BSC 181 Exam 6 Review

ISU Wargo Spring 2026

What structures are associated with the peripheral nervous system?

Sensory receptors, peripheral nerves, and associated ganglia, and the efferent motor endings.

What are the layers that surround a nerve?

Endoneurium, perineurium, and epineurium.

Endoneurium

Loose connective tissue that encloses axons and their myelin sheaths

Perineurium

Coarse connective tissue that bundles fibers into fascicles.

Epineurium

Tough fibrous sheath around a nerve.

What are the classifications of nerves based on stimulus type?

Mixed nerves (sensory + motor), sensory afferent, and motor efferent

What are the classifications of nerves based on location?

Afferernt means toward the body (sensory) and efferent means away from the body (motor).

What are the classifications of nerves based on receptor structure?

The afferent nerve fibers contain cell bodies of sensory neurons (dorsal root ganglia), and the efferent nerve fibers contain autonomic motor neurons (autonomic ganglia).

Compare phasic and tonic receptors.

Phasic (fast-adapting) receptors signal the beginning or end of a stimulus, receptors for pressure, touch, and smell (short term).

Tonic (slow) receptors are mostly proprioceptors or not at all: nociceptors (don’t stop until the input stops).

Which fibers are associated with pain?

(ERMMM CIRCLE BACK)

How does referred pain work?

Pain from 1 body region is perceived from a different region. Visceral and somatic pain fibers travel in the same nerves, so the brain assumes stimulus from a common somatic region (Male heart attack referred pain to the left arm, female left jaw pain).

How are peripheral neurons regenerated?

Axon becomes fragmented, macrophage clean up, axon sprouts (regeneration tube) formed by Schwann cells, and then the axon regenerates and a new myelin sheath forms

How are central neurons regenerated?

Most do not regenerate, CNS oligodendrocytes (inhibiting protein), astrocytes at the injury site to form the scar tissue that blocks axonal regrowth.

Cranial nerve I

Olfactory nerves associated with smell

Where are the receptors for Cranial Nerve I?

They are sensory only in the nasal mucosa.

Where is the olfaction perceived in the brain?

Olfactory epithelium in the nasal cavity. They pass through the cribriform plate to the roof of the nasal cavity to the olfactory bulb (order of the neurons). The olfactory tract runs beneath the frontal lobe to the primary olfactory cortex.

How is Cranial Nerve I tested?

Have them smell something pleasant or something stinky.

Cranial Nerve II

Optic Nerves that are associated with vision

Where are the receptors for Cranial Nerve II?

Receptors are in the retina and are also purely sensory (I and II are purely sensory).

What is the tract/pathway to the brain for Cranial nerve II?

Photoreceptors in the retina, passing through the optic canal/nerve, form a converse and partial crossover (optic chiasma), optic tracts to the thalamus, and optic radiation fibers run to the visual cortex in the occipital lobe.

What is the optic chiasm?

x-shaped structure at the base of the brain (hypothalamus) where the 2 optic nerves meet.

How is Cranial nerve II tested?

Acuity (Snellen chart), peripheral vision test, ophthalmoscopic evaluation (view optic disc and blood vessels).

Cranial Nerve III