control and regulatory system

• components of the nervous system

  the nervous system recieves, transmits and responds to information from the external environment and from the body's internal environment, through a collection of nerve cells.
• the central nervous system


  the central nervous system is the control centre for the body; it consists of the brain and spinal cord. the spinal cord connects the brain, by long lines of individual nerve cells, to every area in the body.
• spinal cord


  the spinal cord is protected by specialised bones named vertebrae. these bones have a hollow centre through which the spinal cord runs. it transmits information to and from the brain through structures called nerves.
• autonomic system


  the autonomic system controls and regulates processes such as heart rate and heart movements (prtistalsis). these actions are automatic - unconsciously controlled.
• sensory and motor neurons (somatic nervous system)


  sensory nerves transmit information from the senses - the eyes, ears, etc. - to the brain.

  motor nerves transmit information to the muscles from the brain.

  the sensory and motor nerve pathways work together, for example when picking up something, such as a pen
• peripheral nervous system


  all the nerves outside the central nervous system make up the peripheral nervous system. it relays information from the brain and spinal cord to the rest of the body, and the reverse infromation from the body to the brain and spina cord. peripheral nerves include autonomic, sensory and motor nerves.
• structure and function of the brain


  • cerebal cortex
  • cerebellum
  • frontal lobes
  • corpus callosum
  • hypothalamus
  • medulla
  • meninges
  • occipital lobe
  • pineal gland
  • spinal cord
  • pituitary gland
  • limbic lobe
• cerebal cortex


  the cerebal cortex is the winkly, outermost layer of the brain, responsible for thinking and processing sensory information from the body. these are four lobes, each resposnible for processing different types of information. it is made of tightly packed neurons.
• cerebellum


  positioned at the back of the skull, the cerebellum co-ordinates and regulates muscle acitivity, for example gross and fine motor skills such as walking and writing. it is also involved in the control of muscles to maintain balance.
• frontal lobes


  the frontal lobes carry out higher level mental processes such as thinking, decision making and planning.
• corpus callosum


  the corpus callosum is a bridge of nerve tissue that connects the two halves of the brain and enables communication between the two.
• hypothalamus


  the hypothalamus is responsible for the maintenance of body temperature. it also regulates apeptite and thirst, letting us know when we need to eat or have fluids.
• medulla


  the medulla automatically caries out and regulates life-sustaining functions such as breathing, swallowing and heart rate.
• meninges


  the meninges are three layers of the membranes surrounding the brain and the spinal cord. they provide a barrier from the rest of the body and act as protection from infection.
• structure and function of neuron

  • neuron
  • axon
  • dendron (dendrites)
  • myelin sheath
  • cell body
  • nucleus
  • nodes of ranvier
  • schwann's cells
  • axon terminal
• neuron


  neurons are specialised nerve cells that transmit electrical impluses (information) from one part of the body to another
• axon


  axons are the long thread-like part of a nerve cell, along which impulses are condcted away from the cell body to other cells. there is only one per neuron.
• dendron (dendrites)


  dendrons are short, branched structures on the neuron that recieve electrical impulses and carry them towads the cell body. these can be as many as 1000 per neuron.
• myelin sheath


  the myelin sheath is a fatty white substance that surronds the axon. it forms a protective, insulating layer and enables electrical impulses to transmit quickly and efficiently along the nerve cells.
• structure and function of a synapse


  information flows from one neuron to another across a synapse. the synapse has a small gap seperating neurons. the synapse consists of three elements:

  • the pre-synaptic membrane
  • the post-synaptic membrane
  • the gap between the two membranes, which is called the synaptic cleft
• function of a synapse


  the function of the synapse is to transfer electric activity (information) from one cell to another:

  • an electrcal impulse travels along the axon
  • this triggers the nerve-ending of a neuron to release chemical messengers called neurotransmitters
  • these chemicals diffuse across the synapse (the gap) and transmit signals
  • they bind with receptor molecules on the membrane of the next neuron
• organisation and function of the endocrine system


  the endocrine system is made up of glands that secrete hormones, sometimes called 'chemical messengers', that regulate metabolism, reproduction, growth and sleep.
• main parts of the endocrine system


