Healthy Nervous System Flashcards
What does Merkel’s disk sense and where is it located?
What type of receptors?
- light pressure, texture
- Near epidermal border
Slowly adapting
What do free nerve endings sense in the skin and where are they located?
warm, cold, itch, pain
(The free endings respond to thermal (hot or cold) stimuli, noxious chemical or mechanical stimuli irritants that provoke ‘itch’)
Epidermal border
What do Meissner’s Corpuscles sense and where are they located ?
What type of receptors are they?
Light touch/stroking of the skin
Upper dermis/Epidermal border
Quick adapting
Where are hair follicle receptors located and what do they sense?
Hair follicles in dermis
Movement
Where are Pacacian corpuscles located and what do they sense?
What type of receptor?
Hypodermis
Vibration
Quick acting
What do Ruffini’s endings sense and where they located?
What type of receptor?
Skin stretch
Sub dermal fat
Slow adapting
What is the sensory modality of A-Beta fibres, what is their diameter and conduction velocity?
light touch, pressure, vibration
about 10-15 microM
about 25-80 m/s
What is the sensory modality of A-delta fibres, what is their diameter and conduction velocity?
Heat, cold, noiception (nausea)
about 2-5 microM,
about 2-25 m/s
What is the sensory modality of C fibres, what is their diameter and conduction velocity?
Heat, cold, nocioception, itch (aching)
< 1 microM
< 1m/s
What are SNAPs?
sensory neuron action potentials
What is an Electroencephalogram (EEG)?
‘electrodes’ on the scalp (usually) sample the extracellular electrical potential from the surface of the cortex. This is an average of mostly asynchronous nerve activity in the cerebral cortex but some synchronous activity gives rise to identifiable wave patterns at frequencies that are characteristic of specific behaviours
What does a EEG delta activity signify and what is its wave frequency?
Delta (< 4 Hz) - deep sleep
What does a EEG Theta activity signify and what is its wave frequency?
some sleep states (e.g. non REM sleep), dozy
< 4 - 7 Hz
What does a EEG Alpha activity signify and what is its wave frequency?
quiet, awake
< 8 - 13 Hz
What does a EEG Beta activity signify and what is its wave frequency?
activated cortex (e.g. intense mental activity, REM sleep) > 13 Hz
What is DSM IV?
Diagnostic and Statistical Manual of Mental Disorders (American Association of Psychiatry)
What is ICD-10?
World Health Organization (International Classification of Diseases) classifications includes psychiatric disorders
What is neurology?
Diagnosis and treatment of neural dysfunction: the emphasis is on direct identification or deduction of physical causes and rational therapy
What is psychiatry?
Diagnosis and treatment of mental dysfunction: the emphasis is on psychological, social and behavioural causes though physical measurements are sometimes taken. Therapy is pragmatic and experiential.
What is psychology
The study of processes underlying mental function including experimental and clinical approaches to the understanding of higher order brain functions such as dictate personality
Where are the 2 enlargements along the spinal cord?
Where the major plexuses of the limbs arise
2 significant points about the ventricles
- site of choroid plexus
* cerebrospinal fluid/blood fluid/blood barrier
Where do motor neurones arise from the spinal cord?
ventral/anterior part of spinal cord
At what vertebral level should a lumbar puncture be performed?
L3/4 or L4/5
Why is the hindbrain (pons and medulla) important?
- cranial nerves pons and medulla sensory and motor for head
- hearing, balance (vestibulocochlear nuclei)
- major tracts ascending & descending
- inputs to cerebellum (pons)
- breathing
What is the cerebellum responsible for?
- posture, eye movements, spinal motor, vestibular nuclei
- body position versus motor commands cortex (via thalamus)
- motor learning motor learning
- measuring, timing
- Ataxia
What is the midbrain responsible for?
posterior/dorsal posterior/dorsal • colliculi (vision/hearing)
anterior/ventral
• oculomotor nuclei
• dopaminergic neurons
eye movement defects
Parkinson’s disease
Unconciuos reflex of turning head to flash/large sound etc
Important units about the thalamus?
- dorsal diencephalon
- sensory relay to cortex
- reciprocal cortex-thalamus connectivity connectivity
- consciousness (Francis consciousness (Francis Crick)
- coma
Sensory info relayed to cortex
Gate keepr for information entering the cortex
- reciprocal connections with the cortex
Role of the basal ganglia?
- modulate cortex via thalamus
- cognitive reward, learning and motivation and motivation
- Huntington s and Parkinson’s Disease
What is the role of the cortex?
Executive function
Memory etc
- mapped out on the highly folded surface
How many layers does the cortex have and which is the most variable in thickness?
6 layers
Lamina 4 - most variable in thickness
Where is the primary motor cortex in relation to the central girus?
Just in rostral
Where is the primary sensory cortex in relation to the central girus?
Just caudal
4 roles of the frontal lobe?
- association cortex
- character and personality (pre-frontal cortex)
- gaze control
- learned tasks
What is Broca’s aphasia and how does it present?
