Fundamentals of the nervous system Flashcards
What are parts of the body and functions are in CNS and PNS
CNS
- brain and spinal cord
- Integration and control centre
PNS
- Cranial nerves & spinal nerves
- Communication between CNS & rest of body
What are the 2 principal cell types in the nervous system
Neurons: Excitable cells that transmit electrical signals
- Mass is far greater
Neuroglia: supporting cells (6 types)
- # is greater
What cells are in the CNS & PNS
CNS
- Astrocytes
- Microglia
- Ependymal Cells
- Oligodendrocytes
PNS
- Satellite cells
- Schwann cells
What are astrocytes (star-shaped)
- guide the migration of neurons & formation of synapses
- Tight junctions and basal lamina of the cerebral endothelial cells (cells line blood cells) play an important role in blood brain barrier
What are microglia
- Migrate toward injured neurons
- Phagocytize microorganisms & neuronal debris
What are ependymal cells
- ciliated cells that circulate CSF
- Produce CSF
What are oligodendrocytes
Forms myelins that gives impermeable membranes to axons
What are satellite cells (PNS)
- Control microenvironment around cell body
- Similar to astrocytes in CNS
What are schwann cells (PNS)
Most form myelin sheaths
What is the function of myelin sheaths
- Protect and electrically insulate axon
- Increase speed of nerve impulse
What is the neurilemma? which nervous system is it in?
Peripheral bulge of schwann cells in PNS
What are Nodes of Ranvier?
What effect does it have?
Gaps between the myelin sheaths
- Make AP go faster, also increasing diameter
Where are the voltage gated channels in a neuron
In the axon NOT cell body
What are clusters of cell bodies called in CNS and PNS? and processes in each?
CNS: nuclei; tracts
PNS: ganglia; nerves
What is the function of dendrites?
Receive input as graded potentials (short distance signals)
Where can graded potential be found? action potential?
GP: cell body + dendrites
AP: axon
What is the role of telodendria?
Synapses with synaptic terminals
What are the functions of axons? Name and explain the 2 directions in trafficking.
Anterograde: away from cell body
- Kinesin motor
- Mitochondria, enzymes
Retrograde: toward cell body
- dynein-dyactin motor
- viruses, toxins
Which type of neurons do not generate AP and are unmyelinated
Bipolar neurons
Which type of cell is mainly found in PNS
unipolar, function as sensory neurons
What are the functional classifications of neurons
SENSORY (afferent): transmit impulses from sensory towards CNS
MOTOR (efferent): carry impulses from CNS to effectors
What is Ohms law equation
Current = voltage/resistance
Contrast between the 3 gated channels
Chemically (ligand) gated channels
- open with binding of a specific NEUROTRANSMITTER
Voltage-gated channels
- open & close in response to changes in MEMBRANE POTENTIAL
Mechanically gated channels:
- open & close in response to physical deformation of receptors
What are factors that influence RMP
- Impermeable to negatively charged proteins
- Slightly permeable to Na+ (Na+ leakage channels)
- 25-100 times more permeable to K+ (K+ leakage channels)
- Freely permeable to Cl-
- Differences in ionic composition of ICF and ECF
- Differences in PM permeability
How do you generate a resting membrane potential?
- K+ ions diffuse in their leaky channels to outside: results in a negative charge in inner membrane
- K+ ions also move inside the cell as they are attracted to the - charge in the inner membrane
What are the requirements for generating a resting membrane potential
- Na+/K+ pump: pump more cations out
- The concentration gradient of K+
- Higher permeability to K+
- Membrane impermeable to anionic proteins
When does membrane potential change?
- when concentrations of ions across membrane changes
- membrane permeability to ions changes
What is a graded potential? what is it triggered by? What sections of the graph does it result in?
-an incoming signal operating over a short distance
- triggered by stimulus that opens gated ions channels
- Results in depolarization and hyperpolarization
What are long-distance signals called? What does it trigger to open?
Action potential
- triggers to open specific voltage gated channels
What are the states of the 2 activation gates at rest? What causes them to change?
Activation gates:
- closed at rest
- open with depolarization to allow Na+ to enter
Inactivation gates:
- open at rest
- block channel once it is opened to prevent more Na+ from entering
What occurs with the gates in depolarization
- Activation and inactivation gates open
- sodium enters
- increases membrane potential
What occurs with the gates in repolarization
- Inactivation gates close
- Activation gates stay open
- Sodium stops entering
- Potassium leaves
- mV decreases
What occurs with the gates in hyperpolarization
-Activation gates close
- Inactivation gates open
- Potassium is still exiting
What is the absolute refractory period
- time when Na+ channels open until channel resets (depolarization)
- ensure all-or-none
What is the relative refractory period
- repolarization + hyperpolarization
- threshold to get an AP is elevated in this period
What is the role of the Na/K pump?
Ionic redistribution
How does CNS determine stimulus intensity?
Frequency/height
by frequency
What is the effect of large diameters in an axon?
Less resistance, faster impulse conduction
What is the rate-limiting step in information transfer in chemical synapses
Synaptic delay
What are the steps for info transfer across chemical synapses.
- AP arrives at axon terminal
- Ca2+ enters axon terminal via voltage gated Ca2+ channels
- Ca entry causes synaptic vessels containing neurotransmitters to exit via exocytosis
- Neurotransmitter diffuses into synaptic cleft and binds to specific receptors
- Binding of neurotransmitter opens ion channels resulting in GRADED POTENTIAL
- Neurotransmitter effects terminated by reuptake of transport proteins and enzymatic degradation
For electrical synapses, how are neurons electrically coupled?
via gap junctions
What is the role of EPSP
- allow flow of Na+ and K+ in opposite directions
- allows more + membrane potential (Na+ influx> K+ efflux) (net depolarization)
- help trigger AP
What is the role of IPSPs
- Allow flow for either K+ out or Cl- in
- Causes a hyperpolarization (more - mV)
- reduces ability to produce an AP
What is the difference between temporal and spatial summation
Temporal summation
- Impulses in rapid-fire order
- 1 entry
Spatial summation
- Impulses at the same time
- more than 1 entry
What occurs in an axoaxonic synapse
release of an excitatory neurotransmitter may be inhibited by activity of another neuron
What are the 6 neurotransmitter classes
- ACh
- Biogenic amines
- Amino acids
- Peptides
- Purines
- Gases (inhibitory or excitatory) & lipids (inhibitory)
What neurotransmitter and class is involved in wakefulness
NE & E
Biogenic amine
What are the neurotransmitters of excitatory and inhibitory of amino acids. 2 of each. Where does it work?
GABA (inhibitory) in brain
Glycine (inhibitory) in spinal
Glu: principal excitatory
Asp
What is the role of neurotransmitter adenosine? Whats the class
Purines
Potent inhibitor in brain
(how caffeine works)
Contrast between discharge zones and facilitated zones
Discharge zone:
- closest to incoming fibre
- immediate fast response
Facilitated zone:
- farther away from incoming fibre
- requires more stimulation
Which receptors have an indirect action
G Protein-linked receptors
Differentiate between diverging circuit and converging circuit
Diverging
- 1 input, many outputs
- Amplifying
Converging
- many inputs, 1 output
- concentrating
Differentiate between serial processing and parallel processing
Serial
- 1 pathway
-Simple
Parallel
- multiple pathways
- higher level function
What receptors have a direct action?
Which ions do the excitatory and inhibitory receptors allow in this receptor?
channel-linked receptors
Excitatory: Na+ influx
Inhibitory: Cl- influx, K+ efflux
What is the neuron cell body called
What are the bodies called in this area
Perikaryon
Nissl bodies
