Prof Study Guide Flashcards
1
Q
plasma membrane
A
phospholipid bilayer + all the associated proteins and other molecules. Many of these are transmembrane proteins
2
Q
what does the plasma membrane and its components collectively do?
A
confer selective permeability to ions, glucose and other molecules
3
Q
nucleus
A
hosts the genome and is the site of transcription which produces mRNAs that
are exported.
4
Q
ribosomes
A
sites of protein synthesis (translation)
found studded on ER or FREE IN CYTOPLASM
5
Q
how is a vesicle-based system (budding and fusion) used by the ER/Golgi complex
A
used to sort new
proteins to either the PM, the outside of the cell (soluble proteins released by exocytosis) or
lysosomes. ONLY THESE THREE
6
Q
where to the cytoplasm and other organelles get their proteins from
A
from free ribosomes
(mitochondria make a few proteins from their own mini-genome and
transcription/translation apparatus).
7
Q
how do mitochondria produce ATP
A
from glucose or fatty acids (it can use amino acids in a pinch)
8
Q
lysosomes digest debris by…
A
fusing with intracellular vesicles often derived from endocytosis
9
Q
peroxisomes
A
DETOXIFY free radicals
10
Q
cytoplasm
A
consists of the semi-liquid cytosol, an aqueous compartment in which intermediate metabolism occurs, the organelles and the cytoskeleton
11
Q
microtubules
A
dynamic polymers of tubulin
12
Q
microtubules form…
A
highways for movement of transport vesicles via kinesin and dynein motor proteins, and cilia and flagella for generating movements.
13
Q
microfilaments
A
dynamic polymers of actin. In association with myosin, a motor protein,
they produce cellular contraction e.g. muscle fibers
14
Q
intermediate filaments
A
longer proteins produced by an array of different genes
15
Q
why have specialized/different types of cells?
A
complex multicellular life, like humans, require cells SPECIALIZED FOR DIFFERENT TASKS
16
Q
PROXimate cause of different cell types
A
differential gene expression
all cell types contain the
same DNA, but express unique subsets of ~10K genes for any given cell type (out of ~22K in
the genome).
17
Q
tissue
A
aggregate of cells and extracellular material
-muscle (contraction)
-nervous (signals; electrical and chemical)
-connective (structural support)
-epithelial (exchange)
17
Q
organ system
A
An organ system is a group of organs that work together to perform complex functions and maintain HOMEOSTASIS in an organism
18
Q
organ
A
two or more primary tissues organized to perform a function
- heart, lungs, liver
19
Q
homeostasis
A
maintain a stable internal environment despite changes in external conditions. This stability is crucial for the proper functioning of biological systems and is essential for survival
20
Q
synaptic; extracellular chemical messaging
A
A chemical messenger is released very locally @ a synapse (there’s a very small gap)
Detected by only one part of one cell
20
Q
hormonal; extracellular chemical messenger
A
Secreting cell going to release chemical messenger into bloodstream
Now it is exposed to virtually all cells in the body, but it only activates a subset of cells; the ones that express the cognate receptor for that signal
21
Q
paracrine; extracellular chemical messaging
A
Chemical messenger released into local tissue environment & exposed via diffusion in the extracellular space or fluid to 10s-100s neurons in local neighborhood
22
Q
nuclear receptors
A
(intracellular) that activate gene expression
Many receptors can be found pre bound to DNA @ nucleus; hormones slip through PM and get in to bind receptors that’ll activate patterns of gene expression
Initiate a new wave of transcription
Relatively slow
23
GPCRs
(‘metabotropic’ or ‘2nd messenger’ signaling)
Chemical messengers bind to cell surface receptors
Activates G protein cascade that leads to sequence of phosphorylation events that alter the protein shape and function of pre-existing proteins and get cellular response
24
enzyme-linked receptors
cell surface proteins that, upon ligand binding, activate intrinsic enzymatic activity or recruit enzymes, triggering intracellular signaling cascades.
