Category Archives: Chapter 2 – Body Coordination

Coordination Between The Nervous System and The Endocrine System


(a) both respond to stimuli
(b) Coordinate the body’s activities and functions
(c) Have target organs


The main difference between these two systems is that the nervous system co-ordinates the body through electrical impulses whereas the endocrine system also co-ordinates bodily functions but is composed of glands that excrete hormones. The nervous system controls muscle movement, senses, heartbeat, breathing, digestion, memory and speech whilst the endocrine system controls levels of glucose in the blood, hydration levels, heat productivity, sexual maturity, sperm and egg production and growth of cells and tissues.


The nervous system:
effect is localized
take shorter time to produce a reaction
duration of a reaction is shorter
do not require hormone


The endocrine system:
effect is widespread
take longer time to produce a reaction
duration of a reaction is longer
involve hormone as an organic messenger

Coordination between the nervous system and the endocrine system is very important.


This coordination :
Enable the body to carry out its activities and functions efficiently and smoothly.
Enables the body to respond to stimuli effectively so as to take action quickly and avoid injury.
Enables the nervous system to detect changes in the body or environment and relate it to the endocrine system for producing the hormones required for join response and action.
Without coordination between the nervous system and the endocrine system , the body cannot function as a whole .


The Human Nervous System

The human nervous system may be conveniently subdivided into two divisions: the central nervous system (the brain and spinal cord) and the peripheral nervous system (the nerves extending to and from the central nervous system).


The central nervous system is the control centre of the nervous system. The peripheral nervous system link receptors and effectors with the central nervous system. Nerves from the brain are called cranial nerves, wheres those from the spinal cord are called spinal nerves.



The spinal cord of the central nervous system is a white cord of tissue passing through the bony tunnel made by the vertebrae. The spinal cord extends from the base of the brain to the bottom of the backbone. Three membranes called meninges surround the spinal cord and protect it. The outer tissue of the spinal cord is white (white matter), while the inner tissue is gray (gray matter). A central canal in the spinal cord carries cerebrospinal fluid, which provides for the nutrition and gaseous needs of the cord tissue. The neurons of the spinal cord serve as a coordinating center for the reflex arc and a connecting system between the peripheral nervous system and the brain.

The peripheral nervous system is a collection of nerves that connect the brain and spinal cord to other parts of the body and the external environment. It is subdivided into the sensory somatic system and the autonomic nervous system.


The sensory somatic system carries impulses from the external environment and the senses. It consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves. The sensory somatic system permits humans to be aware of the outside environment and react to it voluntarily.

The autonomic nervous system works on an involuntary basis. It consists of two groups of motor neurons and a set of knotlike groups of cell bodies called ganglia. Motor neurons extend to and from the ganglia to the body organs. One subdivision of the autonomic nervous system is the sympathetic nervous system. Impulses propagated in this system prepare the body for an emergency. They cause the heartbeat to increase, the arteries to constrict, the pupils to dilate, and other changes to take place. The other subdivision is the parasympathetic nervous system. Impulses in this system return the body to normal after an emergency has occurred.


The Endocrine System


The endocrine system, along with the nervous system, functions in the regulation of body activities. The nervous system acts through electrical impulses and neurotransmitters to cause muscle contraction and glandular secretion. The effect is of short duration, measured in seconds, and localized.

The endocrine system acts through chemical messengers called hormones that influence growth, development, and metabolic activities. The action of the endocrine system is measured in minutes, hours, or weeks and is more generalized than the action of the nervous system.

The endocrine glands do not have ducts to carry their product to a surface. They are called ductless glands. The word endocrine is derived from the Greek terms “endo,” meaning within, and “krine,” meaning to separate or secrete. The secretory products of endocrine glands are called hormones and are secreted directly into the blood and then carried throughout the body where they influence only those cells that have receptor sites for that hormone. Specific hormones are “recognized” only by their target cells and organs and won’t affect any other tissues.

The main endocrine glands in the humans are the pituitary gland, thyroid gland, adrenal gland, pancreas, ovary and testis



Hormones influence many aspects of the body environment, the hormone-triggered chemical changes inside the body’s cells influence numerous complex body processes including :-
Energy levels
Growth, development and healing of all body tissues
Internal balance of body systems, called homeostasis
Responses to surroundings, stress and injury
Metabolism and metabolic health or disease

Hormone levels are affected by aging, stress, disease and lifestyle factors such as diet, exercise, sleep and substance use. As hormones control many body activities, undersecretion or oversecretion of hormones can affect one’s health. These phenomenons are known as hormonal imbalance. Hormones need to be balanced in order to work properly. Too much or too little can impact your health, potentially and seriously.

Common conditions are associated with hormonal imbalances:
Weight gain (especially the waistline)
Loss of muscle mass
Bone loss
Chronic fatigue
Poor immune function
High cholesterol
Decreased libido



Structure and Functions of The Human Brain


The brain is one of the largest organ and most complex organ in the human body. Being so important and yet fragile the brain is protected by a hard bony skull. It is made up of more than 100 billion nerves that communicate in trillions of connections called synapses.The brain is surrounded by a layer of tissue called the meninges.
The main parts of the brain are the cerebrum, cerebellum and medulla oblongata.

Cerebrum is the largest and most highly developed part of the human brain. It encompasses about two-thirds of the brain mass and lies over and around most of the structures of the brain. The outer portion (1.5mm to 5mm) of the cerebrum is covered by a thin layer of gray tissue called the cerebral cortex. The cerebrum is divided into right and left hemispheres that are connected by the corpus callosum. Each hemisphere is in turn divided into four lobes.

