Cardiovascular and Respiratory System Regulation
Stevie-Jade Lisa Vickers – BTEC Nat Diploma in Applied Science Level 3 Medical
The Nervous System Structure
In order for parts of the body and body systems to communicate with each other, a nervous system is required. This
is so that responses to various conditions and situations can be triggered. The nervous system is a complex body
system, composed of nerve cells, sub-systems and branches and receptors. It is composed of the CNS, which is the
central nervous system, as well as the PNS which is the peripheral nervous system.
The brain and the spinal cord are the components which form the central nervous system. The brain, the control
organ, consists of a brain stem, cerebellum, cerebrum, and the diencephalon. The function of the brain is to
generate thoughts, store memories as well as information and to process sensory information. The spinal cord, the
other component of the central nervous system, transmits messages to and from the brain whilst also managing
reflex actions. The PNS, peripheral nervous system, consists of cranial and spinal nerves and is divided into two sub-
systems. These systems are the autonomic and the somatic systems. The autonomic sub-system controls all
involuntary responses from muscles as well as organs and glands. The somatic sub-system controls actions which we
consciously decide to carry out (voluntary) using the skeletal muscles.
Nervous System
Central Nervous Peripheral
System Nervous System
Brain Motor Neurone Sensory Neurone
Somatic Nervous Autonomic
Spinal Cord
System Nervous System
Sympathetic
Division
Parasympathetic
Division
Fig.1: The Central and Peripheral Nervous Systems
When there are stimuli change (a change in the environment), receptors detect these changes. The stimuli are
converted into electrical nerve impulses (which are electrical disturbances that travel along the axon of a neuron). A
sensory neuron is then triggered by this and transmits any information to the sensory receptors which are found in
the central nervous system. This then triggers the relay neuron which then transmits information from the CNS
which assists in the decision as to what response to the stimuli will take place. This triggers the motor neuron to
transmit this information from the CNS (the spinal cord and brain) to the effectors which are muscles or glands that
carry out the final action.
Sensory Relay Motor
Stimulus Receptor Effector Response
Neurone Neurone Neurone
Fig.2: The Reflex Arc
, Voluntary movements are controlled by the somatic nervous system, whereas involuntary responses are controlled
by the autonomic nervous system. Involuntary responses controlled by the autonomic nervous system can be split
into two categories: the sympathetic division and the parasympathetic division. The sympathetic responses are
known as ‘fight or flight’ responses, whereas the parasympathetic responses are known as ‘rest or digest’ responses.
Autonomic Nervous System
Sympathetic
The sympathetic division of the body’s autonomic nervous system controls rapid, involuntary responses which are
required by the body.
A way in which the body may use this is within the cardiovascular system. When in a stressful situation, the body
may release a neurotransmitter called adrenaline, which sends a message actioning the fight or flight response from
the body. This would then cause the heart rate to increase, and, to supply the body with more nutrients and oxygen
from blood, widen the blood vessels. An increased amount of oxygen and nutrients is necessary for performing tasks
such as running from danger.
Another example of a sympathetic response in the body is within the respiratory system. Norepinephrine is a
neurotransmitter which may be released into the synaptic cleft during stressful situations. This neurotransmitter
could cause the body’s inner tubes of the lungs (bronchia) to widen, which in turn allows for more oxygen to be
taken into the bloodstream.
Parasympathetic
The parasympathetic division of the body’s autonomic nervous system controls more slow involuntary responses
that help the body to relax rather than ‘fight or flight’.
Neurones
Neurones bundle together and form what we know as nerves. Neurones are made up of a cell body, dendrons, an
axon, myelin sheath, Nodes of Ranvier, and Schwann cells. The cell body of a neurone contains the nucleus of the
neurone and a large amount of rough endoplasmic reticulum (RER) which produces proteins and neurotransmitters.
Dendrons within a neurone are responsible for the carrying of nerve impulses towards the cell body. The axon is a
single, long fibre which does the opposite of
dendrons, and carries nerve impulses away
from the cell body.
Schwann cells are cells which wrap around
the axon numerous times to protect it and
provide the axon with electrical insulation.
Schwann cells are responsible for nerve
regeneration. The membranes of Schwann
cells make up the myelin sheath, which is
Fig.3: Diagram of a neuron what covers the axon, providing electrical
insulation. The myelin sheath can be either
myelinated or unmyelinated. Nerve impulses are transmitted faster by myelinated neurones. The main difference
between the two, myelinated and unmyelinated, is that unmyelinated nerve fibres lack myeline insulation.
The nodes of Ranvier within a neurone are the gaps between Schwann cells where there is no myelin sheath.
Sensory Neurons have a cell body, a short axon, and
long dendrites. Motor neurons, on the other hand,
have short dendrites and a long axon, as well as a cell
body. Motor neurons conduct impulses to an effector
(which is either a muscle or gland). Sensory neurons,
however, conduct impulses to the CNS (central
nervous system).
Fig.3.1: Diagram of sensory and motor neurons
