BIOL 365 - Final Flashcards
What characteristic of chemical messenger structure has the most significant impact on its signalling mechanism?
Hydrophobicity.
What effector(s) (and 2nd messenger(s)) are stimulated by Gαs?
Adenylyl cyclase (cAMP, PKA).
What does the Goldman-Hodgkin-Katz equation define?
The membrane potential of a cell based on distribution, relative permeability, and charge of ions across the membrane.
What 2 variables affect the time constant (τ)?
- Resistance of the cell membrane (rm)
- Capacitance of the cell membrane (cm)
What type of steroid hormone is aldosterone?
Mineralocorticoid.
Do GABAA receptors cause depolarization (excitatory) or hyperpolarization (inhibitory)?
Hyperpolarization (inhibitory).
What type of chemical messenger is norepinephrine?
Amine hormone.
Which type of pancreatic cell is destroyed in type 1 diabetes?
β cells only.
How is the medulla oblongata positioned in the brain?
At the top of the spinal cord.
Where is GLUT1 found?
In all tissues of the body.
What are the 2 major elements of the cytoskeleton?
- Microtubules
- Microfilaments
What type of channel are nicotinic acetylcholine receptors (nAChRs)?
Ligand-gated cation channels (for Na+, Ca2+, and K+ flux).
Which ions are transported through NMDA receptors?
- Na+
- K+
- Ca2+
What is the main function of Na+/K+ ATPase?
To maintain the concentration gradients of Na+ and K+ across the cell membrane.
What is our blood glucose level after feeding?
9-11 mM.
What pathway occurs when receptor guanylyl cyclase is activated by atrial natriuretic peptide (ANP)?
- Receptor converts GTP to cGMP
- cGMP activates PKG
- PKG phosphorylates target proteins that relax smooth muscle
- Smooth muscle relaxation causes vasodilation
- Blood pressure is lowered
What type of chemical messenger are catecholamines?
Amine hormones.
What is described by the electrochemical driving force of a cell?
How far the membrane potential is from equilibrium.
What type of chemical messenger is aldosterone?
Steroid hormone.
What triggers oxytocin release for positive feedback regulation of uterine contraction?
Stretch receptors in the cervix, activated by contraction, send signals to the hypothalamus that are relayed to the posterior pituitary gland, which releases oxytocin to stimulate further contraction.
What is the equation for the time constant (τ)?
τ = rmcm
- r = resistance of the cell membrane
- c = capacitance of the cell membrane
Which 2 motor proteins are associated with microtubules?
- Kinesin
- Dynein
How many subunits are in a complete nicotinic acetylcholine receptor (nAChR)?
5.
What effector(s) (and 2nd messenger(s)) are inhibited by Gαi?
Adenylyl cyclase (cAMP, PKA).
What is the typical age of onset for type 1 diabetes?
Very young (childhood onset).
What are 2 major capping proteins associated with microfilaments?
- Tropomodulin
- CapZ
Why is it important that a small number of steroid hormones in circulation are not bound to carrier proteins?
Any unbound molecules leaving circulation for the target cell cause a significant decrease in the concentration of free hormone, so more hormones are released from their carrier proteins to reach chemical equilibrium and are then free to diffuse into the target cell.
At what end do microfilaments tend to shrink?
(-).
What is the basic structure of cilia and flagella?
9 pairs of microtubules bundled in parallel around a central pair, arranged into an axoneme.
Which type of G-protein is involved in inositol-phospholipid signalling?
Gq.
What type of chemical messenger is AMP?
Purine.
What are the 2 main advantages of the greater number of neurons and synapses that comes with a more complex nervous system?
- Integration of information happens at synapses: greater potential for complex behaviours
- Memories are stored in synapses: greater potential for learning
What is MEK?
A protein kinase activated by Raf-1 that phosphorylates and activates MAP-kinase as part of the Ras-MAP-kinase signalling pathway.
What is GLUT4?
An intracellular glucose receptor that is translocated to the surface of a pancreatic β cell as a result of signal transduction in response to elevated blood glucose levels.
What region of the brain is the master controller of circadian rhythm?
Suprachiasmatic nucleus (SCN).
