Anatomy Unit 2 (Chapter 13-17)

Looking at the gross anatomy of the spinal cord, how is it structured and organized? What are some of its primary features/structures?

- Extends from skull to level of L1-L2 - terminates at conus medullaris - inferior nerve roots called cauda equina - filum terminale runs from conus medullaris to coccyx within the coccygeal ligament

How are the neurons organized within the ANS? You should know the basic organization of the various ganglia with respect to the spinal cord and the various interconnecting nerve rami.

- Preganglionic neurons in lateral gray horns of spinal segments T1-L2 - ganglia near spinal cord - preganglionic fibers release ACh (excitatory) stimulating ganglionic neurons - target organs - most postganglionic fibers release NE at neuroeffector junctions - triggers fight or flight response Ganglia - sympathetic chain ganglia - located lateral to the vertebral column on both sides - collateral ganglia - destination of most fibers inferior to T4 - preganglionic fibers go through sympathetic chain and travel via splanchnic nerves to collateral ganglia - celiac ganglion - superior mesenteric ganglion - inferior mesenteric ganglion - located anterior to the vertebral column adrenal medulla - some preganglionic fibers pass through sympathetic chain and celiac ganglion to synapse directly with chromaffin cells in adrenal medulla

What are the spinal meninges? What do they do? How are they structured?

- Spinal meninges provide protection, stability, and shock absorption to protect the cord - Dura Mater (strong mother) - most dense, superficial layer, contains epidural space - Arachnoid Mater (spider mother) - middle layer, contains subdural space and subarachnoid space filled with collagen, elastic fibers, cerebrospinal fluid - Pia Mater (gentle mother) - deep layer, firmly bound to underlying neural tissue, includes blood vessels that supply spinal cord

What are the different parts of the diencephalon, and what roles do they serve?

- epithalamus - roof of third ventricle, extensive choroid plexus, pineal gland secretes melatonin - thalamus - serve as relay centers for sensory and motor pathways - Info relayed to cerebrum or brain stem; nuclei grouped based on where they relay information to/from - act a information filter - coordinate motor activities at both conscious and subconscious levels - hypothalamus -Subconscious control of muscle contractions associated with rage, pleasure, pain, and other intense emotions -Adjusts and coordinates activities of auto-nomic centers in other areas of the brain -Coordinates activities of nervous andendocrine systems -Secretes antidiuretic hormone and oxytocin -Production of behavioral drives (e.g., thirst) and emotions -Regulation of body temperature -Control of circadian rhythms

What are the different ways in which neurons can be classified based on function?

- from receptor to CNS: sensory Motor Neurons - from CNS to Skeletal Muscle: somatic motor neurons - from CNs to Visceral Effectors (smooth muscles, glands, cardiac muscle, adipose tissue): visceral motor neurons - between CNS and PNS: interneurons

How does a chemical synapse work?

- neurotransmitters are stored in vesicles in axon terminals of presynaptic neuron - action potential causes neurotransmitters to be released via exocytosis into the synaptic cleft - neurotransmitters diffuse across the cleft and bind to receptors on the postsynaptic neuron, triggering a response (+/-)

What roles do each of the different parts in the mesencephalon serve?

- superior colliculi (visual input) - inferior colliculi (auditory input)

How does an electrical synapse work?

- utilize gap junctions - found in parts of the brain, between some glial cells, and in embryonic nervous tissue

What is unique about the pathway by which the adrenal medulla is innervated?

-some preganglionic fibers pass through sympathetic chain and celiac ganglion to synapse directly with chromaffin cells in adrenal medulla - chromaffin cells are essentially modified (post) ganglionic neurons that release epinephrine and norepinephrine into bloodstream

What are the different ways in which neurons can be classified based on structure?

1. Anaxonic Neuron - more than two processes, axons can't be distinguished from dendrites, rare: only in brain and spinal cord 2. Bipolar Neuron - have two process separated by the cell body, not super common 3. Pseudounipolar Neuron - single elongte process with the cell body off to one side, not common 4. Multipolar Neuron - have more than two processes, single axon and multiple dendrites

What are the six major divisions of the brain?