Damage to area 44 on left side
• telegraphic speech
• meaning spared
• comprehension normal
What is Wernicke’s aphasia and how does it present?
Damage to a speech area of the cortex
• speech pattern “normal”
• no meaning or comprehension
After an amputation, what process in the cortex can cause a lot of pain?
Reorganisation - map plasticity
What are commisures and what is dessucation?
commisures are tracts that connect two halves of CNS
commisural axons “decussate” cross the midline
level at which decussation occurs in major pathways varies
What are graded potentials?
Occur when dendrites are stimulated • small decays (1-2 mm) • all directions outer • “de”polarising • exciting (Different make up at the axon hillock - AP - voltage gates)
Is sodium pump out of resting neurones to keep the membrane potentials?
Yes
What happens when transmission occurs at a nerve terminal?
- synapse
- presynaptic presynaptic neurotransmitters
- postsynaptic receptors
- depolarisation
- hyperpolarisation
- second (molecular) messengers messengers
What is meant by plasticity & integration?
- synapses efficiency of transfer efficiency of transfer can be modulated = learning
- dendrites integrate inputs from multiple synapses
How in the brain grey matter organised?
- nuclei/ganglia
- layers
- functional segregation
Four types of neurone?
- projection
- local interneurons (+ve, -ve)
- motor axons exit CNS = efferent
- peripheral sensory neuron cell bodies outside the CNS = afferent
What are projection neurones?
V. Long in myelinated tract
Info from cortex down into spinal cord
Layer 5 of the cortex
From which embryological feature is the PNS derived and from what does that originate?
Neural crest which migrates from the neural tube
Defects in the formation of the neural crest can be related to craniofacial problems
The dorsal closures of the neural tube is important for the establishment of which axis?
dorsal-ventral
In terms of the origin of the CNS, where are the cells ‘born’?
Inner ventricular surface
From which directions do protein signals come in the origination of the CNS?
Dorsal and ventral
Which two processes give the structural diversity of the CNS?
proliferation + migration
What types of migrations are involved in brain formation?
radial and tangential neuron migration
When are the glial cells made
• last cell division makes glial cells
What determines neural cell type
cell type is determined by DV position in neural tube
Glial cells?
radial glia:
• neural progenitors/guide neural migration
Oligodendrocytes (CNS) >1 axon, Schwann cells (PNS) 1 axon
• deposit myelin
microglia:
• phagocytic CNS
astrocytes:
• physiological homeostasis, blood/brain barrier
• neural stem cells
What is the most important protein type in tight junctions?
Claudins
What is the functional organisation the choroid plexus and what does it do?
Epithelium (with tight junctions) over the blood vessels (with micro villi and cilia)
- leaky - endothelium - no tight junctions
- secretion of CSF
What are the Circumventricular Organs?
Windows of the brain - all have leaky endothelium but epithelium with tight junctions
Sensing the blood
- ports of entrance and exit
List on page 2 of BBB lecture
Which are the sensory circumventricular organs?
Area postrema Subfornical organ Organum vasculosum lamina terminalis lChoroid plexus
Which circumventricular organs are Neurohaemal Secretory?
Median eminence
Neurohypophysis
Pineal gland
Choroid plexus
See diagram on page 3 of BBB lecture for how substances can cross the BBB
NB
How is water secreted through the BBB and the choroid plexus?
Na+/K+ pumps on brain/CSF surfaces respectively
Water follows the sodium osmotically
Why do plasma and CSF not reach equilibrium for substance concentrations?
Because CSF is being continually secreted
What happens to the protein content of CSF as you descend the spinal cord?
Increases
What causes non-communicating hydrocephalus?
blockage of aqueduct of Sylvius
What causes communicating hydrocephalus?
obstruction of flow in sub-arachnoid space or villi
-eg. Bleed
What factors affect CSF penetration of drugs?
- see diagram on page 5 of BBB lecture
What do you know about the ABC Superfamily (ATP-binding cassette) Efflux Transporters in the CNS?
- P-glycoprotein-(Pgp) ABCB1 MDR1 human (Deely and Cole 1997)
- Multi-drug Resistance-Associated Protein-(MRP) ABCC1,2,4,5 MRP 1-7 human (Kusuhara and Sugiyama 2002)
- Breast Cancer Resistance Protein-(BCRP) ABCG2 hBCRP human (Doyle et al. 1998)
How many possible drug binding domains do photoaffinity probes suggest P-glycoprotein has?
How many ATPases does it require to spit out one molecule?
2
2
How does loperamide work?
Paralyses intestine via opium receptors
Do water soluable drugs tend to get into the CNS?
No
What percentage of CNS drugs are lipid soluable?
75%
What percentage of CNS drugs are subject to active efflux?
Up to 90%
Which type of drugs enter the CNS via Carrier-Mediated Influx (Metabolite Transporters)
A relatively small number of drugs that resemble the natural substrate