Neurones Flashcards
What is the role of neurones?
tjere are billions of neurones (specialised nerve cells)
transmit electrical impulses rapidly around the body so that the organism can respond to changes in its internal and external environment
there are several different types found within a mammal, they work together to carry information detected by a sensory receptor to the effector, which in turn carries out the appropriate response
What is the cell body of a neurone?
contrains:
- nucleus surrounded by cytoplasm
- large amounts of endoplasmic reticulum and mitochondria (involved in the production of neurotransmitters)
What are dendrons?
short extensions which come from the cell body
these divide into smaller and smaller branches known as dendrites
they are responsible for transmitting electrical impulses towads the cell body
What are axons?
singular, elongated nerve fibres thjat transmit impules away from the cell body
these can be very long, e.g. those that connect the trips of the toes and fingers to the spinal cord
cylindrical and consists of a very narrow region of cytoplasm, surrounded by a plasma membrane
What is a sensory neurone?
these neurones transmit impulses from a sensory receptor cell to a relay neurone, motor neurone, or the brain
they have one dendron, whichc arries the impulse to the cell body, and one axon, which carries the impulse away fromt he cell body
What is a relay neurone?
these neurones transmit impulses between neurones
e.g. between sensory neurones and motor neurones
they have many short axons and dendrons
What is a motor neurone?
transmit impulses from a relay neurone or sensory neurone to an effector, such as a muscle or a gland
they have one long axon and many short dendrites
What pathway do most nervous responses follow?
receptor → sensory neurone → relay neurone → motor neurone → effector cell
What is a myelin sheath?
covers axons of some neurones
made of many layers of plasma membrane
How is meylin sheath produced?
Schwann cells
grow around the axon many times
each time they grow around the axon, a double layer of phospholipid bilayer is laid down
What is the function of the myelin sheath of myelinated neurones?
insulating layers, allows neurones to conduct the electrical impulse at a much faster speed that unmyelinated neurones
What is the node of Ranvier?
between each adjacent Schwann cell there is a small gap, known as the node of ranvier
What is the function of the node of Ranvier?
the electrical impulse ‘jumps’ from one node to the next as it travels along the neurone
this allows the impulse to be transmitted much faster
