Virginia Tech BMSP 2135 RAT #19

Sensory (afferent) division, motor (efferent) division

What are the two functional divisions of the PNS?

somatic sensory division, visceral sensory division

What are the two subdivisions of the sensory (afferent) division of the PNS?

general senses

somatic sensory division

- contains neurons that detect sensory stimuli from the skin and structures of the musculoskeletal system

- Its neurons respond to stimuli of the ___________ _________ that arise external to the body, such as touch, temperature, and pain, as well as those originating from within the body, such as muscle stretch and the concentration of different chemicals in the body's fluids

- The somatic sensory division also contains special sensory neurons that are responsible for detecting stimuli of the special senses (vision, hearing, equilibrium, taste, and smell).

abdominopelvic and thoracic cavities.

somatic visceral division

- contains neurons that relay sensory stimuli from the organs of the where?

- Its neurons detect internal changes such as blood pressure and the degree to which organs such as the urinary bladder are stretched

somatic motor division, visceral motor division

what are the 2 subdivisions of the motor (efferent) division of the PNS?

lower motor neurons

somatic motor division

- responsible for the body's voluntary motor functions.

- It is made up of ________ ___________ ___________ (or somatic motor neurons) that directly contact skeletal muscle fibers and trigger a contraction when stimulated by upper motor neurons in the CNS

homeostasis

visceral motor division

- responsible for maintaining the _______________ of many physiological variables through its control of the body's involuntary motor functions.

- its neurons innervate cardiac muscle cells, smooth muscle cells, and the secretory cells of glands.

autonomic nervous system (ANS)

What is another name for the visceral motor division?

sympathetic, parasympathetic

what are the 2 divisions of the ANS?

fight or flight

sympathetic ANS

- "_______ ___ ________" division of the ANS that prepares the body for exercise, emergency, and emotion

- role in preparing the body for emergency situations that would involve fighting off an attacker or fleeing from danger.

- Its role is broader than this, however, as it maintains homeostasis when the body is engaged in any type of physical work and mediates the body's visceral responses to emotion

rest and digest

parasympathetic ANS

- "______ ____ ________" division of the ANS that promotes maintenance functions such as defecation, diuresis, and digestion

- role in digestion and in maintaining the body's homeostasis at rest

peripheral nerves (a.k.a nerves)

What are the main organs of the PNS?

common connective tissue sheath

a nerve consists of the axons of many neurons bound together by a what?

mixed nerves

Most nerves are _________ _________, meaning they contain both sensory and motor neurons. This is why a damaged nerve affects both sensation and movement to some degree.

sensory nerves

although most are mixed, there are __________ _________ that contain only sensory neurons and motor nerves that contain mostly motor neurons.

sensory neurons

All motor nerves contain a small population of __________ ____________ that carry stimuli pertaining to muscle stretch and tension, so no nerve is a pure motor nerve.

anterior root, posterior root

What two structures connect spinal nerves to the spinal cord?

motor neurons

an anterior root contains the axons of _________ ______________ exiting the anterior horn

sensory neurons

a posterior root contains the axons of __________ ___________ entering the posterior horn

anterior root

an extension from the anterior horn of the spinal cord containing the axons of lower motor neurons; some also contain the axons of visceral motor neurons

posterior root

the extension from the posterior horn of the spinal cord containing the axons of somatic sensory neurons

spinal nerve

The anterior and posterior roots fuse to form a what?

mixed nerves

Each spinal nerve contains both sensory and motor neurons, so all are __________ ___________

pseudounipolar

Most sensory neurons are what type of neuron?

posterior root ganglion (dorsal root ganglion)

posterior root features an enlarged area that houses the cell bodies (somas) of sensory neurons just lateral to the spinal cord

this swollen area in the posterior root is called the what?

ganglion

What is the term for a collection of somas in the PNS?

