What are the components of the CNS?
The brain and spinal cord
What does the PNS consist of?
The somatic and autonomic nervous system
What does the somatic nervous system do?
Takes messages from the sense organs, along sensory neurones to the CNS while motor neurones take impulses from the CNS along motor neurones to muscles and glands
What does the autonomic system contain?
Sympathetic and parasympathetic systems which are antagonistic to each other
What does the sympathetic system do?
Prepares the body for action (flight or fight) by increasing heart rate, increasing breathing rate by allowing bronchioles to take in more air and decreases peristalsis and production of intestinal secretions
What does the parasympathetic system do?
Calms the body down returning to normal (rest and digest) by decreasing heart rate, decreasing breathing rate by constricting bronchioles so less air is taken in and increasing rate of peristalsis and production of intestinal secretions allowing the body to conserve resources and store energy
what is a converging neural pathway?
impulses from several sources are channelled towards and meet at a common destination.
what do converging neural pathways increase?
the sensitivity to excitatory or inhibitory signals.
what is a diverging neural pathway?
the route along which an impulse travels divides allowing information to be transmitted several destinations at once.
what is a reverberating neural pathway?
neurones later in the pathway form synapses with neurones earlier in the pathway forming a loop enabling impulses to be cycled and stimulated repeatedly.
what is the cerebral cortex?
the centre of conscious thought, where memories are stored and what alters behaviour in light of experience.
what is localisation?
distinct regions with s particular function. Contains sensory, motor and association areas
what are association areas?
concern language, processing, personality, imagination and intelligence.
what do the left and right cerebral hemispheres do?
the left cerebral hemisphere deals with info from the right visual field and controls the right side of the body
the right cerebral hemisphere deals with info from the left visual field and controls the left side of the body
how is info transferred across the cerebral hemispheres?
through the corpus callosum
what does memory involve?
encoding, storage and retrieval of info
what does memory include?
past experiences, knowledge and thoughts
what is sensory memory?
retains all visual and auditory input and only lasts a few seconds
what is encoded into the STM?
selected images and sounds
what s STM?
short term memory-holds a limited capacity and holds info for a short time
how can capacity be improved?
by chunking and rehearsal
what is chunking?
meaningful units of info
what is the serial position effect?
items at the start of a list and items at the end are remembered better than those in the middle
how are items lost from STM?
displacement or decay
what is displacement?
pushed out by new info
what is decay?
breakdown of memory trace
what is LTM?
long term memory-unlimited amount of info for a long time
how is successful transfer from STM to LTM promoted?
rehearsal, organisation (into logical categories) and elaboration of meaning (give meaning to an item)
how can info be encoded?
shallow encoding (rehearsal) or elaborative encoding (elaboration-deeper form of encoding leading to improved retention)
what are the 3 types neurones?
sensory, inter and motor
what is the basic structure of a neurone?
cell body
axon
dendrites
what is the function of the cell body?
contains nucleus so is the control centre
what is the function of the axon?
single nerve fibre that carries nerve impulses away from a cell body
what is the function of the dendrites?
pass impulses towards cell body
what are axons surrounded by?
a myelin sheath
what is the myelin sheath?
a layer of fatty material material that insulates the axon , greatly increasing the speed impulse conduction
what is myelination?
the development of myelin and continues from birth until adolescence
what is the difference between responses to stimuli in adults and in children?
response to stimuli in the first 2 years of life are not as rapid or coordinated as those of an older child or adult
if the myelin sheath is destroyed by diseases what will happen?
loss of coordination
what do glial cells do?
produce. the myelin sheath and support neurones
what is a synapse?
the region of functional contact between the axon ending of one neurone (pre synaptic neurone) and a dendrite of another (postsynaptic neurone)
what is the tiny gap between the post synaptic neurone and the pre synaptic neurone at the synapse called?
synaptic cleft
how are messages passed across the synaptic cleft?
