Unit 3 - Let’s Achieve Flashcards
What does the CNS consist of?
The central nervous system (CNS) consists of the brain and the spinal cord.
What does the peripheral nervous system consist of?
The peripheral nervous system consists of the somatic nervous system (SNS) and autonomic nervous system (ANS)
What does the Somatic nervous system contain
The somatic nervous system contains sensory and motor neurons.
Sensory neurons take impulses from sense organs to the CNS. Motor neurons take impulses from the CNS to muscles and glands.
What does the autonomic nervous system consist of?
The autonomic nervous system (ANS) consists of the sympathetic and parasympathetic nervous systems.
Difference in sympathetic and parasympathetic nervous systems
Sympathetic and parasympathetic nervous systems work antagonistically (opposite).
Sympathetic nervous system
Increases:
- heart rate
- breathing rate
Decreases
- peristalsis
- gland secretions
Parasympathetic nervous system
Increases
- peristalsis
- gland secretions
Decreases
- heart rate
- breathing rate
Converging neuronal pathways
In a converging pathway, impulses from several neurons travel to one neuron which increases the sensitivity to excitatory or inhibitory signals.
Example: Convergence of neurons from rods in the eye.
Diverging neuronal pathways
In a diverging pathway, impulses from one neuron split to travel along several neurons which affects more than one destination at the same time.
Example: Fine motor control of the fingers.
Reverberating neuronal pathways
In a reverberating pathway, neurons later in the pathway link with earlier neurons which sends the impulse back through the pathway. This allows repeated stimulation of the pathway.
Example: The medullas control of breathing rate.
Cerebral cortex
The cerebral cortex is the centre of conscious thought. It recalls memories and alters behaviour in light of experience.
Cerebral cortex - localised areas
The cerebral cortex contains localisations of areas:
- Sensory areas
- Motor areas
- Association areas – (involves language processing, personality, imagination and intelligence).
Hemispheres of the brain
Information from one side of the body is processed in the opposite side of the cerebrum.
The left central hemisphere deals with information from the right visual field and controls the right side of the body and vice versa.
The transfer of information between the cerebral hemispheres occurs through the corpus callosum.
What does memory involve
Memory involves encoding, storage and retrieval of information.
Information pathways
All information entering the brain passes through sensory memory and enters short term (STM). Information is then either transferred to long-term memory (LTM) or is discarded.
Sensory memory
Sensory memory retains all the visual and auditory input received for a few seconds. Only images and sounds are encoded into short term memory.
Short term memory
Short term memory only has limited capacity (5-9 items) and holds information for a short time. This is known as memory span.
Adding extra items will mean that items are lost or displaced.
Chunking
Chunking has the ability to increase the capacity of the short-term memory by grouping information.
Memory span and the serial position effect
When trying to remember items in sequence or order, the serial position effect can be very important. It will show primacy and recency with items ‘middle items’ being lost.
Working memory model
Our working memory is an extension of our STM.
It is able to process and manipulate the data in our STM.
Long term memory capacity
Long-term memory has unlimited capacity and holds information for a long time.
How is information transferred from short term memory to long term memory
Transfer of information from short-term to long-term memory is by:
rehearsal, organisation and elaboration.
Rehearsal
Rehearsal – is regarded as a shallow form of encoding information
(rehearsing the same information over and over)
Elaboration
Elaboration – is regarded as a deeper form of encoding which leads to improved information retention.
(Makes the information more meaningful and easier to transfer to LTM)
Organisation
Organisation involves organising information into groups
eg colours/shapes/events
What aids retrieval
Retrieval is aided by the use of contextual cues relate to the time and place when the information was initially encoded into LTM.
Neurons
Neurons are specialised cells within the nervous system that transmit information to other nerve cells, muscle, or gland cells.
Most neurons have a cell body, an axon, and dendrites.
Myelin sheath function
The function of the Myelin sheath is to insulate the axon and increase the speed of impulse conduction.