induces conformational changes
25
ionotropic receptors
(cell surface) which themselves are ion channels
Neurotransmitter binds receptor; it opens the ion channel and allows ions to flow down their electrochemical gradient
Can bring about a response immediately/in milliseconds
26
what does the brain do with sensory signals
processes them and produces motor output
27
perception
what you can report
28
brain relies on
neurons specialized for chemical and electrical signaling
The 86 billion neurons in the human brain and
interconnected by 100+ trillion synapses where a chemical neurotransmitter is released by
one neuron and detected by another
29
ion movement across the plasma membrane is BASIS of...
electrical signaling in neurons
30
two types of transmembrane proteins for ion/molecule movement:
carriers and
channels
31
Carriers have binding site for the molecule to be transported:
(1) Facilitated diffusion uses a fixed affinity site and transports down the concentration gradient. (2) Pumps have variable
affinity sites and transport uphill, AGAINST the concentration gradient
32
Na+/K+ ATPase pump
transports 3 Na out and 2 K in with each turn of the cycle.
Its role is to establish and maintain concentration gradients.
33
ion channels
do not have binding sites
have pores which allow for diffusion-like permeation
34
chemical driving
diffusion down a concentration gradient
35
electrical driving force
results from electrostatic
interactions at a distance.
36
net driving force
vector sum of each driving force (w direction and magnitude)
37
membrane potential results from
CHARGE separation across the membrane
polarity is referenced inside relative to outside e.g. at rest there is an excess of negative charges on the inside and excess of positive charges on the outside, for a resting potential of -70 mV
38
why do Na and K concentration gradients no run down during normal operation
amount of charge separation underlying biologically meaningful electrical signaling is extremely small compared to the total number of ions in bulk solution on both sides of the membrane
39
IONS DO HAVE
equilibrium potential
40
equilibrium potential
defined as the membrane potential at which there is no net charge movement for that ion.
41
RMP
depends on all the permeant ion
species weighted by their relative permeabilities.
At rest, K permeability dominates as there
are more K leak channels than Na leak channels
42
transient injection of current
leads to passive dissipation of current regardless of the
current source. This passive dissipation causes a graded potential, which always decreases in size as it flows away from the current source. Graded potentials are self-limited in time and space.
43
action potentials
all or none
electrical signals initiated AT THE AXON HILLOCK which rapidly propagate to the axon terminals (as far as 1 meter) where they trigger transmitter release
BRAIN IS SYNAPTIC NETWORK
44
what do action potentials depend on
VOLTAGE-GATED Na+ and K+ channels
45
net driving force on Na at AP onset
strong; but weak at AP peak
it begins when all Na channels have opened (occurs just after threshold is reached) and ends when
Na inactivation is removed
46
relative refractory period
a few ms in duration, during which the neuron can fire another AP but would require a larger than usual triggering event
begins when Na inactivation is removed and ends when the resting potential is restored following the K channel deactivation
47
speed and reliability of action potential propagation depends on
axonal diameter, membrane resistance, internal resistance and the presence or absence of myelin
48
contiguous conduction
relies on a continuous distribution of v-gated Na and v-gated K channels along the length of the axonal membrane.
One metaphor is the stadium wave.
This is an active process in the sense that it is not self-limited in time and space.
49
Saltatory conduction relies on
myelin (insulator) and clusters of v-gated Na and v-gated K channels found at the Nodes of Ranvier. This is an active process at the sites of initiation (axon hillock) and nodes of Ranvier, and a passive process (graded potential) underneath the myelinated stretches of axon.
50
How far current will flow down the axon before leaking out depends on
relative values
of membrane resistance (sometimes referred to as transverse path) and internal resistance
(the axial path).
51
internal resistance in giant axons
low; which favors AP propagation
Myelin increases membrane resistance such that the axial path is now
the lower resistance path.
51
myelin decreases
capacitance and therefore lowers the time constant which results in the membrane potential changing faster in response to current injection: it SPEEDS UP AP propagation.
