Download the nervous system

THE NERVOUS SYSTEM
Learning Outcomes
• C11 – analyse the transmission of
nerve impulses
– Describe the structure of a neuron
– Identify the function of dendrite, axon,
cell body, axoplasm, axomembrane
– Differentiate between sensory, motor
and interneurons
• Consists of the
brain, spinal cord
and nerves
throughout the body
Central Nervous System
• CNS consists of the
brain and spinal
cord
Peripheral Nervous System
• PNS consists of
nerves throughout
the body
• Carries messages to
and from the CNS
Neurons
• Neurons are nerve
cells
• Neurons have 3
main parts
• Cell body contains the
nucleus and organelles
• Axon transmits an
impulse away from the
cell body to the next cell
• Dendrite receives an
impulse and transmits it
to the cell body
• Axoplasm refers to the
cytoplasm within the
axon
• Axomembrane refers to
the plasma membrane
of the axon
• Long axons are
covered in a myelin
sheath
• Nodes of Ranvier
are intermittent gaps
in the sheath
• Schwann cells
wrapped around the
axon contain myelin
(a specialized
phospholipid) in
their plasma
membranes
Types of Neurons
• Sensory neurons carry impulses from
sensory receptors to the CNS
• Have long dendrites
• Motor neurons carry impulses from the
CNS to an effector (muscle or gland)
• Have long axons
• Interneurons connect other neurons to
the CNS
Fig. 17.2
Transmission of Nerve
Impulses
• Nerve impulses travel along neurons by
means of electrochemical changes in
the neuron membranes
• The space between neurons is called
the synapse
• Neurotransmitters carry impulses
across the synapse