Visceral Sensory Neurons: Send info about chemical changes, stretch, temperature, etc. Around viscera, cell bodies located in dorsal root ganglia & sensory ganglia of cranial nerves.
Visceral Reflex: Have some components as somatic reflex arcs: receptor, sensory neuron, integration center, motor neurons & 3 main differences.

1. Visceral Reflex Arc has 2 consecutive neurons in the motor pathway
2. Afferent Fibers are **Visceral Sensory neurons
3. Effectors are smooth, cardiac muscles & glands rather than skeletal muscles.
   
   

Neurotransmitters: ACh & NE. ACh is released by cholingeric fibers. All ANS preganglionic axons & ALL ps postganglionic azons NE is released by adrenergic fibers at; all sympathetic postganglionic axons.

Cholingeric Receptors- 2 types binds ACh; 1 Nicotinic Receptors, 2 Muscarinic Receptors
Adrengic Receptors- 2 Major classes responds NE, Alpha & Beta Receptors.

PS & S Interactions: Most visceral organs have dual innervation. AP's continually fire down axons of both, producing antagonistic interaction. Both ANS divisions are partially active, resulting in basal s & ps tone.

Control of ANS functions: ANS is under control of CNS centers.
Hypothalamus- is generally main integrative center of ANS activity. Cerebral input may modify ANS but does subconsciously. Works through limbic system structures on hypothalamic centers.

Homeostatic Imbalance:
Autonomic Neuropathy: Damage to autonomic nerves that is a common complication of diabetes mellitus. Other frequent symptoms include dizziness after standing suddenly, urinary incontinence, sluggish eye pupil reactions, etc. Best way to prevent diabetic neuropathy is maintain good blood glucose.
Hypertension: Overactive sympathetic vasoconstrictor response to stress. Heart works harder & artery walls are subject to increased wear & tear. Treated with adrergic receptor-blocking drugs.
Rayaud's Disease: Painful, exaggerated vasoconstriction in fingers & toes. Digits turn pale, then cyanotic, treated with vasodilators.
Autonomic Dysreflexia: Life-threatening, uncontrolled activation of autonomic neurons in quadriplegics & people with spinal cord injuries about T6. Blood pressure skyrockets, posing increasted risk for stroke.

SPINAL NERVES: Supply all body parts except head & neck.
8 Pairs of C nerves + 12 Pairs of T nerves + 5 Pairs of L Nerves + 5 Pairs of S Nerves + 1 Pair of C
Both Ventral & Dorsal Roots are branched medially as rootlets that then join laterally from spine nerve.
Innervation of Specific Body Regions: Innervation of Dermatones
Dermatones: Area of skin innervated by cutaneous branches of single spinal nerves. All except C1 participate in dermatones. Most overlap, so destruction of a single spinal nerve will not cause complete numbness.

Peripheral Motor Endings: Motor endings, PNS elements that activate effectors by releasing neurotransmitters.
Innervation of SM: At neuromuscular junction, ACh is released when nerve impluses reached Axon terminal. ACh binds to receptors, resulting in movement of Na+ & K+, Depo of muscle cell, at NE, spreads to adjacent areas of sarcolemma triggers of opening of Na+ voltage gated channels,r esults in an AP, muscle contraction.

Innervation of Visceral Muscle & Glands: Autonomic motor endings visceral effectors are simpler than somatic junction. Branches form synapses en passant*, with effector cells via varicosities. Ach & NE act indirectly via 2nd messagers, visceral slower than somatic.

Inborn (intrinsic) Reflex: Rapid, involuntary, predictable motor response to stimulis. Can be modified by learning & conscious effect. Learned (acquired) Reflex: Results from practice or repetition, Ex: driving skills.

