ANAT 3601 Test 2

Cranial Nerve II (Optic Nerve)

- Function: vision - Location of receptors: retina of eye - Pathway through skull: optic foramina

Basal nuclei

- groups of neuronal cell bodies (gray matter) located deep within the white matter of the brain (cerebral hemispheres) - *integrate motor activity* - *found in cerebellum*

Rhombencephalon

- hindbrain - Secondary vesicles at 5th week: Metencephalon and Myelencephalon

Lateral horns

- house the cell bodies of autonomic motor neurons (to involuntary muscle sand glands) - can only be found between spinal cord levels T1-L2

Saltatory conduction

- impulses are able to skip parts of the axon when sending a signal - impulses jump from node to node, which increases conductivity

Primary visual cortex

- in occipital lobe - process visual information

Primary auditory cortex

- in temporal lobe - hearing

Primary olfactory cortex

- in temporal lobe - smell

Conus medullaris

- inferior end of spinal cord. - Located between L1 and L2 vertebrae.

Cerebral peduncle

part of the midbrain that link the remainder of the brainstem to the thalamus and thereby, the cerebrum

Third ventricle

passes through the mesencephalic aqueduct into the 4th ventricle

Metencephalon

pons and cerebellum and fourth ventricle

Superior colliculi

visual reflexes

Lateral sulcus

between the cerebral hemispheres

Transverse fissure

between the cerebral hemispheres extending this open exposes the insula

Meningeal dura

bottom layer of dura

Central Nervous System (CNS)

brain and spinal cord

Association tracts

bundles of axons connecting different regions of the cerebral cortex in one hemisphere - Ex: from frontal lobe to occipital lobe

Parasympathetic Component of Vagus Nerve

cause decreased respiratory and heart rate and increase action of digestive system *peristalsis*

Splanchnic nerve

come off chain ganglion and go into organs

Hypothalamus

Master controller of the *autonomic nervous system*, master controller of the endocrine system, regulates body temperature, food intake and water intake.

Corpus callosum

connects left and right hemispheres

Mesencephalic aqueduct

connects third ventricle to fourth ventricle

Dorsal roots

contain the central process of sensory nerves from the body

Peripheral Nervous System (PNS)

cranial and spinal nerves

Monosynaptic reflex

direct communication between sensory and motor neuron

Lumbosacral plexus

forms the nerves of the lower extremities

Posterior cord

formed from superior, middle, and inferior trunks

Myelencephalon

medulla and the fourth ventricle

Sigmoid sinus

- blood flows down this from the transverse sinuses into the jugular foramen

Cranial Nerve X (Vagus nerve)

- *Functions*: •Somatic motor to muscles of soft palate, pharynx and larynx. •Autonomic motor (parasympathetics) to the heart, lungs and most of the abdominal organs. - intramural ganglia are associated with this - Pathway through skull: jugular foramen.

Mesencephalon

- *midbrain and cerebral aqueduct* - Secondary vesicle at 5th week: stays mesencephalon

Diencephalon

- *thalamus, hypothalamus, epithalamus and third ventricle* - derived from prosencephalon - located within the white matter of the brain and has 3 parts

Thoracic region of spinal cord

- 12 pairs of spinal nerves traveling between the thoracic vertebrae

Meninges

- 3 layers: dura mater, arachnoid mater, pia mater

Sacral region of spinal cord

- 5 pairs of spinal nerves - contribute to innervation of lower extremity.

Lumbar region of spinal cord

- 5 pairs of spinal nerves - provides most of the innervation of the lower extremities

Cervical region of spinal cord

- 8 pairs of spinal nerves - provides most of the innervation of the upper extremities.

Ganglion

- A collection of *nerve cell bodies* in the *PNS* (not to include basal ganglia) - site of synapse between preganglionic and postganglionic neurons in the ANS

Four types of cells in the CNS

- Astrocytes - Ependymal cells - Microglia - Oligodendrocytes

Motor speech area

- Broca's area - allows us to speak (or write) to people in a way that makes sense - *speech organization*

Motor (efferent) neurons

- Cells bodies in CNS. - Axons carry impulses muscles and glands (effector). - multipolar

Cranial Nerve I (Olfactory nerve)

- Function: smell - Location of receptors: roof of nasal cavity - Pathway through skull: olfactory foramina of cribriform plate

Cranial Nerve VI (Abducens nerve)

- Function: somatic motor to lateral rectus muscle. - Pathway through skull: through superior orbital fissure.

