Information Processing Flashcards
Three phases of information processing
- Sensory Input
- Integration
- Motor Output
Sensory input
response to external and internal stimuli - Peripheral nervous system (PNS)
Integration
Interpretation of sensory input - Central nervous system (CNS)
Motor output
Conduction of signals from the integration center to the effector cells (muscle, gland cells). PNS responsible.
What conducts signals through the body?
Signals are conducted through the body by nerves.
Central nervous system composed of…
brain and spinal cord
Neuron specializes in…
Neurons specialize in transmitting chemical and electrical signals.
Neurons are comprised of
Large cell body and fibre like extensions.
Two types of fibre like extensions
Dendrites (tree) and axons
Dendrites
Dendrites are short and numerous. They receive signals.
Axons
Axons conduct impulses away from the cell body. Axons are one long process. Some axons are insulated by a myelin sheath.
What’s at the end of an axon
Synaptic Terminal
Synaptic Terminal
Located at the end of an axon, the synaptic terminal relays signals to other cells by releasing neurotransmitters. The synaptic terminal forms a synapse.
Synapse
The junction between the presynaptic and postsynaptic (effector) cells.
Glial Cells
Also called glia cells, they are supporting cells that reinforce, protect, and insulate neurons. Glial cells do not conduct impulses.
Types of Glial Cells
Astrocytes, Oligodendrocytes, and Schwann
Astrocytes
Part of the Central nervous system, they induce the formation of tight junctions in the brain like the blood brain barrier.
Blood Brain Barrier function
The Blood brain barrier prevents most molecules from entering the Central Nervous System.
Oligodendrocytes
Make up the myelin sheath within the Central Nervous system
Myelin Sheath description and function
Myelin sheath is electrical insulation that speeds up nerve impulses
Schwann
Makes up myelin sheath in the peripheral nervous system.
Nerve Signals
change in voltage caused by the movement of ions (sodium and potassium)
Why do ions move through plasma membrane?
Due to ionic gradients across the membrane.
Voltage across the plasma membrane for all cells is:
Between -50 to -100 mV
Voltage across the plasma membrane of a resting neuron is:
about -70mV
Two types of ions
Anions and Cations
Anions inside of the cell
Proteins, amino acids, sulphate, and phosphate
Anions outside of the cell
Cl-
Cations inside of the cell
High K+ and low Na+
Cations outside of the cell
Low K+ and high Na+
How do ions cross membranes?
Through integral membrane proteins.
Integral membrane proteins for ions called
Ion channels
Ion channels are what for ions?
Ion channels are selective for ions.
Two types of ion channels
Passive and gated
Passive Channels
Passive channels are open all the time and thus don’t require ATP.
Gated Channels
Gated Channels are usually closed and require a stimulus or voltage change to open them.
Describe the Resting Potential Process.
high number of passive K+ channels. K+ moves down its concentration gradient and leaves the cell, making the inside more negative and the outside more positive. Na+ also moves down its concentration gradient to enter the cell, but it does so at a much slower rate. The net flux of K+ and Na+ ions result in the -70mV resting potential.
What enzyme is essential to the Resting Potential?
Na, K-ATPase maintains the concentration gradients. Without it, a resting potential could not exist as equilibrium would be established.
What does Na, K-ATPase do?
It transports Na+ and K+ against their concentration gradients. Requires ATP.
For every turn of the Na, K-ATPase, what happens?
3 Na+ out, 2 K+ in, and ATP hydrolyzed.
Nerve impulses
Nerve impulses are changes in membrane potential.
Nerve impulses due to what?
Changes in membrane potential (nerve impulses) due to gated ion channels.
Gated ion channels cause what when open?
They cause ion diffusion
2 types of changes in membrane potential due to stimuli
Hyperpolarization and Depolarization
Hyperpolarization
K+ ion channels open due to stimulus and K+ diffuses out. More negative inside.
Depolarization
Na+ ion gated channels open due to stimulus and Na+ diffuses in. Inside less negative.
Action Potential alternative term
Nerve impulse
Action potential requires what?
Strong stimuli, threshold potential must be reached.
5 phases of the action potential
- Resting State, 2. Depolarization, 3. Action Potential, 4. Repolarization, 5. Undershoot.
Resting State
Gated Channels are closed, passive channels are open (always).
Depolarization
Stimulus causes Na+ gated channels to open, and Na+ flows in. Results in depolarization.
Action Potential
If threshold potential is reached, voltage gated Na+ channels open, resulting in a large influx of Na+. This results in a large depolarization.
Repolarization
Na+ channels close and K+ channels open and K+ flows out.
Undershoot
K+ gated channels slow to close. Charge inside of the cell more negative than resting potential (-70 mV). This period is called a refractory period, where area is insensitive to stimulus.
Where does the action potential event generally occur?
The action potential is a localized event.
Where are neurons stimulated?
At the dendrites
Action potential propagation path
Axon»_space;> Synaptic Terminal
How does the action potential propagate?
Depolarization in one area of the membrane causes depolarization in the neighboring area.
How many directions can the action potential move in? Why?
The undershoot and the resulting refractory period means that the Action potential can only move in one direction.
another term for Presynaptic cell
Transmitting Cell
another term for Postsynaptic cell
Receiving cell
How many different types of synapses are there? which one will we focus on?
Two (Chemical and electrical). We will focus on chemical synapses
Presynaptic terminal contains what?
The Presynaptic terminal contains numerous synaptic vesicles that contain neurotransmitters.
Acetylcholine
Excitatory neurotransmitter to skeletal muscles.
Postsynaptic cell contains
neurotransmitter (ligand) gated ion channels for Na+, K+ and Cl-
First step of chemical synapse
Action potential arrives at the presynaptic terminal, where it depolarizes the presynaptic membrane. This causes the voltage gated Ca2+ channels to open and Ca2+ flows in.
Synaptic cleft
Gap between the post and presynaptic terminals
Second step of chemical synapse
Ca2+ stimulates synaptic vesicles to fuse into the presynaptic membrane and release neurotransmitters into the synaptic cleft (exocytosis).
Exocytosis
Fusing of vesicle into membrane and releasing something.
Third step in chemical synapse
Released neurotransmitters bind to ligand gated ion channels on postsynaptic membrane. Effect can be excitatory or inhibitory.
EPSP
Excitatory PostSynaptic Potential - Neurotransmitter binds to postsynaptic Na+ channels, causing depolarization. If depolarization is greater than threshold potential, a new action potential occurs in the postsynaptic cell. Hence excitatory.
IPSP
Inhibitory PostSynaptic Potential - neurotransmitter binds to K+ or Cl- channels resulting in hyperpolarization of postsynaptic cell. More difficult to reach threshold, thus inhibitory.
Fourth step of chemical synapse
Neurotransmitters are quickly degraded and recycled to the presynaptic cell.
How many directions can the nerve impulses be transmitted across the synaptic clef? Why?
Only one, the presynaptic terminal does not have any ligand-gated ion channel proteins.
