3.6.2 - Nervous Coordination Flashcards
What order is info conducted in, in the nervous system ?
Stimulus
Receptor
Coordinator
Effector - Response
What is a stimulus ?
An energy change in the environment
What is a receptor ?
A cell that detects change i.e - Pacinian corpuscle
What is a coordinator ?
This is something that receives nerve impulses from the receptor and makes a decision.
What is an effector ?
Muscle or gland which produces a response : either a chemical release or a muscle contraction.
What is more likely to happen to organisms that respond appropriately to stimuli ?
They maintain themselves in a favourable environment and are more likely to survive and pass on their genetics to the next generation.
What is an action potential ?
When neutron voltage increases beyond resting potential (-70mv)
This generates a nervous impulse
What is depolarisation ?
An increase in voltage above the resting potential, voltage gets more positive due to membrane getting more per able to Na+
What is Resting potential , how is it maintained ?
- 70 mv
- maintained by Na/K pump and K+ channels which are leakier
What is the movement of the ions at resting potential ?
Na+ /K+ ATPase transport protein channel allows 2k+ and 3Na+ ions out.
Via fac. Diffusion, this makes the inside relatively negatively charged.
Creates a con gradient, Na+ ions flow IN through leak channels, K+ channels also open , allowing +ive charge out - decreasing it again
What happens when there is a stimulus ?
This provides enough energy, allows the voltage gated Na+ channels to open
What happens during depolarisation ?
Voltage gated Na+ channels to open, allows ions to diffuse into axon same time as k+ diffusing out
What is the threshold ?
-55 mv
What will voltage always peak at ?
Why ?
+ 40 mv
- voltage gated Na+ channels will close when 40mv is reached in axon
- peak = reached, there will be no further increase.
What is repolarisation ?
K+ channels are open, they are diffusing out, causing a decrease in voltage.
Voltage gated Na+ channel closes
Cell becomes relatively negatively charged in comp. to what it was b4
What is hyperpolarisation ?
There is an overshoot beyond the resting potential, this is because the k+ leaky channels remain open, allowing positive charge to flow out.
What’s the all or nothing principle ?
(Nothing)
-55 mv is the threshold
If stimulus isn’t large enough, it won’t provide enough energy to open enough Na+ channels to go above -55
What’s the all or nothing principle ?
(All)
If -55 is reached, there will always be an action potential , all of them will peak at the same level (+40)
What does a bigger stimuli cause ?
- Higher frequency of action potentials, they fire more quickly along the axon.
Why is the all or nothing principle important ?
It ensures animals respond to large enough stimuli, not sky very slight change as it would be overwhelming.
- hinder survival
What is the refractory period ?
- Brief period of time after an AP in which neutron is less responsive e to stimulus
- Voltage gated Na+ channels = closed
- Na+ don’t move , meaning new AP can’t occur
What does the refractory period allow for ?
Discrete action potentials
Why is the refractory period important ?
- Ensures discrete impulses - each is separate from another
- Ensures APs travel in one direction - stops AP spreading which could prevent a response
3.limits number of impulse transmission - prevents overreaction : no overwhelming of senses
What is a nerve impulse ?
A wave of depolarisation
What 3 factors affect the speed of nervous impulses ?
1) Temperature
2) Axon diameter
3) Myelination and saltatory conduction
What is saltatory conduction ?
- How info travels down the axon, it jumps from node to node, triggering an AP in the next node of ranvier
- Faster and more efficient, also uses less ATP as less membrane is used
