Lecture 2 - Functional Neuroanatomy Flashcards
Santiago Ramon y Cajal
Used Golgi method (learned when becoming professor) and artistic ability -> Nervous system investigations Golgi and Cajal = Nobel prize in Physiology/Medicine (despite different veiws on brain structure) o Golgi = Neurons are continuous (physically touch each other -> reticular theory) o Cajal = Neurons are contiguous (small gaps between them -> Neuron theory/doctrine) Cells/neurons independent from eachother (structurally, metabolically and functionally) Information must be transmitted across these gaps
Neuron structure
Input zone (Dendrites) -> Where neurons collect/ integrate information from other cells/ neurons Integration zone (Cell body) -> Where the decision to produce a neural signal is made Conduction (Axon) -> Where information is transmitted over great distance Output zone (Axon/ Synaptic terminal) -> Where the neuron transfers information to other cells Each neuron has different function based on structure
Different size and shapes of neurones
(3 examples of 200+) o Multipolar (most common in brain) -> motor neurones (muscle control), interneurones (relay and integrate information for learning and memory) o Bipolar (common in sensory system, e.g. vision) -> o 1 dendrite + 1 axon o Unipolar (alson seen in sensory systems, e.g. touch) -> o 1 branch leaves cell body, spreads in 2 directions Information integrates just below dendrites not in cell body
Function of neuron
o Depends on how neurons are connected Depends on connection (synapse) strength Depends whether connections (synapses) are excitatory or inhibitory Can change through changes in synaptic strength (e.g. memory) Depends on information received Strengthen by learning (e.g. learning piano, starts of not effecting the next neurone much to more and more as learn better)
Cells of the nervous system
o Neurons -> main information processing cells o Glia -> support and maintenance o Techniques to visualise cells Static staining- veiw the systems (see picture for example) Fibre tracing- how neurones connect to each other
Composition of an atom
nucleus -> consisting of protons (positive charge/ 1+) and neutrons (neutral/ no charge) orbited by electrons (negative charge/ 1-) No. electrons = no. protons (negative and positive charges cancel out -> molecule has no charge) Atoms are held together by electrostatic force: o Opposite charges attract one another (electrons that orbit are held in place by attracting to the positive charge of the protons AND molecules with an overall negative charge attract other molecules with a negative charge also) o Same charges repel one another
Ion
Ions= atoms/ molecules that have lost/ gained one or more electrons Ions that have lost electrons are positively charged (cations) Ions that have gained electrons are negatively charged (anions)
Ions in water
Solid substances made of ions are known as salts (always contain equal numbers of positive and negative charges- NaCl is the chemical formula of table salt: Na= sodium and is positive charged, Cl = Chloride and is negative charged -> hence the charges cancel each other’s charges -> making table salt have no charge) When salts are dissolved in water, positive and negative ions separate and move about freely Ions are still influenced by electrostatic forces
Positive ions
Cations Sodium (Na+): generating action potentials, mainly outside neuron (extracellular) Potassium (K+): maintaining resting potential, mainly inside neuron (intracellular) Calcium (Ca2+): synaptic transmission, almost exclusively outside neuron (extracellular)
Negative ions
Anions Chloride ions (Cl-): suppressing action potentials, mainly outside neuron (extracellular) Proteins (An-): maintaining resting potential, mainly inside neuron (intracellular)
Glial cells
