Exam 1 Flashcards
Physiology is the study of
functions of living things
Physiology has two approaches, one with an emphasis on ______ and one with an emphasis on ______
on purpose of body process (Why?)
• Explanations are in terms of meeting a bodily need
on mechanism (How?) • Explanations are in terms of cause and effect sequences
Physiology is the brother of
Anatomy
o Structure-Function relationships of the body include:
- Heart receiving and pumping blood
- Teeth tearing and grinding food
- Bones protect vital organs
- Vessels carrying blood
Levels of organization
Chemical •Molecules composed of atoms Cellular •Cells are basic units of life Tissue (group of cells) Organ (one or more tissues make up an organ) Body system (one or more organs make up a body system) Organism
What are the seven basic cell functions?
o Obtain nutrients and oxygen from surrounding environment (Things that do not have nutritional value are things that would not keep you alive on a desert island)
o Perform chemical reactions that provide energy for the cell
o Eliminate carbon dioxide and other wastes to surrounding environment
o Synthesize needed cellular components
oRegulate exchange of materials between cell and its surrounding environment
o Sensing and responding to changes in surrounding environment
o Reproduction
-Exception Nerve cells and muscle cells lose their ability to reproduce early in development
What are the 4 primary types of tissue?
- Muscle tissue
- Nervous tissue
- Epithelial tissue
- Connective tissue
What are the 3 types of muscle tissue and their function?
Skeletal muscle • Moves the skeleton Cardiac muscle • Pumps blood out of the heart Smooth muscle • Encloses and controls movement of contents through organs
Muscle tissue is specialized for ______ and facilitates ______
contracting
movement
Nervous tissue consists of cells specialized for _________
initiating and transmitting electrical impulses
Nervous tissue is found in _______(3 places)
brain, spinal cord, and nerve cells
Epithelial tissue consists of cells specialized for _______
exchanging materials between the cell and its environment
Epithelial tissue connects the body and its organs to ________
the environment
Epithelial tissue is organized into two general types of structures:
- Epithelial sheets
* Secretory glands
the purpose of connective tissue?
Connects, supports, and anchors various body parts
connective tissue is distinguished by having _________
relatively few cells dispersed within an abundance of extracellular materials
three examples of connective tissue:
- Tendons- attach skeletal muscle to bones
- Bone- supports and protects the body
- Blood- transports bodily materials
organs generally consist of what?
two or more types of tissues that work together to perform a particular function
The stomach consists of four different tissue types. Name them and their function as part of the stomach
- Inside of stomach lined with epithelial tissue
- Wall of stomach contains smooth muscle
- Nervous tissue in stomach controls muscle contraction and gland secretion
- Connective tissue binds all the above tissues together
Body Systems-
Groups of organs that perform related functions and interact to accomplish a common activity essential to survival of the whole body
Name the 11 systems of the human body
- Circulatory System
- Digestive System
- Respiratory System
- Urinary System
- Skeletal System
- Muscular System
- Integumentary System (hair, skin, nails)
- Immune System
- Nervous System
- Endocrine System
- Reproductive System
Homeostasis is the ability to maintain a _________, NOT a ____________
relatively stable internal environment
constant internal environment
_________ is essential for survival and function of all cells
homeostasis
Each cell contributes to maintenance of a relatively stable internal environment to maintain ________
homeostasis
Body cells are contained in a ________ through which life-sustaining exchanges are made
watery internal environment
Extracellular fluid (ECF)-
Fluid environment in which the cells live (fluid outside the cells)
The two components of ECF-
plasma
interstitial fluid
Intracellular fluid ICF
Fluid contained within all body cells
the seven factors homeostatically regulated are:
- Concentration of nutrient molecules
- Concentration of O2 and CO2
- Concentration of waste products
- pH
- Concentration of water, salt, and other electrolytes
- Volume and pressure
- Temperature
The circulatory system contributes to homeostasis by?
