Neurobiology Flashcards
Neuroplasticity
is a term that describes change to the brain throughout an individual’s’ life course
neuroplasticity process
Neuroplastic change can occur at small scales (e.g. individual neuron changes), large whole-brain scale (e.g. in response to injury brain function may move to a new area of the brain)
Growth of axons and dendrites is as much as part of plasticity as pruning and apoptosis
;re-growth of axons can be up to 5 nm per day
What is neurulation?
When an embryo starts to differentiate further (how the nervous system develops)
Posterior (end), Ventral (front), Dorsal (back), Anterior (beginning)
All animals in phylum chordata develop dorsal nerve cord as early stage, in process of neurulation (spine)
neurlation process
Nerve cord develops from ectoderm (outer tissue layer)
Area of ectoderm on dorsal side of embryo into neural plat
Cells on neural plate change shape→ plate folds inwards, creates groove along back, separates from rest of ectoderm→ forms neural tube, which becomes nerve cord (spinal cord)
Explain how Spina Bifida occurs
Centrum in vertebrae (series of bones) provide support + thing vertebral arch that protects spinal cord
Centrum develops on ventral side of neural tube, tissue migrates from both sides around neural tube and meets to form vertebral arch
If arch doesn’t fuse together → spina bifida occurs (usually in lower back, varies in severity)
We can discover formation of nervous systems by watching animals grow from embryo to adult; we can’t use humans for ethical reasons
E.g. C.Elegans (flat form), M.musculus (Mice), D.melanogaster (fruit fly)
steps of neurulation
- neuroectodermal tissues diffferentiate form the ecotoderm and thicken into neural plate. The neural plate border separates the ectoderm from the neural plate
- the neural plate bends dorsally with two ends; eventually joining at neural plate borders.
- closure of the neural tube disconnects the neural crest from the rest of the epidermis.Neural crest cells differentiate to form most of the peripheral nervous system
- the noctoderm degenerates and only persists as the nucleus pulposus of the interverterbral discs. Other mesoderm cells differentiate into somites, the precursos of the axial skeleton and skeletal muscle
cerebral cortex + brain damage
responsible for consciousness, perceptions, memory, manipulation of objects emotional and expressive response and judgements to our environment.
It consists of four parts; the temporal lobe, the parietal lobe, the occipital lobe and the temporal lobe.
Brain damage would affect each part differently, resulting in possible paralysis, loss of emotional control, personality changes, sense-perception and language abilities and memory loss.
brainstem
The brainstem is responsible for sleep, alertness, breathing, sense of balance and the autonomic nervous system.
Brain damage could result in vertigo, sleeping difficulties (insomnia) and issues with balance and movement.
cerebellum
The cerebellum is responsible for coordination, balance and motor reflex memory.
Brain damage could cause loss of motor functions, such as walking and quick reaction, as well as dizziness and slurred speech.
how does Brain injury affects brain activity
causing the death of neurons and glial cells, and therefore also the connections between them caused by synapses and neurotransmitters.
Alternatively, brain injury can lead to the excessive production of neurotransmitters that overstimulate neurons, therefore causing neuronal death as they ‘combust’.
stroke
blocked, or limited, supply of blood to the brain that results in the death of cells and neurological damage, as the brain is being devoid of important nutrients and oxygen.
Recovering from strokes includes reforming neurons and learning basic functions, as it generally affects the left-hand side of the brain, and it can take up to 6 months for a patient to recover.
MIGRATION OF IMMATURE NEURONS:
- neural migration can occur by the use of contractile actin filaments moving the cell and its organelles in a given direction
- migration is particularly important in brain development; MATURE neurons don’t move, but regrowth can occur if dendrites or axons become damaged
Axons
are long narrow outgrowths from the cell body that carry impulses from neuron to neuron
axon growth
-axons grow out of each immature neuron (in some cases, axons grow out of the neural tube to other parts of the embryo)
- axon reaches a favourable surface and persists
- neurones reach their fianl locaiton and make synaptic connectsion with their target cells
- target cells produce chemical messengers to which the neurone responds to
- an axon in humans maybe up to 1 m long and large in larger animals
- chemical stimuli determine the direction and length of the axon (differentiation neurons; during the growth of the embryo)
- connections between neurons are highly branched; neurons commonly possess multiple dendrites for receiving impulses from different neurons and multiple terminal ends for passing signals to different neurons
Synapse;
a structure that permits a neuron to pass an electrical or chemical signal to another neuron or effector cell
synpase growth
When a growing axon reaches the cell it’s intended to connect with, a synapse is developed
Synapses consist of specialized membranes from two cells separated by a narrow gap (cleft)
Most neurons develop multiple synapses at both the initiating dendrites and terminal ends; this allows complex patterns of communication
What is Neural Pruning?
is the process of synapse elimination, by retraction of the axons from unwanted synaptic connections
(elemination of un-used synpases)
neural pruning process
Neurons communicate through synapses
As a baby, you have a lot of synapses (TOO MANY CONNECTIONS; Hyperactivity)
Weak synapses are pruned (removed) as you grow older
Neurons that send a lot of messages; the stronger the pathway; the stronger the connection (unused synapses are removed)
Largest process of synaptic pruning occurs during early life but it continues throughout the entire life
neural pruning diseases
Autism can be related to hyperactivity (lack of synaptic pruning)
Too much pruning; causes memory loss/dysfunction e.g. Alzheimers
Largest process of synaptic pruning occurs during early life but it continues throughout the entire life
Apoptosis of neurons?
Apoptosis of neurons; involves killing of the cell + elimination of all connections associated with the neurons
Cerebellum:
Cerebellum: Coordinates unconscious functions, such as movement and balance
Medulla oblongata:
Controls automatic and homeostatic activities, such as swallowing, digestion and vomiting, and breathing and heart rate
Hypothalamus
Maintains homeostasis via coordination of the nervous and endocrine systems, produces hormones secreted by posterior pituitary
Produces and secretes hormones regulating many body functions - such as ADH (water retention / osmoregulation)
Cerebral Hemispheres
Acts as the integration centre for highly complex functions, such as learning, memory and emotion
HOW DO WE IDENTIFY BRAIN FUNCTION?
