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CN 1 Olfactory Nerve Smell CN2 Optic Nerve Sight CN3 Oculomotor Nerve Move Eyes, Constricts pupils, accommodates, rotate the eye, adjust the amount of light + Focus CN 4 Trochlear nerve Controls eye movement CN 5 Trigeminal Nerves - Where herpes comes from. Chews and feels front of head (Sensory Input for the face) 3 Branch 1.Ophthalmic Branch: Sensory from the forehead, eyelids, tear glands 2.Maxillary Branch: Sensory from the skin of face, upper lip, Upper teeth and gums 3.Mandibular Branch: Sensory from Lower teeth and gums, Lower lip, Skin of the jaw (motor for chewing) CN 6 Abducens Nerve Abduct the eyes, Moves the eyes, “ Somatic Efferent”, Controls a single muscle of the eye. (really only lateral rectus of the eye) CN 7 Facial Nerve Moves Face, Taste, Salivates (Facial expressions, impulses to tear and salivary glands. Sensory fibers carry impulses from taste receptors on the anterior tongue.) - Movement - Facial paralysis: Bellspaulsy from herepes virus, but in different cranial nerve. CN 8 Vesti-bulo-cochlear Hearing, Regulates Balance Nerve Nerves originate from the ear. These nerves are sensory and have 2 branches: 1. The Cochlear branch: For hearing 2. Vestibular Branch:: For Balance CN 9 Glossopharyngeal Taste, salivates, swallows, monitors blood pressure Associated with the tongue (glasso) and the pharynx (throat) Motor Fibers: Salivary Glands, Swallowing Sensory Fibers: Tonsils, Posterior tongue, Carotid Artery, Pharynx CN 10 Vagus Taste, Swallow, Talking, Most important parasympathetic Nerve Largest Parasympathetic Nerve in the body. The only cranial nerves that extend from the medulla oblongata and travel through the neck to the thorax and abdomen. These mixed nerves carry sensory impulses from the throat, esophagus, thorax and abdomen to the brain. the motor fibers supply the heart and many smooth muscles and glands. CN 11 Accessory Nerve Originate from the medulla oblongata and the spinal cord. The cranial brances join a vagus nerve to carry impulses to the muscles of the throat. The spinal branch supplies motor impulses to the muscles in the back and neck CN 12 Hypoglossal Nerves Nerves that pass into the tongue. Move the tongue in speaking, chewing, swallowing Cranial Nerves Remember: Oh Oh Oh To Touch And Feel A Guy Very Sexy And Hot The Nervous System Animals have 2 coordinating systems that often cooperate to control physiology and behavior: 1. Endocrine System 2. Nervous System Endocrine System Relies on chemical signals Consists of individual glands that release hormones that travel via blood Response to hormones may take seconds to minutes Dispersal of hormones in blood exposes most of body cells, however, only those with proper receptors respond Fight or Flight section Nervous System Uses electrochemical signals Consists of specialized cells that branch throughoug the body and conduct signals directly to and from specific targets Structural Complexitiy of the system permits the integration of a broad spectrum of information and stimulation of a very wide range of responses Subdivision of the Nervous System 1. The Central Nervous System (CNS) Brain and Spinal Cord: At a very basic level they are responsible for integrating sensory input and (coordinating) motor output Motor Output: leaves the CNS via motor neurons, which communicate with effector cells (muscle cells or endocrine cells) 2. Peripheral Nervous System (PNS) Divided into: 1. Somatic (voluntary) PNS 2. Visceral (involuntary) PNS a.k.a Autonomic (ANS) Somatic PNS 12 Pairs of Cranial nerves, 31 pairs of spinal nerves. These innervate the skin, joints, and muscles that are under voluntary control. The somatic motor axons, which command muscle contraction Axons from the “motor neurons” supply muscles (cell bodies reside within the CNS) and sensory neurons bring information from the skin and joints to the CNS (cell bodies are found in dorsal root ganglia—outside the spinal cord). Ganglia= clusters) The somatic sensory axons, enter the spinal cord via the dorsal roots, the cell bodies of these neurons lie outside the spinal cord in clusters called dorsal root ganglia. There is a dorsal root ganglion for each spinal nerve. ANS further subdivides into the sympathetic (“fight or flight”) and Parasympathetic (“resting and digesting”) Divisions. The Visceral PNS - Innervate internal organs, blood vessels, and glands. Think emotional reactions that are beyond control, such as “ butterflies in the stomach” or “blushing” Cells of The Nervous System 1. Neurons 2. Supporting cells Neurons of the Somatic PNS Sensory neurons: (“afferent fibers”) convey information from the skin and joints. They carry signals to the CNS. Cell-bodies located within the dorsal root ganglion (a “ganglion” is a collection of nerve cell bodies located outside the CNS). Motor Neurons: (“efferent”) convey impulses away from the CNS to effector cells (skeletal muscle fiber.) Cell bodies located within CNS. Interneurons: Entire Neuron and all fibers located within CNS. Integrate sensory input and motor output. Neurons of the Visceral PNS or Autonomic System Both divisions, sympathetic and parasympathetic) posses afferent fibers that alter functions of viscera (body organs including