W2 - Biological Basis of the Brain Flashcards
what are the functions of the Nervous System
- controls actions
- sends info from the skin to the brain
- conroles senses and perception
- processing of memories
Central Nervous System (CNS)
is located in the middle of the body and conncets the brain and spinal cord
Peripheral Nerous System (PNS)
stems out from the CNS and connects the lims with the spinal cord
Neuronal Cells
percieves signals (info) and sends that info incoded signal off
Dendrites
are always expecting to detect signals and to send them to the cell body
Cell body
holds the life support system of the cell
Axon
carries info away from the cell body
Terminal region
links to the next cell and sends signals to thier dendrites
Features of Dendritic Spines
they have extra surface area
Axon Hillock
keeps score of the charge of signals coming in
all or nothing
a score below 55 the cell wont fire and send the signal on
the myelin sheath
is an insaltion on the axon and allows for signals to move faser down it
Unmyelinated vs myelinated speed= ~1 m/s : up to 100 m/s
Nodes of Ranvier
the points from which signals jump as they travel down the myelin on axon - saltatory conduction
Glial Cells
specialized cells in the nervious system that support the integrity of neurons
the three main types of glial cells
Oligodendrocytes (biggest)
schwann cells
Astrocytes (start-like shape)
Oligodendrocytes
creates myelin sheaths around axons in the CNS and incraeses speed of info travelling down the axon
Schwann Cells
creates myelin sheaths around axons in the PNS and incraeses speed of info travelling down the axon
Astrocytes (start-like shape)
- helps repair neurons
- helps bring nutreinys from the bloo to neruons (blood-brain barrier)
- provides structeral support for neurons
Excitatory signals
signals make the cell more likely to fire: -55mV or >
Inhibitory signals
signals make the cell less likely to fire: < -55mV
summation
process done by the Axon Hillock - The sum of all incoming signals
(excitatory and inhibitory) determines whether the neuron fires
These two ions are crucial to sending signal down an axon
Potassium - K+
Sodium - Na+
Ion
Molecular clusters with an electrical charge
Ion Channels
Doors in the Membrane for the moevemnt of Potassium K+ down the concentration gradient
how do ions move through the channels in the membrain?
Concentration Gradients & Electrical Gradients
When is resting membrane potential achieved?
when both forces are equally strong
Action Potential
a change in the voltage inside a cell (relative to outside of the cell) taking place at one section of the cell at a time (not the whole cell at once)
what are Voltage Gated
Sodium Channel? (VGNaChannel)
allows Sodium Na+ to enter the cell for initiation and propagation of action potentials
charge of cell at resting potential
-70mV
range of charge of cell at depolarization
-55mV to 30mV
when do VGNaChannel activate
when they detect a chage of -55mV or > they will open creating a chain reation of action potentail down the axon
Na+/K+ Pump
- Throws 3 Na+ out of the cell
- Brings in 2 K+ into the cell
- Requires energy (NOT passive diffusion!)
1 - state of the neuron at: Resting potential
- charge is at -70mV making cells overall charge negative
- K+ VGC closed
- Na+ VGC closed
2 - state of neuron when: stimulus hits threshold
- charge is at -55mV or > leading to an
- Na+ VGC partly open
- K+ VGC closed
3 - state of neuron at: Depolerization
- The membrane potential rapidly rises and may even become positive, reaching around +30 to +40 mV.
- inside of cell is now positivly charge
- Na+ VGC fully open
- K+ VGC closed
4 - state if neuron in: Repolerisation
- Na+ VGC fully closed
- K+ VGC open
- cell beigns to become negitivly chgarde again as K+ leaves
5 - state of neuron in: Refractory period
- Na+ VGC fully closed
- K+ VGC open
- all K+ has left the cell and chrage of cell drops below resting stae becoming too negitivly charge
6 - state of neuron at: return to resting state
- Na+/K+ Pumps activate
- Na+ is taken out
- K+ is drawn in
- charge of cell returns to -70mV
how is Neuronal Communication done?
through Electrochemical processes
within neuron communication
electrical communctaion
Synapse - between neuron communciation
chemical communcation
the 3 types of Synapses
- synapses with other neurons
- neuromuscular Junctions
- neuroglandular Synapses
Presynaptic neurons
the cell sending a signal
Postsynaptic neuron
the cell receiving a signal
Axondendritic synapse
an axon termanal that connects directly to another neurons dentrites
Axosomatic synapse
an axon termanal that connects directly to another neurons cell body
Axoaxonic synapse
an axon termanal that connects directly to another neurons Axon
Potassium K+ and Sodium Na+
These two ions are crucial to sending signal down an axon
Chloride Cl-
Essential for understanding how neurons send inhibitory signals.