Carries materials from one part of the body to another
The digestive system contributes to homeostasis by? (3 things)
- Breaks down dietary food into smaller molecules that can be distributed to body cells
- Transfers water and electrolytes from external environment to internal environment
- Eliminates undigested food residues to external environment in the feces
The respiratory system contributes to homeostasis by? (2 things)
- Gets O2 from and eliminates CO2 to the external environment
- Important in maintenance of proper pH of internal environment
The urinary system contributes to homeostasis by?
• Removes excess water, salt, acid, and other electrolytes from plasma and eliminates them in urine.
Gout-
- accumulation of uric acid in the blood. Causes severe joint pain
If you are severely dehydrated, drink ____ because ______
gatorade
it makes you drink more
How does the skeletal system work to maintain homeostasis? (4 things)
- Provides support and protection for soft tissues and organs
- Serves as storage reservoir for calcium
- Along with muscular system enables movement of body and its parts
- Bone marrow is ultimate source of all blood cells
How does the muscular system work to maintain homeostasis?
moves the bones
How does the integumentary system work to maintain homeostasis? (2 things)
- Serves as outer protective barrier
* Important in regulating body temperature
How does the immune system work to maintain homeostasis? (2 things)
- Defends against foreign invaders and against body cells that have become cancerous
- Paves way for repairing or replacing damaged or worn-out cells
How does the nervous system work to maintain homeostasis? (2 things)
- Controls and coordinates bodily activities that require rapid responses-reflexes.
- Detects and initiates reactions to changes in external environment
How does the endocrine system work to maintain homeostasis? (2 things)
- All hormone-secreting glands. Regulate numerous cellular activities
- Especially important for controlling concentration of nutrients and, by adjusting kidney function, controls internal environment’s volume and electrolyte composition
How does the reproductive system work to maintain homeostasis? (tricky, 2 things)
- Not essential for homeostasis (not essential for survival of individual)
- Is essential for perpetuating the species
Leukemia-
cancer of the bone marrow. Abnormal accumulation of white blood cells. Lack of platelets. Blood clotting is affected
Glucagon and insulin. Which is more essential and why?
• Glucagon is more essential than insulin. It has 11 genes that do the same thing as it does. You cannot survive if your brain doesn’t have sugar.
In order to maintain homeostasis, homeostatic control systems must be able to: (3 things)
- Detect deviations from normal in the internal environment that need to be held within narrow limits
- Integrate this information with other relevant information
- Make appropriate adjustments in order to restore factor to its desired value
disruptions to homeostasis can lead to
illness and death
Pathophysiology-
Abnormal functioning of the body associated with disease
Name three important roles of the plasma membrane:
o Controls movement of molecules between the cell and its environment
o Participates in joining cells to form tissues and organs
o Plays important role in the ability of a cell to respond to changes in the extracellular environment
The most abundant lipids of the plasma membrane are _______
phospholipids
Amphipathic-
having both a polar and nonpolar portion
carbohydrates are located on which side of cell membrane?
outer surface (extracellular) only
where is cholesterol located in the cell membrane and what does it contribute to?
- Tucked between phospholipid molecules
* Contributes to fluidity and stability of cell membrane
Name five functions of membrane proteins:
- Span membrane to form water-filled pathways, or channels across lipid bilayer
- Serve as carrier molecules
- Membrane-bound enzymes
- Receptor sites
- Cell adhesion molecules (CAMs)
- Proteins on surface are important in cell-to-cell interaction/ recognition
which part of the phospholipid bilayer prevents solutes from crossing?
the hydrophobic interior
Membrane carbohydrates serve as _____
self-identity markers which enable cells to identify and interact with one another
Different carbohydrate concentrations on the membrane can be found in different _____
cell types
Name the 3 means by which cells are held together:
- extracellular matrix
- Cell adhesion molecules in cells’ plasma membranes
- Specialized cell junctions
extracellular matrix seves as biological “_____”
glue
three major types of protein fibers interwoven in extracellular matrix:
collagen, elastin, fibronectin
Collagen-
protein that forms flexible fibers or sheets
Scurvy-
vitamin C deficiency. Causes collagen fibers to be damaged. Results in bleeding in skin and mucous membranes.
