Intro to neurones Flashcards
What is the function of dendrites?
increase the surface area for synapses, they receive inputs from other neurones and convey graded electrical signals passively (without APs) to the soma
What is the function of the soma?
metabolic hub of the neurone, provides axons with nergy and proteins. contains nucleus and other features
What is Nissl substance?
RER of the soma
What is the axon initial segment?
most excitable part of the neuron where APs are initiated
What is anterograde direction through a nerve?
from the soma to the presynaptic terminal
Which viruses exploit retrograde transport?
herpes; polio; rabies
Give an example of a unipolar neurone?
peripheral autonomic neurone (parasympathethic postganglionic)
What is a psudounipolar neurone?
one neurite that bifurcates
Give an example of a pseudounipolar neurone?
dorsal root ganglion
Give an example of a bipolar neurone?
retinal bipolar neurone
Give an example of a mulitpolar neurone?
lower motor neurone
What are the four functional regions of neurones?
input; integrative; conductile and output
What is the overshoot of an AP?
brief period when polarity of the membrane is reversed so that the inside is positively charged
Why is there an undershoot?
membrane potential becomes more negatively charged than the resting potential for a short period as the potassium channels dont close as soon as resting potential is reached
What factors increase the distance that a signal will spread?
increased membrane resistance and decreased axial resistance of axoplasm
How can the axial resistance of the axoplasm be decreased?
by increasing the diameter
How does an AP conduct along an axon?
postivie charge spreads passivley to negatively charged parts since opposite charges attract
Why does an AP not go back the way?
channels are refractory
What is saltatory conduction?
AP jumps from one node of Ranvier to the next
What is a node of Ranvier?
the space between Schwann cells
What are the 3 types of synapse?
axodendritic; axosomatic and axoaxonic
What is the most common type of synapse?
axodendritic
What is the most common excitatory transmitter in the CNS
glutamate
What response does glutamate generate?
excitatory postsynaptic potential
What is the difference ebtween an AP and an epsp?
an epsp is local and graded
What are the main inhibitory transmitters in the CNS?
GABA and glycine
What type of response do GABA and glycine generate?
inhibitory postsynaptic potential
What holds the pre and post-synpatic membranes together?
a matrix of fibrous extracellular protein
What is the area that pre-synaptic vesicles cluster around?
active zone
What is the area that contains the neurotransmitter receptors postsynaptically?
postsynaptic density
What ion does the ipsp use?
chloride
What is spatial sumation?
many inputs converge upon a neurone to determine its output
What is temporal summation?
a single input may modulate output by variation in AP frequency of that input
What type of vesicle are amino acids and amines released from?
synaptic vesicles
What type of vesicle are peptides released from?
secretory vesicles
What makes GABA and amines more difficult than amino acids to use?
amino acids are found in all cells whereas GABA and amines require specific enzymes in neurones
How are transmitters released at synapses?
calcium induced release of transmitter (exocytosis)
How are enzymes transported from the cell body to the presynaptic terminal?
axoplasmic transport via microtubules
What is the labeled line principle?
primary sensory afferent fibres confer modality by their site of termination in the CNS
How does mechanical stimuli cause an AP?
stretch of the membrane caused by the dermation causes ions channels to open and create a graded passive depolarisation which creates an AP at the first node of Ranvier
How is the frequency of APs generated by receptor potential determined?
proportional to the amplitude of the receptor potential or the degree of deformation
Where is the greatest sensitivity to change of stimulus strength?
low stimulus strength
