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Nervous System IB Biology 2 – Van Roekel BILL • What is the part of your body that controls everything else? What are the two parts of this system? • Nervous System • Central Nervous System (brain and spinal cord) and Peripheral nervous system (sensory and motor neurons) Bill • What are the cells used in the nervous system called? Name two different types of these cells. • Neurons • Sensory neurons send signals from sensory receptors all over the body to the central nervous system. • Motor neurons sends signals from the central nervous system to effectors (muscles and glands) all over the body. • Interneurons (also called connector neurons or relay neurons) are usually much smaller cells, with many interconnections. • 6.5.1 State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that can carry rapid electrical impulses. Central Nervous System • Spinal cord receives sensory information from peripheral nervous system and sends message to brain. • Spinal cord also receives MOTOR signal from brain and signals peripheral nervous system. Somatic Nervous System • Receives external stimuli and stimulates a response • Voluntary control of muscle movement Autonomic Nervous System • Maintains homeostasis • Responsible for involuntary control • Divided into two sub levels: – Sympathetic – “fight or flight” – Parasympathetic – “rest and digest” – Enteric – controls digestive system Autonomic Nervous System • Sympathetic: takes over in emergency situations • Parasympathetic: important in returning body to normal state Sympathetic Nervous System • Excitatory response that uses noradrenaline as neurotransmitter to release certain chemicals (epinephrine, norepinephrine, adrenaline, etc) • Associated with “Fight or Flight” response • Increases heart rate • Dilates bronchi to give more oxygen • Dilates pupils • Restricts blood flow from digestive system Parasympathetic Nervous System • Inhibitory response system with neurotransmitter acetylcholine • Associated with relaxed state of body • Returns the system to normal by: – Constricting pupils and bronchi – Slowing heart rate – Increasing blood flow to digestive system Pathway of Pupil Reflex • Pupils are controlled by parasympathetic responses using acetylcholine – Optic nerve receives message from retina in back of eye (retina contains photoreceptors that respond to stimulus of light) – Optic nerve connects with pretectal nucleus of brain stem – Message is sent to and from brain using Oculomotor nerve – Oculomotor nerve synapses with ciliary ganglion – Axons of ciliary ganglion stimulate circular muscle contraction of iris causing it to contract Review of Nervous System • Central Nervous System: Consists of spinal cord and brain, receives and interprets signals from body • Peripheral Nervous System: two parts – Somatic System: takes info from sensory receptors to CNS and sends back motor commands to effectors – Autonomic System: Involuntary and regulates activities of glands, smooth muscle, and heart. BILL - What are the different parts of the nervous system? • Central Nervous System (CNS) – consists of spinal cord and brain, receives and interprets signals from body • Peripheral Nervous System (PNS) – two parts – Somatic System - takes info from sensory receptors to CNS and sends back motor commands to effectors – Autonomic - Involuntary and regulates activities of glands, smooth muscle, and heart • Sympathetic - Excitatory response that uses noradrenaline as neurotransmitter to release certain chemicals, associated with emergency situations. • Parasympathetic - Inhibitory response system with neurotransmitter acetylcholine, associated with relaxed state of body • 6.5.2 Draw and label a diagram of the structure of a motor neuron. Biology of the Neuron Neuron • Neuron, or nerve cell has: – Cell body – contains nucleus and other organelles – Dendrites – short, highly branched processes that receive chemical messages from other cells – Axon – carries nerve impulse away from the cell body. Typically much longer than dendrites Schwann Cells • Schwann cells are individual cells that wrap around the axon to provide insulation during chemical signaling. A layer of Schwann cells forms the Myelin Sheath. Node of Ranvier • Gaps between the layers of Schwann Cells. They function to allow gaps in action potential so the chemical signal essentially “jumps” down the axon. Synaptic Terminals • Synaptic Terminals – relay signals from the neuron to other cells, using neurotransmitters • Synapse – site of contact