Neuroscience Lecture 1 Flashcards
What are a Neurone’s properties?
EXCITABILITY- Ability to RESPOND to STIMULI.
CONDUCTIVITY- GENERATE electrical signals known as ACTION POTENTIALS.
SECRETION- Chemical NEUROTRANSMITTERS are used to bridge gaps at SYNAPSES between neurons.
How many neurones are there in the human brain?
86 billion.
How many connections can an average neurone make?
1000
What is the approximate charge across a membrane?
-70 mV
What is a chemical gradient?
Difference in SOLUTE concentrations across the membrane
What is an electrical gradient?
Difference in CHARGE across the membrane
How does the Na+/ K+ ATPase membrane protein PUMP work to sustain an ion gradient?
The pump pumps out 3 Na+ for every 2 K+ it brings in.
Works CONSTANTLY with the presence of ATP.
To maintain a resting potential.
What is the equilibrium potential of an ion?
Is the point which there would be no net movement of the ion across the membrane.
What is the equilibrium potential of Potassium and Sodium?
EK = -80mV ENa = +60mV
Which ion (Sodium/ Potassium) is the membrane for permeable to? Why?
Potassium, -80mV
The RESTING MEMBRANE POTENTIAL is around -70 mV in neurones.
What is each stage of an action potential?
- Membrane at Rest
- Local Potential
- Depolarisation
- Repolarisation.
- Absolute Refractory Period
- Relative Refractory Period.
- Hyperpolarisation
- Resting state.
Action Potential- Describe the membrane at rest?
At rest the membrane potential is around -70mV. Voltage gated SODIUM and POTASSIUM channels are now CLOSED.
Action Potential- Describe the membrane at its local potential?
Membrane potential RISES because of the opening of LIGNARD GATED ion channels (ion channels).
Do NOT reach threshold= Diminish and no action potential.
Threshold REACHED= Action potential will fire.
Action Potential- Describe the membrane at depolarisation?
Membrane has reached threshold potential.
Potential rises rapidly because VOLTAGE GATED SODIUM ION CHANNELS are OPEN.
Potassium channels remain CLOSED.
Action Potential- Describe the membrane at REPOLARISATION?
Membrane potential has peaked and falls back towards resting potential.
Voltage gated sodium ion channels = INACTIVATED. VOLTAGE GATED POTASSIUM ION CHANNELS = OPEN to bring membrane back to potassium equilibrium.
Absolute Refractivity Period?
Lasts for 1ms.
IMPOSSIBLE to fire ANOTHER action potential.
POTASSIUM CHANNELS= CLOSING.
SODIUM CHANNELS= INACTIVATED.
Relative Refractory Period?
Lasts for SEVERAL MILLISECONDS.
It is possible to fire an action potential, but a LARGER stimuli is required.
Potassium channels = closing.
Sodium channels = DE-INACTIVATED.
What is meant by the All or nothing response?
This principal shows the threshold is either reached and an action potential is produce or it is NOT.
How are action potentials unidirectional?
They travel along the axon and are then followed by the refractory period.
What is myelination? What does myelination do?
MYELINATION is when the neuron axon is INSULATED allowing for more RAPID conduction of the action potential.
What is continuous propagation?
CONTINUOUS PROPAGATION is where an action potential progresses along an UNMYELINATED axon.
What is saltatory propagation?
SALTATORY PROPGATION is where an action potential progresses along a MYELINATED axon.
What are areas without myelin called?
Nodes of Ranvier.
How does the nodes of ranvier allow for faster conduction?
Action potential jumps along these nodes.
How do you increase the speed an action potential travels?
LARGER DIAMETER of axon.
MORE MYELINATION.
What cells myelinated peripheral axons?
SCHWANN cells
What cells myelinated CNS axons?
OLIGODENDROCYTES
What is MULTIPLE SCHLEROSIS (MS)?
Autoimmune disorder when myelination of central nerves is targeted.
What is GUILLAIN- BARRÉ SYNDROME?
Autoimmune disorder when myelination of peripheral nerves is targeted.
At a chemical synapse the pre and post- synaptic elements, what is the gap they are separated called?
SYNAPTIC CLEFT.
Describe the stages of synaptic transmission?
- Action potential OPENS voltage-gated Ca2+ channels in presynaptic membrane.
- Ca2+ ions enter the presynaptic terminal, which TRIGGERS the RELEASE of ACh from vesicles.
- Ach DIFFUSES across the synaptic cleft.
- Ach interacts with Ach receptors which causes OPENS Na+ ion channels so there is an INFLUX of Na+ ions.
- The influx of Na+ ions produces an EPSP (excitatory postsynaptic potential).
- If the EPSP reaches -55mV an action potential is TRIGGERED in the postsynaptic neuron.
