Why do animals need a nervous system?

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Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

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Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

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Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Synaptic Transmission

Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Nervous System Every time you move a muscle & every time you think a thought, your nerve cells are hard at work. They are processing information: receiving.

Presentation transcript:

Why do animals need a nervous system? What characteristics do animals need in a nervous system? fast accurate reset quickly Poor bunny! Remember… think about the bunny…

Nervous system cells Neuron a nerve cell Structure fits function signal direction dendrites cell body Structure fits function many entry points for signal one path out transmits signal axon signal direction synaptic terminal myelin sheath dendrite  cell body  axon synapse

Fun facts about neurons Most specialized cell in animals Longest cell blue whale neuron 10-30 meters giraffe axon 5 meters human neuron 1-2 meters Nervous system allows for 1 millisecond response time

Transmission of a signal Think dominoes! start the signal knock down line of dominoes by tipping 1st one  trigger the signal propagate the signal do dominoes move down the line?  no, just a wave through them! re-set the system before you can do it again, have to set up dominoes again  reset the axon

Transmission of a nerve signal Neurons have a similar system protein channels are set up once first one is opened, the rest open in succession all or nothing response a “wave” action travels along neuron have to re-set channels so neuron can react again

Let’s go to the video! http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

Myelin sheath Axon coated with Schwann cells insulates axon speeds signal signal hops from node to node saltatory conduction 150 m/sec vs. 5 m/sec (330 mph vs. 11 mph) signal direction myelin sheath

Multiple Sclerosis action potential saltatory conduction Na+ myelin + – axon + + + + – Na+ Multiple Sclerosis immune system (T cells) attack myelin sheath loss of signal

What happens at the end of the axon? Impulse has to jump the synapse! junction between neurons has to jump quickly from one cell to next How does the wave jump the gap? Synapse

Chemical synapse Events at synapse ion-gated channels open action potential depolarizes membrane opens Ca++ channels neurotransmitter vesicles fuse with membrane release neurotransmitter to synapse  diffusion neurotransmitter binds with protein receptor ion-gated channels open neurotransmitter degraded or reabsorbed axon terminal action potential synaptic vesicles synapse Ca++ neurotransmitter acetylcholine (ACh) receptor protein muscle cell (fiber) We switched… from an electrical signal to a chemical signal

Neurotransmitters Acetylcholine transmit signal to skeletal muscle Epinephrine (adrenaline) & norepinephrine fight-or-flight response Dopamine widespread in brain affects sleep, mood, attention & learning lack of dopamine in brain associated with Parkinson’s disease excessive dopamine linked to schizophrenia Serotonin

Neurotransmitters Weak point of nervous system any substance that affects neurotransmitters or mimics them affects nerve function gases: nitrous oxide, carbon monoxide mood altering drugs: stimulants amphetamines, caffeine, nicotine depressants quaaludes, barbiturates hallucinogenic drugs: LSD, peyote SSRIs: Prozac, Zoloft, Paxil poisons

Acetylcholinesterase Enzyme which breaks down acetylcholine neurotransmitter acetylcholinesterase inhibitors = neurotoxins snake venom, sarin, insecticides neurotoxin in green active site in red snake toxin blocking acetylcholinesterase active site acetylcholinesterase

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