Neuroscience Revision Flashcards
Somatic NS function…
- SNS Afferents function…
- SNS Efferents function…
- Somatic NS - skeletal muscle for voluntary control of body
- SNS Afferents - Relay sensation from body to CNS
- SNS Efferent - Send out commands from CNS to body for muscle contraction
Visceral NS function…
- VNS Afferent function…
- VNS Efferent function…
- Visceral NS - involuntary control of the body
- VNS Afferent - Relay sensation from viscera, blood vessels to CNS
- VNS Efferent - sympathetic (fight or flight) and parasympathetic (rest and digest)
Somatic NS efferent go…
Visceral NS efferent go…
- SNS - Straight to the muscle
- VNS - have pre-ganglionic fibres (myelinated) with synapse with post-ganglionic fibres (unmyelinated)
Who used the giant squid axon to look at ions involved in action potential
Hodgkin and Huxley
Failure of neural tube to close at caudal end…
Failure of neural tube to close at rostral end…
What can be used to prevent these conditions?
- Caudal = Spina Bifida
- Rostral = Anencephaly
- Prevention = Folic acid
Primary brain vesicles
- Prosencephalon
- Mesencephalon
- Rhombencephalon
Secondary brain vesicles
- Telencephalon
- Diencephalon
- Mesencephalon
- Metencephalon
- Myelencephalon
What cells form CSF?
What is the function of CSF?
What vertebrae would you go between for a lumbar puncture and why?
- Choroid Plexus
- Provides mechanical and immunological to CNS
- Needle inserted between L3 and L4 because the spinal cord ends before this point
External hydrocephalus
Internal hydrocephalus
- External = build up of CSF in sub-arachnoid space
- Internal = build up of CSF within brain ventricles
4 divisions of brain
- Brainstem
- Cerebellum
- Diencephalon
- Cerebrum
Brainstem components
- Medulla Oblongata
- Pons
- Mesencephalon
Olives
- Found in medulla
- Send fibres to cerebellum
Superior Colliculi
Inferior Colliculi
Superior = visual reflexes Inferior = auditory reflexes
Substantia Nigra and Nucleus Ruber found in…
Important for…
- Mesencephalon
- Regulation of movement
Functions of reticular formation
- Regulation of CVS
- Regulation of circadian rhythm
- Alertness and emotional state
6 layers of cerebral cortex
- Molecular layer (superficial)
- External granular layer
- External pyramidal layer
- Internal granular layer
- Internal granular layer
- Fusiform layer (deep)
PET Scanning and Functional MRI used to look at…
Regional blood flow in the brain to active areas when performing specific tasks
Basal Ganglia consists of…
- Caudate Nucleus
- Putamen
- Globus Pallidus
- Substantia Nigra
- Sub-thalamic Nucleus
Striatum consists of…
Putamen and Caudate nucleus
Lentiform nucleus consists of…
Putamen and Globus Pallidus
Limbic system consists of…
- Hippocampus
- Amygdala
- Hypothalmus
- Thalamus
- Reticular formation
3 types of cerebral fibre tracts and function
- Association fibres - link areas within same hemisphere (arcuate fibres)
- Commissural fibres - link areas within different hemispheres (corpus callosum)
- Projection fibres - link areas of cortex to non-cortical areas (internal capsule)
- Women have more commissural fibres
3 layers of cerebellum
- Molecular layer (superficial)
- Purkinje cell layer (only layer that has output)
- Granular cell layer (deep)
3 components of diencephalon?
- Thalamus
- Hypothalamus
- Pineal gland
Association cortex
- Involves most of cortical area
- Input and links from many different areas to allow recognition of things
2 substances secreted by pineal gland and function
- Melatonin - regulates circadian rhythm
- Serotonin - synaptic neurotransmitter
What sense does not pass through thalamus unlike all others
Smell (passes into piriform complex)
Hypothalamus roles
Eating
Sexual behaviour
Stress
Thalamus role
Processing and relay centre that passes info onto other areas of brain
Lateral geniculate nucleus
Important in visual processing
Stages of development
- 10 weeks
- 3 months
- 5 months
- 7 months
- 9 months
- 10 weeks - cerebral expansion and commissures (connections between left and right hemispheres)
- 3 months - basic structures established
- 5 months - CNS myelination begins
- 7 months - lobed cerebrum
- 9 months - gyri and sulk appear
Critical periods of development - Rubella infection
- 6 weeks
- 9 weeks
- 5-10 weeks
- 2nd trimester
- 6 weeks - eye malformations
- 9 weeks - deafness
- 5-10 weeks - cardiac malformations
- 2nd trimester - CNS disorders
Critical periods of development - Fetal Alcohol Syndrome
- What abnormalities arise in child
- Microcephaly
- Loss of fibres
- Disturbed cellular migration
- Increased irritability
- Motor and intellectual impairment
How does speed of conduction change with increased development
- Conduction speed of peripheral nerves increase as the baby becomes more developed
Development of senses:
- Taste and Smell
- Hearing
- Vision
Taste and Smell - Well developed at birth Hearing - Excellent discriminators of language sounds Vision - Poor at birth - Colour vision at 2 months - Optic nerves not matured
How many neurones are in the brain?
Are there more or less non-neuronal cells?
- 10^10 - 10^12
- 10x more non-neuronal cells
Golgi type 1 neurones have…
Golgi type 2 neurones have…
- Long axons
- Short axons
3 types of glial cells
- Macroglia
- Microglia
- Ependyma
Ependyma types?