  • pineal gland
  • pituitary gland
  • hypothalamus
  • thyriod
  • thymus
  • adrenal gland
  • pacreas
  • testes - male
  • ovaries - female
• pancreas


  the pancreas is a gland situated near the stomach that produces insulin. insluin is needed to control glucose (blood sugar) levels in the body.
• pituitary


  located at the base of the brain, the pituitary is the 'master glad' that regulates all the other endocrine glands.
• adrenal


  there are two adrenal glands, one on top of each kidney. they produce adrenaline, the 'fight-or-flight' hormone. this is released into the bloodstream as a response to threat and prepares the body to fight or run by raising the heart and breathing rates.
• thyroid


  located at the lower front part of the neck the thyroid produces thyroxine, which affects growth and sustains metabolism (how the body functions).
• ovaries and testes (reproductive glands)


  the ovaries and testes are the source of sex hormones.

  testosterone in males affects male characteristics such as sexual development, growth of facial hair and changes at puberty, as well as sperm production.

  in females the ovaries produce oestrogen and progesterone as well as eggs. these horomes control breast growth and reproductive functions such as mentruation and pregnancy.
• structure of kidney


  the components of the kidney are as follows:

  • cortex : the outer layer of the kidney.
  • medulla : the inner region, contains thousands of nephrons.
  • renal artery : supplies kidney with blood.
  • renal vein : carries blood filtered by the kidneys.
  • calyx : chambers through which urine passes.
  • ureters : tubes that carry urine from the kidney to the bladder.
  • bladder : stores urine.
  • urethra : urine passes out of the body through this.
• the kidney has two main functions, both carried out by the nephrons - the removal of urea (waste) and the maintenance of the balance of water levels.

  • the kidneys maintain the body's water balance (osmoregulation) by controlling the water concentration of blood plasma. this keeps water input from drinking fluids and water loss constant.
  • the kidneys also controlsalt levels and the excretion of urea. water that is not put back into the blood is excreted in urine.
  • nephrons consist of a ball formed of small capillaries, called a glomerulus, and a small tube called a renal tubule.
• structure of a kidney nephron

  • afferent arteriole
  • efferent arteriole
  • proximal convoluted tubule
  • capillaries
  • loop of henle
  • glomerulus
  • bowman's capsule
  • collecting duct
  • distal convoluted tubule
• • ultrafiltration is when metabolic wastes are seperated from the blood and urine is formed. it occurs in the glomerular capsule (bowman's capsule) in the nephron.
  • after filtration kidneys selectively reabsorb molecules that the body needs. these include: glucose; mineral ions (salts) reabsorbed in the proximal and distal tubules; and as much water as the body needs reabsorbed by the loop of henle.
• structure of the liver


  the liver is the largest internal organ and it carries out most chemical processes than any other organ in the body.

  it consists of:

  • inferior vena cava
  • aorta
  • gall bladder
  • common bile duct
  • hepatic artery
  • portal vein
• deamination


  • deamination occurs in the liver during protein metabolism (breakdown)
  • it results in the production of ammonia, which is a toxic waste
• detoxification


  • the liver converts the ammonia produced by the deamination into urea; this is still waste, but less toxic
  • the urea is transported in the blood and removed by the kidney in the urine
  • the liver breaks down alcohol, removing it from the blood
  • it also breaks down drugs such as paracetamol
• production of bile


  • bile is produced by the liver as a result of the breakdown of red blood cells
  • bile is stored in the gallbladder until needed by the digestive system
  • bile emulsifies fats during the digestive process
• homeostasis


  homeostasis is the maintenance of a constant internal environment. the conditions in the body must be carefully controlled if the body is to function effectively. the nervous system and hormones are responsible for this.
• examples of homeostasis


  • the concentration of carbon dioxide in the blood
  • body temperature maintained at 37°C; enzymes work best at this temperature
  • blood sugar levels, controlled by the release and storage of glucose, which in turn is controlled by insulin
  • water content, to protect cells by preventing much water entering or leaving
• negative feedback


  homeostasis control is achieved using negative feedback mechanisms:

  • if the level of something rises, control systems reduce it again
  • if the level of something falls, control systems raise it again