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Systems Regulating Change in Humans The Nervous System A. Divisions of the Nervous System http://www.youtube.com/watch?v=sjyI4CmBOA0 http://www.youtube.com/watch?v=x4PPZCLnVkA The Nervous System - CrashCourse Biology #26 Nervous System CNS PNS Brain Spinal Cord Autonomic Sympathetic Parasympathetic Somatic Sensory Neurons Motor Neurons A1. Central Nervous System A. Protection Surrounded by bone (skull and vertebrae) Wrapped in meninges Dura mater – superficial (“tough mother”) Arachnoid – intermediate Pia mater – deep, lies against the brain Space between the meninges is filled with cerebrospinal fluid (CSF) which absorbs shock, nourishes, and eliminates waste http://www.nlm.nih.gov/medlineplus/ency/imagepages/19080.htm BLOOD BRAIN BARRIER The Blood-Brain Barrier The blood-brain barrier protects the neurons and glial cells in the brain from substances that could harm them. Unlike blood vessels in other parts of the body that are relatively leaky to a variety of molecules, the blood-brain barrier keeps many substances, including toxins, away from the neurons and glia. Most drugs do not get into the brain. Only drugs that are fat soluble can penetrate the blood-brain barrier. These include drugs of abuse as well as drugs that treat mental and neurological illness. The blood-brain barrier is important for maintaining the environment of neurons in the brain, but it also presents challenges for scientists who are investigating new treatments for brain disorders. If a medication cannot get into the brain, it cannot be effective. Researchers attempt to circumvent the problems in different ways. Some techniques alter the structure of the drug to make it more lipid soluble. Other strategies attach potential therapeutic agents to molecules that pass through the blood-brain barrier, while others attempt to open the blood-brain barrier.4 A1. Central Nervous System B. Brain Two types of Nervous Tissue White matter –myelinated, run in tracks (bundles) Gray matter – unmyelinated nerve cell bodies are often clustered together into functional units called nuclei Glial cells are cells within the nervous system that provide support and nourishment to the other cells http://latourettesindrome.blogspot.com/2005_12_01_archive.html www.ascd.org/.../books/jensen2005_fig1.2.gif A1. Central Nervous System C. Spinal Cord Extends from the base of the brain into the vertebral canal Central root – contains CSF Dorsal root – sensory information enters Ventral root – motor information exits Gray matter – centrally located, forms an “H” shape, composed of interneurons White matter – region around the gray matter that takes information to the brain and delivers information from the brain A1. Central Nervous System C. Spinal Cord A2. Peripheral Nervous System A. Somatic Nervous System voluntary http://normandy.sandhills.cc.nc.us/psy150/somatic.html A2. Peripheral Nervous System B. Autonomic Nervous System Involuntary Controls the internal environment, maintains homestasis Divided into two parts: sympathetic and parasympathetic A2. Peripheral Nervous System B. Autonomic Nervous System 1) Sympathetic System Looks like a string of pearls along the spinal cord Fight or flight response Prepares body for emergencies Everything is stimulated Has ganglion (ganglia) - cluster of neuron cell bodies, many connections to be made and many synapses occur A2. Peripheral Nervous System B. Autonomic Nervous System 2) Parasympathetic System Brings everything back to homeostasis see page 398 for a comparison of the sympathetic and parasympathetic systems http://www.drstandley.com/bodysystems_centralnervous.shtml B. The Neuron How do nerves work? - Elliot Krane http://www.youtube.com/watch?v=uU_4uA6zcE&list=PLJicmE8fK0Ehrg3meytY7DT8LJiw uU3Th&index=144 B1. Neuron Structure Dendrites: Receive info and deliver it to cell body Cell Body (soma): contains major cell organelles and neuroplasm. It is the bridge between the dendrites and the axon. Axon: conduct nerve impulses away from cell body. Axon terminal: synaptic knob, site of neurotransmitter release into the synaptic cleft. Synapse: gap between the pre-synaptic neuron and post-synaptic neuron B1. Neuron Structure Axons In the PNS, axons are coated with an insulating material called myelin Myelin is a fatty protein sheath composed of Schwann cells that increases the speed of nerve transmission by ~50X Schwann cells also provide