1. Cerebrum 2. Diencephalin 3. Mesencephalon (midbrain) 4. Pons 5. Medulla Oblongata 6. Cerebellum

What are the prominent features of the cranial meninges, and what roles do they play?

1. Dura Mater - outer layer of tough fibrous connective tissue 2. Arachnoid mater - middle layer with web-like network of collagen and elastic fibers 3. Pia mater - inner layer, follows contours of brain and extends deep into sulci

What are the different lobes of the cerebrum?

1. Front Lobe 2. Temporal lobe 3. insula 4. Parietal lobe 5. Occipital lobe

What are the major areas of the cerebral cortex? What do they do, and where are they located?

1. Primary motor cortex - surface of precentral gyrus, pyramidal neurons of corticospinal tracts, voluntary motor control 2. Premotor cortex - controls learned motor skills (walking) - may control several muscles at same time or sequentially 3. Speech center (broca's area) - motor speech area, superior to lateral sulcus and anterior to precentral gyrus, usually only on left side

What are the three anatomical principles that dictate the arrangement of neurons within sensory tracts?

1. Sensory Modality Arrangement - sensory fibers arranged according to stimulus - example: information dealing with fine touch will be carried within one sensory tract while information dealing with pain will be carried within another 2. Medial-Lateral Rule - most complex - fibers coming from more inferior travel more medially within a sensory tract than sensory nerves entering the cord at a more superior level 3. Somatotopic Arrangement - fibers arranged within individual tracts according to where their site of origin within the body is - sensory fibers coming from particular regions of the body -> upper limb, form a tract containing organized bundles of sensory fibers from the hand, wrist, forearm, and arm

What five steps are involved in a reflex arc?

1. Stimulation and activation of a receptor 2. Activation of a sensory nerve 3. information processing in CNS 4. Activation of a motor neuron 5. Response by effector

How many neurons are typically present in sensory tracts?

3 neurons 1. First Order Neuron - extend into periphery, detects stimulus, delivers info to CNS, cell body in dorsal root ganglion, enters through dorsal root, travels into brain and synapses on second-order neurons 2. Second Order Neuron - neither sensory or motor, fully in gray matter (cell bodies), axon crosses over to opposite side of body 3. Third Order Neuron - carries sensory info from thalamus to appropriate sensory area of the cerebral cortex

What are the different forms of cerebral white matter, and what roles do they serve?

Association fibers - connect regions within the same hemisphere (include arcuate fibers and longitudinal fasciculi) Commissural fibers - connect cerebral hemispheres (corpus callosum) Projection fibers - connect cerebrum to other regions of the brain and cord

How does the autonomic nervous system (ANS) differ from the somatic nervous system (SNS)?

Autonomic Nervous System - the system of neurons that innervates smooth muscle, cardiac muscle and glands Somatic Nervous System - skeletal muscle BOTH - include motor neurons DIFFER 1. Different effectors - SNS: skeletal muscle - ANS: smooth muscle, cardiac muscle, and glands 2. Different neurotransmitter effects - SNS: excitatory only - ANS: may be excitatory or inhibitory (depending on the receptor type) 3. Different efferent pathways and ganglia - SNS: single neuron from CNS to effector (lower motor neuron) - ANS: two neurons from CNS to effector --> Preganglionic neuron: cell body in lateral horn, lightly myelinated preganglionic fiber exits cord via vental root, terminates in autonomic ganglion --> (post)ganglionic neuron: cell body in autonomic ganglion, unmyelinated postganglionic fiber exits autonomic ganglion, terminates at effector

What is the basic route of a preganglionic fiber in the sympathetic nervous system? What are the different destinations possible for a preganglionic fiber entering a sympathetic chain ganglion? What are the routes a postganglionic fiber may take when exiting the sympathetic chain ganglion?

