Nervous System - Reflex Arcs Flashcards
Structure of a neurone
nerve cells
denrites (attached to dendron)
make connections with other neurones (or effectors)
nucleus
controls the cell
axon
carries the impulses along the neurone
node of ranvier
small parts of exposed axon that increases the speed of the electrical impulses - since the nodes are spaced out, they allow for salatory conduction where the signals (electrical impulses) rapidly jump from node to node.
myelin sheath
insulates the axon, increasing the speed of electrical impulses - The myelin sheath contains periodic breaks called nodes of Ranvier. By jumping from node to node, the impulse can travel much more quickly than if it had to travel along the entire length of the nerve fibre.
Nerve impulses are carried to the neighbouring nerve cell by…
neurotransmitters, which are chemical messengers released by the nerve cell and then taken up by the next.
nerve endings that include the synaptic end bulbs
Synapses = gaps between neurones which allow electrical impulses in the nervous system to cross between neurones.
The synaptic end bulbs contain sacs containing…
neurotransmitters.
The neurotransmitters move across the synapse to the neighbouring cell’s…
receptor site.
At the receptor site (at the dendrites)…
chemicals attach to the next neurone’s receptor site and set up a new electrical impulse.
Receptor’s for neurotransmitters can be blocked by…
anaesthetics or painkillers.
Painkillers work by…
depressing the central nervous system, making it more difficult for pain signals to reach the brain.
Second, they attach to opiate receptors to block pain signals coming from the body and preventing the neurotransmitters from moving along to the next nerve cell.