between synaptic terminal and its target cell. 3 Main Types of Neurons • Sensory neurons have long axons and transmit nerve impulses from sensory receptors all over the body to the central nervous system. • Motor neurons also have long axons and transmit nerve impulses from the central nervous system to effectors (muscles and glands) all over the body. • Interneurons (also called connector neurons or relay neurons) are usually much smaller cells, with many interconnections. • When many individual neurons group together, they form a single structure called a nerve Types of Nerves • 2 categories of peripheral nerves • Spinal Nerves: – 31 pairs (left and right side) that emerge directly from spinal cord. – Mixed nerves – some sensory, some motor neurons • Cranial Nerves – 12 pairs emerge from area of brain called brain stem – Ex: Optic nerve – carries visual information from retina to the brain • 6.5.3 State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons. • http://www.youtube.com/watch?v=xRkPNwq m0mM Nerve Impulse • Nerve impulses are conducted along the axon of a neuron • Result from the change in concentrations of sodium and potassium ions across the membrane of a neuron • Consists of Resting potential and Action Potential Nerve Impulse Pathway • Receptors transform stimulus into action potential • Chain of sensory neurons carry potential to CNS • Interpretation occurs in appropriate area in brain using relay neurons • Response is carried back through CNS with relay neurons and the PNS using motor neurons to area of stimulus by neurons • Potential is carried to effector cells, which stimulate a response The Reflex Arc • 6.5.4 Define resting potential and action potential (depolarization and repolarization) Resting Potential • Resting potential is the electrical potential across the plasma membrane when the nerve is at rest and not conducting a nerve impulse. • Characterized by active transport of Sodium ions (NA+) out of axon cell, and potassium ions (K+) transported into cell • Results in a net positive charge outside the cell and a net negative charge inside the cell Action Potential • Action potential is the positive electrochemical charge generated at the nerve impulse. Normally this is seen as the 'marker' of the nerve impulse position • Depolarization is a change from the negative resting potential to the positive action potential inside the cell – Sodium ions diffuse into the cell and potassium ions diffuse out of the cell when NA+ & K+ channels open • Re-polarization is the change in the electrical potential from the positive action potential back to the negative resting potential inside the cell. • http://highered.mhedu cation.com/sites/00724 95855/student_view0/c hapter14/animation__t he_nerve_impulse.html BILL • Draw a structure of a neuron from memory, including the following: dendrites, cell body, axon, schwann cells, myelin sheath, and synaptic terminal • Explain how a nerve impulse passes through a neuron Neuron Nerve Impulse • Resting potential creates electrical chemical gradient between external and internal environments of neuron, creating membrane potential • Depolarization occurs, where Na and K ions diffuse in and out of membrane channels, creating nerve impulse • Self-propagating action, travels down the axon • Repolarization occurs, where charges return to resting state • Refractory period- when neuron cannot carry another nerve impulse until fully returned to resting potential • 6.5.5 Explain how a nerve impulse passes along a non-myelinated neuron. http://www.youtube.com/watch?v=ifD1YG07fB 8 Resting and Action Potential in Na/K ATPase Resting Potential • Chemical imbalance, resulting from resting potential, between inside and outside of cell creates electrical difference (Membrane potential). • Creates concentration gradient of Na+ and K+ • Area of neuron is polarized Action Potential • Arrival of action potential from a stimulus causes the Na+ to enter neuron, creating a current/initial impulse • If current is strong enough, protein channels (voltage-gated channels) open Na+ diffuse in and K+ out of axon via because of concentration gradient • Depolarization of adjacent sections of neuron occurs. Diffusion of ions results in continuing nerve impulse, or action potential Repolarization • Neurons send dozens of actions potentials in a short period of time • After one impulse is sent out, that area of axon cannot send another impulse until ions are restored to resting potential • Time period for this to occur is the refractory period • To return to resting