U04 Flashcards
Genome
The entire sequence of our DNA
Connectome
The connections between our neurons
Neurons
- cell of the nervous system specialized for sending and receiving neural messages
- 100 billion, making over 100 trillion connections
Sensory neurons
carry messages from the sensory organs (eyes, tongue, skin) to spinal cord and brain
Motor neurons
carry messages from the brain and spinal cord to muscles and glands
Interneurons
within the brain and spinal cord collect, integrate and retrieve messages from various sources
Dendrites
- receives chemical messages from other neurons
- the branches are so extensive bc to increase surface are of cell to receive signals from neurons
Cell body/soma
collects neural impulses, contains the nucleus (houses DNA), sustains cell functions
Axon
transports electrical impulses to other neurons via the terminal branches
Axon terminals/terminal branches
convert electrical signals into chemical messages for other neurons
Myelin sheath
- Axon enclosed in it
- fatty layer that insulates the axons and speeds up transmission of electrical signals
- made up of glia cells
Myelination
the process of developing myelin
Glia cells
- Half of the cells in the brain
- nervous system cells that perform variety of critical support functions
- provide structural support and scaffolding for neurons (guide neurons to where they’re supposed to be)
- clean up debris(dead cells, protein clusters, etc)
- form blood brain barrier (form tight connections with blood vessels)
- They help neurons communicate with each other by helping to strengthen connections between neurons, or, on the other hand, pruning excess or weak connections necessary to make neural communication more efficient.
- supply neurons with essential nutrients and oxygen
- build insulation, critical for speedy and efficient signal transmission
Action potentials
- The way neurons talk to each other, by firing off action potentials
- generated at the junction between the axon and cell body
- then move down the length of the axon
- When a neuron is depolarized by sufficient input, it reaches a threshold for producing action potential, this is called voltage threshold
- at peak of action potential, interior of cell more positively charged than outside
- action potential is all or nothing, not stronger or weaker
Cell membrane
- thing fatty skin enclosing the neuron
- boundary between the inside and outside of the cell
- selectively permeable, allows certain ions to pass and not others
Intracellular fluid and extracellular fluid
- watery chemical soup
- contains various electrically charged particles, or ions
- intracellular (inside the cell)
extracellular (outside cell)
Resting potential
- neuron is at rest, more negatively charged particles inside cell, the imbalance between intracellular and extracellular fluid results in an electrical charge across the membrane (70 millivolts)
- neuron cannot fire action potential at this resting tate
Ion channels
- gate type structures
- when neurons stimulate another neuron’s dendrites, ion channels open up in the cell membrane at the end of axon
- allows positively charged sodium ions to pass from outside to inside of cell
Depolarization
- happens when the ions outside of the cell want to get through to the inside and the ion channels open up
- this movement causes the electrical charge across the membrane to begin to reverse
- polarize means far apart, depolarize means less far membrane, so this means that the extracellular and intracellular environment is decreasing
Voltage threshold
- When a neuron is depolarized by sufficient input, it reaches a threshold for producing action potential
- once it’s reached, these voltage gated ion channels just open wide, positively charged sodium ions come flooding in from outside
- once threshold is reached, the action potential is inevitable
repolarization
- At peak of action potential, additional channels open up that allow for another type of ion, potassium ions, to move across membrane
- they move from inside cell to outside, and negative direction comes out again
Refractory period
- after action potential, at the end of repolarization, there is a temporary dip below resting potential, this is the refractory period
- at this period, it is hard to get neuron to fire again
- this period ensures that action potential is propagated forward, bc action potential moves like a wave along the axon
Synaptic cleft
- At the end of axon, when the action potential (the electrical signal) reaches its end, the neurons don’t actually touch each other
- They are separated by the synaptic cleft
- electrical signals are unable to jump over this cleft so they are converted into a chemical one, neurotransmitters
Neurotransmitters
- electrical signals are unable to jump over this synaptic cleft so they are converted into a chemical messages, neurotransmitters
- they cross gap and bind to receptors on the postsynaptic neuron
- they don’t hang around receptors long, they get cleared out of the synaptic cleft shortly after transmitting signal
- this clearing is done in a few ways: diffusion, degradation, and reuptake
receptor
- channel in membrane of a neuron that binds neurotransmitters (receives it from the neuron across)
- binds neurotransmitters in lock and key fashion, where only a certain neurotransmitter can bind to a certain receptor
Diffusion
Way of clearing neurotransmitter out of synaptic cleft: drift away
Degradation
Way of clearing neurotransmitter out of synaptic cleft: broken down by certain enzymes around in the synapse
Reuptake
Way of clearing neurotransmitter out of synaptic cleft: reabsorbed into the presynaptic terminal branches
Excitation
- receiving neuron slightly depolarized
- excitatory currents are those that prompt one neuron to share information with the next through an action potential
- moves the neuron closer towards voltage threshold and increases likelihood of action potential
- excitatory inputs contract muscle
Inhibitation
- receiving neuron slightly hyperpolarized
- moves the neuron further from threshold and reduces likelihood of action potential
- while inhibitory currents reduce the probability that such a transfer will take place
- inhibitory inputs tell muscles to relax
GABA
- A type of neurotransmitters within a class of it
- GABA is within amino acids
- Binds to major inhibitory receptors; influences muscle tone
Acetycholine
A class of neurotransmitters
- Binds to both inhibitory and excitatory receptors; contributes to muscle control
Monoamines
A class of neurotransmitters, includes norepinephrine, serotonin, dopamine
Neuropeptides
A class of neurotransmitters, includes endorphins