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Neuronal Communication (Role of Sensory Receptors (Sensory Receptors…
Neuronal Communication
Role of Sensory Receptors
Sensory Receptors
Sensory Receptors
:
cells/ sensory nerve endings that respond ti a stimulus in the internal or external environment of an organism and can create action potentials
Most are
transducers
, a cell which can
convert one form of energy to another
(electrical impulses)
Light, heat, movement or chemical changes can be converted to
electrical impulses
by sensory receptors
Pacinian Corpuscles
Pacinian Corpuscles
:
pressure sensors
Rings of connective tissue may deform, pushing against the nerve ending it surrounds to detect change in pressure
Generating Nerve Impulses
Creating Membrane Permeability
Creating Nerve Impulse
At rest, the cell is polarised
Impulsed are created by a change in
permeability
of the membrane to
sodium ions
. Small stimuli open only a few sodium channels, large stimuli will open many and cause an
action potential
(an impulse)
A
generator potential
is created by cell
depolarisation
Structure and Function of Neurones
Neurone Functions
Sensory Neurone --> Relay Neurone --> Motor Neurone
Sensory Neurone
: carries
action potential
to the Central Nervous System (
CNS
) from a sensory receptor. The cell body is just ourside the CNS and the short axon in the CNS
Relay Neurone
: Connect sensory and motor neurones
Motor Neurone
: carries
action potential
from
CNS
to an effector. The cell body is in the CNS and the long axon outside it
Neurone Structure
Mylenated and Non-Mylenated Neurones
Mylenated
Non-Mylenated
Nerve Impulses: Action Potentials
Nerve Inpulses: Transmission
Local Currents
Movement of charged particles
Sodium ion channels open, causing sodium to move into the cell,
depolarising
it
The
sodium ions move
along the axon away from the area of increased concentration, causing a
local current
Positive feedback
cause more sodium ion channels to open further along the neurone causing
full depolarisation
. The
action potential
has now moved along the neurone
Saltatory Conduction
Action potentials jumping from node to node in mylenated neurones
This
speeds up
transmission of the action potential.
Action potentials can only occur in the
Nodes of Ranvier
in mylenated neurones
Frequency
All action potentials are the
same intensity
More intense
stimuli produce a
higher frequency
of action potentials
Higher intensity stimulus
cause more
sodium ion channels
to be
opened
Synapses 2
Synapses 1