How is conductance related to resistance?
Conductance is the reciprocal of resistance.
What property of action potentials prevents backward transmission and summation of action potentials along an axon?
The absolute refractory period.
Which region of the brain is responsible for converting short-term memory to long-term memory?
Hippocampus (limbic system).
Which 2 scientists at the Montreal Neurological Institute determined the somatotropic organization of the cerebral cortex?
- Wilder Penfield
- Herbert Jasper
How are peptide hormones usually stored?
In intracellular vesicles, as prohormones.
Who won the 1923 Nobel for discovering insulin?
Frederick Banting.
How do ions flow through chemical synapses?
Across the synaptic cleft and into postsynaptic channels.
What is the main role of eicosanoids?
Inflammation and pain.
How are steroid hormones released?
They freely diffuse through the membrane and into the blood, where they are bound to carrier proteins for delivery to target cells.
In addition to GLUT1, which is expressed in all tissues, which glucose receptor is well expressed and working constantly in the brain?
GLUT3.
What is synaptotagmin?
A protein found in the synaptic vesicle membranes of chemical synapses; when activated by Ca2+, it binds SNARE proteins to bring vesicle and presynaptic membranes closer together in preparation for membrane fusion and neurotransmitter release.
What are tropic hormones?
Hormones that cause the release of another hormone.
What is the somatosensory function of muscle spindle receptors?
Proprioception.
Which region of the brain is responsible for maintaining homeostasis?
Hypothalamus (limbic system).
Where is acetyl CoA synthesized?
Mitochondria.
In a chemical synapse, what is the first thing that happens when an action potential reaches the presynaptic terminal?
Depolarization causes opening of voltage-gated Ca2+ channels.
What is a first-order endocrine pathway?
A signalling pathway in which the component receiving sensory input also acts as the integrating centre for the signal.
In what direction does kinesin move along microtubules?
Toward the positive end.
Which 2 types of receptors in the digestive tract relay information to the pancreas to regulate insulin secretion?
Glucose and stretch receptors.
What effector is activated by Gαo and Gαq?
PLC-β.
At which end do microtubules grow by dimer addition?
(+).
What types of G-proteins are involved in cAMP signalling?
Gs and Gi.
Does cortisol have an additive or a synergistic effect on glucagon and epinephrine?
Synergistic.
What conditions do NMDA receptors require before they can open?
- Membrane depolarization (to relieve Mg2+ block)
- Binding of glutamate and glycine
What is the general value of capacitance for cells (lipid bilayer)?
1 μF/cm2.
What is the reversal (equilibrium) potential for nicotinic acetylcholine receptors (nAChRs)?
Approx. 0 mV.
What is glutaminase?
An enzyme that catalyzes the conversion of glutamine to glutamate, which can be released as a neurotransmitter.
What are the 2 main functions of the cortex?
- Integrate/interpret sensory information
- Initiate voluntary movements
Which region of the brain is responsible for reward and addiction?
Nucleus accumbens (limbic system).
Do glutamate receptors cause depolarization (excitatory) or hyperpolarization (inhibitory)?
Depolarization (excitatory).
What is white matter?
The portion of brain/spinal cord tissue made up of tracts of axons and their myelin sheaths.
How does the absolute refractory period ensure unidirectional signalling along axons?
As depolarization travels down the axon, Na+ channels immediately behind a region of depolarization are in their absolute refractory period (inactive state) and cannot initiate another action potential, so further depolarization can only happen further away from the axon hillock.
What is the effect of lower resistance of the cell membrane on conductance?
Lower conductance (greater decrease in voltage along the axon).
In crustaceans, where is crustacean hyperglycemic hormone (CHH) synthesized and secreted?
Sinus gland cells in the eyestalks.
What does it mean for hormones to be additive?
The effect of the combined hormones on the target cell is equal to the sum of the individual effects of each hormone.
What enzyme synthesizes phosphatidyl inositol?
Phospholipase C.
What type of chemical messenger is thyroxine?
Amine hormone.
What is MAP-kinase?
An effector protein activated by MEK as part of the Ras-MAP-kinase signalling pathway that can phosphorylate many different cellular proteins, including transcription factors, to have many different effects in the cell.
