Introduction to peripheral nervous system Flashcards
What are the two types of principle cells in the nervous system?
neurones
neuroglia
What are the two basic functions of neuroglia?
- Support, nurture and protect neurones
- Maintain the homeostasis (balance) of the fluid that bathes neurones
what are the 3 basic functions of neurones?
- Receive signals (or information).
- Integrate incoming signals (to determine whether or not the information should be passed along).
- Communicate signals to target cells (other neurons or muscles or glands).
Are neuroglia excitable? what does this mean?
they are non-excitable as they do not transmit impulses
why do neurones vary in size, shape and characteristics?
because they have different features depending on their role
What does the cell body of a neurone look like?
star shaped with nucleus in the centre
The cell body is the neurones _____
core
what are the three functions of the neurone’s cell body?
- to hold genetic information
- maintain structure
- provide energy to drive activity
What does the cell body contain? (3)
- the nucleus
- the cytoplasm
- organelles within the cytoplasm
where are the dendrites located on a neutron?
they are the root like shapes on the ends of the points of the cell body
What is the functions of dendrites?
- to receive incoming information
What are the two types of signals that dendrites can receive?
excitatory or inhibitory
what do excitatory impulses do to the neuron?
they make the neurone fire and generate an electrical impulse
what do inhibitory impulses do to the neuron?
they keep the neuron from firing
Most neurones receive ______ input signals through the ________, receiving thousands of input signals.
many
dendrites
whether or not a neurone is exited into firing an impulse depends on what?
the amount of excitatory and inhibitory signals it receives
If a neurone does end up firing, Where does the nerve impulse (or action potential) go?
the nerve impulse, or action potential, is conducted down the axon.
What shape and size is the axon?
it is the same diameter for most of its length and doesn’t have any spines
its size is dependent on its function
does a larger diameter axon has the ability to send signals faster or slower than a smaller axon?
much faster
what is the name of the special fatty insulating substance that covers many axons? what does this form?
myelin which forms the myelin sheath
What secrets myelin in the fibres of the peripheral nervous system?
Schwann cells
what secrets myelin in the fibres of the central nervous system?
oligodendrocytes
what is the function of the myelin sheath?
it helps to contain the nerve impulse, allowing it to move rapidly along the axon
What are the gaps along the myelin sheath? are they myelinated?
nodes of ranvier, they are non-myelinated
What is the function of the nodes of ranvier?
they expose the axon at various points to allow for regeneration of the impulse which supports the speed at which the nerve impulse passes along the axon
Where do axons arise from the cell body?
at a cone-shaped elevation called the axon hillock
what is the first portion of the axon called and what arises here? what name does this also give it?
the initial segment
the nerve impulse
the trigger zone
along the length of the axon there may be side branches called ____ ________ which are typically at ______ angles to the axon.
axon collaterals
right
What is at the end of the axon?
fine processes called the axon terminals
What does the tip of the axon terminal bulge out to form?
the synaptic bulb
what does the synaptic bulb contain?
neuro-transmitting chemicals
What is the small gap between one neurone and the next or the target cell called?
the synapse/synaptic cleft