Basic Route: - exit cord via ventral root - pass into spinal nerve - pas into white ramus communicans Destinations Possible: 1. Synapse with (post) ganglionic neuron in same chain ganglion 2. Ascend/descend sympathetic chain to synapse in different chain ganglion 3. pass through chain ganglion to synapse in collateral ganglion Postganglionic Routes: - enter dorsal or ventral ramus of adjacent spinal nerves via gray ramus communicans - some exit chain directly via sympathetic nerves (example: cervical sympathetic ganglia)

You should know the names, numbers, and basic functions of the 12 pairs of cranial nerves, as well as whether the nerve is sensory, motor, or mixed. You should also understand the additional terms associated with each cranial nerve.

CN I - Olfactory Nerve - from nasal mucosa through cribriform foramina to olfactory - olfactory tract carries information to olfactory cortex - sensory (special sense of smell) CN II - Optic Nerve - from retina through optic canals to optic chiasm - Medial fibers of each nerve cross at optic chiasm, while lateral fibers stay on the same side - reorganized fibers (optic tracts) continue to thalamus - sensory (special sense of vision) CN III - Oculomotor Nerve - from mesencephalon through superior orbital fissure to 4 (of 6) extrinsic eye muscles and the muscles that raise the eyelids - also sends preganglionic fibers to ciliary ganglion for control of intrinsic eye muscles - motor (somatic and visceral) CN IV - Trochlear Nerve - from mesencephalon through superior orbital fissure to superior oblique muscle - smallest CN (fewest axons) - motor (somatic) CN V - Trigeminal Nerve - ophthalmic division: sensory for orbits, nasal cavity, forehead - maxillary division: sensory for nose, cheeks, upper jaw, teeth - mandibular division: mixed with motor fibers for jaw muscles and sensory fibers for tongue, lower jaw, teeth CN VI - Abducens Nerve - from pons through superior orbital fissure to lateral rectus muscle - motor (somatic) CN VII - Facial Nerve - from geniculate ganglion and pons through internal acoustic meatus and stylomastoid foramen to facial muscles, some salivary glands, lacrimal glands, and anterior taste buds - mixed (sensory for taste, visceral motor for glands, somatic motor for facial nerves CN VIII - Vestibulocochlear Nerve - sometimes called auditory or acoustic nerve - from pons and medulla through internal acoustic meatus to cochlea, vestibule, and semicircular canals - splits into vestibular nerve and cochlear nerve - sensory (hearing, balance, and equilibrium) CN IX - Glossopharyngeal Nerve - from medulla through jugular foramen to posterior taste buds, pharynx, and salivary glands - mixed (sensory for taste, visceral motor for glands, somatic motor for pharynx) CN X - Vagus Nerve - from medulla through jugular foramen to external acoustic meatus, pharynx, larynx, and viscera - mixed (sensory for viscera and external acoustic meatus; visceral motor for respiratory, cardiovascular, and digestive systems; somatic motor for pharynx and larynx) CN XI - Accessory Nerve - called spinal accessory nerve - from medulla and spinal root through jugular foramen to pharynx, larynx, trapezius, and sternocleidomastoid - motor (somatic) CN XII - Hypoglossal Nerve - from medulla through hypoglossal canal to tongue muscles - motor (somatic)

What are the characteristics and functions of the different types of neuroglia? Where would you find each of them?

CNS Neuroglia - Ependymal cells -> line cavities with cerebrospinal fluid (CSF) and produce and circulate cerebrospinal fluid - Microglia -> phagocytic immune cells that engulf microbes/debris and get rid of pathogens - Astrocytes -> most neurons of glial cells and provides structural support, regulate ISF, maintain BBB, and repair damaged tissue - Oligodendrocytes -> provide structural support, myelinate neuronal axons (one cell can cover multiple internodes on multiple neurons), myelinating the axons in CNS insulate neurons so that signals can send faster PNS Neuroglia - Satellite Cells -> surround neuronal cell bodies in peripheral ganglia and isolate neuron from other stimuli and regulate exchange of nutrients and waste products with ISF - Schwann Cells -> form myelin sheaths around segments of neuronal axons (one cell can only cover one small internode), layer after layer of myelin sheaths (phospholipid) around segments or neuronal axons, give rise to white matter in PNS, myelinate part of axon

How does the central nervous system (CNS) begin to develop in the earliest embryonic stages?

