Psychobiology Flashcards
Levels of organisation
Organelle, Cell, Tissue, Organ, Organ System, Organism
Parts of the cell
- Cell membrane - surrounds cell, proteins
- Cytoplasm - includes watery cytosol (water, ions, small molecules, amino acids, soluble protiens)
- Cytoskeleton - consists of filaments and tubules that crisscross the cytoplasm and help to maintain the cell’s shape
- Nucleus - contains DNA and acts as control centre
- Ribosomes - at the site of protein synthesis
Endoplasmic Reticulum - helps make proteins and lipids and transports proteins in the cell
Golgi Apparatus - modifies, sorts and packages proteins for secretion out of the cell, or for use within the cell
Lysosomes - organelles that use enzymes to break down molecules so their components can be recycled
Mitochondria - produce ATP from energy in glucose
Protein synthesis
In nucleus: transcription (DNA -> RNA) and splicing (alternative splicing = sticking together different exons to produce different proteins)
- exported to cytoplasm
In cytoplasm: translation and folding
ATP synthesis
- Glycolysis - produces glucose, 2 ATP and phosphate
- Citric acid cycle - produces 2 ATP and CO2
- Electron Transport Chain and Oxidative Phosphorylation - produces 32 ATP and H2O
- ADP + Pi -> ATP
Tinbergen’s 4 questions
(why we and other animals do stuff) - How behaviour increases fitness, modified by evolution, causes of behaviour, how behaviour developed over lifetime
Development of concepts of mind and brain
Aristotle - mind controls behaviour, heart is the seat of the mind in the body (brain = cooling system)
Hippocrates - brain is the seat of the mind, connected to sense organs and muscles
Galen - Experiments to link different nerves to function; link brain injury to loss of consciousness
Ibn Sina - first descriptions of neurological and psychiatric conditions, linking bodily changes with emotions
Descartes - brain and body as a machine (unconscious processing); soul directs the brain via pineal gland (conscious processing)
Are mind and brain separate?
Dualism - mind and body are different
Materialism - brain controls behaviour - mind is an epiphenomenon (not tangible)
- evidence that brain underlies behaviour - evolutionarily preserved different behaviour - different brains produce the same responses
Peroxisomes
These are membranous sacs of oxidase enzymes. They detoxify harmful substances and break downfree radicals.
Centrosome
The centrosome is composed of two centrioles surrounded by an amorphous mass of protein. Centrosomes are associated with the nuclear membrane during prophase of the cell cycle. Inmitosisthe nuclear membrane breaks down and the centrosome can interact with the chromosomes to build the mitotic spindles.
Centrioles
These are self-replicating organelles made up of nine bundles of microtubules. They appear to help in organizing cell division, but aren’t essential to the process
a-Microfilaments and b-Microtubules
a-Microfilaments- Microfilaments are solid rods made of proteins called actin. These filaments are important supports of the cytoskeleton.
b-Microtubules-These straight, hollow cylinders are found throughout the cytoplasm of all human cells and carry out a variety of functions, ranging from transport to structural support.
The seven characteristics of life
1.Cells -All living organisms have cells; cells are the building blocks of life.
2.Metabolism -All living organisms eat, drink, breathe and excrete.
3.Growth -All living organisms take in material from the environment to enlarge and sustain.
4.Reproduction - All living organisms are able to produce a copy of themselves.
5.Irritability -All living organisms are able to react to a change in their environment.
6.Adaptation- All living organisms are able to compete with each other for food and space to survive.
7.Movement - All living organisms are able to move.
Macromolecule
A macromolecule is a large molecule (carbohydrates, lipids, proteins, nucleic acids).
Types of physiology
Cell physiology - This is the cornerstone of human physiology; it is the study of the functions of cells.
Special physiology - This is the study of the functions of specific organs. For example, renal physiology is the study of kidney function.
Systemic physiology - It includes all aspects of the function of the body systems, such as cardiovascular physiology, respiratory physiology, reproductive physiology etc..
