Today we will start with the Nervous System. Simply stated, the nervous system is the super computer and network of system cables that control the entire body.
The nervous system is divided into two basic systems: the central and peripheral nervous systems
Central Nervous System
The central nervous system is composed of two parts: the brain and the spinal cord. Today we will confine our overview to the brain and will continue on this topic next week.
- Brain – The human brain is about the size of grapefruit and weighs around 3 pounds. There are about 100 billion nerve cells or neurons in the brain along with trillions of support cells known as glia.
The brain has a protective mechanism known as the blood-brain barrier. This barrier acts as a filter and controls the passage of harmful chemical substances and microscopic particles. However, it allows those substances responsible for metabolism, for example, oxygen to pass through. Due to the blood-brain barrier, the brain is protected from many infections that enter the rest of the body.
Gross Anatomy of the Brain
1. Cerebrum – The cerebrum is also known as the cortex or cerebral cortex. It is the outer wrinkled layer that one sees when observing the brain. The cerebrum is the largest part of the brain and accounts for nearly two-thirds of the total weight of the brain. It consists of an outer layer of grey matter composed mostly of neurons (nerve cells) and an inner layer of white matter composed mostly of axons or nerve fibers that transmit the signals from the neurons. The cerebrum also contains the two cortical hemispheres. The left hemisphere controls language and speech and the right hemisphere handles vision and spatial signals.
2. Cerebellum – Sometimes referred to as the ‘little brain’ the cerebellum contains over half the neurons found in the brain. It is located under and to the rear of the cerebrum and above the medulla. It manages and regulates the coordination of movements and sensory input.
3. Brainstem – The brainstem is divided into 4 sections:
A. Diencephalon – Located between the cerebral hemispheres and above the midbrain. The diencephalon contains the thalamus, hypothalamus, posterior pituitary gland, pineal gland, optic tracts and chiasma. It in involved in many facial functions and sensations including smelling, tasting, hearing, eye movement, equilibrium, chewing, salivating and swallowing.
B. Midbrain – Located between forebrain and hindbrain (see below). The primary role of the midbrain is control of the muscles involved in eye movement, pupil dilation and the shape of the lens.
C. Pons – Located below the cerebellum and above the medulla connecting the two. Contains the 5th, 6th, 7th, and 8th cranial nerves and serves to control facial and eye movements.
D. Medulla – Also called the medulla oblongata is the lowest section of the brainstem. Contains the 9th, 10th, 11th and 12th cranial nerves and serves to manage the heart and lungs.
There are several different ways of dividing the brain into functioning areas. The most obvious division is the right and left hemispheres that are connected by the corpus callosum. Another division of the brain is based on the four lobes of the brain: the frontal, parietal, temporal and occipital. A third division divides the brain into three sections: the forebrain, midbrain and hindbrain. Due to the different methods of division, I will attempt to give a brief overview of each of the three and their various subdivisions.
1. Hemispheres –
A. Right Hemisphere – The right hemisphere controls the left side of the body and is generally associated with the processing of information from the world around you. The right side is also associated with emotions. People who are right hemisphere dominant are left handed.
B. Left Hemisphere – The left hemisphere of the brain controls the right side of the body and deals with speech and the language. People with left side injury or stroke often lose the ability to talk. The left hemisphere is also associated with logic and detail. People who are left side dominate are right handed.
C. Corpus Callosum – Also known as the colossal commissure, the corpus callosum is a flat, wide nerve bundle that connects the left and right hemispheres of the brain, allowing for the exchange of cognitive thinking, along with sensory and motor skill information.
2. Lobes –
A. Frontal Lobe – As the name implies, the frontal lobe consists of the front portion of the brain. The frontal lobe is the center of dopamine activity which is associated with such functions as short term memory, positive and rewarding feeling, scheduling and drive. It is also the center of cognitive thought where one contemplates the future consequences resulting from current situations.
B. Parietal Lobe – The parietal lobe is located on the upper side of the brain just behind the frontal lobe. It is involved in spatial vision perception, processing of numbers and objects.
C. Temporal Lobe – The temporal lobe is located directly underneath the parietal lobe and behind the frontal lobe. The temporal lobe is involved with hearing, speech and vision as well as the ability to process the semantics of speech and form long term memory. Within the temporal lobe is the hippocampus, a region of the brain that controls both short and long term memory as well as spatial navigation. Located at the central base of the temporal lobe is the thalamus and hypothalamus. The thalamus is associated with both the states of being awake and asleep. The hypothalamus serves as a link between the nervous and endocrine systems and is closely involved with the pituitary gland. This not only involves the release of pituitary hormones but is also associated with the autonomic nervous system which includes such things as heart rate, blood pressure and body temperature.
D. Occipital Lobe – The occipital lobe is the very back portion of the brain and contains the primary visual cortex. Associated with the visual cortex is the ability to dream.
3. Fore – Mid – Hind
A. Forebrain – The forebrain is the largest of the three sections and consists of the uppermost part of the brain which includes the cerebrum, thalamus and hypothalamus.
a. Cerebrum – See above.
b. Thalamus – The thalamus is a section of grey matter located deep in the lower central region of the forebrain. Its primary functions include motor skills and sensory behavior,
c. Hypothalamus – Located within the thalamus, the hypothalamus basically controls the entire autonomic nervous system.
B. Midbrain – The midbrain is the upper most part of the brainstem which connects the rest of the brain to the stem. The midbrain contains the tectum and tegumentum.
a. Tectum – The tectum the upper layer of the midbrain and helps to control vision and auditory signals.
b. Tegumentum – The tegumentum is the descending portion of the midbrain and works with motor skills and has some connection with the autonomic nervous system
C. Hindbrain – The hindbrain is made up of the cerebellum, pons and medulla at the upper area of the spinal cord, which have all been described above.
The human brain is by far the most complex single structure that God created. With all of man’s technology, we have not even come close to designing or building anything nearly as complex as the human brain. The most powerful super computers fill rooms while the brain only fills the human skull. Super computers draw a tremendous amount of energy to operate and to keep cool. The amount of energy required to keep the human brain functioning and at just the right temperature isn’t enough to operate one lone desktop computer. Computers start to overheat and shut down at the temperature the brain operates at.
There is nothing known in the universe that compares to the human brain. It truly is a testimony to the infinite wisdom of our Creator God. He made man with a brain far superior to any other that He created on days 5 and 6 of Creation. He designed our brains to be able to know and understand Him and the world around us. Our brains are special because God purposely gave man knowledge and understanding as we read in Job 38:36:
Who has put wisdom in the inward parts
or given understanding to the mind?
While the brain’s primary physical function is to control the entire body, its primary mental function is to love the Lord your God as Jesus commanded in Matthew 22:37:
And he said to him, “You shall love the Lord your God with all your heart and with all your soul and with all your mind.”
Take a journey from conception to birth with Dr. David Menton, former professor of anatomy at the prestigious Washington University School of Medicine in St. Louis. Dr. Menton provides both a biblical and scientific answer to the question of when life begins.
Taken from one of Dr. Menton’s lectures, this video will reveal the wondrous design of the womb along with the numerous miracles involved along every step of the development of the unborn child.
Following the tragic starvation induced death of Terry Schiavo, Dr. Menton clearly shows the value and sanctity of human life.
With grace and sensitivity Dr. Menton concludes with a salvation message and explanation of the second birth process as described in John 3.