CNS begins when ectoderm thickens dorsally to become a neural plate - a crease develops along the neural plate, creating neural groove -> the edges gradually come together dorsally, forming a hollow neural tube with a neurocoel

How does the pattern of divergence differ between the sympathetic and parasympathetic divisions? What effect does this have on the types of responses?

Divergence: - Sympathetic - extensive divergence -> more diffuse response - Parasympathetic - less divergence -> more specific response

What are the different branches of a spinal nerve? What areas of the body do they innervate?

Dorsal Ramus - neck and back Ventral Ramus - ventral body and limbs Rami Communicants - connect spinal nerve to sympathetic ganglia - white ramus communicans - myelinated preganglionic fibers - gray ramus communicans - unmyelinated postganglionic fibers

How is a spinal nerve structured?

Each spinal segment is associated with a pair of spinal nerves - several dorsal rootlets join to form a dorsal root, which is associated with a dorsal root ganglion (sensory) - several ventral rootlets join to form a ventral root (motor) - dorsal root and ventral root come together to form a spinal nerve that passes through the intervertebral foramen

How is a peripheral nerve structured?

Epineuron - covers peripheral nerve Perineurium - around one fasicle

For each discussed sensory and motor tract, you should compare and contrast: a. the number and arrangement of the different neurons b. where the neurons decussate and terminate c. what types of information the neurons carry

Four Sensory (ascending) Tracts - from the spinal cord to the brain, conduct sensory impulses upward through chains of three successive neurons 1. Posterior Columns a. 3 neurons - First order synapses on second order which synapse on third order b. decussates to contralateral side and ascends to thalamus from second order; terminates at primary somatosensory cortex c. fine-touch, vibration, pressure, proprioception sensations from right side of body 2. Anterior Spinothalamic Tracts a. first order - from periphery to dorsal horn at level of entry, synapse on second order second order neurons - ascend to thalamus, start in spinal cord instead of brain, ends within thalamus third order - from thalamus to primary somatosensory cortex b. decussates at second order at level of entry; terminates at primary somatosensory cortex c. crude touch and pressure sensations on right side of body 3. Lateral Spinothalamic Tracts a. first - from periphery to dorsal horn at level of entry, second - decussate at level of entry and ascend to thalamus, third order - from thalamus to primary somatosensory cortex b. decussates at level of entry at second order neuron, terminates at primary somatosensory cortex c. pain and temperature sensations from right side of body 4. Spinocerebellar Tracts a. first order - from joints/muscles to dorsal horn, second order - some decussate at level of entry, ascend to cerebellum, and decussate again within cerebellum to return to ipsilateral side, some remain on ipsilateral side as they ascend to cerebellum -> no third order b. decussates at level of entry at second order, but some decussate again to ipsilateral side in cerebellum c. proprioceptive input from golgi tendon organs, muscle spindles, and joint capsules Motor (descending) Tracts - from the brain to the spinal cord or from one region of the spinal cord to a more inferior region 1. Lateral Corticospinal tract a. Upper neurons synapse with lower neurons or anterior horns of spinal cord b. 85% of axons decussate in pyramids (thick bands of upper-motor neurons) c. provides conscious, voluntary control 2. Anterior Corticospinal Tracts a. synapse with lower-motor in brainstem or anterior horns of spinal cord b. 15% of axons enter on ipsilateral side and decussate at targeted segment c. provides conscious, voluntary control over skeletal muscles

What are the different ways that a reflex can be classified? What are some examples of each type?

