Structure and Function of the Central and Peripheral Nervous System - Example

Co-ordination By + 1 Structure and function of the central and peripheral nervous system The nervous system is responsible for the coordination of all the body activities through maintaining the normal function of the body and also responsible for making the body cope with emergency situations. The nervous system constitutes the central and the peripheral nervous system and is responsible for three main functions in the body; sensory functions, interpretation function and motor functions. The sensory function makes the system gather information from the body and the external environment and carry the information to CNS (Brodal, 2010). The sensory information brought to the CNS is processed and interpreted. Motor nerves then convers the interpreted information from the CNS to the muscles and the glands of the body (Brodal, 2010). The nervous system is divided into two; the nervous system that consist the brain and spinal cord and the peripheral system that connects the CNS to the rest of the body. The brain is a mass of nerve tissue that is contained within the skull. The brain is divided into cerebrum, cerebellum, cerebral cortex and the medulla. The cerebrum is the largest part of the brain with the function of being the centre of though and intelligence. The right part of cerebrum controls movement and activities on the left side of the body. The left side controls the functions of speech, smell, sight, memory, learning, sensory and motor functions. The cerebral cortex is located outside the cerebrum and functions in reasoning, learning and memory. Cerebellum lies below the cerebellum at the back of the skull. The part controls the body balance, the voluntary muscles and muscle tone. The medulla controls the rate of heart beat, breathing, coughing and swallowing. The medulla together with the pons forms the brainstem connecting cerebrum to the spinal cord. The spinal cord extends from the medulla down the vertebrate. The spinal cord acts as a message pathway between the brain and the rest of the body. Nerves transmission impulses from the brain which are referred to as efferent or motor nerves, move through the spinal cord to the several organs of the body. When the impulses reach the appropriate level they leave the cord to travel to the target organ. The peripheral system acts as a connection between the nervous system and the rest of the body. The peripheral system is divided into the nerves, the somatic nervous system and the autonomic nervous system. The nerves are made up of neurones that enable the travel of impulses from the centre where the activity in the body takes place to the CNS. The somatic nervous system allows the control of the skeletal muscle. The autonomic nervous system controls the automatic functions of the body such as digestion and resting. The messages in body travel from one neuron to the next across a synapse. Sensory neurons in the system carry messages from a receptor to the brain. Motor neurons then send the message to effector in the glands and muscles. Neurone is the basic unit of the nervous system. The cells are specialized to transmit messages faster from one part of the body to the other. The messages are transmitted through electric impulses. 1.2 Types and functions of neurons There are three types of neurons namely the sensory, the motor and the interneurons. Sensory neurons are characterised with long dendrites and a short axon. They are specialised in conveying messages from the sensory receptors in the body to the central nervous system. Motor neurons are characterised with along axon and short dendrites. Motor neurons are specialized to transmit messages from the central nervous system to the glands or to the nerves for the right actions after the message have been interpreted. The interneurons are those that send messages between the sensory neurons and the motor neurons in the central nervous system. 1.3 Reflex arc and a nerve impulse Reflex arc is the path that is followed by a nerve impulse from the periphery to the nervous system and then to the effector organs to correct the situation. Reflex arc is through stages and it takes place when a receptor detects a stimulus that is due to change in the environment. The sensory neurons then sends signal to the relay neurone for appropriate functions. The motor neurone then sends a signal to the effector which produces a response to the action. A nerve impulse is an electric signal that is sent and travel along an axon. The signal is sent through the difference that occurs between the inside of the axon and the surrounding. When there is activation of the nerve, there occurs a sudden change in the voltage across the wall of the axon which is caused by the movement of the ions in and out of the neurone. This triggers a wave of electrical activity that passes from the cell body along the length of the axon to the synapse. 1.4 Disorders of the central nervous system Disorders in the nervous system include vascular orders, structural disorders, infections, function disorders and degenerations. Neuroimunologic disorder is that caused when one experiences an inflammatory attack in the central nervous system. The disorder affects different parts of the central nervous system. When the disorder affects the spinal cord, it is referred to as transverse myelitis. When the optic nerve in the central nervous system is affected, the disorder is referred to as optic neuritis. In the condition, when the inflammation is in the spinal cord, the immune cells invade the spinal cord. The inflammation can be normal during situations such as infections or can be abnormal during autoimmune attacks. Stroke is also a threatening medical condition that occurs in situations when the supply of blood to the parts of the brain is cut. The disease needs faster attention since the more the condition occurs, the more damage it causes. The signs and symptoms are observed in the face, the arms and speech. The person with the condition will have the faces dropped on one side. The arms of the person are not able to lift anything and the speech of the person may be slurred and may not be able to talk despite being awake. 