chapter 11-1: intro to nervous system Essential Question: What is the function of the Nervous System? What are the two divisions of the Nervous System? chapter 11-1: intro to nervous system Learning Targets Identify structure and function of 3 types of muscle tissue. Identify the functional characteristics of muscle tissue. List the functions of muscle Describe the anatomy of skeletal muscle
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The master controlling and communicating system of the body Functions Nervous System The master controlling and communicating system of the body Functions Sensory input – monitoring stimuli occurring inside and outside the body Integration – interpretation of sensory input Motor output – response to stimuli by activating effector organs
Nervous System Figure 11.1
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Organization of the Nervous System Central nervous system (CNS) Brain and spinal cord Integration and command center Peripheral nervous system (PNS) Paired spinal and cranial nerves Carries messages to and from the spinal cord and brain
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Peripheral Nervous System (PNS): Two Functional Divisions Sensory (afferent) division Sensory afferent fibers – carry impulses from skin, skeletal muscles, and joints to the brain Visceral afferent fibers – transmit impulses from visceral organs to the brain Motor (efferent) division Transmits impulses from the CNS to effector organs
PNS Motor Division: Two Main Parts Somatic nervous system Conscious control of skeletal muscles Autonomic nervous system (ANS) No conscious control Regulates smooth muscle, cardiac muscle, and glands Has two divisions – sympathetic and parasympathetic
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The two principal cell types of the nervous system are: Nerve Tissue The two principal cell types of the nervous system are: Neurons – excitable cells that transmit electrical signals neuroglia or glial cells (Supporting cells) – cells that surround and wrap neurons Provide support & insulation Promote health and growth
Structural units of the nervous system Neurons (Nerve Cells) Structural units of the nervous system Composed of a body, axon, and dendrites Their plasma membrane functions in Electrical signaling
Whitish, fatty, segmented sheath around most long axons Myelin Sheath Whitish, fatty, segmented sheath around most long axons It functions to: Protect the axon Electrically insulate fibers from one another Increase the speed of nerve impulse transmission
Formed by Schwann cells in the PNS A Schwann cell: Myelin Sheath Formed by Schwann cells in the PNS A Schwann cell: Envelopes and encloses the axon with its plasma membrane
Neurons (Nerve Cells) Dendrites receive stimuli Cell body (soma) is where most cellular machinery is found Axon sends message to next cell Myelin sheath surrounds the axon Schwann cells make up the myelin sheath Figure 11.4b
Dendrites Cell Body Impulse Direction Terminal Branches Axon Nodes Myelin Sheath
On a sheet of paper copy the question and then answer it. Do Now Activity On a sheet of paper copy the question and then answer it. What are the two main divisions of the nervous system? The motor division of the PNS has two parts. The part we can’t control is called what? Schwann cells form what?
chapter 11-2: nervous system Essential Question: What is the function of an impulse in the Nervous System? chapter 11-2: nervous system Learning Targets Identify structure and function of 3 types of muscle tissue. Identify the functional characteristics of muscle tissue. List the functions of muscle Describe the anatomy of skeletal muscle
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Neuron Functional Classification Neurons are classified based on structure and function (we will only cover function) Functional: Sensory (afferent) — transmit impulses toward the CNS Motor (efferent) — carry impulses away from the CNS Interneurons (association neurons) — shuttle signals through CNS pathways
Comparison of Functional Classes of Neurons Table 11.1.3
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The Moving Impulse The minimum level of a stimulus that is required to activate a neuron is called a threshold. A stimulus must be equal to or greater than the threshold to cause a neuron to produce an impulse.
The Nerve Impulse The way the nerve impulse travels through neurons is like how electricity travels through wires. Nerves generate tiny amounts of electrical charges, based on amounts of sodium ions (Na+) and potassium ions (K+).
This temporarily changes the charge of the neuron… The Moving Impulse A nerve impulse begins when a neuron is stimulated by another neuron or by its environment. At the leading edge of an impulse, the sodium gates open and sodium flows into the neuron. This temporarily changes the charge of the neuron… Potassium gates then open and allow potassium out of a neuron. This continues to reverses the charges further, forming an action potential …
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Restoring the Resting Potential The sodium-potassium pump then moves sodium out of the cell and potassium into the cell This restores the original charge across the membrane
How the Action Potential is Generated… At rest. As the action potential passes, potassium gates open, allowing K+ ions to flow out. Action Potential Action Potential At the leading edge of the impulse, the sodium gates open. The membrane becomes more permeable to Na+ ions and an action potential occurs. The action potential continues to move along the axon in the direction of the nerve impulse.
How the Action Potential is Generated… At rest. As the action potential passes, potassium gates open, allowing K+ ions to flow out. Action Potential Action Potential At the leading edge of the impulse, the sodium gates open. The membrane becomes more permeable to Na+ ions and an action potential occurs. The action potential continues to move along the axon in the direction of the nerve impulse.
How the Action Potential is Generated… At rest. As the action potential passes, potassium gates open, allowing K+ ions to flow out. Action Potential Action Potential At the leading edge of the impulse, the sodium gates open. The membrane becomes more permeable to Na+ ions and an action potential occurs. The action potential continues to move along the axon in the direction of the nerve impulse.
How the Action Potential is Generated… At rest. As the action potential passes, potassium gates open, allowing K+ ions to flow out. Action Potential Action Potential At the leading edge of the impulse, the sodium gates open. The membrane becomes more permeable to Na+ ions and an action potential occurs. The action potential continues to move along the axon in the direction of the nerve impulse.
The movement of Na and K changes the charge across the cell membrane Quick review When a stimulus overcomes the threshold a neuron starts an action potential The action potential is created by moving ions of sodium (Na) and potassium (K) The movement of Na and K changes the charge across the cell membrane When the Na and K levels are restored, the charge is reversed and the cell is at rest (resting potential)
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Neurons do not touch other neurons. The Synapse Neurons do not touch other neurons. The tiny space between two neurons is called a synapse. Neurotransmitters are chemicals released by one neuron to transmit an impulse across a synapse and stimulate the next neuron.
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Neurons are highly irritable Neurophysiology Neurons are highly irritable Action potentials, or nerve impulses, are: Electrical impulses carried along the length of axons Always the same regardless of stimulus The underlying functional feature of the nervous system
Supplemental Videos
https://www.youtube.com/watch?v=TevNJYyATAM
https://www.youtube.com/watch?v=fHRC8SlLcH0
Supplemental Questions
Add the following to the DNA paper you created yesterday: Do Now Activity Add the following to the DNA paper you created yesterday: Draw a diagram or chart of how our nervous system is organized.
The movement of what substance reverses the charge of a neuron? Do Now Activity PLEASE COPY AND THEN ANSWER THE FOLLOWING onto the paper that has the other two DNAs: The movement of what substance reverses the charge of a neuron? What is the name of the gap between two neurons? List in correct order the flow of a nerve impulse through the neuron ( e.g. name the parts)?