Understanding Neurons in Nervous System

1. Nervous System Monica Hurtado Taylor Gallo Vanessa Alfaro Steven Nuno Period:2

2. Neuron • Function: To sense changes in their surroundings and respond by transmitting nerve impulses along cellular processes to other neurons or to muscles and glands. • The complex patterns in which the neurons connect with each other and with muscle and gland cells they can coordinate, regulate, and integrate many body functions.

3. Structure: • Dendrites are treelike extensions that help increase the surface area of the cell body. They receive information from other neurons and transmit electrical stimulation to the soma. • The soma is where the signals from the dendrites are connected and passed on. • The axon hillock is located at the end of the soma and controls the firing of the neuron. • The axon is the elongated fiber that extends from the cell body to the terminal endings and transmits the neural signal. • The terminal buttons are located at the end of the neuron and are responsible for sending the signal on to other neurons. • Synapse is a located at the end of the terminal button .Neurotransmitters are used to carry the signal across the synapse to other neurons.

5. Classification of Neurons Structural differences: 1.Bipolar neurons: • Cell body of a bipolar neuron has only two processes, one rising from wither end • One is an axon and the other is a dendrite. • Found within specialized parts of the eyes, nose, and ears. 2. Unipolar neurons • Single process extending from its cell body. • Process divides into two branches, but functions as a single axon. • Cell bodies of cell unipolar neurons aggregate in specialized masses of neuron tissue called ganglia, which are located outside of the brain and spinal cord. 3. Multipolar neurons • Many processes arising from their cell bodies. • Only one is an axon the rest are dendrites. • Most neurons that cell bodies lie within the brain or spinal cord are of this type. 4.Pyramidal neurons • The cell body, or soma of the pyramidal neurons has a distinct shape that gives them their name. • In fish, birds, reptiles and mammals. • Made up of a cell body attached to an axon and dendrites. • Both the axon and dendrites undergo extensive branching.

7. Functional differences: 1.Sensory Neurons • Carry nerve impulses from peripheral body parts to the brain or in spinal cord. • At their ends the dendrites of these neurons or specialized structures associated with them act as sensory receptors, detecting changes in the outside world or within the body. • When stimulated, sensory receptors trigger impulses that travel on sensory neuron axons into the brain or spinal cord. 2. Interneurons • Lie within the brain or spinal cord • Multipolar and form links between other neurons • Transmit impulses from one part of the brain or spinal cord to another. • May direct incoming sensory impulses to appropriate regions. Other incoming impulses are transferred to motor neurons. 3.Motor neurons • multiploar and carry nerve impulses out of the brain or spinal cord to effectors; structures that respond, such as muscles or glands.

9. Classification of Neuroglial Cells • Neuroglial Cells • Structure and function • Referred to as glial cells • Different from nerve cells • Don’t participate directly in synaptic interactions • Maintain the signaling abilities of neurons • Surrounds and supports neurons that are in the central nervous system • Main function is to insulate neurons from each other

10. Classification(cont.) • 6 types • oligodendrocytes • astrocytes • ependymal cells • microglia • schwann cells • satellite cells

11. Oligodendrocytes Possesses slender cytoplasmic extensions. Many axons in the CNS are completely sheathed in this process.

12. Astrocytes

13. EpendymalCells

14. Microglia

15. Schwann Cells

16. Satellite Cells

17. Classification of Nervous System • Nervous system- The system of nerves and nerve centers(the brain, spinal cord, nerves, and ganglia) • Peripheral: • Nervous system that consists of the nerves and ganglia outside of the brain and spinal cord • Autonomic: • System of nerves and ganglia that control involuntary functions, consisting of sympathetic and parasympathetic portions • Also known as the involuntary nervous system • Controls visceral functions • Heart rate • Digestion • Salvation • Respiratory rate

18. Action Potiental • Travels down the axon • There is a change in polarity across membrane. • The sodium channels open and sodium moves into axon.

19. Resting Potential • Is not an equilibrium potential. • Relies on the constant expenditure of energy. • Nothing stimulated to the nerve impulse. • Negative sign is the inside of the cell which is due to negative charges in the cell membrane. • Sodium ions and potassium ions diffuse across the cell membrane.

20. Depolarization Phase • Is a positive going change in a cell’s membrane potential. • In neurons and other cells, a large enough depolarization may result in an action potential. • Hyperpolarization is the opposite of depolarization.

21. Hyperpolarizing Phase • Is a change in a cells membrane potential that makes it more negative. • Opposite of depolarization. • It inhibits action potentials by increasing the stimulus required to move the membrane potential to the action potential threshold.

22. Threshold Potential • Level where the membrane potential must be depolarized in order to initiate an action potential. • Regulate and propagate signaling in both the central and peripheral nervous system. • “fires up” an action potential.

23. Refractory and Neurotransmitter • The refractory period is a nerve impulse condition is when neuron responds or not. • When it does respond it responds fully. • The neurotransmitter has acetylcholine • The acetycholine stimulates skeletal muscle contraction.

24. Bibliography • http://www.innerbody.com/image/nervov.html • http://people.eku.edu/ritchisong/301notes2.htm • http://www.ncbi.nlm.nih.gov/books/NBK10869/ • http://blustein.tripod.com/ • http://www.britannica.com/EBchecked/topic/279678/hyperpolarization • http://faculty.washington.edu/chudler/ap.html • Holes Book