Autonomic Nervous System

Central Nervous System (CNS)

consists of the brain and spinal cord; integrative and control centers of the body

Peripheral Nervous System (PNS)

includes cranial and spinal nerves; serves as communication lines between the CNS and the rest of the body

Somatic Nervous System

part of the peripheral nervous system that conducts impulses from the CNS to skeletal muscles; under somatic motor / voluntary control

Autonomic Nervous System (ANS)

part of the peripheral nervous system that controls visceral motor / involuntary actions; conducts impulses from the central nervous system to its effector organs, including cardiac and smooth muscles and glands

Autonomic Nervous System (ANS)

functions to assists the body in maintaining a constant internal environment (homeostasis)

Autonomic Nervous System (ANS)

participates in appropriate and coordinated responses to external stimuli that are required for the optimal functioning of the somatic nervous system in performing voluntary behaviors

Autonomic Nervous System (ANS)

allows one to efficiently and effectively adapt to environmental stressors and other challenges, though survival without it is possible

Autonomic Nervous System (ANS)

plays a role in the body’s response to an emotional experience

Autonomic Nervous System (ANS)

changes to and abnormal activity from this component of the nervous system contribute to diseases, including hypertension and heart failure, as well as neurological disorders

Sensory / Afferent Division

carries sensory nerve impulses from receptors to the CNS

Motor / Efferent Division

carries motor nerve impulses from CNS to effector organs

Motor / Efferent Division

this is further divided into two divisions: sympathetic and parasympathetic

Sympathetic Division

part of the ANS that mobilizes body systems during activity, often referred to as the "fight or flight" system.

Parasympathetic Division

part of the ANS that conserves energy and promotes "rest and digest" activities

Preganglionic and Postganglionic Neurons

the two neurons that make up the peripheral motor portions of the Autonomic Nervous System (ANS)

Preganglionic Neuron

this is located in the Central Nervous System (CNS) as part of the spinal cord (brain stem or in thoracolumbar sacral division, these have axons which are small-diameter, myelinated, relatively slow conducting B fibers

Postganglionic Neuron

this is located in one of the autonomic ganglia. axons of these neurons are mostly unmyelinated C fibers and terminate on the visceral effectors

Acetylcholine (ACh)

Neurotransmitter released by somatic motor neurons and preganglionic neurons in the ANS.

Norepinephrine (NE)

Neurotransmitter typically released by postganglionic neurons in the sympathetic division.

Cholinergic Transmission

Transmission that uses acetylcholine as the neurotransmitter.

Adrenergic Transmission

Transmission that uses norepinephrine as the neurotransmitter.

Homeostasis

The main function of the ANS is to assist in maintaining a constant internal environment.

Divergence in ANS

Refers to the extensive branching of preganglionic fibers in the sympathetic division.

Muscarinic Receptors

Receptors for acetylcholine located at parasympathetic neuroeffector junctions.

Nicotinic Receptors

Receptors for acetylcholine found at all neuromuscular junctions in the somatic nervous system.

α-Receptors

Adrenergic receptors that can be stimulatory or inhibitory; involved in sympathetic responses.

β-Receptors

Adrenergic receptors that are typically inhibitory except in the heart and kidneys.

Thoracolumbar Division

The region of the spinal cord from which sympathetic neurons originate.

Craniosacral Division

The region of the brainstem and sacral spinal cord from which parasympathetic neurons originate.

Ganglia

Clusters of nerve cell bodies in the peripheral nervous system.

Neurotransmitter Release

The process by which neurotransmitters are released from a neuron to transmit a signal to another cell.

Muscle Innervation

The supply of nerves to a specific muscle or group of muscles.

Acetylcholine and Hormones

Chemical messengers released by postganglionic neurons in the ANS.

Viracosities

Swelling along the axon of a neuron that contains neurotransmitter-filled vesicles.

Epinephrine

A hormone released by the adrenal medulla during sympathetic activation.