Slides in this set
The nervous system carries messages around
the body using specialized cells called
Neurones convey their messages using
This method is faster and more precise than
using hormones.…read more
The nervous system is made up of two parts:
1. Central nervous system (CNS)
2. Peripheral nervous system (PNS)
Sensory neurone Motor Neurone
Sensory Organ Effector
· The central nervous system comprises of the brain and spinal chord.
· The peripheral nervous system comprises of the nerves and gangilia
outside the brain and spinal chord
· The human nervous system controls everything from breathing to
producing digestive enzymes to memory and intelligence.…read more
1. Motor neurons - these carry a message to a muscle,
gland, or other effector. They are said to be efferent, i.e. they
carry the message away from the central nervous system.
2. Sensory neurons - these carry a message in to the
CNS. They are afferent, i.e. going toward the brain or spinal
3. Interneuron - (a.k.a. association neuron, connecting
neuron) - these neurons connect one neuron with another. For
example in many reflexes interneurons connect the sensory
neurons with the motor neurons.…read more
STRUCTURAL FEATURES OF
Cell body contains a well developed nucleolus and many organelles such as lysosomes
and mitochondria. There is no mitiotic apparatus in neurones more than six months old.
However regeneration can occur.
Axon is the communication route between the cell body and the axon terminals.
Dentrites are extentions which provide a large surface area to receive information which
they then pass on to the cell body. The plasma has a high density of chemically gated ion
channels, important in impulse transmission.
Schwann Cells is a glial cell which encircles the axon. When the two ends of the cell
meet, overlapping occurs which pushes the nucleus and cytoplasm to the outside layer.
Myelin Sheath is composed of 20 30 layers of Schwann cell membrane. The
phospholipid content of the sheath offers electrical insulation -> saltatory impulse
conduction. The sheaths are not complete until late childhood so infants often have slow
responses/poor coordination. 1 out of every 3 nerve axons are insulated.
Nodes of Ranvier are unmyelinated segments of the neurone. Since these are
uninsulated, ion movements may take place which effectively lead to action potentials
`leaping' from one node to another -> saltatory conduction.
Synaptic knobs/end bulb - is important in nerve impulse conduction from one neurone to
another or from a neurone to an effector. They contain membrane enclosed sacs, synaptic
vesicles, which store neurotransmitters prior to release and diffusion to the post synaptic