Week 1 HNN lectures Flashcards
What does the altar plate turn into?
A place of sensory functions
What does the basal plate turn into?
An area of motor function
Where are the cell bodies of motor neurons found?
The ventral horn of the grey matter
What is found in the ventral horn?
The cell bodies of motor neurons
Where are the temperature pathways found?
The ventral funiculus
What is found in the ventral funiculus?
Temperature pathways
What type of matter is the ventral funiculus made up of?
White matter
What is the outermost of the meninges?
The Dura mater
Where are epidural spaces found?
Between the dura and the vertebrae
What is the middle meningeal layer?
The arachnoid mater
What is CSF?
A filtrate of the blood
Where is CSF made?
In the choroid plexus within the ventricular system of the brain
What is the function of CSF?
To give the brain and spinal cord mechanical and immunological protection
What is the innermost meningeal layer?
The pia mater
What is a major route for spread of cancer from deep pelvic regions?
Batson veins
What is the blood supply for the lower 1/3 of the spinal cord?
The artery of Adamkiewicz
What does the artery of Adamkiewicz supply?
The lower 1/3 of the spinal cord
Where does the artery of Adamkiewicz arise from?
The left posterior intercostal artery (in 70% of people)
Where are epidural injections usually inserted?
Into the epidural space at either L3/L4 or L4/L5 vertebral level
What type of fibres transmit pain?
Ad and C fibres
Where does pain input enter the spinal cord?
The superficial dorsal horn
Where does touch input enter the spinal cord?
The deep dorsal horn
What type of fibres transmit touch
Ab fibres
What is the function of the neuron?
It is a communicating unit of the nervous system
How do neurons communicate?
Via action potentials and synaptic transmitters
Why does a resting membrane potential arise?
Due to a difference in charge (due to ions) between the inside and outside of the neuron
What is the typical RMP (resting membrane potential) of ions?
-60 to -70 mV
How do ions cross the membrane?
Via ion channels
How are voltage gated channels controlled?
Depending on membrane potential
How are ligand gated channels controlled?
In response to binding or activation by a neurotransmitter or drug
What is an action potential?
A brief but dramatic change in membrane potential
What are action potentials used for ?
Neurons use action potentials to communicate information
What happens if the depolarisation is too small and doesn’t reach the threshold?
The membrane potential returns to normal and no action potential is fired
What happens when the depolarisation is big enough and the threshold is reached?
An action potential is released
What ion is related to depolarisation?
sodium ions
What ion is related to repolarisation and hyperpolarisation?
Potassium ions
What happens for depolarisation to occur?
Fast opening of voltage gated Na channels
What happens for repolarisation or hyperpolarisation to occur?
Slow opening of voltage gated K channels
How do local anaesthetics (e.g. lidocaine) work?
It is a Nav blocker that means when nerve damage occurs the nerves in the skin can’t release action potentials
What are the two ways positive charge can travel?
- along an axon
2. out of the axon via the membrane
What does the destination of the current depend on?
- axon diameter
2. number of open pores/ channels in the membrane
Are small diameter axons high or low resistance?
High
Are large diameter axons high or low resistance?
Low
What does it mean If there are lots of open pores or channels on an axon?
The charge can leak out of the axon
What does it mean when there aren’t many open channels on an axon?
Charge wont leak out as readily
What is myelin?
A fatty white substance that prevents the leaking of charge
what makes myelin?
Schwann cells and oligodendrocytes
Where is myelin found?
Some axons are insulated by myelin
How do action potentials move along myelinated axons?
It jumps from node to node on the myelinated axon
What is the difference between myelinated and unmyelinated fibres?
Myelinated fibres conduct action potentials much faster than unmyelinated fibres
What causes MS?
Antibodies attack the myelin
What is an EPSP?
An excitatory postsynaptic potential
What does an EPSP do?
Brings the post synaptic membrane closer to threshold which makes it more likely that the cell will produce an action potential
What is an IPSP?
An inhibitory postsynaptic potential
What does an IPSP do?
