1A. What you will draw
The peripheral nervous system carries signals to and from the CNS. The autonomic nervous system handles involuntary control. Today you'll draw a generic reflex arc, then the sympathetic vs parasympathetic outflow.
BIO 304 . WEEK 5 . TUESDAY . LAB WORKBOOK
PNS and Autonomic Nervous System
Cranial and spinal nerves, reflex arcs, and the sympathetic vs parasympathetic divisions.
Print this page. You will draw your own diagrams from the directions below, then hand-label the structures listed. Drawing by hand is the integrity mechanism for this course.
Part 1 of 2
Anatomy Lab
Box A. The reflex arc (5 components)
Directions
- Use the patellar (knee-jerk) reflex as your example. Draw a leg with the patellar tendon being tapped by a reflex hammer.
- Component 1: Receptor. Draw a muscle spindle in the quadriceps. Label.
- Component 2: Sensory (afferent) neuron. Draw an axon going from the muscle spindle up to the spinal cord, entering the dorsal horn.
- Component 3: Integration center. Inside the spinal cord, show a single synapse (this is a monosynaptic reflex). Label.
- Component 4: Motor (efferent) neuron. Draw an axon leaving the ventral horn and going back down to the quadriceps.
- Component 5: Effector. The quadriceps contracts, kicking the leg up. Label.
- Add arrows showing the direction of signal flow.
Draw here. Sketch by hand.
Box B. Sympathetic vs parasympathetic outflow
Directions
- Draw a side view of the spinal column.
- Sympathetic (thoracolumbar): show preganglionic fibers leaving the spinal cord from T1 through L2. Draw the sympathetic chain ganglia running parallel to the cord. Show short preganglionic fibers ending in chain ganglia, then long postganglionic fibers traveling to target organs.
- Parasympathetic (craniosacral): show preganglionic fibers leaving from the brainstem (via cranial nerves III, VII, IX, and especially X, the vagus) AND from S2-S4 (sacral). Show long preganglionic fibers traveling to ganglia near or on the target organs, then very short postganglionic fibers.
- Label two target organs (e.g., heart, lungs, gut) and note opposing effects: sympathetic increases heart rate, parasympathetic decreases it.
Draw here. Sketch by hand.
1C. Structures to label (13)
After you finish each drawing, label every structure below directly on your sketch.
- Receptor (muscle spindle)
- Sensory neuron (afferent)
- Dorsal horn
- Integration center (spinal cord synapse)
- Motor neuron (efferent)
- Ventral horn
- Effector (skeletal muscle)
- Sympathetic chain ganglia
- Preganglionic fiber (sympathetic)
- Postganglionic fiber (sympathetic)
- Preganglionic fiber (parasympathetic)
- Postganglionic fiber (parasympathetic)
- Vagus nerve (CN X)
Part 2 of 2
Physiology Lab
2A. Sympathetic vs parasympathetic comparison
Fill in the table comparing the two autonomic divisions. Then answer the two follow-up questions.
| Property | Sympathetic | Parasympathetic |
|---|---|---|
| Origin in CNS (thoracolumbar / craniosacral) | ||
| Preganglionic fiber length (short / long) | ||
| Effect on heart rate | ||
| Effect on pupil diameter | ||
| Effect on GI motility | ||
| Effect on bronchial smooth muscle | ||
| Effect on sweat glands |
Why are sympathetic effects more widespread (affecting many organs at once) while parasympathetic effects are more targeted? Justify using preganglionic fiber length and ganglion location.
Both divisions release acetylcholine at preganglionic synapses. At postganglionic targets, sympathetic typically releases norepinephrine and parasympathetic releases acetylcholine. Predict what beta-blocker drugs (which block norepinephrine receptors in the heart) do to heart rate, and why.
2B. Synthesis questions
Answer each in 2 to 4 sentences. Use the language from this week's lecture and your drawings as evidence.
1. A person is startled by a loud noise. List 5 specific sympathetic effects they experience over the next 10 seconds. For each, identify the target organ and the response.
2. After eating a large meal, parasympathetic activity dominates. Predict at least 3 specific physiological changes in this state and explain how 'rest and digest' is the appropriate metabolic context.
3. A patient takes an anticholinergic medication for an overactive bladder. Predict the side effects this drug will produce across other organs that also respond to acetylcholine. Why are dry mouth, blurred vision, and constipation common with these drugs?
3. What to submit
Complete both the Anatomy Lab (your own drawings, hand-labeled, plus the structures list) and the Physiology Lab (activity and synthesis questions). Photograph or scan every page and upload to Canvas before the deadline listed on the schedule. Hand-drawn, hand-labeled work is the integrity mechanism for this course. Typed or AI-generated diagrams are not accepted.