Neurons and Synaptic Transmission Flashcards
What is a neuron?
a cell that carries electrical impulses throughout the body
What are dendrites? (3)
-Extensions at the beginning of a neuron that increase the surface area of the cell body
-receive info from other neurons and transmit electrical stimulation to the cell body
-covered with receptors
What does the cell body (soma) do? (2)
-Produces proteins for the dendrites, axons and synaptic terminals
-Provides energy to trigger an action potential
What is the axon?
-The main conducting unit of the neuron, capable of conveying electrical signals along distances that range from as short as 0.1 millimetre (in the brain) to as long as 1 metre (from the spinal cord to big toe).
What do many axons do?
split into several branches, thereby conveying information to different targets
What are many axons wrapped in?
protective myelin sheath (fatty tissue that speeds up transmission) which are broken at various points by the nodes of Ranvier.
What is the axons job?
Transmits impulses to glands/muscles
Where is the axon terminal located?
on one end of a neuron.
What is the axon terminal? (2)
-the final part of a neuron to receive an electrical impulse
-is also the area where the impulse is converted to a chemical signal.
What does the axon terminal do?
transfers information from its neuron into another neuron, though it does not come into physical contact with the other neuron.
What are the features of a neuron?
-Dendrite
-Nucleus
-cell body
-Axon
-Myelin sheath
-Schwann cell
-Axon terminal
-Nodes of ranvier
What are the types of neurons?
Sensory
relay
motor
Where are sensory neurons found?
in the sensory organs associated with 5 different primary senses
Where is the cell body found in a sensory neuron?
extends from the axon
What does the cell body on a sensory neuron not have?
dendrites
What does the cell body on a sensory neuron not have?
dendrites
What are the features of a sensory neuron?
-Unipolar - cell body has one branch
-No dendrites on cell body
•Long dendrites connect to axon
• Myelin covers axon
What are the features of a sensory neuron?
-Unipolar - cell body has one branch
-No dendrites on cell body
•Long dendrites connect to axon
• Myelin covers axon
why she is sensory neuron unipolar?
because they only send a message one way
What is the function of a sensory neuron?
Afferent nerve cell that carries sensory impulses from the sense organs (e.g. skin) to the CNS
Where are relay neurons found?
brain and spinal chord
What are the features of relay neurons?
-Multipolar - cell body has many branches (recives and sends info)
• Short dendrites
• Several dendrites
• Short axon
• No myelin on axon
• Entirely within the CNS
What is the function of a relay neuron?
Enables sensory neurons and motor neurons to communicate
What are the features of a motor neuron?
• Multipolar - cell body has many branches
• Short dendrites
• Several dendrites
• Long axon
• Myelin covers axon.
What is the function of a motor neuron?
Efferent nerve cell that transmits nerve impulses from the CNS to muscles or glands
What is synaptic transmission?
process by which neuron’s communicate with each other
What is a synapse?
the junction between the axon of one neuron and the dendrites of another
what are the main main features of a synapse?
vesicles in the axon terminal of the pre-synaptic neuron, which are sacs filled with neurotransmitters (chemical messengers).
What is the synaptic gap/cleft?
the tiny gap between the two neurons
What do the receptors on the dendrites post synaptic neuron do?
receive the neurotransmitters.
What is the process of synaptic transmission?
-Info is passed down the axon of the pre-synaptic neuron as an electrical impulse known as an ap.
-ap reaches the axon terminal and triggers release of nt’s from vesicles.
-nt’s diffuse across the synaptic gap to carry the chemical signal from the presynaptic neuron to the post-synaptic neuron.
- nt’s bind to receptor sites on the post-‘ synaptic neuron.
-(summation) Stimulation of post-synaptic receptors can result in excitation or inhibition of the post-synaptic membrane.
how does information travel at the synapse (synaptic transmission)
it travels in one direction
What is only present in the pre synaptic membrane?
Vesicles containing neurotransmitters
What is only present on the post synaptic membrane?
Receptors for neurotransmitters
Why does info only travel in one direction at the synapse? (3)
-Vesicles containing neurotransmitters are only present in the pre-synaptic membrane.
-Receptors for neurotransmitters are only present on the post-synaptic membrane.
-During diffusion, neurotransmitters travel from levels of high concentration at the pre-synaptic membrane to levels of low concentration at the post-synaptic membrane.
What happens once neuron transmitters bind to a receptor on the post synaptic neuron and what does this determine?
they have an excitatory or inhibitory effect.
-determines whether an action potential is fired from the neuron’s cell body, which then travels along its axon.
What does excitation do? (3)
-Increases neural activation in the postsynaptic neuron (creates an excitatory post-synaptic potential).
• Makes the post-synaptic neuron more likely to fire.
• Increases the activity of other neurotransmitters.
What are is an example of excitation neurotransmitters?
Glutamate
• Necessary for cognition, memory and learning.
• High levels can over-excite neurons until they die, causing brain disorders such as Alzheimer’s disease.
What does inhibition do? (4)
-Decreases neural activation in the postsynaptic neuron (creates an inhibitory post-synaptic potential).
• Makes the post-synaptic neuron less likely to fire.
• Decreases the activity of other neurotransmitters.
-Balances periods of excitation.
What does the firing of an action potential in the post synaptic neuron depend on?
the summation (combination) of all the excitatory post-synaptic potentials and inhibitory post-synaptic potentials.
what happens if there is more excitation than inhibition?
a new action potential is created in the postsynaptic neuron.
what happens if there is more inhibition than excitation?
new action potential is not created.
What are the differences between neurotransmitters and hormones?
Neurotransmitters are produced within neurons and pass very quickly from one neuron, across the synaptic cleft, to another nearby neuron whereas hormones are secreted by glands and travel less quickly through the bloodstream to often quite distant target organs.
