Unit 1 Flashcards
Information comes into the neuron from projections called
Axons
The junctions through which information passes from one neuron to another are called
Synapses
Presynaptic neurons release molecules called ________ to signal onto postsynaptic neurons
neurotransmitters
Glia
Non-neuronal cells
CNS contains
Astrocytes, oligodendrocytes, microglia, and ependyma
PNS contains
Satellite and Schwann cells
CNS Is composed of
brain and spinal cord
PNS is composed of
nerves
Neuron
specialized cells that conduct and process information, enabling thought, perception, and control of movement
Action Potential
signals are transmitted by a change of membrane voltage within a neuron
Neurotransmitters are
chemicals
Synaptic plasticity
The strength of synaptic connections can be modified by neuronal activity
Neuronal membrane
Barrier
Soma
cell body
Axon
sends information
Dendrite
receives information; “antennae” of neurons
Synapse
communication sites between neurons
Neuronal Membrane thickness
5 nanometers (nm)
Neuronal Membrane is composed of
phospholipid bilayer that is hydrophilic on outside, and hydrophobic on inside
Neuronal Soma size
5-50 micrometers μm
Cytosol
watery fluid inside the cell
Organelles are
membrane-enclosed structures within soma
What are the organelles inside the soma
Ribosomes, endoplasmic reticulum, golgi apparatus, mitochondria
Ribosomes
major site for protein synthesis
Endoplasmic Reticulum & Golgi Apparatus
sits for sorting proteins for delivery to different cell regions
Mitochondria
site for cellular respiration/generating ATP
Cytoplasm
contents within a cell membrane, excluding the nucleus
Nucleus
contains DNA, is the site for gene expression, transcription and RNA processing
Cytoskeleton
supports the cell shape; internal scaffolding
Cytoskeleton consists of
Microtubules, neurofilaments, microfilaments
Microtubules
20 nm, largest diameter, tubulin based
Neurofilaments
10nm, intermediate diameter
Microfilaments
5 nm, smallest diameter, actin based
Microtubules are located in
Dendrites & axons
Neurofilaments are located in
Axon & soma
Microfilaments are located in
the lining of the entire cell
Axon length
Up to 1 meter
Axon hillock
Beginning
Axon terminal
end
Differences between cytoplasm of axon terminal and axon
- no microtubules in terminal
- presence of synaptic vesicles in terminal
- abundance of membrane proteins
- large number of mitochondria
Signal transformation
electrical –> chemical –> electrical
Dendritic spines
postsynaptic sites, receiving signals from axon terminals
Projection neurons
- Principal neurons
- send an axon out of where the somata are located
Intrinsic neurons
- Interneurons
- make synapses within the structure where their soma is located
Cortex
80% are projection neurons with majority being pyramidal neurons
Cerebellum
Purkinje cells (projection); granule cells (interneuron)
Retina
Retinal ganglion cells (projection); bipolar cells (interneuron)
Cell type
defines a group of neurons that carry out a distinct task
Intracellular and extracellular fluids contain
water and ions
Membrane potential
the voltage across the cell membrane at any moment
Resting membrane potential
the membrane potential when the neuron is not “excited” or “fired”
In neurons, the value of the resting membrane potential is between
-40 mV and -90 mV
Steps of electrophysiology
- insert a microelectrode into the cell
- connect microelectrode to voltmeter which measures the potential cell difference between inside and outside the cell
3 factors for resting membrane potential
- intracellular potassium concentration is HIGH
- extracellular potassium concentration is LOW
- cell membrane is selectively permeable to potassium ions
*sodium is the opposite
The Nernst equation calculates
the equilibrium potential for an ion (the electrical potential that exactly balances a concentration gradient for that ion)
Neuronal membranes are permeable to more than one type of ion true or false
True
Goldman equation considers
the membrane permeability of various ions
Goldman equation describes a _________ condition that is a __________ among several equilibrium potentials.
steady-state ; “compromise”
Hyperpolarization
a change in membrane potential that makes the inside of the cell more negative
Depolarization
a change that makes the inside of the cell less negative
Discovered action potential
Sir John Eccles, Alan Lloyd Hodgkin, Andrew Huxley
Voltage-gated ion channel steps
- Transmembrane
- Ion Selectivity
- Open states depend on depolarization
Voltage-Gated Sodium Channel
- open fast
- open for a short period
- inactivate during prolonged depolarization (cannot be opened again immediately by depolarization)
Voltage-Gated Potassium Channel
- open slow
- stay open for longer
- do NOT inactivate
Tetrodoxin (TTX)
- puffer fish
- Clogs Na+ permeable pores
- Blocks all sodium-dependent action potentials
- lethal dose is 0.33 mg/kg
Batrachotoxin
- poison dart frogs
- blocks inactivation so channels remain open
Aconitine
- Flower buttercups
- Blocks inactivation so channels remain open
Threshold
The level of depolarization that must be reached in order to trigger an action potential
Action potential generation is the
process by which a neuron rapidly depolarizes from a negative resting potential to a more positive potential
Action potential generation is achieved by
the movement of ions through voltage-gated ion channels
- Resting state
- the initial membrane potential is -70mv
- both voltage-gated NA and K channels are closed
Steps of generating action potential
- Resting State
- Depolarization
- Rising phase
- Falling phase
- Undershoot
- Depolarization
- membrane becomes depolarized
- NA+ channels open and Na+ enters the cell
- if threshold is reached, action potential is triggered