Which somatosensory receptors have the lowest conduction velocity?
C-type free nerve endings (pain, temperature, itch): 0.5-2 m/s.
At what end do microfilaments tend to grow?
(+).
What is the role of Gαolf?
To stimulate adenylyl cyclase in olfactory sensory neurons.
What are the main 3 hormones involved in the HPA axis of the stress response?
- Corticotropin-releasing hormone (CRH)
- Adrenocorticotropic hormone (ACTH)
- Cortisol
What are the 2 main disadvantages of large axons (as a means of increasing conduction speed)?
- Take up more space, limiting number of neurons that can be packed into the nervous system
- Require greater volume of cytoplasm, making them expensive to produce and maintain
What type of chemical messenger is ATP?
Purine.
In myelinated axons, what are internodes?
Myelinated regions between nodes of Ranvier.
What growth factor activates type II receptor serine/threonine kinases?
TGF-β.
What is the glucose affinity of GLUT1 and GLUT3?
1 mM.
What type of chemical messenger is vasopressin?
Peptide hormone.
What is crustacean hyperglycemic hormone (CHH)?
A neurohormone secreted from crustacean eyestalks to control glucose levels in crustaceans.
What 2 properties of an axon can increase its speed of conductance?
- Myelination
- Increased axon diameter
Why does a greater value of λ (length constant) increase the speed of conduction along an axon?
Higher λ means lesser decay of current over distance, so electrotonic current flow within the axon after an action potential is faster.
What motor protein is associated with microfilaments?
Myosin.
What is the monomeric form of actin?
G-actin.
Which 3 parts of the brain are permeable (i.e. are not shielded by the blood-brain barrier)?
- Pineal gland
- Pituitary gland
- Parts of the hypothalamus
What is the equation for current (electrochemical driving force)?
Ix = gx(Vm - Ex)
- Ix = current for ion x
- gx = conductance of ion x
- Vm = membrane potential (from Goldman-Hodgkin-Katz equation)
- Ex = equilibrium potential of ion x (from Nernst equation)
What are ventricles (brain)?
Cavities in the brain that contain cerebrospinal fluid (CSF).
How does the number of K+ leak channels along an axon affect its ability to conduct electrical signals?
More K+ leak channels means more loss of positive charge for greater current loss and voltage decrease along the axon.
How are the different regions of the cerebral cortex organized?
Each region corresponds to a specific part of the body that it controls by motor output or from which it receives sensory input.
What type of chemical messenger is GTP?
Purine.
What type of steroid hormone is estrogen?
Reproductive hormone.
What is the value of the gas constant, R?
8.31 J/mole·K.
What are the 3 layers of the mammalian cranial and spinal meninges?
- Dura mater (outer)
- Arachnoid mater (middle)
- Pia mater (inner)
What happens when a cell membrane depolarizes?
The membrane potential becomes more positive.
How are white and grey matter organized in the spinal cord?
- White matter on the surface
- Grey matter on the inside
What are the 3 subsystems of the somatosensory system?
- Cutaneous mechanoreceptors (touch, vibration, pressure)
- Proprioception (limb position, load on joints)
- Pain/temperature
What is the frequency of type 1 diabetes in the general population?
Approx. 1-2 in 10,000.
What action is responsible for dynamic instability in microtubules?
Intrinsic GTPase activity of β-tubulin.
Where are the adrenal glands in mammals?
On top of the kidneys.
What type of steroid hormone is progesterone?
Reproductive hormone.
Do 5-HT3 channels cause depolarization (excitatory) or hyperpolarization (inhibitory)?
Depolarization (excitatory).
Which region of the brain is responsible for aggression and fear responses?
Amygdala (limbic system).
What types of somatosensory receptors are involved in pain, temperature, and itch sensation?
Free nerve endings.
What is a connexin?
A protein complex forming part of each hemichannel in a gap junction.
What type of chemical messenger is epinephrine?
Amine hormone.
What is the axon hillock?
The region of a neuron cell body where incoming signals from dendrites converge just before the axon and may summate to produce an action potential.
Which motor protein moves toward the negative end of microtubules?