Astrocytes Star shaped Each astrocyte can connect with up to 100,000 neurons Neurones stayed same with evolution, but astrocytes have become much more complex Regulate blood flow to active neurons -> ensures oxygen for energy needed for neurons to process and remain alive Create scar tissue stopping spread of damage to neighbouring tissue -> Forming and modulating neural connections during development -> Microglia Very small Travels to injured sites in the brain to remove debris that could damage brain -> immune system, Works less as get older -> disfunction results in Alzheimer’s Oligodendrocytes Myelination (creating the layer of fat around the axon -> speed up neural transmission) Brain and spinal cord Schwann cells Myelination (creating the layer of fat around the axon -> speed up neural transmission) Rest of the body
Demylinating disease
Multiple Sclerosis (MS) and Guillain Barre Syndrome (GBS) Immune system attacks the myelin produced by oligodendrocytes (MS) and Schwann cells (GBS) Probably an autoimmune disease Causes inflammation of the CNS nerves Affects insulating layer of axons -> slows/ dissolves action potential
Grey matter, white matter and basics of brain
Grey matter = neuron cell bodies White matter = neuron axons Brain floats in cerebrospinal fluid (CSF) for protection and nutrition
Orientation of the brain
Humans = bipodal -> body up, face foward
Dog - quadripudal -> body parallel to ground, face foward
Disections of brain
Brain to body control
Ipsilateral = same side (left controlled by left brain)
Contralateral = opposite side (left controlled by right brain)
Brainstem
Brainstem (stayed the same throughout evolution)
- Controls vital body functions (Breathing, Heartbeat, Artery dilation, Salivation, Vomiting)
- Contains the nuclei for cranial nerves III–XII (WHAT DOES THIS CONTROL)
- The pons is closely connected to the cerebellum
- Movement and balance
- Midbrain (sensory and motor centres)
- Neurotransmitters (from the brainstem)
- Dopamine (Ventral tegmental area)
- Serotonin (Raphe nuclei)
- Noradrenaline/ norepinepherine (Locus coeruleus)
Cerebellum
- Own 3-layer cortex with ten ‘lobules’ (gyri)
- Own subcortical structures (deep cerebellar nuclei)
- 10% brain volume, but 50% of the brains neurons
- Sensory information directly from brainstem and isocortex
- Coordinates movement (Balance, Motor planning, Motor learning, Eye movement control)
- Coordinate non-motor function (Rule learning, language)
Basal ganglia
- Caudate Nucleus (blue)
- Cognitive control − Putamen (green)
- Motor control − Nucleus Accumbens (red)
- Reward processing − Globus Pallidus
- Receives outputs from all three other basal ganglia structures
- Damage -> Parkinson’s Disease (break in basal ganglia, implant machinery–> reduce/ stops tremors)/ Huntingdon’s Disease
Thalamus
Complex cluster of nuclei (motor nuclei, sensory nuclei)
Connected to almost any area of cortex – (basal ganglia/ cerebellum -> thalamus (relay)-> isocortex)
Involved in regulating sleep and wakefulness
Occipital lobe
Visual processing (basic visual features, colour and motion) -> calcarine sulcus is primary visual cortex (retinotopic organisation)
Separated from parietal lobe by parieto-occipital sulcus
Parietal lobe
- Somatosensory () perception, Multisensory integration (), spatial attention and decision making
- Separated from frontal lobe by central sulcus (fissure)
- Lesions
- Visual neglect
- Only sees half of object – e.g. will only eat half a pizza
- Left damage = neglect right space -> can explain whole pizza appearance just can’t see the half
- Can be trained to see differently
- Gertsmann’s syndrome
- Dysgraphia –
- Dyscalculia –
- Finger agnosia –
- Left-right confusion –
- Bálint’s syndrome
- Optic ataxia –
- Optic apraxia –
- Simultaneous agnosia –
- Visual neglect
- Predicting lapses in attention -> O’Connell et al. 2009
- Continuous Temporal Evaluation Task (CTET)
- Checkerboard rotates 90oC clockwise/ counter-clockwise every 800 ms
- Participants respond when it takes longer than 1120 ms to change
- Parietal brain signals predict attention lapse 30s before happening (increase more and more then sudden drop)
- 5120 participants
- 150 trials
- Continuous Temporal Evaluation Task (CTET)
Temporal lobe
- Separated from frontal lobe by Sylvian fissure (lateral fissure/sulcus)
- Superior temporal gyrus (primary auditory cortex, speech and language processing (Wernicke’s area), Social cognition (Posterior STS))
