Biology: Nervous System (free read in e-library)

Biology: Nervous System

 

HUMAN BRAIN

The brain is the most complex part of the human body. This three-pound organ is the seat of intelligence, interpreter of the senses, initiator of body movement, and controller of behavior.

 

The brain can be divided into three basic units: 

1. The forebrain, 
2. The midbrain, and 
3. The hindbrain

 

Forebrain - The forebrain is the largest and main thinking part of the brain. It has regions which receive sensory impulses from various receptors. Separate areas of the fore-brain are specialised for hearing, smell, sight and so on.

• Cerebrum

Midbrain - The Midbrain connects the forebrain to the hindbrain. 

• Hypothalamous

Hindbrain - The hindbrain controls the body’s vital functions such as respiration and heart rate.

• Pons
• Medulla
• Cerebellum

 

 

CEREBRUM :

• Largest part of the human brain.
• It sits at the topmost part of the brain. 
• It is the source of intellectual activities. 
• It holds your memories, allows you to plan, enables you to imagine and think. 
• It allows you to recognize friends, read books, and play games.
• It controls the voluntary motor actions.
• It is the seat of learning and memory.
• It is the site of sensory perceptions; like tactile and auditory perceptions.
• It is divided into two hemispheres; called cerebral hemispheres.
• It controls the voluntary actions and is the seat of intelligence.
• Its outer grey matter is the most important part.
•  

 

HYPOTHALAMUS: 

• It lies at the base of the cerebrum. 
• It controls sleep and wake cycle (circadian rhythm) of the body. 
• It also controls the urges for eating and drinking.
• It gets the adrenaline flowing during a test or job interview. 

 

CEREBELLUM:

• It lies below the cerebrum and at the back of the whole structure.
• It coordinates the motor functions. 
• It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.

• It is concerned with equilibrium of the body and co-ordination of muscles.

Example: When you are riding your bicycle; the perfect coordination between your pedaling and steering control is achieved by the cerebellum.

 

MEDULLA:

• It forms the brain stem; along with the pons. 
• It lies at the base of the brain and continues into the spinal cord. 
• It controls various involuntary functions 

Example : heart beat, respiration, size of the pupil, blood pressure, salivation and vomiting etc.

 

THALAMUS:

• a major clearinghouse for information going to and from the spinal cord and the cerebrum.

Cerebrospinal fluid (CSF) is a watery fluid that circulates through the brain’s ventricles (cavities or hollow spaces) and around the surface of the brain and spinal cord. 

Medulla Oblongata

• Lowest part of the brain and is connected with the spinal cord.
• It controls the involuntary actions.

 

Reflex Action

• It can be defined as the spontaneous response to the external stimuli.
• It is not co-ordinated by the brain but by the spinal cord.

 

Sense Organs

• There are several organs in the body that receive the external and internal stimuli and convey it to the brain and spinal cord.
• The main sense organs are Eye, Ear, Skin, Tongue, Nose, etc.

 

NEURON:

Neurons are the core components of the brain and spinal cord of the central nervous system (CNS).

Functions of the three parts of a neuron:

• Axon: It conducts messages away from the cell body.
• Dendrite: It receives information from axon of another cell and conducts the messages towards the cell body.
• Cell body: It contains nucleus, mitochondria, and other organelles. It is mainly concerned with the maintenance and growth.
  
  

 

SYNAPSE : It is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron.