Exam 1 Flashcards
How many cells are in the body
How many of these are RBC’s
100 trillion or more
About 25 trillion are RBC’s
What are the principal components of cells
Nucleus (except in RBC’s) and the cytoplasm
What are the most abundant constituents of cell membranes
Proteins and phospholipids
What is required for neurotransmitters to be ejected from cells by exocytosis
Calcium ions
The sodium-potassium pump account for how much energy consumption in the brain
50%
Calcium ATPases are responsible for maintaining very low cytoplasmic concentrations of calcium by (2 ways)
- Ejecting calcium from the cell (plasma membrane calcium ATPase)
- sequestering calcium in the endoplasmic reticulum via the sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA ATPase)
What are ion channels
Transmembrane proteins that generate electrical signals in the brain, nerves, heart and skeletal muscles
How do ion channels cause conduction of an action potential
Use the energy stored in the chemical and electrical gradients created by sodium-potassium ATPase to rapidly initiate changes in transmembrane potential
What is tetrodotoxin
specific blocker of sodium ion channels as a result of binding to the extracellular side of the channel
what is tetraethylammonium
specific blocker of potassium ion channels by attaching to the inside surface of the membrane
What is P glycoprotein responsible for
the movement of many drugs across the cell membrane
transport of morphine out of CNS, slowing the rate of rise of morphine into the CNS
What is the nucleolus responsible for
synthesis of ribosomes
What is present in the cytoplasm near the nucleus and concerned with the movement of chromosomes during cell division
Centrioles
DNA consists of two complementary nucleotide chains composed of
adenine, guanine, thymine and cytosine
What is included in the Cytoplasm
mitochondria, ER, lysosomes and golgi apparatus
What are mitochondria
power-generating units of cells containing both the enzymes and substrates of the tricarboxylic acid cycle(Krebs cycle) and the electron transport chain
Where does the synthesis of ATP occur
mitochondria
Ribosomes, composed mainly of RNA, attach to the outer portions of
the rough ER
What is the part of the membrane that lacks ribosomes
smooth ER
The smooth ER functions in the synthesis of
lipids, metabolism of carbohydrates and other enzymatic processes
Where is the sacroplasmic reticulum found and what does it do
found in muscle cells and serves as a reservoir for calcium
What are lysosomes
Lipid membrane-enclosed globules providing an intracellular digestive system
What are the digestive enzymes lysosomes are filled with
hydrolytic enzymes
Bactericidal substances in the lysosome kill phagocytized bacteria before they can cause cellular damage. These bactericidal substances include
- lysozyme (dissolves cell membranes of bacteria)
- lysoferrin (binds to iron and other metals essential for bacterial growth
- acid that has a pH <4
- hydrogen peroxide (can disrupt some bacterial metabolic systems)
What is the Golgi apparatus
Collection of membrane-enclosed sacs responsible for storing proteins and lipids
Also performs postsynthetic modifications including glycosylation and phosphorylation
Where are proteins synthesized in the rough ER transported to
What are they stored in
Where are they released (2 answers)
Golgi apparatus
Secretory vesicles
The cell’s cytoplasm or transport to the surface for extracellular release via exocytosis
When do exocytotic vesicles release their contents
continuously
When do secretory vesicles release their contents
they store the packaged material until a triggering signal is received (neurotransmitter release)
Where are lysosomes created
Golgi apparatus
What are eukaryotes
cells that have a nucleus (plants, animals, fungi)
What are prokaryotes
cells who do not have a nucleus (bacteria)
Where is DNA transcribed
nucleus
Once DNA is transcribed it is translated into messenger RNA (mRNA) in the
ribosomes
mRNA in the ribosomes of the cells are converted into
proteins
The maintenance of a normal cell volume and pressure depends on
sodium-potassium pump (ATPase)
