Communicationin the Human Body

Two Systems

• Nervous – 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