Pathophysiology - It is the study of the effects of diseases on organ or system functions (pathos is the Greek word for disease).
PET Imaging
- Positron emission tomography
- Inject radioactive tracer and detect radiation
- Binding of tracer molecules - quantify number of endogenous proteins and their activity
MRI
- Magnetic resonance imaging
- Structural
- Functional
- Can measure diffusion properties of the tissues
Experiments using animals because …
- Mammalian brain structures similar to humans
- Experiments - ethology (natural environment), behaviourism, physiology, neuroanatomy, neurophysiology
- Anatomy (structure, cells there and how connected)
- Physiology - recording brain activity
Peripheral NS
- Made up of the autonomic NS and Somatic NS
- via motor and sensory neurons sned signals to and from the CNS
Somatic NS
- external environment
- Motor ways and sensory pathways in spinal cord
- Dermatomes – strip of skin innervated by one nerve from one dorsal root ganglion
- Myotomes – group of muscles innervated by same motor nerve
Automatic NS
- internal environment
- Sympathetic NS (fight or flight), Parasympathetic NS (rest and restore), Enteric NS (gut)
Where things are in the body
Anterior (front) vs posterior (back)
Superior (up) vs inferior (down)
Dorsal (back) vs Ventral (stomach)
Rostral (towards beak) – caudal (towards tail) –
lateral (sides of brain) and medial (middle)
Hind Brain
Brainstem and Cerebellum called the hind brain)
- Overall: Inputs from senses – outputs to muscles or organs. - In each region: Inputs from upstream and downstream regions. - What a brain region does depends on the nature of the inputs, and outputs and how the information is integrated in that brain area.
Brain stem
- information from body to spinal cord but information from head to brain stem
- medulla at bottom, then pons and midbrain at the top
- information crosses hemispheres at the brain stem - decussation
- (Superior colliculus - quick reactions)
- Sensory and motor nuclei (deal with ingoing and outgoing information) and neuromodulatory nuclei (neuromodulation - spread over wide area of brain - widely change state of brain - arousal and motivation)
Cerebellum
- means little brain
- layered organised structure - – 5 main types of neurons
- different connections can cause behaviour
- Cerebellum-cerebral cortex loop involved in refining sequences of movements
- Neural circuitry helps to underlie this function – lots of information from different modalities carried in parallel fibres from granule cells and associated together at Purkinje cells.
Forebrain
Diencephalon (thalamus and the hypothalamus)
Cerebrum
Basal ganglia
Amygdala
Hippocampus
Cerebral Cortex
Diencephalon
Thalamus
- ‘Information hub’ - relays ascending and descending information from widespread brain areas
- Links to cortical areas - thalamic relay - Relay and gatekeeping – filter and modify information.
Hypothalamus
- Underneath thalamus
- Regulates several homeostatic processes
- Links brain to endocrine system (hormones)
- Many different kinds of nuclei with different functions e.g. appetite regulation, memory
Cerebrum
- Cerebral cortex
- Sub-cortical structures - hippocampus, basal ganglia, amygdala
Basal ganglia
- Information loops from cortex (and hippocampus), through basal ganglia, thalamus and back to cortex
- Modulated by dopamine from VTA/substantia nigra
- Computations: Co-ordinating movement (via dorsal striatum), and motivated behaviour (via ventral striatum)
Amygdala
- Key connections with cortex, hippocampus, thalamus, hypothalamus, basal ganglia and brainstem
- Computations: emotional learning, especially fear conditioning – associate environment with emotive state – respond appropriately
Hippocampus
- 3 main subfields of the hippocampus – dentate gyrus, CA3 and CA1
- Connection with neocortex - continuous - most inputs and outputs with the cortex - entorhinal cortex and subiculum
- Hippocampus is allocortex and has 3 distinct cell layers
- Cellular organisation makes it ideal for forming associative memories - learning relations between features and damage impairs memory
Cerebral Cortex
- Made up of 4 main lobes and 2 hemispheres.
