5.3 neuronal communication Flashcards
What is negative resting potential?
When there is a difference in electrical charges in a resting neuron, this means that it is more positive on the outside and negative on the inside.
How is negative resting potential created?
3 sodium are pumped to the outside of the nerve cell whilst two potassium are pumped into the inside via a sodium potassium pump. This creates an electrochemical gradient as it is more positive on the outside and negative on the inside. The potassium then diffuses out due to concentration gradient through the channel protein, which is only permeable to potassium. This makes the outside of the membrane more positive so the electrochemical gradient is steeper.
What are the four types of sensory receptor
- Mechanoreceptor - chemoreceptor
- thermoreceptor
- photoreceptor.
What stimulus does a mechanoreceptor respond to?
Pressure or movement.
What stimulus does a chemoreceptor respond to?
Chemicals.
What stimulus does a thermoreceptor respond to?
Heat.
What stimulus does a photoreceptor respond to?
Light.
How is action potential reached?
Stimulus causes the movement of sodium ions into the axon. If the threshold potential of -55 mV is reached the voltage gated sodium channels open, causing sodium ions to flood into the neuron. This causes the voltage to reach
+30mV. At +30mV the voltage gated sodium channels close and the voltage gated potassium channels open. This causes the potassium ions to flood out So -80mV is reached inside.
What is depolarisation
The flooding of sodium ions into the axon to reach action potential.
What is repolarisation?
The movement of potassium ions out of the axon.
What is the refractory period
The time between action potential and reaching resting potential
What is hyperpolarization?
Where too many potassium ions move out of the axon so it reaches -80mV. The sodium potassium pump brings the axon back to resting potential.
What is threshold potential
-55mV
It is the potential required for depolarisation took her.
How does the nerve impulse travel along the axon?
The sodium ions diffuse along the axon, which causes a local current.
Why is there refractory. important?
It ensures a delay between action potentials and ensures that the impulses can only pass in one direction along the axon.
What is for all or nothing principle?
The idea that there is no action potential if threshold potential is not reached.
When action potential is reached a more. intense stimulus would result in more frequent action potentials.
What is the Pacinian corpuscle an example of?
mechanoreceptor.
How does the pacinian corpuscle trigger a nerve impulse?
When pressure is applied, the layers are distorted, causing the stretch mediated sodium channels to open. This causes for sodium ions to enter the axon, creating action potential. Then the generator potential is where an influx of ions changes the potential of the axon, causing depolarization. This means action potential is established and a nerve impulse moods along the axon
What are the features of sensory receptor?
They are specific to a single type of stimulant and act as a transducer.
Why are sensory receptors transducers
They convert he stimulus into a nerve impulse.
What are the three types of neuron
- motor
- sensory
- relay
What are the features of a motor neuron?
- cell body in the CNS
- short dendrons
- long axon
What are the features of sensory neuron?
- cell body
- long dendrons
- short axon
What were the features of a relay neurone?
- cell body
- short dendron
- short axon
What does the relay neuron do?
It connects the sensory and motor neurons.
What is the difference between a dendron and an axon?
A dendron will transmit electrical impulses towards the cell body, whereas an axon will transmit electrical impulses away from the cell body.
What is the myelin sheath made up of?
Schwann cells which wrap around the axon tightly, preventing ions from passing through.
What is the benefit of having myelin sheath around a neuron?
It speeds up the transmission of the nerve impulse from 2 m/s to 200 m/s
How does a myelinated neuron speed up the transmission of a nerve impulse?
The myelin prevents sodium ions passing into the axon from the voltage gated sodium channels surrounded by myeling which creates a longer local current. Instead, the sodium ions move into the axon from the nodes of ranvier.
What is local current
The diffusion of sodium ions along the axon.
Why are synapses important?
- Insures impulses are unidirectional.
- Allows imposed me from 1 neurone to many
- Multiple stimuli can cause a single response.
What is spatial summation?
When multiple action potentials converge on one neuron, which builds up enough sodium ions for an action potential to be created.
What is temporal summation.
When multiple action potentials from the same presynaptic neuron meet. this builds up enough sodium ions for an action potential to be created.
What is an example of a neurotransmitter?
Acetylcholine
What are the two types of neurotransmitter?
- excitatory
- inhibitory
What happens in an excitatory ion channel synapse?
EPSPs are triggered the neurotransmitter will attach to the sodium channel. This means sodium move in so it is more positive inside
What is an EPSP?
An excitatory post synaptic potential.
What is an IPSP?
An inhibitory synaptic potential.
What happens in inhibitory ion channel synapse?
IPSPs are triggered. the inside is made more negative as potassium leaves and chlorine move in.
Outline what happens synapse?
- Action potential reaches the pre synaptic bulb
- Voltage gated calcium channels open so calcium ions enter.
- Vesicles containing acetylcholine fused for synaptic membrane.
- Acetylcholine diffuses across the. synapse and binds to the receptor in the sodium channels.
- Sodium channels open. So sodium moves into the post synaptic neuron, which triggers an action potential.
- Acetylcholine is inactivated by acetylcholine esterase into acetate and choline.
- choline is reabsorbed and acetylcholine is resynthesized and stored in vesicles.