Calcium Ca2+
Essential for allowing chemicals in presynaptic cell to exit the cell and enter the synaptic cleft.
step 1: chemical synapse
action potential is traveling down the Axon to the presynaptic terminal
step 2: chemical synapse
action potential arrives at the presynaptic terminal
step 3: chemical synapse
voltage-gated Ca2+ channels open, allowign influx of Ca2+
step 4: chemical synapse
ca2+ allows venricals to merge with the membrane and neurotrasnmitters releases out the other side
step 5: chemical synapse
Neurotrasnmitter binds to receptors, causing channels to open (or close)
step 6: chemical synapse
Excitatory (or inhibitory) postynaptic potential is genenerated
step 7: chemical synapse
Neurotransmitter is removed by glial uptake (or enzymatic degradation)
Reuptake
The pre-synaptic cell membrane has neurotransmitter- specific “transporter” proteins that transport neurotransmitters back into the presynaptic cell
GABA
gamma-aminobutyric acid
Neurotransmitters
Chemical messengers that transmit signals across synapses from one neuron to another neuron (or to a muscle cell or gland cell).
There are different categories of neurotransmitters
- Amino Acids (Glutamate, GABA)
- Monoamines (Dopamine, Serotonin, Histamine)
- Peptides (Endorphins, Oxytocin)
where are neurotrasnmitters made?
they are synthesized inside the cell body or axon terminal of a neuron
Neurotransmitter: Dopamine
- Plays diverse roles in the nervous system:
- Involved in thoughts, feelings, motivations, behaviours
- Associated with the experience of pleasure
- Learning to associate particular behaviours with reward (“reward pathway”)
- Attention, mood regulation, emotional responses
- Coordinating movement (Parkinson’s Disease = progressive loss of dopamine-producing neurons).
Can be excitatory or inhibitory (depends on the receptors)
Neurotransmitter: Serotonin
- Involved in regulation of mood, sleep, eating, arousal, and pain.
- Depression associated with reduced serotonin (thus, antidepressants target neurons that produce serotonin)
- Other ways to increase serotonin levels include sunlight exposure! How?
- Sunlight exposure stimulates production of Vitamin D in the skin.
- Vitamin D is involved in Serotonin synthesis
Agonists Drugs
they occupy receptos and fully activate them
Antagonists Drugs
they occpy receptors but do not activate them
they also block receptors activation by agonists
Alcohol’s effects on neurons
- Alcohol acts as an agonist (for GABA) and an antagonist (for Glutamate)
- Binds to specific part of GABA receptors to make them even more inhibitory
- Also binds to Glutamate receptors preventing the glutamate from exciting the
cell
how do Antidepressants work?
by blocking the Serotinin reuptake transporters from taking seritonin from the synaptic cleft at then end of each synapse making firign more likly to occur next time
Cocaine’s effects on neurons
- Cocaine prevents the reuptake of dopamine.
- It blocks the dopamine transporter on the presynaptic neuron, stopping dopamine from being recycled.
- This causes dopamine to build up in the synapse, leading to prolonged activation of dopamine receptors.
- Cocaine also stops the reuptake of serotonin and norepinephrine.
- Combined, these effects alter mood, arousal, cognitive function, and movement (causing fidgetiness and restlessness).
Synaptic Plasticity
- While action potentials follow an “all-or-nothing” rule, synapses can change in strength, becoming stronger or weaker over time based on their usage.
- Frequent activation of a synapse increases its strength, known as Long-Term Potentiation (LTP).
- Glutamate is crucial for synaptic plasticity, which is essential for learning and memory.
- However, too much glutamate activity can damage or kill neurons, a process called excitotoxicity, which is involved in diseases like Alzheimer’s and ALS.
Action Potentials are initiated by?
voltage gated Na+ channels
what are the primary inhibitory neurotransmitter in the central nervous system?
gamma-aminobutyric acid (GABA)
Marjorie has recently had a stroke. While it appears that she understands language, she ability to speak has been impacted. Which of the following is most likely to be true for Marjorie?
Broca’s aphasia
