Week 4 "Ageing and Control" Flashcards
What is the soma?
The cell body of a neuron
What are dendrites and where are they located?
Connecting to the soma (cell body) at the presynaptic end of a neuron.
What is the role of the axon?
where a (depolarisation) signal it transferred from the cell body to the synaptic terminal.
What is the purpose of myelin sheaths on the axon?
Myelin increases the speed of depolarisation signal along the axon as does not need to wait for membrane depolarisation under myelinated areas.
What is the three key parts of the synaptic terminal?
Presynaptic axon terminal-where neurotransmitters are released
Synaptic cleft- gap
Postsynaptic dendrite- neurotransmitters bind.
What is the resting potential of the average nerve cell?
-70mV
What drives this resting membrane potential?
Efflux of K+ would set the cell at -90mV but an influx of Na+ into the cell makes the cell more positive at -70mV.
What keeps the balance between K+ and Na+ in a resting state nerve cell?
The balance of these ions is regulated by the K+/Na+ pump.
How is an Action potential generated in a nerve cell.
- Excitatory stimulus opens ligand gated Na+ channels (causing Na+ influx)
- Membrane will depolarise till hitting “threshold” approximately -55mV
- At threshold voltage gated Na+ channels open (causing huge depolarisation with an overshoot)
- Voltage gated Na+ channels are inactivated at higher potential (closed) and voltage gated K+ channels open (efflux of K+)
Cell repolarises to -70mV
Specifically what order are ion channels utilised in an Action potential?
- Ligand gated Na+ channels (influx) (move potential to threshold)
- Voltage gated Na+ channels (influx) (responsible for large depolarisation with overshoot)
- Voltage gated K+ channels (efflux) repolarises cell while Voltage gated Na+ channels are inactivated after depolarisation.
How can an action potential be described.
- All or nothing response
2. Has a refractory period.
What is a neurotransmitter?
A chemical substance which is released at the end of a nerve fibre by the arrival of a nerve impulse.
Broadly what kind of effect can a neurotransmitter have on post synaptic dendrites?
Excitatory or Inhibitory
Describe what drives the release of neurotransmitters into the synaptic cleft.
- Action potential arrives at synapse.
- Voltage gated Ca+ channels open (Ca+ influx)
- internal Ca+ concentration drives vesicles containing neurotransmitter to fuse with membrane and be released into the synaptic cleft.
Where can released neurotransmitters bind?
They can bind to post synaptic receptors (mainly) but also bind to presynaptic receptors to affect the cell currently releasing neurotransmitters. (negative feedback)
What is another name for receptor coupling to an ion channel?
Ligand-gated ion channels.
What is the benefits of Ligand-gated ion channels?
- They are highly selective as to what can bind and activate the channel.
- They are very fast acting (something needed in nerve cells)
What is an example of a inhibitory neurotransmitter action?
Gaba neurotransmitters:
Will bind to ligand-gated (K+ or Cl-) channels to cause a hyperpolarisation in the post synaptic dendrite. cell has harder time hitting AP threshold
What is an example of an excitatory neurotransmitter action?
Glutamate neurotransmitters:
Activate ligand-gated Na+ channels (Na+ influx). will cause deoplarisation of the synaptic dendrite.
What determines the magnitude of neurotransmitter effect?
- Amount of neurotransmitter in the synaptic terminal (how much is stored in vesicles)
- Amount of neurotransmitter released
- Period of availability in the synaptic cleft (determined by reuptake/degradation)
- Number of receptors (presynaptic and postsynaptic)
Sensitivity of receptors
Parts of the Central Nervous System
Brain and spinal cord
Parts of the Peripheral nervous system
Consists of all the nerves and ganglia outside the brain and spinal cord.
What are the subclasses of the peripheral nervous system
Somatic Nervous system
Autonomic Nervous system:
- sympathetic
- parasympathetic
What is the general role of the brain stem?
respiration, HR, BP
What is the general role of the spinal cord
transmission of nerve signals from and to the brain.
What is the general role of the cerebellum?
balance
What are the 4 major divisions of the cerebrum and their function?