Cranial nerve XII (Hypoglossal nerve)

- Function: somatic motor to muscles of the tongue (intrinsics, genioglossus, styloglossus, hyoglossus) - Pathway through skull: Hypoglossal canal

Cranial Nerve IV (Trochlear nerve)

- Function: somatic motor to superior oblique muscle. - Pathway through skull: superior orbital fissure.

Cranial Nerve XI (Accessory nerve)

- Function: somatic motor to trapezius and sternocleidomastoid muscles. - Pathway through skull: jugular foramen

Cranial Nerve III (Oculomotor nerve)

- Functions • somatic motor to 4 of 6 muscles of the eye, plus the levator palpebrae superioris. • autonomic motor (parasympathetics) to the lens and pupil. - Location of postsynpatic pFunction: somatic motor to lateral rectus muscle. Pathway through skull: through superior orbital fissure.arasympathetic cell bodies: ciliary ganglion. - Pathway through skull: superior orbital fissure.

Cranial Nerve VII (Facial nerve)

- Functions: • Somatic motor to muscles of facial expression, posterior belly of digastric and stylohyoid. • Autonomic motor (parasympathetics) to lacrimal gland, submandibular and sublingual salivary glands. • Special Sensory: taste from the anterior 2/3 of the tongue. - Location of post‐synaptic parasympathetic cell bodies: submandibular and pterygopalatine ganglia. - Pathway through skull: Into internal auditory meatus and out through stylomastoid foramen.

Cranial nerve IX (Glossopharyngeal nerve)

- Functions: •Autonomic motor (parasympathetics) to parotid glands. •General sensory: from posterior 1/3 of tongue. •Special sensory: taste from posterior 1/3 of tongue. •Regulates blood gases and pressure from carotid body and sinus, respectively. - Pathway through skull: jugular foramen.

Cranial Nerve V (Trigeminal nerve)

- Functions: •Sensory from skin of face, eye, nasal cavity, teeth and anterior 2/3 of tongue. •Somatic motor to muscles of mastication (temporalis, masseter, pterygoids), mylohyoid, anterior belly of digastric and tensor veli palatini. •All 3 divisions are sensory and only V3 has motor function.

Cranial Nerve VIII (Vestibulocochlear nerve)

- Functions: balance (vestibular) and hearing (cochlear). - Location of receptors: inner ear. - Pathway through skull: internal auditory meatus.

Cords

- Lateral - Posterior - Medial

Mandibular branch (V3)

- Pathway: through foramen ovale - only one that has motor functions

Interneurons (association neurons)

- Receive impulses from sensory neurons and "decide" what to do with it. - They facilitate communication between sensory and motor neurons.

Sensory (afferent) neurons

- Receptors for touch, pressure, pain, vision, hearing, balance, taste and smells. - Cells bodies in posterior root ganglion, outside of CNS. - Central process carries sensation to CNS

Somatic Nervous System

- Sensory (sensations we are aware of) Touch Pain Visual input Sounds Smells Tastes -Motor (actions we control voluntarily) Walking Running Throwing Chewing Smiling - often sensations carried by this activate an autonomic motor response - skeletal muscles - always excites a target

Autonomic (Visceral) Nervous System

- Sensory (sensations we are not necessarily aware of) Change in blood pressure Change in body temperature Food in intestine Amount of oxygen in blood Heart-rate - *Motor (actions that take place without conscious thought)* Arteries constrict or dilate We sweat Digestive "juices" are secreted Respiratory rate increases Heart-rate speeds up or slows down Pupil of eye contricts or dilates - often sensations carried by this activate a somatic motor response - *cardiac muscle, smooth muscle, and glands* - can excite or inhibit a target

