Topic 6 - Nervous Coordination Flashcards
What is a myelinated nerve fiber?
Nerve fibers that are insulated by a myelin sheath
What colour is a myelinated nerve fiber?
White
What colour are unmyelinated nerve fibers?
Grey
Do myelinated nerve fibers contain nodes of ranvier?
Yes
Do unmyelinatednerve fibers contain nodes of ranvier?
No
What is the speed of transmission in myelinated nerve fibers?
High speed of transmission
What is the speed of transmission in unmyelinated nerve fibers?
Low speed of transmission
Where are myelinated nerve fibers located?
Central and peripheral nervous system
Where are unmyelinated nerve fibers located?
In the central and peripheral nervous system in the group C nerve fibers.
What is impulse conduction like in myelinated nerve fibers?
Do not lose the impulse during conduction.
What is impulse conduction like in myelinated nerve fibers?
Can lose the nerve impulse during conduction.
What is the length of myelinated axons?
Long
What is the length of unmyelinated axons?
Short
What is Saltatory conduction?
A rapid method by which nerve impulses move down a myelinated axon with excitation occurring at the nodes of ranvier
What happens when the node is at the refractory period?
Membrane becomes repolarised
Na+ channel proteins open
K+ channels open
What happens when the node is at the action potential?
Membrane fully depolarised
All Na+ channel proteins open
K+ channel proteins closed
What happens when the node is becoming depolarised?
Membrane Membrane potential moves towards the threshold level Na+ channel starting to open but many still closed
K+ channel proteins closed
What happens when the node is at resting potential?
Membrane potential around -B27- Na+ channel proteins closed
K+ channel proteins closed
What is the myelin?
Lipid substance produced by Schwann cells
What are Schwann cells?
Special cells that create myelin in the peripheral nervous system
What are the nodes of ranvier?
Gaps in myelin sheath with sodium channels
What is an action potential?
Electrical signal generated at the axon
What is depolarisation?
Process of sodium influx causing axon activation
What is saltatory conduction?
When the impulse ‘jumps’ from one node of Ranvier to the next, resulting in rapid conduction.
What happens to the node in saltatory conduction in the refractory period?
Membrane becoming depolarised
Na+ channel proteins close
K+ channels open
What happens to the node in saltatory conduction at the action potential?
Membrane fully depolarised
All Na+ channel proteins open
K+ channel proteins closed
What happens to the node in saltatory conduction during depolarisation?
Membrane potential moving towards the threshold level
Na+ channels starting to open but many still closed. K+ channel proteins close
What happens to the node in saltatory conduction at the resting potential?
- Membrane potential around -70mV
- Na+ channel proteins closed
- K+ channel proteins closed.
