Lecture 1: History and Structure and function of the nervous system Flashcards
History of Cognitive Neuroscience; is there more than the brain alone.
Monism vs. Dualism
Monoism: The brain produces behavior, thoughts and the mind (thales, willis, la mettrie, Gall)
Dualism: The mind appears from elsewhere; its something immaterial (Decartes; res cogitans vs. res extensa)
Does the brain work as one big organ or is it made up of different modules?
Functional specialization vs. Aggregate field theory
Functional specialization: different areas in the brain have different functions (Willis, Galls’ Sphrenology)
Aggregate field theory: The brain works as a whole (Flourens)
No brain area works alone!
Electrical stimulation (Fritsch & Hitzig 1870)
electrical stimulation of brain areas produces characteristic movement in dogs.
Broddmann (1909)
identification of 52 distinct brain areas with different cellular architectures.
Visualization of individual neurons
Golgi: cells in the brain form a continuous mass of tissue
Ramon Cajal: neural doctrine; neurons are discrete entities.
The cognitive revolution
not all behavior is learned (chomsky)
Instruments of Neuroscience
Angelo Mosso (1891)
pulsations of the blood in the brain is directly related to mental activity.
CNS; central nervous system
Brain (cerebrum, cerebellum, brainstem) + Spinal cord
PNS; peripheral nervous system
Nervous system that is not the brain + Spinal cord
The cells of the nervous system: 2
Neurons: transmit information
Glial cells: function depends on the type
4 types of Glial cells
- Astrocytes: blood-brain-barrier
- Oligodendroctyes: myline sheet
- microglial cells: remove damaged cells
- Schwann cells: myline sheet
Dendrites
receive input from other neurons at the dendritic spines
Axon
outputs signal to other neurons at the axon terminals
Neural signalling
resting membrane potential
when a neuron is not sending a signal, it is at rest. the neuron will have an electrical voltage of -70mV
Intra-extra cellular fluid is made of?
Ions: atoms or molecules that are either positive or negative charge.
K+ potassium
Na+ sodium
Ca2+ calcium
Chloride Cl-
Organic anions A+
ion channels
selectively permit one type if ion to pass. more pottasium K+ channels in cell membrane
Ion pumps
active transport proteins. sodium-potassium pump. pumps 3 sodium ions (Na+) out of the cell and 2 potassium ions in the cells.
Intracellular fluid
positively charged potassium ions K+ and negatively charged organic anions (A-)
Extracellular fluid
consists mostly of positively charged sodium ions Na+ and negatively charged chloride ions (Cl-)
concentration gradient
The difference in the concentration of Ka+ and Na+ inside and outside the cell.
Na+ Ka+ pump
enzyme that actively pumps Na+ out of the cell and pumps Ka+ inside the cell
electrical gradient
because the cell membrane mostly permeable to Ka+ via potassium channels, Ka+ will move from intra to extracellular space. since it is more positively charged outside the cell there is an an electrical imbalance.
electrochemical equilibrium state
The concentration gradient and electrical gradient reach a electrochemical equilibrium state. In this state the difference in electrical charge is -70mV (resting membrane potential)
The action potential
When a neuron is active (when it is passing information) the resting potential changes into an action potential.
The rapid depolarization and repolarization on the neurons output.
Dendrite spines
Neuron receives a signal at the dendrite spines. these contain channels that open when a neurotransmitter binds to the channel receptor
Ligand-gated channels
Ligand-gated channels open or close in response to the binding of specific Neurotransmitter.
Excitatory postsynaptic potential (EPSP)
temporary increase in the postsynaptic membrane potential, making it more likely for a neuron to fire an action potential, typically caused by the binding of neurotransmitters to receptors on the postsynaptic neuron.
One EPSP is not strong enough to elicit an action potential. EPSP decay fast
Inhibitory postsynaptic potential (IPSP)
temporary hyperpolarization of the postsynaptic membrane, making it less likely for a neuron to fire an action potential, usually resulting from the binding of inhibitory neurotransmitters to their receptors on the postsynaptic neuron.
decremental conduction
Decremental conduction is the gradual reduction in the amplitude of an electrical signal as it travels along a neuron
Axon hillock
If there are sufficient excitatory signals, the axon hillock will initiate an electrical signal and generate action potentials when the combined input exceeds a certain threshold.
Temporal summation
When the EPSP’s follow is close succession , the integrated potential at the axon hillock will be large enough to trigger an action potential
One
spatial summation
when different EPSP’s occur simultaneously at different locations, the integrated potential at the axon hillock will be large enough to trigger an action potential
What will happen if the strength of the EPSP is as strong as that of the IPSP
no action potential
voltage gated sodium channels
The axon hillock produces an action potential because of the voltage gated sodium channels that are present at the axon hillock. in contrast to ligand gated channels, these channels are triggered by changes in the membrane potential
Refractory period
when a neuron returns to its resting membrane potential, it undershoots to a state of hyperpolarization before returning to resting potential if -70mV. during this period the neuron cant become active again
Absolute refractory period (ARP)
Na+ are still closed so a new action potential cannot be generated.
relative refractory period
an action potential can happen but only with larger-the-normal depolarizing currents.
Myline sheets
act as insulators around the axons that allow electronic condition to travel high speeds.
Schwann cells
surround the axons with a highly insulating layer
nodes of ranvier
intervals of 1.5 mm of naked sections with no insulation. action potentials are only generated at the nodes of ranvier. between these nodes the signal is passively spread very fast speeding up conduction velocity to up to 150 m/s
Multiple sclerosis (MS)
the immune system destroys the myeline sheets of neurons. many sensory and motor functions are impaired.
synaptic transmissions
the transfer of a signal from one neuron to the other.
how do neurons communicate?
via chemical synapses
synaptic cleft
space between axon terminal of sending neuron and dendrite of receiving neuron
Presynaptic neuron & postsynaptic neuron
releases neurotransmitters in synaptic cleft that binds to specialized receptors of the receiving or postsynaptic neuron
vesicles
vesicles in the axon terminal are filled with neurotransmitter molecules
ligand gated ion channels vs. G-protein coupled receptors
ligand-gated ion channels: binding of neurotransmitter with receptor directly opens the ion channel. fast signalling in ms!
G-protein coupled receptors (GPCRs): indirect effect via a second messenger. slower signalling hundreds of milliseconds/seconds.
types of neurotransmitters
Glutamate: most prevalent neurotransmitter. excitatory. memory, cognition and mood regulation.
GABA: second most prevalent. inhibitory. slows down your brain by blocking specific signals in your CNS (calming effect)
Acetylcholine: present in neuromuscular junction. excites muscles.
Dopamine: motor control/cognition. substantial nigra and ventral tegmental area as production sites in the brain. (parkinson)
Norepinephrine (noradrenaline): arousal. locus coeruleusas production site. fight or flight response.
Serotonin: mood/cognition. raphe nucleus. (depression)
