Neuroscience Flashcards
The basilar membrane sits above a fluid-filled compartment of the cochlear and movement of the fluid transmits to movement of the basilar membrane.
What cells attached to the basilar membrane and tectorial membrane above translate this movement into a nerve impulse?
Hair cells
Hair cells on basilar membrane are moved by sound waves passing into fluid in the cochlear.
What does this movement cause on the hair cell membrane that helps generate a nerve impulse?
Mechanically gated K+ ion channels open.
In the central auditory pathway, what are the key steps of the route nerve impulses take from the cochlear?
“E.COLI”
Eighth cranial nerve (vestibulocochlear)
Cochlear nucleus
Olivary complex
Lateral lemniscus
Inferior colliculus
What is the first structure in the central auditory pathway where the auditory nerve (vestibulocochlear CN VIII) enters the brain stem?
Cochlear nucleus
(Remember: “E.COLI”
Eighth cranial nerve
Cochlear nucleus
Olivary complex
Lateral lemniscus
Inferior colliculus)
In neurons, where do action potentials propagate from?
Axon hillock
What are the two types of neuron synapses?
Chemical (neurotransmitters)
Electrical (ions)
Electrical neuron synapses are less abundant than chemical synapses.
Where might you find electrical synapses?
Brainstem, hypothalamus, etc.
What triggers neurotransmitter release in neuron chemical synaptic transmission?
Influx of calcium ions (which is triggered by the axon potential depolarising synaptic terminal membrane).
What is a connexon?
A protein structure that forms a gap junction in a neuron electrical synapse.
What part of the neuron structure might change as part of neural plasticity?
Dendritic spines (can change number, size, or composition).
What are glia?
Non-neuron cells in the brain, e.g. oligodendrocytes.
Give two important functions of oligodendrocytes.
- Myelinating neurons (one oligodendrocyte can myelinate multiple neurons)
- Provide metabolic support for axons.
Myelin is composed of lipids and proteins.
What is the percentage composition of myelin?
70% lipid, 30% protein.
What are three key functions of microglia?
- immune surveillance
- phagocytosis
- synaptic plasticity (spine pruning)
What is the difference between M1 and M2 microglia?
M1 cause inflammation
M2 help resolve damage/repair
What happens to microglia when they are activated?
Retract their processes and become unramified/amoeboid and motile.
What are the resident immune cells of the CNS?
Microglia.
What are the most numerous glial cells in the CNS?
Astrocytes
Are all astrocytes stellate (star-shaped)?
No, astrocytes are highly heterogeneous.
How do astrocytes help form the blood-brain barrier?
In capillaries, astrocyte end feet cover the basement membrane and maintain the tight junctions in between capillary endothelial cells.
Glutamate is one of the most abundant neurotransmitters, and is a precursor for GABA.
How are astrocytes in tripartite synapses involved in the glutamate-glutamine shuttle?
Astrocyte processes envelope synapses and take up excess glutamate in the synaptic cleft then convert it into glutamine.
What is neurovascular coupling?
The process by which neuronal activity increases blood flow to active areas of the brain.
Give four important features of the blood brain barrier.
- More tight junctions between capillary endothelial cells.
- Fewer fenestrations in basement membrane.
- Astrocyte end feet cover basement membrane.
- Pericytes embedded in basement membrane.
What ciliated glial cells line the brain’s ventricles and the spinal cord’s central canal?
Ependymal cells
What area of frond-like projections in the lateral ventricles, formed from modified ependymal cells, is the main site of CSF production?
Choroid plexus
Sensation is a mental process resulting from the immediate external stimulation of a sense organ. Is this top down or bottom up processing?
Bottom up
Perception is the ability to become aware of something or understand something following sensory stimulation. Is this top down or bottom up processing?
Top down
If something is gustatory, what is this referring to?
Perception of taste.
What is the term for the psychological factors that determine how you perceive your environment, affecting how mental illness presents?
The perceptual set.
Are hallucinations caused by malfunctioning top down (perception) or bottom up processing (sensation)?
Top down.
Hemispheric lateralisation of emotions is the idea that the left and right hemispheres may be specialised for different types of emotions.
Is the right side of the brain specialised in negative or positive emotions?
Negative emotions.
Photoreceptor cells convert light into electrical signals.
What photoreceptor cells are found in the retina?
Rods and cones.
In the retina, what cells do rods and cones pass their electrical impulse to?
Bipolar cells.
In the retina, what is the function of amacrine and horizontal cells?
Act as modulators of information being passed by bipolar cells to ganglion (e.g. contrast and sensitivity details across light field)
In the retina, what is the function of muller cells?
Muller cells support the architecture of the retina and support other cells in the retina (e.g. metabolically).
What is the difference between scotopic and photopic vision?
Scotopic is monochromatic, in low-light conditions, mainly using rods.
