Nervous System
Nervous System Purpose: The Nervous System controls and coordinates functions throughout the body and responds to internal and external stimuli
Parts of the Nervous System Central Nervous System: Brain and Spinal Cord Peripheral Nervous System: The rest of the nerves in the body
How do they work together? Peripheral nerves connect the central nervous system to the rest of the body
Central Nervous System Consists of the brain and spinal cord Relays messages, processes and analyzes information
The Brain Cerebrum - largest part of the brain. Thinking, language, motor function, touch Cerebellum - “little brain”. Controls coordination, balance, movement. Thalamus - located just above brain stem. Motor function, sensory perception Hypothalamus - size of pearl. Controls autonomic and endocrine function, food and water intake
Peripheral Nervous System Consists of all of the nerves that are not a part of the brain or spinal cord Includes sensory and motor nerves
Peripheral Nervous System Somatic Nervous Sys: Controls voluntary movement of skeletal muscle Autonomic Nervous Sys: Controls involuntary movement such as respiration and heart beat
Cells of the Nervous System The cells that carry the messages throughout the nervous system are called neurons
Parts of a Neuron
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Parts of a Neuron - Dendrites Branched projections of a neuron that receives signals from other neurons. Sends signals to the cell body.
Parts of a Neuron - Cell Body The cell body contains the nucleus and other organelles. Dendrites branch off of the cell body.
Parts of a Neuron - Axon The axon is a long, projection of the neuron that conducts the electrical impulse away from the cell body
Parts of a Neuron - Myelin Sheath Myelin forms a layer around the axon and functions to increase the speed of electrical impulses along axon
Parts of a Neuron - Schwann Cells Schwann cells form myelin, which help conduct nerve impulses along the axon
Parts of a Neuron - Nodes of Ranvier Nodes of Ranvier are gaps between the myelin sheaths. Electrical impulses jump from node to node, which helps to increase the speed of conduction.
Parts of a Neuron - Axon Terminals Axon terminals are the end branches of a neuron. Chemicals called neurotransmitters are transferred from one neuron to the next at the axon terminals.
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How does the electrical signal travel along the axon? YouTube The Schwann Cell and Action Potential Action Potential
Action Potential Neuron is stimulated by another neuron or by the environment. Positively charged sodium ions flood in and the inside becomes temporarily more positive. As the impulse passes, potassium ions flood out restoring the resting potential.
What happens when the impulse reaches the end of the neuron? The axon terminal ends at the synapse
Synapse A structure that permits a neuron to pass a electo-chemical signal to an adjacent neuron.
What happens at the Synapse? The electrical activity is converted into the release of a chemical (neurotransmitter), which binds to receptors
Propagation of the Nerve Impulse 1 2 3 Dendrites Cell Body Axon (Action Potential) Axon Terminal 4 7 6 5 Receptor Neurotransmitter Synapse
YouTube Nerve Impulse Animation
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3 Types of Neurons Sensory Interneuron Motor
Sensory Neuron Sensory neurons carry impulses from the senses to the brain and spinal cord
Interneuron Interneurons connect sensory and motor neurons and carry impulses between them
Motor Neuron Motor neurons carry impulses from the brain and spinal cord to muscles and glands
An involuntary and instantaneous movement in response to a stimulus Examples: Blinking, Knee-jerk reflex, Shivering, Sneeze, Yawn, Cough
Reflex Arc Stimulus to sensory neuron to interneuron to motor neuron Occurs quickly by activating spinal motor neurons without going through the brain
YouTube Video Reflex Arc
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