Brain and nervous system Flashcards
Neuron
A specialized cell in the nervous system accumulates and transmits information
What are the different parts of the neuron?
dendrites -> cell body -> axon and the nodes of ranvier and myelin sheath
How many neurons are in the human body?
100 billion about
What is the size range of neuron cell bodies?
5 to 100 micron in diameter
What is the longest axon in the human?
those of motor neurons which transmit neural impulses from the brain to the muscles
Efferent nuerons
nerves that carry messages outward from the central nervovus systems
So the motor neurons carry efferent signals
afferent neurons
nerves that carry messages inward toward the CNS
What makes up 99% of the brain’s neurons?
projection neurons and interneurons
what are projection neurons?
they link one area of the CNS to ome other areas, usually with long axons
what are interneurons
make local connections from one neuron to another with usually short axons
What is the form of carb that feeds the neurons?
Lactate
What does the glial cells do?
1) holding neurons in place
2) provide nourishment to the neurons and controlling the supply
3) sensitive to activity levels and increase blood flow when necessary
4) help with development and migration of neurons
5) create myelin
What is the neuron’s resting potential?
-70 mV and this is the difference between the inside and the outside of a neuronal membrane when the neuron is not firing
What is the excitation threshold in mammals?
-55mV
How the neuron maintain this difference in potential?
different concentration of ions through things like the ion pumps that move more (3) sodium ions out of the cell than potassium ion into the cell. (3:2)
ion channels also help because the ion pumps keep a high concentration of K+ inside the cell, they will diffuse out of the channel
what happens when there is stimulation for action potential?
The sodium ion channels open and there is an influx of positive Na ions which depolarizes the membrane
What is the refractory period?
The time after an action potential during hich a neuron’s cell membrane is unprepared doe the next action potential
What the speed of propagation without myelin
1 meter per second
What is the speed of propagation with myelin sheaths?
120 meters per second
What is multiple sclerosis?
when the brain’s own muelinatoin breaks down because of auto immune response
How to tell the difference between weak or strong signals if there is the all or non law
rate of firing, the number of neurons being excited
What is the highest rate of firing in the human body
1000 impulses per second
what is the trade off of chemical transmission at the synapses
there is slower rate but there is added adcantage of having more neurons to communicate and integrate different pieces of information
can have both inhibitory and excitatory signals
Also can summate different weak signals to push over the threshold
What is Otto Loewi’s experiment
The frog heart showed that there mus be chemical trnsmission going on
Ach
usually at the muscles and can make muscle fibers contract
serotonin
sleep mood and arousal
GABA
most common inhibitory neurotrasmitter
Glutamate
the major excitatory neurotransmitter, important for learning and memory
Norepinephrine
arousal level, wakefulness, learning and memory
Dopamine
Influences movement, motivation and emotion
What does the lock and key model help with?
Selectivity of signals, exact shape of the neurotransmitter must match the receptor
What are agonist
drugs that enhance a neurotransmitter’s activity