6.2.1 Nerves Flashcards
(12 cards)
What type of cells form the myelin sheath
Schwann
What is the structure between each myelin sheath
Node of Ranvier
Describe and explain how a resting potential is maintained in a neurone
- Higher [k+] in neurone than out, and higher [Na+] outside neurone than in
- So, k+ diffuse out neurone, and Na+ diffuses in
- Membrane more permeable to K+ leaving neurone, than Na+ entering neurone
- Sodium ions activly transported out of neurone, and potassium ions into neurone
Describe and explain how an action potential is created in a neurone
- Gated sodium ion channels open, so sodium ions diffuse in
- If threshold potential is reached, voltage-gated sodium ion channels open and more sodium ions diffuse in
- Section of axon membrane depolarised
- Voltage gated sodium ion channels close, and votage gated potassium channels open
- Efflux of potassium ions out of neurone causes repolarisation
Describe the all-or-nothing principle
- Action potential is only generated when threshold is reached
- High pressure generates an action potential
Describe and eplain the differences in myelinated vs non-meuyelinated neurones
- Myelination provides electrical insulation
- So depolarisation occurs at nodes of ranvier (saltatory conduction)
- Non-myelinated depolarisation occurs along whole length of neurone
What is the purpose of the refractory period
Ensure unidirectional propogation of action potentials
What is the refractory period
Time where no new generator potential can be produced
What factors increase the speed of conductance
- Myelination and saltatory conduction
- Increased axon diameter (less reistance to diffusion of ions)
- Increased temperature (increased rate of diffusion of ions)
How does increasing axon diameter increase speed of conductance
Less resistance to diffusion of ions
How does increasing temperature increase speed of conductance
Increased rate of diffusion of ions
What name is given to depolarisation at Nodes of Ranvier
Saltatory conduction
