Coordination
There are communication systems within animals that coordinate the activities of
receptors and effectors. The information they receive comes from the internal and
the external environment. So there are receptors that detect stimuli inside the body
and receptors that detect stimuli in the surrounding environment. In animals there
are two types of information transfer that are used to coordinate the body’s
activities:
Nerves that transmit information in the form of electrical impulses
Chemical messengers called hormones that travel in the blood
Nervous communication
The central nervous system is made up of the brain and the spinal cord and the
peripheral nervous system is made up of the cranial and spinal nerves.
Nerve cells are also called neurones and they carry information directly to their
target cells. Neurones coordinate the activities of sensory receptors such as those in
the eye, decision-making centres in the CNS ad effectors such as muscles and glands.
There are three types of neurone:
Sensory neurones – transmit impulses from receptors to the CNS
Intermediate neurones (relay neurones) – transmit impulses from sensory
neurones to motor neurones
Motor neurones – transmit impulses from the CNS to effectors
The cell body of a motor neurone lies within the spinal cord or brain. There are small
regions of rough endoplasmic reticulum that synthesise proteins in the cytoplasm.
Thin cytoplasmic processes extend from the cell body and have many branches called
dendrites to give a large surface area for the ends of other neurones. The axon is very
long and contains organelles such as mitochondria.
Sensory neurones have a cell body that is in a swelling called a ganglion.
Myelin
Myelin is made of specialised celled called Schwann cells that surround the axons of
some neurones but some are unmyelinated. Myelin is made when Schwann cells
wrap around the axon all along its length and enclose it forming a myelin sheath. The
sheath affects the speed of conduction of the nerve impulse. The small, uncovered
areas of axon between the Schwann cells are called nodes of Ranvier.
There are communication systems within animals that coordinate the activities of
receptors and effectors. The information they receive comes from the internal and
the external environment. So there are receptors that detect stimuli inside the body
and receptors that detect stimuli in the surrounding environment. In animals there
are two types of information transfer that are used to coordinate the body’s
activities:
Nerves that transmit information in the form of electrical impulses
Chemical messengers called hormones that travel in the blood
Nervous communication
The central nervous system is made up of the brain and the spinal cord and the
peripheral nervous system is made up of the cranial and spinal nerves.
Nerve cells are also called neurones and they carry information directly to their
target cells. Neurones coordinate the activities of sensory receptors such as those in
the eye, decision-making centres in the CNS ad effectors such as muscles and glands.
There are three types of neurone:
Sensory neurones – transmit impulses from receptors to the CNS
Intermediate neurones (relay neurones) – transmit impulses from sensory
neurones to motor neurones
Motor neurones – transmit impulses from the CNS to effectors
The cell body of a motor neurone lies within the spinal cord or brain. There are small
regions of rough endoplasmic reticulum that synthesise proteins in the cytoplasm.
Thin cytoplasmic processes extend from the cell body and have many branches called
dendrites to give a large surface area for the ends of other neurones. The axon is very
long and contains organelles such as mitochondria.
Sensory neurones have a cell body that is in a swelling called a ganglion.
Myelin
Myelin is made of specialised celled called Schwann cells that surround the axons of
some neurones but some are unmyelinated. Myelin is made when Schwann cells
wrap around the axon all along its length and enclose it forming a myelin sheath. The
sheath affects the speed of conduction of the nerve impulse. The small, uncovered
areas of axon between the Schwann cells are called nodes of Ranvier.