- autopsy
- animal experiments
- fMRI
- lesions
animal experimentation
Animal experimentation has lead to many advances in science and medicine; particularly in neurobiology and treatment of neurological disorders such as multiple sclerosis
why are animals used in experimentation?
Animals are used rather than humans as the methods are highly invasive + potentially cause permanent damage.
Experimental results have limited validity as there are differences between human + animal brains ;
Most valid comparisons use primates as they are more closely related to humans
approaches of animal experimentations
Autopsy (dissection of brain)
Stimulating regions of the brain with electrodes (and then observing behaviour and movement e.g. Ferrier work with dogs and monkeys)
Lobotomy- removing regions of the brain and observing impairment of brain function (e.g. Flourens’ experiments on pigeons)
what is fMRI
fMRI is the primary tool used in modern research; it measures changes in blood flow through the brain (indicates which regions of the brain are the most active)
Measures can be made in real-time so regional brain activity can be correlated with a stimulus
Sequencing of brain activity (e.g. language comprehension followed by production can be observed)
Tool for medicine + research (e.g. ADHD and dyslexia can be diagnosed + stroke recovery monitored)
fMRI procedure?
The procedure is non-invasive and can be performed without injury; but it’s also an indirect measure as not all brain activity is detected
why does fMRI work?
fMRI works because oxyhaemoglobin responds differently to a magnetic field than (deoxygenated) haemoglobin; computer interprets the results to produce coloured brain activity (different colours often represents different levels of activity)
brain lesions
Lesions are abnormal areas in brain tissue caused by accidents or present from birth
Presence of a lesion is usually associated with damaged and loss of caution in the affected area
Complex functions often involved brain areas making results difficult to interpret
Brain plasticity, to a degree functions to be reorganized into undamaged areas
lesions origins
In 1861- French Physician Broca heard of a patient (Leborgne) with a 21-year progressive loss of speech and paralysis but who hadn’t lost comprehension or mental function
Broca predicted the presence of a lesion in the frontal lobe on the left cerebral hemisphere (Brocas area)
After Leborgne’s death; Broca confirms lesion using autopsy
Findings further confirmed using autopsies + fMRI
Correlation between body size + brain size
Bigger body mass= bigger brain required to control body; doesn’t mean that the animal is more intelligent (that depends on the ratio of the brain areas, synapses + neurons)
Brain size is limited by the metabolism of the animal
embrynogensis
: study of the bodies development from a fertilized egg to a fully formed organism
why is a frog used as an animal mode?
- verterbrate/chordata
- readily available for scintists to colelct
what is a higher chordata example
- birds
- warm blooded
- ferticle chick eggs
ectoderm
outer layer; becomes the brain and nervous system
endoderm
inner layer; forms the lining of gut and other organs
mesoderm
middle layer; develops into the skeletal, reproductive, circulatory, exxcretatory and muscular system
arscheteneron
cavity in centre of embryo
where do CNS neurone originitate?
neural trube
neuroblasts
precursors for neurones
differentiate into neurones
neurones grow towards their target cell
target cells give the chemical signals (e.g. CAM) to the neurone
neurones
Carry messages
gglial cells
do not carry messages
function; physical and nutritional support of neurone
provide a scaggolding network along with the immature neuron can migrate
CAM
- signal molecule released from target cell that acts as asignal to the growth cone
- cell adhesion moelcule located on the surface of cells in the growth environment of the axon
- growth cone of the axon has a CAM specific receptr
- CAM and receptor recognized each other + exchanged chemical messages= activates enzymes within neurone that contribute to axon elongation
chemotrophic factors
- receptors on a growth cone that can pick up signals of molecule secreted by target cells that diffuse into the extracellular environment
- can be attractive or repellent factors
chemoattractive factors; attract axon growth
chemorepellent factors; repell axon growth so it elongates in opposing direction
motor neuron axon extension
- some axons extend beyond the neural tube to reach their target s=cells
- responsible for voluntary muscle movement; motor neurones extend their axons out of the CNS to form circius
- new motor neurones; longest neurons in body
- CAM produced in enzymes to attract axons; activate enzyme to stimulate axon growth towards muscle
multiple synapses?
- many brain synpases formed during early brain development
- many synpases; test out different connections between nerve cells to find best one
- only synpases with fucntion survive while others disapperar
CAM synpase involvement
- CAM acts as lock and key; form physical but reversible bonds between cells axons
- its a neural adhesion molecule thats recruited to the site of connection
=eventually, connections are lost as their not good with their partner
neuromuscular junction
where growth cones of the axon and their target cell connect
types of plasticity
- structural; brain changes physical structure as a result of learning
- fucntional; abiliity of the brain to move functions fro a damaged to undamaged area
plasticity factors
- environmental
- heredity
EXAMPLE OF FUNCTIONAL SHIFT IN NEUROPLASTICITY
- tennis player has stroke; paralyses left arm
- during rehab; his good arm and hand are immobilized
- tennis player has to do a task with left hand; bad arm remembers how to move
- plays tennis again!
