Structure and Function of Sensory, relay and motor neurons, Process of Synaptic transmission Flashcards
What is the structure of a Neuron?
- Cell Body
- Dendrites
- Axon
- Myelin Sheath
What is the function of the cell body?
- Contains the nucleus (chromosomes)
What is the function of the dendrites?
- Extend from the cell body
- They carry electrical impulses from other neurons towards the cell body
What is the function of the Axon?
- An extension of the neuron
- It carries the impulses away from the cell
- It is covered by the Myelin Sheath
What is the function of the Myelin Sheath?
- A fatty substance which increases the speed at which impulses propagate
What are Sensory Neurons?
- Neurons which carry nerve impulses from the sensory receptors (e.g. vision, taste, touch) to the Central Nervous System
- They have long dendrites and short axons
What are Relay Neurons?
- Neither sensory nor motor but sit somewhere in between - allowing the two other types to communicate
- Carries information through the spinal cord/brain (from sensory neurons –> motor)
What are Motor Neurons ?
- Responsible for directly or indirectly controlling muscles
- Carries impulses from the Central Nervous System to effectors (e.g. muscles or glands)
- They have short dendrites and long axons
What are neurotransmitters?
- The molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles
-They allow the transfer of signaling messages between brain cells
Where are neurotransmitters located and stored?
- They are located in a part of the neuron called the axon terminal
- They are stored within thin-walled sacs called synaptic vesicles
Where does communication between two neurons happen?
- In the synaptic cleft
What are 2 examples of neurotransmitters?
- Dopamine
- Seretonin
What does too high dopamine cause?
Schizophrenia
What does too low serotonin cause?
Depression
What is Synaptic transmission?
The process by which a nerve impulse passes across the synaptic gap from a pre- synaptic neuron to a post-synaptic neuron.
Explain the 7 stage process of Synaptic Transmission
- Information is passed down the axon of the neuron as an electrical impulse known as action potential. Once it reaches the end of the axon it needs to be transferred to another neuron or tissue
- It must cross over the synaptic gap between the pre-synaptic neuron and post-synaptic neuron
- At the end of the neuron (in the axon terminal) are the synaptic vesicles, which contain chemical messengers, known as neurotransmitters
- When the electrical impulse (action potential) reaches these synaptic vesicles, it triggers (by opening up the calcium channels) the vesicles to move towards the membrane and release neurotransmitters into the synaptic cleft (called exocytosis)
- Neurotransmitters then carry the signal across the synaptic cleft. They bind to receptor sites on the post-synaptic cell, thereby completing the process of synaptic transmission
- The neurotransmitters makes it either more likely or less likely that the post-synaptic neuron will fire
- Neurotransmitters that don’t bind are either absorbed/broken down by enzymes or get re-uptaken back into the pre synaptic neuron
What is summation?
Add up of both excitatory and inhibitory inputs determines whether the cell fires
Explain the term excitation
- Neurotransmitter which increases the likelihood that an excitatory signal is sent to the post-synaptic cell, making it more likely that the neuron will ‘fire’
Explain the term inhibition
- A neuron which decreases the likelihood of a neuron ‘firing’
Give an example of Excitatory neurotransmitters taking action
Noradrenaline, act as the nervous system ‘on switches’ and they make it more likely that a post-synaptic neuron will ‘fire’, and a behavior will occur
Give an example of Inhibitory neurotransmitters taking action
GABA, are the nervous system’s ‘off switches’ in that they decrease the likelihood that a post-synaptic neuron will ‘fire’, and make it less likely that a behavior will occur