Photopic is chromatic (colour), in bright light, mainly using cones.
Remember Colour = Cones
What light sensitive photopigment is found in rods?
Rhodopsin
What light sensitive photopigment is found in cones?
Opsin
How does opsin in cones in the retina allow us to see colour?
There are three different types of cones: red, green, blue; and they contain different types of opsin which respond to different light waves.
How does light received by rod and cone cells result in a nerve impulse?
When light strikes rhodopsin/opsin pigments, they change form, causing a cascade of chemical reactions in the cell, affecting Na+ ion channels in the cell membrane, which changes the membrane potential, generating an electrical signal.
At what age do humans have the most number of neural connections/synapses?
At birth.
What highly vascular area do neurons arise from in the foetus?
Germinal matrix.
Are presence of primitive reflexes an indicator of healthy brain functioning in adults? Why?
Primitive reflexes are coordinated by the brainstem, and often are suppressed by cortical functioning e.g. the grasp reflex.
Presence of some primitive reflexes such as the grasp reflex suggest the cortex is damaged.
Why do newborns enjoy black and white pictures more than colourful pictures, but 3 month olds enjoy colourful pictures?
Infants have more rods than cones. By 3 months old, however, cones have developed more and can see most visible colours.
Parents tell you they think their 1 year old is left handed. Why might you be concerned?
Children are ambidextrous until around 3 years old, as lateralisation of the brain develops. Preference for one hand in babies/children under 3 could suggest a stroke or other neurological concern.
Distress is stress which is damaging and harmful.
What is eustress?
Positive stress which is beneficial and motivating.
How do neuronal circuits explain the interaction between physical and psychological stress in the brain?
Physical neuronal circuits overlap and interact with psychological neuronal circuits.
Response to acute stress is coordinated by the autonomic nervous system.
What communication system is involved in chronic stress response?
HPA (hypothalamic-pituitary-adrenal) axis.
What does the theory of allostasis say about chronic stress?
Complex physiological/homeostatic systems adapt by changing set-points during stressful situations.
What does the word “fitness” mean in relation to natural selection?
Reproductive success.
Explain the stress diathesis model.
Diathesis = disposition.
The combination of predisposition (e.g. genetically) and adverse life events triggers manifestation of psychological disorder, with different levels of stress/adversity required depending on the level of predisposition.
A neuron is a specialised cell that transmits electrical and chemical signals in the nervous system.
Name three key features of a typical neuron.
Dendrites, axon, and axon terminal.
In a healthy adult neuron, what is the resting membrane potential?
-60 to -70 mV
What ion channels in the neuron phospholipid bilayer are open to maintain a negative charge inside the cell during resting membrane potential?
K+ ion channels.
The brain uses a lot of energy to maintain resting potential of neurons via what active transport pump?
Na+/K+ ATPase.
Why can a neurotransmitter e.g. glutamate binding to receptors on the postsynaptic neuron cause depolarisation or EPSP (Excitatory Post-Synaptic Potential)?
The binding of the neurotransmitter opens chemically gated ion channels, allowing positively charged Na+ into the neuron.
Why can a neurotransmitter e.g. GABA binding to receptors on the postsynaptic neuron cause hyperpolarisation or IPSP (Inhibitory Post-Synaptic Potential)?
The binding of the neurotransmitter opens chemically gated ion channels, allowing positively charged ions out OR negatively charged ions into the neuron.
What happens when EPSP (Excitatory Post-Synaptic Potential) reaches the depolarisation threshold of -55mV, causing an action potential?
Voltage-gated Na+ channels open, causing an influx of Na+ into the neurons.
When sufficient depolarisation happens, at around +30mV, what occurs to repolarise the neruon?
Voltage-gated K+ channels open, causing K+ to leave the cell.
Also Na+ channels close to prevent further influx of Na+.
During hyperpolarisation, due to K+ channels, the neuron cannot fire again until it reaches resting membrane potential.
How does the neuron reach resting membrane potential from this state?
Na+K+ ATPase pumps Na+ out and K+ into the neuron.
Why is hyperpolarisation important for action potentials to travel along the axon of a neuron?
Hyperpolarisation follows the action potential, preventing it from stagnating or travelling back up the axon, and makes the action potential continue travelling along the axon terminal.
What is saltatory conduction?
Conduction of an action potential in myelinated neurons, where the action potential can “jump” (latin: saltare) between the nodes of Ranvier.
Motor end plate action potential spreads (via voltage gated Na+ channels) down the T tubules of muscle fibres, where it triggers voltage-sensitive DHP receptors to change shape.
What effect does this have inside the myocyte?
DHP receptors are mechanically coupled with RyR (ryanodine receptors) on the sarcoplasmic reticulum.
DHP changing shape causes RyR to open, allowing Calcium ions to be released to the sarcomere.
