Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

The  Nervous  System  

 
The  environment  around  an  organism  changes,  the  organism  is  able  to  detect  
those  changes  and  respond
...
 Al  living  things  respond  to  stimuli  such  as  light  and  chemicals
...
 Neurobiology  is  the  study  of  the  
structure  and  the  functioning  of  the  nervous  system
...
 
 
 

Components  of  the  Nervous  System  

 
Receptors  are  the  parts  of  the  nervous  system  that  detect  a  stimulus  and  initiate  
a  nerve  impulse
...
g
...
 
 
Nerve  impulses  are  carried  by  neurones  to  effectors,  which  are  either  muscles  or  
glands
...
 This  pathway  usually  involves  the  
central  nervous  system  -­‐  either  the  brain  or  the  spinal  cord  or  both
...
 These  sensory  and  motor  neurons  throughout  the  
body  make  up  the  peripheral  nervous  system,  PNS
...
 
 
Sometimes  a  very  rapid  response  to  a  stimulus  is  required,  for  example  if  you  
touch  something  that  causes  pain
...
 
 
The  reflex  arc  involves  the  rector  cells  in  your  finger,  a  sensory  neuron,  a  relay  
neuron  in  your  spinal  chord,  motor  neuron  and  the  effector
...
 These  
ascending  and  descending  neurons  carry  information  to  and  from  the  brain
...
 Information  is  gathered  by  sensory  receptors,  which  are  
able  to  absorb  different  types  of  energy  from  the  environment  and  transform  it  
into  nerve  impulses
...
 We  also  have  internal  chemoreceptors,  those  in  our  blood  vessels  
detect  the  pH  or  carbon  dioxide  concentration  of  our  blood  and  help  to  regulate  
our  breathing
...
 Some  respond  to  changes  in  blood  pressure,  others  to  the  movement  of  
fluid  in  the  inner  ear
...
 We  receive  this  information  from  
mechanoreceptors  known  as  stretch  receptors,  found  in  muscles
...
 
 

 
The  Human  Eye  

 
Photoreceptors  in  the  human  eye  make  it  very  efficient,  light  sensitive  organ
...
   
 
Two  types  of  light  receptor  cells,  arranged  in  single  layer  in  the  retina  are  called  
rods  and  cones
...
   
 
Rods  are  much  more  sensitive  to  light
...
 In  dim  light  only  rods  cause  impulses  to  be  
transmitted  along  the  optic  nerve  so  we  cannot  perceive  colour  and  the  world  
appears  in  shades  of  grey
...
 
These  cells  conduct  the  information  from  rods  and  cones  to  the  optic  nerve
...
 It  contains  the  highest  
concentration  of  cones  in  the  retina
...
 
 
Rods  
Cones  
Highly  sensitive  to  light,  work  in  dim  
Less  sensitive  to  light,  work  in  bright  
light
...
 

One  type  of  rod  can  respond  to  all  
wavelengths  of  light
...
 
Not  present  in  the  fovea
...
 
Each  cone  is  connected  to  it's  own  
bipolar  cell
...
 

 
At  the  point  where  neurons  leave  the  eye  in  the  optic  nerve,  they  pass  through  
the  layer  of  rods  and  cones,  and  this  creates  the  blind  spot
...
 However,  the  blind  spot  is  in  a  slightly  different  
position  in  each  eye,  which  means  each  eye  is  able  to  fill  the  gap  for  the  other  and  
we  are  not  aware  of  any  blank  areas  in  our  visual  field
...
 No  one  knows  exactly  what  other  animals  see  or  to  what  
extent  the  see  in  colour
...
 Colour  vision  and  perception  across  the  animal  kingdom  is  the  subject  
of  on  going  research
...
 Most  mammals  
have  weak  colour  vision;  humans  and  other  primates  have  the  most  advance  
colour  perception
...
 
 
Cats  have  three  types  of  cones,  but  a  much  lower  proportion  of  cones  to  rods  
than  humans
...
   
 
Many  animals  can  see  thing  that  we  cannot
...
 This  explains  why  very  few  wild  
flowers  are  coloured  red
...
 These  neurons  combine  impulses  from  groups  of  rods  or  from  
individual  cone  cells  and  they  generate  action  potentials  in  the  ganglion  cells
...
 Impulses  pass  to  the  thalamus  of  the  
brain
...
   
