Do Now: 3 Types of Nerve Cells Glue in your notebook on the next blank page!
Do Now: 3 Types of Nerve Cells
Levels of Organization
Whiteboard Activity Opinion Question What is an ELECTROLYTE? You have 3 minutes to talk to your lab group and then be ready to share out.
What is an ELECTROLYTE? DO NOT WRITE…DISCUSSION ONLY All salts are electrolytes! Substances that conduct an electrical current in a solution A salt is an organic compound found in the body in the form of minerals Calcium and phosphorus, found in teeth and bones Dissolved minerals found in urine Sodium and potassium ions used for nerve impulses in the brain Iron, found in hemoglobin, in the blood cells (this is what makes it red in color)
Notes: How Neurons Communicate Glue this picture on the next blank page
Why is this impulse called an ACTION POTENTIAL? Voltage = measures the difference in concentration of charges. The positives are the “hole” you leave behind when you move an electron. Original experiments on giant squid neurons!
Important Chemistry Vocabulary anions (negative) more concentrated IN THE CELL cations (positive) more concentrated in the extracellular fluid (OUTSIDE THE CELLS) channel leaks K+ K+ Na+ K+ Cl- aa- + – K+
Transmission of a Nerve Signal Neuron communicate similar to dominoes Once the 1st protein channel on the cell membrane opens…the rest open up in succession (one after the other) all or nothing response a “wave” travels along neuron Then…protein channels need to be re-set so neuron can react again
How does a nerve impulse travel? STEP 1 and 2 Step 1 - Stimulus: nerve is stimulated (ACTIVATED) Protein channels open on the cell membrane Step 2 - Na+ ions diffuse into cell charges reverse positive inside; negative outside The 1st domino goes down! – + Na+
How does a nerve impulse travel? STEP 3 STEP 3 - Wave: nerve impulse travels down neuron change in charge opens the protein channels “wave” moves down neuron = action potential Gate + – channel closed channel open The rest of the dominoes fall! – + Na+ wave
How does a nerve impulse travel? STEP 4 STEP 4 - Re-set: 2nd wave travels down neuron K+ protein channels open K+ ions diffuse out of cell charges reverse back negative inside; positive outside Set dominoes back up quickly! + – Na+ K+ wave Opening gates in succession = - same strength - same speed - same duration
Checking For Understanding 1. What are the 4 steps of nerve impulse travel? Write a paragraph or bullet points or draw a flow chart.
Myelin sheath Axon coated with Schwann cells insulates axon speeds signal signal hops from node to node 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 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++ Calcium is a very important ion throughout your body. It will come up again and again involved in many processes. neurotransmitter acetylcholine (ACh) receptor protein muscle cell (fiber) We switched… from an electrical signal to a chemical signal
Nerve impulse in next neuron K+ Post-synaptic neuron triggers nerve impulse in next nerve cell chemical signal opens ion-gated channels Na+ diffuses into cell K+ diffuses out of cell switch back to voltage-gated channel K+ Na+ ion channel binding site ACh Here we go again! – + Na+
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 Nerves communicate with one another and with muscle cells by using neurotransmitters. These are small molecules that are released from the nerve cell and rapidly diffuse to neighboring cells, stimulating a response once they arrive. Many different neurotransmitters are used for different jobs: glutamate excites nerves into action; GABA inhibits the passing of information; dopamine and serotonin are involved in the subtle messages of thought and cognition. The main job of the neurotransmitter acetylcholine is to carry the signal from nerve cells to muscle cells. When a motor nerve cell gets the proper signal from the nervous system, it releases acetylcholine into its synapses with muscle cells. There, acetylcholine opens receptors on the muscle cells, triggering the process of contraction. Of course, once the message is passed, the neurotransmitter must be destroyed, otherwise later signals would get mixed up in a jumble of obsolete neurotransmitter molecules. The cleanup of old acetylcholine is the job of the enzyme acetylcholinesterase.
Checking For Understanding 2. How does the transmission of an action potential from neuron to neuron represent a set of dominoes falling down? Write a paragraph or bullet points or draw a flow chart.
Human Action Potential Everyone in your group should have at least 1 poster. (everyone participates) Objective: Stand up and stand on the line (tape on the floor) to assemble 2 human neuron. The order of the posters should demonstrate the change in electrical charges and movement of ions (charged particles) down the neuron.
Exit Slip Work on your own. Open note. When you finish your paragraph… Peer grade - choose a lab group member to read your paragraph and provide feedback. Turn in your exit slip into the exit slip tray