Elastin-
Rubbery protein fiber. Abundant in lung tissue. Promotes flexibility.
Fibronectin-
Promotes cell adhesion. Holds cells in position. Reduced production in cancer cells that break free and metastasize
What two properties of particles influence whether they can cross cell membrane without assistance?
- Relative solubility of particle in lipid
* Size of the particle
un-assisted membrane transport is called:
diffusion or osmosis
The four assisted membrane transports are:
- Carrier-mediated transport
- Facilitated transport
- Active transport
- Vesicular transport
Diffusion-
uniform spreading out of molecules due to their random intermingling
The tonicity of the extracellular solution determines what about a cell?
whether it will swell, shrink, or remain the same
Which assisted membrane transport requires that the carrier undergo a conformational change?
carrier-mediated transport
Carrier-mediated transport can be active or passive, depending on ______
concentration gradients
Characteristics that determine the kind and amount of material that can be transferred across the membrane via carrier-mediated transport:
- Specificity
- Saturation
- Competition
Facilitated diffusion is an assisted membrane transport that falls under the sub-category of ______ transport.
carrier-mediated
Active transport is also in the sub-category of _____ transport just like facilitated diffusion, with the key differences being that active transport moves molecules ________ their concentration gradient
carrier-mediated
against
primary active transport requires _____, while secondary active transport is driven by _____
- ATP
- An ion concentration gradient established by a primary active transport system
Vesicular transport-
Material is moved into or out of the cell wrapped in membrane
Pinocytosis-
“cell drinking” nonselective uptake of extracellular fluid droplets
Phagocytosis-
-“cell-eating” selective uptake of solid particles
Exocytosis-
Provides mechanism for secreting large molecules
Most depression medications, such a Prozac, are SSRI’s, which stands for
Selective Serotonin Re-Uptake Inhibitors
• Serotonin is a neurotransmitter in the _______ nervous system. Produces a feeling of __________
central
pleasure, euphoria, and general well-being.
Many people who suffer from depression are deficient in ________
Serotonin
How do SSRI’s treat depression?
SSRI’s block Endocytosis, so instead of serotonin binding the receptor and being taken into neuron B, it is allowed to keep binding the serotonin receptor, producing a constant feeling of well-being.
Membrane potentials are in reference to the inside/outside of a cell?
inside
Resting membrane potential-
Constant membrane potential present in cells of non-excitable tissues and those of excitable tissues when they are at rest
The _________ is the most important active transport system, and helps contribute to the ____________
Na+/ K+ ATPase
resting membrane potential of some cells
How the Na+/ K+ ATPase works:
It binds ______ from the cytosol, then undergoes a conformational change after being phosporylated by ATP. Following the conformational change, __________ Dephosphorylation returns the transporter to original conformation, and ________
- 3 Na+
- 3 Na+ are released to extracellular and 2 K+ are picked up
- K+ is released to cytosol
Effect of sodium-potassium pump on membrane potential makes a small/large contribution to membrane potential?
small
The biggest influence on resting membrane potential is _________
the relative permeability, or “leakiness” of ion channels.
Why does K+ desire an equilibrium potential of -90?
- The concentration gradient for K+ tends to move this ion out of the cell.
- The outside of the cell becomes more positive as K+ ions move to the outside down their concentration gradient.
- The membrane is impermeable to the large intracellular protein anion (A-). The inside of the cell becomes more negative as K+ ions move out, leaving behind A-..
- The resulting electrical gradient tends to move K+ into the cell
- No further net movement of K+ occurs when the inward electrical gradient exactly counterbalances the outward concentration gradient. The membrane potential at this equilibrium point is the equilibrium potential for K+ (EK+ ) at -90 mV.
Why does Na+ desire an equilibrium potential of +60?
