Which of these extracellular signal molecules could diffuse through a plasma membrane and bind to an intracellular receptor? |
estrogen |
A(n) _____ is an example of a signal molecule that can bind to an intracellular receptor and thereby cause a gene to be turned on or off. |
Steroid |
Thyroid hormones bind to _____ receptors. |
intracellular |
Which of these is a logical signal transduction pathway? |
A G-protein-linked receptor activates G protein, which activates phospholipase C, which cleaves a membrane lipid to form IP3, which binds to a calcium channel on the ER, which opens to release calcium ions into the cytoplasm, which bind to an intracellular enzyme that carries out a response. |
What role does a transcription factor play in a signal transduction pathway? |
By binding to DNA it triggers the transcription of a specific gene. |
Which of the following, when activated by a signal transduction pathway, moves from the cytoplasm to the nucleus of a cell? |
Transcription factor |
A signal transduction pathway is initiated when a _____ binds to a receptor. |
signam molecule |
Which of these acts as a second messenger? |
Cyclic AMP |
Calcium ions that act as second messengers are stored in _____. |
endoplasmic reticula |
_____ catalyzes the production of _____, which then opens an ion channel that releases _____ into the cell's cytoplasm. |
Phospholipase C ... IP3 .... Ca2+ |
A protein kinase activating many other protein kinases is an example of _____. |
Amplification |
Which type of hormone is lipid soluble? |
Steroids |
Which molecules determine the tissue specificity of hormones? |
Receptors |
True or false? Lipid-insoluble hormones affect their target cells by binding to receptors inside the cell. |
False |
Which of the following statements about lipid-soluble hormones is true? |
They act by affecting the transcription of genes. |
Which of the following is a structure that allows hormone-receptor complexes to bind to specific DNA sequences? |
Zinc finger |
What is the role of cAMP in the signal transduction pathway activated by epinephrine? |
It binds to and activates protein kinase A, which then phosphorylates other enzymes. |
True or false? For a signal transduction pathway to be activated, hormones must be present in the bloodstream at very high concentrations. |
False |
Vertebrates have two major communication and control systems: the endocrine system and the nervous system. Choose the correct statement describing the coordination of these systems. |
Epinephrine functions as a hormone in the endocrine system and as a neurotransmitter in the nervous system. |
Select the correct statement about feedback regulation in endocrine systems. |
Some homeostatic control systems rely on pairs of negatively regulated hormone pathways, each counterbalance the other. |
A neuron's nucleus is located in its _____. |
cell body |
A nerve impulse moves toward a neuron's cell body along _____. |
dendrites |
A nerve impulse moves away from a neuron's cell body along____. |
axons |
An impulse relayed along a myelinated axon "jumps" from _____ to _____. |
node of Ranvier ... node of Ranvier |
Axons insulated by a(n) _____ are able to conduct impulses faster that those not so insulated. |
myelin sheath |
What type of cell makes up the myelin sheath of a motor neuron? |
Schwann cells |
What part of a neuron relays signals from one neuron to another neuron or to an effector? |
synaptic terminal |
Which term describes the difference in electrical charge across a membrane? |
Membrane potential |
Resting neurons are most permeable to which of the following ions? |
K+ |
True or false? The potential energy of a membrane potential comes solely from the difference in electrical charge across the membrane. |
False |
Which channel is mainly responsible for the resting potential of a neuron? |
Potassium leak channel. |
Which term describes an electrical signal generated by neurons? |
Action potential |
Which channel maintains the concentration gradients of ions across a neuronal membrane? |
The sodium-potassium pump moving Na+ ions out and K+ ions in. |
What behavior is observed if the voltage across a neuronal membrane is set to -20 mV? |
The sodium channel opens, and Na+ ions flow in. |
Which of the following is true of a target cell? |
It must have a receptor for the chemical signal. |
A compound that is secreted in one part of the body and travels through the bloodstream to another part of the body where it has an effect is called a(n) |
Hormone |
Protein signal molecules are not permeable to the cell membrane but can affect their target cells because |
the target cells have cell membrane bound receptors specific to the signal molecule. |
In a normal cell which of the following statements is correct. The membrane potential is negative |
The membrane potential is negative. |
In a portal system how many capillary beds does the blood flow through as it travels from the heart back to the heart? |
2 |
Which structure is not part of a neuron? |
Myelin sheath |
Which of the following statements about action potentials in a given neuron is false? |
They are propagated down the length of the dendrite. |
True or false? Action potentials travel in only one direction down an axon because potassium channels in the neuron are refractory and cannot be activated for a short time after they open and close. |
False |