What is the main excitatory/ inhibitory neurotransmitter in the brain?
E- Glutamate
I- GABA
Name and give examples of 4 types of Neurotransmitter:
- Amino Acid Neurotransmitters- Glutamate, GABA, glycine.
- Monoamines Neutrotransmitters- Serotonin (5-HT).
- Catecholamines (Also monoamines)- Dopamine, epinephrine, norephrine.
- Peptide neurotransmitters- Substance P, endorphins
What monoamine neurotransmitters deprived from?
Amino acids.
What is the rate determining step of the synthesis of acetylcholine? Is it saturated or not saturated?
Chloline Acetylransferases (ChAt).
Not saturated.
What enzymes are need to produce domaine? Which is the rate determining step?
Tyrosine Hydroxylase (Rate determining step). Dopa Decarboxylase (DDC)
What receptors are used to transport glutamate into the vesicle?
Glutamate VGlut 1 Receptors.
What substrate is used as an example treatment for Parkinson’s Disease, targeting synthesis by providing additional substrate for dopamine production?
L- Dopa.
How are action potentials released?
- Action potential reaches the PRESYNAPTIC terminal.
- VOLTAGE GATED CALCIUM ion channels OPEN.
- INFLUX of Calcium ions.
- Influx of calcium ions cause the vesicles to BIND with the presynaptic membrane.
- Contents of vesicles is RELEASED by EXOCYTOSIS.
What is a receptor?
PROTEIN which INITIATES a CELLULAR response when activated.
Name 2 types of receptor:
- Ionotropic Receptor.
2. Metabotropic Receptor.
What does an ionotropic receptor give? Example:
For fast response.
Eg: nicotinic Ach receptor or NMDA receptor
What is a metabotropic receptor? Example
Protein + Protein + Signals, other ion channels.
Eg: Muscarinic Ach receptor, mGluR.
Where are receptors located?
BOTH the presynaptic and postsynaptic membrane
What are excitatory postsynaptic potential caused by? Name some examples.
EXCITATORY neurotransmitters.
Glutamate
Acetylcholine
Noradrenaline (NA) (norepinephrine or NE)
What are inhibitory postsynaptic potential caused by? Name some examples.
INHIBITORY neurotransmitters.
GABA
Glycine
Noradrenaline (NA) (norepinephrine or NE)
After an action potential triggers a release of GABA which crosses the synapse what happens in response to this?
GABAA receptors trigger OPENING of CL- ION CHANNELS.
Cl- influx which produces an IPSP.
postsynaptic neuron= LESS LIKELY to reach THRESHOLD
Less likely to fire an action potential.
What type of receptor is a GABAa and GABAb?
GABAA = Inotropic Receptor GABAB = Metabotropic Receptor
What is an agonist?
A chemical that BINDS to a RECEPTOR thus ACTIVATING the RECEPTOR to produce a molecular or cellular response.
What is a FULL agonist? Name an example.
Produces a COMPLETE molecular response.
NICOTINE: Full agonist of nicotinic Ach receptors.
What is a PARTIAL agonist?
Name an example.
Interacts with a receptor in an INEFFICIENT manner producing a less than maximal molecular response.
BUPRENORPHINE is a partial agonist of the u opioid receptor.
What is an INVERSE agonist?
Binds to a spontaneously activated receptor leading to a DEACTIVATION of the receptor.
If there is a full agonist and a partial agonist, what happens?
The responses will compete and the partial agonist will reduce the effect.
What is an antagonist?
A chemical that interacts with a receptor to INHIBIT the action of an AGONIST.
What is a competitive antagonist?
Binds to the active site to block the substrate binding.
What is a non- competitive antagonist?
Binds to the allosteric site which changing the shape of the active site.
Name 2 examples of how neurotransmitters are reabsorbed.
Excitatory amino acid transports (EAATS).
Dopamine transporters.
Name 2 examples of enzymes which break down neurotransmitters.
Acetylcholinesterase or monoamine oxidase.
Name 3 drugs which target the reuptake/ breakdown mechanism:
COCAINE: Blocks dopamine transporters so dopamine stays in the synapses longer.
ANTIDEPRESSANTS: Selective serotonin reuptake inhibitors.
NERVE AGENTS: Acetylcholinesterase inhibitors e.g. VX.
What is the voltage of a typical EPSP (Excitatory postsynaptic potential)? How often does it last for?
0.5 mV
20 milliseconds.
How many EPSPs are needed to reach the threshold?
30 EPSPs
What is Temporal Summation?
Single synapse receives many EPSPs in short time
What is Spatial Summation?
Many synapses receive EPSPs from many cells.
What are Glia?
Connective tissues of the nervous system which consists of different cells.
What are the cells in the CNS Nervous System? What are there functions?
