Anat 215 - Block Theory Evaluation #2
visceral afferents
Sensory fibers that convey impulses from the visceral organs (organs within the ventral cavity).
extrinsic eye muscles
Six muscles that originate from the bony eye socket and attach to the outer surface of the eye to produce eye movements
Mnemonic for cranial nerve type
Some Say Marry Money But My Brother Says Big Brains Matter More
Sympathetic Nervous System origin
T1-L2
Cornea
The clear tissue that covers the front of the eye to form a window to let in light.
intrinsic eye muscles
The muscles that help the iris control the amount of light entering the pupil
parasympathetic nervous system origin
brainstem (cranial nerves III, VII, IX, X) and spinal cord (Sacral nerves) -craniosacral
How are spinal nerves formed?
by the combination of the ventral and dorsal roots of the spinal cord
somatic efferent neurons
carries information from the CNS to skeletal muscles; we can consciously control the activity of these muscles
What three components make up a prevertebral ganglia?
celiac, superior mesenteric and inferior mesenteric
The vascular tunic includes...
choroid, ciliary body, iris, pupil
autonomic efferent neurons
connect the CNS to autonomic effectors including smooth muscle, cardiac muscle, glands, and epithelia
suspensory ligaments of the ciliary body
connect the ciliary body to the lens to change the position and shape
lacrimal apparatus
consists of lacrimal gland and ducts that drain into nasal cavity
pupillary sphincter (circular) muscle
contracts in close vision and bright light to constrict the pupil (allowing less light to enter)
pupillary dilator (radially) muscle
contracts in distant vision and dim light to dilate the pupil (allowing more light to enter)
cranial outflow of parasympathetic
cranial nerves 3(III), 7(VII), 9 (IX), 10 (X). these cranial nerves originate in the dorsal motor nucleus of the medulla with the ganglia close to the target organ
Parasympathetic pathways (2)
cranial outflow and sacral outflow
Why is the cornea the only tissue able to be transplanted without rejection?
do not have blood vessels which would otherwise help the immune system distinguish it as a foreign object
ciliary processes
epithelial tissue folds on the inner surface of the ciliary body that secrete aqueous humor
Hypoglossal nerve (CN XII)
exits the medulla on its anterior surface to supply muscles located under the tongue for speech, manipulation of food and swallowing (motor)
Accessory structures of the eye
eyebrows, eyelids, conjunctiva, lacrimal apparatus, extrinsic eye muscles
What are the three tunics of the eye?
fibrous, vascular, sensory
Parasympathetic neurons
has a longer preganglionic neuron and a shorter postganglionic neuron
Sympathetic neurons
has a shorter preganglionic neuron and larger postganglionic neuron
Why is the SNS referred to as "neuronal divergent"?
has widespread effects throughout the body
Motor (efferent) division
includes both somatic and autonomic neurons which carry information away from the central nervous system to effector organs
sensory tunic (retina)
innermost tunic that is composed of 2 layers; the outer pigmented layer and an inner neural layer
Nerve plexuses are...
interwoven networks of nerves
flow of tears
lacrimal canals → lacrimal sac → nasolacrimal duct → empties into the nasal cavity
What muscle allows you to raise the eyelid?
levator palpebrae superioris muscle
paravertebral ganglia
mass of nerve cell bodies close to the spinal cord on both sides
What nerve branches are involved in the formation of dermatomes?
