Chapter 14 Autonomic Nervous System

Preganglionic axons can ascend or descend

and synapses with a postganglionic neuron in a different chain ganglion

beta-1 receptors

plasma membranes of cardiac muscle cells, certain kidney cells, and adipose cells

beta-2 receptors

plasma membranes of smooth muscle cells of airways of respiratory tract (bronchioles), wall of urinary bladder, sletal muscle fibers, and cells found in liver, pancreas, and salivary glands.

What are the two divisions within the nervous system

1) sympathetic and 2) parasympathetic

Summary of Nervous System Control of Homeostasis

1. Hypothalamus and brainstem reticular formation; actions carried out by the two divisions of ANS 2. Autonomic centers in the reticular formation in brainstem that connect hypothalamus; contain neurons that control activity of preganglionic sympathetic and parasympathetic neurons

summarize visceral reflex arcs

1. Sensory signals... from the viscera and skin are sent by afferent sensory neurons to the brain or spinal cord 2. Integration... the stimuli are integrated by the CNS 3. Motor impulses... from the CNS are sent via efferent sensory neurons in cranial and spinal nerves to autonomic ganglia 4. Autonomic ganglia... send the impulses via other efferent neurons to various target organs, where they trigger a motor response in the target cells

Compare the Somatic and Autonomic Nervous Systems

1. Somatic motor division motor neuron, innervate skeletal muscle, and is voluntary. 2. Autonomic motor division motor neurons innervate viscera muscle, im not sure muscle, and heart. and is involuntary.

Visceral Reflex Arcs

ANS manages vital involuntary process sensory stimulus leads to a predictable motor responseANS manages vital involuntary process sensory stimulus leads to a predictable motor response

Effects on cellular metabolism: To assist with this higher energy demand norepinephrine has the following three effects:

During times of sympathetic activation, nearly all cells, especially skeletal muscle, require higher amounts of ATP; to meet this higher energy demand NE has three effects: a. beta- 3 receptors adipocytes; breakdown of lipids; releases free fatty acids into bloodstream. b. Beta-2 receptors liver cells; release of glucose from other resources c. NE binds Beta-2 receptors on cells of pancreas; release of hormone glucagon; increases blood glucose levels

Epinephrine (adrenalin)

Epi abbreviation

Parasympathetic nervous system

Preganglionic axons are located in several cranial nerves in brainstem and sacral region of spinal cord, Craniosacral division while postganglionic axons are i. Craniosacral division Preganglionic cell bodies are located within the nuclei of several cranial nerves (CN III, VII, IX, X) and sacral (S2-S4) region. ii. Cell bodies of postganglionic neurons are usually located near the target organ in post ganglia. iii. "rest and digest" division: role in digestion and in maintaining body's homeostasis at rest

White (myelinated) ramus communicans

Preganglionic axons separate from anterior ramus of spinal nerve to form a small nerve called white (myelinated) rami communicans; leads to postganglionic cell bodies in sympathetic chain ganglion

Lateral horns of thoracic and lumbar spinal cord

Preganglionic neurons from lateral horns of thoracic and lumbar spinal cord; exit via anterior root

Effects of the sympathetic nervous system on cells of the adrenal medulla

a. ACh is released from preganglionic neurons that then bind to nicotinic receptors on the adrenal medulla cells. b. ACh stimulates the medullary cells to release NE and Epinephrine into the bloodstream. In this case these are considered hormones rather than neurotransmitters. c. Hormones act as long-distance chemical messengers between endocrine and sympathetic nervous system (regulate homeostasis).

Summarize the Effects of the sympathetic nervous system on Smooth muscle cells

a. Constriction of blood vessels serving the digestive, urinary, and integumentary system norepinephrine binds to alpha-1 receptors, which decreases blood flow to these organs. b. Dilation of the bronchioles norepinephrine binds to beta-2 receptors, which increases the amount of oxygen that can be inhaled with each breath. c. Dilation of blood vessels serving the skeletal and cardiac muscle norepinephrine binds to beta-2 receptors, which increase the blood flow. d. Contraction of urinary and digestive sphincters norepinephrine binds to b-2 and b-3 receptors which contracts them. e. Relaxation of the smooth muscle of the digestive tract norepinephrine binds to beta-2 which slows digestion during increases physical activity. f. Dilation of the pupils norepinephrine binds to alpha-1 receptors which causes the pupil to allow more light into eye. g. Constriction of blood vessels serving most exocrine glands norepinephrine binds to beta-2 which decreases the secretion of saliva

effects of parasympathetic nervous system on smooth muscle cells

a. Constriction of the pupil CN III: reduces amount of light allowed into the eye. b. Accommodation of the lens for near vision: CN III and contraction of ciliary muscle; changes lens to a more rounded shape. c. Constriction of the bronchioles CN X- reduces air flow through bronchioles d. Contraction of the smooth muscle lining the digestive tract CN X- produces rhythmic contractions called peristalsis; propels food through digestive tract e. Relaxation of digestive and urinary sphincters CN X and sacral nerves; promotes urination and defecation f. Engorgement of the penis or clitoris Side effects of anticholinergic drugs: either block Ach release or Ach receptors. Urinary retention, constipation, and dry mouth are causes of this.