Which event triggers the creation of an action potential? |
The membrane depolarizes above a certain threshold potential. |
Which of the following terms describes how a neuronal membrane's potential is altered in the presence of inhibitory signals? |
Hyperpolarization |
Where in the neuron do action potentials begin? |
Axon hillock |
How is an action potential propagated down an axon after voltage-gated sodium channels open in a region of the neuron's membrane? |
Sodium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated sodium channels farther down the axon. |
Which of these causes the release of neurotransmitter molecules? |
an action potential reaching the end of the axon |
The space between an axon of one neuron and the dendrite of another neuron is called a(n) _____. |
synaptic cleft |
Neurons store neurotransmitter molecules in vesicles located within _____. |
synaptic terminals |
Which part of the eye is the opening through which light initially passes? |
Pupil |
Which of the following statements does not describe a vertebrate eye? |
It contains many light-sensing columns called ommatidia. |
True or false? The "blind spot" in vertebrate eyes is a region of the retina that contains no photoreceptors. |
True |
Which part of the eye contains the densest concentration of cone cells? |
Fovea |
Which part of the eye bends light to focus it on the retina? |
Lens |
Which of the following statements about photoreception is true? |
The retinal molecule changes shape when it absorbs light. |
True or false? Cone cells are color photoreceptors that use different retinal molecules to absorb different wavelengths of light. |
False |
Identify the correct statement(s) about the resting membrane potential of a cell. 1. Neurons are the only cells that have a charge difference across their membranes. |
2. Potassium (K+) and sodium (Na+) gradients are maintained by active transport in a resting mammalian neuron. 3. Concentration gradients of potassium (K+) and sodium (Na+) across the plasma membrane represent potential energy. |
If the membrane potential of a neuron decreases, the membrane potential _____. |
becomes more positive |
Why is an action potential an all-or-none response to stimuli? |
Because voltage-gated ion channels open when membrane potential passes a particular level |
The plasma membrane of a neuron has voltage-gated sodium and potassium channels. What is the effect of membrane depolarization on these channels? |
Membrane depolarization first opens sodium channels and then opens potassium channels. |
What causes the falling phase of the action potential? |
Inactivation of voltage-gated sodium channels and the opening of voltage-gated potassium channels |
In a normal cell which of the following statements is correct |
The membrane potential is negative |
A membrane depolarization is generally caused by: |
Na+ flowing into a cell |
Excitable cells differ from other cells in that they have___in their membranes |
voltage-gated Na+ and K+ channels |
While membrane depolarizations can be variable, all action potentials are the same. |
True |
Action potentials in myelinated axons propagate: |
using salutatory motion |
Voltage gated Na+ channels have gates. |
2 |
The portion of a neuron that transmits membrane potentials to the cell body is usually the: |
dendrites |
A single neuron can synapse with other neurons |
many |
Post-synaptic cells respond to neurotransmitters through the neurotransmitter: |
binding to a receptor |
An EPSP is caused by the movement of and results in __________. |
Na+, depolarization |
The thick filaments of sarcomeres are composed of _____. |
myosin |
The thin filaments of sarcomeres are composed of _____. |
actin |
A single muscle cell is referred to as a _____. |
muscle fiber |
During the course of muscle contraction the potential energy stored in ATP is transferred to potential energy stored in _____. |
the myosin head |
The release of _____ ions from the sarcoplasmic reticulum is required for skeletal muscle contraction. |
calcium |
Myosin heads bind to _____, which they then pull and cause to slide toward the center of the sarcomere. |
thin filaments |
Of these events, the first to occur when a motor neuron stops sending an impulse to a muscle is _____. |
the pumping of calcium ions out of the cytoplasm and back into the sarcoplasmic reticulum |
In the post-synaptic neuron with a resting potential of -70mV and a threshold of -50mV. Two EPSPs decrease the membrane potential by 15mV each and one IPSP increases the membrane potential by with a 15mV. |
No |
True or false? The horizontal cells are involved in the integration of sensory information. |
True |
True or false? The rods and cone are involved in sensory transduction |
True |
True or false? The amacrine cells are responsible for amplifying the stimulus energy |
False |
During sensory adaptation your response to a stimulus___ |
decreases |
The Central nervous System (CNS) consists of: |
the brain and spinal cord |
The somatic division_____ |
is under conscious control |
If muscles can only shorten when stimulated how is it possible for you to move your limbs in at least two directions (flexed and extended): |
by using pairs of muscles working in opposition to one another |
The binding of actin to myosin during muscle contraction is regulated by |
Ca++ |
True or false? During a muscle contraction the space between the Z-lines will decrease. |
True |