Lab Practical 1 PDF

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Lab Practical I Review Lab 1: Neurology – Histology, Brain Anatomy, Brain Dissection & Radiology Nervous System Divisions  Info via sensory receptors  integration center (Brain)  Effector organs activated Central Nervous System (CNS)  Brain & spinal cord  Integrative & control centers Peripheral Nervous System (PNS)  Cranial nerves & spinal nerves  Communication lines between the CNS & rest of body  Contains: o Sensory (Afferent) division- somatic & visceral sensory fibers, receptors  CNS o Motor (Efferent) division- motor nerve fibers; CNS  effectors  Somatic NS- voluntary; CNS  skeletal muscle  Autonomic NS (ANS)- involuntary; CNS  cardiac/smooth muscle & glands  Sympathetic NS- mobilizes body systems, “Fight or Flight”  Parasympathetic NS- conserve energy; house-keeping ANS Innervations  Parasympathetic NS innervation: o Eye, salivary glands, heart, lungs, stomach, pancreas, liver, gall bladder, bladder, genitals  Sympathetic NS innervation: o Eye, skin, salivary glands, lungs, heart, stomach, pancreas, liver, gall bladder, adrenal gland, bladder, genitals Nerves  PNS nerves (two groups): o Cranial nerves  12 pairs  communicate w/ brain & pass through foramina to face & neck  Nerve I most anterior to Nerve XII most posterior o Spinal nerves  31 pairs  Structure of a nerve: o Epineurium- outer covering o Perineurium- separates axons into bundles (fascicles) o Endoneurium- surrounds each axon o Myelin Sheath- insulates axons  PNS- made by Schwann cells  CNS- made by oligodendrocytes Nervous System Cells  Two types of cells:

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o Glial cells- Supportive role; protect & maintain tissue o Neurons- Communication cells; propagate & transmit electrical impulses Glial Cells: o Neuroglia- network of glial cells to anchor neurons in place o Isolate & support neurons w/ myelin to increase conduction velocity o In CNS, produce & circulate cerebral spinal fluid (CSF) of ventricles o Four CNS glial cell types:  Astrocytes- most abundant & versatile, exchanges between capillaries & neurons, determine capillary permeability, guide migration of young neurons & synapse formation, scaffold for dendrite & axon projections, ensure proper nutritional uptake by neurons, regulate neurotransmitter & potassium concentrations of ECF  Neuropil- fibrous substance that surround fibrous astrocytes of gray matter in cerebral cortex  Perivascular feet- in contact with blood vessels & neuronal surfaces  Microglia- small ovals with thorny processes that monitor nearby neurons health & migrate towards injured neurons  Ependymal cells- line central cavities of brain & spinal cord, form semipermeable barrier between CSF & cavities, have cilia to circulate CSF for brain & spinal cord cushion  Oligodendrocytes- line up along thicker neuron fibers & wrap them, producing insulating coverings (Myelin Sheath) o Two PNS glial cell types:  Satellite cells- surround neuron cell bodies, similar function to CNS astrocytes (exchange, capillary permeability, guide young neuron & synapse formation)  Schwann cells- surround & form myelin sheaths around larger nerve fibers in PNS, vital to regeneration of damaged peripheral nerve fibers Neuron Cells: o Three main parts:  Dendrites- main receptors, provide enormous surface area, convey messages toward cell body (short distance- graded potentials), cannot be myelinated  Cell Body (perikaryon, soma)- surrounds nucleus, contains mitochondria & ribosomes  Nissl bodies- groups of rough endoplasmic reticulum, dark stain  Nuclei- clusters of somas in CNS  Ganglia- clusters of somas in PNS  Axon- transmits signals from cell body to other neurons or effectors  Initial segment- first part of axon extending from axon hillock  Collateral branches- axons further divisions  Terminal branches- smaller branches at ends of axon

