✓ Neurons & Synaptic Transmission (AO1) Flashcards
Describe the structure of a Neuron?
__ / dendrite
/ \ / cell body
| . |/ nucleus
\__/
|
gap = nodes of ranvier
|
myelin sheath
| schwann cells
|
axon
|
—-|—-
/ | \
/ | \
/ | \
. . . axon terminals
Function of dendrites?
branch-like + receive signals from other neurones
Function of cell body?
contains the nucleus
Function of nucleus?
contains genetic material
Function of axon?
long slender fibre that carries nerve impulses away from the cell body
Function of schwann cells?
form myelin sheath
Function of myelin sheath?
protects the axon so that the electrical impulses travel faster along the axon
Function of nodes of ranvier?
gap in the myelin sheath - speeds up the transmission
Function of axon terminals?
at the end of the axon, contains neurotransmitters (stored in vesicles)
What are Hormones?
produced by endocrine gland
released into bloodstream
takes longer time to have an effect
widespread effects around the body
What are Neurotransmitters?
released by nerve terminal
released into synapse
has an immediate effect
direct effect to next neuron
Function/Structure of sensory neuron?
carries impulses from the PNS receptors to CNS ,sometimes only spinal cord (no brain) = reflex actions
long dendrites, short axons
Function/Structure of relay neuron?
carries impulses from sensory neurons to motor neurons - allows them to communicate (relay neurons only in CNS)
short dendrites, short axons
Function/Structure of motor neuron?
carries impulses from CNS to effector (e.g. muscles or glands)
short dendrites, long axons
Describe the Structure of a synapse?
/ \ axon
/ \
/ \ nerve impulse |
/ \ \/
/ \
/ \
/ - . \ synaptic knob
/ . - \ vesicles .
/ . - . \ mitochondria -
—————
synapse
......_ postsynaptic receptor sites
Step 1 of synaptic transmission?
action potential travels down the axon of the pre-synaptic neuron
Step 2 of synaptic transmission?
vesicles release neurotransmitter into synaptic cleft (synapse)
Step 3 of synaptic transmission?
neurotransmitters bind to post synaptic receptors & take an effect
Step 4 of synaptic transmission?
excess neurotransmitters are taken up by the pre-syn neuron re-uptake pump
(vesicles are replenished w new + reused neurotransmitter)
Step 5 of synaptic transmission?
enzymes are released to break down the remaining neurotransmitter
Step 6 of synaptic transmission?
summation
Role of neurons in synaptic transmission?
neurons must transmit info both within the neuron & from one neuron to the next
+
an elec signal called an action potential transmits info within a neuron, down the axon to the axon terminals
+
once an action potential reaches the axon terminals the signal has to be passed onto the next neuron - this is done via synaptic transmission
+
st, which passes the signal over the synaptic gap between the 2 neurons through a chemical process
Action Potentials?
when a neuron is in a resting state the inside of the cell is - charged compared to the outside
+
when a neuron is activated by a stimulus the inside of the cell becomes + charged for a split second
+
this causes an action potential to occur
+
this creates an elec impulse that travels down the axon towards the end of the neuron
Summation?
whether or not the next neuron fires another action potential & continues the message depends on summation
+
if there is more of a + charge (excitatory NTs) than a - charge (inhibitory NTs) = the action potential will fire
+
if there is more - than + the action potential will not fire
Excitation?
NTs that are excitatory cause the receiving neuron to be more likely to fire e.g. dopamine
+
known as “on switches” - cause excitation of the post-synaptic neuron by increasing its positive charge
Inhibition?
NTs that are inhibitory cause the receiving neuron to be less likely to fire e.g. seretonin
+
known as “off switches” - cause inhibition of the post-synaptic neuron by increasing its negative charge, making it less likely to fire
