Module 5.1.3 Neuronal Communication Flashcards
What is the difference between a nerve & a neurone?
Nerve - tissue
Neurone - cell
What is the function of a neurone?
To transmit/carry electrical impulses
What is the structure of a neuron?
Soma/cell body
Dendrite
Dendron
Myelin sheath
Schwann cell
Nodes of Ranvier
Axon
Axon terminals
What is the function of the soma?
Contains the nucleus & is part of the dendrites in motor & relay neurones
What is the function of the dendrite?
Recieves the stimulus via receptors & carries it to the cell body via the dendron in sensory neurons
What is the function of the dendron?
Transmit the electrical impulse
Which neurone is the dendron present in?
Sensory
What is the function of the myelin sheath?
Protects & insulates the axon to speed up the electrical impulse
What is the function of the Schwann cell?
Forms layers of myelin around the axon for insulation
What are nodes of Ranvier & what is their function?
The gaps formed between the myelin sheath were the axons are left uncovered so the action potential can speed up
Why is the whole of the neuron not insulated with myelin?
There wouldn’t be any gaps to speed up the electrical impulse so the electrical impulse would carry the impulse very slowly
What is the function of the axon?
To transmit the electrical impulse
What is the function of the axon terminals?
Carries neurotransmitters in vesicles
What are the 3 types of neurone?
Sensory
Motor
Relay
What is the structure of the sensory neurone?
Cell body in the middle
Long dendrites
Has dendrons
Short axons
What is the function of the sensory neurone?
Brings impulses from the sensory organs into the CNS
What is the structure of a motor neurone?
Cell body at the dendrite end
Short dendrites
No dendrons
Long axon
What is the function of the motor neuron?
Carries the electrical impulse from the CNS to the effector organs (muscles/glands)
What is the structure of the relay neurone?
cell body in the body
Long dendrites
No dendrons
Short axon
What are the major structures in the brain?
Cerebral cortex
White matter
Grey matter
Lobes
Brain stem
Cerebellum
What the structure of the cerebral cortex?
Left & Right Hemispheres
What functions does the cerebral cortex control?
Consciousness, intelligence, memory & language
What are the Left & Right hemispheres connected by?
The corpus callosum
What is white matter?
Nerve cells covered in myelin (gives is it’s white colour)
What is grey matter?
The folds of the cerebral cortex
What are the 4 different lobes in the brain?
Frontal
Parietal
Temporal
Occipital
What functions does the frontal lobe control?
Thinking, planning, organising, problem solving, emotions, personality
What functions does the occipital lobe control?
Vision
What functions does the temporal lobe control?
Memory, understanding & language
What functions does the parietal lobe control?
Movement, orientation, memory & recognition
What is the medulla oblongata?
The brain stem
What functions does the Medulla oblongata control?
Involuntary actions (e.g. heartbeat)
What functions does the cerebellum control?
Controls balance, gross motor skills & coordination or muscular activity
What is action potential?
The momentary reversal of membrane potential that is the basis for electrical signalling within neurons
What are the 3 components that are involved in controlling the resting & action potential of the neuron?
The Na+ K+ pump
The Na+ voltage gated channels
The K+ voltage gated channels
How are sodium & potassium ions transported across a membrane through a sodium potassium pump?
By active transport (requires energy)
How are sodium & potassium ions transported across a membrane through a sodium/potassium voltage gated channel?
Facilitated diffusion
What is the resting potential of a membrane?
-70mV
How is the resting potential maintained?
The sodium potassium pump is open to pump 3Na+ ions outside the cell & 2K+ ions into the membrane via active transport. Both sodium & potassium voltage gated channels are closed to ensure sodium doesn’t reenter the cell making the cell to positive & potassium cannot leave the cell, making the cell too negative, which allows a resting potential of -70mV to be maintained
What is value for the action potential?
+40mV
What are the 3 steps of the action potential?
Depolarisation
Repolarisation
Hyperpolarisation
What happens at depolarisation?
Both the sodium potassium pump & the sodium voltage gated channels are open to allow sodium ions to enter the cell, making it more positive whereas the K+ voltage gated channel closes so the membrane can be at +40mV
What happens during depolarisation & repolarisation?
The action potential reaches its peak
What happens after depolarisation?