nourishment and regeneration of new nerve tissue Note: Myelinated nerves = white matter Unmyelinated nerves = gray matter B1. Neuron Structure Axons Neurolemma is produced by the Schwann cells in the PNS and other glial cells in the CNS, it is a membrane that promotes the regeneration of damaged axons Spaces between the myelin sheath are called Nodes of Ranvier Impulses jump from node to node. An action potential can propagate down a non-myelinated axon at speeds as slow as 0.5 metres per second (1.8 km/h). In contrast, the saltatory conduction that takes place in myelinated axons allows a potential to travel at speeds of up to 120 metres per second (over 400 km/h)! That is why your brain can communicate with your big toe in a few hundredths of a second B2. Types of Neurons a) b) c) Sensory Neurons – take messages from body parts to the CNS, transmitting impulses from sensory receptors in the body Interneurons (association neuron) – in the spinal cord associated with the CNS, connects one neuron to the next (association neurons) Motor Neurons – bring messages out of the CNS to an effector (muscle, gland etc. ) What is ALS? The disease behind the ice bucket challenge http://globalnews.ca/video/1512882/dr-davidtaylor B2. Types of Neurons • Receptors • NS uses receptors to collect info about internal/external environment Chemoreceptors: sensitive to chemicals Baroreceptors: sensitive to pressure Osmoreceptors: sensitive to fluid levels Mechanoreceptors: sensitive to vibrations Photoreceptors: sensitive to light Thermoreceptors: sensitive to changes in temperature B2. Types of Neurons • Receptors Collected info is sent to the CNS by sensory (afferent) neurons CNS is composed of association (inter or relay) neurons. Theses neurons interpret the information Response is sent back to effectors by motor (efferent) Effectors are muscles, glands or organs that help the organism respond to the stimulus. B2. Types of Neurons Reflex Arc PNS CNS Receptor Sensory Neuron http://www.brainviews.com/abFiles/AniPatellar.htm Association (Interneuron) Neuron Effector Motor Neuron REFLEX LAB Babinski http://www.articleoutlook.com/the-babinskitest-and-the-babinski-response/ https://www.youtube.com/watch?v=kOq5Np0 eZ6A B3. Impulse Transmission All activities depend on nerve impulses The plasma membrane of the neuron allows the axon to conduct an impulse through charge separation Passive Transport Protein channels are needed for ions to pass across the membrane There are K+ channels (leaky) and Na+ channels Active Transport Important in maintaining resting membrane potential Ex. Sodium Potassium Pump Embedded proteins in the neuron membrane pump out 3 Na+ for every 2 K+ allowed in, with the use of ATP Maintains polarization at rest Sodium Potassium Pump http://www.mcgrawhill.ca/school/applets/abbi o/ch11/sodium-potassium2_sodiu.swf B3. Impulse Transmission http://www.getbodysmart.com/ap/nervoussystem/neurophysiology/actio npotentials/actionpotential/tutorial.html Membrane potential Based on the distribution of ions across the membrane Usually –70 mV inside, outside is considered zero Sodium ions naturally move into the cell while potassium ions move out of the cell (electrochemical gradient) B3. Impulse Transmission Resting Membrane potential Inside neuron: high concentration of K+ and negatively charged proteins Outside neuron (ECF): high concentration of Na+, Ca2+ and Clresting membrane potential is approx. -70 mV at rest, the membrane is polarized due to the higher concentration of positive charge in the ECF and the negative charge inside the cell membrane. B3. Impulse Transmission Action Potential 1) Depolarization Stimulation occurs and Na+ channels open allowing Na+ to rush into the cell Membrane potential increases to +30 mV B3. Impulse Transmission Action Potential 2) Repolarization Na+ channels close K+ channels open allowing K+ out to equalize and return the polarity back to normal Using ATP, Na+/K+ pumps quickly re-establish the original resting membrane (3 Na+ for every 2 K+ allowed in) Results in a negative charge inside the cell and a positive charge outside the cell Once an action potential occurs at one spot along an axon, it excites and adjacent portion of the membrane into an action potential. A wave of action potential sweeps all the way down the neuron B3. Impulse Transmission Action Potential http://media.pearsoncmg.com/bc/bc_campbell_ biology_7/media/interactivemedia/activities/lo