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Synaptic axon terminal- distal tip of each terminal branch Synaptic vesicles- at ends of synaptic axon terminals containing neurotransmitter molecules  Structural classes of Neurons: o Multipolar- three or more processes, 99% of nervous system (one axon & the rest are dendrites) o Bipolar- two processes (an axon & a dendrite) o Unipolar- single process (Proximal & distal branches)  Functional classes of Neurons: o (Afferent) Sensory neurons- receptors in organs  CNS o (Efferent) Motor neurons- CNS  effector organs o Interneurons (association neurons)- Between motor & sensory neurons where integration occurs Ion Channels  Types: o Chemically ligand-gated: open when appropriate neurotransmitter binds to receptor, allowing simultaneous movement of sodium & potassium o Voltage-gated: open & close in response to changes in membrane voltage o Mechanically-gated: Open in response to physical deformation of the receptor (as in sensory receptor for pressure & touch) Action Potentials  Types of propagation: o Bare plasma membrane- voltage decays because current leaks across membrane o Unmyelinated axon- voltage gated sodium & potassium channels regenerate the action potential at each point along the axon, so voltage does not vastly decays. Conduction is slow b/c movement of ions take time & must occur before voltage regeneration occurs o Myelinated axon- myelin keeps current in axons & voltage does not decay much. AP are generated on only in nodes of Ranvier & appear to jump rapidly from node to node.  Conduction velocity: depends on axon diameter & degree of myelination  Permeability: o Resting state- No ion movement through channels o Depolarization- Na flowing into cell (At threshold of -55 mV) o Repolarization- K+ flowing out of cell o Hyperpolarization- K+ continuing to leave the cell (Short negative shift) Brain Anatomy  The brain can be divided into four major regions:  Cerebrum: o largest region of the brain divided by longitudinal fissure o lateralization (specialization) of functions o Gyrus- fold o Sulcus- shallow groove

Corpus Callosum- white matter pathway that connects hemispheres Fornix- part of limbic system, support memory & emotion Gray matter- outer convoluted surface, forms foliated surface White matter- deep to cerebral & cerebellar cortices, compose of tracts of myelinated axons that project from overlaying gray matter o Cortical grey matter- made of multipolar neuron cell bodies & attendant dendrites o Pyramidal cells- pyramidal shaped cell body, multipolar neurons of the cortex o Layers of the cerebrum:  Molecular layer- mainly dendrites synapsing w/ cortical neuron axons  Outer granular- mostly stellate cells, axons & dendrites  Outer pyramidal- mostly pyramidal cells that increase in size the deeper into layer  Inner granular- densely packed stellate cells  Inner pyramidal & polymorphic layer- large pyramidal cells (superficial) & variety of cell morphologies (deep) Diencephalon: o Thalamus- forms superolateral walls of 3rd ventricle, relay station for incoming info o Hypothalamus- forms the inferolateral walls of the 3rd ventricle, controls autonomic control center, center for emotional responses, body temp regulation, food intake regulation, sleep wake cycles, endocrine system functioning  Infundibulum- connecting stalk to pituitary gland  Mammillary bodies- relay stations in olfactory bodies o Epithalamus- forms roof of 3rd ventricle, contains pineal gland  Pineal gland- secrete the hormone melatonin to regulate sleep-wake cycles, in feedback loop with suprachiasmatic nucleus (SCN), mainly made of pinealcytes & neuroglial cells  Acervuli- calcium deposits in pineal gland with aging, landmark on X-rays o Hypothalamus-Pituitary Complex: o Anterior pituitary (Adenohypophysis or pars distalis) glandular epithelium, utilize hypophyseal portal system  Adenohypophyseal hormones: PRL, TSH, GH, ACTH, LH, FSH o Posterior pituitary (Neurohypophysis or pars nervosa) Neural tissue, utilize hypophyseal tract  Hormones: Oxytocin & ADH o Pars intermedia Reduced in adult humans  Dividing line between adenohypophysis & neurohypophysis  In infancy, may produce alpha-melanocyte stimulating hormone (alters skin coloration in some vertebrates) Cerebellum: o Dorsal to the pons & medulla oblongata o o o o

