Nervous System Notes PDF

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Wednesday, February 1, 2017

Nervous System Brain

- CNS location • the CNS is housed within the dorsal body cavities • Cranial cavity: contained within the skull, location of the brain, cranial meninges, and CSF. Cranial meninges protect (dura mater-2 layers outermost layer. arachnoid mater-just inside dura mater. extends cobweb-like projections into the subarachnoid space. pia mater- soft. envelopes brain and spinal cord. all provide protection and stability for brain and spinal cord. also provide space for blood vessels- subarchanoid space, cerebrospinal fluid)

• Spinal cavity: contained within the vertebral canal, inside the vertebral column. Location of the spinal cord, spinal meninges, and CSF

• Epidural hematoma: right outside the dura mater. If someone gets punched in the pterion, it could break the middle meningeal artery and cause bleeding in the brain. Treatment: drill hole in skull, relieve pressure, tie off bleeding vessel

• Subarachnoid hematoma: SAH is a neurological emergency. Hemorrhage in the subarachnoid space. Less common but an important cause of stroke. “Worst headache of my life.” Hypertension left untreated. Aneurysm in artery.

• Subdural hematoma: bleeding between dura and arachnoid mater. often due to ruptured vein

• Cerebrospinal fluid: 2nd line of defense. Produced in cavities called ventricles by choroid plexus. Part of ventricular system. Interventricular foramen, lateral ventricles, cerebral aqueduct, third ventricle, fourth ventricle. Most CSF is produced in the lateral ventricles, passed to interventricular forman, then into third ventricle, then down cerebral aqueduct into fourth ventricle where it will exit the brain move into subarachnoid space around the brain to keep it floating. Half a liter of CSF produced in 24 hours. Hydrocephalous if CSF is blocked: excess fluid in brain.

• Innermost layer of the meninges: pia mater • Found in the subarachnoid space: arteries, small veins, CSF • connects third and fourth ventricles: cerebral aqueduct 1

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• bad to have additional fluid inside your skull because there is no additional room for it so your brain will become compressed

- Brain parts - superior: cerebrum (cap on mushroom) beneath that and hanging off the back is the cerebellum

- brainstem: connects brain and spinal cord to your cerebellum and the rest of your body

- medial view: diencephalon: composed of structures that end in “alamus” (hypothalamus, etc). found at top of brain stem, just below the rest of the cerebrum

- cortex: outer most brown layer if you cut into a brain the way you cut bread for a sandwich. where you find the cell body’s for most of the neurons in the brain. within the cortex there are ridges (gyrus) and valleys (sulcus) GRAY MATTER

- deep to the cortex: white matter connections between cell body’s. Internal capsule connects the cortex down to the rest of the body, lets info from the rest of the body be carried up to the brain for making decisions. corpus callosum is a bundle of fibers that connect left and right hemispheres.

- frontal: higher intellectual functions, personality, voluntary motor control of skeletall muscle

- parietal: sensory (body wall), understanding speech and expression thoughts and emotions

- temporal: primary auditory cortex; interpretation of olfactory sensations - occipital: visual Thalamus:

- receives all sensory information coming into the body - processes and conveys information going to the cortex, also receives info from cortex on what to let through

- the “executive assistant” to the cortex. bill gates doesnt answer all his emails - damage or disease produces sensory or motor or behavioral abnormalities (hypertension)

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Wednesday, February 1, 2017 Hypothalamus

- communicates with cerebrum and brainstem - responsible for changing the body to keep it in homeostasis - receives information about food intake, water levels, blood pressure, temperature, etc,. and controls visceral function. 4 F’s: feeding, fighting, fleeing, reproduction. Everything to keep you alive

- controls the secretion of hormones - works to create bodily reaction to emotional stimuli Cerebellum

- “little brain” posterior to pons in 4th ventricle but inferior to occipital lobe. behind part of the brainstem.