- Neocortex – has 6 layers.
- It’s very folded –allows a large surface area to fit in a small space.
- Different regions have different roles:
- Layers 1-3 integrate information from local and distance cortical areas, receiving inputs and sending outputs to other cortical areas.
Layer 4 receives sensory information.
Layers 5&6 send information to subcortical structures, thalamus and spinal cord.
- Layers 1-3 integrate information from local and distance cortical areas, receiving inputs and sending outputs to other cortical areas.
Cerebrospinal fluid
- Circulates around the brain and along large blood vessels as well as through the ventricles (fluid-filled spaces in the brain)
(fills the small extracellular space around neurons) - CSF is produced from ependymal cells that line the ventricles
- Meninges are membranes surrounding the brain – dura (tough outer membrane), arachnoid and pia (next to brain surface)
- CSF cushions the brain from impacts to the head, but also clears the brain of unwanted products such as broken down proteins
- Sets environment for brain cells (concentrations of molecules such as glucose and ions)
Blood supply
- Brain has a specialised blood supply as needs lots (stroke from blocked blood supply
- Highly vascularised
- 4 main arteries - circle of Willis so others can compensate
- brain can finely regulate its blood supply
- means increase in regional brain activity increases blood supply to that region.
- this increase in the blood supply is the basis of the signal detected using functional MRI.
Brain cell types
- Neurons
- Gila
- Astrocytes - wrap processes around synapses and neurons, also contact blood vessels. Lots of supportive roles
- Oligodendrocytes – wrap myelin sheath around axon to insulate the axon and allow impulses to travel faster
- Microglia – the brain’s resident immune cell – surveys brain for infection or damage and gobbles up damaged tissue or infection.
Neuron parts
Dendrites – collect inputs from other neurons
Soma – cell body – contains nucleus (genetic material – DNA)
Axon – axon hillock, - where nerve impulse/action potential triggered (integrates all inputs)
myelin sheath - increases speed of transmission
and axon terminal – where neurotransmitter is released to signal to the next cell
- Different shapes with different functions
Ohm’s law
Current = potential x conductance
Current = potential/resistance
Electrical signalling
- Lucia and Luigi Galvani 1781 - electricity makes frogs’ leg muscles move
- The Newgate Calendar describes what happened when the galvanic process (stimulating with electricity) was used on the body
- Hermann von Helmholtz - measured speed of nerve conductions by stimulating frog sciatic nerve and measuring time to constrict muscle
Cell membrane electrochemical gradient
- Outside the cell: lots of sodium (Na+; positively charged), lots of chloride (negatively charged; Cl-), some calcium (Ca2+)
- Inside the cell: lots of proteins (negatively charged), lots of potassium (K+)
- Potassium leak channels let potassium ions through (potassium positively charged)
- Sodium potassium pump - 3 sodium out and 2 potassium in
- resting potential of -70MV
- Equilibrium potential (E) dictated by concentration difference and ion charge
Action potential
- Threshold potential reached
- Depolarisation due to opening of sodium channels
- Repolarisation due to inactivation of sodium channels and opening of voltage-gated potassium channels
- Hyperpolarisation as voltage-gated potassium channels are still open.
- Sodium channels released from inactivation (can fire AP again)
(all or nothing)
Refractory periods
In absolute refractory period can’t fire another action potential, in the relative refractory period a very strong stimulus can re-open the sodium channels and generate an action potential - Therefore strong stimuli can generate high frequency action potentials by intruding into the relative refractory period
Action potential propagation
- Action potentials propagate (transmit) along axons (They are the same size all along)
- Affected by resistance of membrane (slower if more charge can leak out), capacitance of cell (how easy to change membrane voltage)
- How far along axon - Affected by membrane resistance - more leaky membrane -> depolarisation spreads less far
Affected by diameter (internal resistance to flow down the axon) – big diameters conduct faster
Saltatory conduction and the myelin sheath
- Myelin insulates membrane - less charge lost (less leak), action potentials travelling from one node of Ranvier to the next = saltatory conduction, faster and more efficient (fewer ions flow, so less ATP needed to pump them back)
- Unmyelinated axons – lots of channels – depolarisation dissipates before travelling far down axon. Need to have lots of sodium channels close together for action potential conduction – so that next bit of membrane can be depolarised.
