Module 3 Flashcards
What types of glial cells are in the CNS?
astrocytes, microglia, ependymal cells, oligodendrocytes
What times of glial cells are in the PNS?
Satellite cells and schwann cells
What functions do astrocytes provide the CNS?
- Structural support
- Regulate extracellular concentration of ions and neurotransmitters
- Formation of the
blood‐brain barrier
… and … form myelin sheaths around axons
Oligodendrocytes and Schwann cells
T or F
Resting membrane potential is negative in all cells
T
T or F
In all cells there are gradients of ions across the cell membrane
T
T or F
The inside of a cell’s membrane is positive relative to the outside
F
negative
How many sodium and potassium ions are outside the cell during resting membrane potential?
5mM K+
150mM Na+
How many sodium and potassium ions are inside the cell during resting membrane potential?
140mM K+
15mM Na+
The membrane at rest has many open … channels and few open … or … channels.
K+
Na+
Cl-
Na+/K+‐ATPase pumps … Na+ out and … K+ in
3
2
Buildup of ‐ve charge in a neuron is limited by the … gradient vs the … gradient of …
electrical
chemical
K+
The equilibrium potential in a neuron is approx …mV
‐70
T or F
Resting membrane potentials are dependent on voltage-gated ion channels
F
Voltage-gated ion channels are required for action potentials, not resting membrane potentials.
T or F
All cells have a membrane potential
T
… cells experience rapid changes in membrane potential
Excitable
T or F
Ionic gradients are not important in all cells
F
List some excitable cells
Neurons, myocytes and pancreatic beta cells
T or F
Even without an action potential, an axon has many ions moving across its membrane
T
Na+/K+ pumps get their energy from …
ATP
T or F
Na+/K+ pumps passively transport ions across the cell
F
actively
Na+/K+ pumps transport … ions out of the cell and … ions in
sodium
potassium
T or F
Some potassium channels are open all the time, allowing potassium ions to leave the cell
T
T or F
There are only a few constitutively open K+ channels in a cell membrane
F
There are many
T or F
There are only a few constitutively open Na+ channels in a cell membrane
T
T or F
K+ ions are of high concentration in a cell
T
Why do K+ ions have a tendency to diffuse from the inside of a cell to the outside?
Because there is a high concentration of K+ ions in a cell, creating a concentration gradient that moves K+ to the outside of a cell
Why is the chemical gradient of a cell membrane being reduced in a resting membrane potential?
Because potassium ions are moving from a high concentration inside the cell to a low concentration outside the cell.
Why does the electrical gradient of a cell membrane increase during resting membrane potential?
Because the inside of a cell at resting membrane potential is already negative so when K+ are moved out of the cell it becomes even more negative.
If the only channels open in a cell membrane were potassium channels, the value of the membrane potential would be…
EK = -90mV
If the only channels open in a cell membrane were sodium channels, the value of the resting membrane potential would be…
ENa = +65mV
What is the resting membrane potential of most cells?
-70mV
How many mM of Cl- are present in the inside and outside of a cell at resting membrane potential?
10mM of Cl- inside and 120mM of Cl- outside
What happens to a cell’s membrane potential during hyperpolarisation?
The inside of the cell membrane becomes more negative due to the opening of voltage-gated K+ channels and the subsequent movement of K+ out of the cell.
What happens to a cell’s membrane potential during depolarisation?
The inside of a cell membrane becomes more positive due to the opening of voltage-gated Na+ channels and the subsequent movement of Na+ into the cell.
… occurs when a stimulus lowers a cell’s membrane potential (mV) to lower than it is at resting membrane potential without a stimulus.
Hyperpolarisation
… occurs when a stimulus raises a cell’s membrane potential (mV) to higher than it is at resting membrane potential without a stimulus.
Depolarisation
T or F
Action potentials are all-or-nothing
T
T or F
The magnitude of an action potential is dependent on the strength of the original stimulus.
F
Because it is an all-or-nothing reaction it is independent.