Dynein.
What type of receptor does crustacean hyperglycemic hormone (CHH) bind in glucose control pathways?
A receptor guanylyl cyclase.
What is a threshold potential?
A minimum level of depolarization that must be reached at an axon hillock in order for an action potential to fire.
Where is GLUT2 well expressed?
Pancreatic β cells and liver cells.
What type of chemical messenger is histamine?
Amine hormone.
What is the hippocampus?
The region of the limbic system responsible for converting short-term memory to long-term memory.
How do ions flow through electrical synapses?
Through gap junctions.
Which 2 groups of vertebrates have discrete adrenal glands?
Birds and mammals.
What is the effect of glucagon on blood glucose levels?
Glucagon raises blood glucose levels.
What type of chemical messenger is melatonin?
Amine hormone.
How does increased surface area of conducting surfaces affect capacitance?
Increases capacitance.
Which somatosensory receptors have the highest conduction velocity?
Muscle spindles (proprioception): 80-120 m/s.
What is the cerebral cortex?
The outer layer of the cerebrum.
What is CapZ?
A capping protein that associates with microfilaments at the (+) end to prevent actin polymerization, slowing growth.
In what type of signalling pathway are Gq proteins involved?
Inositol-phospholipid signalling.
Are amine hormones hydrophilic or hydrophobic?
Hydrophilic (except for thyroid hormones).
What happens when phospholipase C reacts with PIP2?
PIP2 is cleaved into IP3 and DAG, each of which can have several downstream effects.
Which tissue types have large intracellular pools of GLUT4 receptors?
Muscle and fat tissue.
What fuels the movement of kinesin and dynein along microtubules?
ATP hydrolysis.
What is the Nernst equation?
- Ex = Nernst potential for ion x
- R = gas constant (8.31 J/mole·K)
- T = temperature (K; 295 K at room temp.)
- F = Faraday’s constant (96,500 coulombs/mole)
- z = valence of ion x
- [x]o/[x]i = concentration of ion x outside/inside the cell
What type of receptor are insulin receptors?
Receptor tyrosine kinase (RTK).
What is the main function of the mesencephalon (midbrain)?
Coordinating and initiating reflex responses to auditory and visual input.
What is the olfactory bulb?
The region of the limbic system responsible for sense of smell.
Which region of the brain is reduced in size and function in mammals, compared to the same region in fish and amphibians?
Mesencephalon (midbrain).
What type of chemical messenger is triiodothyronine?
Amine hormone.
What is the equation for the length constant (λ)?
λ = [rm ÷ (ri + ro)]½
- rm = resistance of the membrane
- ri = resistance of intracellular fluids
- ro = resistance of extracellular fluids
Which glutamate receptor subunits are found in NMDA receptors?
- GluN1
- GluN2A-D
- GluN3A-B
What type of chemical messenger is atrial natriuretic peptide (ANP)?
Peptide hormone.
Which glucose receptor is well expressed and constantly working in all tissue types?
GLUT1.
What is the main function of the cerebellum?
Motor coordination.
What electrical property is an approximation of ion permeability in a cell membrane?
Conductance.
Which hormone lowers blood glucose levels?
Insulin.
Where are steroid hormones synthesized?
At the smooth ER or in the mitochondria.
Which ion is transported through GABAA receptors?
Cl-.
How does myelination affect the length constant (λ) of axons?
Myelin increases membrane resistance, which increases λ.
How are microtubules formed?
- Tubulin dimers associate end-to-end to form a protofilament
- Protofilaments line up laterally to form a sheet
- Sheet rolls up into a tube
- Microtubule grows at (+) end by addition of new dimers (and shrinks at (-) end)
In what form are peptide hormones usually synthesized?
Preprohormones.
What types of molecules can travel through gap junctions?
Ions and hydrophilic chemical messengers.
What is the main endocrine function of the pancreas?
Secrete insulin and glucagon to regulate blood glucose levels.
What are the 4 general components of a signal transduction pathway?
- Receiver (ligand-binding region of receptor)
- Transducer (conformational change of receptor)
- Amplifier (increases number of molecules affected by signal)
- Responder (molecular functions that change in response to signal)
What is cerebrospinal fluid (CSF)?