by neurotransmitters stored in vesicles on the presynaptic neurone only
what is two examples of neurotransmitters?
acetylcholine and noradrenaline
describe what happens when an impulse passes through the presynaptic neurone
it stimulates several vesicles to move to the synapse, fuse with the membrane and discharge the neurotransmitters which diffuse across the synaptic cleft and bind to receptors on the membrane of the post synaptic neurone
what is done to ensure precise control and prevent continuous stimulation?
the postsynaptic neurones must remain excited for only a brief moment to pass on the impulse
how are neurotransmitters removed?
by enzyme degradation and reabsorption directly
what is enzyme degradation?
the enzyme breaks down neurotransmitters which is then reabsorbed and synthesised into new neurotransmitters.
what is enzyme reabsorption?
reabsorption of neurotransmitters to be stored in vesicles
what determines if the signal is excitatory or inhibitory?
the receptors present on the postsynaptic neuron
what needs to happen in order for an impulse to be transmitted?
a certain threshold of neurotransmitter molecules must attach to receptors otherwise they are filtered out due to being weak.
what is summation?
if a postsynaptic neuron were to receive info via several synapses (convergent pathway), this collective of weak stimuli could be enough to fire an impulse.
what are endorphins?
neurotransmitters that stimulate neurones involved in reducing the intensity of pain by combining with receptors synapses and blocking the transmission of the pain signal
where are endorphins produced?
in the hypothalamus
what are endorphins produced in response to?
severe injury
prolonged and continuous exercise
physical and motional stress
certain foods such as chocolate
what are increases levels of endorphins linked to? and give examples
feeling of pleasure such as:
eating
sex
prolonged exercise
what is dopamine?
a neurotransmitter that induces feeling of pleasure by stimulating the reward pathway which reinforces certain behaviour to satisfy a need that is beneficial such as hunger or thirst
give examples of neurotransmitter related disorders
alzheimers
schizophrenia
depression
how are neurotransmitter related disorders treated
by agonists and antagonists
what do agonists do?
bind to and stimulate specific receptors on postsynaptic neurones mimicking the action of naturally occurring neurotransmitters triggering normal cellular response
what do antagonists do?
bind to specific receptors on postsynaptic neurones and blocking the action of the neurotransmitter inhibiting normal cellular response
how do other drugs (inhibitors) work?
preventing the removal of the neurotransmitter ( by degrading the enzymes jorpreventing re-uptake) causing an enhanced effect
how do recreational drugs work?
they act like agonists an antagonists and affect the transmission at synapses in the brain
what can recreational drugs alter in the brain?
mood
cognition
perception
behaviour
what happens if recreational drugs affect neurotransmission in the reward circuit?
they are overstimulated
how is drug addiction caused?
the repeated use of drugs that act as antagonists-blocking specific receptors causing the nervous system to compensate by increasing both the number and sensitivity of these receptors
what does drug sensitisation lead to?
addiction where the individual craves more of the drug
how is drug tolerance caused?
by repeated use of drugs that act as agonists-stimulate specific receptors causing the nervous system to compensate by decreasing both the number and sensitivity of these receptors
what does drug desensitisation lead to?
drug tolerance where the individual must take more of the drug to get an effect
whites the body physical defence?
closely packed epithelial cells found on the surface of the skin and lining the body respiratory and digestive tracts
what is the body chemical defence?
secretions including tears, saliva, mucus and stomach acid are produced against invading pathogens
what causes the inflammatory response?
a physical injury such as a cut or invasion of microorganisms
what happens in the inflammatory response following injury?
mast cells in connective tissue become activated releasing large quantities of histamine
what does histamine do?
causes vasodilation and the capillaries to come more permeable
what does increased blood flow do in the inflammatory response?
leads to accumulation of phagocytes and clotting elements at the site of infection
what do phagocytes do?
recognise pathogens, engulf them and destroy them using digestive enzymes contained in lysosomes through phagocytosis
what do phagocytes release?
cytokines (protein molecules which act as a signal) attracting more phagocytes to area of infection
what are lymphocytes?
white blood cells involved in the specific immune response
what do lymphocytes respond to?
specific pathogens because they have a single type of membrane receptor which is specific for one antigen on the invading pathogen
what does the the binding of the membrane receptor and the antigen lead to?
the lymphocyte repeatedly dividing resulting in a clonal population of identical lymphocytes
what are the 2 types of lymphocytes?
