H.
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 9: Human Regulation and Reproduction
Assignment 9A: Understand the interrelationship and
nervous control of the cardiovascular and respiratory
systems
Organisation of the nervous system
The nervous system is divided into 2 separate systems, as shown in Figure 1:
- CNS (central nervous system), made of the brain and spinal cord
- PNS (peripheral nervous system), made of neurones that link the CNS to the rest of
the body
The PNS can then be divided into the somatic and autonomic nervous system, which have
differing functions. The somatic nervous system is responsible for conscious activities, like
running/walking, whereas the autonomic nervous system is in charge of unconscious
activities, e.g. breathing. The autonomic nervous system can also be divided into 2 systems
that have opposite effects on the body – the sympathetic and parasympathetic nervous
system. The sympathetic system can be known as the ‘fight or flight’ system, this is because
it prepares the body for action. This is opposite for the parasympathetic system as it can be
known as the ‘rest/digest’ system, this is because it relaxes the body down. Both these
systems release neurotransmitters - the sympathetic system releases noradrenaline (a
neurotransmitter which connects to the sinoatrial node in the heart) whereas the
parasympathetic system releases acetylcholine (a neurotransmitter which connects to the
sinoatrial node in the heart).
Figure 1 – Diagram of the organisation of the nervous system
1
, H.
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 9: Human Regulation and Reproduction
Types of neurons
Sensory
Sensory neurons are nerve cells that identify and respond to external signals.
They send and receive electrical impulses through receptors and send them to
the CNS (central nervous system). Also, the electrical impulses operate as
signals and are received by the spinal cord and brain, which are part of the CNS.
A sensory neuron is made of dendrites, an axon and a cell body- see Figure 2 for
a detailed diagram of a sensory neuron. It starts with the dendrites, since this is
the location where the impulse/signal is received, and ends with the axon, which
is the fibre used to carry signals away and communicate with the spinal cord.
The dendrites are relatively long whereas the axon is quite short. The cell body is
where the nucleus, cytoplasm and other organelles are found. Moreover, a
sensory neuron has a myelin sheath which has a layer of Schwann cells,
protecting nerve fibres by acting as an insulator.
Most sensory neurons can be referred to as pseudo unipolar, which means they
have 1 axon that expands from the cell body and forms 2 extensions - the
dendrites and the axon. In pseudo unipolar sensory neurons, the cell body is
found on a side branch of the nerve fibre.
Figure 2 – Diagram of a sensory neuron
2
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 9: Human Regulation and Reproduction
Assignment 9A: Understand the interrelationship and
nervous control of the cardiovascular and respiratory
systems
Organisation of the nervous system
The nervous system is divided into 2 separate systems, as shown in Figure 1:
- CNS (central nervous system), made of the brain and spinal cord
- PNS (peripheral nervous system), made of neurones that link the CNS to the rest of
the body
The PNS can then be divided into the somatic and autonomic nervous system, which have
differing functions. The somatic nervous system is responsible for conscious activities, like
running/walking, whereas the autonomic nervous system is in charge of unconscious
activities, e.g. breathing. The autonomic nervous system can also be divided into 2 systems
that have opposite effects on the body – the sympathetic and parasympathetic nervous
system. The sympathetic system can be known as the ‘fight or flight’ system, this is because
it prepares the body for action. This is opposite for the parasympathetic system as it can be
known as the ‘rest/digest’ system, this is because it relaxes the body down. Both these
systems release neurotransmitters - the sympathetic system releases noradrenaline (a
neurotransmitter which connects to the sinoatrial node in the heart) whereas the
parasympathetic system releases acetylcholine (a neurotransmitter which connects to the
sinoatrial node in the heart).
Figure 1 – Diagram of the organisation of the nervous system
1
, H.
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 9: Human Regulation and Reproduction
Types of neurons
Sensory
Sensory neurons are nerve cells that identify and respond to external signals.
They send and receive electrical impulses through receptors and send them to
the CNS (central nervous system). Also, the electrical impulses operate as
signals and are received by the spinal cord and brain, which are part of the CNS.
A sensory neuron is made of dendrites, an axon and a cell body- see Figure 2 for
a detailed diagram of a sensory neuron. It starts with the dendrites, since this is
the location where the impulse/signal is received, and ends with the axon, which
is the fibre used to carry signals away and communicate with the spinal cord.
The dendrites are relatively long whereas the axon is quite short. The cell body is
where the nucleus, cytoplasm and other organelles are found. Moreover, a
sensory neuron has a myelin sheath which has a layer of Schwann cells,
protecting nerve fibres by acting as an insulator.
Most sensory neurons can be referred to as pseudo unipolar, which means they
have 1 axon that expands from the cell body and forms 2 extensions - the
dendrites and the axon. In pseudo unipolar sensory neurons, the cell body is
found on a side branch of the nerve fibre.
Figure 2 – Diagram of a sensory neuron
2