2.1 Hormones secreted by the endocrine glands The endocrine glands include the hypothalamus, the thalamus, testes, pituitary glands, pineal glands, ovaries, thyroid, adrenal glands, pancreases and parathyroid. The pituitary glands secrete growth hormones that are responsible for growth in children and maintenance of healthy bones and muscles in adults. Prolactin hormones are also secreted by the gland and are responsible for milk production in women (Klosterman, 2009). Adrenocorticotropic hormones by the gland promote production of cortisol which helps in reduction of stress and maintains blood pressure levels. Luteinizing hormones are produced by the gland are responsible for regulation of oestrogen in women and testosterone in male. Follicle stimulating hormone by the gland stimulates the release of eggs in women and ensures there is production of sperms in male. Oxytocin hormone is produced at the back of the pituitary gland and is responsible for contraction in pregnant women and maintains milk flow in nursing mothers. Antidiuretic hormone regulates water balance in the body (Klosterman, 2009). The hypothalamus acts as a control of pituitary hormones. Thymus is responsible for production of hormones that are referred to as humoral factors and are mainly utilized during puberty. Pineal glands secrete melatonin that is responsible in making the body recognize the time to go to sleep. Testes produces testosterone that is responsible for growth of the penis, hair and deepening on the voice in male (Klosterman, 2009). The hormone also helps in maintaining a sex drive, promotion of production of sperms and maintenance of healthy levels of muscles and bones. The ovaries produce oestrogen and progesterone that are responsible for development of breasts and maintenance of menstrual periods in female. Thyroid controls body metabolism (Klosterman, 2009). Adrenal glands control blood sugar level. 3.1 Structure and functions of the eye The eye contains the cornea. This is a transparent covering in the front part of the eye. It has no blood vessels and acts as the window in which light passes to the eye. Sclera in the eye acts as a protective coat of the eye. The iris in the eye is round with the pupil in the middle as an opening. The iris functions to contract and relax and changes the size of the pupil depending on light intensity. The lens is a crystalline structure in the eye that focuses light that enters the eye to the retina. The lens changes in shape depending on the closeness of vision. The aqueous and vitreous is a thin fluid situated between the lens and the cornea. It is responsible in giving the eye its shape and also nourishes the lens and the cornea. The vitreous is a thicker substance that is responsible for giving the inner eye its shape. The retina is a sensory tissue that lines the inner layer of the eye. It converts light rays that enter the eye into electrical impulses that are communicated to the brain (Davson, n.d.). It is made up of rods and cones that are responsible for transmission. Vision in the eye is created when light that enters the eye comes into contact with the cones and rods in the retina. The cones and rods convert the light into an electric impulse that is sent to the brain. This is through the optical nerve. 3.2 Visual perception in the eye Perception in the eye begins the time light is focused into the retina. The light is absorbed in the retina by a layer of photoreceptor cells. The cells are the responsible for converting the light into electrochemical signals which are grouped into cones and rods. The rod cells are responsible for vision at night and in dim light while the cones are responsible for high intensity light during the day (Davson, n.d.). Signals that are obtained from photoreceptors pass through the retina to ganglion cells that are in the third layer of the eye. The two retina layers enable detection of changes in the image. Ganglion cells the gather the information along other information and sends them to the brain through the optical nerve. The optical nerve routes information through the thalamus to the cerebral cortex where visual perception occurs. 3.3 Structure and function of the ear The ear is divided into three parts, the outer ear, the middle ear and the inner ear. The outer ear consist of pinna which is a made of cartilage and skin. The pinna is responsible for directing sound waves from the external environment into the external auditory canal. This directs the waves to the tympanic membrane making it vibrate (Fuchs, 2010). The tympanic membrane is thin membrane that separates the middle ear with the outré ear. The middle year is a space filled with air containing three tinny bones referred to as ossicles that are responsible in transmission of sound. The bones are malleus, incus and stapes. The middle ear is connected to the back of the nose through the Eustachian tube. The Eustachian tube is responsible for balancing the pressure that is the ear to that in the external environment. This prevents the bulging of the eardrum (Fuchs, 2010). The inner ear consists of the cochlea and the vestibular system. The cochlea is filled with fluid and contains several specialised sensory hair called cilia. This is the part of the ear responsible for hearing as it connects the ear to the brain. The vibrations are converted to signals that are sent to the brain in this part of the ear. The vestibular system consist the semi-circular canal, the saccule and the utricle (Fuchs, 2010). These are responsible for detection of movement rather than sound. They detect movement through the fluids that they contain. 3.4 Mechanism of perceiving sound by the ear The pinna collects sound and directs it to the ear canal. The sound is the sent to the ear drum. The eardrum will vibrate in response to the sound that is received. The malleus will then transfer the sound waves to the middle ear. The vibrations from malleus are sent to the anvil and then to the last bone. The vibrations get amplified in the middle year. The vibrations are sent to the cochlea from the three bones. When the sound is perceived in the cochlea, the vibrations are the transformed into electricity. The vibrations move the cilia in the cochlea that sends the signals to the spiral ganglia, the cranial nerve and then the impulses to the brain. The impulses are interpreted by the brain that brings about hearing. References Brodal, P. (2010). The central nervous system. New York: Oxford University Press. Davson, H. The eye. Fuchs, P. (2010). The ear. Oxford: Oxford University Press. Klosterman, L. (2009). Endocrine system. New York: Marshall Cavendish Benchmark. Nieuwenhuys, R., Voogd, J., & Huijzen, C. (2008). The human central nervous system. Berlin: Springer. Read More