Trunks

- Superior - Middle - Lateral

Apertures

- allows CSF to leak out and flow outside of brain - subarachnoid space

Precentral gyrus

- also called primary motor cortex - controls *motion* opposite side of body

Postcentral gyrus

- also called primary somatosensory cortex - receives *sensation* from the opposite side of the body

Straight sinus

- at junction of falx cerebri and tentorium cerebelli - drains into the confluence

Corticospinal tract

- axons descend from the cerebral cortex *(precentral gyrus)* through the brainstem and form a pair of thick bulges on the anterior medulla oblongata called the pyramids - *anterior tract: descends and crosses in the spinal cord* - *lateral tract: descends and decussates in pyramids* - 85% of axons in these tracts form the lateral corticospinal tract, which cross to the opposite side of the medulla oblongata at the "decussation of the pyramids" - they then descend into the spinal cord, traveling in the lateral funiculi - if damaged, weakness would occur on the same side

Anterolateral Pathway

- axons travel in anterior and later funiculi - *lateral: pain and temperature* - *anterior: crude touch; if damaged, loss of crude touch from that level of damage and below on the opposite side of the body* - Second-order neurons cross to the opposite (contralateral) side of the spinal cord and ascend in either the anterior or lateral funiculus to the thalamus - the neurons in the thalamus send their axons to the postcentral (sensory) gyrus of the cerebral cortex to relay this information

Arachnoid mater

- below dura mater - looks web-like

Parasympathetic nervous system (Craniosacral)

- both pre and post synaptic neurons release acetylcholine (opposite effect to norepinephrine) - rest and digest - does not innervate sweat glands, arrector pilli, or blood vessels - presynaptic neurons relatively long - postsynaptic neurons are relatively short - ganglia close to target organs - cranial nerves that have this component are: CN III, VII, IX, and X

Commissural tracts

- bundles of axons connecting two hemispheres. The largest is the corpus callosum. There is also an anterior and posterior commissure

Transverse sinus

- carry blood from external occipital protuberance to right behind ears

Sensory pathways

- carry information regarding touch, temperature, pressure, and pain

Parasympathetic component of oculomotor nerve

- cause constriction of pupil and thickening of the lens. - part of the autonomic motion, not somatic - constricts pupil

Parasympathetic Component of Facial Nerve

- cause lacrimation and salivation from *submandibular and sublingual salivary* glands. - fibers leave brain stem, 2 are salivary, 1 is lacrimal (tears)

Parasympathetic Component of Glossopharyngeal Nerve

- cause salivation from parotid glands. -

Ventricles

- cavities in the brain that contain cerebral spinal fluid

Gray matter of spinal cord

- centrally located and shape resembles a butterfly - has anterior and posterior horns in particular regions - consists of neuron cell bodies, short unmyelinated axons, dendrites, and neuroglia

Telencephalon

- cerebrum - lateral ventricles

Spinocerebellar pathway

- conducts proprioceptive information to the cerebellum for processing to coordinate body movements - composed of anterior and posterior spinocerebellar tracts - the anterior spinocerebellar tracts conduct impulses from the lower extremities and the posterior spinocerebellar tracts conduct impulses from the upper extremities - second-order neurons in the posterior horns send their axons up to the cerebellum - *proprioception: knowing how your body is positioned in space at any time, even when your eyes are closed; due to cerebellum*

Posterior Funiculus - Medial Lemniscal pathway

- conducts sensory information about *fine touch, pressure,* vibration, and *proprioception* - information from the lower extremities travel in fasciculus gracilis while those carrying information from the upper extremities travel in the fasciculus cuneatus - the second-order neurons in the nuclei *(in the medulla oblongata)* have axons that *cross to the opposite side of the brainstem and up to the thalamus* through a tract called the *medial lemniscus* in the *medulla oblongata* - third-order (or tertiary) neurons in the thalamus send this information to the primary sensory cortex (post-central gyrus) of the cerebrum - damage to funiculus: loss of fine touch and sensation from that point down - damage to the medial lemniscus:

Projection tracts

- connect the cerebral cortex to the spinal cord - a special extension of the projection tracts, connecting the deep cerebral nuclei and the cerebral cortex, is called the internal capsule

