Did you know?

1. Did you know? • Neurons do not undergo mitosis! • The Nervous System can transmit impulses as fast as 100 meters per second! • If we lined up all the neurons in our body it would be around 600 miles long! • A newborn baby's brain grows almost 3 times larger during the course of its first year!

2. Neurotransmitters & Synapses ARE YOU READY TO RUMBLEEEEEE!?

3. Please Mr. Byrnes, I’m dying to know.. just what is a synapse? • Synapses are the areas where impulses are sent from one neuron to another • Remember that an nerve impulse travels down the axon as a result of depolarizing electrochemical gradients

4. The space between the synaptic knob of one neuron and the dendrite of another • A nerve impulse reaching synaptic knobs triggers release of chemical signals called neurotransmitters

5. Synapses • Several impulses over a short period of time cause neurotransmitters to accumulate in the synapse • Specific levels of neurotransmitter will stimulate the post-synaptic neuron to conduct the impulse • Neurotransmitters are decomposed by enzymes, clearing the synapse for the next impulse

6. Synapses Some neurons and their transmissions are excitatory & some are inhibitory. Excitatory: make the postsynaptic membrane more permeable to sodium & create “normal” action potential

7. Synapses Some neurons and their transmissions are excitatory & some are inhibitory. Inhibitory: make the postsynaptic membrane more permeable to potassium & prevent neurons from becoming active

8. Neurotransmitters: chemicals that transmit signals from a neuron to a target cell across a synapse

9. Neurotransmitters • All listed below are classified as monoamines: Acetylcholine: major excitatory neurotransmitter in the brain; makes post-synaptic membranes more permeable to Na+ ions; destroyed by cholinesterase enzyme Adenosine: inhibitory; promotes sleep

10. Neurotransmitters • All listed below are classified as monoamines: Dopamine: involved in motor systems and emotional behaviour; increases heart rate and blood pressure Serotonin: involved in sleep regulation, appetite, mood; has multiple receptors body-wide

12. Drugs Effects Agonists & Antagonists: either mimic or block neurotransmitters • morphine is an endorphin agonist • amphetamines are monoamine agonists • LSD is a serotonin antagonist; caffeine is an adenosine antagonist

13. Drug Effects Monoamine oxidase (MAO) inhibitors: block re-absorption of neurotransmitters so that they stay in the synapse and continually bind to the post-synaptic membrane • cocaine blocks dopamine re-absorption, resulting in reduction of the number of dopamine receptors

14. Drug Effects Stimulants & Depressants: change the rate of transmission of neurotransmitter across the synapse • caffeine & diazepam are stimulants • aspirin & strychnine are depressants

15. Nervous System Disorders Epilepsy • syndrome characterized by episodic abnormal electrical activity in the brain (seizures) • caused by genetic default or trauma • triggers include lack of sleep, flashing lights, low blood sugar, alcohol • genetic mechanisms include defective ion channels that make neurons hyper-excitable, or an over-abundance of excitatory neurotransmitters

16. Nervous System Disorders Alzheimer's • deterioration of memory and mental capacity • related to decreased production of acetylcholine Parkinson's • characterized by involuntary muscle contractions and tremors • caused by inadequate production of dopamine

17. Nervous System Disorders Botulism • paralytic illness caused by poisoning from toxins produced by the bacterium Clostridium botulinum • blocks release of acetylcholine at synapses • death occurs due to respiratory failure