T or F
Action potentials are fast (1-2 milliseconds) and have high frequencies
T
T or F
K+ channels transition from closed, open and inactivated stages.
F
Na+ channels do. K+ channels transition from open to closed.
What happens during the repolarisation of an action potential?
K+ channels open and K+ rush out
Na+ channels are inactivated and then start to close
What happens during the undershoot of an action potential?
Small hyperpolarisation
Also need Na+/K+-ATPase to restore Na+ and K+ concentrations.
What happens during the resting state of an action potential?
Voltage-gated ion channels are closed
What happens during the stimulus phase of an action potential?
A STIMULUS causes a few Na+ channels to open Na+ rushes in
What happens during the depolarisation phase of an action potential?
If THRESHOLD is reached:
Lots of Na+ channels open
Lots of Na+ rushes in
What happens during an absolute refractory period?
no AP can be generated
– Na+ channels open then inactivated
What happens during a relative refractory period?
AP only if apply large stimulus
– because some Na+ channels closed again
T or F
During the refractory period, the action potential can only fire in one direction
T
T or F
A refractory period limits firing frequency
T
How do local anesthetics work?
Local anaesthetics prevent action potentials by blocking voltage‐gated Na+ channels from transitioning from their inactivated to closed states, therefore, depolarisation cannot occur.
Conduction (Propagation) of action potentials usually starts at the neurons…
axon hillock
What factors affect action potential conduction speed?
Axon diameter, temperature and degree of myelination
T or F
The smaller the diameter, the less resistance –
FASTER conduction speed
F
larger
T or F
Any chemical reaction occurs faster at warmer temperatures!
T
T or F
Conduction speed is affected more by myelination than by axon diameter
T
T or F
Myelin insulates the axon membrane in invertebrates
F
vertebrates
T or F
Myelination causes the conduction speed to be slower but uses less energy
F
Myelination makes conduction speed faster
Are the nodes of Ranvier polarised or depolarised regions?
depolarised
Myelinated nerve fibers provide … conduction
saltatory
Unmyelinated nerve fibers provide … conduction
smooth
T or F
A single neuron can receive signals from many sending neurons
T
What causes vesicles to exocytate into the synaptic cleft?
The influx of Ca+ binding to vesicles in the presynaptic neuron
T or F
The vast majority of synapses are electrical
F
There are relatively few synapses of this type
T or F
Relatively few synapses are chemical
F
The vast majority of synapses are chemical
T or F
Tight junctions prevent fluid from crossing over a layer of cells
T
… is the mechanism of
neurotransmitter release from neurons
exocytosis
What does EPSP stand for?
excitatory postsynaptic potential
What does IPSP stand for?
inhibitory postsynaptic potential
Hyperpolarisation at a postsynaptic membrane happens if there is an … postsynaptic potential
Inhibitory
Depolarisation at a postsynaptic membrane happens if there is an … postsynaptic potential
excitatory
T or F
Most postsynaptic potentials decline before they reach the axon hillock
T
What is temporal summation?
When several EPSPs from the same synapse fire just after each other their combined stimuli can reach the action potential threshold.
What is spatial summation?
When two or more EPSPs from different synapses fire just after each other their combined stimuli can reach the action potential threshold.
T or F
Postsynaptic potentials are generated at the axon hillock
F
Action potentials are. Postsynaptic potentials are generated at the cell body or dendrites
Postsynaptic potentials can be either … or …
excitatory
inhibitory
T or F
Postsynaptic potentials are ungraded
F
They are graded
T or F
Postsynaptic potentials are local
T
What are the two types of chemical synaptic transmission?
