Chapter 16: The Autonomic Nervous System & Higher-Order Functions

Homeostasis Responds to subconscious visceral sensations Excites or inhibits smooth muscle, cardiac muscle, or glands Includes Autonomic sensory neurons Integrating centers in CNS Autonomic motor neurons Enteric nervous system (ENS)

Somatic nervous system Autonomic nervous system Figure 16-1 The Organization of the Somatic and Autonomic Nervous Systems. Upper motor neurons in primary motor cortex Visceral motor nuclei in hypothalamus Brain Brain Somatic motor nuclei of brain stem Preganglionic neuron Visceral Effectors Smooth muscle Autonomic nuclei in brain stem Autonomic ganglia Glands Skeletal muscle Lower motor neurons Spinal cord Cardiac muscle Ganglionic neurons Spinal cord Adipocytes Somatic motor nuclei of spinal cord Autonomic nuclei in spinal cord Preganglionic neuron Skeletal muscle a Somatic nervous system b Autonomic nervous system

Figure 16-10 A Comparison of Somatic and Autonomic Function. Central Nervous System Cerebral cortex Limbic system Thalamus Hypothalamus Somatic sensory Visceral sensory Relay and processing centers in brain stem Somatic reflexes Long reflexes Lower motor neuron Preganglionic neuron Peripheral Nervous System Sensory pathways SNS ANS Short reflexes Ganglionic neuron Skeletal muscles Sensory receptors Visceral effectors

Table 16-5 A Comparison of the ANS and SNS.

Figure 16-2 Overview of the Autonomic Nervous System.

Anatomical Components Preganglionic neuron Cell body is in brain or spinal cord Axons exits CNS as part of a cranial nerve or spinal nerve Axon is type B fiber Postganglionic neuron Lies entirely outside of CNS Cell body & dendrites located in autonomic ganglion Axon is type C fiber Terminates in visceral effector

Figure 16-2 Overview of the Autonomic Nervous System (Part 1 of 2). Sympathetic Division (Thoracolumbar) Preganglionic Neurons Preganglionic neurons are located in the lateral gray horns of spinal segments T1–L2. Ganglia Ganglia are located near the spinal cord. Preganglionic fibers release acetylcholine (Ach), stimulating ganglionic neurons. Target Organs Most postganglionic fibers release norepinephrine (NE) at neuroeffector junctions. Sympathetic activation “Fight or flight” response KEY Preganglionic fibers Postganglionic fibers

Sympathetic Ganglia Sympathetic chain ganglia Collateral ganglia Preganglionic neurons Ganglionic neurons KEY Gray ramus Spinal nerve Preganglionic neuron Autonomic ganglion of left sympathetic chain Sympathetic nerve (postganglionic fibers) Innervates visceral organs in thoracic cavity by sympathetic nerves Note: Both innervation patterns occur on each side of the body. Autonomic ganglion of right sympathetic chain Innervates visceral effectors by spinal nerves White ramus Ganglionic neuron SYMPATHETIC CHAIN GANGLIA a c b White ramus COLLATERAL GANGLIA Preganglionic fibers THE ADRENAL MEDULLAE Lateral gray horn Splanchnic nerve (preganglionic fibers) Postganglionic fibers Collateral ganglion Innervates visceral organs in abdominopelvic cavity Endocrine cells (specialized ganglionic neurons) Adrenal medullae Secretes neurotransmitters into general circulation Sympathetic chain ganglia Aka vertebral chain ganglia or paravertebral ganglia Collateral ganglia Aka prevertebral ganglia Adrenal medullae Known as modified sympathetic ganglion Involves chromaffin cells

Figure 16-4 The Distribution of Sympathetic Innervation. Eye Pons Salivary glands Sympathetic nerves Superior Middle Cervical sympathetic ganglia Heart Inferior Cardiac and pulmonary plexuses T1 T1 Greater splanchnic nerve Gray rami to spinal nerves T2 T2 T3 T3 Lung Celiac ganglion T4 T4 T5 T5 Superior mesenteric ganglion T6 T6 Liver and gallbladder T7 T7 T8 T8 Stomach T9 T9 Lesser splanchnic nerve T10 T10 Spleen T11 T11 Pancreas T12 T12 Large intestine Postganglionic fibers to spinal nerves (innervating skin, blood vessels, sweat glands, arrector pili muscles, adipose tissue) L1 L1 L2 L2 Lumbar splanchnic nerves Inferior mesenteric ganglion Small intestine L3 L3 L4 L4 L5 L5 Adrenal medulla S1 S1 S2 S2 Sacral splanchnic nerves S3 Sympathetic chain ganglia S4 Kidney S3 S4 S5 S5 Spinal cord KEY Coccygeal ganglia (Co1) fused together (ganglion impar) Preganglionic fibers Postganglionic fibers Uterus Ovary Penis Scrotum Urinary bladder

Figure 16-2 Overview of the Autonomic Nervous System (Part 2 of 2). Parasympathetic Division (Craniosacral) Preganglionic Neurons Preganglionic neurons in brain stem and in lateral portion of anterior gray horns of S2–S4. Ganglia Ganglia are in or near the target organ. Preganglionic fibers release acetylcholine (Ach), stimulating ganglionic neurons. Target Organs All postganglionic fibers release Ach at neuroeffector junctions. Parasympathetic stimulation “Rest and digest” response KEY Preganglionic fibers Postganglionic fibers

Parasympathetic Ganglia Terminal ganglia Aka intramural glanglia Close to or within wall of visceral organ