B lymphocytes
T lymphocytes
what do B lymphocytes produce?
antibodies which bind to antigens inactivating the pathogen
what is hypersensitivity and what does it result in?
Lymphocytes can respond to antigens on substances that are harmless to the body (pollen) which can result in an allergic reaction
what do T lymphocytes do?
destroy infected body cells by recognising antigens of the pathogen on the membrane and inducing apoptosis
what is apoptosis?
programmed cell death
how does apoptosis work?
T lymphocytes attach to infected cells and release a protein which diffuses into the cell causing production of self-destructive enzymes. T he remains of the cells are then removed by phagocytosis.
how do T cells distinguish between their own surface molecules and cells with foreign surface molecules?
T cells have specific surface proteins
what does immune system regulation failure lead to?
T-lymphocyte immune response self-antigens meaning they attack the bodys own cells resulting in auto immune diseases such as type 1 diabetes and rheumatoid arthritis
what is the primary immune response?
a person is infected by a pathogen or toxin and their body produces antibodies
what does the ability to have specific surface proteins allow T cells to do?
to recognise self and non-self meaning normally there a no lymphocytes acting against the body own cells
what happens to some T and B lymphocytes in the primary response?
they survive long term as memory cells
what do the memory cells make?
a secondary response
what is the secondary response?
if exposed to the same antigen again the memory cells rapidly give rise to a new clone of lymphocytes producing a rapid and greater antibody production meaning the invading pathogen is destroyed before the individual shows symptoms
what does HIV stand for?
Human Immunodeficiency Virus
what does HIV do?
attacks and destroys T lymphocytes causing a depletion of T lymphocytes
what does HIV lead to?
the development of acquired immune deficiency disease (AIDs) which weakens the immune system making the person more vulnerable to opportunistic infections
what is immunisation?
the person by which a person develops immunity to a disease causing organism
how can immunity be developed?
by vaccination using antigens from an infectious pathogen, so creating memory cells
what does an adjuvant do?
makes the vaccine more effective by enhancing the immune response
what are the different forms in which an adjuvant is used?
inactivated pathogen toxins
dead pathogens
parts of pathogens
weakened pathogens
what is herd immunity?
a large percentage of the population are immunised which helps reduce the spread of diseases
how does herd immunity protect non-immune individuals?
there is less chance of the non-immune individuals coming into contact with an infected person
what does the herd immunity threshold depend on?
the type of disease
effectiveness of the vaccine
density of the population
what is designed to establish herd immunity?
mass vaccines programmes
when do difficulties arise in herd immunity/vaccines?
poverty in the developing world
rejection by a percentage of the developing world
what is antigenic variation?
when some pathogens can change their antigens meaning memory cells are not effective against them
why do people need to be vaccinated every year for diseases like influenza?
antigenic variation
why do we do clinical trials on humans?
to establish the vaccine/drug is safe and effective before they can be licensed for use
what is a placebo?
members of control group given placebo which is the same form of the treatment but without the active ingredient being tested
why do we use placebos?
to allow for a valid comparison to be made
what is a double blind trial?
neither members nor the doctors know whether they are receiving the active ingredient or the placebo
why do we do double blind trials?
to prevent bias interpretation of results
what is randomisation?
all relevant details are entered into computer and the computer randomly sorts the members into groups
why do we use randomisation?
to reduce bias in the distribution of age and gender
why is it important to use a large group size?
to reduce experimental error
improves statistical significance
ability to compare between groups for difference