Ch. 14: Autonomic Nervous System (ANS)

Sympathetic (Thoracolumbar) Division

"Fight or flight." Division of the ANS. Promotes adjustments during exercise, emergencies, intense stress. Effects on body can be widespread; involve the entire body. Fibers originate in the thoracic and lumbar spinal cord. Preganglionic axons are short; project to ganglia located close to CNS. Postganglionic axons are long; project to targets. Ganglia are close to spinal cord. Preganglionic axons leave the CNS from thoracic and lumbar retions of spinal cord (T1-L2). __________ has an additional part involving the adrenal medulla. Short preganglionic (myelinated) nerves are from CNS, and exit thoracic and lumbar spinal nerves T1-L2, synapsing close to CNS in collateral (paravertebral) ganglia (sympathetic chains); also may synapse in the adrenal medulla, releasing ACh. Long postganglionic (unmyelinated) nerves are from collateral (paravertebral) ganglia (sympathetic chains), which are within the target organ, and secrete NE for most; ACh for fibers to sweat glands and some blood vessels.

Parasympathetic (Craniosacral) Division

"Rest or Digest." Division of the ANS. Promotes 'housekeeping' functions. E.g. after eating a meal. Effects tend to be more localized. Fibers originate in the brain stem (cranial fibers) or sacral spinal cord. Preganglionic fibers are long; project almost all the way to the target organs. Synapse in terminal ganglia with the postganglionic neurons. Postganglionic fibers are short; project to targets. Ganglia are within or near visceral effector organs. Preganglionic fibers only leave CNS from brainstem (4 cranial nerves) and from sacral region of spinal cord (sacral nerves S2-S4). _________ effects tend to be localized. Cranial outflow: __________ neurons carried in 4 cranial nerves: Oculomotor (III) Nerves, Facial (VII) Nerves, Glossopharyngeal (IX) Nerves, Vagus (X) Nerves. Sacral outflow: _________ neurons carried in sacral spinal nerves S2-S4. Innervate last part of large intestine, urinary bladder, ureters, reproductive organs. Promote defecation and urination. Long preganglionic (myelinated) from CNS exit CNS via cranial nerves III, VII, IX and X; sacral spinal nerves S2-S4 and synapse close to or within target organ in the terminal ganglia, secreting ACh. Short postganglionic (unmyelinated) nerves are from the parasympathetic (terminal) ganglia, and are within the target organ, secreting ACh.

Single Preganglionic Neuron

A _________ can activate numerous ganglionic neurons going to many effectors. Results in sympathetic effects being widespread.

Autonomic Ganglia

A _________ is a cluster of nerve cell bodies in the autonomic nervous system. The two types, are sympathetic ganglion and parasympathetic ganglion.

Consensual Response

A _________ occurs on the opposite side (contralateral) from where the stimulus takes place. The __________ shows that there is a consensus b/w the pupils - both constrict even if only one eye is stimulated. Protects both eyes from bright light.

Direct Response

A __________ occurs on the same side (ispilateral) as where the stimulus takes place.

Epinephrine, Norepinephrine

Adrenal medulla secretes _________ (adrenaline) and _________ as hormones.

Acetylcholine (ACh)

All somatic motor neurons secrete _________. _________ always stimulates skeletal muscles; causes contraction. All sympathetic and parasympathetic preganglionic neurons secrete ____________ to excite the postganglionic neurons. All parasympathetic postganglionic neurons secrete _________.

Sympathetic Trunk Ganglia

Also called the sympathetic chain or paravertebral ganglia. The __________ are a paired bundle of nerve fibers that run from the base of the skull to the coccyx.

Cardiac, Smooth, Glands

Autonomic motor neurons innervate _________ muscles, _________ muscles and _________.

Pupillary Constriction

Autonomic reflexes that occur in the eye. Bright light causes __________ (parasympathetic effect). Size of pupils is controlled by two smooth muscles in the iris. Sphincter pupillae muscle contraction decreases pupil size. Stimulus: bright light in one eye. Direct (ipsilateral) response: stimulated pupil constricts. Consensual (contralateral) response: opposite (unstimulated) puil constricts.

Pupillary Dilation

Autonomic reflexes that occur in the eye. Dim light or extreme emotion cause __________ (sympathetic effect). Size of pupils is controlled by two smooth muscles in the iris. Dilator pupillae muscle contraction increases pupil size. Stimuli: dim light or intense emotion. Covering one eye should cause both pupils to dilate (consensual). Eyes may "light up" when you're pleased or excited or scared.

Iris

Colored part of eye. Composed of two muscles; sphincter pupillae and dilator pupillae

Autonomic Nervous System

Controls unconscious involuntary functions: digestion, heart rate, blood pressure, pupil size, etc. Has 2 divisions: Sympathetic and parasympathetic divisions. Efferent pathways: Two neuron chain. Myelinated preganglionic neuron projects from CNS to the PNS. Synapses in an autonomic ganglion with a nonmyelinated postganglionic neuron. Postganglionic neuron projects from ganglion to effector organs. Positive or negative effect: Stimulatory or inhibitory, depending on neurotransmitter and receptors on effector organs. Effector organs: smooth muscle (e.g. in gut), glands, cardiac muscles.