only ventral branches
optic nerve (CN II)
originates at the cerebellum and innervates at the retina as it carries impulses from the retina to the brain to provide the sense of sight (sensory)
Vestibulocochlear nerve (CN VIII)
originates at the pons and is composed of 2 nerves, the cochlear part enables hearing and the vestibular part mediates balance and motion (Sensory)
olfactory nerve (CN I)
originates from the cerebrum and conducts nerve impulses for smell (sensory)
inferior oblique extrinsic eye muscle
originates from the medial wall of the orbit, runs laterally and obliquely to insert onto the bottom lateral side of the eyeball; functions to rotate the eye upward and laterally when it contracts
Glossopharyngeal nerve (CN IX)
originates from the medulla and innervates onto the pharyngeal muscles to enable swallowing, it also innervates the posterior one-third of the tongue, middle ear and parotid glands (mixed)
Vagus nerve (CN X)
originates from the medulla oblongata and leaves the head and neck region into the thoracic and abdominal cavities, providing parasympathetic supply to the heart; provides movement for muscle of the neck responsible for swallowing and speech (mixed)
Accessory nerve (CN XI)
originates from the medulla to provide movement of the head and shoulders such as the sternocleidomastoid and trapezius (motor)
Oculomotor nerve (CN III)
originates from the midbrain and innervates at the eye where it enables eye movement, constriction of the pupil and lens accommodation (motor)
Trochlear Nerve (CN IV)
originates from the midbrain and innervates the superior oblique muscle allowing for movement of the eyeball
Abducens nerve (CN VI)
originates from the pons and extends to the lateral rectus muscle of the eye to abduct the eye (motor)
Facial nerve (CN VII)
originates from the pons and extends to the taste buds to provide taste to 2/3 of the tongue, it also provides movement to muscles of facial expression (mixed)
Trigeminal nerve (CN V)
originates from the pons as it contains both special visceral and somatic fibres; is contains 3 branches: 1. Ophthalmic - sensory to the eye and forehead 2. Maxillary - sensory to upper jaw region 3. Mandibular - sensory to lower jaw region; motor to muscles of mastication (mixed)
superior oblique extrinsic eye muscle
originates with the superior rectus muscle, runs medially along the orbit and then makes a short right angle turn before inserting at the superior lateral part of the eyeball; functions to rotate the eyeball downward and laterally when it contracts
what separates the free margins of the eye when the eyes are open?
palpebral fissure
"Travel through" paravertebral ganglion pathway
pass through the sympathetic trunk (white ramus) and paravertebral ganglion, synapse at prevertebral ganglion and travel to the target site
How does light flow through the inner neural layer?
photoreceptors → bipolar cells → ganglion cells (which form the optic nerve)
choroid (vascular tunic)
provide nutrients to retina
what two smooth muscles are the iris made up of?
pupillary sphincter muscle (circular) and the pupillary dilator muscle (radially)
What are the 5 components of reflexes?
receptor, sensory neuron, integration center, motor neuron, effector
function of the vascular tunic
regulates the amount of light that enters into the eye and controls the shape of the lens
Sacral outflow of parasympathetic
sacral nerves S2, S3 and S4 innervates organs of the pelvis and lower abdomen and contains no ganglia just plexus meaning there is no synapse
What can happen if the signal enters the paravertebral ganglia? (3)
same synapse, travel up or down the sympathetic trunk or travel through the sympathetic trunk and synapse at the prevertebral ganglion
fibrous tunic of the eye includes...
sclera and cornea
What does the conjunctiva produce?
secretes a lubricant to protect the eye from drying out
somatic afferents
sensory fibers that convey impulses from the skin, skeletal muscles and joints
function of eyebrows
shade eye from sunlight, prevent perspiration from reaching eye
outer pigmented layer of retina
single cell thick lining that extends anteriorly to cover the ciliary body of the posterior face of the iris and functions to absorb the light and prevent it from scattering in the eye
Sensory (afferent) division
somatic and visceral sensory nerve fibers which conduct impulses from receptors to the CNS
What are the two major nerves that exist in the peripheral nervous system?
spinal nerves (carry information to and from the spinal cord) and cranial nerves (carry information to and from the brain)
What 4 extrinsic eye muscles originate from the orbit and extend straight out?
superior rectus inferior rectus medial rectus lateral rectus NOTE: their function and location is in their name
What are the 6 extrinsic eye muscles?
superior rectus, inferior rectus, lateral rectus, medial rectus, superior oblique, inferior oblique
What is released at the second synapse in the sympathetic and parasympathetic neurons?
