Neurons and synaptic transmission Flashcards
Name the components of a neuron
Dendrites
Soma (cell body)
Nucleus
Myelin sheath
Node of ranvier
Axon
Terminal button
What are the cells making up the nervous system called? What are they specialised to do?
Neurons - specialised to conduct electrical impulses
What is the role of a sensory neuron?
To take messages into the nervous system from the environment
What are the components of a sensory neuron?
Receptor cell
Axon
Myelin sheath
Cell body
What is the role of a relay/inter neuron?
Within the CNS - allows sensory and motor neurons to communicate
What are the components of a relay/inter neuron?
Dendrite
Soma
Axon
Pre synaptic terminal
What is the role of a motor neuron?
Takes messages out of the CNS to an effector
What are the components of a motor neuron?
Dendrite
Soma
Axon
Myelin sheath
Node of ranvier
What are neurons covered in? What does the biochemical structure of this allow it to do?
Complex cell membranes made up of several layers
Allows it to conduct or transmit pulses of electrical activity
What are pulses of electrical activity called?
Action potentials
Where do action potentials begin and where do they travel?
Begin on the dendrites and travel across the cell body and along the axon
What is similar and different about action potentials?
Similar: all have the same electrical properties and look identical
Differences: frequency and pattern
What is the maximum rate at which action potential can be conducted along the neuron? What causes this?
Around 250-400 impulses per second, because of the molecular make up of the neuronal cell membrane
Who is the myelin sheath found and not found in?
Found in advanced animals such as humans and other mammals
Not found in more primitive animals
What is the myelin sheath?
A fatty cover along the axon
What are the nodes of ranvier?
Gaps in myelin sheath
What can action potentials do? (Nodes of ranvier)
They can jump from gap to gap, known as saltatory conduction
Is saltatory conduction faster or slower than the standard continuous conduction along the neuronal axon?
Faster
What is the synapse?
A gap between the presynaptic neuron and the post synaptic neuron
What is the first step of synaptic transmission?
Action potential pushes vesicles containing NTs to the presynaptic membranes
What is the second step of synaptic transmission?
NTs enter synaptic cleft (exocytosis)
What is the third step of synaptic transmission?
NTs diffuse across the synapse
What is the fourth step of synaptic transmission?
NTs bind to specific receptors
What is the fifth step of synaptic transmission?
Action potential created
What is the sixth step of synaptic transmission?
Receptors release NTs back into synaptic gap
What is the seventh step of synaptic transmission?
Released and unused NTs are then either reuptaken by the presynaptic membrane or digested by enzymes in the synapse
What is reuptake?
When the NT is taken up again by the presynaptic neuron where it is stored and made available again at a later time
What are the two ways neurotransmitters can be described in their actions?
Inhibitory or excitatory
What do excitatory NTs do?
Increase the likelihood that an excitatory signal is sent to the post synaptic cell which is then more likely to fire
What do inhibitory NTs do?
Decrease the likelihood of the neuron firing
An excitatory NT binding with a postsynaptic receptor causes an electrical charge in the membrane of the cell, resulting in an..
Excitatory postsynaptic potential (EPSP), meaning the cell is more likely to fire
An inhibitory NT binding with a postsynaptic receptor causes an electrical charge in the membrane of the cell, resulting in an…
Inhibitory postsynaptic potential (IPSP), meaning the postsynaptic cell is less likely to fire
Can a nerve cell receive both IPSPs and EPSPs at the same time?
Yes
How do you determine the likelihood of the cell firing?
Adding up the excitatory and inhibitory synaptic input
What does the net summation determine?
Whether the cell fires or not
What are the two ways the strength of EPSPs can be increased?
Spatial summation
Temporal summation
What is spatial summation?
A large number of EPSPs are generated at many different synapses on the same postsynaptic neuron at the same time
What is temporal summation?
A large number of EPSPs are generated at the same synapse by a series of high frequency action potentials on the presynaptic neuron