Innate: sucking Learned: walking Somatic: sneezing Visceral: swallowing Monosynaptic: patellar knee jerk Polysynaptic: crossed extensor Spinal: stretch reflex Cranial: blinking

What are the different ventricles of the brain, and how are they interconnected?

Lateral Ventricles - within cerebral hemispheres; separated by septum pellucidum Third Ventricle - in diencephalon; separated by septum pellucidum Cerebral Aqueduct - canal within the mesencephalon; connects third ventricle with... Fourth ventricle - begins within pons and cerebellum; connects central canal of spinal cord

What does it mean to say that the cerebral hemispheres are specialized? What types of activities are usually most dominant on each side?

Left hemisphere - language, reading, writing, speaking, mathematics, logical/analytical reasoning Right hemisphere - spatial perception, intuition, facial recognition, artistic/musical skills, emotion two hemispheres connected by corpus callosum

What is a nerve plexus? What areas do each of the discussed plexuses innervate? What are some of the major nerves extending from each of these plexuses?

Nerve plexus = ventral rami from C1-T1 and T12-S4 branch and join together multiple times, forming complex networks called nerve plexuses Cervical Plexus (C1-C5) - innervates muscles and skin of neck, shoulder, and diagram - phrenic nerve (C3-C5) innervates diagram - supplies branches to CN XI (accessory) and CN XII (hypoglossal) Brachial Plexus (C5-T1) - larger and more complex - innervates shoulder, some thorax muscles, and the upper limbs - includes nerves: - axillary nerve - musculocutaneous nerve - radial nerve - median nerve - ulnar nerve Lumbar Plexus (T12-L4) - innervates abdomen, genitals, thigh, and lower leg - includes femoral and obturator nerves Sacral Plexus (L4-S4) - innervates genitals, gluteal muscles, thigh, and lower leg - includes sciatic and pudendal nerves

How does the blood-brain barrier work, and why is it important? What glial cells are involved in forming this barrier? In what areas of the brain do we not see such impermeable capillaries?

Neural tissue of CNS is separated from the general circulation by the blood-brain barrier - Ensures a stable environment for the brain - Tight junctions of capillary endothelial cells prevent diffusion of H2O soluble compounds between cells (lipid-soluble compounds can diffuse through cells) - Astrocytes - secrete chemicals that regulate the active and passive transport of other substances Exceptions: hypothalamus, pineal gland, and choroid plexuses have capillaries with higher permeability

What are the different ways in which neurons and neuronal pools can be organized into neural circuits?

Neuronal pool - a group of interconnected neurons with one or more specific functions Neural circuit - the way in which the neurons within a pool are arranged

How is a typical neuron structured? What roles are played by each part of a neuron?

Neurons - specialized to transmit electrical signals Dendrites -> stimulated by other cells or environment; convey signals to cell body Cell body -> contains nucleus and organelles, synthesizes and packages neurotransmitters -> nuclei (CNS) and ganglia (PNS) Axon -> conducts impulses from cell body to axon terminals -- release neurotransmitters -> bundled into tracts (CNS) and nerves (PNS) - axon terminal -> site of release chemical signal - axon collateral -> branches off axon

How are neurons organized within the CNS and PNS?

PNS - Gray matter = ganglia - collections of neuron cell bodies in the PNS - White matter = nerves - bundles of axons CNS - Gray matter = neural cortex - gray matter on the surface of the brain and nuclei - collections of neuron cell bodies in the interior of CNS and centers - collections of neuron cell bodies in the CNS: each has specific processing functions -> higher centers are the most complex in the brain - White matter = tracts - bundles of CNS axons sharing a common origin and destination columns - several tracts forming an anatomically distinct mass

How does the arrangement of the parasympathetic division differ from that of the sympathetic division? What cranial nerves carry preganglionic parasympathetic fibers?