Choroid plexus

- continually produces CSF

Anterior rami

- distributed to the *body wall* and extremities - form brachial plexus, inercostal nerves, lumbosacral plexus - contain motor and sensory nerves

Lateral ventricles

- drain into one new ventricle, the third ventricle

Autonomic motor system

- effects cardiac muscle, smooth muscle, and glands (*involuntary*)

Somatic motor system

- effects skeletal or *voluntary* muscles

Cerebral nuclei

- embedded in white matter - dark shadowy looking spots

Inferior sagittal sinus

- empty into straight sinus

Superior sagittal sinus

- empty into the confluence of sinuses

Prosencephalon

- forebrain - Secondary vesicles form at 5th week: telencephalon and Diencephalon

Median nerve

- formed from lateral and medial cords - innervates most of the muscles in the anterior forearm and those in the hand that move the thumb - flex wrist and finger

Musculocutaneous nerve

- formed from lateral cord - innervates muscles of the anterior arm: - biceps brachii, coracobrachialis, brachialis: flexion

Ulnar nerve

- formed from medial nerve - innervates most of the muscles in the medial hand: half of the ring finger and pinky - spreads fingers apart and brings them back together (adduction and abduction)

Radial nerve

- formed from posterior cord - innervates muscles in the posterior arm and posterior forearm - extend elbows, wrist, and fingers - skin in same area will be numb with radial nerve damage

Axillary nerve

- formed from posterior cord - innervates the deltoid and one of the teres minor - deltoid: abduct arm - teres minor: external rotation

Brachial plexus

- forms the nerves of the upper extremities - comes from rami *C5-T1* - C5 and C6 come together to form the superior trunk and then the lateral cord: contributes to formation of median nerve and forms the musculocutaneous nerve - C8 and T1 come together to form the inferior trunk and then the medial cord: contributes to formation of the median nerve and also makes the ulnar nerve - C7 forms middle trunk and then the posterior cord - posterior cord forms from the three branches of the three trunks - the posterior cord also forms the radial and axillary cord

Wernicke's area

- gnostic area - *understanding speech* in talking and reading - sensory speech (incoming)

Posterior rami

- go to errector spinae muscle (deep muscles of the back) and skin around that same zone - small twig like branches on posterior side - contain sensory and motor fibers

Sympathetic Nervous System (Thoracolumbar)

- innervate the smooth muscle and glands in the skin. - If they want to go to the skin, they rejoin the spinal nerves after synapsing in the sympathetic chain - presynaptic neurons are relatively short and the postsynaptic neurons are relatively long - ganglia close to the spinal cord - presynaptic neurons release acetylcholine - postsynaptic neurons release norepinephrine - ganglia include: chain, cervical, and collateral (presynaptic) - only ones to go to sweat glands - vertebral levels T1-L2

Tibial nerve

- innervates most of the muscles in the posterior thigh (hamstrings) and posterior leg and runs into the plantar section of the foot - pat of the sciatic nerve - runs through sciatic notch and all the way down the posterior side of the thigh and leg - extend thigh and flex knee (hamstrings, plantar flex foot at the ankle, toe flexion

Deep fibular nerve

- innervates the muscles in the anterior and lateral leg - dorsiflex foot at ankle, extend toes, and invert the foot

Superficial fibular nerve

- innervates the muscles in the anterior and lateral leg - fibularis longus and brevis: eversion of the foot - on dorsal surface of the foot, except between big toe and second toe

Common fibular nerve

- innervates the muscles in the anterior and lateral leg - part of the sciatic nerve

Femoral nerve

- innervates the muscles in the anterior thigh and medial leg - hip flexion and knee extension

Thalamus

- located on either side of the 3rd ventricle - main *relay center for sensory information traveling up to the cerebral cortex* - helps to process and organize the information going to and coming from the cerebral cortex

White matter of spinal cord

- located on the outside - divided into 3 main regions called funiculi - composed of bundles of myelinated axons - The axons connect various grey matter areas (the locations of nerve cell bodies) of the brain to each other and carry nerve impulses between neurons

Denticulate ligaments

- made up of pia mater - anchors the spinal cord to the bony walls of the spinal cord

Cerebellum

- main brain structure responsible for coordinating the movements of our skeletal muscles

