Ch 2 Control of the Internal Environment Flashcards
What are control mechanisms?
Allows the human body to maintain a relatively constant internal environment in spite of stressors
What is homeostasis?
the maintenance of a relatively constant internal environment
What is a steady state (in contrast to homeostasis)?
a steady state represents physiological variables that are unchanging and constant
T or F
The French physiologist Claude Bernard observed that the internal environment of the body constantly varied with change in the external environment.
FALSE; Claude Bernard observed that the internal environment of the body remained REMARKABLY CONSTANT DESPITEEE a changing external environment
Give an example of steady state
- Heart rate; although it changes constantly (80-90bpm for one heart beat), it still maintains a constant rate within the beat
IN CONTRAST TO HOMEOSTASIS LIKE SWEATING WHEN THE WEATHER IS HOT
T or F
Homeostasis is generally reserved for describing normal resting conditions
True
Where does the most intricate of the control systems in the body reside in?
the cells
What are the elements of a biological control system?
1) a sensor or receptor
2) a control center (i.e. center to integrate response)
3) effectors (i.e. organs that produce the desired effect)
A biological control system is composed of how many elements?
3; three
The sensor, upon excitation by a stimulus, sends a message to the
a) efferent nervous system
b) receptor
c) control center
d) effector
c) control center
The control center signals the __ to bring about an appropriate response to correct a disturbance
a) isotope
b) receptor
c) sensor
d) effector
d) effector
Identify the cell activities that are regulated by cellular control systems
breakdown of proteins and energy production
What is a biological control system?
a series of interconnected components that maintain a chemical or physical parameter of the body near a constant value
A type of feedback loop that is the primary method responsible for maintaining homeostasis
negative feedback loop
This excites a sensor and is the signal to begin the operation of a control system, thus representing a change in the internal environment
stimulus
T or F
A majority of the control systems of the body operate via positive feedback
FALSE; mostly operate via negative feedback
What is negative feedback?
an important class of biological control systems in the body that serves to restore normal values of a variable to maintain homeostasis
The __ integrates the strength of an incoming signal from the sensor
control center
When homeostasis is established via the negative feedback mechanism, physiological events result in
negating the initiating stimulus;
giving an opposite response from the initial stimulus to maintain homeostasis
Give an example of positive feedback control system
- enhancement of labor contractions when a woman gives birth
Give an example of a negative feedback control system
- low body temp leads to shivering to increase body heat
- high body temp leads to sweating to decrease body heat
- increasing blood glucose levels triggering the release of insulin to metabolize (decrease) sugar
During labor, increased pressure on the cervix stimulates sensory receptors that trigger the release of oxytocin. Oxytocin in turn promotes increased contractions. This is a classic example of _____.
positive feedback
What is the gain of a control system?
the precision with which a control system maintains homeostasis
In thermoregulation, the hypothalamus receives information about the changes in body temperature and establishes homeostasis by directing appropriate responses. In this instance of negative feedback, the hypothalamus functions as the _____.
control center;
hypothalamus RECEIVES information, NOT TRIGGERED. If hypothalamus was TRIGGERED then it would be sensor but since it is RECEIVING information and DIRECTING appropriate responses (probably to the effectors) then it is a control center
control systems that deal with life-and-death issues
a) maintain true homeostasis
b) are capable of establishing new set points
c) have large gains
d) have small gains
have large gains
When body temperature increases above normal, homeostatic control via negative feedback is triggered by the _____.
thermal receptors in the body
A control system with a large gain is ___.
a) slower in returning to homeostasis
b) more prone to homeostatic disturbances
c) more capable of correcting homeostatic disturbances
d) less capable of returning the system to homeostasis
c) more capable of correcting homeostatic disturbances
The eight major endocrine glands synthesize and secrete blood-borne chemical substances called what?
hormones
Identify a process that is controlled by systems with large gains
regulation of body temp, breathing, and delivery of blood throughout the body
Where is the control center located in the context of regulation of body temperature?
