, Coordination
rganisms need to the function of different
cells and systems to operate properly
ommunication systems in organisms must be
coordinated to produce the required response to
changes in the environment
respond to change through electrical responses
(via neurones) and through chemical responses (via
hormones)
responses are based on chemical communication
systems including plant hormones. For example plants
row towards a light source to maximise photosynthesis,
due to the hormone auxin.
Maintenance of a constant internal
environment achieved by coordination of different
organs.
, Neurones
The nervous system is responsible for detecting changes in the internal and
external environment. The changes are known as the stimulus, which processes the
information to trigger an appropriate response.
The nervous system is made up of billions of nerve cells called neurones.
Neurones transmit electrical impulses rapidly around the body so that the
organisms can respond to change.
Key features of mammalian neurones
• Cell body- Contains the nucleus surrounded by cytoplasm. Within the cytoplasm
there are also large amounts of endoplasmic reticulum & mitochondria which are
involved in the production of neurotransmitters
• Dendrons (before cell body)- Short extensions which come from the cell body.
These extensions divide into smaller branches known as dendrites. They are
responsible for transmitting electrical impulses towards the cell body. The more
branches the more connections able to be made.
• Axons (after cell body)- Singular, elongated nerve fibres that transmit impulses
away from the cell body. These fibres can be very long, cylindrical in shape
consisting of a very narrow region of cytoplasm surrounded by a plasma membrane.
• Schwann cells- Produce protein called myelin forming a myelin sheath made from
many layers of plasma membrane covering the axon (myelinated neuron). This
provides an insulating layer to speed up transmission of impulse.
• Nodes of Ranvier- Gaps between schwann cells.
, Types of neurone
Sensory neurone (afferent
neuron)-Transmits impulses from
sensory receptor cell to the
central nervous system (brain &
spinal cord)
Relay neurone- Sends electrical
impulse from sensory to motor
neurone within the CNS. Axon &
Dendron both very short so no
schwann cells or myelin sheath.
Motor neurone (efferent neuron)-
Sends electrical impulses from CNS
to the effector (muscle or glands)
Axon longer than sensory neurone
rganisms need to the function of different
cells and systems to operate properly
ommunication systems in organisms must be
coordinated to produce the required response to
changes in the environment
respond to change through electrical responses
(via neurones) and through chemical responses (via
hormones)
responses are based on chemical communication
systems including plant hormones. For example plants
row towards a light source to maximise photosynthesis,
due to the hormone auxin.
Maintenance of a constant internal
environment achieved by coordination of different
organs.
, Neurones
The nervous system is responsible for detecting changes in the internal and
external environment. The changes are known as the stimulus, which processes the
information to trigger an appropriate response.
The nervous system is made up of billions of nerve cells called neurones.
Neurones transmit electrical impulses rapidly around the body so that the
organisms can respond to change.
Key features of mammalian neurones
• Cell body- Contains the nucleus surrounded by cytoplasm. Within the cytoplasm
there are also large amounts of endoplasmic reticulum & mitochondria which are
involved in the production of neurotransmitters
• Dendrons (before cell body)- Short extensions which come from the cell body.
These extensions divide into smaller branches known as dendrites. They are
responsible for transmitting electrical impulses towards the cell body. The more
branches the more connections able to be made.
• Axons (after cell body)- Singular, elongated nerve fibres that transmit impulses
away from the cell body. These fibres can be very long, cylindrical in shape
consisting of a very narrow region of cytoplasm surrounded by a plasma membrane.
• Schwann cells- Produce protein called myelin forming a myelin sheath made from
many layers of plasma membrane covering the axon (myelinated neuron). This
provides an insulating layer to speed up transmission of impulse.
• Nodes of Ranvier- Gaps between schwann cells.
, Types of neurone
Sensory neurone (afferent
neuron)-Transmits impulses from
sensory receptor cell to the
central nervous system (brain &
spinal cord)
Relay neurone- Sends electrical
impulse from sensory to motor
neurone within the CNS. Axon &
Dendron both very short so no
schwann cells or myelin sheath.
Motor neurone (efferent neuron)-
Sends electrical impulses from CNS
to the effector (muscle or glands)
Axon longer than sensory neurone