Synaptic transmission
- Action potential travels down axon and arrives at the end of the axon - the axon terminal
- The depolarization of the axon terminal opens voltage-gated calcium channel. Activated when membrane potential reaches -10 mV (more depol than sodium channels). Calcium enters cell
- Calcium causes vesicles - little bags of membrane containing a neurotransmitter – to fuse with the axon terminal membrane and release their contents.
- Neurotransmitter diffuses through the synaptic cleft
- Neurotransmitter binds to ligand-gated Ion channel (a channel that opens when a molecule binds to it)
- Ions flow through the channel, depolarizing or hyperpolarizing the post-synaptic membrane.
Excitatory vs inhibitory
- If the ion channels allow sodium in, the membrane potential becomes more depolarized – the post synaptic cell is nearer to the threshold for opening voltage gated sodium channels – the cell is more likely to fire an action potential. This is an excitatory synapse.
- If the ion channel lets chloride in, the membrane potential will be held near the chloride resting membrane potential - below threshold for firing action potentials. This makes the cell less likely to fire an action potential - the synapse is inhibitory
Glutamate and AMPA receptor
- Depolarisation of dendrites by ion flow through glutamate receptors generates an excitatory post-synaptic potential (EPSP) – drives membrane potential towards the threshold for action potential firing.
- Glutamate is the major excitatory neurotransmitter in the brain, opens cation (positive ion) channels (AMPA is fast opening and causes EPSP)
Other neurotransmitter examples
- NMDA lets in calcium too - cause changes in synapse to make it work better or worse - important for associative learning
- Metabotropic glutamate receptors – bind glutamate and trigger lots of intracellular signalling pathways
Excitatory vs temporal vs spatial summation
- single EPSP is sub-threshold
- temporal - many EPSPs from 1 synapse add over time to reach threshold
- spatial - 1 EPSP at the same time from many synapses add to reach threshold
GABA
- GABA is the main inhibitory neurotransmitter in the brain.
- It opens chloride channels (GABA receptors), allowing negative charge into the), generating an inhibitory post-synaptic potential (IPSP), and/or making it harder to depolarise the membrane.
Synaptic integration
Synaptic integration = summation of excitatory and inhibitory inputs
- Neuronal computation – sum up inputs and produce an output
- Input weight affected by:
- Distance from axon hillock
Shape of neuron
Location relative to inhibitory inputs (gating).
- Distance from axon hillock
Lateral inhibition
- With lateral inhibition, there is a bigger change in perceived light at boundaries - high firing neurons inhibit their neighbours. At the boundary, the high firing rate light-activated neuron receives less inhibition than the high firing rate neurons far from the boundary, and the low firing rate neurons are more inhibited near the boundary than those further from the boundary.
- Explains Mach bands illusion
Neuronal networks
- During feedforward excitation, an excitatory cell activates the next cell, which passes on that excitation
- During lateral inhibition. excitatory cells activate inhibitory neurons that inhibit adjacent excitatory neurons.
- Feedforward inhibition happens when an excitatory cell activates an inhibitory cell, producing inhibition on a subsequent excitatory cell.
- Feedback inhibition occurs when an excitatory cell activates an inhibitory neuron which inhibits the cell’s own excitatory inputs - i.e. it is a negative feedback loop.
(- Recurrent excitation is a positive feedback loop)
Sensation vs perception
Sensation - the capacity to detect a particular physical or chemical stimulus - (external or internal) sensory organs or afferent nerves
Perception - the conscious experience and interpretation of sensory information - CNS
Stimulus transduction
Each sensory organ deploys a specific mechanism to transform chemical or physical attributes of stimuli to neuronal activity.