- Middle temporal gyrus (Interception, Distance/time perception, Language)
- Inferior temporal gyrus (object recognition, face recognition)
- Damage
- Prosopagnosia – face blindness
Frontal lobe
- Primary motor cortex (red)
- Anterior to central sulcus -
- Action execution
- Direct connections to spinal cord
- Premotor cortex (blue)
- Anterior to primary motor cortex -
- Motor preparation
- Prefrontal frontal cortex
- Everything anterior to premotor cortex -
- Superior, Middle, Inferior Frontal Gyri -
- Working memory, goal-directed action (reward/punishment processing, linking rewards to action, tracking expectations and outcomes, conflict monitoring and social cognition/emotion) and language
- Orbitofrontal cortex
- Reward processing – linking stimuli to rewards (Classical conditioning -> Pavlov’s dog)
- Ventromedial prefrontal cortex
- Compares rewards to choose best action
Brains intrinsic properties
Grey matter of isocortex has six layers of cells
Different brain areas have different cellular profiles (cytoarchitecture)
Brodmann (1909) mapped brain areas with different cytoarchitecture
Number of cells in each section shown by bar diagram
Suggests grey matter has different functions- changes in different areas of grey matter
Brain activity at rest - MRI
Brain always active
Decrease and increase together= connected/ function together
Blue= different functional network
Use this to split brain to temporal charictoristics
Each lobe is shown to contain 4 distnct networks -> showing lobes not good to define functions (however occipital lobe is accurate to function)
Roughly 7 networks = different functions
One area is capable of multiple functions
Default mode network
30 seconds of a task (visual, auditory, motor, memory, language etc.) - 30 seconds nothing
Same pattern brain activity when doing nothing
Default mode network link to internal processing
Link to Alzheimer’s disease
Exists in most animals
Diffusion and concentration differences
Diffusion is the movement of particles (atoms, ions, molecules) in a gas or liquid (e.g., water) from regions of high concentration to regions of low concentration -> down the concentration gradient
Diffusion is caused by the random movement of particles -> randomly colliding with the membrane and diffusing through it
CNS
Brain and spinal cord
PNS
All nerves (enclosed bundle of axons)/neurons outside CNS
Monosynaptic reflex arc -> sensory signals not being processed in the brain
Stimulus -> receptor -> sensory neurone -> interneuron -> sensory neurone -> effector organ -> response
Structural
- Cranial nerves
- Olfactory sensory
- Optic sense
- Occularmotor motor
- Trochlear motor
- Trigeminal sensory and motor
- Abducent motor
- Facial motor
- Vestibulocochlear sensory (inner ear)
- Glossopharyngeal motor
- Vagus motor (heart, lungs) and sensory
- Accessory motor
- Hypogloassal (tongue)
- Spinal nerves
- (31 pairs -> each in a pair in opposite direction)
- 8 cervical pairs
- 12 thoracic pairs
- 5 lumbar pairs
- 5 secral pairs
- 1 coccygeaal pair
- (in that order from top to bottom)
- Ventral (efferent fibres = away from brain/CNS) and Dorsal (afferent fibres = towards the brain/CNS) roots
Functional
- Somantic nervous system
- Voluntary body movements
- Conducts sensory information
- Autonomic nervous system
- Little conscious awareness/ control
- Controls homeostasis (maintenance of internal environment) = sympathetic
- ‘Fight or flight’
- Dilate pupils
- Inhibit salivation
- Increase heartbeat
- Relax airways
- Inhibit stomach activity
- Stimulate glucose release (gallbladder)
- Inhibit intestine activity
- Secrete epinephrine and no epinephrine
- Relax bladder
- Promote ejaculation/ vaginal contraction
- Constant contest as to which is needed more -> when relaxed = parasympathetic
- Parasympathetic nervous system
- ‘Rest and digest’
- Constrict pupils
- Stimulate saliva
- Constrict airways
- Stimulate stomach activity
- Inhibit glucose release (gallbladder)
- Stimulate intestine activity
- Contract bladder
- Promote genitalia erection