Limbic System

- mammillary body - amygdaloid body - hippocampus - cingulate gyrus - Process and experience emotions - *integrate emotion with memory*

Pons

- middle part of the brain stem - has cerebellum attached to its posterior side - also has attached: - CN 5-8 - *bridge between the cerebellum, spinal cord, and midbrain* - also has two important respiratory centers in it called pneumotaxic and apneustic centers which control the rate and depth of breathing

Medulla Oblongata

- most inferior part of the brainstem - has cardiac center, vasomotor center, and respiratory center - cell bodies of preganglionic autonomic nerves that stimulate the secretion of stomach and acid peristalsis is found here - structures found on/attached to here: - inferior cerebellar peduncles - medullary pyramids - CN VIII, CN IX, CN X, CN XI, CN XII

Midbrain (mesencephalon)

- most superior part of the brain stem - has the cerebral aqueduct running through it which connects the *3rd ventricle to the 4th ventricle* - axon tracts run through it to connect the brain to the spinal cord - also contains the: - cerebral peduncles, - superior cerebellar peduncles, - corpora quadrigemina, - CN III, CN I

Gray matter

- mostly nerve cell bodies

Multipolar neurons

- motor neurons of the CNS and PNS - also function as interneurons - most common type - many dendritic processes and one axon extending from the cell body

Homunculus

- motor on right - sensory on left

White matter

- myelinated axons - deep to the cerebral cortex

Dura mater

- outermost layer - has 2 layers itself: - provides protection (tough)

Dorsal horns

- primarily house the cell bodies of sensory neurons (receiving sensory information from the body) and *interneurons* - cell bodies of primary sensory neurons are in dorsal root ganglia

Ventral horns

- primarily house the cell bodies of somatic motor neurons (innervate skeletal muscles

Inferior colliculi

- relay station that is responsible for initiating reflex responses to auditory stimuli

Two types of glial cells

- satellite cells - neurolemmocytes (schwann cells)

Unipolar neurons

- sensory neurons in the PNS - mainly found carrying information from the skin - have a single, short process emerging from its body and branches out like a T - start out as bipolar then the two process fuse together near the cell body

Exteroceptors

- sensory receptors which receive stimuli from the external environment - Ex: meissner's corpuscles, naked nerve endings, pacinian corpuscles, golgi tendon organs

Bipolar neurons

- specialized for taste, vision, hearing, balance, and smell - two neuron processes that extend from the cell body, one axon, and one dendrite

Pia mater

- stuck to surface of brain - delicate (thin)

Corpora Quadrigemina

- superior colliculi and inferior colliculi - located on the midbrain

Medial and Lateral Plantar nerves

- the terminal branches of the tibial nerve - innervate the muscles in the bottom of the foot

Falx cerebri

-receives blood from veins

Reflexes

1. stimulus activates a receptor 2. nerve impulse travels through sensory neuron to CNS 3. Information is processed in the CNS by interneurons 4. Motor neuron receives impulse and transmits it to effector (muscle or gland) 5. effector responds

Nerve regeneration

1. the axon is severed 2. Proximal portion of the severed axon seals off and swells; the distal portion degenerates 3. *Neurolemmocytes form a regeneration tube and secrete nerve growth factors* 4. axon regenerate and remyelination occurs 5. Reinnervation of the effector (skeletal muscle fibers) of the axon - Regeneration only occurs in PNS because: • Oligodendrocytes do not release growth factor. • The large number of axons in the CNS interfere with regeneration. • Astrocytes may obstruct axon growth - can also happen in peripheral processes of unipolar neurons

Maxillary branch (V2)

Pathway: through foramen rotundum

Ophthalmic branch (V1)

Pathway: through superior orbital fissure

Left hemisphere

Processing: - language - numbers - reasoning

Right hemisphere

Processing: - musicality - space and pattern perception - insight - imagination - spatial relationships

Pia mater of spinal cord

attached to surface of spinal cord

Medial cord

formed from inferior trunk

Lateral cord

formed from superior and middle trunk

Dorsal root ganglion

house *sensory* neuron cell bodies (which are entering the vertebral canal)

Ventral roots

house cell bodies of *motor* neurons (which are leaving the vertebral canal)

Epithalamus

includes pineal gland, which secretes melatonin to *regulate day/night cycles* (circadian rhythm).

