Presentation on theme: "The Neuron An everyday (every second!) use of active transport"— Presentation transcript:
1 The Neuron An everyday (every second!) use of active transport OPENER Do the wave!
2 The Nervous SystemControls and coordinates functions throughout the body and responds to internal and external stimuli.
3 What makes up the Nervous System? The basic unit of structure and function of the nervous system is a neuron (nerve cell).
4 Structure of a Neuron4. Myelin sheath: insulating membrane *increases speed of impulse*1. Cell body: Contains the nucleus and other cell organellesAxon terminals4. Myelin sheathNodes1. Cell body3. AxonNucleus2. Dendrites3. Axon: long, thin extension of the cell body*Function: sends nerve impulses away from the cell body*(Remember “A” for away!)2. Dendrites: Short, branched extensions of the cell body*Function: receive stimuli*
5 3 Main Types of Neurons 1. Sensory Neurons (sensory = of the senses) -send impulse from sense organs to spinal cord & brain2. Interneurons (inter- = between)-relay messages between sensory and motor neurons3. Motor Neurons (motor = causing motion)-send impulse from brain and spinal cord to effectors(glands or muscles)
6 Which are sensory? Which are motor neurons? Top arrows = sensory; bottom arrows = motor
7 How do Neurons Communicate? 1. Dendrites receive the signal (action potential) which then travels down to the axon of the first neuron.2. When the signal reaches the end of the axon, the axon releases chemicals called neurotransmitters.ex. acetylcholine, norepinephrine, dopamine, serotonin3. Neurotransmitters enter into the space between the 2 neurons, called the synaptic cleft.4. Neurotransmitters bind to receptors on dendrites of the next neuron thereby passing on the signal.
8 The NeuronThe internal “solution” of the cell has a characteristic concentration of sodium versus potassium ionscalled: RESTING POTENTIALMore Na+ outside, more K+ insideTakes Energy to maintain thisA signal is produced when this internal “solution” changesCalled: ACTION POTENTIAL
10 The Resting Neuron When a neuron is at rest There is a certain amount of ions inside & outside of cellThis difference in charges is called the resting potential (-70mV)The nerve cell membrane pumps sodium (Na+) out of the cell and potassium (K+) into the cellWorks by active transportNet result = more K+ inside the cell and more Na+ outside the cellThe cell membrane leaks K+ back out of the cellDiffusionCausing the negative charge inside the cellAlso, organelles inside contribute to the negative charge
11 The Moving ImpulseAn impulse begins when a neuron is stimulated by another neuron or by the environmentCauses movement of ions across the membraneNa + rushes inWhat kind of transport is this?This is called an action potentialAlso called “depolarization (+30mV)Impulse travels down axon away from the cell body to the axon terminalat 110 m/sec (225 mph)After impulse passes, K+ flows out of the cell“repolarization” (-70mV)Passive transport (high to low)
12 What is an action potential? A sudden reversal of membrane potential.“Resting” is when the pump is active“Action” is when the sodium is diffusing into axon
13 Threshold Strength of impulse is always the same It is an all or nothing responseMinimum level of stimulation to cause an impulse is call the thresholdWhat happens when the action potential reaches the end of the axon?
14 The Synapse The area where an impulse is transferred between 2 neurons Synaptic cleft separates the axon terminal from the dendrites of the adjacent neuron
15 The SynapseThe terminals contain tiny sacs (vesicles) that contain neurotransmitters chemical signalsImpulse triggers release of neurotransmitters into the synaptic cleft (via exocytosis)Neurotransmitters diffuse across gap & bind to receptors on the adjacent neuronCause the impulse to continue(if threshold is reached)Neurotransmitters are either broken down or recycledThis is where drugs interfere
16 Dendrite of adjacent neuron The Synapse = junction between two neuronsSection 35-2Direction of ImpulseDendrite of adjacent neuronAxonReceptorVesicleAxon terminalSynaptic cleftNeurotransmitter