- The concentration gradient for Na+ tends to move this ion into the cell
- The inside of the cell becomes more positive as Na+ ions move to the inside down their concentration gradient
- The outside becomes more negative as Na+ ions move in, leaving behind in the ECF unbalanced negatively charged ions, mostly Cl-.
- The resulting electrical gradient tends to move Na+ out of the cell
- No further net movement of Na+ occurs when the outward electrical gradient exactly counterbalances the inward concentration gradient. The membrane potential at this equilibrium point is the equilibrium potential for Na+ (ENa+) at +60 mV.
Equilibrium potential-
The membrane potential for a particular ion in which the chemical gradient and the electrical gradient completely balance each other out.
Its important to keep in mind that the membrane potential will ALWAYS be closest in value to the ________________
equilibrium potential of the most permeable ion at that time
the resting membrane potential is -70 mV, because the membrane is ___ times more permeable to K+ than to Na+
30
o Since relative ion concentrations are constantly varying, one would expect the equilibrium potential for individual ions to vary as well. So, how is the equilibrium potential (Eion) calculated?
The Nernst Equation
The nernst equation allows you to calculate ______ if ________ is known.
equilibrium potential
the relative ion concentrations are known.
The Nernst Equation is defined as:
E(ion) = 61/z log [(ion conc. outside cell)/(ion conc. inside cell)]
What two major regulatory systems ensure survival of the body?
The nervous and endocrine systems
What two tissues are excitable?
nerve and muscle
Nerve and muscle tissue can turn their resting potentials into _______
electrical signals
• Any state when the membrane potential is other than 0 mV, means that there is a separation of charge
Polarization
• Membrane becomes less polarized than at resting potential. A result of the inside of the cell becoming more positive
Depolarization
• Membrane returns to resting potential after having been depolarized.
Repolarization
• Membrane becomes more polarized than at resting potential. A result of the inside of the cell becoming more negative.
Hyperpolarization
________ serve as short distance signals
Graded potentials
In graded potentials, the response is directly related to ________
size of the stimulus.
Action potentials: Distance = speed = size = energy use =
long distance
very fast
all the same size
energy costly
Voltage-
A measure of electrical potential energy. Measured in volts. Millivolts are used in the body, not a big voltage
Ohm’s law:
V=IR
Formation of a Graded Potential begins with an event that triggers ________
opening of local membrane ion channels, usually Na+
The site of initiation of a graded potential is called the _______, and it refers to the _____________________
- active site
- inside and the outside of the membrane in that area.
In a graded potential, Depolarization spreads out in what direction?
-all directions
how much sodium flows into a cell during a graded potential?
very little, much less than an action potential
A triggering event size is directly related to the size of a graded potential because a larger stimulus causes ________
more channels to be opened, resulting in a larger influx of Na+ ions.
Graded potentials die over short distances because?
charge-carrying ions (K+) leak out through leaky channels in un-insulated parts of the membrane (de-myelinated regions)
Auto-immune disease that results in the de-myelination of axons in the CNS and PNS
Multiple sclerosis
Multiple sclerosis occurs because graded potentials diminish too quickly due to ________, resulting in ___________
- leakage of K+ through ion channels
- difficulty in locomotion, vision, and constant pain (neuropathy)
Action potentials are defined as brief, rapid, large (up to _____ mV) positive changes in membrane potential during which potential actually _______.
- 100
- reverses (inside of membrane becomes temporarily more positive)
Action potentials involve what portion of the total excitable cell membrane at a time?
a very small portion
Do action potentials decrease in strength as the propagate?
NO
At what point will an action potential form?
the threshold potential
What kind of channels allow for an action potential to occur?
voltage gated ion channels
Refractory period does what?
keep the spread of depolarization from going too far beyond the active site and allows for one way propagation.
In an action potential, the flow of sodium ions in the intracellular fluid reverses the membrane potential from ____ to _____
-70mV to +30 mV
After an action potential, what restores the membrane potential to the resting state?
Flow of potassium ions into the extracellular fluid
At what potential are Na+ and K+ equally permeable?
