

• Facial nerve

– pterygopalatine and submandibular ganglions

– supply tears, salivary & nasal secretions

• Glossopharyngeal

– otic ganglion supplies parotid salivary gland

• Vagus nerve

– many brs supply heart, pulmonary and GI tract as far as the midpoint of the colon

Autonomic Plexuses in the Thorax, Abdomen & PelvisAutonomic Plexuses in the Thorax, Abdomen & Pelvis

Types of connections bwtn ganglia & postganglia neurons in the sympathetic division

Types of connections bwtn ganglia & postganglia neurons in the sympathetic division

Examples:• Digestion• Blood pressure• Defecation• Urination

Components of an Autonomic Reflex:1. Receptor2. Sensory neuron3. Integration center4. Motor neuron5. Effector (smooth or cardiac muscle, or a gland)

Hypothalamus & MedullaMajor control and integration center

of the ANS

Medulla oblongata

1. What neurotransmitter is produces from the Somatic nervous system, Sympathetic, and Parasympathetic nervous system?

2. What effector organs are targeted from the ANS?3. Where does sensory input for the ANS come from?4. List the components of an autonomic reflex arc.5. What part of the brain is the major control and

integration center of the ANS?6. What effect does the parasympathetic nervous system

have on the digestive system?7. What effect does the sympathetic nervous system

have on the liver?