 
For  example,  because  of  the  way  light  rays  pass  the  retina  of  the  eye,  the  image  
falling  on  the  retina  is  both  inverted  and  reversed  from  left  to  right
...
 This  is  because  the  brain  interprets  
the  impulses  it  receives  so  that  we  can  see  the  world  the  right  way  up
...
 
 
 

Contralateral  Processing  
 
The  brain  must  also  coordinate  the  information  it  receives  from  both  eyes
...
   
 
Axons  from  the  regions  of  the  retina  closest  to  the  nose  in  each  eye  cross  over  to  
go  to  the  opposite  side  of  the  brain,  this  means  that  all  of  the  information  from  
the  left  visual  field  goes  to  the  right  visual  cortex  and  all  the  information  from  the  
right  visual  field  goes  to  the  left  visual  cortex
...
   
 
The  visual  cortex  assembles  all  of  the  information  it  receives  and  gives  us  an  
understanding  for  what  we're  looking  for
...
 The  pinna  is  a  sound  
collecting  device  and  in  many  animals  it  can  be  rotated  by  muscles  to  pick  up  
sounds  in  all  directions
...
 
 
 

How  sound  is  perceived  

 
Sound  is  created  by  differences  in  air  pressure,  which  produce  vibrations
...
 
These  movements  are  transmitted  to  three  tiny  bones  in  the  middle  ear
...
 Each  bone  vibrates  in  turn  so  that  vibrations  pass  via  the  bones  to  the  
oval  window
...
   
 
Vibrations  of  the  oval  window  are  passed  onto  the  fluid  contained  in  the  cochlea
...
   
 
Inside  the  cochlea  are  sensory  hair  cells  attached  to  membranes
...
 Different  
regions  of  the  cochlea  respond  to  different  frequencies  of  sound
...
 Hair  cells  in  any  one  region  vary  in  their  sensitivity  
and  this  allows  differences  in  loudness  to  be  detected
...
 If  the  sound  is  louder,  more  hair  cells  are  
stimulated  and  more  nerve  impulses  pass  to  the  brain
...
 
In  a  natural  environment,  two  types  of  animal  behaviour  can  be  recognised;  
innate,  instinctive  behaviours  and  learned  behaviours  that  occur  as  a  result  of  
experience
...
 This  behaviour  is  common  to  all  
members  of  a  species  and  is  genetically  controlled
...
   
 
Short-­‐lived  species  do  not  have  time  to  acquire  learned  behaviour  or  skills  and  a  
high  proportion  of  behaviour  of  most  invertebrates  in  innate
...
   
 
Learned  behaviour  on  the  other  hand  comes  from  every  day  experiences
...
 
 

Learning  can  develop  new  skills  or  change  existing  ones,  which  the  animals  will  
retain  in  their  memory
...
 
Primates,  big  cats,  wolves,  and  many  other  mammals  spend  a  long  time  with  
their  parents  learning  social  ad  hunting  skills  from  them
...
 Similarly,  many  monkeys  
and  apes  can  remember  where  a  particular  tree  will  be  fruiting  at  a  certain  time  
of  the  year  and  pass  on  this  knowledge  to  their  young
...
 
Primates  in  particular  show  the  ability  to  acquire  new  skills  that  help  them  to  
survive
...
 The  young  chimps  watch  other  
members  of  the  troop  and  then  try  to  copy  them
...
   
 
Many  animals  learn  from  experience  or  by  trial  and  error
...
   
 
Salivation  is  a  reflex  response  to  the  presence  of  food  in  the  mouth,  but  Pavlov  
noticed  that  his  experimental  dogs  began  to  release  saliva  before  they  started  to  
eat  and  he  decided  to  investigate  this
...
 After  repeating  his  experiment  several  times,  he  noticed  that  dogs  salivated  
as  soon  as  he  rang  the  bell
...
 He  called  this  modification  of  dog's  behaviour  conditioning
...
 
 
(2)  After  training,  the  dogs  responded  to  the  conditioned  stimulus  (the  sound  of  
bell)  and  produced  the  conditioned  response  (the  release  of  saliva  without  the  
appearance  of  food)
...
 