• EPENDYMAL & MICROGLIAL CELLS- Form PERMEABLE BARRIER between CFS + tissue fluid.
• ASTROCYTES. Star shaped cells with numerous branches. MECHANICAL SUPPORT
Neurons with NUTRIENTS
Maintain EXTRACELLULAR ENVIRONMENT
REMOVE excess K+ ions Influence BLOOD SUPPLY.
They have PERIVASCULAR feet (near a blood vessel).
OLIGODENDROYCTES- MYELINATE multiple CNS neurons.
What are the cells in the PNS? What are there functions?
- SATELLITE CELLS- Surround cell bodies in PNS ganglia to give physical SUPPORT and CONTROL substances ENTERING/ LEAVING cell body.
- SCHWANN CELLS- MYELINATE PNS FIBRES by wrapping around them.
What is the central nervous system? Characteristics of CNS.
Brain and Spinal Chord.
Protected by bone and does not regenerate after injury..
What is the peripheral nervous system? Characteristics of the PNS.
Everything outside the brain and the spinal cord.
Not protected by bone and regenerates after injury.
What nerves are included in the PNS?
SENSORY Nerves (afferent) MOTOR Nerves (efferent)
What is the somatic nervous system?
VOLUNTARY movement.
What is the autonomic nervous system?
INVOLUNTARY mechanisms
What two branches can the autonomic nervous system be split into? What are they?
- SYMPATHETIC NERVOUS SYSTEM- “Fight or flight”
* PARASYPATHETIC NERVOUS SYSTEM- Relaxation Response.
What nervous system regulates the gastrointestinal tract?
ENTERIC NERVOUS SYSTEM.
What functions does the cerebrum control?
Higher brain functions
What functions does the diencephalon?
Lower brain function
What are the 2 cerebral hemispheres joined by?
CORPUS CALLORUM
How many lobes are there in the brain? Name the lobes.
4 Partial Lobe Occipital Lobe Temporal Lobe Frontal Lobe
What does the spinal cord control?
Reflex actions.
What is gyrification?
process of FORMING characteristic FOLDS of the cerebral cortex which INCREASES the surface area of the cortex.
What is the matter called which covers the cerebrum?
NEURAL CORTEX
What is the cerebral cortex comprised?
RIDIGES (gyri)
Groves (sulci)
Large grooves (fissures)
Name 2 cortexes which make up the frontal lobe?
Pre- frontal Cortex.
Motor Cortex.
What is the Pre- Frontal Cortex responsible for?
- Higher level thought, decision-making planning & organising.
- Inhibiting impulses and actions.
- Personality.
What is the motor cortex responsible for?
- Processes & transmits information regarding body movement and position.
- Plans & co-ordinates fine movements via BASAL GANGLIA.
Where is the parietal lobe located?
Located behind the frontal lobe and above the temporal lobe.
In the parietal lobe what does it detect?
- Primary sensory cortex detects sensations, such as touch and pressure.
- Spatial orientation and information processing.
- Memory for numeracy and spelling.
Where is the temporal lobe located?
Below the frontal and parietal lobes.
What is the temporal lobe responsible for?
- Auditory (sound) processing
- Memory
- Dreams
- Language, understanding
Where is the Occipital Lobe located?
Behind the temporal Lobe.
What is the occipital lobe responsible for?
- Is the main vision centre of the brain.
* Visual information from the eyes is processed and interpreted.
What does the diencephalon include?
Thalamus
Hypothalamus
What is the function of the diencephalon?
- Responsible for integration of nervous and endocrine systems, through the hypothalamus and pituitary gland.
- FILTERS sensory information
- Involved in emotion, memory, and autonomic function.
The diencephalon is the structural link between what 2 elements of the brain?
CEREBRAL HEMISPHERES and brain stem.
What is the Hippocampus particularly important for?
Memory.
What does the cerebellum do?
Adjusts on-going movements by comparing arriving sensations with previously experienced sensations- relays to cerebrum.
What is the Basal Ganglia?
Cluster of structure involved in the regulation of movement.
What does the brain stem consist of? What is its functions?
Consists of the midbrain, pons, and medulla oblongata. Controls heart rate and breathing.
What is the differences between the sympathetic and parasympathetic nervous systems? (Sympathetic System)
Sympathetic system: Increased metabolic rate Increased heart rate and BP Heightened alertness Activation of sweat glands Activation of energy reserves Increased respiratory rate and dilation of bronchioles Reduced digestive and urinary functions.
What is the differences between the sympathetic and parasympathetic nervous systems? (Parasympathetic System)
Parasympathetic system:
Decreased metabolic rate
Decreased heart rate and BP
Increased secretion of salivary and digestive glands
Increased motility and blood flow in the digestive tract
Stimulation of urination and defaecation