- communicates with cerebrum and brainstem to smooth out movements; walking in straight line, etc. Balance. Very susceptible to alcohol

- involved in control of equilibrium with inner ear - damage or disease produces a condition known as ataxia- inability to coordinate voluntary motor control Basal Ganglia

- start and stop of motor movements (gray matter) - communicates with cerebrum - responsible for allowing the appropriate amount and type of movement/motor initiation

- delicately balanced activity between structures - damage or disease produces either too much movement (huntington’s disease) or too little movement (parkinson’s disease) Hippocampus

- short term memories to long term memories - found inside the temporal lobe

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- damage or disease produces anterograde amnesia, the inability to make new memories. most notably destroyed early on in alzheimer’s disease. In alzheimer’s brain: cortex shrivels up damaging areas involved in thinking, planning, and remembering. Shrinkage is especially severe in the hippocampus, an area of the cortex that plays a key role in formation of new memories. Ventricles grow larger Amygdala

- small, almond shaped structure in the temporal lobe - anterior to hippocampus - involved in attaching emotions to experiences and memories, particularly fear - damage or disease produces a loss of appropriate emotional responses to stimuli Brainstem

- midbrain (superior)- mesencephalon - connects cerebrum to the rest of the brainstem - communicates with cerebellum - reflex center: visual reflex and auditory reflex - Pons (inferior to midbrain) - transmits/relays impulses between cerebrum and cerebellum and brainstem - controls breathing - houses 4th ventricle - anterior to 4th ventricle - Medulla Oblongta (continous with spinal cord) where brainstem transitions into spinal cord

- controls vital autonomic functions - cardiac, vasomotor, and respiratory centers (along with pons) - space occupying lesion (blood from epidural, tumor, fluid) can cause patient to suffocate to death when cerebellum crushes up against medulla. Damages respiratory nuclei relays all sensory information to cortex: thalamus 4

Wednesday, February 1, 2017 valley-like depressions in cortex: sulci (singular is sulcus) 4th ventricle is between the cerebellum and the pons governs the release of hormose: hypothalamus

Spinal Cord Spinal nerves C1-C7 exit superior to same number vertebrae Spinal verve C8 exits inferior to C7 Spinal nerves T1-Co1 exit inferior to same number vertebrae Spinal nerves below the L2 vertebra have very long dorsal/posterior and ventral/anterior roots which form cauda equina Difference in length of vertebral column and spinal cord- grow at different rates and times

- Lumbar Spinal Puncture (Spinal tap) • insert needle midline between L3 and L4 (or L4 and L5) spinous processes in adults: lower in infants and children

• Needle pierces dura mater and arachnoid mater, pushes aside fibers of cauda equine

• Withdraw 3-9 mL of CSF from subarachnoid space • Blood in CSF: subarachnoid hematoma Thicker end: Anterior Motor Ventral(motor found between anterior/ventral): muscle contractions Thinner end: Dorsal Sensory Posterior(sensory found between dorsal/posterior): feel things, transmit info Spinal Nerve is about a centimeter (small) dorsal ramus and anterior ramus branch off Ramus ALL (sensory and motor) A in ramus A in All Root ONLY (only motor or only sensory) O in root O in only Anterior (Ventral) Rami

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- Become intercostal (T1-T11) nerves and Subcostal (T12) nerve when they enter intercostal space under rib

- located in costal groove - motor and sensory to structures of anterolateral body wall • intercostal mm., abdominal mm., bone and skin - Anterior (ventral) rami are also mixed nerves • carry somatic sensory, somatic motor, visceral sensory, and visceral motor information

- Somatic Nerve Plexuses • most anterior (ventral) rami form nerve plexuses • plexus= network of intersecting nerves • cervical plexus (C1-C4) • brachial plexus (C5-T1) • lumbar plexus (L1-L4) • sacral plexus (L4-S4) • C3 C4 C5 all bundle together and go to diaphragm - Myotomes • myotome- a group of muscles innervated by the ventral roots of a given spinal cord segment

• each muscle is innervated by more than one spinal nerve Ex. triceps brachii m. innervated by radial n

• each spinal nerve innervates more than one muscle. ex. musculocutaneous n. (C5C7) innervates biceps branchii, brachialis, and coracobranchialis mm segmental innervation

- dermatome (sensory) important dermatomes of trunk T4 nipple, T10 umbilicus, T12/ L1 groin Cervical Plexus (C1-C4)

- distribution to neck, shoulder, and posterior head 6

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- phrenic nerve - C3, C4, C5 keep the diaphragm alive The ventral rams contains fibers carrying both sensory and motor information A plexus is mostly composed of nerve fibers from multiple spinal levels Somatic Reflexes

