Neurons, neural communication and synaptic transmission (1) Flashcards
What is neurogenesis?
The process where new neurons are formed in the brain.
What in our brains controls behaviour?
The sending of messages and connections between our cells.
What is a neuron?
They are specialised cells that receive and transmit information throughout the CNS.
What are the four parts of a neuron?
- Dendrites.
- Soma.
- Axon.
- Pre-synaptic terminal.
Describe the structure of the soma.
- The Soma contains the nucleus which houses the chromosomes and DNA.
- The bulk of the nucleus is made of cytoplasm which houses the mitochondria, endoplasmic reticulum, golgi apparatus and the plasma membrane.
- The mitochondria extracts energy from the breakdown of nutrients to provide energy in the form of ATP.
- The golgi apparatus produces lysosomes to break down unwanted substances.
- The plasma membrane separates the in and outside of the cell.
What is the function of the axon and what are three key terms associated with it?
- All information is sent along the axon.
- Action potential.
- Myelin sheath.
- Nodes of ranvier.
What is the myelin sheath?
The insulating material that covers the axon.
What are the nodes of ranvier?
Breaks in the myelin.
How do dendrites work?
- All information is received by dendrites.
- This information is received across a tiny gap called the synapse.
- Synapses line the surface of the dendrites.
- Outgrowths called dendritic spines increase the surface area available for communication.
What happens when an action potential reaches the pre-synaptic terminal?
They secrete a neurotransmitter which travels across the synapse to the next neuron in the chain.
What do the neurotransmitters do to the postsynaptic receptors?
Either excite or inhibit.
What is saltatory conduction?
How the action potential travels.
It passes down the axon, and jumps between the un-myelinated areas (Nodes of Ranvier).
What are two advantages of saltatory conduction?
- Energy is saved as sodium-potassium pumps are only required at specific points along the axon.
- Conduction of an action potential is much faster in myelinated axons.
What is resting potential?
- There are more sodium ions outside the cell and more potassium cells inside the cell, providing electrical energy.
- It is -70 volts.
What is an electrostatic gradient?
Positive ions being attracted to negative ions.
What is diffusion gradient?
When high concentrations of ions are attracted to areas of low concentration.
How does a neuron maintain its resting potential?
The unequal distribution of electrical charges and different concentrations of ions causes ions to repel and attract and move around.
Describe the sodium-potassium pump.
3 sodium ions are pumped out and 2 potassium ions pumped in using active transport, this helps maintain the negative charge within the neuron.
What is it called when the resting potential becomes more positive or negative?
More positive = excitatory postsynaptic potential (EPSP).
More negative = inhibitory postsynaptic potential (IPSP).
What are the four stages in EPSP?
0 Resting potential.
1 Depolarization.
2 Repolarisation.
3 Hyperpolarisation.
Describe depolarisation of EPSP.
When stimulated past threshold (-55mV), sodium channels open and sodium rushes into axon causing a region of positive charge.
Describe the repolarisation and hyper polarisation of EPSP.
Repolarisation =
Sodium channels close, potassium channels open and potassium exits the axon.
Hyperpolarisation =
Potassium continues to exit causing brief undershoot in charge. Ion pumps restore resting balance. Allows for “refractory period”
What is the difference between EPSP and IPSP?
EPSP sends the signal/neuron, while IPSP makes it harder to send.
What is the synpase?
A small space in-between neurons that they communicate through.
Describe components of a neurotransmitter.
- Chemical messengers.
- Synthesised by Golgi apparatus.
- Made from pre-cursor molecules.
What is a synaptic vesicle?
What neurotransmitters are stored in.
Describe the process of calcium channels.
- Depolarisation causes vesicles to dock on pre-synaptic membrane using protein clusters.
- Calcium channels open and calcium floods in.
- Some calcium ions attach to the dock causing the vesicle to fuse with the membrane.
- The vesicles releases the neurotransmitters into the synaptic cleft through the fusion pores. The process of release is called exocytosis.
What is a ligand?
A chemical that binds to a receptor. Has to be right key for the door.
What are three ways neurotransmitters can be removed from the synapse?
- Diffusion.
- Breakdown.
- Recycle and reuptake.
Describe the diffusion of neurotransmitters out of the cell.
Some neurotransmitters will simply drift away from the synaptic cleft by diffusion.
Describe the breakdown of neurotransmitters out of the cell.
After neurotransmitters have induced their effects, they are broken down by enzymes.
Describe the reuptake and recycle of neurotransmitters.
Some neurotransmitters can be absorbed back into the presynaptic neuron to be reused again.
What is the difference between an agonist and an antagonist?
- Agonists increase the action of neurotransmitters
- Antagonists block or decrease the action of neurotransmitters.
What are the main amino acids in the brain?
Glutamate and GABA.
Describe glutamate and GABA in relation to postsynaptic potentials.
- Glutamate is excitatory and produces EPSPs.
- GABA is inhibitory and produces IPSPs.
Describe the difference between inotropic and metabrotropic receptor effects.
- Ionotropic involves ligand gated channels.
- Metabrotropic involves metabrotrpic receptors and the activation of G-proteins.
What ions do glutamate and GABA work with?
Glutamate = Sodium.
GABA = Chlorine and Potassium.
What does alcohol do to glutamate and GABA?
It blocks glutamate receptors and enhances GABA functioning.
What categories of monoamines do dopamine, adrenaline and serotonin fit into?
Dopamine and adrenaline = catecholamines.
Serotonin = indolamines.
What is acetylcholine synthesised from?
Acetate and choline.
What is a neuropeptide?
Two or more amino acids linked together.
What is the function of nitric oxide?
To increase blood flow to the neurons.
