A&P Exam 3 - Peripheral Nervous System GENERAL

Both sympathetic and parasympathetics are part of the __ nervous system and have how many neurons in their pathway?

part of the autonomic nervous system, have 2 neurons in their pathway (one preganglionic, one postganglionic)

What are splanchnic nerves? What do they innervate? Do they have sensory or motor fibers?

Splanchnic nerves innervate the internal organs in the chest, abdomen, and pelvis. They have both sensory and motor fibers.

Only this type of splanchnic nerves carry parasympathetic (rest and digest) fibers

Pelvic splanchnic nerves

What are the differences in the two types of cholinergenic receptors? What neurotransmitter binds here? Are they in the parasympathetic or sympathetic nervous system?

Nicotinic = always excitatory, muscarinic = can be excitatory or inhibitory

Acetylcholine binds here. Found in both parasympathetic and sympathetic nervous system.

What are the two different types of adrenergic receptors? What neurotransmitter binds here? Are these in the sympathetic or parasympathetic nervous system?

Alpha type = smooth muscle contraction, vasoconstriction

Beta type = cardiac stimulation, smooth muscle relaxation, vasodilation

Norepinephrine/epinephrine binds here

Found in postganglionic parts of the parasympathetic nervous system

What four cranial nerves have parasympathetic functions?

CN III - oculomotor

CN VII - facial

CN IX - glossopharyngeal

CN X - vagus

Where on the spinal cord do sympathetics originate vs. parasympathetics?

Sympathetics = thoracolumbar origins

Parasympathetics = craniosacral origins

Which part of the nervous system has LONG PREganglionics and SHORT POSTganglionics?

Parasympathetic

Which part of the nervous system has SHORT PREganglionics and LONG POSTganglionics?

Sympathetic

What is “tone?" Describe sympathetic tone vs. parasympathetic tone.

Both sympathetics and parasympathetics are always activated at a consistent level at rest.

sympathetic = blood vessels

parasympathetic = heart and smooth muscle of digestive and urinary tracts

What is referred pain? What is an example?

Referred pain: autonomic aspects of pain crossfire/synapse/integrate with somatics slightly

Ex: pain in gall bladder can manifest as pain in the shoulder

What is the difference between exteroreceptors, interoreceptors, and proprioceptors?

Exteroreceptors - stimuli arising outside the body

Interoreceptors - stimuli arising inside the body

Proprioceptors - stimuli in skeletal muscles, tendons, ligaments, joints, and connective tissue

What are the differences between A-delta type fibers and C type fibers?

A-delta = fast-adapting (stop firing fairly quickly even if stimulus is still being applied), myelinated

C = slow-adapting (continue to fire longer after persistent stimulus is applied), unmyelinated

What is a free nerve ending? What are the different classifications of these, aka NONENCAPSULATED fibers

free nerve ending is an unspecialized, unencapsulated sensory nerve terminal that detects pain, temperature, mechanical pressure, and touch.

General - detect crude touch and pain

Merkel discs - light touch and texture, slow adapting

Hair root plexuses - light touch and movement on hair, fast adapting

What do Meissner’s (encapsulated) corpuscles do?

Rapid-adapting, detects light touch and low frequency vibrations

What do lamellar/Pacinian (encapsulated) corpuscles do?

Rapidly adapting, detects deep stretch, pressure, high frequency vibrations

What do Ruffini (encapsulated) corpuscles do?

Slow adapting, deep within skin, joint capsules, and ligaments

What do muscle spindles vs. golgi tendon organs do?

muscle spindle - in muscle, senses stretch and the speed of stretch

golgi tendon organ - in tendon, senses tension

Explain the muscle stretch reflex and the two efferent signals it sends

The muscle spindle senses stretch and sends an afferent signal to the spinal cord.

1. efferent - excitatory to contract quad

2. efferent - inhibitory to prevent antagonist contraction

Describe the tendon reflex and its two interneurons.

Tendon organs sense contraction, then send afferent signal to spinal cord

1. Interneuron - excitatory to antagonist

2. Interneuron - inhibitory to agonist

What five nerves innervate the eye?

Optic, oculomotor, trochlear, opthalmic (first branch of trigeminal), abducens

The three components of the surface anatomy of the eye are the palpebral fissure, iris, and conjunctiva. What do they each do?

Palpebral fissure - space between upper and lower eyelids

iris - colored portion around pupil

conjunctiva - thin clear mucus membrane covering front portion of eye

What does the lacrimal gland do?