52
Na channel inactivation ensures...
unidirectional spread of naturally occurring AP, and the annihilation of APs experimentally induced at either end of an axon when they collide.
53
Demyelinating diseases result in
slow and unreliable AP propagation. The autoimmune disease multiple sclerosis commonly affects the cerebellum, a brain structure which plays
an important role in calibrating ongoing movements. The symptoms = ‘action tremors’
54
intrinsic
LOCAL control systems built into an organ
Organ itself has a solution for its own problem
E.g. increased CO2 production leads to relaxation of smooth muscle and dilation of blood vessels
Increase the blood flow through the organ and it will be able to clear CO2 faster
55
extrinsic
External control system outside of an organ permitting coordinated regulation of several organs
56
negative feedback
change in controlled variable triggers response that opposes the change
57
sensor
mechanism to detect the controlled variable
58
integrator
compares the sensor's input
says "we're good" and turns off
59
set point
desired value of the variable
60
effector
adjusts the value of the controlled variable
61
paracrine secretion spatial range
neighboring cells (10s-100s microns)
62
Hormonal Secretion spatial range
body wide
63
synaptic secretion spatial range
one part of one cell (~1 micron)
64
Electrical synapse
Direct connection between 2 neurons
VERY FAST
Electrical signal passes directly from 1 to the other though GAP JUNCTIONS
65
Neuron
WHOLE CELL that sends and receives messages
66
Synapse
Junctions between 2 neurons
67
Chemical synapse
RESTRICTED SPATIAL RANGE (1 part of 1cell)
68
What causes the neurotransmitters to be released by exocytosis?
Ca2+ enters the synaptic knob
Floods pool of docked synaptic vesicles that triggers release
See Ca2+ in HIGH concentration
69
How does a PSP come about and what does it mean (chemical synapse) ??
Binding to receptors allows voltage-gated ion channels to open & allow current to flow= GRADED POTENTIAL
…means that there is a change in voltage across membrane and it could vary in magnitude (IPSP/EPSP)
70
Inhibitory Postsynaptic Potential (IPSP)
HYPERPOLARIZING event, bring Vm AWAY from threshold
Make LESS likely to fire action potential
Allow (-) ions in like chloride
MAKE INSIDE MORE (-)
71
Excitatory Postsynaptic Potential (EPSP)
DEPOLARIZING; bring Vm closer to threshold for firing AP
Binding opens ion channels; allow (+) like Na+ INTO neuron
Move closer to threshold
72
Ionotropic receptors
Fast synapses & ligand-gated ion channels
Neurotransmitter binds causes immediate conformational change (ion channel opens)
RAPID change
73
Metabotropic receptors
Slow synapses and receptors coupled to G proteins
74
Transmitter removal
Duration of neurotransmitter action is limited to
- diffusion out of synaptic cleft (diffusion results in dilution; signaling terminated)
- degradation by extracellular enzymes
-reuptake into presynaptic terminal by transporter proteins
75
Neuronal integration- convergence
Synaptic input of many neurons on to ONE neuron
76
Temporal summation
EPSPs happen close enough in time, so they can add up; allows SINGLE synapse to effectively transmit stronger signals based on frequency of incoming action potential
77
Spatial summation
On same dendrite, EPSPs from different inputs (Ext 1& Ext 2 both on R1)
Integrate signals from multiple sources
78
EPSP-IPSP Cancellation
An Excitatory and inhibitory synapse occur on one recording site and they cancel out
79
Components of CNS
Brain, spinal cord, retina
Processing of sensory info, initiating motor commands, higher cognitive function
80
Afferent division
Sensory stimuli and visceral stimuli inputs
81
Output of CNS
Efferent division; transmit MOTOR commands from CNS to rest of body
82
Somatic nervous system
Controls VOLUNTARY movements (walking or waving hand)
It relays sensory information, such as touch, pain, temperature, and proprioception, enabling the body to respond to environmental stimuli
83
Autonomic nervous system
division of the peripheral nervous system that regulates involuntary physiological functions. It controls processes that occur automatically, without conscious effort, such as heart rate, digestion, and respiratory rate
84
Synapses
Connections between a neuron and a target cell that allow for communication
85
electrical coupling/electrical synapse
Proteinaceous tunnels built from connexin proteins allow passive current flow from one cytosol to the next. These tunnels are much larger than ion channel pores. Cardiac cells are electrically coupled to form a syncytium. The mature brain, in contrast, relies mostly on chemical synapses
86
excitation-secretion coupling
neurotransmitter release via Ca-dependent exocytosis
87
transmitter receptors can be
ionotropic (receptor is the channel) or metabotropic (receptor activates G protein cascade which acts on a separate ion channel)
88
most common ionotropic glutamate receptor
allows both Na and K to permeate. The
dominant charge carrier is Na due to its larger net driving force in and around resting
potential. The results in depolarization. The reversal potential is ~ 0 mV which is well above
threshold for firing a spike, therefore the effect is EXCITATORY.