- Reflex- an immediate, involuntary motor response to a specific sensory stimulus - Reflex Arc: 2 components • afferent limb: sensory —-> CNS • efferent limb: motor —-> effector organ (skeletal) Monosynaptic reflex: direct communication between sensory and motor neuron Polysynaptic reflex: interneuron facilitates sensory-motor communication The efferent arm of a reflex arc for the leg requires information carried along the ventral root Spinal Cord Video: Motor neuron (frontal lobe) is needed to make an arm contract (left part of brain). This neuron is going to send impulses along fibers that run down through the internal capsule down to the brainstem. In the lowest portion of the medulla, that fiber is going to cross over to the opposite side (right part of brain). This fiber will descend down the spinal cord to the arm and make a synapse. This synapse attaches onto somatic/ spinal/lower motor neurons which will send impulses along fibers that exit the spinal cord and synapse onto the arm muscle. When the synapse is activated, it'll cause that arm to contract.

Sensory ending in skin of right arm, the impulse is carried on one portion of a neuron. That neuron has a cell body in the dorsal root ganglion (just outside the spinal cord). The other side of the neuron reaches up into the spinal cord, up into the brainstem where it crosses over to the left side of brain, which reaches up and goes to the thalamus. From the thalamus(executive assistant), a neuron in the thalamus will send impulses along the fiber that goes up to sensory cortex in the parietal lobe.

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Wednesday, February 1, 2017 White matter carries info down/up.

H shape in spinal cord is gray matter, this is where you find neuronal cell bodies. Bottom of H is thicker- anterior side. The “bulge” in the root is the dorsal root ganglion. Posterior- sensory. Anterior-motor. Somatic sensory- interaction of your body surface with the environment Visceral sensory- all of your organs and glands going on inside your body, sensory information they provide to your brain Somatic motor- skeletal movement (limbs) Autonomic motor- heartbeat, intestines digest (visceral) Somatic: Information flows in along somatic sensory fibers, their cell bodies are found in dorsal root ganglion. The information is carried by the other arm of the neuron/fiber and carried into the spinal cord. There it ascends up into the brain (posterior horn). Interneurons allow for communication between the sensory and motor neurons found in the spinal cord. Motor: from spinal cord out into muscles in periphery. These motor neuron cell bodies are found in the anterior horn. That information is sent along fibers that run along the ventral root from the spinal cord. Spinal nerve is composed of the posterior and anterior root ganglion. This nerve contains both motor and sensory information. If you damage a spinal nerve, you get both deficits. The relative locations of cell bodies can be seen on the right hand side. Where it says somatic, for sensory, that has to do with where those fibers are ascending and who they are talking to. Spinal nerve is only about a centimeter long. After the spinal cord, it splits into posterior(dorsal) and anterior(ventral) rami- includes both sensory and motor information. Anterior-black Posterior-yellow. The posterior ramus- carry visceral motor (blood vessels, sweat glands) and information from the skin of the back and carry motor to the intrinsic back muscles. The anterior ramus- runs as intercostal (ribs) nerves, inferior rib part. Located in costal groove. Motor and sensory to structures of anterolateral body wall. The anterior ventral rami are mixed- somatic sensory, somatic motor, visceral sensory, visceral motor. T1T12. Above and below T1-T12 is more complicated. Plexus- network of intersecting nerves. There are no plexuses between T2-T12. 8

Wednesday, February 1, 2017 Cervical (C1-C4) Brachial (C5-T1) Lumbar (L1-L4) Sacral (L4-S4) Reflex is an immediate involuntary motor response to a specific sensory stimulus. Involuntary meaning brain doesnt have to be functioning for these things to happen (could be in coma). These are processed in the spinal cord, at the level where the sensory is coming in and motor is coming out. Afferent: sensory info coming into spinal cord. Efferent: motor going out into the effector organ (skeletal muscle most likely) Patellar “knee jerk” reflex indicates L4 is undamaged Cranial Nerves Video: Difference between spinal nerves vs. cranial nerves

- Spinal Nerves • extend from spinal cord • contain motor and sensory fibers • damage causes weakness/paralysis, sensory anesthesia - Cranial Nerves • extend from brain and brainstem • can be motor OR sensory OR both • deficits can be more complicated Cranial Nerves

- 12 paired nerves - each has a name and a roman numeral(need to know), don’t use arabic numeral - each exits the skull to reach its target structure(need to know + function + what it would present like if it got damaged)

- cranial nerve 5 is both sensory and motor

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- cranial nerve I: olfactory nerve…carries sense of smell. orange/yellow part passes through cribiform plate. the blue part is not the cranial nerve, its how the cranial nerve gets connected back to the brain. damage is easy if you fall or get hit in the head and lose your sense of smell. produces new neurons after you've developed so you may be able to gain your sense of smell back.

