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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!

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did you know
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!
neurotransmitters synapses

Neurotransmitters & Synapses

ARE YOU READY TO RUMBLEEEEEE!?

please mr byrnes i m dying to know just what is a synapse
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
slide4

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
synapses
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
synapses1
Synapses

Some neurons and their transmissions are excitatory & some are inhibitory.

Excitatory: make the postsynaptic membrane more permeable to sodium & create “normal” action potential

synapses2
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

slide8

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

neurotransmitters
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

neurotransmitters1
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

drugs effects
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
drug effects
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
drug effects1
Drug Effects

Stimulants & Depressants: change the rate of transmission of neurotransmitter across the synapse

  • caffeine & diazepam are stimulants
  • aspirin & strychnine are depressants
nervous system disorders
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
nervous system disorders1
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
nervous system disorders2
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