= functions in brain areas that were killed by stroke are transferred to healthy regions= new connections formed that are stimulated by activity
EXAMPLE OF STRUCTURAL SHIFT IN NEUROPLASTICITY
- study of london taxi drivers by McGill uni
- london taxi drivers; observed with MRI to see that their hippocampous is larger; for memory storage capacity
- structural change of hippocampus in taxi drivers increases with length of time driver has been doing routes
Cerebral Hemispheres: (right and left hemisphere)
The hemispheres act as the integration centres for highly complex functions, such as learning, memory and emotion
Higher order functions rely on input both from stimuli and memories
Sophisticated processes, such as reasoning, planning, self-awareness and morality, rely on a complex network of neurons (It is estimated that there are 1014 synapses in the brain)
Due to the huge complexity of these neural networks, how these functions work is only partially understood
Left and right cerebral hemisphere functions:
Some functions are limited to a particular hemisphere, but most functions are bilateral + dealt with by both sides of the brain
The right side of the brain receives stimuli from the left side of the body (and vice versa)
The left visual field from both eyes is processed by the right side of the brain (and vice versa)
The left side of the brain controls movement, muscle contraction, on the right side of the body (and vice versa)
This explains why stroke victims lose sensation and/or the ability to move limbs on half the body
Activities coordinated by the Medulla Oblongata:
Respiration + Breathing Heart and blood vessel function Digestion + Swallowing (peristalsis) + Vomiting Sneezing Pupil dilation’
cerebral hemispheres
integrating centre for higher compled functions
assosiated with; intelligence learning memory personality sensory impulses motor function organization problem solving
hypothalumus
control pituitary gland which secretes hormones
- coordinates nervous and endocrine systems
- maintains homeostatis
cerebellum
assosiated with regulation and coordination of movement and balance
- two hemispheres + highly folded surface
- coordinates UNCONSCIONS FUNCTIONS
medulla oblongata
maintains vital body functions such as breathign and heart rate (autonomic and homeostatic activities)
piutitary gland
secretes hormones; has two lobes;
- posterior lobe
- anterior lobe
each love controlled by hypothalmus to secrete hormones
role of medulla oblongata
- swallowing centre; coordinates mouth, throat and adams apple movement to make sure food goes own oesuphogus and not wind pipe
- controls breathing by controlling carbon dioxide levels in blood
- cariovascular centre; controls heard rate by excersixe or stress exposre
right hemisphere
recieving and analyzing information that comes from our senses
left hemisphere
all forms of communication
autonomic nervous system
has two divisions;
1. central nervous system; brain and spinal cord
- peripheral nervous system;
. peripheral nervous system
- peripheral nervous system;
- somatic (voluntary); infromation recieved by senses + messages sent to skeletal muscles; takes sensory information from sensory receptors in CNS and then returns them to motor commands from CNS to muscles (e.g. reflex arc)
ANS: invountaryl regulates glands, muscle and heart activitty (medulla oblongata)
- autonomic (involuntary); controls cardiac mucle, smooth muslce
- sympathetic system
- parasympathetic system
sympthatetic system of PNS
important in emergency
response is fight or flight
neutrotransmitter is noadrenanline
exictatory
parasynpathetic system
important in returning to normal
response is to relax
neurotransmitter is acetylecholine
inhibitory
pupil reflex
The pupil reflex originates in the brainstem and is under the control of the autonomic nervous system
pupil reflex process
Stimulus: bright light
Receptor: photoreceptors on the retina detect potential damaging levels of light
Coordination; sensory neurons in the optic nerve send impusles to the medulla oblongata.
Relay and then motor neurons direct the impulse to the irsis muscles
Effect: Radial muscles relax + circular muscles contract to constrict the size of the pupil
Failure of the pupil reflex indicates the damage to the medulla oblongata (brain stem)
If brain stem fails; basic automatic brain function can fail
sensory and motor neurones in pupil reflex
connect in brain rather than spinal cord (cranial reflex)
pathway of pupil reflex
- optic nerve recieves messages from retina at back of the eye; retina contains photorecetpors that recieving light stimulues
- photoreceptors synpase with bipolar neurons and then with ganglion cells (nerve fibres of the ganglion cell become the opitc nerve)
- optic nerve connects with pretectal nuclear of brain stem
- from the pretectal nucleus; a message is sent to the Edinger-Westphal nucleus; axons of which run along the oculomotor nerves back to the eye
- oculomotor nerves synpase on the ciliniary ganglion
- axons of ciliary ganglion stimulate the circualr muscle of the iris
brain death
- its possible to artificialyl maintain the body without the impulses that come from the brain (e.g. heart rate, breathing and blood flow, temperature, fluid retention etc)
- people can live on life support; but brain shows no electrical activity
- ‘the time when a physician has determined that the brian and brain stem have irreversibly lost all neurologiacal function”
what tests must a physician do to test for brain death?
- . toxicology test (make sure the patient isnt under drugs)
- test movement of extremeties (no movement or hesitation in arm/leg fall)
- eye movement; no eye rolling
- corenal reflex; no eye blinking
pupil reflex; no constriction in response to light
gag reflex; insercetion of small tube into throat causes no reaction
respiration; no breathing response when patient is removed from ventilator
issues with brain dead people?
they can still have spinal refelxes;
knee jerk response canstill be functional
what further tests are ussd to confirm brain death?
- electroencephalogram (EEG); measures brain activity in microvolts
- cerebral blood flow (CBF); radioactive isoptopes injected into blood stream and seen if there is brain activity
cerebral cortex
- front part of nueral tube
- consits of left and right cerebral hemispheres
- covered by thin layer of grey mater; cerebral cortex
cerebral cortex functions
- reaosning
- language
- complex thought
- visual processing
- motor movement
- remembering
- speech
prefrontal cortex
organizes thoughts, solves problems, formats strategiest
motor assosiciation cortex
coordinates movement
primary motor cortex
plants and executes movements
primary somatosensory cortex
processes information related to touch
sensory association cortex
processes sensory information of perceptions or multisensory information
visual association area
processes visual information
visual cortex
recognizes visual stimuli
wernicke’s area
processes auditory information
auditory association area
processes auditory information
auditory cortex
dectects sound quality (loudness or tone)
broca’s area
produces speech and language
- with brain injury patienst affects their speech
- paul broca discovered this as the language function
nucleus accumbens
- reward circtui in brain
-respponds to dopamine and seratonin neurotransmitters
dopamine; promotes desire
seratonin; inhibits desire
drugs such as cocain + nicotine increase dopamine production= results in addiction
brain metabolism
brain metabolism requires large energy inputs
- neurons have a lot of mitochondria for ATP
- brain cells need twice as much energy than any other cell
- glucose; primary energy source (neurones cant store gluose so blood must deliver it) ,hence good carbs are food for the brain!
what does the left cerebral hemisphere control and vice versa?
