UNIT II: THE HUMAN BRAIN

1. UNIT II: THE HUMAN BRAIN

2. How many cells are in the human brain? • 1 trillion! • Two categories: • Glial Cells • Neurons 1/15

3. Glial Cells • Three Functions: • Provide scaffolding to support both developing and mature neurons. • Wrap around neurons to form insulation from electrical signals • Releasing chemicals that influence neuron growth • Make up 90% of cells in brain! 2/15

4. Neurons • 100 billion cells - both sends and receives messages and signals (up to 268 mph!) • Allows us to: • Receive sensory information • Control muscle movement • Regulate digestion • Release hormones • Complete mental processes (thinking, etc.) 3/15

5. Neurons (cont) • Each neuron has hundreds of connections • Approximately 100 trillion neural connections in the brain • Which is more: the world’s communications, or the brain’s? • 0.00005% 4/15

6. Neuron Growth • Humans born with all our neurons that slowly die over our lifetime. • What two areas of the brain does new research suggest canregrow? • Hippocampus and olfactory bulb • Humans do have the ability to rewire our brains -> recover from traumatic event 5/15

7. Alzheimer’s Disease • Excessive buildup of protein amyloid destroys neurons faster than body can repair them. • All people produce amyloid, Alzheimer’s patients cannot get rid of it • Teeth plaque • Only “cure” right now is to slow or stop amyloid buildup 6/15

8. Neurons – Structure and Function • Cell body – egg-shaped structure that provides fuel, manufactures chemicals, maintains working order in the neuron, contains neurons DNA 7/15

9. Neurons – Structure and Function • Dendrites – Branchlike extensions; receive signals from cells or other neurons and pass them to the cell body. 8/15

10. Neurons – Structure and Function • Axon – single threadlike structure, carries messages to other neurons, organs, or muscles. Can be the length of the width of a human hair, or over 3 feet! 9/15

11. Neurons – Structure and Function • Myelin Sheath – looks like separate tube-like segments composed of fatty tissue. Prevents interference from other electrical signals and helps signals travel faster. 10/15

12. Neurons – Structure and Function • Terminal bulbs – look like tiny bubbles at the end of axon’s branches. Acts like a tiny container that stores neurotransmitters. Do not actually touch any neighboring organs, muscles, or cells. 11/15

13. Neurons – Structure and Function • Synapse – Infinitely small gap between terminal bulb and its neighboring organ, muscle, or other neural cells. Terminal bulbs eject neurotransmitters into the synapse to send messages. 12/15

14. What’s Wrong Here? 13/15

15. Reattaching Limbs • Limbs can be reattached because of something we call nerves. • In whole body except brain/spinal cord • String-like bundles of axons and dendrites • Carry messages from senses, skin, muscles, and organs 14/15

16. Reattaching Limbs • Nerves (but not neurons) have the ability to regrow • Gives us the ability to reattach limbs • Difference between nerve and neuron: • Neuron is individual cell • Nerve is a group of neurons • Think of nerves as the superfast lane of highway neurons use to get signals to your brain 15/15