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Biology M5: Communcation, homeostasis and energy > Neuronal communcation > Flashcards

Flashcards in Neuronal communcation Deck (50)
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What is homeostasis and why is it needed?

different organs have different functions in the body and they must be coordinated to maintain a relatively constant internal environment e.g pancreas and liver work together to maintain blood glucose


What is cell signalling and what are the different ways it occurs?

coordination at a cellular level occurs through cell signalling. One cell releases a chemical which will affect the target cell: transfer of signals locally (between neurones) or over bigger distances (hormones)


How does coordination in plants happen?

The use of plant hormones (e.g phototropsim)


give two differences between hormonal and neuronal communication

Hormonal: uses chemicals in the endocrine system, much slower
Neuronal: uses electrical impulses, much faster communication


Role of neurones

transmit electrical impulses rapidly around the body so it can respond to internal and external stimuli, the different types of neurones carry information from sensory receptor to the effector


Cell body in neurones

Cell body: nucleus surrounded by cytoplasm, large amounts of endoplasmic reticulum and mitochondria which are involved in the production of neurotransmitters


Dendrons in neurones

short extensions that come from the cell body, they divide into smaller branches called dendrites and are responsible for transmitting electrical impulses towards the cell body


Axons in neurones

singular elongated nerve fibres that transmit impulses away from the cell body


Role of a Sensory neurones

transmit impulses from sensory receptors to a relay neurone, motor neurone or the brain.
Have one dendron to carry impulses to cell body (in the centre)
One axon to carry impulses away from cell body


Role of a relay neurone

Transmit impulses between neurones, many short axons and dendrons


Role of a Motor neurone

Transmit impulses from relay neurones to effectors, such as a muscle or a gland, one long axon and many short dendrites (cell body one end)


Myelinated neurones

Schwann cells produce the myelin sheath which covers the entire axon on myelinated neurones as an insulating layer


Effects of myelination

Insulating layer and makes conduction of impulses faster - myelinated impulses can travel as fast as 100m per second/ non-myelinated 1m every second


Nodes of Ranvier

small gaps between Schwann cells occurring every 1-3mm in humans.
This way the impulse has to jump from neurone to neurone which means it is transmitted faster.
Non-myelinated neurones have impulses travelling continuously along


Role of Sensory receptors

convert the stimulus they detect into a nerve impulse
Information is passed through the CNS to the brain


Features of sensory receptors

- specific to one type of stimulus
- act as a transducer, convert stimulus into an impulse called a generator potential


4 main types of sensory receptors

mechanoreceptor: pressure and movement (pacinian corpuscle)
chemoreceptor: chemicals (olfactory receptors)
thermoreceptor: heat (end-bulbs of krause)
photoreceptor: light (cone cell, different wavelengths of light)


Pacinian corpuscle

detect mechanical pressure
located deep within the skin and are most abundant in the hands and soles of feet


Structure of a pacinian corpuscle

end of a sensory neurone is found in the centre of the corpuscle surrounded by connective tissue
within the neurone's membrane there are sodium ion channels which transport them through the membrane


Conversion in pacinian corpuscle

at normal state/resting potential, the stretch-mediated sodium ion channels are too narrow to allow sodium to pass through

When pressure is applied the corpuscle changes shape and the membrane around the neurone stretches

Sodium ion channels now widen and sodium can diffuse into the neurone

Influx of the ions changes the potential of the membrane so it is now depolarised which creates a generator potential

generator potential then creates an action potential


What is resting potential

the potential difference across the membrane when a neurone is not transmitting an impulse. The outside of the membrane is more positively charged than the inside of the axon. The membrane is polarised and is at a potential of about -70 mV


Outline the creation of a resting potential

1. Sodium ions are actively transported out of the axon and potassium ions are transported in (ratio of 3:2).
2. There are more sodiums outside of the axon and more potassiums inside the axon so the sodiums move back into the axon cytoplasm down the electrochemical gradient.
Most gated Na+ channels are closed but many K+ ones are open and so potassium can diffuse out


What is a neurotransmitter?

chemical messengers - endogenous chemicals that allow neurotransmission


What is an excitatory neurotransmitter?

neurotransmitter that results in the depolarisation of the postsynaptic neurone - if threshold is reached in the postsynaptic membrane an action potential is triggered


Give examples of excitatory neurotransmitters

Acetylcholine, dopamine, serotonin,


What is an inhibitory neurotransmitter?

neurotransmitter that results in the hyperpolarisation of the postsynaptic membrane. This prevents the action potential being triggered.


Give examples of inhibitory neurotransmitters

GABA, glycine


Describe the process of the transmission of impulses across synapses

1. action potential reaches the end of the presynaptic neurone
2. depolarisation of the presynaptic neurone causes calcium ion channels to open
3. calcium ions diffuse into the presynaptic knob
4. this causes synaptic vesicles to move the the membrane and fuse with it
5. the neurotransmitter is released by exocytosis
6. neurotransmitters diffuse across the synapse and bind with receptors of the postsynaptic membrane
7. sodium ion channels open
8. sodium ions channels diffuse into the postsynaptic neurone
9. this triggers an action potential that is then propagated across the postsynaptic neurone


How and where is acetylcholine broken down?

Acetylcholinesterase breaks down Ach in the


What is saltatory conduction?

when the action potential 'jumps' from one node of ranvier to another - much faster than a wave of depolarisation along the whole length of the axon membrane