Nervous System Communication. Kid Concussions In The News.
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Transcript of Nervous System Communication. Kid Concussions In The News.
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Nervous System Communication
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Kid ConcussionsIn The News
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Neurons
• Nerve cells
• Parts of neurons– Cell body– Long extensions (fibers=dendrites or axons)
• Message = nerve impulse
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Animal Nervous Systems
• Sponges – no nervous system
• Other animals all have neurons in systems
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Nerve Net
• In all cnidarians
• Interconnected nerve cells
• No brain
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Ringlike Nervous System
• In echinoderms
• Ring with 5 radiating nerves
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Ladderlike Nervous System
• In many Platyhelminthes
• Some have distinct brain (ganglia)
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Annelid Nervous System• Segmental ganglia
– Ganglia = aggregations of nervous tissue
• Ventral nerve cord & brain
Arthropod
Mollusks(depends
level of activity) some have giant fibers
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Vertebrate Nervous System
• Central nervous system– Brain & spinal cord
• Peripheral nervous system– Nerves to & from CNS
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Nerve Cells(Neurons)
• Cell body– Contains nucleus and organelles– Produces substances necessary for cell to live &
function• Axon (conducts or passes on impulse)
– Long cell extension– May have myelin covering
• Dendrites (receive impulse) – Usually short cell extensions– No myelin covering– most neurons have multiple dendrites
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Sensory Neurons• Receive information from sense organ receptors• Transmit to the central nervous system• Cell bodies of sensory neurons lie near the CNS
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Motor Neurons• Transmit commands away from CNS to effector (muscle or
gland)• Each neuron has one long axon• Cell bodies on most motor neurons lie in or near CNS
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Interneurons • Located within brain & spinal cord• Integrate information• Axons may or may not be myelinated• usually axons are shorter than those in PNS
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Neuroglia • Nerve support cells
• Provide support, protection, & nutritional stability
• Schwann cells (special neuroglial cells)– Found around axons– Produce myelin sheath
• Oligodendrocytes – produce myelin sheath around some CNS axons
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Myelin Sheath• Insulates axon• Nodes of Ranvier-allows impulse to move
at a greater speed along axon• Uninsulated areas- no myelin sheath
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Nerve Impulses• Electrical signals transmitted along
membranes of nerves
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Resting Potential
• Neuron is electrically charged at rest
• Outside is positively charged
• Inside is negatively charged
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Sodium-Potassium Pump
• Proteins embedded within cell membrane
• Moves sodium to the outside
• Moves potassium to the inside
• Maintains resting potential
• Requires energy (ATP)
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Action Potential
• Nerve impulse is started by a stimulus
• Stimuli cause movements of ions through membrane
• Threshold potential– Sufficient stimulation to depolarize membrane
• Action potential– Rapid reversal of membrane electric potential
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Nerve Transmission• Action potential at one point depolarizes next area• Depolarization moves in self-propagating wave
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Saltatory Conduction• Nerve impulse jumps & moves faster
along myelinated axon
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Synapse • Area where nerve communicates
• Transfers message– Another neuron– An effector
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Synaptic Cleft• Neurons do not touch other neurons or
effector cells• Nerve impulse must cross gap (electrical
signal is changed to a chemical signal)
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Neurotransmitters • Organic molecules (> 60 different chemicals)• Transfer message across synaptic cleft• Attach to receptors on target cell
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Neuromuscular Junctions• Synapse between neuron & skeletal muscle• Neurotransmitter is aceytylcholine
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Neuron to Neuron Connections
• Uses many different neurotransmitters
(such as dopamine, norepinephrine, serotonin)
• Some cause different effects– Excitatory synapse – continuation of impulse– Inhibitory synapse – reduce ability to depolarize
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Integration of Nerve Impulses• Summed impulses determine if
postsynaptic neuron will depolarize
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Human Nervous System
• Central nervous system– Brain– Spinal cord
• Peripheral nervous system– Brings messages to & from CNS– Somatic nervous system – voluntary– Autonomic nervous system - involuntary
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Central Nervous System
• Integrates sensory & motor impulses
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Spinal Cord• Connects peripheral nervous system with brain• Receives information via spinal nerves• Includes reflex arcs
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CNS Protection - Meninges
• Layers of membranes– Dura mater– Arachnoid– Pia mater
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Peripheral Nervous System• Sensory & motor impulses• Cranial nerves communicate directly with brain,
some are strictly sensory or motor, some are mixed.
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Spinal Nerves• Sensory & motor nerve fibers
• 31 pairs and all are mixed nerves
• Travel directly to spinal cord
• Nerves are bundled to form mixed nerves
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Motor Neuron Systems
• Somatic nervous system, part of PNS– Voluntary– Movements of skeletal muscles– requires a single motor neuron– Reflex = automatic response to nerve
stimulation
• Autonomic nervous system, part of PNS– Involuntary motor pathways– requires two motor neurons
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Divisions of the Autonomic Nervous System
• Parasympathetic – Acetylcholine is the neurotransmitter– Prevails during periods of inactivity– Housekeeping
• Sympathetic – Norepinephrine is the neurotransmitter– “fight or flight”– Responds to stress– Prepares body for action
• Parasympathetic & sympathetic together help to maintain homeostasis
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Psychoactive Drugs• Affect action of neurotransmitters
In specific parts of the brain
• Some are abused
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Drug Addiction
• Chronic use (or abuse) of psychoactive drugs• Person becomes physically dependant• Drug use tends to increase due to drug
tolerance
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End Chapter 32