sym - epinephrine or norepinephrine para- acetylcholine
divisions of autonomic nervous system
sympathetic (fight or flight) and parasympathetic (rest and digest)
"Travel up or down" paravertebral ganglion pathway
synapse would occur and pass through the white ramus to enter the ganglion and travel up or down the sympathetic trunk, exiting through the grey ramus at a different ganglion and traveling to its target site
"Same synapse" paravertebral ganglion pathway
synapse would occur at the same level after it passes through the white ramus to enter the ganglion and through the grey ramus to exit a different ganglion and travel to the target site
pupil
the adjustable opening in the center of the eye through which light enters
What connects the two eyelids together?
the medial and lateral canthus
Vascular tunic
the middle coat of the eye known as the uvia which contains the blood and lymphatic vessels are present which supply the eye
autonomic nervous system (ANS)
the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). - involuntary muscle control
Divisions of the peripheral nervous system
the sensory (afferent) and motor (efferent division)
Peripheral Nervous System (PNS)
the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body.
Cillary body (vascular tunic)
thickened ring of tissue that encircles the lens consisting of the intrinsic eye muscles, ciliary processes and suspensory ligaments
inner neural layer of retina
transparent layer composed of photoreceptors (rods and cones), bipolar cells and ganglion cells
blind spot (optic disc)
where the optic nerve leaves the eye; there are no photoreceptor cells here
Sclera
white of the eye which shapes and protects the eyes providing an anchoring site for all the extrinsic eye muscles
How many spinal nerves are there?
31 pairs 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal
What 3 cranial nerves control the extrinsic eye muscles?
CN III (controls the superior rectus, inferior rectus, lateral rectus and inferior oblique muscles) CN IV (control the superior oblique muscle) CN VI (controls the medial rectus muscle)
conjunctiva
Delicate membrane covered by stratified squamous epithelium that lines the eyelids and covers the eyeball
visceral reflexes
- produced by the autonomic nerves and initiated in the viscera - activates smooth and cardiac muscles or glands
somatic reflexes
- produced by the somatic nervous system and innervates skeletal muscle. - induced by stimulation of somatic sensory nerve endings
What is the difference between the somatic and autonomic nervous system (2)
- somatic has one neuron where as autonomic is made up of two - first synapse occurs at a ganglion and then the second occurs at the target organ in ANS compared to there being only one synapse at the target organ is SNS
Parasympathetic preganglionic neurons can... (3)
1. Synapse at the cranial ganglia to supply the head (CN III, VII and IX) 2. Form a parasympathetic plexus to supply thoracic & abdominal plexuses(CN X) 3. Form splanchnic nerves to supply terminal gut and pelvic viscera
Preganglionic pathway (5)
1. fibres leave the lateral horn 2. pass through the ventral root to exit the spinal cord 3. pass through the spinal nerve 4. pass through the white ramus 5. enter the paravertebral ganglia
How many cranial nerves are there?
12 pairs
Mnemonic for cranial nerves
On Occassion Our Trusty Truck Acts Funny. Very Good Vehicle Any How.
function of eyelids
Protect the eyes from injury, strong light, and dust.
caruncle of the eye
a fleshy projection located in the medial canthus which secretes a white oily substance
brachial plexus
a network of nerve axons (C5-C8, T1) which supply the upper limbs
lumbosacral plexus
a network of nerve axons of the spinal nerves (T12-S4), which supply the lower limbs
Iris
a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening
What is released at the first synapse in the sympathetic and parasympathetic neurons?
acetylcholine
What spinal nerves participate in the formation of dermatomes?
all spinal nerves except C1 since it does not have a sensory root
prevertebral ganglia
also known as preaortic ganglia as it is located along the anterior surface of the aorta
Dermatomes are
an area of the skin innervated by the by the cutaneous branches of a single spinal nerve
What are the two chambers of the eye?
anterior chamber and posterior chamber
anterior chamber of eye
between cornea and iris, contains aqueous humor
What are the 2 major plexuses within the peripheral nervous system?
brachial and lumbosacral plexuses