Reflex Arc 1. Receptor: Site of stimulus action 2. Sensory Neuron: Transmits afferent impulses to CNS. 3. Integration Center: Either monosynaptic or polysnaptic. 4. Motor Neuron: Conducts efferent impulses from integration center to effector organ. 5. Effector: Muscle fiber or gland cell that responds to efferent impulses by contracting or secreting.
Reflexes are classfied functionally as: Somatic Activate Skeletal Muscle; Autonomic: Activates visceral effector

Gyri: Hills
Sulci: Shallow grooves, seperates 5 lobes
Major Sulci: Central Sulcus, Parieto occiptal Sulcus, Lateral Sulcus
Fissures: Deep grooves
Longitudinal Fissure: Separates 2 hemispheres
Transverse Fissure: Separates cerebrum & Cerebellum
5 Lobes: Frontal, Temporal, Parietal, Occiptal, & Insula.
Gray Matter: Short, nonmyelinated neurons & cell bodies
White Matter: Myelinated & nonmyelinated axons
Features and Changes of Pattern

1. Spinal cord exhibits this basic pattern, however pattern changes with ascent into brain stem; 2. Brain stem has additional gray matter, nuclei scattered withing white matter; 3. Cerebral hemispheres & cerebellum contain outer layer of gray matter called cortex, scattered areas of gray matter nuclei amid white matter.

Ventricles: Filled with CSF, lined by ependymal cells.
-Paired Lateral Ventricles, Cerebral Aqueduct, Fourth Ventricle, & third ventricle.
CEREBRAL CORTEX
Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding. 4 Components

1. Motor, Sensory, & Association Areas.
2. Each hemisphere is concerned with contra lateral side of body.
3. Lateralization of cortical function can occur in only one hemisphere
4. Conscious behavior involves entire cortex in one way or another.
   
   

MOTOR AREA: Located in the frontal lobe, controls voluntary movement, primary motor cortex in precentral gyrus, premotor cortex anterior to precentral gyrus. Brocas area anterior to inferior premotor area. Frontal eye field within & anterior to premotor cortex; superior to Brocas area, Primary Somatic Motor Cortex: All muscles can be mapped to area. Premotor Cortex: Helps plan movements, controls reptitous or patterned motor skills.
Brocas Area: Present in one hemisphere, motor speech area, directs muscles of speech production.

SENSORY AREAS: Areas of cortex concerned with sensation. Occur in parietal, insular, temporal & occiptal lobes. 8 main areas, visual areas, auditory areas, vestibular cortex, olfactory cortex, gustatory cortex, & visceral sensory area. primary somatosensory cortex & somatosensory association cortex.

Lateralization of cortical functioning:
Lateralization: Division of labor between hemispheres
Cerebreal Dominance: Refers to hemisphere dominate for language
LEFT HEMISPHERE: Controls language, math & logic
RIGHT HEMISPHERE: Visual spatial skills, intuition, emotion, artistic, & musical skills.

Homeostatic Imbalance- Damage to primary motor cortex, paralyzes muscles, paralysis occurs on opposite sides of body from damage.
Muscle strength or ability to perform discrete individual movements is not impaired; only control over moments is lost.
Damage to the primary visual cortex results in functional blindness. By contrast, people with damaged visual association area can see, but don't understand what they are looking at.

Cerebral Hemispheres: Cerebral White Matter, 2nd of the 3 basic regions of the hemispheres, responsible for communication between cerebral areas and cortex to lower CNS.

Basal Nuclei- 3rd of 3 basic regions of cerebrum, includes caudate nucleus, putaman, globus pallidus. Associated with subthalamic nuclei (Diencephalon) & substantia nigra (MidBrain). FUNCTIONS: Influence muscle movements, role in cognition & emotion, regulate intensity of slow or stereotyped movements, filter out incorrect inappropriate responses, inhibit unnecessary movements. (Parkisons & Huntington's DIsease are disorders of basal nuclei.

Diencephalon- Thalamus, Act as relay station for info coming into cortex. Sorts, edits, & relays ascending input such as impulses from hypothalamus, impulses from cerebellum, impulses for memory. Hypothalamus, located below thalamus, forms cap over brain stem, forms inferolateral walls of 3rd ventricle; The hypothalamus is the main visceral control & regulating center that is vital to homeostasis; Regulates body temp, hunger & satiety, water balance, sleep-wake cycle, controls ANS, & physical responses to emotions. Epithalamus, most dorsal portion of diencephalon, forms roof of 3rd ventricle, contains pineal gland, secretes melatonin that helps regulate sleep-wake cycle. Mammillary Bodies: Paired anterior nuclei that act as olfactory relay stations. Infundibulum: Stalk that connects to pituitary gland.

