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The Nervous SystemNeural Anatomy
Neurons: The Building Blocks
of the Nervous System
Module 7: Neural and Hormonal Systems
Nervous System
• The electrochemical communication system of the body
• Brings information to the brain from the senses
• Sends messages from the brain to the body to enact behavior
Neuron• The basic building block of the
nervous system -- a nerve cell
• Neurons perform three basic tasks
–Receive information
–Carry the information
–Pass the information on to the next neuron
Types of Neurons• Afferents, or “sensory neurons”,
carry information from the body to the brain
Types of Neurons
• Interneurons, found in the spinal cord and the brain, interpret the incoming information and determine the next course of action
Types of Neurons• Efferents, or “motor neurons”,
carry information from the spinal cord or the brain to the rest of the body in order to initiate behavior
Parts of the Neuron
Parts of the Neuron - Dendrites
Parts of the Neuron - Soma
Parts of the Neuron - Axon
Parts of the Neuron – Myelin Sheath
Parts of the Neuron - Terminals
Neuron
Neuron
The Neural Network
How does the whole system fit together?
• A neuron is considered at “resting potential” when there is no sensory input and it is awaiting stimulus.
A Neural Chain
• Special receptors in each of the five senses detect stimuli from the outside world.
• When a neuron receives enough information to pass on, it has reached its “action potential” and fires off the message to the next neuron in the link
• Once a neuron fires, it must re-set momentarily in order to receive another message. This re-set period is called “refraction”. It cannot fire during this period.
A Neural Chain
•Sensory neurons carry all of the input to the spinal cord.
A Neural Chain
• Interneurons in the spinal cord and the brain process the information and decide the best course of behavior.
A Neural Chain
• Motor neurons from the brain travel back down the spinal cord and out to the appropriate parts of the body with the appropriate behavior instructions.
A Neural Chain
Neural Communication: The Neural Impulse
A neuron firing is like a toilet flushing
1. Like a Neuron, a toilet has a resting potential. The toilet is “charged” when there is water in the tank and it is capable of being flushed.
Neuron firing like a Toilet
2. Like a Neuron, a toilet has an action potential. When you flush, an “impulse” is sent down the sewer pipe.
Neuron firing like a Toilet1. Like a neuron, a toilet has a
refractory period. There is a short delay after flushing when the toilet cannot be flushed again because the tank is being refilled
2. Like a Neuron, a toilet operates on the all-or-nothing principle – it always flushes with the same intensity, no matter how much force you apply to the handle
Communication Between Neurons
Module 7: Neural and Hormonal Systems
Synapse
• The electrical message from the dendrite travels down the axon to the terminal buttons. Here, it changes into a chemical message to be transferred to the next neuron.
• The tiny, fluid filled gap between the axon terminal of one neuron and the dendrite of another neuron is called the synapse.
Neurotransmitters
• A chemical messenger that travels across the synapse from one neuron to the next
Neurotransmitters
• http://depression.emedtv.com/depression-video/the-brain-and-its-chemicals-video.html
• http://www.youtube.com/watch?v=p5zFgT4aofA
Acetylcholine (ACh)
• Enables muscle action, learning, and memory
• Undersupply, as ACh-producing neurons deteriorate, marks Alzheimer’s disease
Dopamine• Influences movement, learning, attention,
and emotion• Helps control the brains reward and
pleasure center!
• Excessive dopamine receptor activity is linked to schizophrenia; a lack of dopamine produces the tremors and lack of mobility of Parkinson’s disease
Serotonin
• Affects mood, hunger, sleep, and arousal
• Undersupply is linked to depression; Prozac and other anti-depressants raise serotonin levels
Norepinephrine
• Helps to control alertness and arousal
• Undersupply can depress mood
Endorphins
•Natural opiates that are released in response to pain and vigorous exercise
Endorphins
Touch Neuron to review
• http://www.childrenshospital.org/research/_neuron/index.html
http://www.childrenshospital.org/research/_neuron/index.html
The Structure of the Nervous System
The Nervous System
Central Nervous System (CNS)
• The brain and spinal cord
• The brain is the location of most information processing.
• The spinal cord is the main pathway to and from the brain.
Spinal Cord
Divisions of the Nervous System
Peripheral Nervous System (PNS)
• The sensory and motor nerves that connect the central nervous system to the rest of the body
• Peripheral means “outer region”
• The system is subdivided into the somatic and autonomic nervous systems.
Divisions of the Nervous System
Somatic Nervous System
• The division of the peripheral nervous system that controls the body’s skeletal muscles
• Contains the motor nerves needed for the voluntary muscles
Divisions of the Nervous System
Autonomic Nervous System
• The division of the peripheral nervous system that controls the glands and muscles of the internal organs
• Monitors the autonomic functions• Controls breathing, blood pressure, and
digestive processes• Divided into the sympathetic and
parasympathetic nervous systems
Divisions of the Nervous System
Sympathetic Nervous System
• The part of the autonomic nervous system that arouses the body to deal with perceived threats and stress
Divisions of the Nervous System
Parasympathetic Nervous System
• The part of the autonomic nervous system that calms the body
• Brings the body back down to a relaxed state
Divisions of the Nervous System
The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System
• Physical Responses
The Sympathetic and Parasympathetic Nervous Systems