potential, active transport pumps Na+ out of cell and K+ into cell repolarization Depolarization Repolarization • Resting Potential – electricity generated before application of a stimulus. • Action Potential – brief depolarization/repolarization caused by application of stimulus • 6.5.6 Explain the principles of synaptic transmission. Synaptic Transmission • Synapse: chemical communication between neurons in a sensory pathways – Occurs between terminal buttons of presynaptic neurons and dendrites of postsynaptic neurons • Uses neurotransmitters to pass information between neurons – Neurotransmitters are any chemicals used for synaptic transmission i.e. acetylcholine Synaptic Transmission • Sensory Pathways are unidirectional and consists of many patterns Mechanism of Synaptic Transmission • Action potential reaches the terminal buttons on a Neuron. 1. Calcium Ions (Ca2+) diffuse into terminal buttons of presynaptic neuron 2. Vesicles containing neurotransmitter fuse w/ plasma membrane and release neurotransmitter 3. Neurotransmitter diffuses across synaptic gap 4. Neurotransmitter binds w/ receptor protein on postsynaptic neuron 5. Binding results in channel opening and Na+ diffusing through channel 6. Initiates action potential in postsynaptic neruon 7. Neurotransmitter is degraded by enzymes and released from receptor protein 8. Ion channel closes to sodium ions 9. Neurotransmitter diffuse back across synaptic gap to terminal button in presynaptic neuron http://www.youtube.com/watch?v=LT3VKAr4roo Studying our Senses • • • • • Read 1st page of Studying our senses lab Partner up (2 per group) Each group must wipe down lab table using Lysol Each person must use Germ-X Each partner needs their own spoon and 6 different jellybeans held in a Dixie cup • ONLY TIME YOU WILL BE ALLOWED TO EAT • Other interesting visuals – http://blogs.discovermagazine.com/badastronomy/2009/0 6/24/the-blue-and-the-green/ – http://www.psy.ritsumei.ac.jp/~akitaoka/cataloge.html Bill • Explain how a nerve impulse passes through a neuron • Resting potential creates electrical chemical gradient between external and internal environments of neuron, creating membrane potential • Depolarization occurs, where Na and K ions diffuse in and out of membrane channels, creating nerve impulse • Self-propagating action, travels down the axon • Repolarization occurs, where charges return to resting state • Refractory period- when neuron cannot carry another nerve impulse until fully returned to resting potential Resting Potential • Chemical imbalance, resulting from resting potential, between inside and outside of cell creates electrical difference (Membrane potential). • Creates concentration gradient of Na+ and K+ • Area of neuron is polarized Action Potential • Arrival of action potential from a stimulus causes the Na+ to enter neuron, creating a current/initial impulse • If current is strong enough, protein channels (voltage-gated channels) open Na+ diffuse in and K+ out of axon via because of concentration gradient • Depolarization of adjacent sections of neuron occurs. Diffusion of ions results in continuing nerve impulse, or action potential Repolarization • Neurons send dozens of actions potentials in a short period of time • After one impulse is sent out, that area of axon cannot send another impulse until ions are restored to resting potential • Time period for this to occur is the refractory period • To return to resting potential, active transport pumps Na+ out of cell and K+ into cell repolarization The BRAIN Parts of the Brain • Cerebral Hemispheres: integrating center for high complex functions such as learning, memory, and emotions • Hypothalamus: maintains homeostasis, coordinates nervous and endocrine systems, secretes hormones of posterior pituitary, and releases regulating factors in anterior pituitary • Cerebellum: “little brain” coordinates unconscious functions such as movement and balance • Medulla: controls automatic and homeostatic activities, such as swallowing, digestion, vomiting, breathing, and heart rate • Pituitary Gland: stores and releases hormones produced by hypothalamus and anterior pituitary, secretes regulating hormones Left & Right Hemispheres • Left Hemisphere: contains areas important for all forms of communication. If damaged, person may have difficulty speaking or complicated movements with hands • Right Hemisphere: Specializes in receiving and analyzing information which comes from our senses. Damage results in difficulty identifying faces and locating an object correctly in space