-15 mV, because it is half the distance between -90 and +60
Voltage gated Na+ channels have what two gates?
an activation gate and an inactivation gate.
Which Na+ voltage gate is most important?
inactivation gate, it is like the lock on a door
what is the shape of the inactivation gate?
ball and chain
Activation gate is found where? and works like a ________ allowing Na+ to cross.
interior of the channel
sliding door
Inactivation gate is found on the side of the channel facing the ________, and is similar in structure to a ball and chain. The ball clogs the channel pore when the channel is closed, and hangs freely when the channel is open.
cell interior
Which gates must be open for Na+ to cross?
BOTH
What three conformation can the Na+ voltage gate be found in?
- Closed, but capable of opening (Activation gate is closed (inner part), but inactivation gate is open (ball and chain))
- Open (Both gates are open, Na+ is allowed to cross)
- Closed, and not capable of opening (activation gate open, inactivation gate is closed). This occurs when channels are inactivated. Called refractory period. Another action potential cannot be initiated until these channels de-inactivate following hyperpolarization of the membrane.
What is the difference between absolute and relative refractory period?
In absolute, all inactivation gates are closed. In relative, fewer gates are closed. Gates are closed in both cases, just fewer gates in relative refract.
What is the reason for refractory period?
All nerves need to fire the same. If the nerve impulses build upon each other, you would get something analogous to tetanus in muscles. This could stop your heart. So refractory period is necessary to reset the action potential so action potentials don’t build upon each other.
What kind of gates does the voltage gated K+ channel have?
only one activation gate
Sodium channels open during ________ by positive feedback
Depolarization
When the sodium channels become inactive, ____________. This repolarizes the membrane
the channels for potassium open.
Which channels are responsible for hyperpolarization and why?
K+
because they are slow to open and close.
Which is more energy costly, and action potential or graded potential?
Action potential
Positive feedback-
the input and the output are identical.
Mosquito bite→ scratch→ histamine release→ causes more itching→ releases more histamine
Negative feedback-
most feedback mechanisms. The input and output are opposites.
Increase in blood sugar→ release of insulin→ decrease in blood sugar
At rest, which channels are open and which are closed?
all the voltage-gated channels are closed, but numerous K+ leak channels, and very few Na+ leak channels are open
At threshold potential, the membrane is about ____ times more permeable to Na+ and K+
600
The voltage-gated Na+ channels are activated at slightly different changes in voltage. So, it takes more depolarization to open some, while only a small amount to open others. o So during the initial depolarization, more channels are opened as ____________
the membrane becomes depolarized.
o This is defined as the membrane potential at which enough voltage-gated Na+ channels have been opened to initiate the positive feedback cycle that will open the remaining channels.
Threshold potential
Upon reaching the threshold potential, why does the membrane potential not reach +30?
Because Na+ channels begin to be inactivated, decreasing permeability
During the stretch from ________________ on an action potential, all of the voltage gated Na+ channels are inactivated. At that point, no stimulus, regardless of how large, can activate the Na+ channel.
the peak to the end of the red line (-70 mV)
Most commonly missed question: During relative refractory period, which channels are closed/open/inactivated. The wrong answer is that they are all closed but not inactivated.
A: some but not all channels are inactivated
Can a stimulus produce a response during relative refractory period? Absolute?
Yes during relative if the stimulus is large
Never during absolute
Which comes first, relative or absolute refractory period?
Absolute
There is always more Na+ outside/inside the cell and more K+ outside/inside the cell.
outside
inside
What restores concentration gradients disrupted by action potentials?
