(Neuro)Glial cells- why are they important?

Neurons have a negative “Resting Potential” Nerve impulse = Action Potential Ready… Aim… FIRE!

It’s what moves you!

Structural Classification of Neurons Multipolar neurons – many extensions from the cell body Figure 7.8a

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.

How Neurons Communicate Figure 7.10

Insulated with myelin for speed ----Unmyelinatd axons speed of AP is 10 m/s. ----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). The Myelin sheath (formed by Schwann cells and oligodendrites) why is it important?

Functional Properties of Neurons Irritability – ability to respond to stimuli Conductivity – ability to transmit an impulse The plasma membrane at rest is polarized ◦ Fewer positive ions are inside the cell than outside the cell

Starting a Nerve Impulse Depolarization – a stimulus depolarizes the neuron’s membrane A depolarized membrane allows sodium (Na + ) to flow inside the membrane The exchange of ions initiates an action potential in the neuron Figure 7.9a–c

The Action Potential If the action potential (nerve impulse) starts, it is propagated over the entire axon K+ rush out of the neuron after Na+ ions rush in, which repolarizes the membrane The Na+ - K+ pump restores the original configuration ◦ This action requires ATP

Nerve Impulse Continues b/w Neurons Impulses are able to cross the synapse to another nerve ◦ Neurotransmitter is released from a nerve’s axon terminal ◦ The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter ◦ Action potential is started again in the dendrite

Disease  Multiple sclerosis destroys myelin sheaths.  Sodium (Na) channels are only at nodes.  Neuron can’t have an action potential or nerve impulse.

Anesthetics = action potential Local Local (Novocain, Xylocaine) attach to Na+ channel. Na+ can’t enter cell. General anesthetic (ether, chloroform) open K + channels, K + exits as fast as Na+ enters General anesthetic (ether, chloroform) open K + channels, K + exits as fast as Na+ enters

Keep those action potentials firing! Draw a diagram that outlines action potential Words to know: Action Potential Resting potential DepolarizationPolarization Sodium potassium pump

The Reflex Arc Reflex – rapid, predictable, and involuntary responses to stimuli Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector Figure 7.11a

Types of Reflexes and Regulation Autonomic reflexes ◦ Smooth muscle regulation ◦ Heart and blood pressure regulation ◦ Regulation of glands ◦ Digestive system regulation Somatic reflexes ◦ Activation of skeletal muscles

Central Nervous System (CNS) CNS develops from the embryonic neural tube ◦ The neural tube becomes the brain and spinal cord ◦ The opening of the neural tube becomes the ventricles  Four chambers within the brain  Filled with cerebrospinal fluid

Reflex Arc

Receptors Sensory neuron Relay neuron Motor neuronEffectors Reflex Arc

Words to know: Reflex arc ReceptorEffectorsIntegrationAfferentEfferent

Structural Classification of Neurons Multipolar neurons – many extensions from the cell body Figure 7.8a

Structural Classification of Neurons Bipolar neurons – one axon and one dendrite Figure 7.8b

Structural Classification of Neurons Unipolar neurons – have a short single process leaving the cell body Figure 7.8c