89
Ions have_____. Channels have______. At those values, there is__________________.
equilibrium potentials, reversal potentials, no NET CURRENT FLOW.
90
More common ionotropic receptor
GABA
91
what is GABA permeable to
Cl; reversal potential is -70, which is below threshold for firing a spike, therefore the effect is inhibitory. Many metabotropic receptors activate K channels. The reversal potential is -90, which is below threshold for firing a spike, therefore the effect is INHIBITORY
92
Postsynaptic neurons in the brain tend to experience...
intermittent bombardment of 10s-
100s of synaptic potentials which are individually small. These PSPs add (or subtract) from
one another when they occur close together in time and space - conditions needed for
spatiotemporal summation
93
afferent
ascending towards the brain
94
efferent
descending away from the brain
95
At level of spinal cord, afferent sensory input goes through...
dorsal root ganglion
96
efferent motor output goes through
VENTRAL roots
97
what is bilaterally symmetric
spinal cord (and brain)
98
functional localization
specific areas of the brain are associated with particular functions or processes. Different regions of the brain are specialized for different tasks, such as language, movement, memory. and sensory perception
primary motor cortex
primary auditory cortex
somatosensory cortex
primary visual cortex
99
topographic map
spatial representation of how specific functions or sensory inputs are organized across different regions. certain areas of the brain correspond to particular parts of the body. ORDERLY MAPPING
more sensitive areas, like the hands and face, have larger representations (overrepresentation in sensory homunculus)
100
are chemical messengers inherently excitatory or inhibitory?
DEPENDS ON RECEPTOR IDENTITY
101
nicotinic ACh receptors
generally EXCITATORY; opening of ion channels, primarily Na+ into cell... LEADS to depolarization
102
muscarinic ACh receptors
work through G proteins and second messenger systems.
hyperpolarization (when K+ channels open) leads to INHIBITION (slow heart rate)
depolarization (when K+ channels close) leads to EXCITATION ( smooth muscles contract)
103
Receptor cells (photoreceptors, hair cells, somatosensory receptors) are specialized to
transduce a particular form on environmental energy (‘modality’; light, sound, touch) into a
change in membrane potential
104
receptor potential
change in membrane potential of sensory receptor cell when it is stimulated by an external stimulus
105
receptors are grouped together in...