Examples of animals using other senses
Electrolocation and communication in electric fish - Produce and detect small current flows around them. Use these currents to “see” objects
(electrolocation) and communicate with conspecifics (electrocommmunication)
Ultraviolet vision in bees - detecting a different spectrum of light may be advantageous for bees when looking for the right flowers to feed from
Asymmetric vision in the cockeyed squid - Large (yellow) eye looking upward: detects predators against the dim sunlight. Small eye looking downward to detect prey bioluminescent signals.
Sensory receptors
- Photoreceptors - detect light for vision
- Mechanoreceptors - detect movement - sound, texture, blood pressure, muscle stretch
- Chemoreceptors - chemical compounds - smell and taste
- Nociceptors - detect tissue damage - pain
- Each sensory organ or receptor detects a specific part/quality of the world
- transduce stimuli into neural activity
The retina
- Fovea covered by densely packed cones (acute vision during the daylight) (blue green and red cones, each sensitive to a specific wavelength band)
- periphery covered by rods, more sensitive to light but not as acute (sense very dim light)
the eye
- The iris opens and closes to allow more or less light through the pupil
- The cornea and the lens focus the light into the retina, where the image is recreated
- The optic disc allows vessels going in and out, and the optic nerve to carry visual information to the brain
Transduction
- Photoreceptors are depolarised in the dark, releasing glutamate.
- Light makes them hyperpolarise, reducing glutamate release
- Photoreceptors and bipolar cells do not fire action potentials, change their membrane potential, which affects the probability of neurotransmitter release.
- In vertebrate retinas, there are two types of bipolar cells: ON and OFF.
- In the fovea, one bipolar cell connect to only one photoreceptor, In the peripheral retina, one bipolar cell connects with several PR.
Neural routes to the brain (visual)
- Retinohypotalamic tract (regulate circadian rhythm, regulates light to retina)
- Geniculostriate pathway (dorsal = how, ventral = what)
- Tectopulvinar pathway (no colour, where of objects)
Sounds made up of:
Frequency, amplitude and complexity
Human ear:
- Outer ear captures and amplifies sound waves.
- Middle ear amplifies and transmit vibrations.
- Inner ear translates vibrations into neural activity
Middle ear
- Air filled cavity occupied by ossicles, the three smallest bones in the human body: Malleus, Incus and Stapes.
- Ossicles vibrate in response to tympanic vibration. Amplify and transmit sounds to inner ear (oval window).
Inner ear
vestibular organs tell us which way up we are, sound detected in cochlea, nerves bring information
Organ of Corti and basilar membrane
sensitive to different frequencies, vibrations from oval window displace liquid and make the basilar membrane vibrate (high frequency base and lower frequency in apex)
- Pressure transmission along the canals
- Vibrations of the stapes push and pull the flexible oval window in and out of the vestibular canal at the base of the cochlea.
- Pressure waves deflect the basilar membrane in a frequency specific manner.
- All pressure ends up moving the round window and dissipates.
Inner and outer hair cells
If we lose hair cells they are gone forever (can stress hair cells and they can die - we lose them as we age)
Vibration to neural activity translation in inner hair cells:
- Stereocilia: Hair-like extensions on the tips of hair cells. Molecular filaments (tip link) connect the tip of each cilia to neighbouring potassium channels.
- In resting state (no sound, middle panel), there is a basal K+ influx and neurotransmitter release.
- Basilar membrane vibration (right panel) induce bending of stereocilia which increase K+ influx, increasing neurotransmitter release at the cell base.
Coding of freqency and amplitude in the cochlea
- Place code: Frequency information is coded by the place along the cochlea with the greatest mechanical displacement.
- Amplitude code: louder sounds produce larger vibrations of the basilar membrane, making the inner hair cells release more neurotransmitter.
Auditory pathways:
- Hair cell neurotransmitter release activates bipolar cells that form the auditory nerve (cranial nerve VIII).
