bio csec

• Important hormones and their effects on the body


  • Growth hormone
  • Male and female reproductive hormones
  • Anti-diuretic hormone (ADH)
  • Thyroxine
  • Insulin
  • Glucagon
  • Adrenaline
  • Oestrogen
  • Progesterone
  • Testosterone
• Pituitary gland


  Sometimes called the master gland, controls the release of hormones by other endocrine glands
• Growth hormone


  • Regulates growth of the body
• Male and female reproductive hormones

  • Controls egg and sperm production
• Anti-diuretic hormone (ADH)


  • Controls the reabsorption of water in the kidneys, allows more water to be reabsorbed from the distal convoluted tubule and the collecting ducts
• Thyroxine


  • Controls the rate of chemical reactions in the body
  • Too little produced during childhood, person dwarf, mentally disabled
  • In adults too little causes body processes to slow down, less energy is needed from food, so people get fat, they will also feel tired and worn out and their faces may become swollen and puffy
  • Too much causes body processes to speed up, more energy is needed so the people become thin, they become excessively active, their eyes may bulge
• Insulin


  • Controls the amount of glucose in the blood if it is too high, cells take it up to carry out respiration, liver cells absorb excess glucose and convert it to glycogen (stored in liver and muscle cells), thus lowering the glucose level in the blood
  • If pancreas fails to produce insulin to lower the glucose content in the blood we say the person is diabetic, diabetics urinate more often and will be thirsty, because glucose is not being taken up by the cells and used the person will be tired and weak, also, be a decrease in mass as fat and protein (muscles) are burned to provide energy
• Glucagon


  • Produced when the blood glucose level falls below the normal level, causes liver cells to convert stored glycogen to glucose which is released into the blood stream thus raising the blood sugar level
• Adrenaline


  • The 'fight or flight hormone', prepares the body for emergencies, increases rate of heartbeat and breathing, causes glycogen to be converted into glucose in the liver and causes an increase in blood supply to the brain and muscles
• Oestrogen


  • Development of female secondary sexual characteristics and regulation of the menstrual cycle, causes repair of the uterus wall
• Progesterone


  • Causes the uterus wall to become thicker and fuller of blood vessels, maintains the uterus lining, prevents the uterus wall from breaking down during pregnancy
• Testosterone


  • Development of male secondary sexual characteristics, stimulates sperm production
• Homeostasis


  The maintenance of a constant internal environment despite changes in the external environment
• Feedback control or feedback mechanisms


  The processes by which the body brings about the 'steady state' and keeps conditions in the body within narrow limits
• Nervous system

  Brain and spinal cord
• Functions of the nervous system


  • Controls thinking, planning and learning
  • Allows us to interpret information from our senses (eye[sight], ear[hearing], nose[smelling], tongue[tasting], skin[touch] etc.)
  • Controls our instinctive reactions which allow us to react to danger by reflex actions
  • Controls the activities of all of our other systems, e.g. controls the movement of our limbs and the internal organs, and regulates our body temperature
• Sense organs


  • Eyes
  • Ears
  • Nose
  • Tongue
  • Skin
  • Mouth
• Sensory cells or receptors


  Special cells in the sense organs that pick up the stimulus
• What receptors do

  • Receive a specific stimulus (a change in the external or internal environment), the information in the form of tiny electric current (nerve impulse) is passed along nerves which may go to the brain, the brain interprets the nerve impulse and sends a message back down to the sense organ via nerves telling it to respond
• Events that take place when someone touches a hot pot or a pin is stuck in the paw

  1. Receptors/sensory nerve endings in the skin receive the stimulus

  2. Nerve impulse passes along the sensory neuron to neurons located in the spinal cord

  3. Neurons located in the spinal cord (relay neurons) receive the nerve impulses from the sensory neuron and passes the nerve impulse to the motor neuron

  4. Nerve impulses pass along the motor neuron from the spinal cord and goes to the muscles(effectors)

  5. The effector(muscles) which receives the nerve impulse contracts and the hand is lifted away from the hot pot or the pin stick
• Reflex action

  An immediate response to a stimulus
• Reflex action


  • When you touch a hot pot you immediately pull your hand away
• The nerve impulse goes from the sensory neurone to nerves (relay neurons) in your spinal cord and then to the motor neurones without going to the brain. This is called an involuntary (reflex) action
• Sometimes the impulse goes to the brain back down nerves to the spinal cord and motor neurone, in this case we become aware of what is going on and we experience pain
• How the nervous system receives and responds to a stimulus

  1. Receptors (sensory cells) receive the stimulus

  2. Message (nerve impulse) passes along a sensory neurone

  3. Nerve impulse may go to the brain or spinal cord

  4. Message travels along nerves to the brain where a decision is taken

  5. New message is sent back to the spinal cord and to the motor neurone instructing a response
• Voluntary actions involve the brain since we have conscious thought of it
• Neurone


  An individual cell that transmits impulses along its length
• Nerve


  Made up of hundreds of neurons
• Parts of the neurone


  • Cell body transmits impulses to the axon
  • Dendron transmits impulses towards the cell body
  • Axon transmits impulses away from the cell body to the target cell
  • Myelin sheath wraps around the axis of the axon resulting in faster nerve impulse conduction
  • Dendrite receives impulses (messages) from other neurons and passes the message to the cell body, then along the axon
• Synapse


  The gap or space between neurons
• How the nerve impulse travels from one neurone to the next

  1. Via a chemical substance

  2. Nerve impulse reaches vesicles containing chemical substance

  3. Vesicles migrate to cell membrane and release chemical across the synapse gap

  4. Chemical diffuses across gap and starts nerve impulse in next neurone
• Nerve impulses travel in one direction only due to the chemical substance being on one side of the synapse gap
• Differences between the endocrine system and nervous system

  • Endocrine system uses hormones, nervous system uses nerve impulses
  • Endocrine system transport is via blood, nervous system transport is via neurone membranes
  • Endocrine system is slow, nervous system is fast
  • Endocrine system has widespread effects, nervous system has localized effects
  • Endocrine system is stimulated by sense organs affecting glands, nervous system is stimulated by sense organs affecting neurone membranes
  • Endocrine system is mainly coordinated by pituitary gland, nervous system is coordinated by the brain
• Plants respond to stimuli differently to animals as they cannot move away, instead they produce hormones and chemicals to respond slowly
• Function of the brain


  • Receives information from sensory neurons, processes it, and passes it to effectors to respond
  • Stores information (memory/intelligence)
• Main regions of the brain

  • Cerebrum
  • Cerebellum
  • Medulla oblongata
• Function of the cerebrum


  Involved in memory, consciousness and intelligent actions. Certain regions are concerned with particular activities
• Function of the cerebellum


  Receives information on balance and posture, sends out impulses to maintain correct posture
• Function of the medulla oblongata


  Controls breathing, heartbeat, peristalsis, digestion, and body temperature. Responsible for involuntary actions
• Functions of the eye parts


  • Conjunctiva - thin membrane covering cornea
  • Cornea - refracts light, transparent
  • Aqueous humour - refracts light
  • Pupil - central hole in iris that light enters through
  • Iris - controls pupil size
  • Ciliary muscle - controls lens shape
  • Suspensory ligaments - attach lens to ciliary muscle, control lens shape
  • Lens - focuses light onto retina
  • Vitreous humour - maintains eyeball shape, refracts light
  • Retina - contains light sensitive cells that convert light to nerve impulses