ad.html?48&B More animations http://bcs.whfreeman.com/thelifewire/content/ chp44/4402s.swf http://www.mcgrawhill.ca/school/applets/abbi o/ch11/voltagegated_voltage_ga.swf http://highered.mcgrawhill.com/sites/0072495855/student_view0/cha pter14/animation__the_nerve_impulse.html B3. Impulse Transmission Action Potential 3) Hyperpolarization The membrane briefly drops below resting membrane potential do to the relative leakiness of K+ channels This prevents another action potential and maintains the refractory period 4) Refractory Period Refractory period is the recovery time required before a neuron can produce another action potential It is an resetting of ionic distribution B3. Impulse Transmission Action Potential 5) Threshold Level Threshold level is the minimum level of a stimulus required to produce a response (approx. –55 mV) All or none – not graded Threshold value – stimulus is just strong enough to cause voltage gated Na+ channels to open Subthreshold Graded responses – summation of subthreshold stimuli can lead to action potential B3. Impulse Transmission Action Potential 6) All or None Response The all or none response of a nerve or a muscle fibre means that the nerve or muscle responds completely or not at all to a stimulus What Determines the Intensity of the Response? More neurons are depolarized Impulse frequency – brain reads it as more pain B3. Impulse Transmission Action Potential http://brainu.org/files/movies/action_potential _cartoon.swf http://media.pearsoncmg.com/bc/bc_0media_ ap/apflix/ap/ap_video_player.html?pap C. More on The Synapse http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter14/animatio n__transmission_across_a_synapse.html C. The Synapse nerve impulses travel from one neuron to another across a small spaces that separates them called a synapse a synapse consists of (1) a terminal bouton, (2) a gap between the adjoining neurons called the synaptic cleft, (3) synaptic vesicles which produce and store neurotransmitters, and (4) the membrane of the dendrite or postsynaptic cell the neuron that transmits the impulse is the presynaptic neuron; the one that receives the impulse is the postsynaptic neuron C. The Synapse Events at the presynaptic neuron action potential reaches the axon terminal Ca2+ causes vesicles containing neurotransmitters to bind to the axon terminal membrane Neurotransmitter is released Neurotransmitters diffuse across synapse to post-synaptic neuron receptors on the membrane Neurotransmitters can be excitatory (depolarization) or inhibitory (hyperpolarization) C. The Synapse Events at the presynaptic neuron C. The Synapse Events at the postsynaptic neuron Inhibitory or excitatory signal is received When the neurotransmitters bind to receptors, the permeability of the postsynaptic neuron is affected May cause an action potential if the threshold is reached C. The Synapse Neurotransmitter Chemicals Acetylcholine - released by nerves that stimulate muscle contraction, typically excitatory (broken down by cholinesterase) (Acetyl)Cholinesterase – released from glial cells, breaks down acetylcholine, prevents continuous stimulation. Norepinephrine (noradrenaline) – produced by the adrenal glands in a fight or flight response, increases blood glucose levels Dopamine – produces feeling of pleasure when released, usually inhibitory Serotonin - it acts as a neurotransmitter regulating normal brain processes, inhibits pain pathways C. The Synapse Drugs synthetic or naturally occurring chemicals can alter mood or emotional state bind to receptors present on post-synaptic membranes Note: See the graph on page 363 Sometimes neurons need simultaneous stimulation to get to threshold level of the next neuron Table 2.1 Major Neurotransmitters in the Body1,7,8 Neurotransmitter Role in the body Acetylcholine A neurotransmitter used by spinal cord neurons to control muscles and by many neurons in the brain to regulate memory. In most instances, acetylcholine is excitatory. Dopamine The neurotransmitter that produces feelings of pleasure when released by the brain reward system. Dopamine has multiple functions depending on where in the brain it acts. It is usually inhibitory. GABA (gamma-aminobutyric acid) The major inhibitory neurotransmitter in the brain. Glutamate The most common excitatory neurotransmitter in the brain. Glycine A neurotransmitter used mainly by neurons in the spinal cord. It probably always acts as an inhibitory