Parasympathetic vs. Sympathetic - arises from cranial and sacral regions of CNS (Sympathetic = thoracolumbar region of spinal cord) - long preganglionic fibers, short postganglionic fibers (short preganglionic fibers, long post ganglionic fibers) (extensive less divergence -> more specific response) divergence -> more diffuse response)

In fairly basic terms, how do the patellar and crossed extensor reflexes work?

Patellar (knee jerk) reflex -> example of monosynaptic spinal reflex known as stretch reflex 1. stimulus hits tendon 2. receptor (muscle spindles) 3. send sensory through dorsal root to spinal cord 4. synapses to motor neurons 5. exits through ventral root 6. stimulates muscle to contract Crossed Extensor Reflex 1. Painful stimulus activates nociceptor 2. Primary sensory neuron enters spinal cord and diverges 3. one collateral activates ascending pathways for sensation (pain) and postural adjustment (shift in center of gravity) 4. Withdrawal reflex pulls foot away from painful stimulus 5. crossed extensor reflex supports body as weight shifts away from painful stimulus

What are all the different divisions of the nervous system, and how do they relate to one another? What are the main functions for each of these different divisions?

Peripheral Nervous System -> sensory (afferent or towards CNS from receptors) and motor (efferent or towards tissue from CNS) Two different motor: - Somatic Nervous System -> skeletal muscle - Autonomic Nervous System -> smooth, cardiac muscles, and gland Two divisions of Autonomic Nervous System: - sympathetic division: fight or flight - parasympathetic division: resting and digesting Central Nervous System -> integrative and control centers - brain and spinal cord

How does somatic motor control work?

Planning Stage: conscious decision to move is made, info is relayed from frontal lobes to motor association areas, these areas relayinfo to cerebellum and basal nuclei Movement: motor association areas send instructions to primary motor cortex as movement begins, feedback from basal nuclei and cerebellum modifies those commands, and output along conscious and subconscious pathways directs involuntary adjustments in position and muscle tone

What are the primary and secondary vesicles that develop in an early embryo brain, and what regions of the brain do they develop into by birth?

Primary brain vesicles (3 week embryo) - primary vesicles: prosencephalon, mesencephalon, rhombencephalon Secondary brain vesicles (6 week embryo) - secondary: telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon

What is amyotrophic lateral sclerosis (ALS)? How does it affect the nervous system and muscular control?

Rapidly progressive degenerative disease affecting upper and lower motor neurons effects: loss of motor control, muscle weakness, loss of muscle tone, eventual muscle atrophy, sensation and intellect not impaired

How can an axon in the PNS potentially recover following an injury?

Schwann clls contribute to repair of damaged axons via Wallerian Degeneration - not full proof 1. Fragmentation of axon and myelin occurs in distal stump 2. Schwann cells form cord, grow into cut, and unite stumps. Macrophages engulf degenerating axon and myelin 3. Axon sends buds into network of Schwann cells and then starts growing along cord of Schwann cells 4. Axon continues to grow into distal stump and is enfolded by schwann cells

What roles do the different nuclei in the pons serve?

Sensory and motor nuclei for CN V, VI, VII, and VIII nuclei process/relay commands from cerebellum

What are the similarities and differences between spinal and epidural anesthesia?

Similarities: - injection of medication near cord to numb lower body - avoid risks of general anesthesia - allow patient to be awake Differences: - space of injection (subarachnoid space vs. epidural space) - site of injection (spinal must be inferior to L2; epidural can be more superior) - inclusion of catheter for epidural - pain relief occurs more quickly with spinal - typically no significant muscle block with epidural - epidural doesn't go through dura mater, can inject higher than L2, takes awhile for pain reduction

How do descending motor pathways differ between the somatic nervous system and the autonomic nervous system?

Somatic Nervous System - Upper motor neurons in primary motor cortex - Lateral corticospinal tract : - anterior corticospinal tract - subconscious motor pathways - skeletal muscle Autonomic Nervous System - visceral motor nuclei in hypothalamus - glands, smooth muscle, cardiac muscle

What are the two main divisions of the ANS? What roles are played by each division? What are the basic anatomical differences between the two divisions?

