M5 C13: neuronal communiction Flashcards
what is an example of a change in the internal environment?
blood glucose conc
internal temperature
water potential
cell pH
what is an example of a change in the external environment?
humidity
external temperature
light intensity
how do animals respond to changes in the environment?
chemical responses (via hormones)
electrical responses (via neurones)
how do plant respond to changes in the environment?
chemical responses (via hormones)
why is coordination needed?
few body systems can work in isolation so organisms need to coordinate the function of different cells and systems to operate effectively
what is an example of coordination?
in order to contract muscle cells must respire and therefore need oxygen however they cannot get this oxygen themselves so rely on red blood cells. red blood cells rely on stem cells to replicate as they have no nucleus.
what is homeostasis?
maintaining a relatively constant internal environment
what is cell signalling?
one cell releasing a chemical that has an affect on another cell known as a target cell
what response transfers signals locally?
electrical response
between neurones at a synapse known as a neurotransmitter
what response transfers signals across large distances?
chemical response by using hormones
for example the pituitary gland secretes ADH which has an affect on the kidneys
how do plant respond to environmental changes?
by hormones (a chemical response)
what does the nervous system do?
detects changes known as stimuli and triggers an appropriate response
what does the motor neurone do?
transmit impulses from relay neurone or sensory neurone to an effector they have one long axon and many short dendrites. it also has a cell body and nucleus
what does the relay neurone do?
has a cell body and a nucleus, with lots of axon and dendrons coming off of it. with axon terminals and dendrites
what does the sensory neurone do?
transmits impulses from receptor cell to a relay neurone, motor neurone or brain
what does the sensory neurone look like?
has a central cell body with axons going away towards axon terminals and dendron going towards it from dendrites
what are the gaps called between the myelin sheath?
node of ranvier
what is the myelin sheath?
schwann cells produce layers of plasma membrane around axons/ dendrons creating a myelin sheath to insulate neurone
what is saltatory conduction?
where signals jump from node to node
how does multiple sclerosis occur?
immune system sees schwann cells as foreign which triggers an immune response. this causes the myelin sheath to be destroyed making it longer for the impulse to travel.
what are sensory receptors?
they are located in sense organs. allows body to detect changes in the environment. they are specific to one type of stimulus and act as transducers.
what are transducers?
take stimulus and converts it into a generator potential. (electrical impulses)
what is the Pacinian corpuscle?
sensory receptors that detect pressure and touch
where is the pacinian corpuscle located?
deep within skin eg the end of fingertips, soles of feet
what is the resting membrane potential?
-70mv
how is the pacinian corpuscle depolarised?
an influx of positively charged sodium ions from outside the membrane through the stretch mediated sodium channels
how do the stretch mediated sodium channels open?
open due to pressure being applied near the receptors
what does the generator potential lead to?
action potential
how does the sodium- potassium pump work in the axon membrane?
it actively pumps sodium ions out of the axon and pottasium ions into the axon in the ratio 3:2. more positive on the outside
what does the sodium- potassium pump create?
the electrochemical gradient for sodium to diffuse into the axon and potassium back out
can potassium ions move back out after being pumped into the axon?
yes they can diffuse out through open potassium ions channels
can sodium ions move back in after being pumped out of the axon?
no because the sodium ion channels are closed
what does the excess of positive charge on the outside of the membrane create?
a negative charge so the resting potential of the membrane is -70mv
how is action potential created?
when the axon membrane is depolarised by the energy of the stimulus
what is the potential difference of the membrane after it has been depolarised?
+40mv
what happens after the impulse passes?
the membrane repolarises and and the charge goes from negative to positive. the neurone returns to rest
how is action potential propagated?
it starts at one end of the neurone and are propagated along the axon to the other end. depolarisation of one region acts as a stimulus for depolariastion of the next region
what does the energy of the stimulus trigger?
triggers some voltage gated channels to open. causing depolarisation as the charge changes
what does the change in charge from depolarisation cause?
more sodium ions to move as more channels are opened. this is an example of positive feedback
what happens at +40mv?
the voltage gated sodium ion channels close and the voltage gated potassium ion channels open
what happens after the voltage gated potassium ions open?
potassium ions diffuse out of the axon down the electrochemical gradient reducing the charge - repolarisation