neurons- the matter of the nervous system
DESCRIPTION
The Nervous system controls the entire body It is the interface between stimulus and response Allows animals to interact with their environment Brain and spinal cord: central nervous system (CNS) Other nerves: peripheral nervous system (PNS)TRANSCRIPT
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Neurons- The matter of the nervous system
Chapter 7: Pgs 120-133
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The Nervous system controls the entire body
• It is the interface between stimulus and response
• Allows animals to interact with their environment
• Brain and spinal cord: central nervous system (CNS)
• Other nerves: peripheral nervous system (PNS)
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The nervous system is the interface between stimulus and response
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The Neuron is the base unit of the nervous system
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Neurons are large cells supported by a variety of glial cells
• Human neurons can be 1m in length
• Potentially thousands of glial cells support a single neuron
• Provide nutrition, support, insulation
• Schwann cells are an example
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Schwann cells are glial cells which protect neurons with myelin
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The 3 kinds of neurons work together to
interface between stimulus and response
• The reflex arc is the simplest neural circuit
• Consists of – 1 sensory neuron– 1 interneuron– 1 motor neuron
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The synapse is the connection point between
neurons• Vesicles sit in
axon terminals, loaded with neurotransmitters
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Some important neurotransmitters
• Acetylcholine- Neuromuscular
• Dopamine-Exitatory• Norepinephrine • GABA- Inhibitory• Serotonin-Regulatory
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Many Drugs copy the action of neurotransmitters
• Methamphetamine is structurally similar to dopamine
• Dopamine involved in learning and reward systems
Dopamine
Methamphetamine
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Many synapses make complex information processing possible
• Cell interactions form logic circuits
• AND, NOT, etc. gates are formable
• Human Brain: 100 billion neurons
• Up to 10,000 synaptic connections/neuron
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Which one of the following statements is false?
A) Sensory neurons convey signals from the CNS to
sensory receptors. B) Motor neurons convey signals from the CNS to
effector cells. C) Interneurons integrate data and relay
appropriate signals to other interneurons or to motor neurons.
D) The PNS includes nerves and ganglia. E) The CNS consists of the brain and spinal cord.
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The Nerve impulse
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The nervous system runs on electricity
• Current- The movement of charge (electrons or ions)
• Voltage- potential energy stored in a charge disparity over distance
• Nervous system uses ions (Na+, K+, Cl-, Ca++) to send signals from one neuron to another
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At rest, neurons must be ready to respond in milliseconds
Water behind a dam is stored potential energy
Charge and concentration gradients hold potential chemical energy
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Neurons have a resting membrane potential
• Negatively charged• Keeps the neuron
poised for instant action• -70mV• Maintained by constant
active transport of ions
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Pumps maintain gradients, channels activate cells
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• Which of the following statements about the sodium-potassium pump is false?
• A) It is a membrane protein. • B) It keeps the concentration of sodium low
inside the cell. • C) It moves sodium across the membrane and
into the cell. • D) It helps maintain the resting membrane
potential. • E) It actively transports potassium into the cell
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Two kinds of ion channels
Ligand-gated ion channels open when bound to a ligand (a neurotransmitter)
Voltage gated ion channels open when the voltage in the cell changes
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Neurons can respond in milliseconds, giving us quick reflexes
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Neurotransmitters are the chemical signals with which neurons
communicate across a synapse• Neurotransmitters bind
to gated ion channels in the cell membrane of the next neuron
• Binding opens the ion channel
• Hydrolysis or reuptake removes the neurotransmitter
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The Nerve Impulse step by step
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Step 1- depolarization causes vesicles to fuse
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Step 2- Fused vesicles release neurotransmitter into the synapse
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Step 3- Neurotransmitters open gated sodium channels, depolarizing cell
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Step 5- Voltage-gated sodium channels pass the signal down the axon
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Voltage-gated channels sit at nodes of Ranvier, making the signal travel faster
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Step 6- Change in voltage at the axon terminal passes the signal on
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Step 7- Potassium channels are opened, re-polarizing the cell for its next response
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Step 8- Ion balance is restored using active transport- the Na+/K+ pump
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What is the functional unit of the nervous system?
• A) dendrite • B) cell body • C) neuron • D) axon • E) synapse
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Depolarization is the activation event
• Depolarization is caused by opening of gated sodium channels
• When depolarized, neurons respond in milliseconds
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Action potentials normally travel along an axon
• A) toward the cell body. • B) away from the cell body. • C) in either direction, depending on the needs
of the animal. • D) away from the synapse. • E) from axons into dendrites.
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Step 0.5: Vesicles were marched down the axon previously by kinesin
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Antidepressants can block reuptake of neurotransmitters
• SSRI- “Selective Serotonin Reuptake Inhibitors”
• Prozac, Paxil, Zoloft, etc.- all SSRI’s
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Sarin nerve gas is an Acetylcholinesterase Inhibitor
• How does it work?• How does it kill people?
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The reflex arc is the most basic neural circuit
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The Ganglion splits the signal to notify the brain
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The human brain has 3 major regions
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Higher thought is compartmentalized to the cerebrum
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Regions of the cerebral cortex are themselves compartmentalized
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A homonculus shows the area of the brain devoted to regions of the body