Your Nervous System

Engage Lorenzo’s Oil Discussion Lorenzo’s Oil Discussion

Explore Quick Communications Quick Communications Neuron Models Neuron Models

Explain Nervous System Four Major Parts of the Nervous System Four Major Parts of the Nervous System Neurons Neurons Nerves Nerves Brain Brain Spinal Cord Spinal Cord

Two Major Nervous System Central Nervous System Central Nervous System Peripheral Nervous System Peripheral Nervous System Nerves and Neurons are found in both and this is where we will begin Nerves and Neurons are found in both and this is where we will begin

Neuron ”Nerve Cell” Neuron ”Nerve Cell” Functional Unit of Nervous System Functional Unit of Nervous System 1. Cell Body – center part of the cell containing the nucleus 2. Dendrites Carries messages toward the cell body. Carries messages toward the cell body. Fingerlike projections Fingerlike projections 3. Axon Carries messages away from the cell body. Carries messages away from the cell body. Elongated extension of the cell body Elongated extension of the cell body End of the axon is divided into fingerlike projections called axon terminals. End of the axon is divided into fingerlike projections called axon terminals.

Neuron Model To check for understanding you will need to construct a neuron model that contains dendrites, a cell body (soma), axon, and axon terminals. To check for understanding you will need to construct a neuron model that contains dendrites, a cell body (soma), axon, and axon terminals.

Types of Neurons Sensory Neurons – picks up the stimuli (nerve impulse) and carries it to the spinal cord and brain. Sensory Neurons – picks up the stimuli (nerve impulse) and carries it to the spinal cord and brain. Interneurons- Found within the brain and spinal cord. Relays the message between the sensory neurons and the motor neurons. Interneurons- Found within the brain and spinal cord. Relays the message between the sensory neurons and the motor neurons. Motor Neurons – transfers impulses away from the brain to the spinal cord Motor Neurons – transfers impulses away from the brain to the spinal cord

How Neurons Work 1. Reception Receptors in the skin sense stimuli Receptors in the skin sense stimuli 2. Transmission Sensory neurons transmit the touch message Sensory neurons transmit the touch message 3. Data Interpretation Information is sorted and interpreted Information is sorted and interpreted 4. Transmission Motor Neurons transmit a response message to a muscle Motor Neurons transmit a response message to a muscle 5. Response Muscles are activated causing a response Muscles are activated causing a response

Impulse Transmission Start with a RESTING neuron – one NOT transmitting an impulse Start with a RESTING neuron – one NOT transmitting an impulse Plasma membrane controls [ ] of ions inside the cell Plasma membrane controls [ ] of ions inside the cell Na + and K + on both sides of membrane Na + and K + on both sides of membrane Na + Higher Conc Outside Na + Higher Conc Outside K + Higher Conc Inside K + Higher Conc Inside Remember Na + /K + ATPase Pump Remember Na + /K + ATPase Pump

Sodium Potassium Pump

How an Impulse Travels Stimulus excites a neuron Stimulus excites a neuron Na+ channels open, Na+ build up inside Na+ channels open, Na+ build up inside Inside more + that outside Inside more + that outside Change in charge (depolarization) Change in charge (depolarization) Membrane immediately behind depolarization returns to RESTING STATE Membrane immediately behind depolarization returns to RESTING STATE RESTING STATE – inside negative, outside positive RESTING STATE – inside negative, outside positive

1. Resting State A neuron is not conducting an impulse A neuron is not conducting an impulse The K+ concentration is much higher inside the cell than out The K+ concentration is much higher inside the cell than out The Na+ concentration is much higher outside the cell than in The Na+ concentration is much higher outside the cell than in

2. Depolarization A nerve cell is stimulated A nerve cell is stimulated Membrane becomes permeable to Na+ for an instant and they quickly move into the cell Membrane becomes permeable to Na+ for an instant and they quickly move into the cell The inner surface of the cell membrane is now more positively charged then the outside. The inner surface of the cell membrane is now more positively charged then the outside.

3. Repolarization When the cell membrane becomes depolarized, K+ automatically leaves the cell until the cell is back to its resting state. When the cell membrane becomes depolarized, K+ automatically leaves the cell until the cell is back to its resting state.

4. The Impulse Travels “Wave” of depolarization – transmission of an impulse along length of axon “Wave” of depolarization – transmission of an impulse along length of axon All or None Principle – must reach a threshold level or the impulse dies All or None Principle – must reach a threshold level or the impulse dies Covered by a white covering called a myelin sheath (Schwann Cells), an insulator Covered by a white covering called a myelin sheath (Schwann Cells), an insulator Myelin sheath causes the ion exchange to occur only at the nodes which speeds up the process Myelin sheath causes the ion exchange to occur only at the nodes which speeds up the process For a short time after depolarization; the neuron cannot be stimulated For a short time after depolarization; the neuron cannot be stimulated

5. Transmission Across a Synapse Neurons do not actually touch. This gap between the two cells is call a SYNAPSE Neurons do not actually touch. This gap between the two cells is call a SYNAPSE Impulses are carried across a synapse by chemical messengers called neurotransmitters. Impulses are carried across a synapse by chemical messengers called neurotransmitters. Approximately 30 different neurotransmitters; do one of two things: Approximately 30 different neurotransmitters; do one of two things: 1. Stimulate the action potential in a second cell 2. Inhibit the action potential in the next cell

6. Refractory Period The period of time it takes a neuron to return to its resting potential after being stimulated The period of time it takes a neuron to return to its resting potential after being stimulated A neuron cannot be stimulated during this period A neuron cannot be stimulated during this period This period of time is about of a second This period of time is about of a second

Elaboration Neurotransmission: Neurotransmission: Nifty Neurons and Muscle Messages

Evaluation Parts of Nervous System List the Four Major Parts of the Nervous System List the Four Major Parts of the Nervous System Neurons Neurons Nerves Nerves Brain Brain Spinal Cord Spinal Cord