Suprachiasmatic nucleus of thalamus sets biological clock, controls endocrine system.

BRAIN STEM
Midbrain- Between diencephalon & pons
Cerebral Peduncle- 2 ventral bulges that contain pyramidal motor tracts.
Cerebral Aqueduct- Channel running through Midbrain that connects 3rd &4th ventricle.
Corpora Quadrigemina: Contains Superior & Inferior colliculi
Pons: Between MidBrain & medulla oblongata
4th Ventricle: Separates pons from cerebellum.
Medulla Oblongata- Blends into spinal cord at foramen magnum, contains 4th ventricle, continues central canal of sc. Choroid Plexus: capillary rich membrane that forms csf.

FUNCTIONS Cardiovascular: Cardiac center adjusts force and rate of heart, vasomotor center adjusts blood vessel diameter for BP. Respiratory: Generates respiratory rhythm, controls rate & depth of breathing, Other centers: vomiting, hiccups, swallowing, coughing sneezing.

CEREBELLUM: Dorsal to pons & Medulla
Connected by wormlike vermis
Contains thin cortex of gray matter with arbor vitae. Functions: Processes input form cortex, brain stem, & sensory receptors, to provide precise, coordinated movements of sm. Plays role in thinking, language, emotion, balance, & coordination.

Homeostatic Imbalance: Hypothalamic disturbances cause # of disorders such as: Severe body washing, obesity, sleep disturbances, dehydration, emotional imbalances, damaged by tumors, radiation, surgery, or trauma.

TRAUMATIC BRAIN INJURIES

• Concussion: Temporary alteration in functions
  -Contusion: Permanent Damage
  -Subdural/Subarachnoid Hemorrhage: Pressure from blood force brainstem through foramen magnum, resulting death
  -Cerebral Edema: Swelling of Brain, with traumatic head injury.
  
  

Ischemia: Tissue deprived of blood supply, leading to death of brain tissue, caused by blockage of cerebral artery by blood clot.
Hemiplegia: Paralysis on one side or sensory & speech deficits
Transient Ischemic Attacks: Temporary episodes of reversible cerebral ischemia
Tissue Plasminogen Activator: Only approved treatment for strokes.

Alzheimer's Disease: Progressive disease of brain, results in dementia
Memory loss, short attention span, disorientation, language loss, irritability, moodiness, confusion, hallucinations
Parkinson's Disease: Degeneration of Dopamine-releasing neurons. Basal nuclei deprived of dopamine becomes overactive, tremors at rest. Theories include mitochondrial abnormalities or protein degradation pathways. Treatment includes deep brain stimulation, gene therapy, stem cell transplants.
Huntington's Disease: Fatal hereditary disorder, accumulation of protein, causes flapping movements. Fatal withing 15 years of onset, treated with drugs, block dopamine effects.

HOMEOSTATIC IMBALANCE
Epileptic Seizure: Electrical discharges by groups of neurons. May lose consciousness, fall stiffly, and uncontrollable jerking. Occurs in 1% of population.
Meningitis: Inflammation of meninges, may spread to CNS, usually diagnosed by microbes.
Hydrocephalus: Blocks CSF circulation or drainage, increased pressure, skull bones fuse, causes head to enlarge, in adults, keeps rigidity of the skull, pressure leading to brain damage.

Spinal Cord: Enclosed in Vertebral Column, begins at foramen magnum, ends at L1 or L2.
Filum Terminale- Fibrous extension of conus covered with pia mater
Denticulate Ligaments- Extensions of pia mater that secure cord to dura mater.
Spinal Nerves- Part of PNS, 31 PAIRED ROOTS.
caude equina: collection of roots at inferior end of vertebral canal, anterior: ventral Median Fissure, Posterior: Dorsal Median Sulcus.