What do Glial cells produce
Glial cells produce the myelin sheath and support neurons.
What does Myelin allow
Myelin enables nerve cells to transmit information faster and allows for more complex brain processes.
Why is the Myelination process important
The myelination process is vitally important for the healthy functioning of the central nervous system
How long does myelination last
Myelination continues from birth to adolescence.
Responses to stimuli in the first two years of life are not as rapid or co-ordinated as those of an older child or adult.
What does loss of myelin sheath cause
Loss of the Myelin sheath is caused by certain diseases and causes loss of coordination
Example: Multiple Sclerosis
What do neurons connect with and where
Neurons connect with other neurons or muscle fibres at a synaptic cleft.
What do neurotransmitters do involving the synaptic cleft
Neurotransmitters relay impulses across the synaptic cleft.
Where are neurotransmitters stored
Neurotransmitters are stored in vesicles in the axon endings of the pre-synaptic neuron.
Neurotransmitters (movement)
They are released into the cleft on arrival of an impulse. They diffuse across the cleft and bind to receptors on the membrane of the postsynaptic neuron.
How do electrical impulses change going across synaptic cleft
The electrical impulse changes to a chemical impulse as it is carried across the synaptic cleft.
What do receptors do involving signals
Receptors will determine whether a signal is excitatory or inhibitory.
Why might neurotransmitters need to be removed and how?
There may be a need for the quick removal of neurotransmitters by enzymes or the reuptake of neurotransmitters to prevent continuous stimulation of postsynaptic neurons.
What can synapses do
Synapses can filter out weak stimuli arising from insufficient secretion of neurotransmitters.
What must attach to receptors and what does this do
A minimum number of neurotransmitter molecules must attach to receptors in order to reach the threshold on the postsynaptic membrane to transmit the impulse.
This mechanism prevents the generation of impulses from weak/harmless stimuli.
How a series of weak stimuli can trigger an impulse
Summation of a series of weak stimuli can release enough neurotransmitter to trigger an impulse.
What are endorphins
Endorphins are neurotransmitters that stimulate neurons involved in reducing the intensity of pain.
What does increases levels of endorphins cause
Increased levels of endorphins are linked to the feelings of pleasure obtained from activities such as eating, sex and prolonged exercise.
What increases endorphin production
Endorphin production increases in response to severe injury, prolonged and continuous exercise, stress and certain foods.
Dopamine
Dopamine is a neurotransmitter that induces feelings of pleasure and reinforces particular behaviour by activating the reward pathway of the brain.
The reward pathway
The reward pathway involves neurons which secrete or respond to dopamine.
Agonists
Agonists are chemicals that bind to and stimulate specific receptors mimicking the action of a neurotransmitter at a synapse.
Example: morphine action leading to pain relief.
Antagonists
Antagonists are chemicals that bind to specific receptors blocking the action of a neurotransmitters at a synapse.
Example: Strychnine poisoning.
Why might neurotransmitter need to be removed? What do other drugs act as?
As there may be a need for the quick removal of neurotransmitters by enzymes or the reuptake of neurotransmitters to prevent continuous stimulation of postsynaptic neurons, other drugs act by inhibiting the enzymes that degrade neurotransmitters or by inhibiting reuptake of the neurotransmitter at the synapse causing an enhanced effect.
Example: Cocaine.
Pathogen
A pathogen is a bacterium, virus or other organism that can cause disease/harm.
Antigen
Antigens are molecules, often proteins located on the surface of cells that trigger an immune response.
Physical defence against disease
Closely packed epithelial cells found in the skin, inner linings of the digestive and respiratory systems are physical defences against disease.
Chemical defence against disease
Chemical defences include secretions such as tears, saliva, mucus and stomach acid.
Inflammatory response
Histamine is released by mast cells causing vasodilation and increased capillary permeability.
The increased blood flow leads to an accumulation of phagocytes and clotting elements at the site of infection.
