brain

The human brain controls almost every aspect of the human body. This ranges from physiological functions to cognitive abilities. It receives signals and sends them to different body parts through neurons. The human brain structure is similar to those of other mammals, but it is the most developed.

LEARNING OBJECTIVES

By the end of this lesson, you should be able to:

• Describe the structure of the brain
• Explain the location of the brain
• Explain the various parts of the brain and their functions

The central organ of the nervous system of humans is the brain. The spinal cord together with the brain makes up the CNS (central nervous system). The brain is made up of the cerebrum, the cerebellum, and the brainstem. Most activities of the body are controlled by the brain. It is also responsible for coordinating information received from the sense organs and make decisions- these are the instructions sent to parts of the body. The brain is located in the skull bones of the head for protection. 

      

The average weight of an adult’s human brain is approximately between 1.0 kg- 1.5 Kgs. The brain is mainly made up of neurons. Neurons are the basic working units of the brain, specialized cells designed to transmit information to other nerve cells, muscle, or gland cells. Estimates suggest that the human brain has between 86 and 100 billion neurons. The brain is responsible for the control of body movements, thoughts, and interpretation.

LOCATION OF THE BRAIN

As we have already learned, the brain is enclosed in the skull. The skull is able to provide frontal, lateral as well as dorsal protection. The skull is made up of 22 bones. 14 bones make up the facial bones and the other 8 make up the cranial bones. The brain is found in the cranium and around it is the cerebrospinal fluid.

             

The (CSF) cerebrospinal fluid is a fluid circulating in the skull and the spinal cord. Every day, 500ml of cerebrospinal fluid is released by the specialized ependymal cells. The major function of this fluid is cushioning the brain from mechanical shocks. It also gives basic immunological protection to the brain. The brain is suspended in this fluid.

PARTS OF THE HUMAN BRAIN

               

Forebrain. This is the largest part of the brain. The following parts are contained in it:

• Cerebrum
• Hypothalamus
• Thalamus

The function of the forebrain is to control reproductive functions, emotions, sleep, hunger, and body temperature.

The largest part of the forebrain is the cerebrum. This part is also the largest of all vertebrate brains.

Midbrain. This is the smallest region of the brain. It is also the central part of the brain. The midbrain is made up of the following parts:

• Tectum
• Tegmentum

Hindbrain. This is the lower or hind part of the brain. It is made up of the following parts:

• Cerebellum
• Medulla
• Pons

The functions of the hindbrain include coordination of all survival processes like breathing, sleep, and heartbeat.

          

Cerebrum

This is the biggest part of the brain. It is made up of the cerebral cortex, and other subcortical structures. The cerebrum is made up of 2 cerebral hemispheres. These hemispheres are joined by the corpus callosum (heavy and dense bands of fiber). Upon further division of the cerebrum, it has four lobes or sections:

• Frontal lobe. This is associated with movements, parts of speech, reasoning, planning, and problem solving.
• Parietal lobe. It helps in movement.
• Occipital lobe. It is associated with visual processing.
• Temporal lobe. This is associated with speech, auditory stimuli, perception, and recognition of memory.

The brain is made up of two types of tissues: Grey and White matter.

• The grey matter normally has different types of cells that make up the bulk of the brain. It is a major component of the CNS (central nervous system). It consists of synapses, glial cells, neuropil, and neuronal cell bodies. You can distinguish between the white and grey matter as the grey matter has many cell bodies and fewer myelinated axons. The white matter has fewer cell bodies and is mainly made up of myelinated axons. Brain regions found in the grey matter are involved in: sensory perception like hearing and seeing, speech, muscle control, self-control, and decision making.
• The white matter. This is an area of the CNS that is mainly made up of myelinated axons. Its appearance is light due to the presence of a lipid called myelin. The white matter affects brain functions and learning, coordinating communication and acting as a relay, and controlling the distribution of action potentials.

The cerebellum functions include thinking, memory, consciousness, and intelligence.

Thalamus

This is a small structure that is found above the brain stem. Its function is to relay sensory information from the sense organs. It also transmits information for movement and coordination.

Hypothalamus

This is a small but essential part of the brain. It is located just below the thalamus. It is considered the brain’s primary region as it is involved in many functions. They include:

• Receiving impulses
• Regulating body temperatures
• Controlling emotions
• Controlling the senses of smell and taste
• Synthesis of essential hormones of the body
• Coordination of messages from the autonomous nervous system
• Control of appetite, blood pressure, peristalsis and the rate of heartbeat

Tectum

This is a small portion in the midbrain. It acts as a relay center for sensory information from the ears to the cerebrum. It is also responsible for the reflex movements of the eye, neck and head muscles. It provides passage for various neurons to and from the cerebrum.

Tegmentum

This is a region in the brainstem. It has different components that are involved in sleep, body movements, arousal and various necessary reflexes. It connects with the spinal cord, thalamus, and cerebral cortex.

Cerebellum

This is found in the posterior of the medulla and pons. It is the second-largest brain part. It has two hemispheres, the inner white medulla, and the outer grey cortex. Its main function is coordination and maintenance of body balance during running, riding, swimming, walking, and precision control of voluntary movements.

Medulla oblongata

This part mainly controls the autonomic functions of the body like digestion, breathing and heartbeat. It plays a vital role in connecting the spinal cord, the cerebral cortex and the pons. It also helps us maintain our posture and control our reflexes.

Pons

The main functions of pons include:

• Control of sleep cycles
• Regulation of respiration
• Transfer of information between the mortal cortex and the cerebellum.
• Involved in sensations like the senses of hearing, balance and taste.

Keynotes

• The central organ of the nervous system of humans is the brain
• The spinal cord together with the brain makes up the CNS (central nervous system)
• Most activities of the body are controlled by the brain