Sympathetic Division - E -> emergency, excitement, exercise, and embarrassment, blood pulled away from viscera and skin and shunted to heart and skeletal muscles - arises from thoracolumbar region of spinal cord Parasympathetic division - d division - digestion, defecation, and diuresis - conserves energy and promotes sedentary activities - arises from cranial and sacral regions of CNS

What are the different kinds of synapses that a neuron can form?

Synapse - junction that mediates information transfer between a neuron and another cell - neuron to neuron (presynaptic neuron to postsynaptic neuron) - Neuron to muscle (neuromuscular junction) - neuron to gland (neuroglandular junction

What are tracts? What are the basic differences between sensory (ascending) and motor (descending) tracts?

Tracts - collection of axons in CNS (brain and spinal cord) - communication between CNS and PNS, and peripheral organs involve tracts that relay sensory and motor information between the periphery and higher brain centers - conduct sensory impulses upward through chains of three successive neurons - Sensory (Ascending) tracts -> from spinal cord to brain - Motor (descending) tracts -> from the brain to the spinal cord or from one region of the spinal cord to a more inferior region

What are the different parts of the cerebellum? What functions does the cerebellum serve?

Two cerebellar hemispheres -Functions: - Receives proprioceptive information from spinal cord and monitors all visual, tactile, balance, and auditory sensations -Adjusts postural muscles -Fine tunes and coordinates both voluntary and involuntary movements

What are the key differences between white matter and gray matter?

White matter -> myelinated Gray -> unmyelinated (mostly dendrites and cell bodies of neurons)

What are the functions of cerebrospinal fluid (CSF)? How and where is CSF produced? What roles do ependymal cells play in the choroid plexus? What is the pattern of CSF circulation through the CNS?

a lymph-like fluid found in and around the brain and spinal fluid, prevents contact between neural tissues Supports and cushions brain transports nutrients, chemical messengers, and waste products - Transports nutrients, chemical messengers, and waste products - Produced by choroid plexus (produces cerebrospinal fluid) of each ventricle - Highly permeable capillaries, but free exchange between capillaries and CSF is prevented - Ependymal cells essentially secrete CSF into ventricles, while also removing waste products and regulating composition of CSF

What types of neurons do the dorsal and ventral roots carry?

dorsal: carry sensory neurons ventral: carry motor spinal nerve: dorsal and ventral root come together and pass through the intervertebral foramen = mixed nerve

How does dual innervation work in the ANS? What are the different types of responses associated with each division?

most organs innervated by both divisions of the autonomic nervous system

What roles do the different nuclei in the medulla oblongata serve?

nuclei may be: - relay stations - sensory/motor nuclei associated with cranial nerves (VIII, IX, X, XI, and XII

How are neurons associated with the collateral ganglia organized?

preganglionic fibers go through sympathetic chain and travel via splanchnic nerves to collateral ganglia - splanchnic nerves connect chain and collateral

What does it mean to say that a spinal nerve is a mixed nerve?

sensory and motor

What is a dermatome?

sensory fibers in each pair of spinal nerves monitor a specific region of the body surface - illustrate segmental division of labor - clinically important because damage to either a spinal nerve or dorsal root ganglion produces a characteristic loss of sensation in specific areas of the skin

What is decussation?

things that being sensed on one side is processed on either side -> goes to thalamus

Looking at the cross-sectional anatomy of the spinal cord, what are its major features? What makes up the gray matter and white matter of the spinal cord, and how are these structures organized?

•Key features include the central canal, posterior median sulcus, and anterior median fissure •Gray matter - contains nuclei and short interneurons -Posterior (dorsal) gray horn - sensory nuclei -Lateral (intermediate) gray horn - autonomic motor nuclei -Anterior (ventral) gray horn - somatic motor nuclei •White matter - contains tracts of myelinated axons -Posterior white column -Lateral white column -Anterior white column