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Mapa Mental por harry_bygraves, atualizado more than 1 year ago
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Criado por harry_bygraves
mais de 11 anos atrás
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Motor
neurones
- A mammalian motor neurone can generate and conduct impulses. In doing so, it covneys information rapidly over
considerable distances. A single nerve impulses may be transmitted from the spinal cord to the feet in a few milliseconds.
- The structure of a motor neurone. A typical motor neurone has a cell body containing a nuleus and other organelles. In
the cytoplasm of the cell body are Nissl granules- these contain parallel rows of the endoplasmic reticulum and
assoicated ribosomes. Dendrites, highly branched cytoplasmic extensions about 1mm long, recieve incoming information
from other cells and conduct nerve impuleses towards the body. A fine process called the axon extends from the cell
body to the target cells. The conical region where an axon joins the cell body is called an axon hillock. the axon hillock
integrates the incoming information from the dendrites and initiates a nerve impulse. the axon transmits outgoing nerve
impulses from the cell body to the target cell. Axons and dendrons are often refered to as nerve fibres.
- At the target cell, the axon divides into a number of nerve endings. the tip of each nerve ending has a swelling
called the axon terminal. a narrow gap called the synaptic cleft seperates the membrane of an axon terminal
from the membrance of a target cell. the junction between one neurone and another cell is called a synapse.
- The axons of many mammalian motor neurones are enclosed along most of their length by a thick
insulating material called the myelin sheath. the myelin sheath is produced by special supporting cells
called Schwann cells. The sheath is essentially a series of cell membrances, each produced by a single
schwann cell and wrapped many times around the axon. Gaps between the membranes of one schwann
cell and the next are called nodes of ranvier. they play a key role in the fast transmisson of nerve impulses
- Fast transmission enables mammals to respond almost instantaneously to stimuli. nerve impulses can be
directly along the nerve fibres to specific points in the body so that responses can be very localised.
- Invertebrate neurones are not myelinated. The speed of conduction of their
nerve impulses depends, amoung other things, on the diameter of the
neurone
- Structures and functions
- Dendirtes;
- Branched and
numerous allowing
many synaptic
connections with
other neurones
- Recieve
incoming
information
- Branched and
numerous allowing
many synaptic
connections with
other neurones
- Cell body
- Has a large volume to
accomodate a nucleus
and organelles
- Densely packed with mitrochondria
to provide the ATP needed to
generate a nerve impule
- Nissl granules
manufacture proteins
- Has a large volume to
accomodate a nucleus
and organelles
- Axon
- Carries outgoing nerve
impulses to target cells
- Long and thin to
conduct impulses over
a long distance rapidly
- Carries outgoing nerve
impulses to target cells
- Schwann cell
- produce a myelin
sheath that acts as an
electrical insulator for
the axon
- produce a myelin
sheath that acts as an
electrical insulator for
the axon
- Nodes of Ranvier
- Gaps in the myelin sheath
that allow a nerve impulse to
jump from one to the next,
speeding up the condition of a
nerve impulse
- Gaps in the myelin sheath
that allow a nerve impulse to
jump from one to the next,
speeding up the condition of a
nerve impulse
- Axon
terminals
- highly branched to
increase the contact area
betwen an motor neurone
and its target cell
- Bulbous end contain
neurotransmitter which is
released when a nerve
impulse reaches it
- highly branched to
increase the contact area
betwen an motor neurone
and its target cell
- Dendirtes;
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