Lubricates eye surface with lacrimal fluid aka tears. Moves down and across eye inwards towards nasolacrimal duct

What is the posterior cavity of the eye?

Everything behind the lens/ciliary body

What is the anterior cavity? It has two parts, what are these?

Anterior cavity - in front of ciliary body and lens

• anterior chamber - in front of iris

• posterior chamber - behind iris

What are the two fibrous parts of the eye? What do they do?

Cornea and sclera are continuous with each other. Sclera = white part of eye, cornea = clear and covers iris/pupil/lens

What structures are located deep to the fibrous part of the eye?

choroid, ciliary body, iris

What are the two muscles in the iris and what do they do?

Sphincter pupillae - size decreases, parasympathetic

Dilator pupillae - size increases, sympathetic

What does the ciliary body produce?

Aqueous humor for anterior segment.

What is the process of parasympathetic control of the eye?

via OCULOMOTOR nerve

parasympathetics of oculomotor nerve exit edinger westphall nucleus, travel to ciliary ganglion and synapse, go to sphincter pupillae

What is the process of sympathetic control of the eye?

fibers work their way up from thoracolumbar region, redistribute themselves around carotid and become carotid plexus, exit, then go to dilator pupillae

The retina is essentially an extension of ___.

The optic nerve

What is the optic disc?

“blind spot,” where all nerve fibers bundle together and form optic nerve

What is the macula?

Light is focused here for fine detailed vision

What are the six extraocular muscles that control eye movement? What nerves are they controlled by?

Lateral and medial rectus, superior and inferior rectus, superior and inferior oblique

All controlled by oculomotor except for lateral rectus (abducens) and superior oblique (trochlear)

What does the lens do?

Focuses light on specific areas of retina for detail vision

What is the difference between myopic and hyperopic eyes?

myopic - eye is too long, nearsighted (can only see close)

hyperopic - eye is too short, farsighted (can only see far)

What do rods and cones do?

convert light into electrical and chemical signals to the brain. embedded in pigment cells

What are the two main visual pigments in rods and cones? What is the cyclic process that occurs here?

Rhodopsin and opsin.

1. Starts as rhodopsin in the dark. (opsin + 11-cis-retinal)

2. light hits it, turns it into opsin + 11-trans-retinal, then components separate

3. Enzymes convert it back into 11-cis-retinal and it recombines with opsin to once again form opsin

What happens when these changes occur in retinal?

A G-protein pathway is activated and a signal is sent

Vision is a three-neuron pathway. What are the three parts of this pathway?

1. Photoreceptor

2. Bipolar neuron

3. Ganglion cell

What are the differences between rods and cones?

RODS- noncolor vision, high sensitivity (low light), more

CONES - color vision, low sensitivity (bright light), less

What is the nasal vs. temporal retina?

nasal - inner half, detects outer visual field

temporal - outer half, detects inner visual field

Describe the steps of vision processing

1. Light detected by cones

2. Signal passed to bipolar neuron

3. Signal passed to ganglion cell

4. Axons of ganglion cell come together to form optic nerve

5. Optic nerve travels back and forms optic chiasm, where fibers from nasal retina cross

6. Nerve fibers travel down the optic tract. Will have fibers from nasal retina of contralateral side and fibers from temporal retina of ipsilateral side.

How is smell detected?

1. Odorants dissolve into nasal epithelium

2. They bind to receptors on olfactory neurons (which are bipolar)

3. Olfactory neurons form olfactory bulb, then travel through nasal cavity to synapse in olfactory tract

What are the receptor cells for taste?

Gustatory epithelial cells

What three nerves innervate the tongue?

Anterior 2/3 - facial

epiglottis - vagus

posterior 1/3 - glossopharyngeal

What are the function of the ossicles and tympanic membrane in the middle ear?

Tympanic membrane recieves sound and rattles ossicles, which communicates sound to inner ear

What are the three ossicle bones?

malleus, incus, stapes

What is the function of the pharyngotympanic tube?

Communication between the pharynx and middle ear, helps regulate pressure from external environment

The inner ear is innervated by one nerve and has two main parts. What are these?

The vestibular system (balance) and cochlea (hearing). innervated by vestibulocochlear nerve, which splits into two

How do otolith organs (utricle, macula, saccule) function in the vestibular system?

These organs are flat, jelly-like slabs weighed down by calcium crystals (otoconia). when these crystals move, stereocilia in neurons detect these changes

How do semicircular canals function in the vestibular system?

They are filled with fluid; changes in acceleration of the fluid shifts cupula, which is detected as movement

Which cranial nerve innervates most of the visceral organs?

vagus