5.1.3 Neuronal Communication Flashcards
what is the nervous impulse made out of
- made up of a complex network of cells called neurones
- sends information as nerve impulses
what are nerve impulse
- electrical signals
- also called action potentials
- how the nervous system sends information
what are the three types of neurones
sensory
motor
relay
what are sensory neurones
transmit nerve impulses from receptors to the central nervous system CNS
what is the CNS made out of
the brain and spinal chord
what are motor neurones
transmit nerve impulses from the CNS to effectors
what are relay neurones
transmit nerve impulses between sensory neurones and motor neurones
what happens after a stimulus is detected by receptor cells
a nerve impulse is sent along a sensory neurone
what happens when a nerve impulse reaches the end of a neurone
- chemicals called neurotransmitters take information along to the next neurone, which then sends a nerve impulse
what does the CNS do
processes the information, decides what to do, and sends the information along a motor neurone to an effector
what is the process of seeing a stimulus to a response being formed
STIMULUS: seeing someone waving
RECEPTORS: light receptors in your eye detect the wave
→ sensory neurone
CNS: processes the information and decided what to do about it
→ motor neurone
EFFECTORS: muscle cells are stimulated
RESPONSE: muscles contract to make your arm wave
what is a transducer
something that converts one form of energy into another
how do sensory receptors act as transducers
- different stimuli have different forms of energy (e.g. light and chemical)
- your nervous system is only able to send information in the form of nerve impulses (electrical energy)
- so sensory receptors convert the energy of a stimulus into electrical energy
what happens in a nervous system receptor that is not being stimulated
- the receptor is in its resting state
- there’s a difference in charge between the inside and outside of the cell
- this is generated via ion pumps and ion channels
- this results in a voltage (potential difference) across the membrane
what is resting potential
the potential difference when a cell is at rest
what happens to a sensory receptor when a stimulus is detected
- the cell membrane is excited and becomes more permeable
- this allows more ions to move in and out of the cell
- this alters the potential difference (generator potential)
what is the generator potential
the change in potential difference due to a stimulus
what does a bigger stimulus cause in sensory receptors
- bigger stimulus
- excited the membrane more
- causes a bigger movement of ions
- and a bigger change in potential difference
- so a bigger generator potential is produced
what happens if a generator potential is big enough
- it will trigger an action potential (nerve impulse) along a neurone
when will an action potential only be triggered
if the generator potential reaches a certain level called the threshold level
- (if the stimulus is too weak, the generator potential won’t reach the threshold and there will be no action potential)
what are Pacinian corpuscles
mechanoreceptors, so detect mechanical stimuli
- e.g. pressure and vibrations
- found in your skin
- contain the end of a sensory neurone, called a sensory nerve ending
- the sensory nerve ending is wrapped around lots of layers of connective tissue called lamellae
what happens when a Pacinian corpuscle
- e.g. by a tap on the arm
- the lamella are deformed, and press on the sensory nerve ending
- this causes deformation of stretch-mediated sodium channels in the sensory neurones cell membrane
- this means that the sodium ion channels open and sodium ions diffuse into the cell
- this creates generator potential
- if it reaches threshold
- triggers an action potential
what do all neurones contain
- a cell body with a nucleus (plus cytoplasm and all other organelles normally present in cells)
- the cell body has extensions that connect to other neurones, called dendrites and dendrons
- and axons
what do dendrites and dendrons do
carry nerve impulses towards the cell body