Neurones Flashcards
Why can receptors be considered transducers?
They convert one type of energy into an electrical impulse
What is the charge of the inside and outside of a neurone?
Inside negative
Outside positive
What is the resting potential of a neurone?
-70mV
Draw a Pancinian Corpuscle
Sensory neurone with connecting tissue (lamellae)
Explain how pressure on a Pancian C, causes an action potential
- The shape of the corpuscle is changed
- Causing Stretch mediated sodium channels in the neurone membrane to open
- Sodium ions diffuse into the concentration gradient
- Depolarising the membrane
- Called a generator potential
- The greater the pressure the more stretch mediated channels open causing a bigger generator potential
- If threshold is reached an action potential develops and is transmitted along the neurone
When is a action potential triggered?
When the generator potential reaches the threshold
Explain adaptation in neurones?
When pressure is first applied impulses are transmitted along the neurone
With continuous pressure the frequency of the action potentials decreases, and then after a while may stop altogether
It prevents the nervous system from being overloaded with insignificant information
What piece of equipment could be used to measure potential difference
Voltmeter
Explain how testing potential is established and maintained
- There is a higher concentration of sodium ions on the outside than on the inside and a higher concentration of potassium ions on the inside than the outside of the axon
- The membrane is relatively impermeable to both K and Na but is less permeable to NA so more K diffuse out than Na in
- This means there are more positive ions outside the membrane and the membrane is said to be “polarised”
- The resting potential is maintained by the SODIUM POTASSIUM PUMP which pumps 3 Na out and pumps 2 K ions in
What happens when a neurone is stimulated? (Simple)
A nerve impulse starts when the resting potential across the neurone membrane is converted into an action potential
Draw a graph to correctly demonstrate how a membrane is stimulated
Include generater potential and restin and action, label with depolarisation and depolarisation and hyperpolarisation
Explain how a neurone is depolarised
- During an action potential, one section is depolarised
- This depolarisation of one section of membrane causes local currents
- These currents cause the voltage sensitive sodium ion channels to open, increasing the permeability if the membrane to sodium ions so causing depolarisation leading to the development of an action potential
- The nerve impulse can only travel in one direction due to the hyperpolarisaton of the membrane
Explain Saltatory conduction
In a myelinated nerve the depolarisation/ action potential jumps from node to node
The effect of the myelin sheath is to speed up conduction
Typical speed of conduction is 100ms-1
What are the two nervous systems
Explain what they are
Nerves carry impulses to and from the rest of the body (Peripheral Nervous system)
Central Nervous system consisting of the brain and the spinal cord
What do the Somatic Nervous system and the Autonomic Nervous System control?
Controls conscious actions like walking (somatic)
Controls unconscious actions like altering heart rate (autonomic)