Direct and indirect
… synaptic transmission involves a second messenger
indirect
What do neurotransmitters do in indirect synaptic transmission?
the neurotransmitter binds to a receptor on the postsynaptic membrane
What do neurotransmitters do in direct synaptic transmission?
neurotransmitter opens ion channels on the postsynaptic membrane
T or F
Both direct and indirect chemical synaptic transmission produces action via ligand-gated ion channels
F
Only direct transmission
Are GPCRs an example of direct or indirect chemical synaptic transmission?
indirect
What are some examples of direct chemical synaptic transmission receptors?
nicotinic receptors and glutamate receptors
When a neurotransmitter opens ion channels on the postsynaptic membrane this leads to a…
graded postsynaptic potential
The amino acid GABA is an example of a excitatory/inhibitory neurotransmitter
inhibitory
The amino acid glycine is an example of an excitatory/inhibitory neurotransmitter
inhibitory
The amino acid glutamate is an example of an excitatory/inhibitory neurotransmitter
excitatory
Indirect synaptic transmission can result in EPSPs or IPSPs depending on the … and …
neurotransmitter and the receptor type
Is 5-hydroxytryptamine (aka serotonin or 5-HT) a direct or indirect synaptic transmitter?
Indirect with the exception of 5-HT3 receptors
Is acetylcholine a direct or indirect synaptic transmitter?
Indirect on muscarinic receptors but direct on nicotinic receptors
Which one of the following is NOT an example of neurotransmitter removal from a synaptic cleft?
a) Neurotransmitters are taken up by astrocytes
b) Neurotransmitters are recycled by selective uptake via transporters
c) Neurotransmitters are broken down by enzymes
d) Neurotransmitters diffuse back into the presynaptic cleft
e) Neurotransmitters diffuse out of the synaptic cleft
d
T or F
Depolarisation makes a membrane potential less negative
T
T or F
All animals have a nervous system
F
Sponges don’t
Which of the following is not an example of how neurons can organise themselves:
a) neurons can form a nerve tent
b) neurons can form a nerve net
c) neurons can form a nerve ring with radial nerves
d) neurons can form nerve cords with transverse nerves
a
Segmentally arranged clusters of neurons are called…
ganglia
Ganglia are part of what nervous system?
the peripheral nervous system
T or F
Ganglia are not connected to the CNS
F
T or F
Mollusc NS organisation depends on lifestyle
T
The CNS consists of the … and …
brain
spinal cord
T or F
Spinal nerves are part of the CNS
F
They are part of the PNS
T or F
Most spinal and cranial nerves contain both sensory neurons and motor neurons
T
How many pairs of cranial nerves do mammals have?
12
How many pairs of spinal nerves do mammals have?
31
Ventral/anterior means front/back of body
Dorsal/posterior means front/back of body
front
back
The sympathetic/parasympathetic division of the autonomic nervous system is responsible for the fight or flight response
sypathetic
What are some things that happen during a fight or flight response?
Bronchi dilate
Heart beats faster
Glycogen to glucose
Adrenaline secretion
Digestion is inhibited
What sections of the forebrain are developed from the embryonic?
cerebrum and diencephalon
What is the function of cerebrospinal fluid?
Supply of nutrients and hormones; remove waste
Blocked flow in hydrocephalus
What is reticular formation?
Part of the brainstem that acts as a selectivity filter that determines arousal and sleep
The cerebellum is important for…
Motor function, coordination and cognitive and perceptual functions
What elements of the brain does the diencephalon contain?
The epithalamus, hypothalamus and the thalamus
Which part of the brain is the pineal gland in?
the epithalamus
the epithalamus connects the … system to the rest of the brain
limbic
The thalamus receives input from … and output from …
sensory neurons
motor neurons
What are the functions of the hypothalamus?
Homeostatic regulation ‐ hormones
Biological clock
Temperature regulation
Survival ‐ hunger, thirst…
The …. is responsible for communication between the left and right sides of the brain.
corpus callosum
When is Broca’s area in the brain activated?
During speech generation
When is Wernicke’s area in the brain activated?
when speech is heard
T or F
The hippocampus is responsible for long-term memory
F
short-term memory
The … is responsible for long term memory
cerebral cortex
T or F
A nerve consists of many neurons
T
What are glial vital for?
structural integrity and normal function
