Lecture 16: The Autonomic Nervous System M/O Chapter 18 78. Contrast the anatomy of the parasympathetic and sympathetic nervous systems. 79. Discuss the two divisions of the ANS and the general physiological roles of each. 80. Describe examples of specific effectors dually innervated by the two branches of the ANS and explain how each branch influences function in a given effector.

Introduction to the Autonomic Nervous System

The autonomic NS is a subdivision of the PNS and consists of primarily visceral motor fibers. (Technically, the ANS also includes visceral sensory, but these fibers do not have a clear anatomic structure, so they are more vague and complex. We will leave them that way.) 1. Effectors: Smooth muscle, cardiac muscle, glands 2. Function: Takes care of all VITAL physiological processes A. Regulates body temperature, heart rate, respiratory rate B. Coordinates digestion, excretion, reproduction 3. Does not require consciousness (hence, visceral!)

Mapping Efferent Pathways 1. 2. 3. 4. 5.

Sensory info enters into a spinal nerve from some pathway. Sensory cell bodies (both VS and SS) are found in the dorsal root ganglion. The sensory neurons synapse in the CNS...somewhere. Interneurons can pass the information around in the CNS. Depending on the effector, the path will either be: A. Somatic motor or B. Visceral motor i. Sympathetic or ii. Parasympathetic

Comparing VM and SM

1. Both VM and SM exit the spinal cord via the ventral root. 2. However, SM cell bodies are found in the anterior gray horn. VM cell bodies are found in the lateral gray horns of the spinal cord at levels T1-L2 and in the lateral area of S2-S4... and in various places . 3. Also, SM neurons travel ALL the way from the spinal cord, directly to the skeletal muscle they innervate. VM neurons reach their effectors in a 2 neuron chain that includes an autonomic ganglion. 4. There is ONE type of SM pathway...but there are two distinctive types of VM pathways. These pathways are distinguished by ANATOMICAL FEATURES.

Comparing VM Pathways

1. Both sympathetic and parasympathetic cell bodies are found in the lateral gray horn (or at least in the lateral area of the gray matter in the spinal cord). A. This neuron is considered the preganglionic neuron. B. Preganglionic neurons are myelinated. 2. Preganglionic fibers follow the same path as SM neurons A. Out the ventral root B. Into the spinal nerve 3. The preganglionic neurons synapse on ganglionic neurons whose cell bodies are found in autonomic ganglia somewhere in the PNS. A. The ganglionic axon is not myelinated. B. The ganglionic neuron innervates the effectors (smooth muscle, cardiac muscle, glands)

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Mapping the Sympathetic NS onto the spinal cord 1. 2. 3. 4.

All autonomic neruons have a preganglionic cell body in the lateral grey horn (or nearby). Sympathetic neurons travel out through the ventral root and into the spinal nerve. Here they pass into a special autonomic pathway called the rami communicantes. Almost immediately after branching off the spinal nerve, they synapse with the ganglionic neuron. A. Preganglionic neurons are really really SHORT. B. This means the sympathetic ganglia are very close to the spinal cord. C. This means that ganglionic neurons are very very LONG. 5. The ganglionic fiber then can head back into the ventral ramus and head out...

Mapping the Parasympathetic NS onto the spinal cord

1. All autonomic neruons have a preganglionic cell body in the lateral grey horn (or nearby). 2. Parasympathetic neurons travel out through the ventral root and into the spinal nerve. 3. Here they go through the ventral ramus and out into the body. A. Preganglionic neurons are really really LONG. B. Usually they reach almost all the way to the effector! 4. Parasympathetic ganglia are very close to the effector and are often embedded IN the effector. A. This means that ganglionic neurons are very very SHORT. B. Sometimes they are even embedded IN the wall of the effector. 5. Most preganglionic parasympathetic fibers (75-80%- MO pg 545) run through the vagus nerve (cranial nerve X).

Comparing Sympathatic and Parasympathetic NS Parasympathetic (aka craniosacral)

Sympathetic

Rest and digest...feed and breed Brainstem (cranial nerves 3,7, 9 and 10)

Fight, fright, flight! Lateral gray horns in T1-L2 spinal cord

Location of ganglionic neuron’s cell body

Lateral gray matter in S2-S4 (spinal cord) Intramural ganglion: In the wall of the effector

Chain ganglia (aka sympathetic trunk ganglia) are found next to the spinal cord.

