neurons and synaptic transmissions Flashcards
(17 cards)
1
Q
how may neurons are there in the human nervous system
A
100 billion
2
Q
what percent of neurons are located in the brain
A
- 80%
3
Q
what are the 3 types of neurons
A
- sensory
- relay
- motor
4
Q
sensory neuron
A
- carry messages from the PNS to the CNS
- long dendrites
- short axons
5
Q
relay neuron
A
- connect the sensory neuron to motor or other relay neurons
- short dendrites
- short axons
6
Q
motor neuron
A
- connect the CNS to effectors (muscles and glands)
- short dendrites
- long axons
7
Q
what does the cell body include
A
nucleus which contains genetic material of the cell
8
Q
what are dendrites
A
- branchlike structures protruding form cell body
- carry nerve impulses from neurons to the cell body
9
Q
what are axons
A
- carry nerve impulses away form the cell body
10
Q
what are myelin sheath
A
- fatty layer that protects the axon
- speeds up the electrical transmission of the impulse
11
Q
nodes of ranvier
A
- gaps in the myelin sheath
- speed up rate of transmission by forcing the impulse to jump across the gaps
12
Q
what are terminal buttons
A
- a the end of axons
- communicate with the next neuron
13
Q
the firing of a neuron
A
- when a neuron is in resting state the inside of the cell is negatively charged compared to the outside
- when a neuron is activated by a stimulus the inside of the cell becomes positively charged for a split second causing the action potential to occur
- this creates an electrical impulse that travels down the axon towards the end of the neuron
14
Q
chemical transmission
A
- each neuron is separated from the next by the synapse
- signals within neurons are transmitted electrically
- signals between neurons are transmitted chemically across the synapse
- when the electrical impulse reaches the presynaptic terminal it triggers the release of neurotransmitters from synaptic vesicles
15
Q
neurotransmitters
A
- chemicals that diffuse across the synapse to the next neuron
- once it crosses the gap it is taken up by a postsynaptic receptor site on the dendrites off the next neuron
- only travels 1 way
- different neurotransmitters have different specialist functions
16
Q
excitation and inhibition
A
- neurotransmitters have either an excitatory or inhibitory effect on the neighboring neuron
- serotonin causes inhibition so the neuron is negatively changed and less likely to fire
- addrealinee causes excitation by increasing the neurons positive charge and making it more likely to fire
17
Q
summation
A
- decides whether a postsynaptic neuron fires
- if the net effect on the postsynaptic neuron is inhibitory the next neuron is less likely to fire
- if the net effect is excited it is more likely to fire
- action potential of the neuron is only triggered if the sum of the excitatory and inhibitory signals reaches the threshold
