Biopsychology - Neurons and Synaptic Transmission Flashcards
What is a neuron?
Neurons and Synaptic transmission
Neurons are nerve cells and they are the basic building blocks of the nervous system. They process and transmit electrical and chemical signals.
Give information about neurons in the body
Neurons and Synaptic transmission
- There are 100 billion neurons in the human nervous system
- They communicate with eachother via electrical impulses and chemical signals
- They vary in size from less than a millimeter up to a meter long, they all share the same structure
- 80% of nerve cells are in our brain
Describe the function of the cell body
Neurons and Synaptic transmission
It contains the nucleus which contains the genetic material of the cell (DNA)
Descibe the function of dendrites
Neurons and Synaptic transmission
Dendrites branch out from the cell body and recieve signals from nearby nerve cells. They carry nerve impulses from neighbouring neurons towards the cell body.
Descibe the function of an axon
Neurons and Synaptic transmission
It is the thin body of the neuron and carries impulses away from the cell body down the length of the neuron
Describe the function of the myelin sheath
Neurons and Synaptic transmission
It is a fatty substance that is found around the axon which insulates to protect the axon. It speeds up electrical transmission of the impulse.
Describe the function of the nodes of ranvier
Neurons and Synaptic transmission
They are segmented gaps in the myelin sheath. They speed up transmission of the impulse by forcing it to jump across gaps along the axon.
Describe the function of terminal buttons
Neurons and Synaptic transmission
They are located at the end of the axon and communicate with the next nerve cell across the synapse.
The process of synaptic transmission (1)
Explain electrical transmission
(the firing of a neuron)
Neurons and Synaptic transmission
- In a resting state inside the cell, a neuron is negatively charged compared to outside of the cell
- When a neuron is activated y a stimulus, the inside of the cell becomes positively charged for a second, causing action potential to occur.
- This creates an electrical impulse that travels down the axon toards the end of the neuron
- The electrical impulse allows neurons to release chemical messangers called neurotransmitters that allow neurons to communicate with eachother
What are neurotransmitters?
Neurons and Synaptic transmission
They are chemicals that diffuse across the synapse to the next neuron in the chain. Once the gap is crossed, it’s absorbed by the post synaptic receptor site. The chemical message is then transformed back into an electrical signal in the recieving neuron. Each neurotransmitter has it’s own specific molecular structure that fits perfectly into a post synaptic receptor site, like lock and key.
The process of synaptic transmission (2)
Explain chemical transmission
Neurons and Synaptic transmission
Signals between neurons are transmitted chemically across the synapse.
1. The electrical impulse reaches the end of the neuron (presynaptic terminal)
2. It triggers the release of a neurotransmitter from tiny sacs at the terminal buttons called synaptic vesicles into the synapse.
NTs have either an excitatory or inhibitory effect on neurons next to it
Explain excitation and inhibition
Neurons and Synaptic transmission
- Serotonin (an NT) causes inhabition in the recieving neuron, resuting in the neuron becoming negatively charged and less likely to fire.
- Adrenaline (an NT and hormone) causes excitation in recieving neuron, resulting in neuron becoming more positively charged and more likely to fire.
- Neurons recieve both potentials at the same time and the likelihood of a cell firing is determined by adding up the excitatory and inhabitory synaptic input: Summation determines whether the cell fires.
The effects of psychoactive drugs
Neurons and Synaptic transmission
- Mental illnesses can be treated by these drugs
- Drugs produce their effects on behaviour by altering the levels of NTs in the brain - clinical depression has been linked to a lack of serotonin in the brain, therefore antidepresents increase levles of serotonin in the brain by lenghtening it’s effects at the synapse.
The effects of psychoactive drugs
Explain Antagonists and Agonists
Neurons and Synaptic transmission
- Antagonists: drug that stops a neuron from firing by blocking action of NT - inhabitory
- Agonist: drug that copies the action of a NT and binds to a receptor site, causing a neuron to fire - excitatory
Explain the sensory neuron
- Function: Carries messages from the PNS (sensory receptors) to the brain and spinal cord
- Structure: Long dendrites and short axons
- Location: PNS
Explain the relay neuron
- Function: Transfers messages from sensory neurons to other interconnecting neurons or moto neurons
- Structure: Short dendrites and short axons
- Location: Mostly in the brain and spinal cord
Explain the motor neuron
- Function: Carries messages from CNS to effectors such as muscles and glands
- Structure: Short dendrites and long axons
- Location: Their cell bodies are in the CNS and their long axons form part of the PNS
