Communication in the Human Body

Two Systems Nervous Endocrine Fast and short term communication Electrical (neurons) Chemical (neurotransmitters) Endocrine Slow and long term communication Chemical (hormones)

Your Senses Location Distance (mm) Observations Arm Finger Tip Back of Neck

What’s Happening Neuron’s (Cells that make up nerves) 3 parts: Dendrite (where input happens (receptors)) Cell Body (where organelles are located) Axon – message is sent down (axon terminal – output) Neurons are bundled together to make a nerve!

Types of Neurons Sensory Neuron – organ to central nervous system (CNS) Interneuron – make up CNS Motor Neuron – from CNS to organ

Neurons are Specific Individual Neurons respond to only 1 type of stimulus. Example Touch (3 types of neurons) Pressure Pain Temperature

How Neurons Work Neurons are polarized (negative inside and positive outside) When “fire” they temporarily depolarize This is propagated down the axon to the axon terminal All or none (action potential)– either enough stimulus (threshold) for nerve to completely “fire” or does not “fire” at all http://www.youtube.com/watch?v=YwN9aCobCy8

Neurotransmitters Communication between neurons at the synapse Small space between axon terminal of one neuron and the dendrites of another. Are specific – needs to be receptor for neurotransmitter on receiving dendrite Released triggered by electrical signal. Re-uptake: Neurotransmitters are reabsorbed and reused http://www.youtube.com/watch?v=90cj4NX87Yk&feature=endscreen&NR=1

2 categories of neurotransmitters Excite or cause action potential Inhibit or prevent action potential Many drugs mimic or act like neurotransmitters

Endocrine System Chemical messengers Specific – has to be a receptor for the hormone in order for the cell to respond to it. Control – normally a negative feedback loop Some drugs can also mimic hormones