(Neuro)Glial cells- why are they important?
Make up 85% of the nervous system Clear away cellular debris Microglia repair Astrocytes create the blood brain barrier Oligodendrocytes help with the myelin sheaths 10 Ready Aim FIRE! Neurons have a negative Resting Potential
Nerve impulse = Action Potential Resting potential= -70 mV Action potential= All or none law 5 The nerve impulse: 100 million messages per second
50 billion neurons 10, 000 miles of fibers in 1 cubic inch. Stretched out goes to the moon and back. The Myelin sheath (formed by Schwann cells and oligodendrites) why is it important?
Myelin sheath is provided by which two neuroglia cells? Schwann and oligodendrocytes Acts as insulation Action potential occurs only at the unmyelinated regions called the nodes of Ranvier.This is where the sodium channels are located Insulated with myelin for speed ----Unmyelinatd axons speed of AP is 10 m/s. Myelin sheath has spaces= Nodes of Ranvier. ----The AP jumps from node to node (speed 120 m/s). Functional Properties of Neurons
Irritability ability to respond tostimuli Conductivity ability to transmit animpulse The plasma membrane at rest ispolarized Fewer positive ions are inside thecell than outside the cell Starting a Nerve Impulse
Depolarization astimulus depolarizesthe neuronsmembrane A depolarizedmembrane allowssodium (Na+) to flowinside the membrane The exchange of ionsinitiates an actionpotential in theneuron Figure 7.9ac The Action Potential If the action potential (nerve impulse)starts, it is propagated over the entireaxon K+ rush out of the neuron after Na+ ionsrush in, which repolarizes the membrane The Na+ - K+ pump restores the originalconfiguration This action requires ATP http://www.sumanasinc.com/webcontent/ animations/content/synapse.html
animations/content/carrier_proteins.html Nerve Impulse Continues b/w Neurons
Impulses are able to cross the synapseto another nerve Neurotransmitter is released from anerves axon terminal The dendrite of the next neuron hasreceptors that are stimulated by theneurotransmitter Action potential is started again in thedendrite How Neurons Communicate
Figure 7.10 Disease Multiple sclerosis destroys myelin sheaths.
Sodium (Na) channels are only at nodes. Neuron cant have an action potential or nerveimpulse. Disease that impact the myelin sheath, like MS, affect the action potential which impacts the action potential of that neuron.People with MS ultimately experience pain and decrease motor function in the areas of their body where the myelin sheath of the neurons has been effected. Anesthetics = action potential
Local (Novocain,Xylocaine) attach toNa+ channel. Na+cant enter cell. Anesthetia stops the action potential, stop the action potential and do you feel pain? NO why? the signal fro pain is stopped.Both local and general anesthesia prevent the change in polarity along the axis of the neuron. General anesthetic (ether, chloroform) open K + channels, K + exits as fast as Na+ enters The Reflex Arc Reflex rapid, predictable, andinvoluntary responses to stimuli Reflex arc direct route from a sensoryneuron, to an interneuron, to an effector Figure 7.11a Types of Reflexes and Regulation
Autonomic reflexes Smooth muscle regulation Heart and blood pressureregulation Regulation of glands Digestive system regulation Somatic reflexes Activation of skeletal muscles Reflex Arc Reflex Arc Receptors Sensory neuron Relay neuron Motor neuron
Effectors