Repolarisation
What happens during repolarisation?
Both the sodium potassium pump & the K+ voltage gated channels are open to allow the potassium ions to leave the cell which makes the membrane increasingly negative. The Na+ voltage gated channel closes to ensure this aswell so the membrane reaches -90mV
What happens after repolarisation?
Hyperpolarisation
What is hyperpolarisation also known as?
The refractory period
What happens during hyperpolarisation?
So that the membrane can return to -70mV both the Na+ & K+ voltage gated channels close but the sodium potassium pump remains open so that the membrane can stay negative but the membrane can become a little bit more postive due to the influx of sodium ions
What is the threshold potential?
Above -55mV where there is enough sodium voltage gated channels to increase the membrane’s positivity so an action potential can fire?
What happens if the threshold potential isnt met & why?
An action potential doesn’t fire as an action potential is “ all or nothing”
Explain the process of the threshold potential
The threshold potential needs to be met so that the action potential can occur & fire. This is above -55mV. This is because an action potential is “all or nothing” which means that this threshold potential must be overcome otherwise the action potential wont fire. This occurs because the stimulus is able to release enough cell signalling molecules that are able to open enough Na+ voltage gated channels so that more sodium ions can enter the cell & make the membrane more positive to the point that is is above -55mV and the action potential can fire
What direction does an action potential fire?
Unidirectional (From dendrite to terminal buttons)
What is saltatory conduction?
The ‘jumping’ of action potentials between nodes of Ranvier
What are sensory receptors?
Receptors found in sensory organs that act as transducers & are specific to one type of stimulus e.g. light
Why are sensory receptors specific to one type of stimulus?
To ensure responses are coordinated properly
What are transducers?
Things that turn a stimulus into an electrical impulse/generator potential
What are the 4 types of sensory receptor?
Mechanoreceptors
Chemoreceptors
Thermoreceptors
Photoreceptors
What are the function of Mechanoreceptors?
Sensitive towards pressure/movement
What is an example of a mechanoreceptor?
The pacinian corpuscle
What is the function of a chemoreceptor?
Receptors that are sensitive towards chemicals e.g. taste
What is an example of a chemoreceptor?
The olfactory receptor
What is the function of thermoreceptors?
Receptors that are sensitive to changes in temperature
Where would Thermoreceptors usually be found in the body?
Present on the tongue & the skin’s surface
What is the function of photoreceptors?
Receptors that are sensitive towards light
Where would photoreceptors usually be found in the body?
Present in the cone cells in the retina of the eyes
What is the pacinian corpuscle?
A specific mechanoreceptor sensitive towards pressure & movement
Where is the pacinian corpuscle found in the body?
In the fingertips/soles of the feet & in the joints
What is the structure of the pacinian corpuscle?
Stretch-mediated sodium ion channels
Capsule
Connective tissue
Gel
Sensory neurone
Describe what happens to the pacinian corpuscle at resting state
The stretch-mediated are closed so the sodium ions on the outside cannot enter the cell. This makes the inside of the sensory neurone negative & the outside of the membrane positive so no action potential fires down the sensory neurone
Describe what happens when pressure is applied to the pacinian corpuscle?
The shape of the pacinian corpuscle changes so the stretch-mediated sodium ion channels open. Due to the high electro-chemical gradient of sodium ions outside they diffuse into the sensory neurone & depolarise the membrane. This initiates a generator potential that is similar to a threshold potential & triggers an action potential down the sensory neurone to the CNS (brain)
Why are action potentials described as unidirectional?
The dendrites are found at one end of the cell & the axon terminals are found at the opposite end, meaning that the action potential can only travel in one direction
Sodium ions are positive so they travel in the direction of negativity, so it jumps to the next node of ranvier through localised currents in unmyelinated neurons
Why are action potentials described as “all or nothing”?
The stimulus must be strong enough to open all of the voltage-gated channels to cause the membrane to overpass the threshold potential
What are the 2 types of neurotransmitter?
Excitatory and inhibitory
What is an excitatory neurotransmitter?
Neurotransmitters that cause an influx of sodium ions that depolarise the membrane
What is an inhibitory neurotransmitter?
Neurotransmitters that cause potassium ions to leave the membrane causing repolarisation