A fluid that fills spaces within the central nervous system and acts as a shock absorber.
What 3 major steroid hormones are made directly from progesterone?
- Cortisol
- Corticosterone
- Testosterone
Where are the receptors involved in proprioception located?
- Muscles
- Tendons
- Joints
How does increased thickness of an insulating layer affect capacitance?
Decreases capacitance.
What is the effect of increased resistance of extracellular and intracellular fluids on conduction over distance?
Lower conductance (greater decrease in voltage along the axon).
True or false: The opening and closing of gap junctions can be regulated.
True.
What organ secretes epinephrine during the stress response?
Adrenal medulla.
What proportion of diabetics have type 1 diabetes?
Approx. 10%.
What is the limbic system?
A network of connected structures between the cortex and the rest of the brain that influences emotions, motivation, and memory (the “emotional brain”).
What molecule is intermediate between progesterone and aldosterone?
Corticosterone.
How many neurons are in the brain?
Approx. 1011.
What type of chemical messenger is serotonin?
Amine hormone.
What are the 5 main regions of the prosencephalon (forebrain)?
- Cerebrum
- Hippocampus
- Thalamus
- Hypothalamus
- Limbic system
Which region of the somatosensory system is responsible for relaying sensory information from the head and face?
Cranial root ganglia.
What feature of the central nervous system (CNS) is unique to vertebrates?
Hollow dorsal nerve cord (spinal cord).
What is Ras?
A protein kinase activated by SOS that activates Raf-1 as part of the Ras-MAP-kinase signalling pathway.
How are steroid hormones stored?
They can’t be stored because they are hydrophobic–they have to be made on demand.
What happens to tyrosine kinase receptors (RTKs) when they are bound by a ligand?
One RTK dimerizes with another, and they phosphorylate each other to become active and recruit other kinases.
What are the 2 main parameters regulated by atrial natriuretic peptide (ANP)?
- Extracellular fluid volume
- Blood pressure
What causes intracellular GLUT4 to be translocated to the cell surface?
Phosphorylation during insulin signal transduction.
What are the 3 main classes of steroid hormones?
- Mineralocorticoids
- Glucocorticoids
- Reproductive hormones
What type of chemical messenger is acetylcholine?
Amine hormone.
Which nicotinic acetylcholine receptor (nAChR) subunits are found in muscle nAChRs?
- α
- β
- γ/ε
- δ
What nicotinic acetylcholine receptor (nAChR) subunits are found in neuronal nAChRs?
- α2 - α10
- β2 - β4
What causes the symptoms of type 1 diabetes?
Autoimmune destruction of pancreatic β cells (mediated by T cell lymphocytes), leading to a lack of insulin production.
What is the effect of insulin on blood glucose levels?
Insulin lowers blood glucose levels.
How many meninges do mammals have?
3.
What effect does the opening of Na+ channels have on the cell membrane?
Depolarization.
What two signalling pathways are involved in the stress response?
- Sympathetic nervous system
- Hypothalamus-pituitary-adrenal cortex (HPA) axis
What type of chemical messenger is GMP?
Purine.
How many pairs of cranial nerves do vertebrates have?
13.
What are the cranial root ganglia?
Cell bodies of afferent fibres that relay sensory information from the face and head.
Do P2X receptors cause depolarization (excitatory) or hyperpolarization (inhibitory)?
Depolarization (excitatory).
What are 5 major factors affecting growth/shrinkage of microtubules?
- Local tubulin concentration
- Dynamic instability
- Microtubule-associated proteins (MAPs)
- Temperature
- Chemicals (e.g. poisons)
Where do neurons of the hypothalamus terminate?
Posterior pituitary.
Once acetylcholine (ACh) has been broken down in the synaptic cleft by acetylcholinesterase (AChE) into choline and acetate, what happens to the choline and acetate?
- Choline: taken up and recycled by the presynaptic neuron
- Acetate: diffuses out of the synapse
Do glycine receptors cause depolarization (excitatory) or hyperpolarization (inhibitory)?
Hyperpolarization (inhibitory).