Moves the post synaptic membrane potential further away from threshold which reduces the likelihood of an action potential being produced
What is temporal summation?
The frequency of firing of action potentials
What is spatial summation?
Firing at multiple sites of action potentials
What are the types of neurotransmitter?
Cholinergic, Biogenic amines, Amino acids, Neuropeptides and miscellaneous
What is divergence?
When one neuron communicates with many
What is it called when one neuron communicates with many others?
Divergence
What is convergence?
when many neurons communicate with one
What is it called when many neurons communicate with one?
Convergence
What is an EEG?
Electro-encephalography
What is PET?
Positron emission tomography
What is fMRI?
Functional magnetic resonance imaging
what is TMS?
Transcranial magnetic stimulation
What does an EEG do?
It records the electrical activity of the brain
What does PET do?
Measures blood flow, via a small dose of radioactive material injected into the bloodstream
What does fMRI do?
Measures blood flow
What does TMS do?
Uses electromagnet to stimulate brain activity, causing depolarisation or interrupted firing
What is EEG used for?
To investigate cognitive processes in response to a stimulus
What is PET used for?
Locates brain activity while performing a task
What is fMRI used for?
Locates brain activity while performing a task
What is TMS used for?
Interrupts brain activity while performing a task
By what stage of gestation will the majority of neurons be present?
10-11 weeks
What is a heterotopia?
An area of neural tissue that isn’t in the right place
Where are movements planned?
The cerebellum
What area of the brain allows us to react quickly to the environment?
The cerebellum
What does the cerebellum allow us to do?
Plan movements and react quickly to the environment
What area of the brain does everything pass through?
The midbrain
What is a sulcus
A groove
What is a gyrus
A fold
What is in the sagittal sulcus?
The sagittal sinus and a thin sheet of dura mater
What function is in the precentral gyrus?
Motor
What function is in the postcentral gyrus?
Sensory
How do the motor and sensory homunculs lie in respect to each other?
Parallel
What is in Brocca’s area?
Motor aspects of speech and speech associated gestures
Which hemisphere is Brocca’s area most commonly found?
The left hemisphere
Why is the Brocca’s area most commonly found in the left hemisphere?
Because most people are right handed
What happens if there is damage to Brocca’s area?
Extensive aphasia - non-fluent, slow speech
What happens in Wernicke’s area?
Sensory language area, lexical processing
Where is Wernicke’s area?
In the dominant cerebral hemisphere (left in 90% of the population)
What happens if there is damage to Wernicke’s area?
Receptive aphasia - extremely poor comprehension (you can’t understand speech)
What do the basal ganglia do?
Influence motor activity and motor control
What is the function of the lateral ventricles?
They provide cushioning
Where do the lateral ventricles drain into?
The third ventricle and eventually onwards to the spine
What information does the Medial Lemniscal pathway transmit?
Touch
What information does the spinothalamic pathway transmit?
Pain
What is it thought that claustrum neurones have something to do with?
Consciousness
What is the widest type of nerve fibre?
Aa
What is the fastest type of nerve fibre?
Aa
What is the second widest type of nerve fibre?
Ab
What is the second fastest type of nerves fibre?
Ab
What is the thinnest type of nerve fibre?
C
What is the slowest type of nerve fibre?
C
What is the order (widest to thinnest) of the nerve fibres?
Aa, Ab, Ad, C
What is the order (fastest to slowest) of the nerve fibres?
Aa, Ab, Ad, C
What do Aa fibres transmit?
Proprioception
What do Ab fibres transmit?
Touch in skin
What do Ad receptors transmit?
Pain, temperature
What do C fibres transmit?
Temperature, pain, itch
Why are C fibres slower than the other fibres?
They are not myelinated
What are the ascending tracts of white matter?
Sensory
What do the descending tracts of white matter do?
Modulate activity
Where in the sensory pathway does the primary neuron synapse to the secondary neuron?
