L02: the nervous system (overall structure)

Question 1

behaviour

Answer 1

an organisms internally coordinated response to its internal and external environment

Question 2

what does it take for an organism to behave?

Answer 2

1. register/sense information from the environment, eg. birds planning flight routes using magnetic fields
2. result in an internal change (transform/process the information) eg. counterexample of anaesthesia blocking the senses
3. generate an appropriate response eg. counterexample of paralysis (internal change sensed, but unable to move in response), aphasia (language affected temporarily)

Question 3

single cell organism

Answer 3

organism floating in water

registration: molecule attaches itself to the cell membrane

transformation: triggers chemical change at the membrane that leads to a cascade of chemical changes inside the cell

response: resulting directly in a particular behaviour eg. change of membrane proteins = change in direction towards more food

single cascade

Question 4

complex organism

Answer 4

sense of smell

registration: molecule attaches itself to the cell membrane of a specific receptor cell

transformation: triggers chemical changes in other (nerve) cells that complex organisms are connected to, generating a nerve impulse. this is transmitted along specific neural pathways

response: resulting in activation of output systems (eg. execution of a movement)

cascade of communication

Question 5

the appropriate response

Answer 5

1. power grip for a hammer vs the precision grip for a nail
   • motor signal adapted without conscious thought
   • leaves us free to direct our attention elsewhere
2. adhd vs muscle tone
   • complex behaviour needs constant monitoring of the behaviour itself and the changes caused by it
   • registering of movement is impaired, so less attention is given to the outside environment

Question 6

complex plant behaviour

Answer 6

phototropism - plant grows (appropriate response) towards the sun (environmental stimuli) without a nervous system

Question 7

complex animal behaviour

Answer 7

animals have a variety of appropriate response options to choose from based on complex stimuli

eg. a gopher hearing birds chirping vs a chainsaw outside

therefore, we only need a nervous system to interact flexibly with the environment

Question 8

sponges

Answer 8

the only multicellular animals without NS

they just filter food particles passively

all other animals have a NS

Question 9

nervous system

Answer 9

a nervous system is a network of electro-chemically active cells (neurons) specialised to communicate with each other.

the activity of one cell causes a corresponding change in the next

Question 10

neuron firing

Answer 10

if the chemical change in neuron 1 is strong enough then a signal fires (active neuron).

then there is a change in next neuron to change its internal chemical state to be active.

signal transmission goes down the axon to the next cell body

Question 11

NS of invertebrates

Answer 11

animals with no spines

• simplest form of nervous system is the uncentralised nervous system
  
  • hydra/seastar
    have evenly spread out neurone networks
• no nerve cell control centre that controls other neurones or body parts
  
  • they have no brains!

Question 12

NS of vertebrates

Answer 12

animals with spines

• even structurally simple animals have centralised nervous systems
  
  • flatworm, leech, insect have separate CNS (’protobrain’ & nerve cord) & PNS
  • tightly packed cluster of nerve cells near the head area called ‘nerve cords’ - resembles a brain
  • scattered neurones are loosely connected in the body

Question 13

ventral and dorsal

Answer 13

‘ventral’ = towards the belly
‘dorsal’ = towards the back

Question 14

comparatively to invertebrates, vertebrates…

Answer 14

• vertebrates CNS and PNS is more separated (CNS controls the PNS more intensely, PNS is less pronounced)
• vertebrate brain is specialised to organise and direct communication between neurones
• vertebrate brain can control actions of body parts

Question 15

central nervous system

Answer 15

brain and spinal cord (dorsal), encased in bones

Question 16

peripheral nervous system

Answer 16

the nervous system for all other neurones

it transmits messages via neurons (nerve cells) to and from the CNS. it has 2 divisions: somatic and autonomic nervous system

somatic & autonomic nervous system

Question 17

somatic nervous system

Answer 17

• controls voluntary movements and is under conscious control
• picks up sensory information from the environment eg. touch, sight, hearing
• connects the senses with the CNS and has sensory pathways AND motor pathways
• controls skeletal muscles but is controlled by the motor cortex.

Question 18

autonomic nervous system

Answer 18

• no external input, receives input only from the CNS
• controls involuntary movement, not under conscious control
• ONLY has motor pathways
• controls smooth muscles + the internal organs and glands of the body but is controlled by the brain stem

> has the sympathetic and parasympathetic nervous system

Question 19

sympathetic & parasympathetic nervous systems

Answer 19

sympathetic is activated when a person is stressed: heart rate + breathing increase, digestion stops, salivation reduces, pupils dilate, flow of blood is diverted from the surface on the skin (fight or flight response)

parasympathetic is activated when the body relaxes and conserves energy: opposite to symp. (rest and maintenance)