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o Coordination of somatic motor function, primary skeletal muscle contraction o Stores learned muscle patterns & coordinates with complex muscle movements o Layers: Includes gray & white matter  Gray matter: molecular layer (unmyelinated fibers, basket & stellate cells), intermediate layer (Purkinje cells), granular layer (deepest; granule cells) Brain stem: o Midbrain Between diencephalon & pons  Cerebral peduncles- two bulges ventrally  Corpora quadrigemina- collection of nuclei scattered in white matter & has four dome-liked projections  Superior colliculi- visual reflex center that coordinate head & eye movement  Inferior colliculi- part of auditory relay center from hearing receptors of the ear  Substantia nigra- allow for smooth movement by inhibiting inappropriate muscle movements & dopamine signals, deep to cerebral peduncle & dark colored due to high content of melanin pigment (precursor to dopamine, degeneration of the substantia nigra’s neurons is cause of Parkinson’s disease- accumulation of alpha-synuclein into inclusions called Lewy Bodies) o Pons Between midbrain & medulla oblongata  Chiefly composed of conduction tracts between higher brain centers & the spinal cord o Medulla Oblongata Most inferior part of the brain stem  Control over cardiovascular & respiratory systems Spinal Cord: o Apart of CNS o Spinal Cord Proper:  Anterior median fissure- marks right & left halves  Gray matter- occupies a butterfly shape  White matter- surrounds gray matter, composed of axonal tracts that propagate both afferent & efferent impulses from neurons on opposite sides (Contralateral) and neurons on the same side (Ipsilateral) o Upper spinal cord (Caudal medulla)  Gray matter- gray horn & ventral horn  Trigeminal spinal nucleus & tract- receive sensory information from ipsilateral side of face  Fasciculus gracilis- ascending tracts that convey sensations from lower limbs to upper brain centers

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Medullary reticular horn- sensory information filtering & arousing cerebral cortex to consciousness  Pyramidal decussation fibers- crossing of pyramidal tracts of motor cortex Embryonic Development  Neural tube- anterior (future brain & stem) & posterior (future spinal cord) portion, formed by week 4 & subdivides into primary brain vessels (3) then secondary brain vessels (5) around week 5 Neural Tube Primary Brain Secondary Brain Adult Derivatives Vesicles (3) Vesicles (5) Anterior (Rostral) Prosencephalon Telencephalon Cerebrum: cerebral (forebrain) hemispheres (cortex, white matter, basal nuclei) Diencephalon Diencephalon (thalamus, hypothalamus, epithalamus) Mesencephalon Midbrain Mesencephalon (Midbrain) Rhombephalon Metencephalon Pons (hindbrain) Cerebellum Myelencephlon Medulla Oblongata Posterior (Caudal) Spinal Cord Meninges  Connective tissue layers that encase the human brain, external to organs of the CNS  Three layers: o Dura Mater Strongest meninx  Two-layered sheet around brain (Superficial Periosteal layer- attached t skull & Deep Meningeal layer- covers brain & continues into vertebral canal) o Arachnoid Mater Middle meninx  Spider web-like extensions into pia mater  Beneath is the subarachnoid space filled with CSF & largest blood vessels serving the brain o Pia Mater Innermost meninx  Delicate layer enriched with tiny blood vessels Ventricles  Four chambers

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One lateral ventricle in each hemisphere separated by the septum pellucidum CSF- circulates from the lateral ventricles through the interventricular foramen to enter the narrow third ventricle  aqueduct of the midbrain  fourth ventricle  Fourth ventricle- two lateral apertures & single median aperture direct CSF to exterior of brain & spinal cord by flowing through into the subarachnoid space  reabsorbed at arachnoid granulations (Project into the veins of dural sinuses)  Choroid plexus- specialized capillary within each ventricle, aggregate of blood vessels encapsulated by ependymal cells projecting into 3rd & 4th ventricles Cerebrospinal Fluid  Produced by ependymal cells (ciliated glial cells line inner walls of ventricles) in choroid plexus  Cushion for cerebral cortex & provides basic mechanical & immunological protection to brain & serves in autoregulation of cerebral blood flow Motor Areas  Lie in posterior part of frontal lobes  Four areas: o Primary motor cortex- in precentral gyrus, made of pyramidal cells that allow for conscious control of precise or skilled voluntary movements; signals sent from primary motor cortex to body regions o Premotor cortex- Anterior to precentral gyrus; controls learned repetitious/patterned motor skills (i.e. musical instruments & typing) o Broca’s area- Anterior to inferior region of premotor cortex; usually only in left hemisphere & directs muscles of speech production o Frontal eye field- partially in & anterior to premotor cortex & superior to Broca’s area; controls voluntary movement of eyes Sensory Areas  Eight areas: o Primary somatosensory cortex- In postcentral gyrus of parietal area; Receive info from somatic receptors & identify body region being stimulated (Spatial Discrimination) o Somatosensory association cortex- Posterior to primary somatosensory cortex; integrates sensory input & relay it via primary somatosensory cortex to produce an understanding of an object being felt o Visual areas- On extreme posterior tip of occipital lobe; receives visual information that originates on retina o Auditory areas- In superior margin of temporal lobe abutting lateral sulcus; perceive sound o Olfactory cortex- On medial aspect of temporal lobe in piriform lobe; smell perception o Gustatory cortex- In insula; perceives taste stimuli o Visceral sensory area- In insula posterior to gustatory cortex; visceral sensation (upset stomach or full bladder)