o The Na+/K+ pump
List the basic parts of a neuron
- Cell body
- Dendrites
- Axon
- Axon Hillock
- Axon terminals
Action potentials are initiated at the _________ and conducted throughout a nerve fiber
Axon Hillock
Neuron cell body functions:
- Houses the nucleus and organelles
* Receives and integrates signals from other nerve cells
Dendrites function:
- Project from cell body and increase surface area available for receiving signals from other nerve cells
- Signal toward the cell body
Neuron cell body is also called the ______
soma
____ and ____ serve as a neuron’s input zone
dendrite and cell body
An axon is also called a ______
nerve fiber
Axon function:
- Single, elongated tubular extension that conducts action potentials away from the cell body
- Conducting zone of the neuron
collaterals-
side branches of an axon
Axon hillock-
- First portion of the axon plus the region of the cell body from which the axon leaves
- Neuron’s trigger zone
means “touching” or “next to”
contiguous
Contiguous conduction occurs in what kind of nerve fibers?
un-myelinated
Action potentials spread along every portion of the membrane in _______ conduction
contiguous
Means to “jump”
saltatory
Saltatory conduction occurs in:
myelinated nerve fibers
In saltatory conduction, impulse jumps over ______________.
sections of the fiber covered with insulating myelin (biological insulation)
Is the magnitude of an action potential dependent on the strength of a stimulus?
No
Period following a stimulus in which the voltage-gated Na+ channels cannot open until the resting potential is restored. Period is over when these channels are in the closed-but-capable-of-opening conformation.
Absolute refractory
. A second action potential can be initiated, if the stimulus is stronger than what is normally required.
relative refractory
Exist between regions of myelinated nerve fiber.
Nodes of Ranvier
Myelinated fibers conduct impulses about ____ times faster than unmyelinated fibers of comparable size
50
Myelin is primarily composed of _____, formed by ________ in CNS, and formed by _________ in PNS
lipids
oligodendrocytes
Schwann cells
o Besides myelin, our bodies have evolved __________ to transmit electrical impulses more quickly.
larger diameter axons
Faster conduction from larger axon diameter is due to _____ and _____.
-less internal resistance to local current flow and higher surface area
Higher surface area on axons leads to faster propagation because __________, however the downside is that _________
- more voltage-gated channels are available to carry current.
- The downside to this is that there are more leak channels as well.
Large myelinated fibers that innervate skeletal muscle ~___ mph.
Small, unmyelinated fibers that innervate the digestive tract ~___ mph.
- 270
- 2
Fibers in _____ can regenerate with the help of ________. Fibers in ______ do not have regeneration ability. (The axons themselves do regenerate, but die off quickly)
PNS
CNS
_________ inhibit regeneration of cut central axons
Oligodendrocytes
From an evolutionary stand point, its better to have _____ neurons than _____ neurons.
less
improperly functioning
Regeneration in the CNS is believed to be inhibited by a protein called ______
Nogo
Recent research into CNS damage has involved:
- Function-blocking antibodies to Nogo in mice.
- Peripheral nerve grafts
- Neural stem cells
- Using enzymes to break down scar tissue at sites of injury
The two types of synapses:
Electrical and Chemical synapses
Electrical Synapses-
Two neurons connected by gap junctions. Fly’s response when you go to swat them. Quick. Example is like the hotel door separating two rooms, that’s an analogy for a gap junction.
Chemical Synapses-
Chemical messenger is transmitted across the junction separating the two neurons. Slower, but more reliable.
Vesicles full of neurotransmitter do not leave the presynaptic membrane, they _______
FUSE WITH MEMBRANE and release neurotransmitter
EPSP:
IPSP:
Excitatory post-synaptic potential
Inhibitory post-synaptic potential
Excitatory synapses –
Inhibitory synapses –
- bring the membrane potential higher
- anions entering the cell (more negative); essentially turning it off
What will happen if a neuron recieves both an excitatory and inhibitory input at the same time?
they will cancel each other out
Temporal summation-
One excitatory nerve impulse too weak to cause an action potential is followed by another one quickly after before the first comes back down to rest that will boost the postsynaptic membrane to threshold
Spatial summation-
A post-synaptic membrane is brought to threshold due to simultaneous activation of two (Ex1 & Ex2) or more excitatory presynaptic inputs that individually would not have brought the membrane to threshold.
Name 8 common neurotransmitters
- Acetylcholine
- Dopamine
- Norepinephrine
- Epinephrine; another name for adrenaline.