the right side of the body (muscle contraction and sensory information)
mechanoreceptors
- stimulated by mechanical force or pressure
- sense of touch; caused by pressured receptors that are senstiive to strong or light pressure
- arteries; pressure receptors detect blood prssure changes
- lungs; stretch receptors respond to degree of lung inflation
propriorectopors; muscle position and movement; for posture and balance
inner ear; pressure receptors senstivie to fluid waves; equilibirum
chemo receptors
response to chemical substances (taste and smell)
- blood vessels; pH changes which adjust breathing rate
pain receptors; respons to chemical released by dmaged tissues
olfactory receptors; smell response
photorecetpors
respond to light energy
found in eyes; responsible for vision
rod cells and cone cells
thermoreceptors
respond to change in temperature
located in skin
Stimulus:
Stimulus: a change in external or internal environment that is detected by a receptor and elicits a response
Response:
Response: change in behaviour in reaction to a stimulus
reflex
reflexes are rapid, involuntary or autonomic response to a stimulus (e.g. constriction of the pupil in bright light)
Reflexes are the produce of natural selection
Rapid and unconscious responses allow for danger avoidance with minimal harm to the organism- so pain is a good thing!
T
he pain reflex is moderated by the spinal cord rather than the brain- shorter paths, faster response and no conscious decisions needed!
Olfactory receptors= sensory smell
Olfaction occurs in the upper part of the nose
The combination of impulses reaching the brain allows us to recognize many different types of smell
Receptor cells possess cilia which project into the air in the nose
Olfactory receptor proteins are located in the membrane of the cilian; different olfactory receptors respond to different chemicals
1. Factors bind to receptors
2. Olfactory receptor cells are activated and send electrical signals
3. The signals are relayed via converged axons
4. The signals are transmitted to higher regions of the brain
iris
regulate pupil size
pupil
admits light
retina
contains receptors for vision
aqueious humour
tranmits light rays and supports eye ball
vitreous humour
tranmits light rays and supports eye ball
rods
allows black and white vision in dim light
cones
allows colour vision in bright light
fovea
area of densely packed cone cells where vision i smost acute
lens
focuses the light rays
slcera
protects and supports eyebal
cornea
focusing beings here
choroid
absorbs stray light
conjunctiva
covers sclera and cornea to keep eye moist
opitc nerve
transmits impulses to brain
steps of vision pathway
- rod and cone recieve light simulus
- rod and cone synpase with bipolar neurone
- bipolar neurone carriers impulse to ganglion cell
- ganglion cell located in optic nerve
- optic nerve carries impulse to brain
rods
- photoreceptor cells that are snesitive to light; recieve simulus of dim light and synapse with bipolar neurone
-more senstiive to light and function well in dim light
-one one type of rod found in retina; can abosrb all wavelengths of visible light
-impulses from group of rod cells pass to a single nerve fibre in the optic nerve
found along/all around the retina
cones
photoreceptor cell activated by bright light
recieve bright light stimuu and synpase with bipolar neurone
function well in bright light + less senstivie to light
three types found in retina (red, green and blue vision)
impulse from a SINGLE cone cell passes to single nerve fibre in optic nerve
found in fovea
red-green colorblindness
Sex- linked disease
Affects males more (as its an X recessive disorder)
Genes are found on locus Xq28
Genes are responsible for producing photoreceptive pigments in the cone cells in the eye; if one of these genes cannot distinguish between green (medium) wavelengths and red(long) wavelengths in the visible spectrum
Because the gene is a non-homologous region when compared to the Y chromosome, rg blindness is a sex linked disorder, as the male has no allele on the Y chromosome to combat a recessive faulty alleles on the X-chromosome
bipolar neurones
cells in the retina that carry impulses from a rod or cone cell to a ganglion cell of the optic nerve
bipolar because have two processes extending from cell body
ganglion cells
synapse with bipolar neurons and send impulses to the brain via optic nerve
eyelid function
protect the eye
Visual Fields
the range over which an eye can detect visual stimuli
visual processing
light from your left visual field falls onto the right side of the retina and vice versa
Stimuli from both left retinas are processed in the left visual cortex of the occipital lobe; therefore both sides of the brain process images from both eyes
Images are focused by the cornea and lens; an inverted image is focused on the retina
Both eyes send visual information to both sides of the brain; this is achieved through the optic chiasm (where information from the inner halves of the retinas are crossed over)
The optic tracts carry the visual nerve impulses to the visual cortex in the occipital lobe; this is called contralateral processing
This means that both sides of the brain are responsible for processing information from both eyes
How sound is perceived by the ear (IB answer);
Sound travels as pressure waves in the air which push the membrane of the eardrum, causing it to vibrate. The degree of vibration will vary according to the frequency and amplitude of the sound waves.
· - eardrum(tympanic membrane) is moved by sound waves
The eardrum pushes on the bones of the middle ear (the ossicles; malleus, incus and stapes), which magnify the vibrations (~ 20 times).
· The ossicles push against the oval window, displacing fluid within the cochlea.
· Movement of the cochlear fluid affects the position of cilia on sensory hair cells. Cilia on hair cells vary in length and each resonates to a different frequency of sound. Hair cells are mechanoreceptors; respond to different wavelengths/pitches
· Activation of the hair cells generates nerve impulses (neurotransmitters) which are transmitted via the auditory nerve to the brain; sounds/vibrations are transformed into nerve impulses (action potentials) carried by auditory nerve
· The kinetic motion of the cochlear fluid is dissipated (dispersed) by the movement of the round window. (round window releases the pressure and dissipate the sound allowing the fluid in cochlea to vibrate)
Pinna
Pinna:
Collection of sound waves
ear drum (tympanic membrane)
Eardrum
Vibrated by air pressure due to changes in sound waves
oval window
Oval window
Transmits vibrations from middle ear bones
round window
Round window Dissipates vibrations (dampens ‘used’ sound stimulus)
cochlea
Cochlea
Tiny hairs response to individual wavelengths of sound, generating AP
Semicircular canals
Semicircular canals
Balance (not hearing)
Auditory nerves
Auditory nerves
Transmit nerve impulses from cochlea to brain
Eustachian tube
Eustachian tube
Joins throats and sinus; for equalisation of pressure
Middle ear bones
Middle ear bones
Stimulated by ear drum, knock against each other and magnify sound (around 20x)
sound
Sound is vibrational energy that initiate sound waves that stimulates hairs in the ear cell to stimulate neurons to send messages to the brain
Frequency (affect pitch)
Amplitude (affects volume/loudness of sound)
Sound waves have to reach the ear and are converted to action potentials that the ear understands
cochlear implant?
