Lectures 1, 2 and 3 Flashcards
Which ion is in high concentration in the cytoplasm of cells?
Potassium
What in the cell requires a high concentration of potassium?
Replication machineries (DNA, RNA, proteins)
What evidence is there against life starting in primordial oceans?
There was not much potassium in them and there is potassium in the cytoplasm of the cell (so how did the systems evolve?)
What are the two places theorised that life began on earth?
. Hydrothermal cents
. Terrestrial, anoxic, geothermal fields
What is the theory of how multicellular organisms evolved?
Protists (choanoflagellates-single cell) aggregate to form multicellular structures
Why do they think Metazoans evolved in the ocean which was rich in sodium?
Explains the presence of high concentrations of sodium in their extracellular fluid
The difference in ionic composition of the intracellular and extracellular fluids must be kept as constant as possible. What is the word for this?
Homeostasis
What can changes in extracellular osmolarity lead to?
Cell shrinkage or swelling
Where is the concentration of sodium and potassium high/ low?
. Na high outside the cell, low inside
. Vice versa
What does the difference in ionic composition of the intracellular and extracellular fluids generate?
Electrochemical gradient (stores energy)
If permeability for potassium ions increases what will happen to the membrane potential?
Will shift towards the equilibrium potential for potassium
If the permeability for potassium ions decreases, what will happen to the membrane potential?
Will shift towards the equilibrium potentials for the other ions
What is the function of dendrites?
Receive information from other neurons
What is the function of the cell body’s
Contains the nucleus and most cell organelles
What is the function of the axon?
Conducts Acton potentials away from the cell body
What are the axon terminals?
Synapse with a target cell
What happens to information collected by dendrites?
It is integrated in the axon hillock, which generates action potentials
What are the potentials that occur at the cell body called?
Graded potentials
What is a graded potential?
Is a change from the resting potential that is proportional to the magnitude of a stimulus
What is the purpose of graded potentials?
They are a means of integrating stimuli because the membrane can respond with proportional amounts of depolarisation or hyperpolarisation to each stimulus, and those changes in membrane potential are summed
What does whether a membrane depolarises or hyperpolarises depend on?
The ion concentrations inside and outside the neurons, the equilibrium potentials, and the repertoire of ion channels (what types of channels we have in each neuron)
Is permeability for sodium ions increases the membrane potential will shift towards the equilibrium potential for Na ions. What does this lead to?
Depolarisation
Is permeability for K ions increases, the membrane potential will shift towards the equilibrium potential for potassium ions. What does this lead to?
Hyperpolarisation
What do ion channels do?
Mediate facilitated diffusion of ions and other metabolites
How are ion channels opened/ closed?
By specific triggers: specific ligands, voltage conditions, or physical association with structural elements
Ion channel activity is the reason for what?
Electrical brain activity
What does it mean if the ion channels are closed?
Must be near the resting potential of the cell
What is the strength of a stimulus determined by?
The concentration of neurotransmitter
When does spatial summation occur?
When several excitatory postsynaptic potentials arrive at the axon hillock simultaneously
What does temporal summation mean?
Means that postsynaptic potentials creates at the same synapse in rapid succession can be summed
The membrane potential decreases exponentially with distance, so how can neurons send information over long distances?
The action potential (spikes)
Voltage gated sodium ion channels contain an activation gate and an inactivation gate. What is the function of the activation and inactivation gate?
. The activation gate: opens the channel and allows ions to pass through the pore
. The inactivation gate “plugs” the pore, preventing ions from passing through while the activation gate is open
Describe the absolute refractory period
No action potential will be generated, even if the membrane depolarises beyond the threshold. This is because the voltage-gated sodium ion channels are inactivated
Describe the relative refractory period
This is the period after hyperpolarisation. The membrane potential is lower (more negative) than usual and it requires more depolarising power to reach the threshold potential
Describe a graded potential
Vary in magnitude Vary in duration Decay with distance Occur in dendrites and cell body Caused by opening and closing of many kinds of ion channels
Describe action potentials
Always the same size and shape (in a given cell type)
Always the same station (in a given cell type)
Do not decay with distance
Occur in axons of neurons (also in muscle cells)
Caused by opening and closing of voltage-gates ion channels
What do graded potentials allow?
Integration of multiple input signals into action potentials
Describe glial cells
Surround neurons and provide support for and insulation between them. Glial cells are the mists abundant cell types in the central nervous system
What do Astrocytes do?
Maintain homeostasis
What is the function of Schwann cells?
Produce the myelin sheath, a greatly extended and modified plasma membrane wrapped around the plasma membrane wrapped around the axon in a spiral fashion
What do oligodendrocytes do?
Wrap around axons (insulation)
What are microglial cells similar to?
Macrophages
In long axons membrane depolarisation and action potential generations occurs where?
Occurs only in parts of the axon which are not insulated by the myelin sheath known as the nodes of ranvier
What are the nodes of ranvier?
Gaps in the myelin sheath (action potentials can jump from node to node). This is where you find voltage-gated sodium and potassium channels
What does myelination do?
Increases the speed of action potentials propagation in neurons (not all axons are myelinated)
What does an increase in the diameter of an axon do?
Effectively decreasss the internal resistance of current flow
Which is faster electrical or chemical synapses?
Electrical synapses are faster
What would happen if acetylcholinesterase was inhibited?
Synapses wouldn’t be able to switch off
Describe a neuron
Highly efficient cells which integrate and transmit information.
