Neuroscience Flashcards
(9 cards)
Know the organization of the nervous system, the types of cells and what each cell type does
Nervous System
- CNS (Central Nervous System)
- Brain
- Spinal Cord
- PNS (Peripheral Nervous System)
- Motor
- Sensory
- Autonomic
- Somatic
Cells of the Nervous System
Neurons
-Send and receive electrical input
-Comprised of : soma (cell body), dendrites (receive info), axon (send signal)
-Axon of hillock and axonal terminals
-Axonal bundles form nerves
-Gila “glue”
-More numerous than neurons 50:1, may function as stem cells
-Astrocytes: metabolic support of neurons, form BBB (blood brain barrier), maintain conc. Gradients
-Mircroglia: remove cell debris
-Oligodendrocytes: produces myelin sheath in CNS which contains nodes of Ranvier (interrupted segments)
-Schwann Cells: glial cells of PNS
Know the difference between sensory, inter and motor neurons
- 1) Sensory – afferent Nuerons receive information and transmit to brain or spinal cord
- 2) Motor Nuerons – efferent neuron
- 3) Interneurons (association) – integrate information coming from a variety of neurons will stimulate motor neurons
How is the membrane potential established? What is an electrochemical gradient? What does equilibrium potential refer to? What does it indicate?
- Membrane Potential
o The difference in charge from the inside of cell compared to the outside
o Due to differing ion concentrations and plasma membrane
o Polarized - Resting
Electrochemical Gradient
- Combined effect of electrical and chemical gradient
Equilibrium Potential
- Opposing forces of chemical and electrical gradients can create an equilibrium where there is no net movement
How is an action potential generated? Describe IN DETAIL the steps of the action potential and the propagation down the axon. What would happen if any of the gates did not function as they should?
• How is an action potential generated? Describe IN DETAIL the steps of the action potential and the propagation down the axon. What would happen if any of the gates did not function as they should?
Action Potentials
- Carry electrical signal along an axon
- Always the large same amplitude depolarization
- All or none – cannot be graded
- Actively propagated – regenerates itself as it travels
Action Potential Sequence
- Begins when graded potential depolarizes to threshold potential (-50 mV)
- Voltage gated Na+ channels open triggering action potential
- Na+ rapidly diffuses into cell causing characteristic spike
- Inactivation gate in Na+ channel swings shut when membrane sufficiently positively polarized (will not reopen until resting potential restored)
- Voltage gated K+ channels also opened by threshold potential but 1 msc later than Na+ channels
- K+ leave cell and membrane becomes negative again
- So many K+ leave that membrane hyperpolarizes
- Voltage gated K+ channels close and resting membrane potential restored
- Evolution of K+ channels with a slightly slower opening time than Na+ channels was a key event that led to the formation of nervous systems
- If both opened at the same time, they would negate each other’s effects
- Absolute refractory period
- Cell unresponsive to another stimulus due to Na inactivation gates being closed
- Limits frequency of action potentials
- Ensures action potential does not move “backward”
Conduction
- Graded potentials reach threshold potential at axon hillock
- Triggers opening of voltage-gated Na+ channels just beyond hillock region
- Depolarizes area farther along axon
- Sequential opening of Na+ channels conducts a wave of depolarization from axon hillock to axon terminal
- Inactivation gate of Na+ channels prevents backward movement toward cell body
Describe saltatory propagation? Why is is beneficial to have myelinated axons? What else affects the speed of propagation?
Saltatory conduction – jumping of the action potential
Speed Varies based on
- Axon Diameter
- Myelinations
o Myelinated faster than unmyelinated
o Oligodendrocytes and schwann cells make myelin sheath
o Not continuous – nodes of renvier
o Salutatory conduction – jumping of action potential
Know the difference between a chemical and electrical synapse. Which is faster? Why?
An electrical synapse
An electrical synapse is a mechanical and electrically conductive link between two abutting neuron cells that is formed at a narrow gap between the pre- and postsynaptic cells known as a gap junction. Each gap junction contains numerous gap junction channels which cross the membranes of both cells. With a lumen diameter of about 1.2 to 2.0 nm, the pore of a gap junction channel is wide enough to allow ions and even medium sized molecules like signaling molecules to flow from one cell to the next thereby connecting the two cells’ cytoplasm. Thus when the voltage of one cell changes, ions may move through from one cell to the next, carrying positive charge with them and depolarizing the postsynaptic cell.
Gap junction channels are composed of two hemi-channels called connexons in vertebrates, one contributed by each cell at the synapse.
A chemical syapse
The space between a chemical syapse is much larger than an electrical synapse.
The release of a neurotransmitter is triggered by the arrival of a nerve impulse (or action potential) and occurs through an unusually rapid process of cellular secretion, also known as exocytosis: Within the pre-synaptic nerve terminal, vesicles containing neurotransmitter sit “docked” and ready at the synaptic membrane. The arriving action potential produces an influx of calcium ions through voltage-dependent, calcium-selective ion channels. Calcium ions then trigger a biochemical cascade which results in vesicles fusing with the presynaptic-membrane and releasing their contents to the synaptic cleft.
An electrical synapse is faster than a chemical synapse but chemical synapases are far more common.
What do acetylcholine and GABBA? are they excitatory or inhibitory?
GABBA – Gamma-aminobutyric Acid – Direct or indirect (G proteins) depending on type of receptor. CNS: cerebral cortex, cerebellum, interneurons throughout brain and spinal cord. Direct inhibitory effects: opens CL channels; indirect effects opens K+ channels and blocks entry of Ca2+.
Acetycholine (ACh) – Primarily direct, through binding to chemically gated channels. CNS: synapse throughout the brain and spinal cord, PNS: Neuromuscular junctions, neuroglandular junctions, and synapses in autonomic ganglia. Widespread in CNS and PNS; best known and most studied of neurotransmitters. Both excitatory and inhibitory
What are the different types of stem cells? Which are most differentiated? What is the current state of stem cell technology (i.e. what can researchers do with these stem cells, where can they get them and what might they be used for)?
- Neural Stem Cells (NSC) – proliferate and differentiate early development to neurons, oligos, and astrocytes
o Totipotent cells: cell can become any cell in body: ex. Zygote, can make new organism
o Pluripotent cells: can become any of the 3 gem layers, not extra-embryonic tissue such as the placenta
o Multipotent: can give rise to multiple cell types - Embryonic stem cells: pluripotent cells from inner cell mass of blastocyst (4-5 dpf)
- Adult Stem cells: somatic stem cells, may be pluripotent
- Have been able to generate pluripotent cells from multipotent cells. Problem: tumorigenic, may lack potency of embryonic stem cells
Because stem cells can become bone, muscle, cartilage and other specialized types of cells, they have the potential to treat many diseases, including Parkinson’s, Alzheimer’s, diabetes and cancer. Eventually, they may also be used to regenerate organs, reducing the need for organ transplants and related surgeries.
describe the current technology of prosthetics and neuroprosthetics
Prosthesis – an artificial device that replaces a missing body part
Biomechatronics – the science of using mechanical devices with human muscle, skeleton, and nervous systems to assist in motor control
- New development of prosthetic controlled by implanted electrodes
- osetointegration directly connects the prosthetic to the bone