- cranial nerve II: optic. sensory nerve…carries vision from eye..left cranial nerve II to left eye. right cranial nerve II to right eye. one nerve to two different parts of the retina.

- cranial nerve III: oculomotor nerve…control ciliary muscles and sphincter pupilae which are involved in the control of the pupil (size and shape of lens) to allow body to accommodate when you need to look at things closer or further away. let in more light or less. controls all extrinsic muscles of eye except those listed for CN IV and VI. 6 muscles around eye. 4 of 6 are controlled by cranial nerve III. moves eyes up and down.

- cranial nerve IV: trochlear motor. controls superior oblique muscle of eye. - cranial nerve VI: abducent motor nerve. controls lateral rectus muscle of eye, only one it controls. causes eye to abduct.

- (LR6SO4)3 pneumonic device • lateral rectus = VI (abducens) • superior oblique = IV (trochlear) • all other eye muscles = III (oculomotor) - foramina is where cranial nerves pass through - CN I-olfactory-cribriform plate - CN II-optic nerve-optic canal - CN III-oculumotor nerve-superior orbital fissure - CN IV-trochlear nerve-superior orbital fissure - CN V- trigeminal nerve- superior orbital fissure, foramen rotundum, foramen ovale - CN VI- abducens nerve- superior orbital fissure - CN VII- facial nerve- internal acoustic meatus - CN VIII- vestibulocochlear nerve- internal acoustic meatus

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- CN IX- glossopharyngeal nerve- jugular foramen - CN X- vagus nerve- jugular formane - CN XI- spinal accessory nerve- jugular foramen (enters skull via forman magnum) - CN XII- hypoglossal nerve- hypoglossal foramen canal Damage to the right CN II would most likely result in loss of vision from the right eye Damage to the Trochlear nerve would directly impair the function of only 1 extra ocular muscles The Three Branches of the Trigeminal(cranial nerve V)

- V1- ophthalmic; carries sensory information from area indicated above (frontal lobe) as well as the cranial dura

- V2- maxillary; carries sensory information from area indicated above (maxillary) as well as the cranial dura

- V3- mandibular; carries sensory information from area indicated above (mandibular) as well as the anterior two-third of the tongue (touch sensation only) and the cranial dura. Additionally, it carries motor information controlling the muscles of mastication (chewing). Cranial nerve VII- carries both motor, visceral motor, and sensory. Motor is muscles of facial expression. Visceral is submandibular, sublingual, lacrimal, nasal and palatine glands. Sensory is taste from anterior two thirds of tongue and soft palate. Clinical Correlate: Bell’s Palsy (CN VII): facial nerve (CN VII) paralysis on the left or right side of the face. Cranial nerve VIII- vestibulocochlear. equilibrium, balance, and motion. What position your head is in, if you’re moving, etc. Damage to this nerve can result in loss of hearing, balance abnormalities, abnormal eye movements. A patient presents to the clinic and is unable to hear out of their right ear. Damage to the VIII cranial nerve accounts for this Cranial nerve IX- glossopharyngeal. Carries sensory information, taste from posterior one third of tongue (taste and touch) and pharynx (sensory portion of gag reflex)

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Wednesday, February 1, 2017 Cranial nerve X- vagus. The motor portion for the gag reflex (the actual motion). Also provides motor to other muscles of the larynx and pharynx as well as a lot of visceral motor information that helps to control your organs. Cranial nerve XI- spinal accessory. Strictly motor. Sternocleidomastoid and trapezius. Sternocleidomastoid allows you to turn your head and trapezius allows you to shrug your shoulders. Damage would cause shoulder to slump down when they come into clinic. Cranial nerve XII- hypoglossal. All of the motor for the tongue (extrinsic and intrinsic muscles) A tumor affecting the jugular foramen would damage the IX, X, and XI nerves

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