Neurons and synpatic transmissions Flashcards
Where are most neurones located and how can signals be transmitted
80% of the neurones are located in the brain
Signals can be trasnmitted Chemically (across a synapse) and Electronically within a nerve cell
How many total neurones are there in the body
100 billion
What are the three types of neruones
Motor
Sensory
Relay
What is the size of neurones
They vary in size from less than a mm to a metre long
What is the basic structure of a neurone
They have a soma (body) which includes the nucleus-contains the genetic information in a cell-
And they have branch like structures called dendrites which portrude from the cell body
What does the axon do?
The axon carries electrical impulses away from the cell body down the length of the neuron
What is the neuron covered in
A myelin sheeth which insulates and protects the axon as well as speeds up the electrical transmission of the impulse
What would happen if the Myelin sheeth was continuous
It would slow down the electrical transmission
What are the nodes of ranvier
The gaps between myelin sheeth
They speed up the transmissions of the impulse as they force it to jump across the gaps along the axon
Allow ions to diffuse in and out of a neurone
What is at the end of the axon
Terminal buttons- Allow communication with the next neuron across the synapse (a gap)
What is electron transmission
The firing of a neuron
Is the neuron positively charged or negatively charged when it is in its resting state compared to the outside
Negatively charged inside positvely outside
What is an action potential
The change in electric potential that propagates along the axon during the transmission of a nerve impulse or the contraction of a muscle.
What are the 2 steps in electrical transmission
- Has to teach the action potential
- electrical impulse travels down the axon towards the end of a neuron
What are neural networks
The way neurons communicate
What is a synapse
A gap that separates a neuron from another
What does a synapse include
A gap between them (synaptic cleft) as well as the presynaptic terminal and post synaptic receptor site
How are signals within neruons trasnmitted
Electrictronically
How are signals between neurons trasnmitted
Chemically by synaptic trasnmissions
What happens when an electrical impulse reaches the end of a neuron (presynaptic terminal)
Triggerers the release of a neurotransmitter from tiny sacs called synaptic vesicles
What are neurotrasnmitters
Chemicals released from the synpatic vesicle that relay signals across the synapse from one neuron to another
What happens once the neurotransmitters cross the synpase
It is taken up by the postsynaptic receptor sites-dendrites of the next neuron-
Here the chemical message is converted into an electrical impulse and the process of transmission happens again
What is an example of a neurotrasnmitter having a specialist function
- Acetylcholine is found at each point where a motor neuron meets a muscle
- Causes the muscle to contract
What are the two effects a neuron can have on the neighbouring neuron
Excitiory or inhibitory
What does serotonin do to the recieving neuron
Serotonin inhibits the recieving neuron resulting in that neuron becoming more negatively charged
What does adrenaline do to the receiving neurone
Adrenaline causes excitation of the post synpatic neuron by increasing its positive charge and making it more likely to fire
When are action potentials of the post synpatic neuron triggered
When the sum of the excitory and the inhibitory signals at any one time reach the thrreshold
What is the length of dendrites and axons in all three differnet neurons (Sensory Relay and Motor)
Sensory neurons have long dendrites and short axons
Relay neurons have short dendrites and short axons
Motor neurons have long axons (lead
to muscles) and short dendrites.
What is the location of a sensory neuron?
- Located in receptors such as: eyes, ears, tongue and skin
- Also located in the PNS in clusters known as ganglia
What is the function of a sensory neuron (4)
- Carry nerve impulses to the spinal cord and brain from the receptors
- When these impulses reach the brain they are translated into ‘sensation’ for example, visual input.
- However, NOT all sensory information
- reaches the brain, some neurons stop at the spinal cord – allowing for quick reflexes.
- Carry messages from the PNS to the CNS
Where are relay neurons located
- Found only in the brain and spinal cord.
- They lie somewhere between sensory input and motor output.
What is the function of the relay neuron
To allow sensory and motor neurons to
communicate with each other
Where are motor neurons located
In the central nervous system (CNS)
What is the function of motor neurons (2)
- When stimulated they release neurotransmitters that bind to the receptors on the muscle to trigger a response, leading to movement.
- They form synapses with muscles to control their contractions.
What is synaptic transmission
The process by which neighbouring neurons communicate with each other by sending chemical messages across the synpatic cleft which separates them
