The Spinal Cord and its basic features
The spinal cord is a cylindrical structure that gradually tapers in the lower back region. The spinal cord is protected by the vertebral column, which is composed of individual vertebrae of the cervical , thoracic and lumbar regions and the fused vertebrae making up the sacral and coccyx portions of the column.
The internal structure of the spinal cord is much simpler and more uniform throughout its various parts than in that of the brain. No matter where it is sectioned, it presents the same essential appearance .
The principal function of the spinal cord is to distribute motor fibers to the effectors of the body (glands and muscles) and to collect somato sensory information to be passed on to the brain . The spinal cord also has a certain degree of autonomy from the brain as various reflex control circuits are located here.
One of the chief functions of the spinal cord is to conduct impulses to and from the brain . Although impulses enter and leave the brain through the cranial nerves, sensory impulses from all over the body except the head go to the brain through the spinal cord . The face and the neck is exercised by the brain. In the spinal cord are the conduction pathways proceeding upward and downward between the brain and the spinal nerves . In addition , the spinal cord serves as an integrating centre of its own and mediates reflex actions without much help from the brain .
In the spinal cord are the conduction pathways proceeding upward and downward between the brain and the spinal nerves . In addition , the spinal cord serves as an integrating centre of its own and mediates reflex actions without much help from the brain.
Neurons and their basic features
The neurons are the basic units of the nervous system.They are especially adapted to perform information processing functions.The four main parts of the neurons are :
1)The cell body which contains the nucleus of the nerve cell and its nutritional mechanisms.
2) Several dendrites which are usually short and the thick extensions of the cell body.The word dendrite is derived from the Greek word “ dendron “ which means “tree” as dendrites of a neuron look like trees .Dendrites help us to pick messages from other neurons and pass it on to the axon and terminal from where it travels to other neurons .
3) Axon is a thick, long extension of a nerve cell. The axons of most neurons are less than a millimeter long, but some peripheral neurons have axons or nerve fibers several feet in length. The axon is a long slender tube. It carries information away from the cell body down to the terminal buttons. Axons and their branches come in different shapes, as do dendrites.
4) Terminal Buttons:
The axon divides and branches a number of times .At the end of these extensions is found a little knob called the terminal button. These buttons have a very special function of transmitting the information to other cells. These terminal buttons secrete substances called neurotransmitters.
Neurons constitute about half the volume of the central nervous system. There are three principal types of neurons , classified according to the way their axons and dendrites leave the soma . These are unipolar, bipolar and multipolar.
Is memory a structure or a process ?
Human memory can be termed as episodic . There are two major theoretical approaches to episodic memory.
- Structure oriented : This approach to memory views information as passing from one memory system or store to another. Some may be lost or transformed from one form to another.
- Processing oriented : This approach to memory sees information as being transformed by the processing that subjects (people) apply to it . This processing can range from the shallowest kind in which only visual (graphic) characteristics are noted, to a deeper processing in which acoustic (phonemic) characteristics predominate to the deepest processing , in which meaning (semantic) characteristics are paramount .
The two approaches , structure and process , are similar in that each assumes some transformation or encoding of information . However , a structural approach emphasizes distinct systems or stores . These are often viewed as storage locations in the brain, each with its twin characteristics . A processing approach emphasizes the different process that subjects use to transform information . These are thought to be easily manipulated by instructions and sensitive to the different strategies that subjects employ in their efforts to remember.
The Brain and its basic features.The brain is the most important part of the central nervous system. The brain is usually divided into forebrain. midbrain, hindbrain.
The forebrain along with the neocortex (cerebral cortex) plays an important part in perception, sensation and co-ordination of behaviour patterns it also plays an important role in emotion, motivation, learning, language and thinking. The midbrain performs various functions like audition, vision and conduction of impulses within the nervous system. The hindbrain performs important functions like coordinated movements, sleep, and arousal and temperature regulation. It is also involved in the reception of visual, auditory, vestibular and somato sensory information. The reticular formation is an important structure of the brain. This structure is also called as the reticular activating system (R.A.S.) as it is related to sleep, arousal and attention.