GRAY MATTER
Dorsal Horns: Interneurons that recieve somatic & visceral sensory input
Ventral Horns: Some interneurons, somatic motor neurons
Lateral Horns: Sympathetic neurons.
VENTRAL ROOTS: Bundle of motor neuron axons that exit the SC.
DORSAL ROOTS: Sensory input to cord, Dorsal Root Ganglia: cell bodies of sensory neurons.
Somatic Sensory, Visceral Sensory, Visceral Autonomic Motor, & Somatic Motor

WHITE MATTER: 3 directiosn; Ascending, descending, transverse
Divided into 3 white columns, dorsal, lateral & ventral. Each spinal tract composed of axons with similar destinations & functions.
NEURONAL PATHWAYS: Spinal tracts

1. Decussation: Pathways cross from one side of CNS to other
2. Relay: Consist of chain of 2 or 3 neurons
3. Somatotopy: Spatial relationship in CNS
   Symmetry: Pathways are paired symmetrically.
   
   

SPINAL CORD TRAUMA & DISEASES
Paresthesias: Damage to Dorsal Roots, sensory tracts, sensory function loss.
Paralysis: Damage to Ventral Roots, motor functions loss
Paraplegia: Transection between T1 & L1
Quadriplegia: Tramsection in cervial region
Spinal Shock: Transient period of function loss. caudal to lesions
Amyotrophic Lateral Sclerosis (ALS): Also called Lou Gehrigs Disease, destruction of ventral horn motor neurons, loss of ability to speak, swallow & breathe, death occurs in 5 years.

HOMEOSTATIC IMBALANCE
Cerebral Palsy: Neuromuscular disability, poorly controlled or paralyzed voluntary muscles.
Due to brain damage, lack of oxygen during birth, speech difficulties, motor impairment can be seen.

Anencephaly: Cerebrum & parts of brain stem never develop, child is vegetative; death occurs soon after birth.
Spina Bifida: Incomplete formation of vertebral arches, laminae & spinous processes are missing on at least one vertebrae.
Spina Bifida Occulata: Least serious, one missing vertebrae, causes no neural problec. Sacral Dimple or path of hair may hint at underlying anormaly.

CRANIAL NERVES
12 pairs of cranial nerves are associated with brain. 2 attaches to forebrain, rest with brain stem. Each numbered (I-XII) & named from rostal to caudal.

I- Olfactory Nerve: Sensory nerves of smell; fibers synapse in olfactory bulbs; terminates in primary olfactory cortex, purely sensory function

II- Optic Nerve: Arise from retinas; a brain tract; Pass through optic canals, converge & partially cross over at optic chiasma; optic tract goes through thalamus, optic radiation fibers run to occipital cortex.

III- Oculomotor Nerve: Fibers extend from ventral midbrain through superior orbital fissures to four of six eye muscles. Raises eyelids, direct eyeball, constrict iris & controlling lens shape.

IV- Trochlear Nerve: Fibers from dorsal midbrain enters orbits via superior orbital fissures to innervate superior oblique muscle. Primairly motor nerve that directs eyeballs

V- Trigeminal Nerve: Largest cranial nerves; fibers extend from pons to face; 3 divisons: Opthalamic-pass through superior orbital fissure, Maxillary- passes through foramen rotundum, Mandibular- pass through foramen ovale. Convey sensory impulses frmo areas of face.

VI- Abducens Nerve: Fibers from inferior pons enter orbits via superior orbital fissures. Primairly a motor, innverating

VII- Facial Nerve: Pons travel through acoustic meatuses & emerge through stylomastoid foramina to lateral aspect of face. Chief motor nerves of face with 5 major branches. Motor functions include facial expressions, parasympathetic impulses to lacrimal & salivary glands.

VIII- Vestibulocochlear Nerve: Afferent fibers from hearing receptors, & equilibrium receptors, mostly sensory function, motor component for adjustment

IX- Glossopharyngeal Nerve: Motor functions: innervate part of tongue & pharynx for swallowing & provide ps fibers to partoid salivary glands. Sensory functions: Fibers conduct taste & general sensory impulses from pharynx & posterior tongue.

X- Vagus Nerve: Only cranial nerves that extend beyond head & neck region. Fibers from medulla exit skull via jugular foamen. Most motor fibers are ps fibers that helps regulate activities of heart, lungs, & abdominal viscera.

XI- Accessory Nerve: Formed from c1 & c5, accessory nerves exit skull via jugular foramina to innervate trapezius & sternocleiodmastoid muscles.

XII- Hypoglossal Nerve: Fibers from medulla exit skull via hypoglossal canal. Innervate extrinsic muscles of tongue that contribute to swallowing and speech.