neurotransmitter. Norepinephrine Acts as a neurotransmitter and a hormone. In the peripheral nervous system, it is part of the fightor-flight response. In the brain, it acts as a neurotransmitter regulating normal brain processes. Norepinephrine is usually excitatory, but is inhibitory in a few brain areas. Serotonin A neurotransmitter involved in many functions including mood, appetite, and sensory perception. In the spinal cord, serotonin is inhibitory in pain pathways. http://science-education.nih.gov/supplements/nih2/addiction/default.htm D. Central Nervous System The brain and spinal cord The Unfixed Brain http://www.youtube.com/watch?v=jHxyPnUhUY&feature=youtu.be Pinky and the Brain http://www.youtube.com/watch?v=h5f56Ynb0 1E&feature=youtu.be Phineas Gage http://www.youtube.com/watch?v=MvpIRN9D 4D4 D1. The Brain The Cerebrum a) Cerebral cortex – outermost part of the brain composed of gray matter, folded to increase surface area Gyri (folds) and sulci (indentations) http://www.youtube.co m/watch?v=MvpIRN9 D4D4 MRI D1. The Brain a) The Cerebrum Cerebral hemisphere is divided into the right (creativity) and left (mathematical) cerebral cortex Frontal Lobe: controls movement (walking and talking), sometimes linked to intellectual activities and personality Temporal Lobe: controls smelling and hearing, sometimes linked memory and interpretation of sense information Parietal Lobe: controls touch and temperature awareness, sometimes linked to emotions and speech interpretations, reading Occipital Lobe: controls vision, and interprets visual information D1. The Brain The Cerebrum a) Cerebral hemisphere is divided into the right (creativity) and left (mathematical) cerebral cortex Speech: temporal – the Wernicke’s area picks up written and spoken words frontal – Broca’s area is involved in language processing, speech production and comprehension D1. The Brain The Cerebellum b) coordination of muscle activities (balance, muscle tone, body position etc) ensures movements are coordinated can be programmed to remember movements https://www.facebook.com/Ca lgaryHumaneSociety/post s/582899035084614 D1. The Brain The Brainstem c) • • • known as the medulla oblongata cardiac center, breathing, vasa-motor control reflex actions – vomiting, sneezing, coughing, swallowing The Pons d) • the region of the brain that acts as a relay station by sending nerve messages between the cerebellum and the medulla The Thalamus e) Located below the cerebrum Screens sensory information so that it can direct attention to stimuli of importance (acts as a filter for information brought to conscious thought) D1. The Brain Hypothalamus (the brain within a brain) f) control of the ANS, it is the way the internal environment works (maintains homeostasis) receives information from internal organs co-ordinates nervous and endocrine systems connection between emotions and physiology feelings of rage/anger body temperature depression control hunger/fullness center thirst/osmoreceptors sex drives sleeping/waking patterns D1. The Brain Pituitary Gland g) • The master gland Corpus Callosum h) • Region of white matter that connects the left and right hemispheres Meninges i) act as shock absorbers protects from chemicals entering (blood brain barrier) and going all the way down the spine Dura mater, arachnoid, pia mater Cerebrospinal Fluid j) shock absorber – carries red blood cells and nutrients produced in the ventricles of the brain (spaces/gaps in the brain) Girl Living With Half Her Brain http://www.youtube.com/watch?v =2MKNsI5CWoU http://www.youtube.com/watch?v =yNWQUN4jg-s Brain dissection D2. The Spinal Cord Two Main Functions • a) b) communication between peripheral nervous system and the brain simple reflex actions reflex arc (see page 354) stimulus sensory receptor sensory neuron interneuron motor neuron effector (muscle/gland) D3. Cranial Nerves Do not pass through the spinal cord • a) Vagus nerve from the brainstem, down neck, and through the whole body – bladder, kidney, digestive system E. Autonomic Nervous System nerves designed to maintain homeostasis which are not under conscious control sympathetic nervous system prepares the body for stress parasympathetic nervous system returns body to normal resting levels see table 15.1 on page 366 and the diagram on page 367 ganglion (ganglia) - cluster of neuron cell bodies, many connections to be made and many synapses occur sympathetic nervous system has ganglia