NERVOUS SYSTEM AND BEHAVIOUR

I showed simple information in the article [ NEUROLOGICAL BASIS OF BEHAVIOUR ] and I said I will complete in another article; in this article, I show simple information about the[ NERVOUS SYSTEM AND BEHAVIOUR ] and I will complete in another article because the article will be long and I appreciate the time of the readers.

Let’s discuss this important topic .

The nervous system can be divided into two main parts: 

1. The central nervous system.
2.  The peripheral nervous system.

1)- The central nervous system.

The CNS is made up of the brain and the spinal cord, and is responsible for processing, interpreting and storing messages, allowing the body to maintain homeostasis and respond to different stimuli. The brain and spinal cord are the two parts of the CNS.

The Brain

The coordinating and synthesizing part of the central nervous system (CNS) is the brain.

The brain of a human is divided into several main areas:

• A)-The cerebrum – the largest part of the brain, responsible for the highest kinds of mental activity as well as voluntary muscle control, interpretation of sensations, reasoning, learning and memory.  In other words, the thinking part of the brain.
• B)-The cerebellum – governs the co-ordination, adjustment and the smoothing out of movement.
• C)-The olfactory bulb – concerned with the sense of smell, which is the only sense that communicates directly the centre of emotions, the amygdala. This means that the sense of smell is closely associated with our emotions.

Definitions: Voluntary – Unforced or self-motivated. Receptor – A sensory nerve ending that responds to a particular kind of stimulus, found in the sense organs and on the skin.

Note In psychology, Emotion is also sometimes called Affect.

• D)-The thalamus – acts as a relay centre for neurons that link the spinal cord to the cerebrum. It has a twofold function:

o 1- It acts as a channel between the sense receptors (all except smell) and the cerebellum.

o 2- It plays a role in controlling the cycle of sleep and wakefulness.

• E)- The hypothalamus – includes the important pituitary gland, an endocrine gland whose hormones influence body growth, reproduction, lactation, and the water balance in the kidneys.  It also generally influences the activity of cells. Its role from a psychologist’s viewpoint might be summarised as:
• Controlling patterns of eating, drinking and sexual behaviour.
•  Homeostasis – An optimal level of organic function, usually maintained by a regulatory mechanism. (i.e. the maintenance of a healthy balance of temperature, heart rate and blood pressure).

. Hormonal activity

• G)-The medulla oblongata – also known as the brain stem.  It connects the brain with the spinal cord, and a number of the cranial nerves leave the brain at this point.  It contains a number of reflex centres which control the heartbeat, circulation, respiration, swallowing, and various digestive functions.

Other main parts of the brain

1)-The reticular system – a network of neural pathways throughout the central core which is connected to the sense receptors.  It acts as a filter for all incoming information and thus plays a role in our attention, awareness and arousal.

2)-The limbic system – a composite of structures which surround the central core. This system acts as a seat for our drives and emotions. It aids the hypothalamus in kerbing instinctive distress, and part of this system is also involved with memory capacity.

3)-The Spinal Cord

The spinal cord is a tissue mass inside the vertebral canal, protected by the bone of the vertebrae.  It also consists of:

• A)-Spinal nerves – 31 pairs of nerves originating from posterior and anterior roots on the spinal cord.
• B)-Spinal meninges – membranes covering the central nervous system in the spine.

The spinal cord is the continuation of the medulla oblongata and sends messages between the brain and part of the body.  The cord travels down the length of the spinal column protected inside the vertebrae.  It is divided into segments.  Each segment gives rise to a pair of spinal nerves which travel from the spinal cord into the body through spaces in the vertebrae. In the centre of the spinal cord there is a canal filled with fluid called the cerebrospinal fluid.  This fluid circulates up and down the spinal cord and into cavities of the brain. Impulses are transmitted from the tissues of the body to the brain along the spinal cord.

Reflex Actions

A reflex is an automatic (unlearned) response to a stimulus, caused by the reflex arc, the neural circuit that links the spinal to other parts of the body, permitting the body to quickly respond to stimuli.  A reflex action is the response of a motor neuron to a stimulus from a sensory neuron.  There are simple and complex reflex actions.  Simple ones occur in the spinal cord where the motor and sensory neurones join at the reflex arc.  With more complex reflexes, the stimulus is passed along to the brain which then sends out its own stimulus or message on what action to take.

The medulla oblongata has reflex centres which control the actions of the heart, expansion and contraction of blood vessels and such actions as swallowing, vomiting, coughing and sneezing.  The reflex centres in the cerebellum control movement and posture while those in the hypothalamus regulate temperature and the water balance.