(CN X) Vagus

a. innervate most thoracic and abdominal viscera. b. Branches of the vagus nerves contribute to the cardiac, pulmonary, and esophageal plexuses

Describe the balance between the parasympathetic and sympathetic nervous systems

actions of parasympathetic division directly antagonize those of sympathetic division; maintain a delicate balance to ensure that homeostasis is preserved

beta-3 receptors

adipose cells and smooth muscle cells in walls of digestive tract

beta-2 agonists

asthmatics

Homeostasis

balance between two systems

Adrenergic receptors

bind to epinephrine and norepinephrine; two major types: alpha and beta.

Dual innervation

both divisions innervate many of same organs where their actions antagonize one another.

Parasympathetic Neurotransmitters and Receptors:

both pre and postganglionic parasympathetic neurons release Ach at their synapses, and the effect is generally Excitatory Cholinergic receptors

Postganglionic neuron; neurotransmitter

cell body resides in autonomic ganglion in PNS; axons travel to target cells; trigger specific changes (inhibitory or excitatory responses) Neurotransmitters: acetylcholine or norephinephrine

(CN III) Oculomotor

ciliary body to control iris and lens

(CN VII) facial

control lacrimal glands AND submandibular and sublingual salivary glands

Pharmacology and sympathetic nervous system receptors

different subtypes of sympathetic nervous system receptors have provided targets for medication therapy for many different disease states, including asthma nad hypertension

beta-blockers

high blood pressure

Sympathetic nervous system

i. Preganglionic axons are: thoracic and lumbar and spinal cord while Postganglionic axons are: brainstem or sacral spinal cord ii. Thoracolumbar division (T1-L2); Preganglionic cell bodies originate iii. Sympathetic ganglia located: near spinal cord, where preganglionic axons synapse with postganglionic neuron cell bodies iv. "fight" or flight" division of ANS; prepares body for emergency situations; exercise; emotions

Pregangionic neuron; neurotransmitter

initial efferent neuron; cell body resides within CNS Neurotransmitter: acethylcholine

Muscarinic receptors

located in membranes of all parasympathetic target cells.

Nicotinic receptors

located in membranes of all postganglionic neurons.

Sacral nerves

make up the pelvic nerve-component of this division. This subdivision supplies the last segment of the large intestine, the urinary bladder, and the reproductive organs.

Norepinephrine (noradrenalin)

most frequently utilized neurotransmitter released from synapses between postganglionic axons and target cells.

Sympathetic chain ganglia

most of postganglionic cell bodies found here; "chainlike" appearance; both sides of vertebral column; run parallel

autonomic nerve plexus:

neural networks that are formed by complex interconnections between neurons from the sympathetic and parasympathetic divisions of the autonomic nervous system

Acetylcholine (ACh)

neurotransmitter used in excitatory synapses between sympathetic preganglionic axons and postganglionic neurons; transmit action potentials to target cell. Least common

alpha-2 receptors

on plasma membranes of preganglionic sympathetic neurons instead of peripheral target cells. Usually, AP in a preganglionic neuron leads to Ach release; stimulates postganglionic neuron. When norepinephrine binds to alpha-2 receptors, axon terminal is hyperpolarized; slows or cancels AP. Component of a negative feedback loop.

(CN IX) glossopharyngeal

parotid salivary gland

Preganglionic axons can synapse in

postganglionic neuron in sympathetic chain ganglion

Effects of the sympathetic nervous sytem on secretion from sweat glands

postganglionic sympathetic neurons secrete Ach which binds to muscarinic receptors. Negative feedback.

Splanchnic nerves:

preganglionic axons that synapse with collateral ganglia near organs of abdominopelvic cavity

Autonomic tone

refers to the fact that neither division is ever completely shut down; constant amount of activity from each division. Sympathetic tone- dominates in blood vessels; keeps them partially constricted. Parasympathetic tone- dominates in heart; average of 72 beats per minute.

Preganglionic

short and myelinated

alpha-1 receptors

smooth muscle cell membranes of blood vessels in skin, GI tract, and kidneys, arrector pili muscles in dermis, will cause vasoconstriction

Pelvic splanchnic nerves

some preganglionic neurons synapse with terminal ganglia in associated plexuses; most synapse in terminal ganglia within walls of target organs b. Terminal ganglia

Effects of the sympathetic nervous sytem on other cells:

sympathetic nervous system influences many other target cells, all with mission of maintaining homeostasis during increased physical or emotional stress. Enhances mental alertness by increasing neuron activity in brain. Temporarily increases tension generated by skeletal muscle; "adrenaline rush" increases bloods tendency to clot. Trigger contraction of arrector pili muscle which causes goosebumps, and ejaculation.

Collateral ganglia

synapses between preganglionic axon terminal with postganglionic neuron cell body; preganglionic axons pass through chain ganglia without forming synapses; located near target organ

Preganglionic axons can pass through the chain ganglia

synapses with a postganglionic neuron in a collateral ganglion

Antagonistic

systems will inhibit one another.

Effects of the parasympathetic nervous syetm on glandular epithelial cells

the parasympathetic division has little effect on sweat glands but does increase secretion production from other glands: a. CN VII b. CN VII and IX c. CN X

Postganglionic

unmyelinated

Gray (unmyelinated) ramus communicans

unmyelinated postganglionic axons that exit chain ganglia and reunite with spinal nerves

Effects of parasympathetic nervous sytem on cardiac muscle cells

vagus nerve (CN X) decreases heart rate and blood pressure