- Occipital lobe- visual input processing
- Temporal lobes-auditory processing
- Parietal lobe- sensation and feeling
- Frontal lobe- complex tasks-movement etc
What is the general role of the basal ganglia
motor activity
What is the role of the somatic nervous system
All voluntary muscular control
What are the two major pathwyas used by the somatic nervous system
- Somatomotor (efferent)- from brain to muscle
2. Somatosensory (afferent)- from sensory receptor to brain
What are the major functions of the autonomic nervous system?
- gut movement
- heart contractions
- visceral sensations
What is the best way to summarise the sympathetic system?
fight or flight
What is the best way to summarise the parasympathetic system?
rest and digest
What is the main mechanism which the nervous system uses to maintain homeostasis?
Negative feedback loops.
What is the difference between pharmacology and clinical pharmacology?
Pharmacology is the fundamental science behind chemical action within biological system (cells tissue etc) whereas clinical pharmacology is focused on pharmacology and its effects on patients.
What is pharmacodynamics?
Mechanism of action
What is pharmacokinetics?
what happens to a drug when inside the body. metabolism and excretion ect
What is pharmacogenomics?
effects on genetics and response to drugs
What is the difference between a drug and a medicine?
A drug is a chemical that causes change in a biological system
A medicine is a drug that is used to treat or prevent disease within the body.
What are the different names a drug may have?
- chemical
- generic
- trade
What are the four phases of pharmacokinetics within the body?
(ADME)
Absorption- drug entering the blood stream
Distribution- movement of drug around the body
Metabolism- alterations of drug in the body (usually by liver)
Excretion- disposal of drugs out of the body (usually by the kidneys)
What is parenteral form of drug admission?
Injections.
What is the speed of Intermuscular, intravenous and subcutaneous injections absorption
V-fast
M-medium
S-slow
What is bioavailability?
The proportion of a drug that enters the circulation system of the body where it can have an active affect.
What is Clearance vs Half life for a drug.
Clearance is the rate at which a drug is removed from the circulatory system (measured in litres/hour)
Half life is the time taken for a drugs concentration to be half of its original value.
What does it mean by a drugs in a steady state?
Steady state is the concentration of a drug remains within the therapeutic range between doses of a drug. (steady within a range)
Describe the drug action in terms of speed and effect.
ligand gated channels
Ligand activated- very fast(milliseconds), eg nicotinic or Ach receptors.
Describe the drug action in terms of speed and effect.
G-protein coupled receptors
secondary messenger generation- fast (seconds) eg muscarinic or Ach receptors
Describe the drug action in terms of speed and effect.
Kinase linked receptors
Kinases phosphorylates proteins, can cause protein synthesis effect very slow (takes hours) eg insulin
Describe the drug action in terms of speed and effect.
Nuclear receptors
Causes direct change in gene transcription and protein synthesis very slow (takes hours), eg steroids as they can access the nucleus eg oestrogen.
What is an agonist?
A drug that binds to a receptor and activates it.
What is an antagonist?
Binds to a receptor and activates it but does not produce the full effect of an agonist.
what is a Partial agonist?
A drug that competitively binds to a receptor but does not cause activation -instead prevents activation.
What is the general mechanism of a benzodiazepine?
Drug that binds to a Cl- channel to boost the effect of binding neurotransmitters. In this case the result is an increased suppression of neuron activity
What is the relationship between drug dose and response.
More drug = higher response
Until a plateau is reached.
What is Emax and EC50?
Emax = Dose in which greatest response is reached (plateau)
EC50 = Dose in which 50% response is reached
What effect would an antagonist have on the dose-response curve of an agonist?
The antagonist would shit the dose-response curve to the right (higher dosing required)
While it shifts to the right there is no impact on the curve itself.
What is the importance of receptor selectivity on the use of a drug.
The more specific the better. But offtarget effects are potentially dangerous and need to be monitored
Define drug Affinity
how well a drug will bind to a receptor
Define drug Efficiency
how well a drug will act when bound to a receptor
Define drug Potency
how much drug is needed to initiate a response