Cochlear implant is a surgically implanted device that helps to correct hearing loss associated with damaged cochlear hairs
Its function is to generate electrical signals from sound vibrations and transmit them to your auditory nerve
Implant turns sound information into electrical signals that are sent + understood by the brain
Electrodes directly stimulate the auditory nerve to send the sound information to brain
New mechanism for hearing; bypasses the damage in the ear
Ear damage; damage to the hairs; very loud sounds (e.g. explosion) or continuously listening to loud sounds (music)
structures of middle ear transmit and amplify sound?
- bones of middle ear (incus, malleus, stapes) recieve vibrations from tympanic membrane and amplify them 20 times
- stapes strike oval window causing it to vibrate
- vibrations pass along cochlead fluid
- cochlea fluid has hair cells; they vibrate
- hair cells (mechanoreceptors) release neurotransmitters across synpase to sensory neurone of auditory nerve
- vibratiosn transformed into nerve impulses
- chemical message stimulated by sensory neurone
- impulses caused by sound perception trnasmitted to brain by auditory nerve
- round window releases pressure so fluid in cochlea can vibrate
sensory hair in cocholea
-detect sound of specific length
- internal change produces electircal impulses
-short high frequency waves; high pitched sounds
long, low frequency waves; low pitche dsound
-sound is percieved in auditory area of cerebral fortex
ear damage
- damage to hair cells in cochlea hair cells
- produced by large noise/continous listneing to loud music
hair cells + movement
- semicircular canals in ear maintain our equillibrium
-canals contain fluid and hair cells; movement of fluid over hair cells detercts rotaionsal movement of head
-hair cells act as sensory receptors; send messages to VESTIBULAR nerve
= allow for us to maintain balance
anosmia
inability to identify common smells
innate behaviour
- inherited from parents
- develops independetly of environment
- genetically based
- generally uniform; low variation in population
- less common in species of higher intelligence
- increases change of surviival and reproduction
e.g. mating, bird song, finger suckling in babies, spider webs
learned behaviour
- based on experience
- modified by individual on trial and error basis
- high variation among population
- highly affected by environment
- may or may not increase change of survival and reproduciotion
Capacity to learn may be a product of natural selection,rather than specific behaviours
Examples: Acquisition of language + social skills
Domesticated behaviours in pets
Training dolphins to perofmr
taxis
directed response to a stimulus
- taxes indentified by type of stimulis to which the organism responds
chemotaxis; respone to chemicals (e.g. drugs, food, pestcidies)
phototaxis; response to light (UB, fluorsecent, etc)
gravitaxis; response to gravity
rheotaxisl response to water current
thigmotaxis; response to touch
postive response; body towards stimulus
negative response; body away from stimiulus
planaria
- flatworm that lives in lakes and bonds
- active and moves my muscle contraction
- contains photoreceptors and chemorectpors
-negatively phototaxis (likes darkness; lives under leaves and rocks for portection)
postiviely chemotaxis; likes to eat food liek raw liver
euglena
- single clled protist
- has a flagelliu, and an eyespot stimulate by light
- makes its own food by photosynthesisis; is phototaxic postivley; needs light
kinesis
movement in a response to a non-directional stimulus
e.g. humidity
- rate of moevemnt depends on intensity of stimulus not direction`
- animal doesn’t move towards or away from stimulus; moves randomly untill it finds a comfort zone
slow movement vs fast movement
Orthokensis; when an organism changes its speed in response to a stimulus
Klinokensis; when an organism turns slowly or rapidly in response to a stimulus
ISOPODS
- terrestial crustaceans that show kensis
-live on land but have gills and need moist air
= humidity is important - move around quickly and randomly in dry environment untill they are in humid environment again
reflexes
- reflexers are quick response to a stimulus
- not controlled by brain
- controlled by autonomic nervous sytem
reflex arc
- compose of a receptor cell
- sensory neurone
- relay neurone in spinal cord
- motor neruone (carries message to effector; muscle)
reflexes are protective; pain or blink reflexes
pain reflex
- receptor cells receive stimulus (pain)
- receptors decect a stimule and generate nerve impulse to sensory neurone
- sensory neurone carries impulse towards spinal cord
- axon of sensory neurone enters spinal cord and sends chemical message across synpase to a realy neurone
- the realy neurone reynapses with the motor neurone and transfers the impiulse chemically across the synpase
- the motor neurone carries the impulse to an effector
- an affect is an organ the produces a response (e,g, muscle)
reflex conditioning
classifcal reflex condition can be used to modify a reflex response
e.g. play a music note before making someone blink by waving hand; at one point they will blink just to the sound of themusical note
unconditioned response: eye blink to waving hand
unconditioned stimilus: waving hand
Neutral stimulus: musical note with no effect
conditioned stimulus; musical note with effect
conditiones response; eye blink in response to musical note
learned behaviour
- not genetically programmed
process of gaining new knowledge and kills - learning can be measured by performance; explained by change in performance that is stored in nervous system as memory
operant conditioning
- form of learning; throug negative or positive reinforecement in behaviour in response to environment
- B.F. Skiiner used operant conditioner with rats and pigeons
- studied how they learnt that touching a lever gave them food; assosiate food with lever and the manipulate environemnt
- original bheaviour performed spontenaously during environmental exploration
- experiment changs the likelihood of this behavior being performed (the behaviour is called an operant)
- no intereference from experiemnter in experiment
- animal brings about chang in its envrionement by performance
learning
are all behaviours learned?
