Neuron firing like a Toilet 1. Like a Neuron, a toilet has an action potential. When you flush, an “impulse” is sent down the sewer pipe
Neuron firing like a Toilet 2. Like a neuron, a toilet has a refractory period. There is a short delay after flushing when the toilet cannot be flushed again because the tank is being refilled
Neuron firing like a Toilet 3. Like a Neuron, a toilet has a resting potential. The toilet is “charged” when there is water in the tank and it is capable of being flushed again 4. Like a Neuron, a toilet operates on the all-or-none principle – it always flushes with the same intensity, no matter how much force you apply to the handle
All-or-None Principle The principle that if a neuron fires it will always fire at the same intensity All action potentials are of the same strength. A neuron does NOT fire at 30%, 45% or 90% but at 100% each time it fires.
Communication Between Neurons Module 7: Neural and Hormonal Systems
Synapse ◦ The space between the terminal buttons on one neuron and dendrites of the next neuron
Neurotransmitters ◦ Chemicals contained in the terminal buttons that enable neurons to communicate. Neurotransmitters fit into receptor sites on the dendrites of neurons like a key fits into a lock.
Acetylcholine (Ach) Found in neuromuscular junctions Involved in muscle movements Involved in learning and memory Involved in REM sleep
Disruption of Acetylcholine Functioning Nerve gases and Black Widow spider venom — too much ACh leads to severe muscle spasms and possible death Cigarettes — nicotine works on ACh receptors ◦ can artificially stimulate skeletal muscles, leading to slight trembling movements
Acetylcholine - Alzheimer’s Disease Deterioration of memory, reasoning, and language skills Symptoms may be due to loss of ACh neurons
Dopamine Involved in movement, attention, and learning Reward and motivation – drugs can impair this greatly
Dopamine - problems Dopamine imbalance also involved in schizophrenia Loss of dopamine-producing neurons is cause of Parkinson’s disease
Parkinson’s Disease Results from loss of dopamine-producing neurons in the substantia nigra Symptoms include ◦ difficulty starting and stopping voluntary movements ◦ tremors at rest ◦ stooped posture ◦ rigidity ◦ poor balance
Serotonin Affects mood, hunger, sleep, and arousal Emotional states
Serotonin Problems Involved in depression ◦ Prozac works by keeping serotonin in the synapse longer, giving it more time to exert an effect
Endorphins Natural opiates that are released in response to pain and vigorous exercise Positive emotions
Norepinephrine Physical Arousal “Fight or flight” response Works with the sympathetic nervous system Learning memory
Neural Communication: The Neural Chain Module 7: Neural and Hormonal Systems
Receptor Cells Specialized cells in the sensory systems of the body that can turn other kinds of energy into action potentials that the nervous system can process Receptor cells in the eye turn light into a neural impulse the brain understands.
Sensory Nerves Nerves that carry information to the central nervous system Connect the sense organs to the brain and spinal cord
Interneuron's Nerve cells in the brain and spinal cord responsible for processing information related to sensory input and motor output
Motor Nerves Nerves that carry information from the central nervous system Carries messages from the brain and spinal cord to other parts of your body
Most information travels from the body, up the spinal cord, is processed by the brain, sent back down the spinal cord, and then back to the body with behavior instructions. The exception to this general pathway is reflexes.
Reflexes are controlled by the spinal cord without any conscious effort on behalf of the brain. Reflexes serve as primitive responses that protect our bodies from danger and help us adjust to our surroundings.
Reflex We cough, for example, when an irritant enters our windpipe and we need to expel it through our mouth. We sneeze when we need to clear our nasal air passages of irritants and allergens. We blink when danger threatens the sensitive tissues of the eye and when we need to moisten and clean the cornea. (This reflex occurs 900 times an hour!) We yawn when nerves in the brain stem find there's too much carbon dioxide in the blood.