Figure 16-6 The Distribution of Parasympathetic Innervation. Pterygopalatine ganglion N III Lacrimal gland Eye Pons Ciliary ganglion N VII Salivary glands Submandibular ganglion N IX Otic ganglion N X (Vagus) Heart Lungs Autonomic plexuses (see Figure 16-8) Liver and gallbladder Stomach Spleen Pancreas Large intestine Pelvic nerves Small intestine Rectum Spinal cord S2 Kidney S3 S4 KEY Preganglionic fibers Postganglionic fibers Uterus Ovary Penis Scrotum Urinary bladder

Figure 16-8 The Autonomic Plexuses and Ganglia. Aortic arch Right vagus nerve Trachea Autonomic Plexuses and Ganglia Left vagus nerve Cardiac plexus Thoracic spinal nerves Pulmonary plexus Esophagus Thoracic sympathetic chain ganglia Esophageal plexus Splanchnic nerves Celiac plexus and ganglion Superior mesenteric ganglion Diaphragm Superior mesenteric artery Inferior mesenteric plexus and ganglia Inferior mesenteric artery Hypogastric plexus Pelvic sympathetic chain

Neurotransmitters & Receptors Cholinergic Adrenergic Neurons release Ach Includes All preganglionic neurons All parasympathetic postganglionic neurons Sympathetic postganglionic neurons to most sweat glands Receptors Nicotinic Excitatory Muscarinic May be excitatory or inhibitory depending on cell Neurons release NE Includes most sympathetic postganglionic neurons Receptors Alpha 1 Alpha 2 Beta 1 Beta 2

Table 16-1 Adrenergic and Cholinergic Receptors of the ANS.

Sympathetic Parasympathetic CNS Preganglionic neuron PNS Figure 16-7 Summary: The Anatomical Differences between the Sympathetic and Parasympathetic Divisions. Sympathetic Parasympathetic CNS Preganglionic neuron PNS Preganglionic fiber KEY Sympathetic ganglion Neurotransmitters Acetylcholine Norepinephrine or Epinephrine Ganglionic neurons Bloodstream Postganglionic fiber Parasympathetic ganglion TARGET

Table 16-2 A Structural Comparison of the Sympathetic and Parasympathetic Divisions of the ANS.

Responses Sympathetic Parasympathetic “Fight or Flight” “E” situations Exercise Emergency Excitement Embarrassment Includes Pupils dilate HR, force of contraction, & BP all increase Airways dilate Some blood vessels vasodilate & some vasoconstrict Stimulates glycogenolysis & lipolysis “Rest & Digest” Supports functions that conserve & restore body energy SLUDD Salivation Lacrimation Urination Digestion Defecation Also 3 “D”s Decreases HR Decreases diameter of airways (bronchoconstriction) Decreases diameter of pupils (constriction)

Table 16-3 A Functional Comparison of the Sympathetic and Parasympathetic Divisions of the ANS (Part 1 of 4).

Table 16-3 A Functional Comparison of the Sympathetic and Parasympathetic Divisions of the ANS (Part 2 of 4).

Table 16-3 A Functional Comparison of the Sympathetic and Parasympathetic Divisions of the ANS (Part 3 of 4).

Table 16-3 A Functional Comparison of the Sympathetic and Parasympathetic Divisions of the ANS (Part 4 of 4).

Figure 16-9 Visceral Reflexes. Receptors in peripheral tissue Afferent (sensory) fibers CENTRAL NERVOUS SYSTEM Stimulus Long reflex Short reflex Processing center in spinal cord Peripheral effector Response Autonomic ganglion (sympathetic or parasympathetic) Postganglionic neuron Preganglionic neuron

Table 16-4 Representative Visceral Reflexes (Part 1 of 2).

Table 16-4 Representative Visceral Reflexes (Part 2 of 2).

Figure 16-14 diagrams the functional relationships between the nervous system and other body systems we have studied so far. SYSTEM INTEGRATOR Body System Nervous System Nervous System Body System Provides sensations of touch, pressure, pain, vibration, and temperature; hair provides some protection and insulation for skull and brain; protects peripheral nerves Controls contraction of arrector pili muscles and secretion of sweat glands Integumentary Integumentary Page 174 Provides calcium ions for neural function; protects brain and spinal cord Controls skeletal muscle contractions that results in bone thickening and maintenance and determine bone position Skeletal Skeletal Page 285 Facial muscles express emotional state; intrinsic laryngeal muscles permit communication; muscle spindles provide proprioceptive sensations Controls skeletal muscle contractions; coordinates respiratory and cardiovascular activities Muscular Muscular Page 380 The Nervous System The nervous system is closely integrated with other body systems. Every moment of your life, billions of neurons in your nervous system are exchanging information across trillions of synapses and performing the most complex integrative functions in the body. As part of this process, the nervous system monitors all other systems and issues commands that adjust their activities. However, the significance and impact of these commands varies greatly from one system to another. The normal functions of the muscular system, for example, simply cannot be performed without instructions from the nervous system. By contrast, the cardiovascular system is relatively independent—the nervous system merely coordinates and adjusts cardiovascular activities to meet the circulatory demands of other systems. In the final analysis, the nervous system is like the conductor of an orchestra, directing the rhythm and balancing the performances of each section to produce a symphony, instead of simply a very loud noise. Endocrine Page 647 Cardiovascular Page 776 Lymphatic Page 824 Respiratory Page 874 Digestive Page 929 Urinary Page 1010 Reproductive Page 1090