- Serotonin
- Glycine
- Glutamate
- Gamma-aminobutyric acid (GABA)
neurotransmitters vary from _________, but the same neurotransmitter is always released at _________
- synapse to synapse
- one particular synapse
How large are neuropeptides?
2 to 40 amino acids
Neuropeptides are synthesized in ______________
neuronal cell body in the endoplasmic reticulum and Golgi complex
Neuropeptides’ effects on cells are _____ term
long
Neuropeptides are considered ________ because they don’t cause the formation of EPSP or IPSP, but bring about ______ that subtly modulate, depress or enhance the action of the synapse. They are important in learning, motivation and satiety.
- neuromodulators
- long-term changes
Name 4 neuropeptides
CCK (cholecystokinin), dopamine, glutamate, histamine.
Any given drug that interacts with the nervous system will affect synapses in one of which 3 ways?
- Altering the synthesis, axonal transport, storage, or release of a neurotransmitter
- Modifying neurotransmitter interaction with the postsynaptic receptor
- Influencing neurotransmitter reuptake or destruction (like depression medication)
How does cocaine alter synaptic transmission?
- Blocks reuptake of neurotransmitter dopamine at presynaptic terminals
- Causes a feeling of euphoria
- Your tolerance for dopamine will go through the roof if you are addicted to cocaine– instead of feeling normal when you stop, you feel terrible, which is when you have withdrawal
How does tetanus toxin alter synaptic transmission?
• Prevents release of inhibitory neurotransmitter GABA, affecting skeletal muscles. Spastic paralysis – can’t unclench a muscle. (Lockjaw)
How does strychnine alter synaptic transmission?
• Competes with inhibitory neurotransmitter glycine at postsynaptic receptor site. Spastic paralysis, convulsions, muscle spasticity, and death.
List the 4 types of chemical messengers.
paracrines, neurotransmitters, hormonal singals, neurohormones
Paracrines:
Do they enter bloodstream?
Which cells do the affect?
Provide example:
- No
- only neighboring cells in immediate environment of secretion site.
- histamine
Neurotransmitters:
- Range =
- Respond to?
- How does it reach it’s target?
- Give an example?
- short range chemical messengers
- respond to electrical signals (action potentials)
- diffuses across narrow space to act locally on adjoining target cell (another neuron, a muscle, or a gland)
- Acetylcholine
Hormonal signaling:
- Range?
- Released by?
- example?
- long range
- endocrine glands
- Insulin
Neurohormones: Do they enter the blood? What are they released by? Range? Example?
- Yes
- neurosecretory neurons
- long range
- Vasopressin
Extracellular chemical messengers bring about cell responses primarily by _______
signal transduction
Signal transduction-
o The process by which a target cell receives incoming chemical signals and transforms them into a particular cellular response
Binding of extracellular messenger (first messenger) to matching receptor brings about desired intracellular response by either _________ or ______________.
-Opening or closing channels or activating second-messenger systems
Second messengers help produce the cellular response to a first messenger by __________
Relaying message to intracellular proteins that carry out dictated response
Endocrinology-
Study of homeostatic activities accomplished by hormones.
What are the two distinct groups of hormones?
Hydrophilic hormones and lipophilic hormones
Extracellular signals can cause a tit-load of different responses. Some will open or close channels. _______ a channel is more common in this case.
opening
The two signal transduction pathways that are triggered by most extracellular hydrophilic hormones are:
Tyrosine kinase pathway and GPCR pathway
Kinase-
an enzyme that transfers a phosphate group from ATP to an intracellular protein, through a process called phosphorylation.
Kinases generally trigger a ________, resulting in ________
- signaling cascade
- activation of the final set of proteins that produce the desired effect in the cell.
In the tyrosine kinase pathway, the receptor is also responsible for ________, making it a receptor as well as an enzyme.
kinase activity
Tyrosine Kinase pathway:
• Ligand binding to receptors triggers a process called ________, where one receptor __________. Then the receptors ______________, or add phosphate groups to themselves.