• The frontal lobes are responsible for problem solving and judgment and motor function.
• The parietal lobes manage sensation, handwriting, and body position.
• The temporal lobes are involved with memory and hearing.
• The occipital lobes contain the brain’s visual processing system.

The cerebrum is involved in several functions of the body including:
Determining Intelligence
Determining Personality
Producing and Understanding Language
Interpretation of Sensory Impulses
Motor Function
Planning and Organization
Touch Sensation


Cerebellum is sometimes referred to as the “little brain,” the cerebellum lies on top of the pons, behind the brain stem. The cerebellum is comprised of small lobes and receives information from the balance system of the inner ear, sensory nerves, and the auditory and visual systems. It is involved in the coordination of motor movements as well as basic facets of memory and learning.


The medulla oblongata is a portion of the hindbrain that controls autonomic functions ( involuntary actions) such as breathing, digestion, heart and blood vessel function, swallowing and sneezing. Involuntary actions are actions that cannot be controlled by our conscius mind. Motor and sensory neurons from the midbrain and forebrain travel through the medulla. As a part of the brainstem, the medulla oblongata helps in the transferring of messages between the brain and the spinal cord.


The Role of Proprioceptors (Stretch receptors) in Maintaining Balance and Coordination


There are stretch receptors in the muscles, tendons and ligaments in the body. When these receptors are stimulated by being stretched or compressed , they send out nervous impulses to the brain or the spinal cord.These stretch receptors act as internal sensory organs and are called proprioceptors. These proprioceptors enable us to carry out muscular activities without having to watch them and also coordinate the movement and maintain balance. Proprioceptors are involved in many of our daily activities, such as walking, buttoning the shirt, typing and cycling.


The Vertebrae, The Spinal Cord and The reflex Arc


The Human Vertebrae

The Anatomy of the Spine – The Bones

The human spine is composed of 26 individual bony masses, 24 of those are bones called vertebrae. The vertebrae are stacked one on top of the other and form the main part of the spine running from the base of the skull to the pelvis. At the base of the spine, is a bony plate called the sacrum which is made of 5 fused vertebrae. The sacrum forms the back part of the pelvis. At the bottom of the sacrum is a small set of 4 partly fused vertebrae, the coccyx or tailbone. Adding the fused and partly fused bones of the sacrum and coccyx to the 24 vertebrae, the spine has 33 bones all together.

The spine is labeled in 3 sections: the cervical spine, the thoracic spine and the lumbar spine. Starting from the top there are 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae.

Spinal Cord Overview




The Spinal Cord is connected to the brain and is about the diameter of a human finger. From the brain the spinal cord descends down the middle of the back and is surrounded and protected by the bony vertebral column. The spinal cord is surrounded by a clear fluid called Cerebral Spinal Fluid (CSF), that acts as a cushion to protect the delicate nerve tissues against damage from banging against the inside of the vertebrae.

The anatomy of the spinal cord itself, consists of millions of nerve fibres which transmit electrical information to and from the limbs, trunk and organs of the body, back to and from the brain. The nerves which exit the spinal cord in the upper section, the neck, control breathing and the arms. The nerves which exit the spinal cord in the mid and lower section of the back, control the trunk and legs, as well as bladder, bowel and sexual function.

The nerves which carry information from the brain to muscles are called Motor Neurones. The nerves which carry information from the body back to the brain are called Sensory Neurones. Sensory Neurones carry information to the brain about skin temperature, touch, pain and joint position.

Cross-sectional of spinal cord

Reflex Action and Reflex Arc

Reflex action is the involuntary functioning or movement of any organ or body part in response to a particular stimulus. The function or action occurs immediately, without the involvement of the will or consciousness.

A reflex arc is a neural pathway that controls an action reflex. In higher animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This characteristic allows reflex actions to occur relatively quickly by activating spinal motor neurons without the delay of routing signals through the brain, although the brain will receive sensory input while the reflex action occurs.

The knee-jerk reaction

The pathway for this reflex arc starts at a stretch receptor within the tendon. Hitting this receptor stimulates it, which causes it to send a nerve impulse along a sensory neuron to the spinal cord. Within the spinal cord, the nerve impulse passes from the sensory neuron to a motor neuron and travels back to the thigh muscle. When the impulse arrives at the thigh muscle, it causes it to contract and jerk the lower part of the leg upward. The person is aware that this is happening, so sensory impulses do travel from the spinal cord to the brain, but there is nothing that can be done to stop it happening.



The basic unit in the nervous system is the neurone.The neuron is made up of different parts. They are sort of like regular cells because they have a nucleas, cytoplasm, and have a membrane. Yet they are different because they have special part (fibers) called dendrites and axon. Dendrites are fibers all over the cell body leading in different ways. There are many dendrites. Dendrites are the part of a neuron that take nerve impulses in. The axon is also leaving the cell body.  It goes until the synaptic buttons. There are not any branches off from the axon unless it is at the end. The axon is surrounded by a protective layer called the myelin sheath. The axon carries nerve pulses away. At the end of the axon are the synaptic buttons. The synaptic buttons connect to other neurons.Neurones come in many sizes and can be devided into three basic types, namely sensory neurone, motor neurone and relay neurone.

Sensory neurones are connected to receptors or sensory organs. They transmitted impulses from the sensory organs to the central nervous system. sensory neurons have dendrites on both ends, connected by a long axon with a cell body in the middle.

P62 sensory neuron

 Motor neurons that control muscle contractions have a cell body on one end, a long axon in the middle and dendrites on the other end;


Relay neurones are located in the central nervous system. They connect sensory neurones to motor neurones and transmit impulses between these two neurones.


The similarities between the three types of neurones are
(a) they all have a cell body
(b) they all have dendrons and dendrites
(c) they all can recieve and send out impulses