UNIT 1
Human Organ System
Human body consists of many organs. Different body parts coordinate to work properly. This coordination of body parts is called Organ system. Many organ systems are working within the human body. Some of which are given below:
- Nervous System
- Excretory System
- Circulatory System
- Respiratory System
- Reproductive System
- Digestive System
In this chapter, we will study Nervous system and Excretory System.
NERVOUS SYSTEM
Just imagine that you are watching television, and you want to turn up the volume. Without taking your eyes off the screen, you find the remote control on a table next to you. You will not touch a glass of water lying on the table because it does not feel like the remote.Your brain is the interpretation of the motivation collected through your communication.if you had no way to interpret each stimulus, you might pick up any other item on the table instead the remote.It is Divided into two parts.
- The central nervous system
- The peripheral nervous system
The Central Nervous System (CNS)
The Central Nervous System is divided into two parts. i.e.
- The Brain
- The Spinal Cord.
The Brain
The brain of an adult human being weights about 1300-1400 gram and has more than 100 billion neurons. The brain is protected by three layers of connective tissues called meninges.Between the layers of Meninges is fluid. The fluid protects the brain.The brain itself has three main parts called
- Fore brain,
- Mid brain
- and Hind brain.
Fore-Brain
It is the part of your brain that interprets signals from the body and form responses such as hunger, thirst, emotions and pain.The cerebrum has right and left halved,or hemispheres.
Each hemisphere controls the opposite side of the body, for example, right side control the left side of the body and left side control the right side of the body. Each hemisphere of the human brain is divided into four lobes. i.e; Frontal Lobe, Parietal Lobe. Occipital Lobe and Temporal Lobe.
i:- Mid-Brain
It is the central part of brain. Its basic function is to transfer information and impulses between fore-brain and hind brain.The midbrain also controls some reflexes, such as changing the size of the pupil to control the amount of light entering the eye.
ii:- Hind-Brain
It is the rear-most part of the brain. It has three basic parts; Cerebellum, Pons and Medulla oblongata.Cerebellum is the part of the brain that coordinates body movements.it helps to maintain body posture balance and it automatically adjusts the body to move smoothly.
Pons regulates breathing and passes signals between the brain and the spinal cord. The medulla Oblongata connects the brain to the spinal cord.it controls basic life functions, such as heartbeat, vomiting, swallowing and coughing etc,
iii:- The spinal Cord
The vertebral column consists of vertebrae and the spinal cord. The spinal cord is a bundles-of neurons like a rope. Its length may be different according to the height of man. It connects the brain to the nervous that is found throughout the body.
The Peripheral Nervous System (PNS)
The peripheral nervous system (PNS) is the collection of nerves that connects the Central Nervous System(CNS) to all your organ systems.
Includes 12 pairs and 31 pairs of cranial nerves and spinal nerves.More than two axons that are both sensory and motor neurons that nerve and get the most information in the CNS. In general, the PNS is made up of a sensory system and motor system. The sensory nerves system stores information about the body and its surroundings. The motor nerves system triggers voluntary and involuntary responses within the body.
a. Somatic Nervous System
This movement is the type of PNS that regulates all of which you have voluntary control over. This target connects the CNS.
b. Autonomic Nervous System
This is the type of PNS that controls autonomic functions, that you do not have to think about. For example, unneeded muscles help your gut digest food.it through your intestines.
Autonomic nervous system is important in maintaining homeostasis.It takes message from hypothalamus to organs about respiration, excretion, heart beat etc.
Within autonomic nervous system there are two sub types, the sympathetic nervous system and the parasympathetic nervous system.
c. Sympathetic Nervous System
This is the system that prepares the body for action and stress. When you become frightened or you are preparing for fight or flight your sympathetic nervous system is stimulated.
When blood vessels going to the skin and internal organs contract, it reduces blood flow to these areas Meanwhile, blood vessels going to the heart, brains, lungs and skeletal muscles expansion, increased blood supply to those areas.
Heartbeat rate increases, enlarges, and breathing becomes more efficient. These changes improve one's physical abilities and allow him/her to think and respond quickly.
Parasympathetic Nervous System
This is the sub type of the autonomic nervous system that works opposite to the sympathetic nervous system and calms to body.it normalizes the changes caused by the sympathetic nervous system.It helps the body to conserve energy which is done by lowering blood pressure and heartbeat rate. When the body finds comfort,it is activated.
Neurons and Their Types
As you have read earlier in this unit that our brain have more than 100 billion neurons. You can easily guess that the neuron is the smallest structural and functional unit. A neuron consists of two parts, cell body and axon.
The cell body is thicker region of the neuron containing the nucleus and most of the cytoplasm.There are thread-like projections on the cell body of neuron is called dendrites.
The axon is a long projection,that carries impulses away from the cell body,usually a neuron has a single axon.
Fatty substances covering the axon form myelin sheath along with short regions of exposed axon known as nodes of Ranvier.
Types of Neurons
Neurons are of three types.
- Sensory neurons
- Associative Neurons
- Motor neurones
i:- Sensory neurons
They carry nerve impulses (stimulus) from receptors to CNS.
ii:- Associative neurons
They form CNS and are responsible for analyzing the message and issuing orders.
iii.Motor neurons
Carry nerve impulse (orders) from CNS to effectors (muscles)
Working of Nervous System
The inter-neurons of the brain and spinal cord are arranged in a particular way. All of the axons of these neurons clustered together. The accumulation of neuron cell bodies is called ganglion and it is dark gray.
The collection of axon is called nerve because the myelin sheath on axon gives them a white appearance. In the brain, grey matter is on the outside, and the white matter is on the inside.
Grey matter forms an inner butterfly shaped area.
Although movement is controlled by your cerebrum and cerebellum, your brain depends on your spinal cord to deliver message to the proper muscles. When you're brushing your teeth and you want to move your arms, the brain sends an impulse down the spinal cord.
The impulse is directed by an inter neuron to the motor neuron that connects to the arm muscles. The motor neuron then carries the impulse to receptors in the arm muscles. When the receptors are continuously dynamic,your arm moves.
