B6 - Brain and Mind

B6 - NEW SYLLABUS

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THE NERVOUS SYSTEM

  • STIMULAS - A CHANGE IN THE ENVIRONMENT AROUND YOU.
  • ORGANISMS RESPOND TO STIMULI TO SURVIVE. A SINGLE CELL ORGANISM CAN JUST RESPOND TO ITS ENVIRONMENT, BUT THE CELLS OF MULTICELLULAR ORGANISMS NEED TO COMMUNICATE WITH EACH OTHER SO THE ORGANISM CAN RESPOND TO STIMULI.
  • WE HAVE EVOLVED TO DEVELOP NERVOUS AND HORMONAL COMMUNICATION SYSTEMS.
  • THE NERVOUS SYSTEM IS MADE UP OF:

1. CNS - (CENTRAL) IN VERTEBRATES THIS HAS THE SPINAL CORD AND BRAIN.

2. PNS - (PERIPHERAL) IN MAMMALS THIS IS WHAT THE CNS IS CONNECTED TO THE BODY WITH. IT IS MADE UP OF SENSORY, MOTOR AND RELAY NEURONES.

3. SENSORY NEURONES - THE NEURONES THAT CARRY IMPULSES FROM THE RECEPTORS TO THE CNS

4. MOTOR NEURONES - THE NEURONES THAT CARRY IMPULSES FROM THE CNS TO THE EFFECTORS.

5. RELAY NEURONES - ACT AS A LINK BETWEEN SENSORY AND MOTOR NEURONES.

6. EFFECTORS - MUSCLES AND GLANDS THAT RESPOND TO NERVE IMPULSES

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THE NERVOUS SYSTEM CONTINUED...

  • RECEPTORS - DETECT STIMULI. THERE ARE TASTE RECEPTORS ON THE TONGUE AND SOUND RECEPTORS IN EARS. RECEPTORS MAKE UP PART OF COMPLEX ORGANS LIKE THE LIGHT RECEPTORS IN THE EYES RETINA.
  • EFFECTORS - RESPOND TO NERVOUS IMPULSES & BRING ABOUT CHANGE. THE 2 TYPES OF EFFECTORS ARE THE MUSCLE CELLS & HORMONE SECRETING CELLS THAT ARE FOUND IN GLANDS
  • THE CNS IS THE PROCESSING CENTER AND COORDINATES RESPONSES ( COORDINATOR)

EXAMPLE 

A BIRD IS EATING SOME SEED WHEN OUT OF THE CORNER OF ITS EYE , IT SPOTS A CAT ( STIMULI). THE RECEPTORS IN THE BIRDS EYE STIMULATE THE SENSORY NEURONES WHICH CARRY INFORMATION FROM THE RECEPTORS TO THE CNS (COORDINATOR). THE CNS DECIDES WHAT TO DO ABOUT IT AND SENDS INFORMATION TO THE MUSCLES IN THE BIRDS WINGS (EFFECTORS) ALONG MOTOR NEURONES AND THE MUSCLES CONTRACT SO THE BIRD FLIES AWAY SAFETLY.

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NEURONES

(http://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Neuron1.jpg/220px-Neuron1.jpg)                             (http://encyclopediascience.files.wordpress.com/2011/05/sensory_neuron.gif)

                  MOTOR NEURONE                                                                              SENSORY NEURONE

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NEURONES AND SYNAPSES

  • NEURONES = NERVE CELLS. THEY TRANSMIT INFORMATION AROUND THE BODY  AS ELECTRICAL IMPULSES (THESE ARE SHORT LIVED SO THE RESPONSE IS FAST).
  • THE IMPULSES PASS ALONG THE AXON. THE AXON IS MADE UP OF THE NERVES CYTOPLASM STRETCHED OUT INTO A LONG FIBRE AND SURROUNDED BY A CELL MEMBRANE. THEY ARE SURROUNDED BY A FATTY SHEATH THAT ACTS AS A ELECTRICAL INSULATOR,
  • HORMONES (INSULIN & OESTROGEN) CARRY INFORMATION AROUND THE BODY - THEY'RE FORMED IN GLANDS AND TRAVEL IN THE BLOOD. THEIR RESPONSES ARE BROUGHT ABOUT MORE SLOWLY AND SO THEY LAST LONGER.
  • SYNAPSE = THE GAP BETWEEN 2 NEURONES. INFORMATION NEEDS TO BE TRANSMITTED ACROSS THE SYNASPE TO THE NEXT NEURONE AND IS DONE USING TRANSMITTER CHEMICALS:
  • WHEN AN ELECTRICAL IMPULSE REACHES THE END OF 1 NEURONE (PRESYNAPTIC CELL) IT TRIGGERS THE RELEASE OF NEUROTRANSMITTER CHEMICALS  FROM SYNAPTIC VESICALES INTO THE SYNAPSE CLEFT. THEY DIFFUSE ACROSS THE GAP AND BIND TO THE RECEPTOR MOLECULES ON THE MEMBRANE OF THE NEXT NEURONE (POSTSYNAPTIC CELL) TRIGGERING A NEW IMPULSE.
  • SOME DRUGS AND TOXINS AFFECT THE TRANSMISSION OF IMPULSES ACROSS THE SYNAPSE E.G. ECSTASY (MDMA) BLOCKS THE SITES IN THE BRAINS SYNAPSES WHERE THE CHEMICAL SEROTONIN IS ROMOVED. THE MOOD ENHANCING EFFECTS OF ECSTASY IS DUE TO THE INCREASED CONCENTRATION LEVELS OF SEROTONIN
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REFLEXES