learning is the acquistion of skills or knowledge
Behaviour is response to a stimulus
Eating + reproduction main desires of animals
Morphology + physiology constrain behaviour + evolutionary behaviour
Some are learned, but a lot of them are genetic (adaptive/innate)
bird songs
- bird songs are a mixture of learned and inherited (inate) beahviour
- bird has inate bird song from parent; adapts and perfects it by learning (crude template; inate behavioural song )
- male birds change singing to attract females during sexual maturation
memory
process of retaining knowledge by encoding, storage and accessing
encoding
brain processes information and it receives form senses so it can be remembred
visual encoding elaborative encoding acousting encoding sesnation eoncidng etc.
storage
ability to store informaiton allows us to maintain the knowledge gained for a certain period of time
-storage occurs at the level of the neurone
- practice makes perfect; increased numbers of transmitted signals increases synaptic connections
= less practice; weakened synaptic connection
accessing
accessing is the retrieval of stored memories;
- short term memory; information held fr short period of time due to active thinking
- long term memory; information stored over long period of time; physical change to neural netrwork of brain
- recognistion; assosiation of physical object/event with something already experienced (comparitive knowledge)
- recall; rememberng a fact, object, event not currently present (activation of neurones involved in memory)
konrad lorenz
- ethologist
- studied imprinting in baby geese
- found that most crticial period was in 13-16 hours after hatching
- example of early learned behaviour; geese impring on any moving object
- beheaviour occurs regardless of consequences
ethology vs pscychology
ethology; study of animal behaviour in natural behaviour
pyschology; adopt an experimental lab approach in which external world of animal is tudied
pavlov vs jane goodall
nautral selection
- survival fitness of an animal (ability to survive and reproduce relative to the gene pool contribution to the next generation)
- changes in behaviour to surivve in environment genetically
migration in europan blackcaps
- genetic basis of behaviour and its change by natural selection
Sylvia atricapilla; migratory bird
Evolved over a decade
Learnt behaviour but then became genetic
Normal behaviour: in autumn most blackcaps migrate south to spain to avoid germany’s cold winter
Variation in behaviour; small number of blackcaps migrate northwest to UK
Selective advantage; shorter flight to the UK and a good supply of food (from bird enthusiasts). Bird wintering in the UK return to breeding site earlier than those migration south from spain (reproductive advantage; more food sources, nesting/territory choice/ hatchlings have longer time to develop before autumn migration)
Experimental evidence; eggs were taken from both populations + raised in captivity independent of parents; hatchlings persisting in following the migration patterns of their genetic parents
Natural selection; genes for north-west migration increased in frequency amongst the blackcap population
blood sharing in vampire bats
- example of the development of altruisitc behaviour by natural selection
Bats regurgitate blood to help other bats; ensure survival of species and mutualistic relationship
If bats don’t get blood in 48 hours; they starve and can die
To prevent this; bats regurgitate blood into mouths of starving bats to make them healthy
System works; bats return favours when roles are reversed for communal, continued survival
Animals can keep track of associations; bats won’t share blood as easily with new group members; BLOOD-SHARING associations built up over time
= bats keep track of blood sharing; benefit of skill is that bats recognized cheats and make sure that they are denied blood in the future
Wilkinson suggests that blood-sharing may be to avoid extinction in the last ice-age (disappearance of horse, camel, giant sloth reduced blood supply; these conditions favoured survival of bats if they share)
Similar environmental upheaval could be responsible for human altruism
altriusim
Why do animals look after other animal’s needs?
Altruism; helping others unselfishly
Reciprocal altruism: form of sharing/kindness that results in mutual benefit (to exist; it requires other animals to return favours regularly to grant large benefit at small cost)
Larger communities (extended animal); benefit of behaviour> cost of individual Inclusive fitness; include offspring of the relatives
foraging behaviour in shore crabs
- increasing chances of surivival by optimal prey choice
Shore-crabs (Carcinus maenas); break open medium mussels instead of big ones (even though big ones are have more energy) as it requires less energy expenditure + avoids damage to claws so that at reproductive time they aren’t as damaged
However, when food is scarce, they will elect suboptimal mussels to survival if no other options
breeding strategies in coho salmon
- bheaviour affecting surival and reproduction
Sneaker jacks in Coho salmon; breeding strategy behaviour aids more than physiology
Larger males outcompete smaller males for access to mates + food
Hooknose vs Sneaker jakes
Sneaker jacks not as prone to predators; smaller + less exposed to predators; quickly and more agile; can deposit sperm on eggs (not big but sneaky)
Hooknose: larger, however suffer from predation and fishing; fight for access to females with each other
courtship behaviour in the birds of paradise
-mate selection
Bird of paradise: (Courtship behaviour)
Male ‘lek’ behaviour; cleans up area, uses snake skin to either polish or increase snake scent, have sparkly + impressive plumage, practices courting dance and places berries to attract female
Strong males, can prep nest easily + have greater showy plumage
Trade off for males between having showy plumage + avoiding predation
Those that survive + successfully mate with a female pass on their genes for plumage + courtship dance behaviour
Genes for exaggerated plumage + courtship dances are selected for
synchronized oestrus in lions
- example of innate behaviour that increases the changes of survival and reproduction