31

There are _____ pairs of spinal nerves

cranial nerve

a nerve containing axons whose origin or destination is the brain; they attach to the brain and mainly innervate structures of the head and neck

motor

Unlike spinal nerves, cranial nerves are not formed from the fusion of motor and sensory nerve roots, and so some cranial nerves are purely sensory, others are mixed, and others are predominantly _________

epineurium

the connective tissue sheath that surrounds a peripheral nerve; wraps the nerve as a whole

fascicles

Within the nerve, axons are bundled into smaller groups known as ____________

perineurium

the connective tissue that surrounds a fascicle of a peripheral nerve; nestled between the fascicles are blood vessels that supply the axons with oxygen and nutrients

endoneurium

the connective tissue that surrounds an axon within a peripheral nerve

the same

the arrangement of connective tissue sheaths within spinal and cranial nerves is (different/the same)

sensory receptors

Sensory neurons detect stimuli at structures known as ___________ ______________

cerebral cortex

detected sensory stimuli are transmitted along the sensory neurons via spinal or cranial nerves to sensory neurons of the CNS, which transmit the impulses to the ___________ ___________ for interpretation and integration.

motor areas

Depending on the nature of the sensory stimuli, an appropriate motor response is initiated

The motor response is initiated by commands from the _________ _________ of the brain to the upper motor neurons

lower motor neurons

These impulses travel to the spinal cord, where they synapse on local interneurons and then lower motor neurons of the PNS. The ________ ___________ ____________ then carry the impulses to the appropriate muscle fibers via specific cranial or spinal nerves, where they trigger their contraction

anterior horn of spinal gray matter

If the motor signal is sent along a spinal nerve, where are the somas located?

anterior root

In which root of the spinal nerve will the axons travel for a motor response?

12

there are _____ pairs of cranial nerves

olfactory (I), optic (II), vestibulocochlear (VIII)

cranial nerves

which cranial nerves are sensory nerves?

(hint: there are 3)

oculomotor (III), trochlear (IV), abducens (VI), accessory (XI), hypoglossal (XII)

cranial nerves

which cranial nerves are motor nerves?

(hint: there are 5)

trigeminal (V), facial (VII), glossopharyngeal (IX), vagus (X)

cranial nerves

which cranial nerves are mixed nerves?

(hint: there are 4)

special senses

3 cranial nerves that contain the axons of ONLY sensory neurons: olfactory (I), optic (II), and vestibulocochlear (VIII) nerves, which are each involved in one of the __________ ____________

olfactory nerve

CN I =

cribriform plate of the ethmoid bone

olfactory nerve (CN I)

The axons form bundles that penetrate the holes in the __________ ___________ of the _________ bone

olfactory bulb

olfactory nerve (CN I)

the axons end where?

olfactory tract

olfactory nerve (CN I)

What structure carries the olfactory signals to the cerebrum?

temporal lobe

olfactory nerve (CN I)

What cerebral lobe initially processes smell?

optic nerve

CN II =

optic chiasma

optic nerve (CN II)

- the two optic nerves meet and form an "X" called the _________ __________, where some of the axons decussate (switch sides)

thalamus

optic nerve (CN II)

axons from the optic chiasma are destined for structures such as the ____________, the midbrain, and ultimately the primary visual cortex in the occipital lobe

vestibulocochlear nerve

CN VIII =

balance & equilibrium, hearing (audition)

vestibulocochlear nerve (CN VIII)

What information is carried by this nerve?

axons of proprioceptive sensory neurons

The motor cranial nerves—the oculomotor (III), trochlear (IV), abducens (VI), accessory (XI), and hypoglossal (XII) nerves—also technically contain what?. In spite of this, they are still viewed as motor nerves because the main function of their sensory neurons is to allow the brain to monitor the contraction of the muscles they innervate.

extrinsic eye muscles and smooth muscles of the eye

motor cranial nerves

the oculomotor nerve (CN III) innervates what?

superior oblique muscle of the eye

motor cranial nerves

the trochlear nerve (CN IV) innervates what?

lateral rectus muscle of the eye

motor cranial nerves

the abducens nerve (CN VI) innervates what?

accessory

The ____________ nerve is the only cranial nerve that has a component from the spinal cord (it is a cranial nerve with spinal cord accessories).

speech

motor cranial nerves

the accessory nerve (CN XI)

- the cranial component of the accessory nerve innervates certain muscles of _________

muscles that move the head and shoulder (trapezius and sternocleidomastoid)

motor cranial nerves

the accessory nerve (CN XI)

- the spinal component of the accessory nerve innervates what?

hypoglossal nerve

CN XII =

below, tongue

hypoglossal nerve

- what does "hypo" mean?

- what does "glosso" mean?

therefore, the destination of the hypoglossal nerve is inferior to the tongue

innervates the (intrinsic and extrinsic) muscles of the tongue

what is the function of the hypoglossal nerve (CN XII)?

trigeminal nerve

the mixed cranial nerves—the trigeminal (V), facial (VII), glossopharyngeal (IX), and vagus (X) nerves—are generally large and have a fairly wide distribution.

