Basic Psychology, Biology of Psychology

Peripheral Nervous System (PNS)

The peripheral nervous system (PNS)is the division of the nervous system containing all the nerves that lie outside of the central nervous system (CNS). The primary role of the PNS is to connect the CNS to the organs, limbs, and skin. These nerves extend from the central nervous system to the outermost areas of the body. The peripheral system allows the brain and spinal cord to receive and send information to other areas of the body, which allows us to react to stimuli in our environment.

The nerves that make up the peripheral nervous system are actually the axons or bundles of axons from neuron cells. In some cases, these nerves are very small but some nerve bundles are so large that they can be easily seen by the human eye.


The peripheral nervous system itself is divided into two parts:

  • The somatic nervous system
  • The autonomic nervous system

Each of these components plays a critical role in how the peripheral nervous system operates.


The Somatic Nervous System

The somatic system is the part of the peripheral nervous system responsible for carrying sensory and motor information to and from the central nervous system. The somatic nervous system derives its name from the Greek word soma, which means “body.”

The somatic system is responsible for transmitting sensory information as well as for voluntary movement. This system contains two major types of neurons:


  1. Sensory neurons (or afferent neurons) that carry information from the nerves to the central nervous system. It is these sensory neurons that allow us to take in sensory information and send it to the brain and spinal cord.
  2. Motor neurons (or efferent neurons) that carry information from the brain and spinal cord to muscle fibers throughout the body. These motor neurons allow us to take physical action in response to stimuli in the environment.


The Autonomic Nervous System

The autonomic system is the part of the peripheral nervous system responsible for regulating involuntary body functions, such as blood flow, heartbeat, digestion, and breathing. In other words, it is the autonomic system that controls aspects of the body that are usually not under voluntary control. This system allows these functions to take place without needing to consciously think about them happening.


This system is further divided into two branches:

  1. The sympathetic system regulates the flight-or-fight responses. This system prepares the body to expend energy and deal with potential threats in the environment. When action is needed, the sympathetic system will trigger a response by speeding up the heart rate, increasing breathing rate, increasing blood flow to muscles, activating sweat secretion, and dilating the pupils. This allows the body to respond quickly in situations that require immediate action. In some cases, we might stay and fight the threat, while in other cases we may instead flee from the danger.
  2. The parasympathetic system helps maintain normal body functions and conserve physical resources. Once a threat has passed, this system will slow the heart rate, slow breathing, reduce blood flow to muscles, and constrict the pupils. This allows us to return our bodies to a normal resting state.




Basic Psychology, Biology of Psychology

Human Brain

brain-structure1-300x190The most important and perhaps the most complex organ of human body is the brain. It controls all senses and functions of the body. Human brain weighs about 3 lbs. and is enclosed in a hard bony shell for protection, called skull. Interpreting information collected from different parts of the body and preparing the body for the generation of an appropriate response are some of the physiological tasks of the brain. Cerebrum, cerebellum, diencephalon and brainstem are the primary brain divisions.

For centuries, researchers and scientists have been trying their best to thoroughly explore the human brain structure, but until recently they have been unable to examine it completely and think it something very hard to accomplish. In fact, many of its functions still remain least understood, such as thinking.


The Cerebrum: Also known as the cerebral cortex, the cerebrum is the largest part of the human brain, and it is associated with higher brain function such as thought and action. Nerve cells make up the gray surface, which is a little thicker than our thumb. White nerve fibers beneath the surface carry signals between nerve cells in other parts of the brain and body. Its wrinkled surface increases the surface area, and is a six-layered structure found in mammals, called the neocortex. It is divided into four sections, called “lobes”. They are; the frontal lobe, the parietal lobe, the occipital lobe and the temporal lobe.

Functions Of The Lobes:

brain-lobes-300x194.jpgFrontal Lobe – The frontal lobe lies just beneath our forehead and is associated with our brain’s ability to reason, organize, plan, speak, move, make facial expressions, serial task, problem solve, control inhibition, spontaneity, initiate and self-regulate behaviors, pay attention, remember and control emotions.

Parietal Lobe – The parietal lobe is located at the upper rear of our brain, and controls our complex behaviors, including senses such as vision, touch, body awareness and spatial orientation. It plays important roles in integrating sensory information from various parts of our body, knowledge of numbers and their relations, and in the manipulation of objects. Portions are involved with our visuospatial processing, language comprehension, the ability to construct, body positioning and movement, neglect/inattention, left-right differentiation and self-awareness/insight.