- dimerization
- combines with another
- autophosphorylate
RTK pathway:
o Once dimerization and autophosphorylation have occurred, the receptor recruits cellular proteins to the membrane, where they ___________ and begin the _______________
- are also phosphorylated
- signaling cascade that leads to a cellular response.
Kinases come in 3 classes:______________, depending on the amino acid sites on the substrate proteins that they phosphorylate
-serine, threonine, and tyrosine kinases
A G-protein coupled receptor is a protein that crosses the membrane __ times and is coupled to a ____________. Upon binding of the signaling molecue to the G-protein, the ______ dissociates and binds an effector molecule, which is usually an enzyme. Binding of the α subunit triggers activation of the effector protein, which generally results in the production of _________.
- 7
- heterotrimeric G-protein ( α, β, and γ subunits).
- α subunit
- a second messenger
In GPCR pathway, the second messenger initiates a signaling cascade, which often includes activation of _________, that leads to a cellular response
protein kinase
About half of all drugs prescribed today act on ________________
G-proteins or some part of the G-protein pathway
Examples of GPCR’s are (4):
- Light-activated rhodopsin for night vision.
- Thousands of odorant receptors.
- Receptors for hormones.
- Receptors for neurotransmitters.
Epinephrine acts on GPCR’s. Based on which cell the receptor is attached to, epinephrine can elicit various responses. List 4 epinephrine receptors and their cellular response.
- β-adrenergic receptors on hepatocytes and adipose cells. To release glucose and fatty acids for quick energy (ATP) production
- β-adrenergic receptors on muscle heart cells to increase contraction rates and force. To better transport oxygen and nutrients to muscle cells
- β-adrenergic receptors on smooth muscle cells of the intestines; causes them to relax. To temporarily shut down digestive functions.
- α2 adrenergic receptors in smooth muscles lining blood vessels of skin, intestine, and kidney to constrict vessels to cut off blood flow. To shunt blood to skeletal muscles, heart, and brain. “looks like you’ve seen a ghost”
Epinephrine binds ß-adrenergic receptors to activate _________, which activates _________. On the other hand, _____ or _____ bind α1 and α2 adrenergic receptors to activate ____ which then inhibits adenylyl cyclase.
- Gs
- adenylyl cyclase
- PGE1 (Prostaglandin E1) or Adenosine
- Gi
adenylyl cyclase catalyzes:
ATP → cAMP (second messenger)
Adenylyl cyclase is under _________ control
both positive and negative
Adenylyl cyclase generally has __ catalytic domains and _____ transmembrane domains with _____ helices each
- 2
- 2
- 6
cAPKs-
Example:
- cAMP dependent protein kinases
- PKAs and Ser/Thr kinases
cAPks have 2 ______ subunits and 2______ subunits
regulatory, catalytic
cAPK tetramer is active/inactive? Binding of 2 molecules of cAMP on each _____ subunit causes activation/inactivation?
- inactive
- regulatory
- activation
cAPKs (like PKA) exhibit __________, in that the binding of cAMP to the first subunit drops the Kd for the second binding
cooperativity
Neurotransmitters themselves don’t differ from one cell to the next. What differs is the
___________
receptor type.
Acetylcholine causes skeletal muscles to contract by binding ___________ at the neuromuscular junction, which opens and allows __________ to enter and depolarize the muscle cell, leading to contraction.
- nicotinic acetylcholine receptors
- Na+
Smoking while pregnant is especially bad, because fetus receives more nicotine than you do, which can _______________
disrupt the development of acetylcholine nerves/receptors
Acetylcholine causes heart muscle cells to _____________ by binding ______________, causing a release of ____ from the cell which causes sustained ________
- slow contraction rates
- muscarinic acetylcholine receptors on heart muscle cells
- K+
- hyperpolarization of the cell membrane
Acetylcholine binding in heart cells activates _______ to open K+ channels.
Gßγ subunit