Phagocytes
Phagocytes are white blood cells which recognise pathogens and destroy them by phagocytosis.
Phagocytosis
Phagocytosis involves the engulfing of pathogens and their destruction by digestive enzymes contained in the lysosomes.
Cytokines
Cytokines are protein molecules that act as a signal to specific white blood cells causing them to accumulate at the site of infection.
Lymphocytes and their types
Lymphocytes are white blood cells involved in the specific immune response.
There are two different types of lymphocytes – B lymphocytes and T lymphocytes.
How lymphocytes bind to antigens and the impact of antigen binding
Lymphocytes produce antibodies which have a specific type of membrane receptor which is specific for one antigen.
Antigen binding leads to repeated lymphocyte division resulting in the formation of a clonal population of identical lymphocytes.
B lymphocytes
B lymphocytes produce antibodies against antigens, which leads to the destruction of the pathogen.
Antibodies
Antibodies are Y-shaped proteins that have receptor binding sites specific to a particular antigen or pathogen.
Antibodies become bound to antigens, inactivating the pathogen.
The resulting antigen-antibody complex can then be destroyed by phagocytosis.
Hypersensitive response by B lymphocytes
B-lymphocytes can respond to antigens on substances which are harmless to the body. E.g. Pollen
This hypersensitive response is called an allergic reaction.
Apoptosis
Apoptosis is programmed cell death.
How T lymphocytes destroy infected cells
T lymphocytes destroy infected body cells by recognising antigens of the pathogen on cell membrane and inducing apoptosis.
T lymphocytes attach onto infected cells and release proteins which diffuse into infected cells causing the production of self-destructive enzymes which cause cell death.
The remains of the cell are then removed by phagocytosis.
What can T lymphocytes distinguish between
T-lymphocytes can normally distinguish between self-antigens on the body’s own cells and non-self-antigens on infected cells.
T lymphocytes - consequences of failure to regulate
Failure of regulation of the immune system leads to T lymphocytes responding to self-antigens. This causes autoimmune diseases.
Autoimmunity
In autoimmunity, the T-lymphocytes attack the body’s own cells which causes autoimmune diseases
such as type 1 diabetes and rheumatoid arthritis.
Formation and behaviour of memory cells
Some of the cloned B and T lymphocytes survive long-term as memory cells.
The development of memory cells provides immunity.
When a secondary exposure to the same antigen occurs, these memory cells rapidly give rise to a new clone of specific lymphocytes.
These destroy invading pathogens before an individual starts to show any symptoms.
Comparing antibody production during the primary and secondary responses
During the secondary response, antibody production is greater and more rapid than during the primary response.
How does HIV virus cause aids
HIV attacks and destroys T lymphocytes which causes depletion of T lymphocytes which leads to the development of AIDS.
Individuals with AIDS have a weakened immune system and so are more vulnerable to opportunistic infections, such as pneumonia and influenza.
Immunity through vaccination
Immunity can be developed by vaccination using antigens from infectious pathogens, so creating memory cells.
Immunity through vaccination - antigens
Antigens used in vaccinations can be inactivated pathogen toxins, dead pathogens, parts of pathogens and weakened pathogens.
Immunity through vaccination- adjuvant
Antigens are usually mixed with an adjuvant during production. Adjuvants are a substance which makes the vaccine more effective, so enhancing the immune response.
Example: - An aluminium-mineral based adjuvant is added to the Hepatitis A vaccine.
When does Herd immunity occur
Herd immunity occurs when a large percentage of the population is immunised.
Why is establishing herd immunity important
Establishing herd immunity is very important in reducing the spread of diseases.
How are non-immune individuals protected by herd immunity
Non-immune individuals are protected as there is a lower probability they will come into contact with infected individuals.