- The auditory nerve enters the medulla, making synapsis in a tonotopic manner
- Axons from the cochlear nuclei ascend to the superior olivary complex in the pons. (Inputs from each ear are processed by both olivary nuclei)
- A series of ascending projection along the midbrain ends up in the primary auditory cortex (A1). The tonotopic representation is preserved up to A1.
Hearing loss:
- Hearing declines with age.
- Or damage (permanent or transitory) to any components of the auditory pathway.
- Transitory: (will recover)
- Obstruction of the ear canal (i.e. excessive ear wax), damage to the tympanic membrane.
- Conductive hearing loss: caused by problems in the ossicles (i.e. otitis media during ear infections).
- Permanent:
- Otosclerosis: excessive growth of ossicles. Requires surgery.
- Sensorineural hearing loss (most common defect), due to defects in cochlea or auditory nerve. Damage to hair cells caused by toxicity or excessive exposure to noise.
(worse in men)
Hearing Aids:
Cochlear implant bypass degenerated inner hair cells.
- Miniature flexible electrode array surgically implanted in the cochlea through the oval window.
- A receiver/stimulator detects and process sound into radio signals, which are sent to the stimulator (implanted inside the skull during surgery).
- Miniature electrodes positioned in frequency specific regions of the cochlea emit electrical signals, activating neighbouring bipolar cells and the auditory nerve.
Function of smell
- Primary function of nose is to humidify and warm air going to the lungs
- Secondary function is olfaction:
- Air flows into the nose cavity.
- Odorants interact with the olfactory epithelium.
- Mucus in the epithelium captures odorants
In olfactory epithelium (cell types)
Three cell types:
- Supporting cells: metabolic and physical support.
- Basal cells: olfactory cell progenitors.
- Olfactory sensory neurons (OSN): detect odors and produce mucus.
Olfactory receptors
- Odorants are recognised by specific receptors in the cilia of OSNs.
- Olfactory receptors are G-coupled proteins whose activation opens Na+/Ca2+ channels.
- OSN is depolarized by Na+/Ca2+ influx, firing action potentials.
Olfactory pathways
- Axons from OSNs pass through the tiny holes in the cribriform plate (bone) to enter the brain.
- Each type of OSN projects its axon to a single glomerulus within the olfactory bulb.
- OSN axons make synapsis with mitral and tufted cells, that project to the primary olfactory cortex and other brain regions.
shape pattern theory
- each scent—as a function of odorant-shape to OR-shape fit —activate unique arrays of olfactory receptors in the olfactory epithelium from each scent.
- These various arrays produce specific firing patterns of neurons in the olfactory bulb, which then determine the scent we perceive.
Detection threshold of olfaction affected by
- Gender - women have lower thresholds - heightened in ovulation but not heightened in pregnancy
- Training - perfume and wine tasters can distinguish more
- Age - 50% of population is anodmic (sense of smell loss) by 85
Olfactory fatigue:
- Smell detection stops during continuous exposure, detector of changes
- Receptor adaptation - makes the receptor stop responding - detection ceases
- Mechanism - receptors internalisation or sodium or calcium channel inactivation in the olfactory sensory neuron
Purpose of taste
guides appetite and triggers physiological processes for absorbing nutrients and adjusting metabolism - identifying nutrients and avoiding chemical threats
- Bitter taste might signal poisonous food. While intense sour might be related to acidic substances, that might cause damage.
- Sweet and salty tastes normally induce seeking behaviour since such substances increase survival.
Taste sensors
- Taste receptors are arranged in taste buds, distributed along the tongue, palate, pharynx, epiglottis, and upper third of the oesophagus.
- Taste buds arranged in three kind of papillae, distributed in specific regions of the tongue.
- Receptors for different tastes group together in the same bud.
- Receptor activation sends neural signal through taste nerves
Retronasal olfactory sensation
- perception of odourants while chewing and swallowing food - brain processes odours differently, depending on whether they come from nose or mouth
- Flavour: taste (sweet, salty, sour, bitter, umami and fat) and olfaction (retronasal) combination.
