by: sam biller + ryan coughlin. neurons are nerve cells that transfer information within the body....
TRANSCRIPT
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Chapter 48 - Neurons, Synapses
and Signaling
By: Sam Biller + Ryan Coughlin
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Overview of Neurons
• Neurons are nerve cells that transfer information within the body.
• The structure of Neurons allows them to use pulses of electrical current to receive, transmit, and regulate the flow of information over long distances.
• Neurons transmit sensory information, control heart rate, coordinate hand and eye movement, record memories, generate dreams and more.
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Neuron Organization and Structure:Cnidaria - Sea Anemone
• Movements used by a net of nerves
• No Brain or Nervous System
• Cnidarians detect and respond to stimuli from all directions. Sensing objects by touch.
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Neuron Organization and Structure:Annelida - Segmented Worm
• No brain, have a ganglionic mass
• Bundle of nerves running
down body
• Branches into other bundles
• Sensory organs on skin
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Neuron Organization and Structure:Arthropoda - Crustaceans
• Very similar tothe annelidas.
• Have a brain thatbraches off into nerve
bundles and cord
• These each have a specific function
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Neuron Organization and Structure:Mammalian - Humans
• Bigger more complexbrain
• Nerves branched allover body
• Messages travel from brain along nerves
• Electric signals traveldown the neurons
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Action Potential
The Sodium and Potassium channels are closed.
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• A reduction in the magnitude of the membrane potential is called a depolarization.
• Sodium Channels in a resting neuron to open, membrane's permeability to Sodium Ions increases.
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• After the Membrane has been crossed the positive and negative feedback switch along the membrane because of the Sodium Ions positive charge.
• Potassium Channels remain closed.
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• Sodium Channels become inactivated blocking the sodium ions flow.
• Most Potassium Channels become open switching the positive and negative feedback back to normal.
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• The Sodium Channels remain closed, but are unblocked.
• Some Potassium remain open causing the membrane's permeability to potassium ions to be higher than at rest.
• As the Potassium channels begin to close and sodium channels remain closed the membrane returns to its resting state.
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Neurons communicate with other cells at Synapses
• Action potentials are not transmitted from neurons to other cells.
• Transmission does occur at the synapses.
• Electrical and Chemical Synapses transmit information to other cells.
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Electrical Synapses
• Allows the electrical current to flow directly from one neuron to the other.
• Vertebrates and Invertebrates, electrical synapses synchronize the activity of neurons for rapid behaviors.
• Electrical Synapses take place in the vertebrate brain.
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Electrical Synapses
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Chemical Synapses
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Chemical Synapses continued...
1. The action potential arrives in the presynaptic membrane depolarizing it.
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Chemical Synapses continued...
2. Depolarization opens voltage-gated channels, triggering Ca2+ in the membrane.
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Chemical Synapses continued...
3. Increased Ca2+ concentration causes the synaptic vesicles to fuse with the presynaptic membrane, releasing the neurotransmitters into the synaptic cleft.
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Chemical Synapses Continued...
4. The neurotransmitters then bind to the ligand-gated ion channels in the postsynaptic membrane which binding triggers opening, allowing Sodium and Potassium to diffuse through.
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Chemical Synapses Continued...
• Neurotransmitter is not part of the ion channel
• Neurotransmitter binds to metabotropic receptor
• Activates a signal transduction pathway in the postsynaptic membrane involving a second messenger
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Neurotransmitters
100 different types Acetylcholine – Amino Acids Biogenic Amines Neuropeptides Gases
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Diseases
Motor Neuron Diseases (MND) - destroy neuron cells which are important in health and everyday life and functioning.
MND controls: voluntary muscle actions, such as swallowing, breathing, speaking, talking, hand gestures, and walking.
Examples of Diseases:
Amyotrophic lateral sclerosis (ALS or Lou Gehrig’s Disease)
Progressive Muscular Atrophy - Causes Weaknesses in the hands and the lower body.
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Diseases
Epilepsy – a brain disorder in which a bunch of nerve cells start to signal abnormally
When the signals happen so fast, sometimes as quick as 500 times per second, a person has a seizure.
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Diseases Continued...
There is no cure for Neuron related diseases.
There is no cause for Neuron related diseases, but some are inherited.
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Work Cited
• "Motor Neuron Diseases." - Symptoms, Causes, Treatments. Web. 25 Mar. 2012. <http://www.localhealth.com/article/motor-neuron-diseases>.
• Reece, Jane B., and Neil A. Campbell. Biology. Boston, MA: Cummings, 2011. Print.
• "Google Images." Google Images. Web. 25 Mar. 2012. <http://images.google.com/>.
“MedicineNet.com.”MedicineNet. Web. 25 Mar.2012.<http://www.medicinenet.com/sizure/article.htm.