anatomy 18.1 pt 4

Purpose of the two-neuron chain in the ANS

It allows nerve impulses to be grouped and dispersed efficiently through neuronal convergence and divergence.

Airline analogy in the ANS

An airline system using connecting flights and airport hubs.

First flight in the airline analogy

The preganglionic axon.

Flight from Indianapolis to Chicago in the analogy

The preganglionic axon traveling from the CNS toward an autonomic ganglion.

Comparison of first flight to preganglionic axon

Both transport passengers or nerve impulses toward a central connecting point.

Chicago airport hub in the analogy

The autonomic ganglion.

What happens at the autonomic ganglion in the analogy?

Preganglionic and postganglionic pathways meet and connect.

Other preganglionic flights arriving at the airport hub

Axons from other preganglionic neurons converging on ganglionic neurons.

Connecting flight from Chicago to Miami in the analogy

The ganglionic neuron and its postganglionic axon.

Miami in the airline analogy

The final effector destination.

Function of the postganglionic axon in the ANS

It sends a nerve impulse from the ganglionic neuron to the effector.

Two flights versus direct flight analogy

A direct flight would be more direct, but the connecting-flight system allows the airline to transport and distribute many passengers efficiently.

Reason the airline uses an airport hub

It is more efficient to send passengers to a central location before distributing them to different destinations.

Airport hub illustrating neuronal convergence

Many incoming flights represent many preganglionic neurons converging at an autonomic ganglion.

Airport hub illustrating neuronal divergence

Passengers can leave the hub on different connecting flights, representing nerve impulses being distributed to numerous ganglionic cells.

What does neuronal convergence allow in the ANS?

Numerous preganglionic neurons can influence a single ganglionic cell.

What does neuronal divergence allow in the ANS?

One preganglionic neuron can influence numerous ganglionic cells.

Energy efficiency of the two-neuron ANS pathway

It allows many nerve impulses to be grouped and dispersed using a limited number of neurons.

Relationship of autonomic ganglion to the two neurons of the ANS pathway

The preganglionic neuron synapses with the ganglionic neuron within an autonomic ganglion.

Location of dendrites and cell body of a preganglionic neuron

Within the CNS, either the brain or spinal cord.

What does the preganglionic axon synapse with?

With a ganglionic neuron within an autonomic ganglion.

Neurotransmitter used by preganglionic neuron in the ANS

Acetylcholine.

Neurotransmitters used by postganglionic axon at the effector

Acetylcholine (ACh) or norepinephrine (NE).

Final destination of the postganglionic axon

An effector.

Types of structures that can serve as autonomic effectors

Cardiac muscle, smooth muscle, and glands.

Main purpose of the autonomic nervous system

To maintain homeostasis by regulating physiological processes within optimal ranges.

Need for the ANS to adjust physiological variables

To meet changing body needs.

Advantage of the ANS two-neuron arrangement

It provides extensive convergence and divergence, allowing increased communication and control.

Key comparison between SNS and ANS motor pathways

The SNS uses one motor neuron directly from the CNS to skeletal muscle, while the ANS uses two motor neurons with an autonomic ganglion between them.

Key functional difference between SNS and ANS

The SNS involves processes that are consciously perceived or controlled, whereas the ANS regulates processes below the conscious level to help maintain homeostasis.