o Vestibular cortex- In posterior part of insula & adjacent parietal cortex; conscious awareness of balance Pathways  Ascending pathway- conduct sensory impulses upwards through first, second & third order neurons to various areas in the brain (2nd & 3rd are interneurons)  Descending pathways- deliver efferent impulses from the brain to spinal cord o Divided into two groups: o Direct pathway (pyramidal)- control skilled voluntary movement o Indirect (Extrapyramidal)- regulate muscle activities (Tone for posture & balance) PNS Histology  Dorsal root ganglion- visible swelling within the dorsal root of each spinal nerve; contain aggregate of unipolar neurons cell bodies & surrounding satellite cells  Unipolar neurons- conduct sensory afferent impulses of PNS to spinal cord  Meissner’s Corpuscle- Light pressure receptors of dermis  Neuromuscular junctions- provide targeted release of excitatory neurotransmitter acetylcholine to sarcolemma (motor endplate; enriched with Ach gated ion channels) Cranial Nerves Name Function Sign of Damage Cause of Damage Olfactory I (S) Smell Anosmia (inability Fracture of to smell) cribriform plate of ethmoid Intracranial tumor or Optic II (S) Vision Hemianopsia stroke (Blindness on affected side) Oculomotor III Mydriasis (Pupil Increased Supplies 4/6 extrinsic eye (M) dilation) intercranial pressure muscles (Inferior oblique, (Early sign is pupil medial rectus, inferior dilation) rectus & superior rectus Diplopia (Difficulty Paralysis of superior Trochlear IV (M) “Pulley” extrinsic eye turning eye inferior oblique muscle muscle (superior oblique & lateral, leads to muscle) double vision) Trigeminal V (B) Three branches, sensory Inflammation of one Tic douloureux fibers to face & motor of the divisions (Trigeminal fibers of chewing muscles; neuralgia) largest cranial nerve Diplopia Any disorder that Abducens VI (M) Controls lateral rectus causes this nerve to (extrinsic) muscle that abducts eyeball (Turns it be crushed against laterally) the sphenoid bone (i.e. stroke) Facial VII (B) Innervates muscles of facial Bell’s Palsy Viral infection that expression (Paralysis of causes inflammation

Vestibulocochlear Hearing & balance VIII (S)

Glossopharyngeal Innervates tongue & IX (B) pharynx, sensory to the throat

muscles of facial expression on side of face with affected nerve) Vertigo (Loss of balance & equilibrium)

Dysphagia (Difficulty swallowing) & ageusia (Loss of taste sensation) Dysphonia (Hoarseness or difficulty swallowing)

Vagus X (B)

Extends beyond head & neck, innervates visceral body organs of thorax & abdomen

Accessory XI (M)

Innervates trapezius & sternocleidomastoid

Difficulty elevating scapula or rotating head

Hypoglossal XII (M)

Innervates tongue-moving muscles

When sticking out tongue, it moves in direction of damaged nerve

of the nerve

Compression caused by acoustic neuroma- a tumor in Schwann cells of this nerve Nerve damage interrupts the sensory component of the swallowing reflex Nerve damage interrupts the motor component of the swallowing reflex; hoarseness results from paralysis of the muscle of the larynx Nerve damage result sin paralysis of the sternocleidomastoid and/or trapezius Compression of nerve from increased intracranial pressure...