Nervous System Flashcards
Describe the responsibility of the Nervous System
responsible for sensing and responding to the environment
Describe Receptor Cells
where the nervous system gets its information
they can be activated by internal stimuli (inside body) or external stimuli (outside body)
Describe how the nervous system processes and responds to stimuli
The nervous system processes and responds to stimuli by transmitting information to Mechanical Effectors (such as muscles) and Chemical Effectors (such as glands)
Describe Neurons
Neurons are the primary cells of the nervous system and are the biological basis for sensory and response
Describe Sensory/Afferent Neurons
they carry messages from the rest of the body to the brain, allowing us to sense our environment
Describe Motor/Efferent Neurons
they carry messages from the brain to the rest of the body, allowing us to respond to our environment
Describe Dendrites
they are the ends of the neurons which receive chemical messages
they receive excitatory or inhibitory signals from the environment and surrounding neurons
Describe Axons
they are the ends of the neurons which sends messages to other cells
Neurons tend to have a single axon with multiple dendrites
Describe Glial Cells
the other types of cells in the nervous system
they are not involved in message transmission, they exist to support the neurons
they pass nutrients from the capillaries to neurons, trap bacteria and other particles and produce myelin
Describe Myelin
the Myelin Sheath is a layer of fatty tissue that surrounds the axon
Myelin insulates the electrochemical signals making the nervous system more efficient
Without myelin, messages would get lost and you would lose the ability to sense and respond to your environment
Describe Excitatory Signals
signals that encourage the dendrites to send a message
Describe Inhibitory Signals
signals that encourage the dendrite to not send a message
if the amount of excitatory signals exceed the amount of inhibitory signals, then a message is sent along the neuron
the electrochemical message moves from dendrite to cell body to axon
Describe a Synapse
the dendrite of one neuron doesn’t physically attach to the axon of another neuron, resulting in a very short gap
Describe Neurotransmitters
Special chemicals that act as excitatory or inhibitory signals in the nervous system
When an electrochemical message reaches the ends of an axon, it causes the release of neurotransmitters into the synapse
once released, the neurotransmitters jump across the synapse and bind to the Receptor Site on the opposing dendrite
Describe what happens after neurotransmitters attach to the receptor site
the neurotransmitters will act to either send or inhibit a message in the receiving neuron, depending on whether the neurotransmitter is excitatory or inhibitory
the concentration of neurotransmitter molecules received must pass a threshold level in order to have effect
Describe Electrochemical
Nerve Impulses are Electrochemical, meaning that the electrical signal is the result of chemical differences across the neuron’s cell membrane
Describe a resting neuron
a resting neuron has more positive charges out of the cell membrane than in the cytoplasm
this causes a negative voltage across the membrane
(-70mV on average)
the negative voltage results from a much higher Na + K outside of the neuron than inside
Describe Sodium Ions
The majority of these positive charges outside of the neuron are Sodium Ions, which accumulate at a higher concentration in extra cellular fluid
Describe Potassium Ions
Potassium Ions also contribute to the resulting voltage, however these positive charges are usually in higher concentration within the cytoplasm
Describe a neuron’s resting state
Polarized
positive outside, negative inside
Describe the Sodium Ion Channels
Activation of the neuron results in the opening of Sodium Ion Channels in the cell membrane allowing positively charged sodium to flood into the neuron
Describe Depolarization
the movement of sodium ions causes the voltage to temporarily turn positive inside the neuron
(+ 40mV on average)
neurons can’t remain permanently depolarized or it will not be able to function
Describe the Sodium-Potassium Na-K Pump
it uses active transport to swap intracellular sodium ions with extra cellular potassium ions, resulting in RePolarization of the neuron
the reversal of charge triggers an Action Potential which moves down the neuron
Action Potential is the rapid change of charge
Describe the Refractory Period
When Repolarization takes place, it takes about 1ms to complete
that 1 ms is called the Refractory Period, where no new action potential can be initiated