Gluteal nerves

innervate muscles in the gluteal region

Obturator nerve

innervates most of the muscles in the medial thigh - runs through obturator foramen and stops just before knee - adduct thigh at hip - patch of skin on the upper inner thigh will be numb if damaged

Polysynaptic reflex

interneuron facilitates sensory-motor communication

Cauda equina

like a "horse's tail" being comprised of nerve roots from the inferior end of the spinal cord.

Anterior funiculus

located anteriorly between the anterior horns

Lateral funiculus

located laterally

Posterior funiculus

located posteriorly between the dorsal horns

Arachnoid mater of spinal cord

loose around spinal cord with subacrachnoid space containing CSF

Sensory System

receives sensory information from receptors and sends it to the CNS

Motor System

sends impulses from CNS to muscles or glands

Perineurium

surrounds a fasicle of neurons

Endoneurium

surrounds a single axon around the myelin

Epineurium

surrounds bundles of fasicles of neurons (nerves)

Filum terminale

strand of pia mater off end of conus.

Dura mater of spinal cord

thick outer layer of spinal cord

Periosteal dura

top layer of dura

Spinal (mixed) nerve

where the dorsal and ventral roots come together

Synapse

• "the functional contact of a nerve cell with another nerve cell or effector." • It is where an impulse is relayed to another neuron or effector. • It is typically located between the axon terminal, or telodendria, and the effector or another neuron.

Cerebrum

• 2 hemispheres • Location of conscious though and complex intellectual function • Allows us to comprehend the world around us • The center of reasoning • Stores our memories • Allows us to be aware of sensory input • Is where voluntary movement is initiated - CN I is the only cranial nerve attached here

Astrocytes

• Blood-brain barrier • Regulates tissue fluid composition • Fill space from dead neurons • Provide structural network • Can directly influence function of neurons with calcium release. - assist with neuronal development - star-shaped - *supports and nourishes neurons in CNS*

Glial cells

• Found in CNS and PNS. • Smaller than neurons. • Capable of cell division. • They protect, nourish and provide supporting network for neurons. • There are many more glial cells than neurons. • There are numerous types with various functions.

Ependymal cells

• Line the ventricles (internal cavities) of the brain to form the choroid plexus • Help form choroid plexus (for production of (CSF) - cuboidal epithelial cells

Spinal cord

• Link between brain and rest of body. • Has spinal nerves which carry motor and sensory stimuli. • Is a continuous cord of tissue with segmental features

Satelite cells

• Located around cell bodies of PRG • Regulate nutrients/wastes - unipolar - *arrange themselves around neuronal cell bodies in ganglia* *PNS*

Nerve plexus

• Network of anterior rami of spinal nerves. • Allows the nerves in our bodies to be formed from various levels of spinal nerves. • The two largest nerve plexuses are the brachial plexus and lumbosacral plexus.

Microglia

• Small cells - slender processes extending from cell body • *Wander through CNS and "clean up" through phagocytosis*

Devlopment of the Brain

• The central nervous system begins as the neural tube. • By the *4th week*, the primary vesicles form: - *Prosencephalon* - *Mesencephalon* - *Rhombencephalon* - By 5th week secondary vesicles form

Neurolemmocyte (Schwann cell)

• Wrap around axons in *PNS* to provide myelin to a portion of an axon - similar to oligodenrocytes because they lay down the same myelin - neurolemmocytes commit themselves to myelinate one small part of an axon - participate in the repair of damaged peripheral nerves - node of Ranvier is where 2 adjacent cells meet

Cerebrospinal fluid

• clear and colorless • located within ventricles and subarchnoid space - passes through arachnoid villi and enters the blood of the dural sinus • provides buoyancy for the brain • is a shock‐absorber for the brain • helps transports nutrients and chemical messengers to the brain and remove waste products.

Oligodendrocytes

• large cells with bulbous body - Slender extensions wrap around axons providing myelin in *CNS* • Myelinate more than one axon