How many functional types of proteins are within the cell membrane
5
What do channel proteins do
move ions through the cell membrane by concentration gradients
What do transport (carrier) proteins do
help ions and molecules move against their concentration gradient with the use of ATP (Sodium-potassium pump)
What do integral proteins do
completely transverse the cell membrane and allow substances through move through (channel and pump)
What do peripheral proteins do
associated with and conducts enzymatic and hormonal reactions
Where are peripheral proteins lovated
can be located inside or outside of the cell but they do not transverse the cell membrane
What do receptor proteins do
allow substances to bind and elicit responses
Where are structural proteins found
microtubules
What is a protein
a chain of amino acids (polypeptide)
translated from mRNA
What can proteins be (3 answers)
- enzymes (involved with catalyzing chemical reactions)
- receptors (control signaling to mitochondria)
- hemoglobin (found in muscle and organ tissue)
Transmission of impulses between responsive neurons at a synapse is mediated by
Release of a neurotransmitter from the presynaptic terminal (ex. glutamate &. GABA)
What nerve fibers transmit impulses from peripheral receptors to the CNS
Afferent
What nerve fibers transmit impulses from the CNS to the periphery
Efferent
How are afferent nerve fibers classified
Based on their diameter and velocity of conduction on nerve impulses (A, B, C)
How are type-A fibers subdivided
alpha, beta, gamma
What type of fibers transmit signals regarding cutaneous mechanoreceptors
A-beta
Touch and fast pain are transmitted by what kind of fibers
lightly myelinated type a-delta fibers with free nerve endings
What type of fibers transmit slow pain, pruritus and temperature sensation
Type C fibers
What nerve fibers have myelin
Type A and B
What type of fibers are unmyelinated
Type C
The successive excitation of nodes of Ranvier by an action potential that jumps between successive nodes is
Saltatory conduction
During much of the action potential the cell membrane is completely refractory to further stimulation. This is called
Absolute refractory period. Caused by the presence of a large fraction of inactivated sodium ion channels
During the last portion of the action potential a stronger than normal stimulus can evoke a second action potential. This is called
relative refractory period
What blocks many types of potassium ion channels
Tetraethylammonium
What blocks many types of sodium ion channels
Tetrodotoxin
Where are the sites of continuous synthesis and storage of neurotransmitters (2 answers)
Synaptic vesicles of the cell body and dendrites of neurons
Can vesicles contain and release only one neurotransmitter
No, they can contain and release more than one neurotransmitter
What is an important coagonist at the NMDA receptor
Glycine
How many classes of cell surface receptors are there?
What are they
3
G protein coupled receptors, ligand-gated ion channels and enzyme-linked transmembrane receptors
Rapid synaptic transmission is accomplished entirely through what kind of channels
voltage-gated ion channels
What are examples of tyrosine kinase-linked membrane receptors (3)
the insulin receptor, atrial natriuretic peptide receptor and the receptors for many growth factors
What kind of intracellular receptors act in the nucleus where they directly regulate the transcription of specific genes? (2)
steroid receptors and thyroid hormone receptors
What kind of inhibitors act in the cytosol by inhibiting the activity of phosphodiesterase, increasing the cytosolic concentration of cyclic adenosine monophosphate (cAMP)
phosphodiesterase inhibitors
what are the three components of a G protein-coupled receptor
a receptor protein, three G proteins (alpha, beta and gamma) and an effector mechanism
Binding of an extracellular ligand to the G protein-coupled receptor triggers conformational change of the protein. That change causes activation of the G alpha protein coupled to the interior portion of the receptor. How does the activation occur?
It occurs by exchanging a GDP moiety that is bound to the protein for a GTP.