 
When  a  neurotransmitter  is  released  from  the  pre-­‐synaptic  membrane,  the  post-­‐
synaptic  membrane  is  depolarised  as  positive  ions  enter  the  cell  and  stimulate  an  
action  potential
...
 Some  pre-­‐synaptic  neurones  release  neurotransmitters  that  
inhibit  the  post-­‐synaptic  neuron  by  increasing  the  polarisation  of  the  membrane  
(hyperpolarisation)
...
 Post-­‐synaptic  transmission  is  therefore  inhibited  
at  these  inhibitory  synapses
...
 Some  post-­‐synaptic  neurons  are  stimulated  by  many  different  pre-­‐
synaptic  neurons,  some  excitatory  and  some  inhibitory
...
 The  neuron  may  receive  
more  stimulatory  impulses  overall  so  that  it  fires  an  action  potential,  or  it  may  
receive  mainly  inhibitory  impulses  so  that  it  does  not
...
 
 

Psychoactive  Drugs  

 
Psychoactive  drugs  are  chemical  substances  that  affect  the  way  that  the  brain  
transmits  impulses  at  synapses
...
 They  act  in  the  following  ways:  
 
(1)  Some  have  similar  structures  to  neurotransmitters,  and  so  either  block  
receptors,  preventing  a  response  or  have  the  same  effect  as  the  neurotransmitter  
but  are  not  removed  so  that  the  response  is  prolonged
...
 
 
(3)  Some  increase  the  release  of  neurotransmitters
...
 
 

Excitatory  Drugs  

 
Some  psychoactive  drugs  are  excitatory,  which  means  that  they  promote  the  
transmission  of  impulses,  and  excitatory  synapses,  or  inhibit  transmission  at  
inhibitory  synapses
...
   
 
Excitatory  drugs  
Mode  of  action    
Effects  
Nicotine  
(1)  Acts  at  synapses  that   (1)  Produces  feelings  of  
use  the  neurotransmitter   pleasure,  although  to  a  
acetylcholine
...
 
(2)  It's  not  broken  down   (2)  Strongly  addictive  
by  the  enzyme  
because  it  wears  off  
acetylcholine  esterase,  
quickly,  so  users  must  
which  breaks  down  
dose  themselves  
acetylcholine
...
   
post-­‐synaptic  membrane   (3)  Has  a  calming  effect  
as  acetylcholine
...
 
of  pleasure  and  
wellbeing
...
 
euphoria
...
 
by  blocking  its  return  to   (2)  Highly  addictive,  with  
the  pre-­‐synaptic  
users  seeking  to  maintain  
neurones
...
 
transmission  of  impulses   (3)  As  it  wears  off,  
in  reward  pathways,  
feelings  off  euphoria  turn  
giving  feelings  of  
into  depression  and  the  
pleasure  and  wellbeing
...
 
(4)  Prolonged  use  can  
cause  long  lasting  mental  
health  problems  such  as  
depression,  anxiety,  and  

Amphetamines  

   
 

delusions
...
 
of  energy  and  alertness
...
 
aggression  in  some  
(3)  Cause  the  release  of  
people
...
 
(4)  Increase  the  
concentration  of  
dopamine  present
...
 Examples  of  inhibitory  drugs  include  
alcohol,  THC,  and  benzodiazepines
...
 
membranes
...
 
stimulate
...
 
THC  (tetra  hydra  
(1)  Effects  receptors  in  
(1)  Induces  feelings  of  
cannabinol)  (the  most   cells  in  the  cerebellum  
relaxation,  and  effects  
important  psychoactive   and  cerebral  
coordination
...
 
anandamide
...
 
are  found  in  areas  of  the  
(3)  Causes  
brain  concerned  with  

Benzodiazepines  

hyperpolarisation  of  
post-­‐synaptic  
membranes,  so  that  they  
are  more  difficult  to  
stimulate
...
 
(2)  Causes  
hyperpolarisation  of  
post-­‐synaptic  
membranes  so  that  they  
are  more  difficult  to  
stimulate
...
   

(1)  Reduce  anxiety,  cause  
relaxation,  and  can  
induce  sleep
...
 

 
 

What  causes  addiction?  
 
Addiction  is  a  chemical  dependence  on  a  psychoactive  drug
...
 However,  three  factors  
seem  to  be  common  of  all  addictions,  whether  drugs  have  been  taken  for  
therapeutic  reasons  or  recreation:  
 
(1)  Social  factors  -­‐  pear  pressure  can  influence  young  people  to  experiment,  and  
drug-­‐taking  behaviour  can  be  associated  with  the  need  to  belong  to  a  group
...
 In  some  cultures,  cigarette  
smoking  is  freely  accepted  and  in  others  alcohol  is  used  to  celebrate  social  
events
...
 Users  of  
addictive  drugs  find  it  hard  to  give  them  up  because  of  the  feelings  of  wellbeing  
that  are  induced  by  dopamine
...
   