blood vessels). In addition, they possess efferent fibers that monitor change in body organs. All cell bodies for these afferent and efferent fibers reside outside the CNS in ganglia. From another Source.. Afferent and Efferent indicate whether the axons are transporting information towards or away from a point. Consider the axons of the PNS relative to a point of reference in the CNS. The somatic or visceral sensory axons bring information into the CNS are afferent. The axons that emerge from the CNS to innervate the muscles and glads are efferent. Almost All neurons have 2 types of fibers 1. Dendrites 2. Axons Structure of a Neuron 1. Cell Body: most of a neuron's organelles, including its nucleus is located here 2. Dendrites- highly branched exntensions that receive signals from other neurons 3. Axon- transmits signals to other cells 4. Axon hillock- region where it joins the cell body, typically the region where the signals that travel down the axon are generated. 5. Synaptic terminal- where the axon divides into branches, each of the ends land here 6. Synapse- the site of communication between the synaptic terminal and another cell Glia- are supporting cells (like glue) that are essential for the structural integrity of the nervous system and for the normal functioning of neurons. In the mamalian brain, glia outnumber neurons by 10-50 fold. there are several types of glia in the brain and spinal chord. As a group, these celld o much more then just gold neurons together Neurotransmitters Chemicals that cross the synapse ( the gap between the axon terminal and the dendrite of follower neuron or effector cell) Supporting cells (Glial cells) Cells that structurally reinforce, protect, insulate and generally assist neurons (glue) Do not conduct impulses Outnumber by neurons by 10 fold Glial Cells of the CNS 1. Astrocytes- Control ionic environment, induce Blood Brain Barrier (BBB), forms a Glial Scar. (these cells fill spaces between neurons. Provides influence whether a neuron can grow or retract.) Also regulating chemical content of the space. - BBB: Functional barrier between the blood and the interstitial fluid of the brain, which is very much like cerebral spinal fluid. What it really is, are tight junctions between capillary endothelial cells. - So the brain has just as much or more vascularization then any other organ in the body. Huge need for oxygen and glucose utilization. So its very well pro-fused with capillaries. Don't imagine a brain is separated away from the blood. It just means that nothing can get squeezed between the squamous cells, and the cells self regulates what passes through its membranes. 1 reason is because the predominating neurotransmitters of the brain are amino acids. But the most prevalent neurotransmitter in the brain by far, is glutamate. And you get a lot of that when you eat a steak, or protein. So if you ate a good protein meal, and then it circulates in your blood well then basically you go into a seizure without a BBB, you over stimulate. - So basically the BBB are induced by the foot process of the astrocytes. (They look like stars). - Function Specifically: Are super important in (ion balance) but specifically with potassium. When potassium is elevated extracellularly, it can shut down or stop neuron firing. . (Think perfect murder: potassium ions in I.V) So they make sure there is NO elevation of potassium, despite the number of action potentials that could cause that elevation. - When the brain is damaged, a reactive astrocytosis occurs. Reaction of the astrocytes to try and protect the remaining viable tissue, and they form a glial scar. BTW 20 sec. of ATP depravation, kills a neuron. Also from the book: - Astrocytes adjacent to active neurons also cause nearby blood vessels to dilate, which increase blood flow to the area, enabling the neurons to obtain oxygen and glucose more quickly. During development, astrocytes induce the formation of tight junctions between cells that line the capillaries in the brain and spinal cord. The result is the BBB which restricts the passage of most substances into the CNS, allowing the extracellular chemical environment of the CNS to be tightly controlled 2. Oligodendrocytes- form myelin in CNS, Myelinates axons. (insulates the wire) 3. Microglia- are phagocytic, originate outside the CNS (removes debris left by dead or degenerating neurons and glia) Migrate to the brain, their origins are the same of a monocyte (give rise to microglia). When activated, its a strong indication of neuro-pathology. 4. Ependymal Cells- Secret CSF (Choroid Plexus) and line brain ventricles. - (provides the lining of fluid-filled ventricles, also directs cell migration during brain development). 