CSA 1 Flashcards
What is the CNS and its main function?
Central Nervous System is the brain and spinal cord, used for information processing, including reflexes and behavior
What is the Peripheral Nervous System and its main function?
Includes cranial nerves and spinal nerves, used for sensory detection and motor activation
What is the nervous system (mostly) derived from?
Ectoderm
Define Afferent and Efferent
Afferent- Towards Spinal Cord (first letter)
Efferent- Away from spinal cord (exit)
What is a ganglion?
A group of cell bodies outside the CNS. Inside CNS, they are called a nucleus.
What are autonomic ganglion?
Near certain glands and inside organs such as heart
What are parasympathetic ganglion?
smaller neurons, eccentric nuclei
What are dorsal root ganglion?
Sensory, big neurons, central nuclei
What is the term for anterior in human prefrontal cortex?
Rostral
What is the term for superior in human prefrontal cortex?
Dorsal
What is the term for inferior in human prefrontal cortex?
Caudal
What is the term for posterior in human prefrontal cortex?
Dorsal
How are Brodmann Areas numbered?
By cellular architecture
What are Brodmann Areas of the Neocortex/cerebral cortex?
Regions of the cortex numbered 1-52. Each has a particular set of inputs and outputs, and often will have a function.
Name the parts of a neuron.
Input to Dendrites, then cell body, then Axon hillock, then Axon covered with myelin sheath, breaks in myelin for axon colaterals and Nodes of Ranvier, then axon terminal for output ending in synaptic boutons
Describe myelin
hydrophobic lipid layer, provide insulation to increase conduction
What does increasing axon diameter do?
Increases signal speed
How are neurons classified?
multipolar, bipolar, unipolar. All have 1 axon.
What type of neuron are most neurons?
Multipolar: several dendrites
What are pyramidal cells, where are they, and what do they do?
Multipolar neuron shaped like a pyramid in the cerebral cortex, for thinking
What are purkinje cells, where are they?
Multipolar neuron in cerebellum
What are dorsal root ganglion, where are they, and what do they do?
very large pseudounipolar neurons with large nuclei and a single nucleolus, afferent inputs to spinal cord, for sensory information
What are bipolar neurons and where are they located?
Neurons with One Dendrite and One Axon, Retina and Cochlea
What are pseudounipolar neurons?
Look like they only have one pole, but have two poles (likely side by side)
What are unipolar neurons and what is an example?
Only one output, no input/Dendrite, Rod or Cone in Retina
Describe the chemical synapse.
Synapse = functional link. Presynaptic cell releases vesicles filled with neurotransmitter into a 30nm gap, diffuse across and are taken in by by receptor into postsynaptic cell (neuron, myocyte, gland) and initiate electric signal down the postsynaptic cell.
What is divergent signalling and what is an example?
A single neuron sends a signal to many neurons, eg skin
What is convergent signalling and what is an example?
Multiple inputs influence a single neurons, eg retina
What are interneurons and where are they located? Where do they send and receive signals?
Relay/Connector, Association, Intermediate/Local Circuit Neurons. Neither sensory nor motor, only in CNS. Receive from sensory or interneurons, send to motor or interneurons. Most central processing is by interneurons.
How are glia different from neurons?
Glia: No action potentials, do not form synapses, are able to divide, form the myelin sheath, common source of tumors in nervous system
What is the only area where neurons generally can divide?
Hippocampus
Why is PNS an ambiguous acronym?
Peripheral Nervous System or Parasympathetic Nervous System
What is a more appropriate name for basal ganglia, that they do not have?
Basal Nuclei
What is the ratio of Neurons to Glial Cells
1 : 10-50
Name the 4 types of glia of the CNS.
Ependymal Cells, Astrocytes, microglial cells, oligodendrocytes.
How do oligodendrocytes interact with neurons?
One oligodendrocyte myelinates multiple axons but each axon needs many oligodendrocytes to myelinate it.
What are the shape and functions of an astrocyte?
Star-shaped, interdigitate with cells to support them, influence blood flow and blood brain barrier (“feet” on processes about vessel endothelium), assist neuronal development/growth, protect neurons from harmful substances
Name the 2 types of glia in the peripheral nervous system.
Schwann cells, and Satellite cells.
Describe microglia and their function.
Act as immune cells, protect neurons from disease, migrate to injury sites, engulf microbes/debris, mesodermal origin.
Describe Ependymal Cells.
Lines areas of CSF including brain’s ventricles and central canal of spinal cord, form CSF. Have cilia + microvilli on apical membrane (towards lumen) to move cells.
Describe schwann cells.
Production/Maintenance of myelin in peripheral nervous system. 1 axon per schwan cell and vice versa.
Describe Satellite cells.
Supports neurons, regulates exchange of materials between neurons and interstitial fluids. Analagous to astrocytes.
What are gliomas?
Largest group of primary tumors derived from glial cells, usually highly malignant, grow rapidly, usually inside cranium and difficult to remove completely with surgery.
