Lecture 1 - Neurons and Neurotransmitters Flashcards
The brain is the organ of …
Interpretation and prediction - continually taking in sensory data and integrating the into with previous experiences to then make predictions
Pareidolia
seeing faces in inanimate objects
Central nervous system
Brain and spinal cord
Peripheral nervous system
Nerves - collects information from organs/muscles, carry information to muscles to carry out movement and allow organs to operate
Four lobes of the human brain
Frontal lobe, parietal lobe, occipital lobe, temporal lobe
Frontal lobe
decision making, executive function, high order processing, controlling behaviour
Parietal lobe
helping body move through space
Occipital lobe
visual system interpretation
Temporal lobe
memory system - building memory and interpreting visual stimuli
Brains processing units =
Neurons
Neurons
neurons which are specialised nerve cells
How many neurons in average human brain?
approx 85 billion in the average human brain - each makes 100-10000 connections with others and these connections are important for allowing you to store information and behave in different ways
What is the key to information processing in the nervous system?
simple fact that the inside of a neuron is negatively charged compared to the outside i.e. neurons have a resting membrane potential of -70mV (sits at this when the neuron is not transmitting information)
Lots of positively charged sodium on the outside and lots of negatively charged anions on the inside which gives a negative charge on the inside compared to the outside
There are ion channels that move ions from inside to outside and outside to inside
Information is transmitted within the neuron cell by….
transient alteration in the membrane potential (transmit information by small changes in membrane potential)
Dendrites
Input
Axon
output
Graded potential
Within dendrites the pulse can vary in size i.e. it is a graded potential. Graded potentials are changes in membrane potential that vary in size, as opposed to being all-or-none. … The magnitude of a graded potential is determined by the strength of the stimulus.
Temporal summation
Arrival of stimulus immediately after each other resulting in addition of them together
Where PSP’s that occur in quick succession add up/summate
Spatial summation
Spatial = addition of multiple stimulus from multiple neurons to a single postsynaptic neuron
Where PSP’s from different areas of the input zone add up/summate
Action potential
Within axons, this “pulse” is all or none (an action potential) depending upon whether it reaches a threshold level of intensity at the initial segment
Difference of action potentials compared to graded potentials
AP occurs extremely rapidly and then is gone in a very short amount of time
AP can in mV is massive compared to graded potentials
Tetrodotoxin (TTX)
Blocks ion flow through channels that generate action potentials
10000 times deadly than cyanide, found in puffer fish
Neurons are the
basic building blocks of the nervous system
three main parts of a neuron
dendrite, cell body (soma) and the axon
Dendrites
specialised receiving unit
Axons
conducts electrical impulses away from the cell body to other neurons, muscles or glands
Glial cells
support cells of the nervous system
Within the brain glial cells…
outnumber neurons about 10 to 1
Nerve activation involves 3 basic steps
1 - at rest, the neuron has an electrical resting potential due to the distribution of positively and negatively charged chemical ions inside and outside the neuron
2- when stimulated, a flow of ions in and out through the cell membrane reverses the electrical charge of the resting potential, producing an action potential, or nerve impulse
3 - The original ionic balance is restored and the neruon is restored and the neuron is again at rest, ready to be stimulated again
Ions in ECF and ICF
outside cell = high Na+, low K+ and high Cl-
inside cell = Low Na+, high K+ and low Cl-
Resting membrane potential
internal difference of around -70mV
At rest, the neuron is said to be in a state of
polarisation
Action potential
Electrical shift of about -70mV to +40mV
also called a nerve impulse
Order of events in an action potential
resting membrane potential
Depolarisation
Action potential
repolarisation
sodium flows in =
depolarisation
potassium flows out =
repolarisation
Action potentials are
all or nothin
Absolute vs relative refractory
absolute = no AP relative = can get AP but much harder to generate one
Myelin sheath =
fatty insulation layer derived from glial cells during development
Unmyelinated axons are what colour
grey in colour which is why it is called grey matter and myelinated axons are often called white matter
Synaptic space
tiny gap between the axon terminal and the next neuron
Neurotransmitters are
chemical substances that carry messages across the synaptic space to other neurons, muscles or glands
Neurotransmitter examples
ACh Noradrenaline Serotonin Dopamine GABA Endorphin
Drugs that block the action of ACh
can prevent muscle activation and cause paralysis
Neuromodulators
Have more widespread and generalised influence on synaptic transmission