in the brain
When the thermoregulatory control center directs the blood vessels in the skin to constrict, _____.
body heat is conserved; shivering occurs
When the thermoregulatory control center directs the blood vessels in the skin to dilate, _____.
sweating occurs; to promote heat loss
The endocrine system regulates blood glucose concentration by the hormone _____.
insulin
The failure of a blood glucose control system to correct disturbances in homeostasis results in _____.
a) a steady state
b) disease
c) autoimmunity
d) a new set point
b) disease
the maintenance and control of blood glucose levels for homeostasis is a function of what system?
endocrine system
Muscular exercise presents a dramatic test of the body’s homeostatic control systems because it results in large
a) amounts of heat production
b) increases in muscle O2 production
c) increases in muscle CO2 requirements
d) amounts of O2 accumulation
a) amounts of heat production
What are the sensors and control centers for change in body temp (either increase of decrease above normal)?
sensors -> thermal receptors in the body
control center -> hypothalamus in the brain
THIS WASN’T ASKED FOR BUT
effectors -> IF COLD = shiver and IF HOT = sweat
The cell’s ability to respond to a challenge can be
a) improved by prolonged exposure to a specific stress
b) can become severely limited on prolonged exposure to a specific stress
a) improved by prolonged exposure to a specific stress
What is acclimation?
- the improved function of an existing homeostatic system
- the change that occurs in response to repeated environmental stresses and results in the improved function of an existing homeostatic system
- ex: cells can adapt to heat stress due to a hot environment by the production of heat shock proteins.
What is adaptation?
a change in the structure and function of a cell or an organ system that results in an improved ability to maintain homeostasis during stressful conditions
Intracrine signaling is a form of cell signaling mechanism wherein a chemical messenger _____.
a) moves from one cell to the neighboring cell
b )acts on nearby cells to bring about a coordinated response
c) triggers a signaling pathway within the same cell
d) travels by the blood stream throughout the body to target cells
c) triggers a signaling pathway within the same cell
What is intracrine signaling?
occurs when a chemical messenger is produced inside a cell that triggers a signaling pathway within the same cell that leads to a specific response
What is juxtacrine signaling?
occurs when the cells communicate by cell-to-cell contact, in which the cytoplasm of one cell is in contact with the cytoplasm of another through small junctions that connect the two cell membranes
i.e. the method by which one heart cell signals to an adjacent cell to contract
What is autocrine signaling?
occurs when a cell produces and releases a chemical messenger into the extracellular fluid that acts upon the cell producing the signal
i.e. resistance training; muscle cell triggers the DNA in the nucleus to produce more contractile protein which in turn increases the size of that muscle cell
What is paracrine signaling?
occurs when cells produce signals that act locally on nearby cells to bring about a coordinated response
i. e. how immune cells communicate with each other to generate a coordinated attack to protect the body from infection and injury.
ex2: synaptic signaling
What is endocrine signaling?
occurs when cells release chemical signals (hormones) into the blood and these hormones are then carried throughout the body
The signaling mechanism in which a cell contacts another cell through small junctions that connect the two cell membranes is called _____ _______.
juxtacrine signaling
In autocrine signaling, the chemical messenger is _____.
a) sent to nearby cells to bring about a coordinated response
b) released into the extracellular fluid
c) used to trigger a signaling pathway within the same cell
d) carried by the blood stream throughout the body to target cells
b) released into the extracellular fluid
In paracrine signaling, chemical messengers are released _____.
a) to trigger pathways within the same cell
b) via junctions into the adjacent cell
c) into the blood to travel to remote target cells
d) to act on nearby cells
d) to act on nearby cells
Identify the cell signaling mechanism that occurs when a chemical messenger is produced inside a cell that triggers a signaling pathway within the same cell.
intracrine signaling
The cell signaling mechanism that acts locally to bring about a coordinated response is called _____ signaling.
paracrine signaling