 
(3)  Genetic  predisposition  -­‐  relatively  few  people  become  addicted  to  drugs,  
although  many  are  exposed  to  them
...
 Research  on  
identical  twins  also  supports  this  view
...
   
 
 
 

The  structure  and  function  of  the  Brain  

 
The  brain  is  the  most  complex  organ  in  the  body
...
 Each  part  has  a  particular  
function,  regulating  some  automatic  processes  such  as  the  heartbeat  and  
balance,  and  controlling  our  speech  and  ability  to  reason
...
 These  regions  receive  information  from  the  sense  
organs,  and  coordinate  and  organise  motor  functions
...
 It  coordinates  the  
endocrine  and  nervous  systems  by  regulating  the  secretions  of  the  pituitary  
glands
...
 
 
The  medulla  obligata  (brain  stem)  controls  automatic  and  homeostatic  activities  
such  as  breathing,  swallowing,  digestion,  and  heart  rate
...
 
 
Functional  magnetic  resonance  imaging  (FMRI)  is  used  to  identify  which  part  of  
the  brain  controls  which  activity
...
 There  may  be  activities  in  an  area  of  the  brain  
associated  with  a  particular  task,  but  correlation  does  not  imply  cause
...
 
 
 

Sympathetic  and  Parasympathetic  Control  

 
The  peripheral  nervous  system  (PNS)  consists  of  all  the  nerves  that  do  not  form  
the  central  nervous  system  (brain  and  spinal  chord)
...
   
 
The  autonomic  nervous  system  is  subdivide  into  two  parts:  
 
(1)  The  sympathetic  nervous  system  
 
(2)  The  parasympathetic  nervous  system
...
   
 
The  sympathetic  nervous  system  causes  responses  that  are  important  in  an  
emergency,  this  so-­‐called  fight  or  flight  response
...
 
 
The  parasympathetic  system  controls  events  in  non-­‐urgent,  relaxed  situations,  
and  is  inhibitory  in  its  effects
...
 
pupil
...
   
that  more  blood  can  be  
pumped  to  the  muscles
...
 
restricted  as  blood  
vessels  constrict
...
 It  occurs  when  bright  light  shines  on  the  eye
...
 
 
Unlike  the  majority  of  reflexes,  it  is  controlled  by  the  brain,  instead  of  the  spinal  
chord
...
   
 
Motor  impulses  are  sent  from  the  medulla  obligata  to  the  muscles  of  the  iris
...
 
 
 
 

Brain  Death  

 
Life  support  machines  in  the  modern  hospital  can  take  over  the  roles  of  vital  
organs  such  as  the  heart  or  the  lungs  when  a  person  is  seriously  ill  or  injured  
from  an  accident
...
 The  patient  may  be  unconscious  or  in  a  coma  because  
of  damage  of  the  brain,  which  van  recover  in  time
...
 
 
The  legal  definition  of  brain  death  is  based  on  the  activity  of  the  brain  stem
...
   
 
Doctors  test  the  activity  of  the  brain  stem  to  determine  whether  to  continue  life  
support
...
 If  not,  the  patient  is  likely  to  be  considered  brain  dead,  however  a  
number  of  other  reflex  actions  such  as  eye  movement  and  blinking  are  always  
checked
...
 Impulses  are  carried  from  these  free  nerve  ends  to  the  sensory  
areas  of  the  cerebral  cortex,  where  messages  are  interpreted
...
   
 
Excessive  pain  can  be  un-­‐bearing  and  in  some  situations  the  pituitary  gland  
releases  endorphins,  which  are  neurotransmitters  with  pain  relieving  properties
...
 Morphine  and  heroin  mimic  
endorphins  and  bind  to  the  same  receptors
...
 
 
Immediately  after  a  road  accident,  a  person  may  feel  no  pain  and  may  sometimes  
be  able  to  move  themselves  away,  despite  serious  injuries
...
 
 
 
 

Studies  of  Behaviour  
Social  Organisation  

 
Social  organisation  is  a  feature  of  many  species  in  which  animals  live  together  in  
groups
...
 
