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Two Main Parts of the Nervous System Central Nervous System – Brain – Spinal Cord Peripheral Nervous System – Nerve cells that send messages between the central nervous system and all the parts of the body
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Neurons and Neural Communication
The Nervous System
The Nervous System• Our nervous system is involved
in thinking, dreaming, feeling, moving, sleeping, and more
• Regulates internal functions
• When we learn a new behavior or new information, it registers the experience and changes to store it
Two Main Parts of the Nervous System
• Central Nervous System– Brain– Spinal Cord
• Peripheral Nervous System– Nerve cells that send messages
between the central nervous system and all the parts of the body
The Nervous System
The Central Nervous System
The Brain The Spinal Cord
The Peripheral Nervous System
The Somatic Nervous System
The Autonomic Nervous System
The Sympathetic
Nervous System
The Parasympathetic Nervous System
The Nerve Cells
• Neurons
– Send and receive messages from other structures throughout the body (like muscles and glands)
– Each of us have more than 100 billion neurons, most of which are in the brain
Parts of the Neuron• The Cell Body (Soma)
– Produces the energy to fuel the activity of the cell– Nucleus is in the cell body
• Axon– Carries messages away from the cell body– One axon per cell body– Covered with a fatty insulation known as the “Myelin
Sheath”• Helps speed up the transmission of messages• Protects Axon
– Axon terminals branch from the end of the axon
• Dendrites– Thin fibers branching out from the cell body– Carries information to the cell body
Neural Communication• Messages are sent from the axon terminals of one neuron
to the dendrites of other neurons
– Messages cross the SYNAPSE• the space between the axon terminal of one neuron and the dendrite
of another neuron
– Messages can only travel in one direction
– New synapses can develop between neurons when we learn something new
– Synapse disruption can occur concussions
The Message Sent: Neurotransmitters
• Chemicals stored in sacs, or vesicles, in the axon terminals
• Neurons can fire neurotransmitters hundreds of times per second
• Chemical neurotransmitters are converted into an electric pulse which travels the length of the neuron
Neurotransmitters• Acetylcholine
– Control of muscles
• Dopamine– Motor behavior– Too little plays a role in Parkinson’s disease, as seen in the
tremors and rigid, uncoordinated movements– Too much contributes to schizophrenia
• Noradrenaline– Prepares the body for action
• Serotonin– Emotional arousal and sleep
The Central Nervous System
• Consists of the neurons of the brain and spinal cord
• Spinal cord is a column of nerves (about as thick as your thumb) which is protected by the bones of the spine– Responsible for spinal reflexes, like removal of your
hand from a hot stove• response faster than the brain can register the pain of being
burned
The Peripheral Nervous System
• Responsible for transmitting messages between the central nervous system and all other parts of the body
• Divided into two parts:– The Somatic Nervous System– The Autonomic Nervous System
The Somatic Nervous System
• Transmits sensory messages to the central nervous system
• Activated by touch, pain, changes in temperature, and changes in body position
• Enables us to experience sensations of hot/cold and to feel pain/pleasure
The Autonomic Nervous System• Autonomic = “occurring involuntarily”
• Regulates the body’s vital functions– Heartbeat– Breathing– Digestion– Blood pressure
• Two divisions:– Sympathetic Nervous System– Parasympathetic Nervous System
Sympathetic vs. Parasympathetic
• Prepares the body for action “Fight or Flight”– Suppresses
digestion– Increases heart
rate– Increases
respiration– Elevates blood
pressure
• Calms the body after emergencies– Normalizes heart
rate– Normalizes blood
pressure– Slows breathing– Normalizes
digestion
The Nervous System
The Central Nervous System
The Brain The Spinal Cord
The Peripheral Nervous System
The Somatic Nervous System
The Autonomic Nervous System
The Sympathetic
Nervous System
The Parasympathetic Nervous System