What are neuroblastomas?
Tumor derived from neural crest cells from sympathetic nervous system, most common in children and infants, outside cranium, often secrete catecholemine, survival rates vary depending on type, initial prognosis very good if caught early, but neurological problems often develop ~30 years later, treatment depends on type.
Describe electrical signals in 5 ways.
Faster (do not require conformational changes), bidirectional, much smaller gap 3.5 nm, no plasticity, no amplification
What does it mean to have no amplification in electrical synapse?
Resistance weakens signal as it is transmitted. Signal will not transmit if post-synaptic cell is much bigger than pre-synaptic cells.
Define spatial summation.
A neuron determines whether to fire based on adding together many inhibitory and excitatory signals received from several other neurons. Small depolarisations, if there are many, can reach threshold (convergent signalling).
Define temporal summation.
When the input neuron is firing fast enough that the receiving neuron can add together the many small signals, reaching threshold (if the recovery and depolarisation frequency of input is much faster than receiving neuron’s ability to recover from a small depolarisation, and is still highly depolarised)
What is threshold for depolarisation?
-55 mV
What is the overshoot voltage?
Above 0 (+40 mV as an example)
What is the equilibrium potential?
-70 mV
How fast are cardiac action potentials vs neuronal action potentials?
300-500 mS vs. 5 mS
What are inward rectifiers?
K+ channels open at rest, K+ flows out as dominant current, resting membrane potential near equilibrium -70mV
What does the initial depolarisation cause?
Na+ channels to open, Na+ flows into cell, meaning more depolarisation/positive feedback
What happens when voltage goes above the threshold value?
Cell committed to Action Potential (all-or-nothing)
What 2 things happens during repolarisation?
Na+ channels inactivate, Delayed rectifier K+ channels open about 1ms
What happens in after hyperpolarisation?
Inward rectifier K+ channels open, but Na+ channels are still recovering/not yet open
How can you increase firing frequency of a neuron?
Lower the threshold by inactivating a small number of sodium channels (by slightly increasing long-term voltage). This lessens positive feedback.
What is excitability?
How easy it is to start nervous signalling (sensitivity in neurons, irritability in muscles). Too much leads to seizure or muscle spasms. Basis of psychotropic drugs.
When is a channel closed vs inactivated?
Closed inside is negative, inactivated inside is positive and after a delay
What is extracellular fluid in terms of voltage?
Same everywhere, considered the ground, called zero
How does Ca2+ enter the cell and what effect does it have?
Passively, when channels open, makes cell positive
Increased permeability to Na+ and K+ does what to cell?
Na+ makes cell more positive, K+ makes cell more negative
What is lidocaine/lignocaine and how does it work?
Local anaesthetic applied topically, lowers excitability by raising the threshold, which stops action potentials. Done by blocking a small percent of sodium channels
What is carbamazepine?
Anticonvulsant, blocks sodium channels, raises AP threshold/lowers excitability
What is an example of an antiarrhythmic drug and how does it work?
Quinidine, works by lowering conduction velocity, extending the refractory period
What is tetrodotoxin (TTX)?
Poison found in liver of pufferfish/fugu fish liver,
How do sulfonylureas work?
Manage type 2 diabetes by inhibiting K+ channel to increase excitability of pancreatic beta cells, increasing insulin secretion
What are the forces acting on each ion?
Chemical/diffusion force and electrical force based on voltage
What is another term for equilibrium potential?
Reversal Potential
E Na
+60mV (a NAg retires early at 60)
E K
-90 mV (a King will die at 90)
E Ca
+123 mV (a CAt is easy as 1-2-3)
E Cl
-40 mV, -65 in neurons (A CLub for fighting Ali Baba’s 40 thieves)
What is a graded potential?
Electrically localised, lasts a long time, but conducted almost instantly, and flatter in shape. In rods and cones.
What is saltatory conduction?
Combination of graded potentials followed by slow APs (requires conformational changes of ion channels). Net effect is faster conduction velocity as length between nodes increases. If too long, voltage dies out.
Where are conduction tests and myelination tests useful?
Multiple Sclerosis, paraesthesis, numbness, tingling, burning, peripheral neuropathy, spinal disc herniation
What are typical conduction velocities?
100 m/s myelinated alpha motor fibres, 1 m/s for unmyelinated c nociceptive fibres
What is the normal volume of CSF in the brain?
150 mL
How much CSF is produced in 24 hours?
450-500 mL
What makes CSF?
Choroid plexus
What can cause expanded ventricular system/more CSF?
Obstruction to CSF flow, scarring around arachnoid granulations, shrinkage of the brain
What can raise intracranial pressure?
Swelling of the brain, lesion, or obstruction to CSF flow
What causes hydrocephalus?
Failure to fuse
What is the condition resulting from failure of spinal cord to fuse posteriorly?
Arnold-Chiari malformation
