5.1.3- Neuronal Communication Flashcards
what are sensory receptors?
specialised cells that detect stimuli
what are sensory receptors known as and why?
ENERGY TRANSDUCERS
they convert different forms of energy into electrical energy
what are the 4 types of sensory receptors and what is their stimulus?
1- Mechanoreceptor- pressure and movement
2-Chemoreceptors- chemicals
3-Thermoreceptors- heat
4- Photoreceptors- light
what is an example of a mechanoreceptor?
Pachinian Corpuscle, in the skin
what is an example of a chemoreceptor?
Olfactory receptor in the nose
what is an example of a thermoreceptor?
End-bulbs of Kraus, in the tongue
what is an example of a photoreceptor?
Cone cells in the eye
what is the function of a sensory neurone?
carry impulses from receptors to the CNS
what is the function of a relay neurone?
connect the sensory and motor neurone, present in the CNS
what is the function of a motor neurone?
carry impulses from CNS to effectors
when in resting potential, what is the neurone cell membrane described as?
polarised
what is resting potential?
the potential difference across the neurone cell mebrane while the neurone is at rest
what happens during resting potential of neurones?
-3 sodium ions are transported out
-2 potassium ions are transported in
-the sodium-potassium pump controls this
-the sodium ion channels are closed so that sodium cannot come back into the neurone, while the potassium ion channels remain open so they can move back out
-this leads to the inside being negative and the outside being positive, with a difference of around -70mV
what is action potential?
the depolarisation of the neurone cell membrane, so the inside is more positive than the outside, occurring when the cell is active
what happens during action potential of neurones?
-sodium ion channels open, and potassium ion channels close
-this causes a rush of sodium ions into the neurone, causing the flip of charge
-the change becomes around +40 mV
what occurs during repolarisation of neurones?
-the Na ion channel closes but the K ion channels open, which leads to a flood of K entering the neurone
-however, this can lead to overpolarisation, as the inside will become too negative
-therefore, the sodium-potassium pump works to get it back to normal
what is a pacinian corpsucle?
a specific sensory receptor that detects mechanical pressure
how does a pacinian corpuscle convert mechanical pressure into a nervous impulse?
-normal state, PC has a resting potential
-stretch-mediated sodium channels in sensory neurones membrane are too narrow to allow Na ions to pass through
-pressure is applied, so the PC changes shape, membrane stretches
-Na ion channels widen so Na ions diffuse in
-membrane becomes depolarised, resulting in a generator potential
-generator potential if reaching threshold potential creates an action potential
what is generator potential?
the transmembrane potential difference produced by activation of a sensory receptor
what is habituation?
-body gets used to a particular ‘feeling’ if the body receives the stimulus over a long period of time.
—> less stimulation of corpuscle over time
what is a nerve impulse?
a wave of depolarisation followed by a wave of repolarisation
how is a nerve impulse transmitted?
-when an action potential is set up, the influx of sodium ions set off the transmission along the neurone
-the increase of these ions set up a local current
-these ions then diffuse sideways along the neurone, causing voltage-gated sodium channels to open further down the neurone, setting off another action potential
-local current moves down as a wave of depolarisation, followed by the nerve impulse (wave of repolarisation)
how is a nerve impulse transmitted?
-when an action potential is set up, the influx of sodium ions set off the transmission along the neurone
-the increase of these ions set up a local current
-these ions then diffuse sideways along the neurone, causing voltage-gated sodium channels to open further down the neurone, setting off another action potential
-local current moves down as a wave of depolarisation, followed by the nerve impulse (wave of repolarisation)
what does a more intense stimulus mean in terms of frequency?
a high frequency of nerve impulses
what is a myelinated neurone?
when a neurone has a fatty sheath wrapped around it, providing electrical insulation, along side layers of membrane, Schwann cells, nodes of ranvier
what is the speed of conduction of a myelinated neurone?
FAST= 120m/s
known as saltatory conduction
what is a unmyelinated neurone?
when several neurones share one lossely wrapped schwann cell, no nodes of ranvier and no fatty sheath, and so action potential moves along in a wave with no jumping
what is the speed of conduction of an unmyelinated neurone?
SLOW= 20m/s
what is the advantages of myelinated neurones?
-action potential is transmitted more quickly
-rapid response
-saltatory conduction (AP jumps from node to node)
-insulated parts stay resting
what is a synapse?
the junction between two neurones (pre-synpatic and post-synpatic)
what allows nerve impulses to cross the synpatic cleft?
neurotransmitters
what is a cholinergenic synapse?
a synapse which makes and releases acetylcholine.
describe the movement of nerve impulses across a synapse in
8 steps?
1- AP moves down neurone until synpase is reached
2-Within the synpatic knob, acetylcholine is released and transported in vesicles
3- Calcium ions diffuse into the neurone, causing the vesicles to move towards the pre-synaptic membrane.
4-The vesicles then fuse with the membrane (exocytosis), and so acetylcholine diffuses acrosss the synapse towards the post-synaptic membrane
5-the sodium ion channels are attached to a receptor, and these open , allowing the ions to diffuse in
6-Acetylcholine binds to the receptor.
7-This means that the enzyme, acetylcholinesterase is left within the synaptic cleft
8-The enzyme breaks down, with choline moving back into the pre-synaptic neurone, where it then combines with acetylcoenzymeA to create acetylcholine.
what are the two types of summation?
-spatial= occurs when a number of pre- connect with one post-, so neurotransiters build up high enough to trigger AP in post-.
-tempora;= occurs when a single pre- releases neurotransmitter to AP over a short period of time, so it builds up in synpase until sufficient to trigger an AP