Occipital Lobe – The occipital lobe is located at the back of our brain, and is associated with our visual processing, such as visual recognition, visual attention, spatial analysis (moving in a 3-D world) and visual perception of body language; such as postures, expressions and gestures.

Temporal Lobe – The temporal lobe is located near our ears, and is associated with processing our perception and recognition of auditory stimuli (including our ability to focus on one sound among many, like listening to one voice among many at a party), comprehending spoken language, verbal memory, visual memory and language production (including fluency and word-finding), general knowledge and autobiographical memories.

A deep furrow divides the cerebrum into two halves, known as the left and right hemispheres. And, while the two hemispheres look almost symmetrical, each side seems to function differently. The right hemisphere is considered our creative side, and the left hemisphere is considered our logical side. A bundle of axons, called the corpus callosum, connects the two hemispheres.

midbrain-300x292.jpgLimbic System – the limbic system is often referred to as our “emotional brain”, or ‘childish brain’. It is found buried within the cerebrum and contains the thalamus, hypothalamus, amygdala and hippocampus.

Thalamus – the primary role of the thalamus is to relay sensory information from other parts of the brain to the cerebral cortex

Hypothalamus – the primary role of the hypothalamus is to regulate various functions of the pituitary gland and endocrine activity, as well as somatic functions e.g.body temperature, sleep, appetite.

Amygdala – the primary role of the amygdala is to be a critical processor for the senses. Connected to the hippocampus, it plays a role in emotionally laden memories and contains a huge number of opiate receptor sites that are implicated in rage, fear and sexual feelings.

Hippocampus – the primary role of the hippocampus is memory forming, organizing and storing information. It is particularly important in forming new memories, and connecting emotions and senses, such as smell and sound, to memories.

The Diencephalon – The diencephalon is also known as the fore brain stem. It includes the thalamus and hypothalamus. The thalamus is where sensory and other impulses go and coalesce.The hypothalamus is a smaller part of the diencephalon

Pituitary Gland – the primary role of the pituitary gland is an important link between the nervous system and the endocrine system. It releases many hormones which affect growth, metabolism, sexual development and the reproduction system. It is connected to the hypothalamus and is about the size of a pea. It is located in the center of the skull, just behind the bridge of the nose.


The midbrain is located below the cerebral cortex, and above the hindbrain placing it near the center of the brain. It is comprised of the tectum, tegmentum, cerebral aqueduct, cerebral peduncles and several nuclei and fasciculi. The primary role of the midbrain is to act as a sort of relay station for our visual and auditory systems. Portions of the midbrain called the red nucleus and the substantia nigra are involved in the control of body movement, and contain a large number of dopamine-producing neurons. The degeneration of neurons in the substantia nigra is associated with Parkinson’s disease. The midbrain is the smallest region of the brain, and is located most centrally within the cranial cavity.


cerebellum-300x219.jpgThe Cerebellum – The cerebellum, or “little brain”, is similar to the cerebrum with its two hemispheres and highly folded surface. It is associated with regulation and coordination of movement, posture, balance and cardiac, respiratory and vasomotor centers.

Pons – The primary role of the pons is to serve as a bridge between various parts of the nervous system, including the cerebellum and cerebrum. Many important nerves that originate in the pons, such as the trigeminal nerve, responsible for feeling in the face, as well as controlling the muscles that are responsible for biting, chewing, and swallowing. It also contains the abducens nerve, which allows us to look from side to side and the vestibulocochlear nerve, which allows to hear. As part of the brainstem, a section of the lower pons stimulates and controls the intensity of breathing, while a section of the upper pons decreases the depth and frequency of breaths. The pons is also associated with the control of sleep cycles, and controls respiration and reflexes. It is located above the medulla, below the midbrain, and just in front of the cerebellum.

Medulla – The primary role of the medulla is regulating our involuntary life sustaining functions such as breathing, swallowing and heart rate. As part of the brain stem, it also helps transfer neural messages to and from the brain and spinal cord. It is located at the junction of the spinal cord and brain.

Brain Stem – The brain stem is located beneath the limbic system. It is responsible for vital life functions such as breathing, heartbeat, and blood pressure. The brain stem is made of the midbrain, pons, and medulla.


