Chapter 16 Autonomic Nervous System

autonomic nervous system (ANS)

autonomic nervous system (ANS)

the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms.

sympathetic nervous system

A subdivision of the autonomic nervous system that activates nerves, glands and visceral muscles in times of stress or threat (prepares the body for action); fight or flight; mobilizes energy reserves; increases heart rate, respiratory rate, perspiration, pupil size

parasympathetic nervous system

the subdivision of the autonomic nervous system that operates during relaxed states and that conserves energy; the subdivision of the autonomic nervous system that typically influences activity related to the nourishment, and growth of the body

preganglionic neuron

in the autonomic nervous system of the PNS, a neuron that has its cell body located in the CNS and whose axon extends into the PNS to synapse with a second neuron at an autonomic ganglion. The second neuron's axon synapses with the target organ. The second neuron is term ganglionic or postganglionic neuron

preganglionic fibers

axons of preganglionic neurons

ganglionic neurons

Release neurotransmitters at specific target organs

postganglionic neuron

also called a ganglionic neuron; is part of the autonomic division of the PNS. It is a neuron that has its cell body located in an autonomic ganglion (where a pre-ganglionic neuron synapses with it) and whose axon synapses with the target organ.

postganglionic fibers

also called ganglionic fibers; axons of ganglionic neurons that synapse with target organs

autonomic ganglia

groups of autonomic nerve cells located outside the central nervous system; plural of autonomic ganglion

autonomic ganglion

A cluster of cell bodies of sympathetic or parasympathetic neurons located outside the central nervous system. Site of the synapse between the axon of the preganglionic neuron and the cell body of the postganglionic neuron.

sympathetic chain ganglia

a series (or chain) of connected sympathetic postganglionic cell body clusters positioned along each side of the vertebral column; where synapses between preganglionic fibers and postganglionic neurons take place. Postganglionic neurons control effectors: in body wall, inside thoracic cavity, in head, and in limbs

sympathetic collateral ganglia

Three unpaired ganglia that are found in abdominal cavity, close to target organs.
- celiac
- superior mesenteric
- inferior mesenteric

sympathetic nerves

Autonomic nerves that activate responses in times of stress; heartbeat, respiration, and blood pressure are affected.

Norepinephrine (NE)

the neurotransmitter used by the sympathetic division of the autonomic nervous system at the post-ganglionic organ-level (synapse)

Epinephrine

Neurotransmitter secreted by the adrenal medulla in response to stress. Also known as adrenaline.

celiac ganglion

Innervates stomach, duodenum, liver, gallbladder, pancreas, spleen, and kidney

superior mesenteric ganglion

Innervates small intestine and initial segments of large intestine

inferior mesenteric ganglion

Innervates terminal portions of large intestine, the kidney, urinary bladder, and sex organs

splanchnic nerves

consist of axons that synapse in collateral ganglia

autonomic plexuses

a network of sympathetic and parasympathetic axons

thoracolumbar division

another name for sympathetic division

craniosacral division

another name for parasympathetic division

pterygopalatine ganglion

A cluster of cell bodies of parasympathetic postganglionic neurons ending at the lacrimal and nasal glands.

Ciliary ganglion

Site of postganglionic nerve cells that elicits constriction of pupil

submandibular ganglion

Site of postganglionic neurons that synapse on salivary glands

otic ganglion

site of synapse in glossopharyngeal nerve; that innervates salivary glands

neuroendocrine cells

specialized neurons that release hormones into the bloodstream

adrenal medulla

secretes epinephrine and norepinephrine

autonomic tone

normal background rate of activity that represents the balance of the two systems according to the body's changing needs

Telodendria

Series of fine, terminal extensions branching from the axon tip.

varicosities

Knoblike swellings of certain autonomic axons containing mitochondria and synaptic vesicles.

Alpha 1 receptors

stimulation causes peripheral vasoconstriction and closure of GI and urinary bladder sphincters

Alpha 2 receptors

The stimulation of this receptor are inhibitory; inhibiting parasympathetic neuromuscular and glandular activity

alpha receptors

adrenergic receptors (that are G protein-coupled receptors); that are more sensitive to norepinephrine

beta receptors

adrenergic receptors (that are G protein-coupled receptors) that are found in the heart, lungs, and vascular smooth muscle; more sensitive to epinephrine

nitric oxide (NO)

a neurotransmitter that induces vasodilation

terminal ganglia

located close to effector

intramural ganglia

located within wall of target organ

nicotinic receptors

cholinergic receptors that also respond to stimulation by nicotine; On all ANS postganglionic neurons, in the adrenal medulla, and at neuromuscular junctions of skeletal muscle; Excitatory when ACh binding occurs; Open chemically-gated sodium ion channels

muscarinic receptors

Cholinergic receptors that are located postsynaptically in the effector organs such as smooth muscle, cardiac muscle, and glands supplied by parasympathetic fibers.

dual innervation

most viscera receive nerve fibers from both parasympathetic and sympathetic divisions

visceral reflexes

Unconscious, automatic responses to stimulation of glands, cardiac or smooth muscle; can be inhibited or facilitated by higher centers

long visceral reflexes

Afferent sensory fibers in the dorsal root ganglia or cranial nerve ganglia carry info from visceral organs to spinal cord and brain stem.

short visceral reflexes

Do Not involve the CNS. Sensory Nerve Endings are located in the epithelial layer of the GI tract. Include stretch and Chemo-sensory cells, can involve autonomic postganglionic neurons.

enteric nervous system

The nervous system of the gastrointestinal tract. It controls secretion and motility within the Gi tract, and is linked to the central nervous system.

short-term memory

activated memory that holds a few items briefly before the information is stored or forgotten

long-term memory

the relatively permanent and limitless storehouse of the memory system. Includes knowledge, skills, and experiences.

memory consolidation

the gradual, physical process of converting new long-term memories to stable, enduring memory codes. The strengthening of the neural network that represents a memory

Hippocampus

A neural center located in the limbic system that helps process explicit memories for storage.

skill memories

Learned motor behaviors
Incorporated at unconscious level with repetition

fact memories

specific bits of information

memory engram

a single neural circuit that relates to a single memory formed by experience and repetition

Reticular Activating System (RAS)

a dense network of neurons found in the core of the brain stem; it arouses the cortex and screens incoming information