 

Social  organisation  provides  protection  from  predators,  opportunities  for  
division  of  labour  among  the  group  and  support  for  finding  food
...
 No  
member  of  the  group  can  survive  without  others
...
 They  may  build  nests  in  hollow  trees  or  hives  provided  by  a  
beekeeper
...
 She  controls  the  activities  of  the  
colony  and  prevents  other  females  becoming  fertile
...
 
 
(2)  Drones  are  fertile  males  and  mate  with  virgin  queens
...
 They  live  
for  about  six  weeks
...
   
 
When  a  colony  becomes  too  large,  the  old  queen  leaves  the  nest,  followed  by  a  
number  of  workers
...
 A  new  queen  will  remain  behind  to  re-­‐establish  the  old  nest,  but  
worker  bees  drive  out  of  the  drones  at  the  end  of  the  season
...
 Instead,  natural  selection  acts  on  the  whole  colony
...
 These  may  
include  genes  that  promote  social  organisation,  or  care  of  the  young,  or  those  
that  produce  effective  controls  to  make  sure  that  workers  work  together
...
   
 
Altruistic  behaviour  may  decrease  the  individual's  chance  of  surviving  and  
reproduction,  but  increase  the  number  of  off  spring  produced  by  another  
individual
...
 Only  one  dominant  female,  the  queen,  reproduces
...
 Some  mole  rats  in  the  colony  act  as  workers,  
they  dig  tunnels,  gather  food,  and  build  the  nesting  chamber
...
 These  
guards  also  defend  the  colony  against  predators  such  as  snakes,  and  may  fight  to  
the  death  in  an  effort  to  prevent  a  colony  from  being  harmed
...
 
 
The  division  of  tasks  in  this  way  improves  the  chances  of  survival  and  passing  on  
genes  to  the  next  generation  for  all  the  members  of  the  colony
...
   
 
Evolution  favours  behaviour  that  increases  the  flow  of  alleles  to  the  next  
generation
...
 
 
 

Foraging  Behaviour  

 
Efficient  feeding  behaviour  is  essential  for  survival  and  reproduction,  but  in  
hunting  and  foraging  there  is  a  cost  in  terms  of  the  energy  needed  to  find,  catch,  
and  consume  food,  which  has  to  be  balanced  with  the  benefits  and  animal  gains  
of  the  food
...
   
 
The  blue  gill  sunfish  is  a  well-­‐studied  species  that  feeds  on  water  fleas  and  other  
small  pond  invertebrates
...
 When  food  is  abundant,  they  actively  select  only  the  
largest  flees
...
 If  the  density  of  food  is  
low,  the  fish  will  eat  whatever  they  can  rather  than  go  hungry
...
 
The  birds  probe  the  soil  and  extract  larvae
...
 However,  a  full  
beak  means  fewer  trips  back  to  the  nest
...
 The  
greater  the  distance,  the  larger  the  number  of  larvae  the  bird  carried  in  its  beak
...
 

In  the  1990s,  Marian  Petrie  studied  a  group  of  male  peacocks,  she  discovered  
that  females  not  only  preferred  males  with  long  tales,  but  also  selected  those  
with  more  eye  spots  on  their  tails
...
 Females  may  prefer  such  males,  
because  they  are  likely  to  produce  attractive  male  offspring,  or  because  an  
attractive  tale  is  a  sign  of  good  health
...
 However,  there  are  many  unanswered  
questions
...
 
 
Corals  have  many  reproductive  strategies  but  nearly  all  large  reef  building  
species  release  millions  of  gametes  once  a  year  in  a  perfectly  timed  manor
...
   
 
The  enormous  number  of  gametes  together  at  the  same  time  also  maximise  the  
chances  of  fertilisation  and  overwhelm  predators  with  more  food  than  they  can  
possibly  consume
...
 Some  animals,  such  as  red  deer,  have  animal  cycles  for  
reproduction
...
 The  winning  stag  gathers  and  mates  with  females
...
 The  
advantage  of  this  strategy  is  that  fresh  green  food  is  available  for  both  the  
mothers  and  for  the  young
...
 
 
Many  other  species  have  daily  patterns  of  activity,  e
...
 some  animals  forage  at  
night  and  sleep  during  the  da,  and  others  do  the  opposite
...
 It  feeds  on  seeds,  roots,  
and  vegetables,  and  has  a  good  sense  of  smell
...
   



---