What factors does herd immunity depend on
The factors upon which herd immunity depends are:
- The type of disease
- The effectiveness of the vaccine
- The density of the population
Why are mass vaccination programmes designed
Mass vaccination programmes are designed to establish herd immunity to a disease.
What difficulties can arise when widespread vaccination is not possible
Difficulties can arise when widespread vaccination is not possible due to: -
- Poverty in the developing world.
- Vaccines are rejected by a percentage of the population in the developed world.
Antigenic variation
Some pathogens can change their antigens. This means that memory cells are not effective against them (think about mutations)
Antigenic variation occurs in the influenza virus explaining why it remains a major public health problem and why individuals who are at risk require to be vaccinated every year.
Why are clinical trials needed for a new drug/vaccine
Clinical trials are needed to establish safety and effectiveness before being licensed for use.
Factors involved in setting up clinical trials
Randomised- reduce bias in the distribution of characteristics such as age and gender
Double-blind - neither subjects nor researchers know which group subjects are in to prevent biased interpretation of results
Placebo-controlled - one group of subjects receives the vaccine/drug while the second group receives a placebo-control to ensure valid comparisons.
Clinical trials - group size importance
The importance of group size during clinical trials will reduce experimental error and establish a statistical significance.
End of trial - group size
At the end of the trial, results from two groups of a suitable size will:
- reduce the magnitude of any experimental error
- compared to determine whether there are any statistically significant differences between them.
Sympathetic - increase and decrease?
Increases:
- breathing rate
- heart rate
Decreases
- peristalsis
- gland secretions
Parasympathetic - increases and decreases?
Increases:
- peristalsis
- gland secretions
Decreases
- breathing rate
- heart rate
Why are neurotransmitters removed
Between electrical impulses, the neurotransmitters are rapidly removed from the synaptic cleft.
This prevents continuous stimulation of the postsynaptic neuron.
Methods of neurotransmitter removal - re-uptake
Re-uptake - neurotransmitter is reabsorbed back into presynaptic neuron and restored inside a vesicle ready to be used again.
Methods of neurotransmitters removal - enzyme degradation
Enzyme degradation- neurotransmitter is broken down by an enzyme into smaller inactive products which are then reabsorbed by the presynaptic neuron and resynthesised into an active neurotransmitter.
What does the SNS control
The SNS controls voluntary actions
E.g. movement of skeletal muscles
What does the ANS control
Responsible for involuntary control of the body including glandular secretion, maintaining organ systems and REFLEX movement of skeletal muscle cells
What does memory include
Memory includes past experiences, knowledge and thoughts.
How is information transferred between the cerebral hemispheres
The transfer of information between the cerebral hemispheres occurs through the corpus callosum.
What is our working memory useful for
Performing simple cognitive tasks
E.g. steps of a recipe
How can items be retained in memory and how can items be lost
Items can be maintained by rehearsal.
Items are lost by displacement and decay.
What do most neurons have
Most neurons have a cell body, an axon, and dendrites.
How can convergent neural pathways trigger an impulse
Convergent neural pathways can release enough neurotransmitter molecules to reach threshold and trigger an impulse.
When is the reward pathway activated
The reward pathway is activated when an individual engages in a behaviour that is beneficial to them, for example when eating when hungry.
What is the myelin sheath composed of
It is composed of protein and fatty substances.
What causes drug addiction
Drug addiction is caused by repeated use of drugs that act as antagonists.
Antagonists block specific receptors causing the nervous system to increase both the number and sensitivity of these receptors.
This sensation leads to addiction where the individual craves more of the drug.
Drug tolerance
Drug tolerance is caused by repeated use of drugs that act as agonists.
Agonists stimulate specific receptors causing the nervous system to decrease both the number and sensitivity of these receptors.
This desensitisation leads to drug tolerance where the individual must take more of the drug to get an affect.
What do phagocytes also release
Phagocytes release cytokines which attract more phagocytes to the site of infection.
Examples of neurotransmitters
Acetylcholine
Noradrenaline