sheets to form a sensory surface, sometimes referred to as a sensory epithelium
106
receptor potentials cause action potentials to
be generated in the receptor cell (receptor potential reaches certain threshold) or its
downstream target. The rate and timing of action potentials carry information about the
stimulus to the brain
107
thalamus
obligatory relay of visual, auditory and somatosensory information to
primary cerebral cortices, defined as the anatomical targets of the thalamic subdivisions
108
primary cerebral cortex projects to what
higher cerebral cortex
109
receptive field of a neuron
where on body you can touch to activate neuron
110
lateral inhibition
sharpens receptive fields via side channel
suppression
111
high acuity
high density of receptors with small spatial receptive fields
112
acuity
ability to discriminate two similar but not identical sensory stimuli. It depends
on receptor density and receptive field size
113
pupil size
gates the amount of light coming into the eye
114
lens
behind iris and pupil; fine tunes the focus of light rays; allows sharp images to be formed on retina
115
fovea
region of highest acuity; packed with cones; provide high visual acuity and color vision
116
cones
3 types (red, green, blue); small receptive fields/high acuity; require brighter light to function, outer segment still has discs
117
rods
low light/night vision (scotopic); can detect single photons, DO NOT distinguish between different wavelengths, serve LOW ACUITY and PERIPHERAL field vision
118
BOTH rods and cones, light is absorbed by photopigments which activate a G protein
cascade that enzymatically cleaves cGMP : IN DARK
cGMP had been holding open a
Na channel which had depolarized the cell leading to transmitter release.
a continuos release of neurotransmitter has INHIBITORY effect on next cell; signal is SUPPRESSED- see DARK
119
cGMP in LIGHT
transmitter release stops and the circuit is disinhibited (the downstream cell is
intrinsically active). That causes retinal ganglion cells to fire spikes. RGC axons gather
together and leave the retina at the optic disc
120
medial axons DO
cross the midline
121
optic nerve
122
optic chiasm
123
optic tract
124
sound
a wave with alternating cycles of compression and rarefication of particles in a medium (e.g. air or water)
reflected by your pinna into the ear canal
and causes the tympanic membrane to vibrate
125
KEY point ab basilar membrane
gradient in the physical property of basilar membrane is what determines frequency discrimination
diff loc w diff frequency of sound
126
vibrations are
conducted via the mechanically efficient ossicles to the oval window which causes fluid movement within the cochlea.
causes the basilar membrane to move up and down
127
location where high frequencies best resonate
narrow, stiff end near the OVAL WINDOW
128
location where low frequencies best resonate
broad, compliant end near the HELICOTREMA
129
where are the hair cells
in the ENTIRE LENGTH of the basilar membrane
130
where are the tips of the apical stereocilia embedded
embedded in the TECTORIAL membrane
131
are the tectorial and basal membrane ontop of eachother
pivot points are OFFSET; creates a
shearing force that bends the stereocilia forward and backward with each sound cycle
132
stereocilia membrane ion channels
mechanically gated, open with each cycle of
sound and depolarize the hair cell (yes, with K!). This is a receptor potential. It causes
transmitter release from the hair cells to the primary afferent fibers which head towards
the brain.
133
what happens once mechanically gated ion channels open due to movement in the ear
K+ depolarizes and causes activation of transmitter release
134
pacinian corpuscles
have mechanically gated ions that respond to membrane deformation and open; depolarizes the cell which triggers spikes that propagate towards the spinal cord
135
phasic signaling
encapsulated sensory neuron that is rapidly adapting; response to SUSTAINED stimulus; brief on and off response
DUE to slow mechanical separation of the overlying connective layers
136
tonic signaling
non-encapsulated receptor types exhibit sustained RESPONSE to sustained STIMULUS
137
how many times does somatosensory info cross the MIDLINE on journey to cortex
EXACTLY ONCE; find topographic maps of the sensory surface (‘sensory homunculus’)
138
motor neurons exit the spinal cord via the
ventral root ganglion and synapse onto skeletal
muscle; final common pathway for both voluntary and involuntary movement.
139
are neuron-muscle synapses and neuron-neuron synapses
very similar
140
neuromuscular junction
motor neurons project out of the ventral root and make contact with muscles here; also called motor end plate
141
EPSP in motor system
typically large enough to cause spikes in the postsynaptic cell (muscle), and transmission is rapidly terminated with assist from acetylcholinesterase, an extracellular facing enzyme that breaks down the transmitter, Ach
142
myasthenia gravis
autoimmune attack on Ach receptors cause muscle weakness
alleviate: systemic administration of neostigmine which blocks acetylcholinesterase and therefore prolongs the dwell of Ach in the synaptic cleft,
increasing total activation of the spared Ach receptors
