CH11 Efferent Division of Peripheral Nervous System

Efferent neurons

Carry commands from CNS to the muscles and glands of the body.

Somatic motor neurons

Control skeletal muscles and are mostly voluntary.

Autonomic neurons

Control smooth muscle, cardiac muscle, many glands, and some adipose tissue; mostly involuntary.

Sympathetic branch

Part of the autonomic division associated with 'fight-or-flight' responses.

Parasympathetic branch

Part of the autonomic division associated with 'rest-and-digest' responses.

Antagonistic control

Most internal organs are under antagonistic control, where one autonomic branch is excitatory and the other is inhibitory.

Preganglionic neuron

First neuron in the autonomic pathway with its cell body located in the CNS, projecting to an autonomic ganglion.

Postganglionic neuron

Second neuron in the autonomic pathway with its cell body in the autonomic ganglion, projecting to the target tissue.

Ganglion

A cluster of neuronal cell bodies outside the CNS that acts as a mini-integration center.

Acetylcholine (ACh)

A neurotransmitter released by both sympathetic and parasympathetic preganglionic neurons onto nicotinic cholinergic receptors.

Norepinephrine (NE)

A neurotransmitter secreted by most postganglionic sympathetic neurons onto adrenergic receptors on the target cell.

Muscarinic cholinergic receptors (mAChR)

Receptors on the target cell where most postganglionic parasympathetic neurons secrete ACh.

Sympathetic cholinergic neurons

Postganglionic neurons that secrete ACh onto sweat glands.

Nonadrenergic, noncholinergic neurons

Neurons that use other types of neurotransmitters instead of norepinephrine or acetylcholine.

Homeostatic control centers

Located in the hypothalamus, pons, and medulla, they integrate sensory information and lead to autonomic, endocrine, and behavioral responses.

Behavioral responses

Responses that may be integrated in brain centers into motivated behaviors and control movement.

Sensory information integration

Occurs in the cortex and limbic system, creating emotions that influence autonomic output.

Tonic control

A type of control where only sympathetic innervation is present, such as in sweat glands and smooth muscles in most blood vessels.

Cooperative control

Occurs when different tissues work together to achieve a common goal.

Neurotransmitter receptor

Often determines the response in the target tissue.

Integration of autonomic function

Involves sensory info from somatosensory and visceral receptors, leading to various responses.

Vagus Nerve

Contains about 75% of all parasympathetic fibers.

Autonomic Varicosities

Release neurotransmitter over the surface of target cells.

G Protein-Coupled Receptors

Receptors that have multiple subtypes in the autonomic nervous system.

Alpha Receptors

React strongly to norepinephrine and weakly to epinephrine.

a1-Receptors

Cause muscle contraction or secretion (exocytosis).

a2-Receptors

Decrease cAMP; cause smooth relaxation or decreased secretion.

Beta Receptors

Have different affinities for catecholamines.

b1-Receptors

Respond equally to epinephrine and norepinephrine.

b2-Receptors

More sensitive to epinephrine than norepinephrine.

b3-Receptors

More sensitive to norepinephrine than epinephrine.

Muscarinic Receptors

Stimulated by parasympathetic pathways on target cells.

Adrenergic Receptors

Receptors that respond to norepinephrine and epinephrine.

α1 Receptor

Found in most sympathetic target tissues; NE > E, increases IP3 and intracellular Ca²⁺.

α2 Receptor

Found in the gastrointestinal tract and pancreas.

β1 Receptor

Found in heart muscle and kidney; NE = E, increases cAMP.

β2 Receptor

Found in certain blood vessels and smooth muscle of some organs.

β3 Receptor

Found in adipose tissue; NE > E, increases cAMP.

NN Receptor

Found in postganglionic autonomic neurons; opens nonspecific monovalent cation channels.

NM Receptor

Found in skeletal muscle; opens nonspecific monovalent cation channels.

M1, M3, M5 Receptors

Found in the nervous system and parasympathetic target tissues; increases IP3 and intracellular Ca²⁺.

M2, M4 Receptors

Found in the nervous system and parasympathetic target tissues; decreases cAMP and opens channels.

Sympathetic Division

If a neuron releases norepinephrine, it is part of which division of the peripheral nervous system?

Physiological Responses of Sympathetic Action

Which physiological responses results from sympathetic action?

Properties of Autonomic Nervous System

The two branches of the autonomic nervous system have which properties?

Sympathetic Nervous System Origin

The sympathetic nervous system originates in the _______ region(s) of the spinal cord.

Parasympathetic Nervous System Fibers

The parasympathetic nervous system has long preganglionic and short postganglionic nerve fibers.

Neurotransmitter in Autonomic Synapse

The neurotransmitter in the synapse between pre- and postganglionic autonomic neurons is acetylcholine.

Norepinephrine Production

The neurotransmitter norepinephrine is made from tyrosine.

Receptor on Parasympathetic Target Cells

The receptor found on most parasympathetic target cells is muscarinic cholinergic.

Incorrect Ligand-Receptor Pairing

Which pairings between ligand and receptor is NOT correct?

Example of Parasympathetic Response

Which is an example of a parasympathetic response?