Lionesses live in a pride together, with a small coalition of dominant males; most adult males live singularly or in a small coalition independent of pride (only dominant males can breed)
Female lions raise their cubs together in a creche (all work together to feed and protect cubs to increase the chances of survival for others)
Young male lions can more easily form coalitions with others to leave the pride at the same time; coalitions more successfully than single males in taking over a pride and breeding
Innate behaviour
Synchronized oestrus; become fertile at the same time; so birthing of cubs is close together
Lionesses all birth and raise cubs together
If one lioness dies, the others raise its cubs
Cubs born of equal ages; grow up together and avoid older cubs hurting younger ones
blue tits and learning
- feed on cream from milk bottles by blue tits as example of development and loss of learned bheaviour
E.g. Blue tits (Cyanistes caeruleus) and milk bottles
1921; People who had milk delivered to their door saw that the milk was consumed from the milk bottle
Blue tits as culprits; good nutrients for bird; behaviour spread through populations throughout europe
Introduction of aluminum foil bottle caps; did not to change behaviour
Behaviour rapidly disappeared in 1990’s (decline in doorstep behaviour + people tend to favour low fat milk + securer bottle caps)
Rapid spread and loss of the behaviour indicate that it’s a learned behaviour; spread of innate behaviour is limited to the production + survival of offspring
synaptic transmission
- presynaptic neurone transmits signal using neurotranspmitters in a synapse with the postsynaptic neurone
- synaptic cleft; space betwen neurones
interactions at the synapse
- impulses that move down presynaptic neurone is called action potential
- cuases vesciicles containig neutoransmitters to fuse with presynaptic membrane
- vesciles fuse with membrane and then released by excosytosis to synaptic cleft
- one in cleft, it bends to specific receptors in postynaptic membrane; act as gates to let ions enter ot leave when neurotransmitters bind to them
exictatory neurotransmitters
generate action potentials
- increase permeatbility of the postynaptic neurone to sodium ions
- causing Na+ ions to diffuse in
- so the neurone is depolarized; inpulse is carried forward
example; acetylcholine
inhibitory neurotransmitters
cause hyperpolarization of the neurone to make it difficult for an action potential to be genarated (make inside more negative)
- make the inside of the neurone more negative
- causes the Cl- to move in or K+ to move out
- hyperpolarizes the neurone
- impulse is inhibited
example; GABA (gamma-aminobytiric acid)
summation
postynaptic neurone recieves exictatory or inhibitory stimiulu and sums of the signals
- interactions at this place in between exictatory and inhibititory neurones; summation is the way that decisions are made by the CNS
slow vs. fast neurotransmitters
flow of ions either caues depolarization of hyper polartizaion
consists of 2 types;
fast acting NT’s
slow acting nT’s
fast-acting NTs
have an effect on the target cell wtihin 1 milisecond of binding to a receptor
slow acting NTs
have an effect on the target cell in hundres of miliseconds; can take up to a miniute
- acts as a second messenger moleucle
- knowing as neuromodulators; released into cerebrospinal fluid to modulate fast acting neutoranmitters;
- regulate effeciency of neurotransmitter release from presynaptic neurone
- regulate effiecienvy of post synaptic neurone
examples of slow NT’s
dopamine
seratonin
acetylcholine
synaptic transmission process
- many axons synapse with each cell body
- after an action potential arrives at an axon bulb, synaptic vesicles fuse with the presynaptic membrane
- neurotransmitter molecules are relased and bind to receptors on the postynaptic membrane
- when a stimulatory neurotransmitters bond to a recetpr, Na+ diffuses into the postynatic neurone
memeory + slow NT’s
- action of slow NT’s on neurones by allowing the brain to learn and have memory
seratonin Slow NT process on Aplysia in short term memory
- puff os seratonin acts on presynaptic neurone
- this causes an influx oc calcium ions into presynaptic neurone
- increase of calcium ions causes production of cylic adenosine monophosphate (cAMP); second messenger
- cAMP cativates protein kinase (PKA
- PKA enhances the relase of NT from presynaptic neurone into synapse
=result is short term learning in the gill withrdraw reeflex oc the Aplysia snail
how does long term memory differ from short term process?
- requires the synhtesis of proteins
- proteins needs activatino of genes in nucleus of neurone
- proteins change the form and function of synapse; results in memory
seratonin Slow NT process on Aplysia in long term memory
- 5 puffs of seratonin are given to increase seratonin level
- seratonin in the synapse is received by a receptor in the postynaptic membrane
- G protein is activiated; stimulated adenyl cylase enzyme immbedded in postynaptic neurone
- activated AC caues ATP molecules ot change to cAMP molecules
- high levels of cAMP being produced
- this activates PKA
- this signal reaches nucleus; activates transprcription; the genes make more proteins
- proteins travel out of nucleus and modify shape of synapse; create long lasting change in synaptic function
cholinergic synapse
- hyper polarization of neurone
- affects parasympathetic system
- synapses that use acetylecholine
- e.g. nicotine; calming effect
cholinergic synapse
- affects parasympathetic system
- synapses that use acetylecholine
- e.g. nicotine; calming effect
adrenergic synapse
- depolarization of neurone (exictatory)
- affects sympathetic system
- synapses that use nonadrenaline
- e.g. cocain and amphetatmiens stimulate adregenic synapses (cause alrentess, energy, euphoria)
effect of drugs on brain
- alter mood or emotional state
- act as synapses of the brain udsing different mecanisms; resulting in altered emotiona state
- can be exictatory (nicotine, cocain, ampehtative); increase likelidhood of nerve transmissions
- can be inhibitatory (alcohol, THC); decrease likelihood of nerve transmission
how do drugs change synaptic transmission?