All but one (the _____________ _________) contain somatic sensory, somatic motor, and parasympathetic neurons wrapped up in the same nerve

The mixed cranial nerves have multiple and diverse functions due to their size and the different types of neurons they house

trigeminal nerve

mixed cranial nerves

CN V =

facial nerve

mixed cranial nerves

CN VII =

masseter, temporalis

mixed cranial nerves

trigeminal nerve

- the motor axons of the mandibular nerve of the trigeminal nerve supply the ___________ and ___________ muscles to elevate the mandible

ophthalmic nerve, maxillary nerve, mandibular nerve

mixed cranial nerves

what are the 3 branches of the trigeminal nerve?

facial sensation

mixed cranial nerves

trigeminal nerve

- has 3 branches

- the sensory root of the trigeminal nerve detects __________ ___________

taste, somatic

mixed cranial nerves

The sensory root of the facial nerve (VII) provides _______ sensation and _________ sensation

glossopharyngeal nerve

mixed cranial nerves

CN IX =

throat

mixed cranial nerves

glossopharyngeal nerve (CN IX): what does "pharynx" mean?

glossopharyngeal

mixed cranial nerves

the _____________________ nerve (CN IX) senses taste (from the back third of the tongue), as well as innervates muscles of the pharynx

vagus nerve

mixed cranial nerves

CN X =

parasympathetic NS

mixed cranial nerves

vagus nerve (CN X)

- This cranial nerve is unique because it innervates many visceral organs including those in the thoracic and abdominal cavity.

- It is important in what system?

eyelids, eyebrows, eyelashes

what are 3 accessory structures of the eye?

palpebrae

eyelids are also called _____________

anterior

eyelids

- Two thin folds that cover the ___________ part of the orbit

- Prevent foreign objects from entering the eye and distribute tears across the surface of the eye during blinking

eyebrows

Hairs along the ridge of the brow form the _____________, which prevent perspiration from running into the eyes, reduce glare in bright light, and aid in formation of facial expressions

Eyelashes

____________ are stiff hairs located in the edges of the superior and inferior palpebrae

they are richly innervated by nerve endings so that the slightest touch triggers the blink reflex, which reduces the risk of eye injury

conjunctiva

a transparent membrane that covers the inside of the eyelids and the anterior sclera

epithelial

the conjunctiva = thin ______________ membrane that lines the posterior surfaces of the eyelids (palpebral conjunctiva) and then turns back on itself as the bulbar (or ocular) conjunctiva to cover the anterior surface of the white part of the eye

lacrimal apparatus

a collection of structures involved in the production and drainage of tears

lacrimal gland

this is located in the superolateral region of the orbit, just posterior to the conjunctiva.

extrinsic eye muscles

6 skeletal muscles that insert into the outer layer of each eyeball

superiorly

the superior rectus muscle moves the eyeball how?

inferiorly

the inferior rectus muscle moves the eyeball how?

medially

the medial rectus muscle moves the eyeball how?

laterally

the lateral rectus muscle moves the eyeball how?

superior oblique muscle

this extrinsic eye muscle travels from the posterior orbit along the medial wall and through a fibrous loop called the trochlea before inserting on the superolateral part of the eyeball

depression of the eye and laterally

the superior oblique muscle moves the eyeball how?

superiorly & laterally

the inferior oblique muscle moves the eyeball how?

fibrous, vascular, neural

what are the 3 layers of the eyeball?

sclera, cornea

what are the 2 components of the fibrous layer of the eyeball?

white

fibrous layer of eyeball

sclera

- the "________" part of the eyeball

- thick collagenous structure that helps to maintain the shape of the eye

- covers about 5/6 of the surface of the eyeball

- continuous with the cornea

- collagen fibers allow it to resist deformation from external and internal forces and maintain its shape

focusing

fibrous layer of eyeball

cornea

- a transparent structure on the anterior eye that refracts light as it enters the eye; plays an important role in admitting light into the eye and _____________ it

- covers the anterior 1/6 of the eyeball

- translucent due to its orderly parallel arrangement of collagen fibers, relative lack of water in its tissue, and absence of blood vessels (AVASCULAR)

choroid, ciliary body, iris

what are the 3 components of the vascular layer of the eyeball?

choroid

pigmented portion of the vascular layer of the eyeball that contains many blood vessels to nourish the retina