A given hormone affects ________.
only specific target cells, because nontarget cells lack the appropriate receptors
Which of the following is NOT a means by which cell signal pathways are normally halted?
The signal is halted by the binding of an inactivator molecule to the signal molecule.
?-adrenergic receptors have a higher affinity for norepinephrine than for epinephrine. ?-adrenergic receptors have a higher affinity for epinephrine than for norepinephrine. Which concept about receptor function do these statements reflect?
competition
sensor
senses changes in physiological variables
output signal
will deliver a chemical that will affect the target organ/effector. it can be carried out by a neuron, or a classic hormone released into the blood
input signal
delivers information about environmental stimuli from the periphery to the control center
response
results from changes in organ activity. it can cause a change in the original stimulus
integrating center
synthesizes information coming in from many sensory pathways and sends out the proper response
effector
changes physiological variables in order to restore and maintain homeostasis
What is the order of the reflex pathway
stimulus, sensor, afferent signal, integrating center, efferent signal, effector, response
Describe the function of an afferent neuron.
to deliver information about the physiological variable to the integrating center
a simple endocrine pathway will include
target tissue, endocrine organ, circulatory system, sensor, and classic hormone
Which of the following best describes the role of endocrine organs in both simple and complex reflex pathways?
to function as a sensor and integrating center
Specialized neurons in the brain respond to changes in blood osmolarity (solute concentration). When blood osmolarity strays outside the homeostatic range, these neurons release a neurotransmitter that stimulates neurons of the posterior pituitary, which
neurohormone
In order to prevent damage due to overstretching, skeletal muscles contain specialized sensors. As a muscle stretches, information from these sensors is sent via afferent neurons to the spinal cord where the information is integrated. After integration is
simple neural
TRUE OR FALSE: Autocrine signals are produced by and act upon the same cell.
TRUE
What determines which cells act as targets for endocrine signals?
those cells with receptors specific for the signaling molecule
Neurotransmitters and neurohormones both
are released by neurons and affect only cells with specific receptors.
A chemical that is secreted by a cell to act on cells in its immediate vicinity is called a(n)
paracrine
The most significant difference between a paracrine and an autocrine is
the cell that responds to it.
If the signal molecule acts on the cell that secreted it, the chemical is called a(n)
autocrine.
All molecules secreted by nerve cells (neuromodulators, neurotransmitters, and neurohormones) are known as
neurocrines.
To maintain ________, the body uses a combination of simple diffusion across small distances; widespread distribution of molecules through the circulatory system and rapid, specific delivery of messages by the nervous system.
homeostasis
Most long-distance communication between cells takes place through the ________ and ________ systems with their combination of chemical and electrical signals.
nervous, endocrine
Choose the correct example of signal amplification.
One hormone molecule causes the activation of more than one second messenger molecule.
The ion that controls the widest variety of intracellular activities is __________.
calcium
Why do some normal cells fail to respond to a chemical signal?
Some cells lack the necessary receptors.
Receptor molecules on the surface of a cell
determine that cell's response and may allow a particular ligand to bind.
Receptor molecules are located
- in the outer cell membrane.
-the nucleus.
-the cytosol.
-the cell surface.
Lipophilic hormones
bind to receptors inside the cytoplasm or nucleus.
The ________ link membrane receptors to either ion channels or to membrane enzymes located on the cytoplasmic face of the membrane.
G proteins
Many second messenger systems activate ________, enzymes that transfer a phosphate group from ATP to a protein. The phosphorylation of proteins sets off a series of intracellular events that lead to the ultimate cellular response.
protein kinases
An intracellular signal molecule that translates a signal from a neurotransmitter or hormone into an intracellular response is called a
second messenger.
An ion widely important in intracellular signaling is
calcium
Down-regulation may allow a target cell to
only decrease its number of receptors for a ligand.
________ are molecules that bind to the receptor in such a way that they block the normal ligand from binding and turning the receptor on. As a result, the signal pathway remains inactive.
Antagonists
If the concentration of an endocrine ligand decreases, the target cell may insert more receptors into the cell membrane in an attempt to keep its response at a normal level, in a process known as
up-regulation.
Negative feedback in reflex loops __________.
is common because it promotes homeostasis
Compared to endocrine reflexes, neural reflexes __________.
respond rapidly, and are very brief
An integrating center
evaluates incoming signals and compares it with the setpoint.
Which of the following are considered differences between endocrine and neural control systems?
-duration of action
-speed
-nature of the signal
-specificity
Match the term with its description:
A. threshold
B. effector
C. integrating center
D. setpoint
E. sensory receptor
the desired target value for a parameter
setpoint
_______ receives information about the regulated variable and initiates a response.
integrating center
Match the term with its description:
A. threshold
B. effector
C. integrating center
D. setpoint
E. sensory receptor
the minimum stimulus to trigger a response
threshold
Match the term with its description:
A. threshold
B. effector
C. integrating center
D. setpoint
E. sensory receptor
the organ or gland that performs the change
effector
Match the term with its description:
A. threshold
B. effector
C. integrating center
D. setpoint
E. sensory receptor
continuously monitors its environment for a specific variable
sensory receptor
Homeostatic regulation usually involves a(n) ________ that is sensitive to a particular stimulus (variable) and a(n) ________ whose activity has an effect on the same stimulus.
receptor, effector
glycolysis
the metabolic pathway that breaks down glucose into 2 pyruvate molecules
glycogenolysis
the breakdown of glycogen stores from the liver to produce glucose
glycogenesis
a process by which excess glucose is linked together and stored as glycogen in muscle and liver
gluconeogenesis
the production of glucose from smaller products like lactate and amino acids
lipolysis
the breakdown of triglycerides
fasted-state
the time between meals when the body is performing catabolic reactions in order to maintain blood glucose levels
fed-sate
the time occurring right after a meal when the body is absorbing macronutrients
The magnification of the signal from a water-soluble hormone is achieved through an increase in _______.
cAMP in the cytoplasm
Water-soluble hormones affect target cells by binding to __________.
plasma membrane receptors
How do endocrine hormones reach their target cells?
Hormones are transported through the blood stream to target cells.
What is the role of activated protein kinases?
Phosphorylate proteins.
Cyclic AMP is degraded by __________.
phosphodiesterase
Which form of cell-to-cell communication uses the direct transfer of electrical and chemical signals?
Gap junction signaling
What is a neuromodulator?
A neurocrine that acts slowly in a paracrine manner.
What is the best example of a first messenger?
Insulin, which causes the target cell to take up glucose from the blood.
Which specific characteristic must a signaling molecule have in order to bind to a cytosolic or nuclear receptor?
It must be lipophilic.
Which type of receptor alters the cytoskeleton when its ligand binds to it?
Integrin receptor
The binding of a single ligand to its receptor can activate many second messengers. Which characteristic of signal transduction systems is this?
Signal amplification
Which is the best example of a second messenger?
Intracellular Ca2+
Which gas is also a paracrine signaling molecule?
Nitric oxide