4 Ventricles in the brain btw. (Lateral Ventricles, and Ventricles 3 and 4). (1st and 2nd are the lateral) Full of cerebral spinal fluid. The choroid Plexus is not CSF, it makes the CSF Cerebral Spinal Fluid= CSF Glial Cells of the PNS 1. Schwann Cells- form a myelin sheaths around the axons of the PNS (just like oligodendrocyte) - Use of phospholipids 2. Satellite cells- Similar to astrocytes in function. The only difference between oligodendrocyte and a schwann is, Oligodendrocyte have a few branches and it sends each branch out and wraps around a axon. Think of a stick figure holding onto 2 things in both arms. A Shwann cell uses its whole body to wrap around an axon, and only in the PNS Transmission of Electrical Signals Membrane Potential- A voltage across the membrane, it is necessary for life, sometimes that can be used as a signal -Due to differential distributions of ions and charge -Its the voltage difference between the interior and the exterior of a cell. Because the fluid inside and outside a cell body is highly conductive, where as a cells plasma membrane is highly resistive, the voltage change in moving from a point outside to a point inside occurs largely with the narrow width of the membrane itself. Therefor, it is common to speak of membrane potential as the voltage across the membrane. The frequency really determines the response The “beeping” is the fluctuation of membrane potential, what contributes most of membrane potential is the presence of non-diffusible anions (A). The 2nd most is the sodium potassium pumps. They account for 70% of brain ATP utilization 1. Huge role in establishing membrane potential, keeping the outside positive relative to the inside. It keeps out sodium and brings in potassium, theres a net loss of a positive charge. But also isn't that a net loss of solute? Net loss of solute means that its a village pump. the sodium potassium pump, it is there failure that is the reason of a stroke. If you don't run the pumps, your boat is gonna fill with water. Resting Potential of non transmitting neuron= -64 to -70 mv Remember: The interior is negative relative to the exterior. The inside of membrane of all living cells (for the most part) is negative inside the cell relative to the outside. Outside the cell Cations Na+ 150 mM K+ 5 mM Anions CL - 110 mM A- 0.2 mM Inside the cell Cation Na + 15 mM K+ 150 mM Anions Cl- 10 mM A- 65mM If you were elevate the extracellular potassium, to the extent thats comparable to the intracellular concentrations. it will stop the diffusion gradient. Which is necessary for re-polarization, both for muscles and neurons. The most important 2 cations in an action potential, (only 2 players for neurons in action potential). Equilibrium Potential Balance between diffusion gradient and electrical attraction is All cells have a membrane potential Na+ “wants” to diffuse into cell, down its conc. gradient K+ diffuses out of cell, down its conc. gradient Negative charges inside cell attrack K+ back in Membrane permeability to K+ is 20x greater than for Na+ Therefore, resting membrane potential most influenced by K+ The slight trickle of Na+ into cell results in =70mV, instead of K+= -85V If left unchecked, Na+ leak would further reduce membrane potential, allowing K+ to further leak out Prevented by sodium-Potassium pump Net result: inside relatively negative compared to outside Graded and Action Potentials (Overview) Even though all cells of body have membrane potential, only neurons and muscle cells/fibers can change theirs in response to stimuli This ability results from gated ion channels in neuron and muscles Effect depends upon type of gated ion channel that opens Hyper-polarization: occurs if K+ or Cl- channels open Depolarization: occurs if Na+ channels are open Graded Potentials: magnitude of change depends on strength of stimulus Threshold: (-50 to -55 mV) if via graded potentials, a neuron reaches threshold an action potential is triggered Action Potential: rapid change in membrane potential caused by selective opening of voltagegated ion channels Action potentials are all or none, amplitude not affected by strength of stimulus Wednesday 10/28/08 From Class: We understand that cations are positively charged ions, K+ and Na+, Despite the fact that we have a relatively high concentration of potassium (K) inside the cell, still inside the cell is negative relative to the outside. 2 things contribute most to that: Contributes most to intracellular negativity: 1. Proteins that are non diffuse-able anions (A-)!!!!! 2. Sodium Potassium Pumps: because they pump out 3 sodium (Na+) for every 2 potassium (K+) into the cell. Why is it a pump? Why isn't it an exchanger? Why isn't it facilitated diffusion? Because in both cases, the ions are going against gradients aren't they. In both cases, its pumping sodium against sodium's gradient of ten fold. same with potassium. These pumps are running all the time, Example: Aneurysm: when an artery expands and ruptures, and you have bleeding. How is that damaging? Everything distal to that (tissue) after the break, is going to be deprived of oxygenated blood. (by the way, Anoxic- no oxygen Hypoxic- reduced oxygen) So, that tissue will die quickly, for lack of oxygen because lack of oxygen you can't make ATP (not enough that is). Why is the tissue dead? (without oxygen), no ATP = No function = no pumps!!!! Fluid is always trying to rush into the cell, membranes leak, because the interior is hyper-osmotic, theres more stuff inside the cell its attracting water all the time. 10/30/2008 From Class: The magnitude of the stimulus is only reflected by the frequency of the action potentials. But when you get down to the axon terminal, where action potential comes down, neurotransmitters are released (quantum release).