What type of muscle fibres would be useful when running a marathon (or ultramarathon!) and why?
Type I AKA slow twitch.
Have more oxidative capacity; takes time but generates more ATP.
What type of muscle fibres would be useful when walking up a flight of stairs and why?
Type 2A AKA fast fatigue resistant.
Have a mix of oxidative and glycolytic capacity.
What type of muscle fibres would be useful in sprinting?
Type 2B AKA fast fatigable.
Have more glycolytic capacity; generates smaller amount of ATP but works very quickly so can keep up with demand.
Why do sensory neurons involved in motor reflexes in antagonistic muscle pairs (e.g. bicep and tricep) need to synapse with both a motor neuron and an interneuron?
Sensory neuron needs to cause contraction of one muscle by synapsing directly, and relaxation of the other by synapsing with inhibitory interneuron (e.g. contraction of bicep, needs relaxation of tricep to bend elbow).
What two important structures, one in the muscle and one in the tendon, give us proprioception by containing mechanical-sensitive receptors?
Muscle spindles and golgi tendon organ.
When are mechanical-sensitive receptors in the golgi tendon organ and muscle spindles activated to cause relfex contraction or inhibition?
When over extended e.g. when muscle is relaxed and lengthened/stretched (extension) muscle spindle is stretched, if muscle is contracted (flexion) golgi tendon organ is stretched.
In the three levels of motor control hierarchy, what two areas of the brain are involved in higher motor control to plan and execute movement strategy?
Association cortices (plan the movement/motivation).
Basal ganglia (gives the ‘go’ signal).
In the three levels of motor control hierarchy, what two areas of the brain are involved in middle motor control to recruit correct muscles and refine movement?
Motor cortex.
Cerebellum (fine motion control).
In the three levels of motor control hierarchy, what two areas of the CNS are involved in lower motor control to engage muscles, perform reflexes, and provide rhythmic control via central pattern generators?
Brain stem.
Spinal cord.
Briefly explain how the vestibulospinal tract helps us maintain balance and posture as an unconscious process.
Sensory nerve from labyrinth in inner ear synapses with motor nerve in the vestibular nuclei in the brainstem, which then activates muscles to correct balance.
What function do the premotor cortex (PMC) and supplementary motor area (SMA) have in higher level motor planning?
They both receive input from the prefrontal cortex and are then involved in sequencing and ordering movement, instructing the primary motor cortex.
Explain how the basal ganglia nuclei prevent unwanted movement.
Globus pallidus & substantia nigra pars reticulata are tonically active; constantly releasing GABA to inhibit the thalamus, preventing it from exciting neurons in the motor cortex.
Explain how the basal ganglia allow voluntary movement to occur after receiving glutamate from the cerebral cortex.
Caudate and putamen release GABA.
GABA inhibits globus pallidus and substantia nigra pars reticulata, disinhibiting the thalamus.
Thalamus can then release glutamate to excite the motor cortex.
Explain briefly how the cerebellum works as a parallel processor using a sensory feedback mechanism during execution of motor activity.
Adjusts ongoing motor commands using sensory information to maintain fluid precise movement.
(e.g. compares intended movement (from motor cortex) with actual movement (from sensory feedback) to provide error correction function).
What parasympathetic nerves are involved in the autonomic nervous system?
CN III, VII, IX
CN X
Sacral outflow (to pelvic organs).
“Parasympathetic hitches a ride
On cranial nerves 3, 7, and 9
Not forgetting vagus also
And the sacral outflow!”
Are postganglionic autonomic motor neurons myelinated or unmyelinated?
Unmyelinated.
Are preganglionic autonomic motor neurons myelinated or unmyelinated?
Usually myelinated.
What neurotransmitter is required between preganglionic and postganglionic autonomic motor neurons?
Acetylcholine (ACh).
What neurotransmitter is required between postganglionic autonomic motor neuron and the effector (e.g. smooth muscle)?
Either acetylcholine (usually parasympathetic) or noradrenaline (usually sympathetic).
What is adrenal amplification in the sympathetic autonomic nervous system?
Sympathetic stimulates adrenal medulla to release adrenaline and noradrenaline which amplifies the sympathetic response.
What is the enteric nervous system?
Autonomic nerve supply to the digestive tract, which can act independently of the sympathetic and parasympathetic systems.
What sympathetic receptor sub types for noradrenaline are found mainly in blood vessels for vasoconstriction?
Alpha (1 and 2).
What sympathetic receptor sub types for noradrenaline can be found in the lungs and are stimulated by salbutamol for bronchodilation?
Beta 2.
What sympathetic receptor sub types for noradrenaline can be found in the heart, and has some crossover with beta 2 receptors in the lungs, and so can be stimulated by salbutamol, causing tachycardia?
Beta 1 receptors.
