nervous system A neurone is a nerve cell which is the basic functional unit of the nervous system The central nernous system consists of the brain and spinal cord The peripheral nervous system consists of cranial nerves and spinal nerves. The brain is an organ that is the centre of control and coordination in the nervous system The spinal cord controls reflex action The peripheral nervous system is the network of nerves which connect the central nervous system with other parts of the body. Cranial nerves composed of 12 pairs of nerves which orogonate from the brain and are connected to sense organs in the head and neck, and also to effectors such as the muscles or glands in the body cavity. Spinal nerves are composed of 31 pairs of nerves which originate from spinal cord and are connected to sense organs and effectors in the whole body including hands and legs.Neurones A neurone is a nerve cell.It is the basic functional unit of the nervous system The cell body contains many projections Dendrons - projections from the cytoplasm that point outward from the cell body Dendrites - smaller projections that branch from dendrons or axons Axons - another type of projection Dendrans and dendrites receive messages from other cells and trnasmit the message to the cell body Axons conduct messages away from the cell body Some axons in certain neurones are covered by myelin sheath.The sheath breaks up at intervals along the dendrons or axons.This enables impulses to jump from one node to another, shortening the time impulses travel along the surface of the axons or dendrons. Besides this, the meylin sheath is important because: It acts as an electrical insulator it is a source of food for axons and dendrons it also protects axons and dendrons from physical injury.Types of neurones There are three types of neurones sensory neurones motor neurones interneurones (relay neurones)

Nervous Coordination

Receptors and effectors Any changes which occur inside and outside of the human body are known asstimuli Receptors are sensory cells that detect and receive stimuli and turn them into electrical impulses Effectors are muscles or glands which produce responses due to stimuli.They respond to stimuli by: contraction gland secretion Figure above shows how the human nervous system works. Nerve Impulses are messages conveyed along the nerve in the form of weak electrical pulse An impulse moves only in one direction as shown in figure.

Impulses move in one direction

Reflex action A reflex action is a rapid,automatic unlearned response to a stimulus.This action is involuntary and cannot be controlled by the brain A reflex action does not require conscious thought or decision by the brain The components involved in a reflex action are: The receptors The effectors Sensory neurones Relay neurones Motor neuronesReflex arc A reflex arc is a sequence of pathways taken by the impulses from receptors to effectors in a reflex action The pathway of impulses in a reflex arc are as follow:

Pathway of impulses

Proprioceptors Proprioceptors are sense organs which are connected to sensory neurones.Humans are able to determine the position of their legs, arms, head and other parts, along with the orientation of the body as a whole with this type of receptors Proprioceptors are found in all skeletal muscles, tendons, ligaments and joints.They provide information to the brain regarding adjustment in posture and movement.Therefore, adjusments may be made to maintain body posture or to carry out a particular body movement.Kinaesthesis Kinaesthesis is the ability to sense the position, location, orientation and movement of the body and its part without looking at ourselves.

The Human Brain and Its Complexity

Structure of the brain

The human brain is the most complex organs in the human body.It is also the most complex brain among all mammals. The brain is the centre that contols and coordinates our responses as shown in above

The human brain has an external layer which is white in colour. The grey-coloured layer is made up of closely packed neurone cell bodies which form the grey matter of the brain The white-coloured layer is made up of nerve fibres which form the white matter of the brain The human brain can be divided into three main parts: Cerebrum Cerebellum Medulla oblongata

Human Brain

Cerebrum The cerebrum is the largest part of the human brain.It makes up about 80% of the mass of the human brain. The cerebrum can be divided into two hemispheres. Right hemisphere Left hemisphere Nerve impulses from the left side of the body will be received by the right hemisphere whereas nerve impulses from the right side of the body will be received by the left hemisphere Functions of the cerebrum are: It controls voluntary and highest intellectual functions such as thinking, learning and problem solving. It regulates emotion and memory through the limbic system. It controls human behavior. Receives and interpets impulses from sensory organsCerebellum The cerebellum is located below and behind the cerebrum The function of the cerebellum are: Controlling and maintaining posture and balance of the body Controlling and coordinating muscularactivities

Medulla oblongata Medulla oblongata is the lower most portion of the brain and is continuos with the spinal cord.It is the smallest component of the brain Medulla oblongata relays nerve signals between the brain and spinal cord. Medulla oblongata controlsn automatic functionsVoluntary and involuntary actions Human respond to a stimulus through voluntary actions and involuntary actions

Effect of injuries to specific parts of the human brain

Hormonal Coordination in the BodyHormones are chemicals secreted by endocrine glands.Hormone produced are secreted directly into the bloodstream and carried by blood to tissues or organs without the need of any ducts.They are usually secreted is small amounts The hormones have a specific effect only on the tissue or an organ designed to receive its message .This tissue or organ is called target tissueor target organ.This is because only this specifictissue or organ will respond to them. Important roles of hormones are: causing physical and physiological changes. Controlling the rate of body process Influencing growthThe endocrine system Chemical coordination involves the endocrine glands and their secretion Endocrine system consists of endocrine glands and their secretion Endocrine glands do not have ducts.Thus it is also called ductless glands.

