1 / 15

Neurons and the Reflex Arc

Neurons and the Reflex Arc. Structure and Function of the Nerve Cell. Neurons work by changing the concentration of positive and negative charges inside and outside the cell. They are in fact run on electricity. . Structure and Function of the Nerve Cell.

gay
Download Presentation

Neurons and the Reflex Arc

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Neurons and the Reflex Arc

  2. Structure and Function of the Nerve Cell Neurons work by changing the concentration of positive and negative charges inside and outside the cell. They are in fact run on electricity.

  3. Structure and Function of the Nerve Cell When at rest there is a high concentration of sodium outside the cell and a high concentration of potassium inside the cell. Inside the cell are other anions such as chlorides making the inside of the cell negative. The membrane is more permeable to potassium and this is constantly diffusing out.

  4. Functioning of the Neuron: In a resting state (not firing) the neuron is positively charged on the outside of the membrane. The inside of the membrane has a slight negative charge. Sodium and potassium channels are closed.

  5. Functioning of the Neuron: When the neuron fires we say there is a wave of depolarization that occurs along the axon or an “action potential”. When this happens, sodium ions are allowed to diffuse through the axon, neutralizing the difference in charge on either side of the axon membrane.

  6. Functioning of the Neuron: When the positive sodium ions enter the nerve cell, they are attracted forward to the negative ions along the inside of the cell membrane. This triggers the sodium pumps to open and propagate the action potential along the axon.

  7. All or Nothing Action Potential

  8. Functioning of the Neuron: Once the neuron has fired it is called “refractory” and cannot fire again until the sodium has been pumped out of the neuron and potassium back in. Each sodium and potassium pumps pump 3 sodium ions and 2 potassium ions while using 1 ATP.

  9. Speeding Up the System • Myelinated sheath • Reflex Arc

  10. Myelin Sheath The myelin sheath acts as an insulator and allows depolarization to jump down the axon very quickly from each Node of Ranvier. Schwann cells, composing the sheath cannot repair themselves if damaged.

  11. Reflex Arc

  12. Reflex Arc The reflex arc carries out required movement without the brain’s involvement. A sensory neuron is activated with a strong stimulus and sends an action potential to the spinal cord. An interneuron in the CNS shorts the signal and stimulates a motor neuron to act.

  13. Patellar Reflex Arc Also known as the knee jerk reflex, this can be induced by striking someone’s relaxed knee while their leg dangles. Why would humans have developed this reflex? Try it! (Mr. LeBreton does not have this reflex.)

  14. Homework: 1) Research another reflex that you can try on a friend in class tomorrow. 2) Read “Neurons and the Reflex Response” Page 140 Read Page 147 up to, but not including page 150 “The Synapse” 3) Answer: Page 146 Question 5 Page 151 Question 3, 4, 5, 6

More Related