control and coordination - nerves Flashcards
how do animals increase their chance of survival
by responding to changes in their external environment
eg. by avoiding places that are too hot or too cold
what is a stimulus
a change in an animals surroundings
what is a response
a reaction to a stimulus (change)
what is the change in environment detected by
a receptor organ
what is the response brought about by
an effector organ
what links the receptor and effector
a coordination system (nervous system)
what is the order from a stimulus to a response
stimulus -> receptor -> sensory neurone -> relay neurone (CNS) -> motor neurone -> effector -> response
what is the role of any receptor
to detect the stimulus by changing energy into the electrical energy of nerve impulses
what is transduction
when energy is changed from one form into another
-> all receptors are transducers of energy
what is the receptor and effector organ of a ball being thrown at you
receptor: eyes
effector: muscles in hand
what is the receptor and effector organ of a bright light
receptor: eyes
effector: muscles in eyes contract (radial and circular muscles)
what is the receptor and effector organ of smelling food and becoming hungry
receptor: nose
effector: salivary gland releases saliva
what is the receptor and effector organ of dim light
receptor: eyes
effector: radial and circular muscles
what energy is being transduced when the receptor is eyes (retina)
light
what energy is being transduced when the receptor is ear (organ of hearing)
sound
what energy is being transduced when the receptor is ear (organ of balance)
kinetic
what energy is being transduced when the receptor is tongue (taste buds)
chemical
what energy is being transduced when the receptor is nose (organ of smell)
chemical
what energy is being transduced when the receptor is skin (touch/pressure/pain)
kinetic
what energy is being transduced when the receptor is skin (temp receptors)
heating
what energy is being transduced when the receptor is muscle (stretch receptors)
kinetic
what does the human nervous system consist of
- central nervous system (CNS) -> brain and spinal chord
- peripheral nervous system (PNS) -> all of the nerves in the body
what do impulses from receptors pass along
pass along nerves containing sensory neurones (nerve cells) until they reach the brain and spinal chord
how is information sent through the nervous system
as electrical impulses
what are electrical impulses
electrical signals that pass along neurones
what is a bundle of neurones known as
a nerve
what are the impulses that pass along a neurone a movement of
a movement of charged particles (ions) in and out of the neurone
where do nerves spread out to
spread out from the CNS to all other regions of the body and importantly, to all the sense organs
what do most neurones do
transmit impulses to muscles and glands
what does the CNS act as
a central coordinating centre for the impulses that come in from (or are sent out to) any part of the body
speed of impulses?
travel at speeds between 10 and 100 m/s
what are the three types of neurone
- sensory neurone
- relay neurone
- motor neurone
what is the cell body (of a general neurone)
where nucleus and main organelles are found
what is the axon
main long fibre of the neurone that carries impulses
what are dendrites
- these extend out of the cell body of the neurone and at the far end of the axon
- these fibres carry impulses and allow neurones to connect with lots of other neurones. forming a network for easy communications
- thus, forming junctions with each other, cell bodies or sensory receptors
what are synapses
- junctions between dendrons/dendrites/axon terminals
- allow impulse to pass across
what are nodes (of ranvier) and myelin sheath
- the axon is insulated by the fatty myelin sheath with small uninsulated sections along the length called nodes
- meaning the electrical impulses does not travel down the whole axon
- the impulse jumps from one gap (node of ranvier) to the next
- also allows nerve impulses to move quicker
adaptations of neurones
- long -> travel over large distances -> allows quick and accurate communication and response
- myelin sheath acts as an electrical insulator -> increases speed of transmission
- projections and divisions (dendrites) -> communication to other neurones/increase surface area
- gaps -> move quicker (nodes) -> instead of gradually moving through, can jump from one node to the next
- lots of mitochondria in nerve cells -> provide energy for synthesis of neurotransmitters (pass messages across synapse)
sensory neurone:
- carries an electrical impulse from the receptor to a relay neurone (CNS)
- cell body in middle of axon (branching off axon)
- receptor cells are present to detect stimuli (heat/touch/light)
- longer axon, longer dendrites, allowing greater connection
relay neurone:
- carries electrical impulse from sensory neurone to motor neurone
- part of CNS
- coordinates a response
- shorter, small cell body with dendrites branching off
motor neurone:
- carries electrical impulse from relay neurone to effector organ
-> brings about a response - cell body is at one end (nearest relay neurone)
- long axon (much longer than dendrites)
- dendrites branching off cell body
-> connects to lots of relay neurones
symptoms of someone with motor neurone disease (means motor neurones are not working correctly)
- loss of movement
- weakness
- slurred speech
- weakened grip
- tiredness
- muscle twitches
- trouble swallowing