Pituitary gland is located at the base of the brain just beneath the hypothalamus The anterior lobe regulates the activity of several glands.Among these are thyroid,adrenals and reproductive glands. It produces hormones such as: Corticotropin - stimulates the adrenal gland to produce certain hormones. Growth hormone - stimulates the growth of bones, muscles and other body organs.Plays a role in the handling of nutriens and minerals in the human body. Prolactin - promotes the development of glandular tissue in the female breast during pregnancy.Stimulates milk production in women who are breastfeeding. Thyrotropin - stimulates the thyroid gland to produce thyroxine hormones. The posterior lobe of the pituitary gland releases antidiuretic hormones (ADH).This hormone acts on the kidneys to regulate water content and write output.Oxytocin is also released by the posterior lobe.Oxytocin triggers the contraction of the uterus during labour.It also stimulates the ejection of milk from the lactating breast.

Thyroid gland The thyroid gland is located in the front of the lower neck. Hormone thyroxine produced by the thyroid gland has the following functions: Controls metabolic rate Controls skeletal growth Controls mental developmentPancreasPancreas produces two important hormones Insulin - insulin decreases blood glucose concentration by stimulating the conversion of glucose into glycogen in the liver. Glucagon - glucagon increases blood glucose concentration by stimulating the conversion of glycogen to glucose in the liver.Insulin and glucagon work together to maintain a steady level of glucose in the blood.This is important to produce and maintain stores of energy.

Adrenal gland is located on top of each kidney. The adrenal glands have two parts; the internal part is the adrenal cortex and the inner part is name adrenal medulla Adrenal cortex produces hormones called corticosteroids.Corticosteroids influence or regulate salt and water balance in the body, the body's response to stress,metanolism,the immune system and sexual development abd function. Adrenal medulla produces catecholamines such as adrenaline.Ovary are located in the female reproductive system Ovaries produce two groups of female sex hormones. Oestrogen Progesterone Oestrogen is involved in the development of secondary sexual characteristics in female such as: The development of breasts The accumulation of body fat aroundthe hips and thighs. Maturation of reproductive organs such as the uterus and vagina. Progesterone prepare the uterus lining for pregnancyTestis is located in the male reproductives system testis secretes hormones called androgens The most important androgen hormone is testosterone.

Coordination between the Nervous System and the Endocrine System The two types of coordination work together at certain times.The human digestive system is a good example.When food is served,the mouth will start to salivate and this response is coordinated by the nervous system.Gastrin a type of hormone is secreted when the half-digested food goes into the stomach.Gastrin causes the stomach wall to produce hydrochloric acid and other emzymes to carry out further digestion.

Effects of Drug Abuse on Body Coordination and Health

Definition of drugs Drugs are chemical or biological substances which affect the function of the nerveous system,especially the brain,causing changes in behaviour and personality.They change the way the body works.Types of drugs The four main types of drugs are: Stimulants Depressants Hallucinogens Opiates

Drug abuse is the misuse or overuse of any medication or drug Reasons of drug abuse include: use drugs because they are thrill-seekers use drugs out of curiosity or because their friends do it use drugs in order to cope with unpleasant emotions and difficulties in life

Effects of Excessive Consumption of Alcohol on Body Coordination and Health

Ethanol commonly known as alcohol is found in most alcoholic drinks.It is a strong psychoactive substance with a depressing effect. Ethanol is produced in a process call fermentation.Fermantation is a process that uses yeast or bacteria to change the glucose in the food into ethanol. Yeast + glucose > ethanol + carbon dioxide + energy

Effect of excessive consumption of alcohol on body coordination

Alcohol is a depressant.This means it slows down the function of the central nervous system. When alcohol is consumed, it is absorbed into the bloodstream rapidly and travels around the body to the brain.

Effect of excessive consumption Alcohol is broken down into acetaldehyde by the enzyme, alcohol dehydrogenase in the liver.The acetaldehyde is then broken down into acetic acid by the enzyme acetaldehyde dehydrogenase.Next acetic acid is converted into fats or carbon dioxide and water.Fatty acids build up as plaques in the capillaries around liver cells.Liver cells begin to die.This leads to the liver disease called cirrhosis.As we know the liver is damaged,certain toxins build up.This leads to sympthoms of jaundice. Foetal alcohol syndrome is another one consequence of excessive consumption of alcohol use. Foetal alcohol syndrome: a foetus is fed through the placenta inside the mother.Since alcohol passes easily through the placenta,the developing foetus gets a dose of alcohol when the mother drinks alcohol.