Adrenal Medulla

Deepest part of adrenal gland. Some sympathetic preganglionic fibers project to the _________ and then synapse. _________ is innervated only by sympathetic nerves. In the _________, epinephrine (adrenaline) is mostly secreted and some norepinephrine are secreted into the blood as hormones. _________ is like a sympathetic ganglion, but without postganglionic fibers. Epinephrine and NE supplement the NE secreted from sympathetic neurons; enhances overall "flight or fight" response.

Sympathetic Preganglionic Neurons

Destinations of _________. Exit spinal cord via T1-L2 spinal nerves. Some project to ganglia that form the sympathetic trunk. _________ excite postganglionic neurons which send signals throughout the body for a full bodywide "fight or flight" response.

Atropine

Drug from belladonna plant. Is a parasympathetic inhibitor. Blocks receptors for ACh on sphincter pupillae muscles.

Somatic Nervous System

Efferent pathways: A single myelinated neuron projects from CNS (brain or spinal cord) all the way to the skeletal muscle in the _________. Ex: 1. Trigeminal (V) Nerves project to chewing muscles. 2. Facial (VII) Nerves project to muscles of facial expression. 3. Lower motor neurons in spinal nerves project to skeletal muscles in body below the head and neck. Positive Effect: always stimulatory; always causes contraction. Effector organs: skeletal muscles.

Glycogenolysis

Liver releases glucose during an emergency (sympathetic effects).

Terminal Ganglia

Most are small _________ or intramural ganglia, so named because they lie near or within (respectively) the organs they innervate. This happens in the parasympathetic (craniosacral) division

Dual Innervation

Most organs have _________: both autonomic divisions innervate the same organs but usually cause opposite effects.

Norepinephrine (NE)

Most sympathetic postganglionic neurons secrete _________.

All spinal nerves and their branches

Of the 31 pairs of spinal nerves, which carry somatic motor neurons? a) All spinal nerves and their branches (rami) (e.g. intercostal, phrenic, median, radial, ulnar, femoral, and sciatic nerves) b) All intercostal spinal nerves c) All phrenic spinal nerves d) All median spinal nerves

Trigeminal, Facial, Glossopharyngeal, Vagus

Of the cranial nerves we've discussed, which carry somatic motor neurons? a) Olfactory and Optic b) Trigeminal, Facial, Glossopharyngeal, Vagus c) Vestibuocochlear d) Oculomotor

Pupil

Opening in iris. Normal _________ size results from a balance between sympathetic and parasympathetic effects. Parasympathetic effects are protective; can override sympathetic effects.

Glossopharyngeal (IX) Nerves

Parasympathetic neurons carried in this nerve provides parasympathetic innervation of the parotid gland via the otic ganglion. It also provides parasympathetic innervation to the mucous glands.

Oculomotor (III) Nerves

Parasympathetic neurons carried in this nerve to smooth muscles in the iris; constrict the pupils; cause lenses to bulge for close vision.

Facial (VII) Nerves

Parasympathetic neurons carried in this nerve to supply many of the glands of the head and neck, including the submandibular, sublingual, nasal, palatine, lacrimal and pharyngeal gland.

Peripheral Nervous System (PNS)

Somatic and autonomic nervous systems are part of the _________, under the motor (efferent) division. Both somatic and automatic nervous systems are part of the motor divisions of the _________. Systems differ in: 1. Effector (target organs). 2. Efferent pathways. 3. Neurotransmitters and their effects.

Skeletal Muscles

Somatic motor neurons innervate _________. ("soma" = body; voluntary movement of body)

Collateral (Prevertebral) Ganglia

Some preganglionic neurons pass through the sympathetic trunk. Synapse in __________. __________ are sympathetic ganglia which lie between the paravertebral ganglia and the target organ. Help form splanchnic.

Splanchnic Nerves

Some preganglionic neurons pass through the sympathetic trunk. Synapse in collateral (prevertebral) ganglia. Help form _________ which innervate organs in the abdomen and pelvis.

Effectors

Targets of the motor neurons.

Sympathetic, Parasympathetic

_________ and _________ neurons differ anatomically in several ways: 1. Sites in CNS from which preganglionic fibers emerge. 2. Length of preganglionic and postganglionic fibers. 3. Location of autonomic ganglia (close to or far from CNS)

Vagus (X) Nerves

___________ carry 90% of all parasympathetic neurons to heart and digestive tract. Longest nerve of the autonomic nervous system in the human body. Sends parasympathetic output to the viscera, especially the intestines.

Sympathetic Trunk

_________s run close to and parallel to the spinal cord on both sides. Most preganglionic neurons synapse immediately in the _________ with their postganglionic neurons. Some preganglionic neurons ascend or descend the ____________ before synapsing. Some preganglionic neurons pass through the __________.