In the spinal cord or brainstem
Where in the sensory pathway does the secondary neuron synapse to the tertiary neuron?
In the thalamus
Where does the tertiary neuron travel to?
The cerebral cortex
What type of mechanoreceptors detect light touch?
Meissner’s corpuscle and Merkel disks
What types of mechanoreceptors detect pressure?
Pacinian corpuscles and Ruffini endings
Where is the medial Lemniscal pathway?
Dorsal column
What does the medial Lemniscal pathway transmit?
Discriminative tactile sensation (touch)
What does the spinothalamic pathway transmit?
Pain, temperature, crude touch
Where does the primary neuron synapse to the secondary neuron in the pain pathway?
The dorsal root in the spinal cord
Where does the secondary neuron synapse to the tertiary neuron in the pain pathway?
In the thalamus
What does the corticobulbar pathway transmit?
Motor control (voluntary) and innervation of the cranial nerve nuclei
Where are action potentials for the corticobulbar pathways generated?
The motor cortex
Where does the upper motor neuron go?
The pons or medulla
Where does the lower motor neuron go?
The muscle that is being triggered
Where do the neurons from the corticospinal pathway cross over?
The pyramidal decussation
What descending tracts control voluntary motor movement?
Corticospinal and corticobulbar tracts
What descending tracts control muscle tone?
Reticulospinal, tectospinal and vestibulospinal
What does the reticulospinal pathway control?
Extensors and flexors
What are the two sections of the reticulospinal pathway?
Pontine tracts and medullary tracts
What does the pontine tracts control?
Extensors
What does the medullary tracts control?
Flexors
What does the vestibulospinal pathway control?
Modulates the activity of alpha-motor neurons and is important in the maintenance of balance and posture
What does damage/pathology of the vestibulospinal pathway lead to?
Loss of postural control
Where does the tectospinal pathway run?
Ventromedially
Where does the tectospinal pathway originate?
Contralateral superior colliculus (mid-brain)
What is the function of the tectospinal pathway?
Innervates muscles of the neck and modulates activity of alpha and gamma neurons
What is the purpose of pain?
Survival - protective
What negative effects can pain have on the body?
- CNS - anxiety, depression, sleep impairment
- CVS - inhibits cough, hyperventilation
- GI - nausea, vomiting
- GUS - urinary retention, uterine inhibition
- muscle - restless, immobility
What is nociception?
The mechanism by which we detect the presence of a potentially tissue harming stimulus
What are the four physiologic processes involved in nociception?
Transduction, transmission, modulation and perception
Where are nociceptors found?
Skin, bone, muscle, internal organs, blood vessels
Where are nociceptors not found?
The brain
What type of fibres detect temperature?
C and Ad
What type of fibres transmit pain?
C and Ad
What type of fibres transmit touch?
Ab
What are the two levels of pain modulation?
Spinal and supra-spinal
what is neuropathic pain?
Pain that is initiated or caused by a primary lesion or dysfunction in the peripheral or central nervous system
What can cause neuropathic pain?
Post-surgical and post-traumatic nerve injury
Where is pain felt in peripheral neuropathic pain?
In the territory of the affected nerve or nerve root
Where is pain felt in central neuropathic pain?
It is related to the site of the lesion in the spinal cord or brain
What are the characteristics of somatic pain?
- Site - well localised
- Radiation - dermatomal
- Character - sharp, aching, gnawing
- Periodicity - constant +/- incident
- Associations – rarely
What are the characteristics of visceral pain?
- vague distributiom
- diffuse, to body surface
- dull, cramp, dragging
- often periodic
- nausea, sweaty, HR & BP
What are the 6Ps of pain relief?
Prevention Pathology Physical therapy Pharmacotherapy Procedural Psychology
What are the steps on the WHO ladder for analgesic pain relief?
Step 1 - Paracetamol, NSAIDs or cox II inhibitors
Step 2 - Codeine, Dihydrocodein (often as co-analgesics)
Step 3 - Morphine, oxycodone, tramadol, buprenorphine, fentanyl