- block a receptor for a neurotransmitter
- block release of neurotransmitter from presynaptic membrane
- enhance release of neurotransmitter
- enhance neurotranmission by mimicking neutornasmitter (similar chemical stucture)
- block removal of neurotransmitter from synapse; prolong effect
stimulants
- stimulation of sympathetic nervous system; excitatory
e. g. cocaine
THC
SEDATIVE
Without:
Dopamine release is moderated (inhibited) by GABA
With;
- THC mimics anandamide cannabinoids and inhibits GABA release by binding to cannabinoid receptors
GABA cannot inhibit dopamine release therefore more dopamine is released
Dopamine involved in reward pathways and causes enhanced pleasure feelings
Intoxications
Hunger
Memory impairment
Potential dependency
COCAINE
STIMULANT
Without cocaine
- dopamine is re uptaken by pumps on the presynaptic membrane
With cocaine;
- cocaine blocks reuptake pumps
- dopamine remains in synaptic cleft
- more dopamine continues to be released
- summative increase in postsynaptic transmission
Dopamine is involved in reward pathways; caused enhanced feelings of pleasure, which last longer than normal
- feelings of euphoria
- increased energy and alertness
- highly addictive
- association with depression as body reduces production of own dopamine over time
genetic predisposition
Many genes with roles in addiction have been identified, using animal models
For example the A1 allele of the dopamine receptor gene DRD2 is more common in addicts
social factors
Social environment plays a role; individuals raised in environments with prevalent substance abuse are at higher risk
Peer pressure (from those that use drugs), poverty, social deprivation, traumatic life experiences and mental health all increase the likelihood of drug addiction
Culture, religion and traditions can both positively/negatively affect addiction; explains variation in addiction patterns found between different countries
anaesthetics
Anaesthetics are very varied group of molecules that affect neural pathways in different way
How different anaesthetic work is not fully understood, but it is known that many do affect the receptors found in synapses
General anesthetics block ‘long distance communication’ hence affecting (often inhibiting) the transmission of impulses from receptors (areas of sensory perception) and the CNS
Anaesthetics cause a temporary loss of sensation, there are two main types;
LOCAL; cause numbness (loss of sensation) in an area of the body e.g. feeling of the gums during dental procedure
GENERAL; cause unconsciousness and therefore a lack of sensation throughout the body
Many anaesthetics have multiple roles and hence affect the body in different ways, due to this and the incomplete understanding we have of them they are usually administered by specialised medical practitioners called Anaesthetists
endoprphins
- neurotransmitters that cause pain relief
- released by pituitary gland during stress, excersize and injury
- small peptides that bind to opiate receptors
- similar action to morphine, heroin
- block pain transmission at in site of pain perception + block release of pain stimulating neurotransmitters
MDMA
Ecstasy is a reactional designer drug that users take to feel energise, happy, awake and dance. MDMA is the active component. The effect takes about 30 minutes to start and tend to last between 3-6 hours, followed by gradual comedown
Users often develop temporary feelings of love and affection however some users experience anxiety/panic attacks
Mephedrone and methylone are active components of bath salts
Saline is the control
sertatonin
Seratonin: neurotransmitter that contributes to a sense of well being and happiness
MDMA + seratonin: MDMA causes extra sereatonin to be released
- axon of neurone 1 releases seratonin into synapse
- recetpro on neurone 2 is activated by seratonin
- a SERT (seratooin transporter) bseicle on neurone 1 will take up all extra seratonin in synpase and pump it back in when needed
- MDMA forces seratonin axons to release a lot of seratonin; good feeling is replaced by depression as people deplete seratonin levels
MDMA and dopamine
- when setaonin is depleted, the SERT receptors are empty
- dopamine enteres the SERT receptor by mistake
- dopamine is broken down and the products are toxic to seratonin producing neurones
- neurotoxicity; can cause long term lasting damage to the brain cells ;o;;; them or impair their fnciont
acetylcholine
Acetylcholine (ACh) is an example of an excitatory neurotransmitters
It causes an influx of positive sodium ions into the postsynaptic neuron making the membrane potential more positive until the threshold is reached (at 50 mv) at which point the postsynaptic neuron starts to depolarize
GABA)
Gamma aminobutyric acid (GABA) is the main inhibitory neurotransmitter in mammals
It hyperpolarizes postsynaptic neurons by causing an influx of negative chlorine ions making the neuron’s membrane potential more negative; a release of GABA means that it’s harder for ACh to enact depolarisation in the postsynaptic neuron; it either takes longer for the threshold to be reached or the action potential is inhibited and doesn’t occur
alcohol
SEDATIVE
Without alcohol;
-GABA inhibits the postsynaptic transmission
-glutamate is an excitatory NT that binds to receptors increasing postsynaptic transmission
With alcohol;
-alcohols increases inhibitory effect of GABA by causing GABA to remain bound to its receptor for longer
-alcohol binds to glutamate receptors preventing glutamate from stimulate the postsynaptic neuron
Indirectly causes a dopamine released= enhanced
feelings of pleasure
- calm, relaxed feeling
- memory impairment
- increases (worsens) reaction speed
- affects breathing, body temperature regulation and appetite
- potential dependency
nicotine
STIMULANT
Without nicotine:
- dopamine is re uptaken by pumps on the presynaptic membrane
with:
-nicotine mimics the action of ACh; it binds to ACh receptors triggering action in the postsynaptic neuron
-unlike ACh Nicotine is not easily broken down and remains in synaptic cleft and continues to stimulate the postsynaptic neuron
ACh causes the release of dopamine, which in turn causes enhance feelings of pleasure
-feelings of euphoria
-increased calmness and alertness
-addictive; brain develops a tolerance for nicotine as it becomes needed for normal function
Addiction:
Addiction: dependence on a substance or activity resulting in its repeated and compulsive use
Breaking an addiction is very difficult and can cause severe physical/mental reactions (withdrawal)
What factors influence whether someone is an addict or not?
What factors influence whether someone is an addict or not?
Psychological; isolation vs happy/connected lives
Addiction is about the cage; adaptation to environment
Existing bonds and connections/healthy relationships
Nurture
Genetic
Socioeconomic conditions
dopamine action
Dopamine secretion
Dopamine activates pleasure pathways of the brain; it is normally released to reward positive behaviours
Many drugs affect, often enhancing, dopamine activity (e.g. cocaine and heroine)
Abuse of some drugs to lead to down-regulation of dopamine receptors, requiring higher doses to achieve same effect (habituation; to get used to it)
Speeding up of drug approval
Rigorous testing of drugs is important to determine; Effectiveness That it’s safe to use Appropriate dosage Side effects Takes a lot of time.
Ethical concern;
Testing process takes years to complete, so that the time patients are suffering and possibly dying from a condition that a drug under development could treat
In this situation, patients and their advocates will pressure health services and governments to speed up the drug’s approval; increases the risk of the drug causing harm to the patients
E.g. Ebola crisis in West Africa in 2014/5 + ZMapp Drug; promoted fast tracking of experimental drug ZMapp
