Section 6 - 15 Nervous coordination and muscles Flashcards
Define - potential difference
The difference in electrical potential between two points
Define - Polarised
The term used to describe a cell that has a difference in electrical potential across its membrane
Define - diffusion
The movement of a substance from an area of high to low concentration
Define - facilitated diffusion
The movement of a substance from an area of high to low concentration using a protein carrier
Define - active transport
The movement of a substance from an area of low to high concentration, requires energy
Define - leakage channel proteins
Proteins involved in the active transport of substances across membranes
Define - Voltage-gated channel proteins
An ion channel found in plasma membranes, they open and close as the potential difference of membranes changes
Define - protein pumps
An ion channel found in plasma membranes, their permeability to ions remains relatively constant
Explain the structure of a myelinated motor neurone
- Voltage gated sodium and potassium channels only found on the node of Ranvier
- Action Potential only happens at the node of ranvier
- The action potential jumps from node to the next as the sheath is highly insulated
Explain the structure of a non-myelinated motor neurone
- Action potential fires as voltage gated sodium channels are open and the threshold is reached
- The action potential means more voltage gated sodium channels are opened
- Only one direction as refractory period so voltage gated sodium channels close
What is the nerves resting potential?
- potential difference = -65mv
- polarised
- inside is more negative
- more positively charged outside
- potassium ions inside
- sodium ions outside
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How do nerves maintain a resting potential?
- Aim to main the inside more negative
- At sodium-potassium pump - active transport 3 sodium out and 2 potassium in - going against the conc gradient
- Increased sodium conc outside - leakage channel proteins closed preventing facilitated diffusion
- Increased potassium conc inside - diffuse out the cell as leakage channel proteins are open
- Overall more positive ions outside the cell so positive outside and negative inside.
What are the stages of action potential being reached within the nervous system?
- stimulate
- depolarisation
- repolarisation
- hyperpolarisation
- restoration of resting potential
Explain the stimulate stage of creating an action potential
- causes voltage gated soidum channels to open and sodium ions to diffuse into neurons
- This makes the inside less negative - depolarisation
Explain the depolarisation stage of creating an action potential
- If enough voltage gated sodium channels are opened then enough sodium entered the cell to reach threshold
- threshold = -55mv
- This allows more SGSC to open and active potential occurs
- AP membrane = +40mv
Explain the repolarisation stage of creating an action potential
- VGSC closed and VGPC are opened
- Means potassium diffuses out of the cell causing the membrane to become more negative