Basic Psychology, Biology of Psychology

Central Nervous System (CNS)

The central nervous system (CNS) is the processing center for the nervous system. It receives information from and sends information to the peripheral nervous system. The two main organs of the CNS are the brain and spinal cord. The brain processes and interprets sensory information sent from the spinal cord.

The central nervous system consists of the brain and spinal cord. It is referred to as “central” because it combines information from the entire body and coordinates activity across the whole organism.

  • The brain plays a central role in the control of most bodily functions, including awareness, movements, sensations, thoughts, speech, and memory. Some reflex movements can occur via spinal cord pathways without the participation of brain structures.
  • The spinal cord is connected to a section of the brain called the brainstem and runs through the spinal canal. Cranial nerves exit the brainstem. Nerve roots exit the spinal cord to both sides of the body. The spinal cord carries signals (messages) back and forth between the brain and the peripheral nerves.

Both the brain and spinal cord are protected by a three-layered covering of connective tissue called the meninges.The meninges are three layers or membranes that cover the brain and the spinal cord.  The outermost layer is the dura mater.  The middle layer is the arachnoid, and the innermost layer is the pia mater. The meninges offer protection to the brain and the spinal cord by acting as a barrier against bacteria and other microorganisms.

Within the central nervous system is a system of hollow cavities called ventricles. The network of linked cavities in the brain (cerebral ventricles) is continuous with the central canal of the spinal cord. The ventricles are filled with cerebrospinal fluid, which is produced by specialized epithelium located within the ventricles called the choroid plexus. Cerebrospinal fluid surrounds, cushions, and protects the brain and spinal cord from trauma. It also assists in the circulation of nutrients to the brain.


How does the central nervous system protect itself from injury?

The central nervous system is better protected than any other system or organ in the body. Its main line of defense is the bones of the skull and spinal column, which create a hard physical barrier to injury. A fluid-filled space below the bones, called the syrinx, provides shock absorbance.Unfortunately, this protection can be a double-edged sword. When an injury to the central nervous system occurs, the soft tissue of the brain and spinal cord swells, causing pressure because of the confined space. The swelling makes the injury worse unless it is rapidly relieved. Fractured bones can lead to further damage and the possibility of infection.

Why can’t the central nervous system repair itself after injury?

Many organs and tissues in the body can recover after injury without intervention. Unfortunately, some cells of the central nervous system are so specialized that they cannot divide and create new cells. As a result, recovery from a brain or spinal cord injury is much more difficult.The complexity of the central nervous system makes the formation of the right connections between brain and spinal cord cells very difficult. It is a huge challenge for scientists to recreate the central nervous system that existed before the injury.

Basic Psychology, Biology of Psychology

Nervous System

The nervous system is a complex network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body.

The nervous system includes both the Central nervous system and Peripheral nervous system. The Central nervous system is made up of the brain and spinal cord and The Peripheral nervous system is made up of the Somatic and the Autonomic nervous systems.Together, these organs are responsible for the control of the body and communication among its parts.


Nervous system is the chief controlling and coordinating system of the body. It controls and regulates all activities of the body, whether voluntary or involuntary, and adjusts the individual (organism) to the given surroundings. This is based on the special properties of sensitivity, conductivity and responsiveness of the nervous system.

human_nervous_system.jpgThe protoplasmic extensions of the nerve cells form the neural pathways called nerves. The nerves resemble the electricity wires. Like the electric current flowing through the wires, the impulses (sensory and motor) are conducted through the nerves.The sensory impulses are transmitted by the sensory (afferent) nerves from the periphery (skin, mucous membranes, muscles, tendons, joints, and special sense organs) to the central nervous system (CNS). The motor impulses are transmitted by the motor (efferent) nerves from the central nervous system to the periphery (muscles and glands).
Thus the CNS is kept continuously informed about the surroundings (environment) through various sensory impulses, both general and special. The CNS in turn brings about necessary adjustment of the body by issuing appropriate orders which arc passed on as motor impulses to the muscles, vessels, viscera and glands. The adjustment of the organism to the given surroundings is the most important function of the nervous system, without which it will not be possible for the organism to survive.


Functions of nervous system

Sensory Input

  • Receptors within and near body surface
  • Send nerve impulses to CNS


  • CNS receives, processes, and interprets sensory input
    Decides what to do with it.

Motor Output

  • CNS sends out nerve impulses to effector organs (muscles and glands) in response to sensory input.