  • REFLEXES ARE FAST, AUTOMATIC, PROTECTIVE BIOLOGICAL CONTROL SYSTEMS THAT LINK A STIMULAS TO A RESPONSE. THEY ARE INVOLUNTRY . THE ROUTETAKEN BY THE INFORMATION IN REFLEX IS CALLED S REFLEX ARC. 
  • THE REFLEX ARC GOES THROUGH THE CNS. THE ACTIONS ARE INVOLUNTRY BECAUSE THE RECEPTORS QUICKLY SEND IMPULSES ALONG THE SENSORY NEURONE TO THE CNS (USUALLY THE SPINAL CORD) WHICH THEN SENDS MESSAGES ALONG THE RELAYAND MOTOR NEURONES WHICH GO TO THE EFFECTOR AND YOU REACT BEFORE THE BRAIN PICKS UP THE MESSAGES.  NO INFORMATION IS EVER PROCESSED SO REFLEXES ARE RAPID.
  • SIMPLE REFLEXES INCREASE CHANCE OF SURVIVAL. E.G FINDING FOOD AND SHELTERING FROM PREDETORS
  • HUMANS HAVE THE KNEE JERK REFLEX, PUPIL DILATION, DROPPING HOT OBJECTS.
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LEARNING REFLEXES

  • REFLEX RESPONSES CAN BE MODIFIED BY THE BRAIN. IT CAN BE OVERRIDDEN BY A NEURONE BETWEEN THE BRAIN AND THE MOTOR NEURONE IF THE REFLEX ARC FOR EXAMPLE WE CAN HOLD A HOT DINNER PLATE WHEN WE WOULD NORMALLY DROP IT.
  • CONDITIONED REFLEXES EXAMPLE:

A Russian scientist called Pavlov trained dogs to expect food whenever he rang a bell. The dogs eventually produced saliva when they heard the bell ring.

  1. The dog salivates naturally when given food.
  2. Pavlov rings a bell every time the dog eats.
  3. After much repetition the dog salivates when the bell rings, even when there is no food.

This is an example of a conditioned reflex. The dogs were conditioned to salivate when the bell rang.

  • The food is called a primary stimulus.
  • The ringing bell is called a secondary stimulus.

When the ringing bell becomes a secondary stimulus, it does cause salivation, even though the dog will not be able to eat the bell as food. This is now called a conditioned reflex. In a conditioned reflex the final response (salivation) has no direct connection with the stimulus (ringing bell). Conditioned reflexes are useful because they increase an animal’s chances of survival. For example, birds will not eat caterpillars with bright colouring because they are conditioned to think of bright colours as poisonous. Some caterpillars have bright colours to protect them, even though they are not poisonous.

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LEARNING

  • NEURONS IN YOUR BRAIN ARE CONNECTED TOGETHER TO FORM PATHWAYS.
  • THE 1ST TIME A NERVE IMPULSE TRAVELS ALONG A CERTAIN PATHWAY NEW CONNECTIONS ARE MADE BETWEEN THE NEURONES. N
  • EW EXPERIENCES CREATE NEW PATHWAYS.
  •  IF SOMETHING IS REPEATED MORE NERVE IMPULSES FOLLOW THE NERVE PATHWAY. THIS STRENGHTENS THE PATHWAY.
  • STRENGHTENED CONNECTIONS MAKE IT EASIER FOR IMPULSES TO TRAVEL ALONG A PATHWAY.
  • THE OLDER YOU ARE THE HARDER IT IS TO LEARN.
  • YOU CAN LEARN BY VISULISING AND REPEATING
  • CHILDREN LEARN EXTREMELY EASILY UP TO THE AGE OF 8.
  • THE ENVIRONMENTAL STIMULI GOES ITO THE VISION, HEARING OR TOUCH STORES (SOME INFORMATION IS LOST) WHERE IT IS PROCESSED IN THE SHORT -  TERM MEMORY AND REHEARSED (SOME INFORMATION IS LOST) WHERE IS PROCESSED AGAIN AND REACHES THE LONG-TERM MEMORY

FERAL CHILDREN - 1799 SOUTHERN FRANCE  A BOY ACTED LIKE AN ANIMAL BUT LOOKED LIKE A HUMAN. HE COULDNT TALK. HE HAD LIVED IN THE WILD MOST OF HIS LIFE AND WAS ABOUT 12 YRS OLD AND NAMED VICTOR. HE WAS TAKEN TO PARIS AND THEY TRIED TO TEACH HIM TO SPEAK BUT HE NEVER LEARNT MORE THAN A FEW WORDS.

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MEMORY, THE BRAIN AND STUDY

  • MEMORY IS THE STORAGE AND RETRIEVAL OF INFORMATION. THERE IS SHORT-TERM THAT LASTS SECONDS AND LONG-TERM MEMORY THAT CAN LAST YEARS. STRONG STIMULI HELPS YOU REMEMBER THINGS.  
  • THE CEREBRAL CORTEX IS THE OUTER PART OF THE BRAIN
  • IT HAS A FOLDED STRUCTURE AND PLAYS IMPORTANT ROLES IN MEMORY , INTELLIGENCE, LANGUAGE AND CONSCIOUSNESS.

SCIENTISTS STUDY THE BRAIN BY:

1. STUDYING PATIENTS WITH BRAIN DAMAGE  E.G IF THE BCK OF THE BRAIN WAS DAMAGED BY A STROKE AND THE PATIENT WENT BLIND WE WOULD KNOW IT WAS RESPONSIBLE FOR VISION

2. ELECTRICALL STIMULATING THE BRAIN BY PUSHING ELECRODES INTO THE TISSUE AND OBSERVING WHAT EACH PART OF THE BRAIN DOES. 

3.  MRI SCANS - USED TO SEE ACTIVE PARTS OF THE BRAIN WHEN PEOPLE ARE DOING DIFFERENT ACTIVITIES 

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