- Ependymocytes lining ventricles and central canal
- Tanycytes found in hypothalamus
- Choroid ependymal cells in choroid plexus
Microglia function
- Derived from monocytes
- Phagocytic cells that remove dead/damaged neurones
Astrocyte cell types
- Fibrous astrocyte - white matter
- Protoplasmic astrocyte - grey matter
- Retinal Müller cells - retina
3 functions of Astrocytes
- Spatial buffering (absorb K+)
- Neurotransmitter uptake (all of Glutamate, most of GABA)
- Glucose metabolism (convert glucose to glycogen for use by neurones - involves lactic acid)
Major period (dense) line made by... Intraperiod (feint) line made by...
- Major = internal proteins cross linking
- Intra = external proteins cross linking
Periodicity is…
The distance between 2 major (dense) period lines or 2 intra (feint) period lines
2 Major CNS myelin proteins
Myelin Basic Protein
- Induces experimental allergic encaphalomyelitis when injected into organisms
Proteolipid Protein
- Jimpy mice has no PLP and has jerky movements, very little myelin (what is present is toxic) nd severe loss of oligo’s
Other CNS myelin proteins
- Carbonic Anhydrase
- Proteases
- Myelin-Only Glycoprotein (MOG)
- Myelin-Associated Glycoprotein (MAG)
Major PNS myelin protein
P0
- Adhesion molecule that promotes schwann cell adhesion to axon membrane
Other PNS myelin proteins
- MBP
- PMP-22
Myelin composition
- CNS myelin has more…
- PNS myelin has more…
- In KO mice with no cerebrosides what happens?
- CNS = more sphingomyelin
- PNS = more cerebrosides and sulfatides
- KO mice still form myelin but it has vacuoles
Electrical properties of neurones
- Action potentials
- Graded potentials
- Action potentials - fixed size, all-or-nothing signals, can pass either way along axon but tend to go one way
- Graded potentials - variable size, local signals not propagated over long distances
Action potentials are coded by…
Graded potentials are coded by…
- AP = coded by frequency
- GP = coded by size
3 factors that set up resting potential?
- Selectively permeable membrane - ion channels are selective for specific ions e.g. Na+, K+
- Unequal distribution of ions - Na+/K+ ATPase pumps 2K+ in for every 3Na+ out (requires ATP)
- Maintained by physical forces - diffusion and electrical
Equilibrium potential
- Eion is the membrane potential that would be achieved in a neurone if the membrane was only permeable to one ion
- Eion is the membrane potential when the diffusion forces balance electrostatic forces
- This is -65mV in resting potential
Nernst Equation
Used to calculate Eion for an ion but assumes the membrane is only permeable to one ion
- Constant is divided by 2 when calculating Eion for Ca2+
Goldman Equation
- Takes in to account there’s more than one ion permeable to one membrane
- Used to estimate true resting membrane potential
Action potentials properties
- Rapid and reversible change in membrane potential from negative (-60mV) to positive (+40mV)
- AP triggered by increase in Na+ permeability
- All the same size and duration and do not decrease down the axon
Action potential Timeline
- Rising phase - rapid depolarisation of membrane by Na+ influx
- Overshoot - membrane potential is above zero (+40mV)
- Falling phase - rapid repolarisation as Na+ channels shut and K+ channels open
- Undershoot - membrane potential below resting potential due to K+ channels open too long
Absolute refractory period
A period when no stimulus, however large, is able to initiate another action potential
Relative refractory period
A stronger than normal stimulus is needed to elicit neuronal excitation
Voltage gated Na+ channels
- Open in response to depolarisation (once threshold value is reached)
- Channel inactivation occurs quickly
- Channel deactivation must occur before channels can open again - repolarisation is needed to remove inactivation ball so they can be opened again (absolute refractory period)
Voltage gated K+ channels
- Opening leads to repolarisation
- They are slow to open and slow to close (hyper polarisation)
- Relative refractory period is when K+ channels are open
Action potential conduction
- Occurs by spread of Na+ ions by diffusing along the axon
- Causes opening of channels further down axon to generate AP
- Occurs in both directions, but Na+ channels behind AP are inactivated so AP only travels in one direction
Factors affecting Conduction Velocity
- Leakiness of membrane - if more leaky then diffusion of Na+ will be slow and conduction velocity is slow
- Axon diameter - resistance to current flow is inversely proportional to the cross sectional are of the axon (thicker axons have lower resistance and faster conduction)
- Myelination - prevents current loss along the axon by increasing membrane resistance
Why so many unmyelinated small axons?
Myelination requires metabolic processes and benefit of a high membrane resistance is reduced by the high internal resistance
Axons vs. Dendrites
Axons
- Generate AP at the axon hillock
Dendrites
- Use graded potentials as aren’t many Na+ channels
Graded potentials
- Excitatory post synaptic potential (EPSP) - influx of Na+
- Inhibitory post synaptic potential (IPSP) - influx of Cl-
Spatial Summation
Temporal Summation
- Spatial - adding together of EPSPs generated simultaneously at many different synapses
- Temporal - adding together of EPSPs generated at the same synapse occurring in rapid succession
EPSP shunting
Inhibitory inputs prevent action potential firing
- Make the membrane more leaky so EPSP is dissipated
- Inward movement of Cl- so IPSP reduces size of EPSP so threshold potential harder to reach
Electrical synapses
- Allow direct transfer of ionic current from one cell o the next
- Occurs through specialised gap junction
- Unlike chemical synapses, transmission is bidirectional