Length of preganglionic axon Length of postganglionic axon Location of ganglia

Cranial ganglia (associated with cranial nerves) Long Short Very close to the effector

Collateral ganglia (aka prevertebral ganglia); found anterior to the spine Short Long Very close to the spinal cord

Parasympathetic effect

Sympathetic effect

Decrease Decrease Constricted Increase

INCREASE! INCREASE! Dilated (to let in more light) Decrease

Function Location of preganglionic neuron’s cell body

Heart rate Breathing rate Pupil size Digestive processes

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Reproduction

Arousal

Climax

Lab 16: The Human Skull Reading: M&O Ch. 7 The skull is extraordinarily beautiful and extraordinarily complex. The best way to learn the bones is to read the text with a skull in hand. DO NOT simply follow the list and identify bones from pictures. A tremendous amount of guidance lies in the language of your textbook and should be taken advantage of. You are responsible for most of the bolded terms in the assigned pages. A summary list is appended below. Terms not on the list below can be crossed out in pencil in your textbook…I recommend you do this before you come to lab. Work with a partner. One of you can read and one of you can hold the skull. Start on M&O pg. 175 and with an intact skull. As you work through the assigned pages, refer to individual isolated bones when necessary. You need to be able to recognize the bones from the outside and from the inside (i.e., the surfaces facing the brain, etc.). You’ll know you’re in good shape when you can identify all the bones and identify all the cranial foramina without referring to the text. Don’t worry too much about what passes through each foramen yet…we’ll come back to this next lab!!

Required Terms

1. skull A. cranial bones (8) B. cranium C. facial bones D. cranial cavity E. sutures F. sutural (or Wormian!) bones 2. frontal bone A. supraorbital foramen B. glabella C. frontal sinuses 3. parietal bones 4. temporal bones A. internal auditory canal B. mastoid process C. styloid process D. stylomastoid foramen E. carotid canal F. zygomatic process G. zygomatic arch H. mandibular fossa I. external auditory canal 5. occipital bone A. foramen magnum B. occipital condyles C. hypoglossal canal D. external occipital protuberance (inion) E. superior and inferior nuchal lines F. jugular foramen 6. zygomatic bones A. temporal process

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B. zygomatic arch 7. sphenoid bone A. body B. sella turcica C. optic groove D. optic foramen E. foramen rotundum F. foramen ovale G. foramen spinosum H. pterygoid processes 8. ethmoid bone A. crista galli B. cribriform plate C. cribriform foramina D. superior nasal conchae E. middle nasal conchae F. perpendicular plate 9. lacrimal bones A. lacrimal groove 10. 11. 12. 13.

nasal bones vomer inferior nasal conchae palatine bones

14. maxillae (maxillary bones) A. infraorbital foramen B. alveolar processes C. maxillary sinuses D. zygomatic processes 15. mandible A. ramus B. angle C. alveolar process D. temporomandibular joint E. coronoid process F. mandibular notch 16. paranasal sinuses 17. auditory ossicles A. malleus B. incus C. stapes 18. hyoid bone

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External Brain 16: Autonomic NS 78. Contrast the anatomy of the parasympathetic and sympathetic nervous systems. 79. Discuss the two divisions of the ANS and the general physiological roles of each. 80. Describe examples of specific effectors dually innervated by the two branches of the ANS and explain how each branch influences function in a given effector.

Study Questions 1. 2. 3. 4.

What are the four major regions of the temporal bone? What passes through the holes in the cribriform plate? What passes through the foramen magnum? Which two bones join to form the zygomatic arch?

5. Which two bones articulate to form the jaw joint? 6. Which bone contains the middle ear cavity and the inner ear? 7. Which seven bones can be seen inside the orbit? 8. Which two bones contribute to the nasal septum? 9. Where does the eardrum sit? 10. What sits in the sella turcica? 11. What is the evolutionary advantage of an ANS that has a 2 neuron chain, as opposed to the somatic NS, where motor neurons travel all the way from the spinal cord to their effectors? 12. Why might the lateral horn of gray matter be absent?

Prepping for Cranial Nerves...what passes through these holes? (see Table 7.1) Skull “hole” cribriform foramina optic foramen superior orbital fissure foramen rotundum foramen ovale foramen lacerum carotid canal internal auditory meatus stylomastoid foramen jugular foramen hypoglossal canal

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