What do neurons and glial cells build?
Extremely complex neuronal networks
What equation is used to calculate the equilibrium for each ion?
Nernst equation
Define equilibrium potential
This is the potential a membrane would establish, solely. Based on the concentration gradient for one particular ion type. This is based on the assumption that the membrane is highly permeable for this ion type
What equation do you use to calculate membrane potential?
Goldman equation
Define membrane potential
The membrane potential of a cell is a sum of the equilibrium potentials for each ion inside and outside of the cell, as well as the membrane permeability for each ion. If the permeability for one ion is Hogg, the ion will reach its equilibrium and grande the equilibrium potential for this ion dominates the membrane potential. In most cells, this is the case for potassium ions because there are open potassium channels. In other words: the membrane potential will always shift towards the equilibrium potentials of the ions with the highest permeability
Define resting potential
In neurons, the basal membrane potential (without any graded potentials or action potentials) is called resting potential. This is to highlight the difference in the membrane potential in an unstimulated (i.e. resting) compared to a stimulated (graded/ action potential) state. (Please note that the membrane potential is called a resting potential only in those cells which can generate action potentials (neurons or muscled)
What do afferent neurons do?
Send information from the periphery to the central nervous system
What do efferent neurons do?
Send information from the central nervous system to the periphery
What is a nerve made up of?
Is a group of axons from many neurons
What are the names of the layers of connective tissue that surround the nerve?
Endoneurium, perineurium, epineurium
What does the left hemisphere of the brain control?
The right side of the body and speech
What does the right hemisphere of the brain control?
The left part of the body and perception of spatial relationships
What is the corpus callosum?
A bundle of axons which connects the two hemispheres
What is the gray matter in the brain?
Contains cell bodies, dendrites and axon terminals. This is where most synapses are located
What is the white matter?
Mainly consists of axons which connect different parts of the grey matter to each other
How many layers of neurons does the cortex contain?
Usually 6
What is the function of the cerebral cortex?
Receives sensory information (perception), integrates information and controls voluntary movement
It is discussed that the cortex is organised in functional vertical units called what?
Columns (different bundles of neurons)
What does layer 1 of the cerebral cortex contain?
Only a few cell bodies and connections
What do layers 2 and 3 of the cerebral cortex do?
Integrate signals within the cortex, the other layers communicate with other parts of the brain
What are the names of the loves the cerebrum can be divided into?
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
What does the primary motor cortex control?
Muscles involved in speech (voluntary movement)
What are the language areas of the cortex?
Multiple regions of the left cerebral cortex participate in the processes of repeating a word that is heard, and speaking a written word
What was the name of the railroad worker that had a railway spike go through his head that changed his personality and made him impulsive and make bad decisions?
Phineas Gage
What is the frontal lobe of the cerebrum mainly responsible for?
Personality and decision making
What are the thalamus and basal nuclei regions of the brain involved in?
The coordination of movement
What are disturbances in the neuronal communication within the basal nuclei system associated with?
Impaired control of movement (Parkinson’s disease)
What does the cerebellum receive sensory and motoric input from?
The periphery of the body and the organ of equilibrium (inner ear).
It receives motoric input from the cerebrum
What does the cerebellum do?
It integrates the input information it receives and coordinates movement. It is also involved in learning and memory
What does the cerebellum receive sensory and motoric input from?
The periphery of the body and the organ of equilibrium (inner ear).
It receives motoric input from the cerebrum
What does the cerebellum do?
It integrates the input information it receives and coordinates movement. It is also involved in learning and memory
The thalamus is a rely station which integrates what?
Sensory and motoric information
The thalamus receives information from which senses?
All except smell
What does the thalamus do?
Filters ‘unnecessary’ information and only relays ‘important’ information to the cortex
What is the amygdala involved in?
Emotional responses, especially aggression and fear
What is the hippocampus involved in?
Learning and memory- it converts short-term to long-term memory
What is the olfactory bulb responsible for? What is it connected to and what does this mean for humans?
It is responsible for the sense of smell. It is connected to the Amygdala and the hippocampus. Therefore odours provoke strong emotions and memories in humans
What does the hypothalamus control?
Internal organs and the endocrine (hormonal) system in order to maintain homeostasis (electrolyte and fluid balance, hunger and thirst).
E.g. controls sodium ions etc. When too much salt is in the system
What does the pituitary gland do?
Secretes hormones
What is the pineal gland involved in?
Establishing circadian rhythms and secretes the hormone melatonin
What is the function of the brain stem?
Connects the brain to the spinal cord and mainly controls involuntary functions
What are the names of the 3 regions of the brain stem?
The midbrain
Pons
Medulla oblongata
What does the midbrain control?
Eye movement
What is the function of pons?
Is a bridge between the cerebrum and the cerebellum. It also controls breathing
What does the medulla oblongata control?
Controls involuntary functions (breathing, cardiovascular control e.g. blood pressure)
What are ventricles filled with?
Cerebrospinal fluid (which continues throughout the spinal cord)
What does cerebrospinal fluid do?
Protects the brain from injury and reduces its weight
Where is the cerebrospinal fluid secretes from?
An epithelium- the choroid plexus (500ml per day)
What is the fluid flow of the glymphatic system fuelled by?
The arterial pulse
How does sleeping positions affect the efficiency act of the glymphatic system ‘cleaning ‘ the brain?
When you sleep on your right side, your heart is in a slightly elevated position, thus pumping more efficiently towards the brain