Beta adrenergic receptors couple with stimulatory G alpha proteins and increase the activity of
Adenylyl cyclase (adenylate cyclase)
Opioid receptors associate with inhibitory G alpha proteins that
decrease the activity of adenylyl cyclase
Many hormones and drugs act through G protein-coupled receptors including (4)
catecholamines, opioids, anticholinergics and antihistamines
Dopamine has high concentrations in the
Basal ganglia
Dopamine is important to the reward centers of the brain and plays a key role in (2)
addiction and tolerance to anesthetic and analgesic drugs
Norepinephrine is present in large amounts in (2)
the reticular activating system and hypothalamus
The sedative action of dexmedetomidine is mediated by activation of alpha-2 adrenergic receptors in the
locus ceruleus
How does dexmedetomidine work in the receptors of the locus ceruleus
inhibits firing of the ventral lateral preoptic nucleus of the hypothalamus (VLPO)
What type of neurotransmitter is substance P
excitatory neurotransmitter
Where is substance P release
It is coreleased by terminals of pain fibers that synapse in the substantia gelatinosa of the spinal cord
What type of G protein-coupled receptor does substance P activate
neurokinin-1
What type of agonists are endorphins
Where are they secreted
endogenous opioid peptide agonists
Secreted by nerve terminals in the pituitary, thalamus, hypothalamus brainstem and spinal cord
What do endorphins act through
mew opioid receptors
The release of what is facilitated by endorphins
dopamine release
What do endorphins activate
inhibitory pain pathways
Serotonin is present in high concentrations in
the brain
Serotonin in the brain acts on (2)
ligand-gated ion channels and g protein-coupled receptors
Where are serotonin receptors located
Chemoreceptor trigger zone
What are serotonin receptors in the chemoreceptor trigger zone inhibited by
ondansetron, granisetron and other common antiemetic drugs
Histamine is present in high concentrations in the
Hypothalamus and reticular activating system
Histaminergic neurons active during the wake cycle are located in the
tuberomammillary nucleus of the hypothalamus
The sleep promoting properties of antihistamine drugs that cross the BBB are due to inhibition of
H1 G protein-coupled receptors
Three basic types of ion channels
ligand-gated ion channels (ionotropic receptors), voltage-sensitive ion channels and ion channels that respond to other types of gating
Nicotinic acetylcholine receptors are opened in the presence of
acetylcholine
Serotonin receptors are opened in the presence of
serotonin
GABA receptors are opened in the presence of
GABA
Glycine receptors are opened in the presence of
glycine
The native agonist for NMDA and AMPA is
glutamate
What type of neurotransmitter is acetylcholine and what does it activate
excitatory
muscarinic and nicotinic receptors in the CNS
Nicotinic acetycholine receptors are nonspecific cations and is
depolarizing
Where are nicotinic acetylcholine receptors in the brain commonly located
presynaptic location
G protein-coupled muscarinic acetylcholine receptors in the peripheral parasympathetic nervous system have what type of effect
inhibitory effect
Nicotinic acetylcholine receptors are also responsible for
activating muscle contraction
Nondepolarizing muscle relaxants work by blocking
the acetylcholine binding site. Causes depolarization-excitatory
What is the major excitatory amino acid transmitter in the CNS
glutamate
Glutamate receptors are
excitatory and depolarizing
Glutamate plays a key role in
learning, memory, central pain transduction and pathologic processes such as excitotoxic neuronal injury following CNS trauma or ischemia
What is glutamate synthesized by
the deamination of glutamine via the Krebs cycle
Glutamate is released into the synaptic cleft in response to
depolarization of the presynaptic terminal
The two main subgroups of glutamate receptors are
inotropic and metabotropic receptors
What are three examples of ionotrpic glutamate receptors
NMDA, AMPA and kainate receptors
Metabotropic glutamate receptors are transmembrane receptors that are linked to
They modulate with second messengers such as
G proteins
inositol phosphates and cyclic nucleotides
The serotonin receptor is
excitatory
What is the major inhibitory neurotransmitter in the brain
GABA
What happens when two molecules of GABA bind to the GABA receptor
the chloride channel in the center of the receptor opens and chloride ions enter the cell
GABA receptors are
inhibitory
What is the principal inhibitory neurotransmitter in the spinal cord
Glycine
Why do strychnine and tetanus toxin result in seizures
they antagonize the effects of glycine on postsynaptic inhibition
Voltage-gated ion channels are present in (3)
neurons, skeletal muscles and endocrine cells
The human ether-a-go go related gene (hERG) is mostly famous for its association with
prolonged QT syndrome
The hERG potassium channel is sensitive to many drugs and is responsible for sudden death from drugs that predispose the patient to
Torsades de point
Downregulation
excess circulation concentrations of ligand often results in a decrease in the density of the target receptors in cell membranes
Desensitization
waning of a physiologic response over time despite the presence of a constant stimulus
Upregulation
drug-induced antagonism of receptors often results in an increased density of receptors in cell membranes (one reason most cardiac medications should be continued through perioperative period)
