Neuro System Physiology 1 Flashcards
List the 3 unique parts of a neuron
Long cell process (axon), short cell processes (dendrites), and specialized cell junctions (synapses)
What are the parts of the Synapsis?
Terminal Bouton, Presynaptic Membrane, Synaptic cleft, postsynaptic membrane, and neurosecretory vesicles
What are the types of neurons?
Bipolar (e.g. CNS cells), Unipolar (e.g. sensory neurons), and Multipolar (e.g. motor neurons)
What is myelin?
Layers of lipid-rich insulation wrapped around an axon
What is myelin’s function?
To increase signal conduction speed along an axon
Which specialized support cells are responsible for myelin?
Oligodendrocytes in the Central nervous system and Schwann cells in the Peripheral nervous system
What is the space between units of myelin called?
Nodes of Ranvier
Where are nodes of Ranvier more apparent?
In the CNS. In the PNS the bare segments are partly covered by cytoplasm from Schwann cells.
True or False: One Schwann cell will produce the myelin for multiple PNS nerves’ axons.
False, Oligodendrocytes in the CNS produce myelin for multiple nerves’ axons, but Schwann cells in the PNS remain affixed to only one neuron’s axon
What are non-neuron support cells in the CNS called?
The glia
What cells make up the glia?
Astrocytes, Oligodendrocytes, Ependyma, and Microglial cells
What are the functions of an Astrocyte?
They guide developing neurons into place during embryo development, give structure for specialized cells to exist in, and some move fluid, glucose, and ions from the local capillaries to neurons
What is the function of Ependymal cells?
They are simple cuboidal cells in the spinal cord and ventricles of the brain - that along with capillaries - form the choroid plexus. Both the choroid plexus and ependymal cells lining produce cerebrospinal fluid
What is the function of Microglia cells?
They are specialized macrophage immune cells of the CNS
From the skull moving into the brain, what are the 3 parts of the meninges?
Dura, Arachnoid, and Pia
Where do you find the main veins and arteries of the brain and the cerebrospinal fluid?
They are found in the subarachnoid space between the Arachnoid and Pia
Efferent nerves are made up of what?
Motor
Autonomics
Afferent nerves are made up of what?
Sensory and Somatic
What ion is high outside the cell?
Sodium
What ion is high inside the cell?
Potassium
What establishes the electrical gradient?
Na+/K+ ATPase pump
How many ions are pumped in and out?
Three Na+ out, Two K+ in
What is the role of the large anions trapped inside the cell?
They help generate resting membrane potential by being negative on inside compared to outside. They attract K+ to line up on membrane on outside
What factors are necessary for establishing the resting membrane potential?
(1) Selectively permeable membrane
(2) A gradient maintained by Na+/K+ ATPase pump
(3) Large anions inside cell
Influx of Na+ into the cell such that inside becomes less negative is known as what?
Depolarization
What 2 neurotransmitters lead to depolarization?
Acetylcholine and glutamate. These are both excitatory neurotransmitters.
What two ionic events establish the phase of repolarization?
(1) Na+ stops coming into the cell (active closure of Na+ gated channels)
(2) K+ starts to slowly move out
What is Hodgkins cycle?
With a little depolarization Na+ gated channels are open and we get an influx of Na+ which causes more gated channels to open etc.
What stops the Hodgkins cycle?
Active closure of gated channels
What ionic event accounts for hyperpolarization, the situation in which the membrane becomes temporarily more negative than a resting membrane?
The slow closing of K+ gated channels
The point at which an action potential is generated is known as what?
Threshold
Passive diffusion of ions through the axon providing local circuit currents is known as what?
Electrotonic conduction
What 3 factors affect membrane excitability?
(1) High extracellular calcium which decreases Na+ influx
(2) A decrease in extracellular K+ which means more K+ will leak out down gradient via K+ leak channels making the inside of the cell more negative and hyperpolarized
(3) Local anesthetics
The process in myelinated axons where the electrical conduction flows from node to node rather than down the membrane is known as what?
Saltatory conduction
What is released when an action potential reaches the terminal bouton?
Calcium
The binding of Ach to the cholinergic receptor on the post synaptic membrane causes what?
The post synaptic membrane to become permeable to Na+ which influxes through open channels
What does acetylcholine esterase do?
It breaks down Ach thus stopping the synaptic signal
What kind of neurotransmitter causes hyperpolarization of the post synaptic membrane?
Inhibitory neurotransmitters
What 2 neurotransmitters lead to hyperpolarization?
Gama-aminobutyric acid (i.e. gaba) and glycine
Give an example of an inhibitory neurotransmitter?
gaba
What are the two precursors for Ach?
Acetyl-CoA and Choline
What breaks down norepinephrine?
Monoamine oxidase (mao)
What ionic movement marks an inhibitory post synaptic potential? What is the net result?
Chloride into the cell
Potassium out of the cell
Net result is hyperpolarization
What post synaptic potential is always excitatory, always suprathreshold and always leads to an action potential?
End Plate Potential
What do we call a situation in which synapses fire at the same time in order to reach threshold?
Temporal summation
A situation in which the synapses have to be close to the axon hillock before depolarization can take place is known as what?
Spatial summation
What 3 kinds of information is supplied by sensory receptors?
Type of stimuli
Location of stimuli
Intensity/duration of stimuli
What type of sensory receptor senses touch, pressure, position sense?
Mechanoreceptors
What type of receptors sense light?
Photoreceptors
What type of receptor senses pain?
Nociceptors
What type of receptors sense taste, smell?
Chemoreceptors
What does it mean when we say that the receptor potential is graded?
The greater the intensity of the stimulus the greater the depolarization of the sensory receptor nerve endings
The greater the amplitude of the receptor potential then the greater the frequency of action potentials up afferent nerves is known as what?
Frequency code
True or false: Receptor potentials are graded. Action potentials operate on an all or none principal.
True
