nerve tissue Flashcards
in higher animals the nervous system is specialised to have two main types
receptors (receive stimuli)
effectors (react to stimuli)
nerve cells
known as neurons
responsible for how we act and react to our environment
elongated cells with different outgrowths
Nissl granules
groundplasm of the cell body contains dark, granular structures
large quantities of RNA, with ribosomes
two types of outgrowths
dendrites
axon
dendrites
receive impulses
afferent outgrowths
axon
relays impulses to the next neuron
efferent outgrowths
neurilemma
enclosed in a series of consecutive cells that form a tough wrap
Schwann cells
where neurons occur outside the spine and brain
myelin sheath
Schwann cells form a sheath around the axon and secrete a further protective layer
nodes of Ranvier
interruptions in the sheath around the axon
outgrowths of neurons
found inside the brain and spinal cord are not covered with a myelin sheath
neurons are classified according to their function
motor neurons
sensory neurons
interneurons
motor neurons
take impulses from the central nervous system to the effectors
also called efferent neurons
sensory neurons
receive impulses from the receptors and take them to the central nervous system where they are processed
also called afferent neurons
interneurons
occur inside the central nervous system
also called connecting neurons
afferent neurons
neurons and other structures move towards a structure
efferent neurons
neurons move away from these structures
structure of neurons
bipolar neurons
unipolar neurons
multipolar neurons
bipolar neurons
one dendrite and one axon
interneurons are often bipolar
unipolar neurons
have one outgrowth that splits into a T, with an afferent (dendrite) and efferent (axon) outgrowth
sensory neurons are unipolar
multipolar neurons
have one axon but many dendrites
they can make contact with many other neurons
motor neurons and interneurons are multipolar
