Chapter 01 Homeostasis: A framework for Human Physiology Flashcards
What is homeostasis?
Homeostasis
Most of the common physiological variables of the body are maintained within a ______ range
predictable
Is homeostasis a static or dynamic process?
Dynamic process, not static.
values aimed to be kept at a constant range.
‘set point’
Physiological variables can change dramatically over a 24-hr. Period, but the system is still in overall balance
true
What is an example of a physiological variable maintained by homeostasis?
Body temperature (36.5 - 37.8)
blood pressure
Heart rate
Blood sugar level
Platelet count
Oxygen and CO2 levels in the blood
Resting metabolic rate
Na and K concentration
Other examples include blood pressure, heart rate, blood sugar level, and oxygen levels.
Homeostasis is maintained
through a complex system of feedback loops, primarily negative feedback loops, where the body constantly monitors internal conditions and adjusts them to keep vital parameters
Physiology
Homeostasis is not maintained, which can result in various physiological disruptions
Pathophysiology
High body temperature is maintained by
sweating
Heart rate, normal and abnormal
(55 - 100 bpm, < bradycardia, > tachycardia)
Blood sugar level, normal and abnormal
(~ 70 - 100 mg/dL, < hypoglycemic, > hyperglycemic)
Example of dynamic constancy
Blood glucose levels increase after eating
Levels return to their set point via homeostasis
Levels change over short periods of time, but remain relatively constant over long periods of time
maintains body temperature when room temperature increases
Homeostatic control system
What happens to blood glucose levels after eating?
Blood glucose levels increase after eating and return to their set point via homeostasis.
Feed forward
Enhances the production of the product and usually indicates possible illness.
Positive feedback system
example Positive feedback system
Continuous increase of oxytocin during childbirth
Thyroid storm
Give an example of a positive feedback system.
Continuous increase of oxytocin during childbirth.
Another example is a thyroid storm.
Shuts the system off once the set point has been reached.
Most of the important body feedback systems will be based in this
Negative feedback system
controls the sequence of chemical reactions by inhibiting the sequence’s rate-limiting enzyme, “Enzyme A.” inNegative feedback systems
“Active product”
Anticipates changes in regulated variables to improve the speed of the body’s homeostatic responses
Minimizes fluctuations in the level of the variable being regulated
possible illness, cannot be stopped
Feedforward Regulation
Feedforward Regulation examples
When outside temperature decreases, neurons detect the change and relay information to the brain
The smell of food triggers nerve responses from smell receptors in the nose to the cells of the digestive system
A specific involuntary, unpremeditated, unlearned “built-in” response to a particular stimulus
Reflex
The pathway mediating a reflex
Reflex arc
What are the components of a reflex arc?
Stimulus, receptor, afferent pathway, integrating center, and efferent pathway.
Components of the reflex arc:
Detectable change in the internal or external environment
Initiating factor for the reflex arc to be activated
Stimulus
Components of the reflex arc:
Detects the change
Receptor
Components of the reflex arc:
The pathway the signal travels between the receptor and the integrating center
Receptor -> Integrating center
Away from the receptor
Afferent pathway
Components of the reflex arc:
Receives signals from different receptors
Its output reflects the net effect of the total afferent input
Can be the brain but for the reflexes it is mostly in the spine
Integrating center
Components of the reflex arc:
The pathway along which information travels away from the integration center to the effector
Going to the effector
can have an multiple effectors
Efferent pathway
Communication systems use ________ that bind to receptors
signals
What types of signals are used in communication systems?
Hormones, neurotransmitters,
Types of Signals
Produced in and secreted from endocrine glands or in scattered cells that are distributed throughout another organ
Produced type of signalling that allows communication with other cells located at a different location
Hormones
Types of Signals
Chemical messengers that are released from the endings of neurons onto other neurons, muscle cells, or gland cells
Neurotransmitters
Types of Signals
Produced by the change in electric potential in the cells
Electrical stimulus
Participate not only in reflexes, but also in local responses, present in Neurotransmitters
Chemical Messengers
Three categories in communication signals
endocrine, paracrine, and autocrine signals
Three categories in communication signals
Signal reaches often-distant targets after transport in blood
Long distance cells
Endocrine
Three categories in communication signals
Endocrine
Paracrine
Autocrine
categories in communication signals
Signal reaches often-distant targets after transport in blood
Long distance cells
Endocrine
categories in communication signals
Signal reaches neighboring cells via the ISF
Proximal cells
Paracrine
categories in communication signals
Signal affects the cell that synthesized the signal
Affects itself
Autocrine
Diabetes Mechanism
Type 2
GLUT4 does not respond to insulin > Glucose remains in the blood > Brain thinks there is no glucose in the muscle cells > More glucose is produced > Diabetes
Normal Insulin Mechanism
Pancreas (β cells) > Insulin > Blood vessels > GLUT4 receptors in the muscle cells (gateway) > Glucose enters the muscle cells > Lowers glucose in the blood
Diabetes patients slim down and are always hungry because the muscle cells are deprived of glucose
true
drug that makes the body more sensitive to insulin which allows glucose to enter the muscle cells
Metformin
Insulin-dependent diabetes (Cannot produce insulin)
Type 1:
Insulin resistance diabetes (Cannot produce insulin)
Type 2:
What is the difference between endocrine, paracrine, and autocrine signals?
Endocrine signals reach distant targets via blood, paracrine signals reach neighboring cells, and autocrine signals affect the cell that synthesized them.
What is the mechanism of Type 2 diabetes?
GLUT4 does not respond to insulin, leading to high blood glucose levels.
A neuron, endocrine gland cell, and other cell types may all secrete the same chemical messenger
true
In some cases, a particular messenger may function as a neurotransmitter, as a hormone, or as a paracrine/autocrine substance
true
Example of chemical messenger that is Neurotransmitter and can also be a hormone
Norepinephrine
Neurotransmitter: Brain
Hormone: Adrenal glands
A characteristic that favors survival in specific environments and is irreversible.
adaptation
example of adaptation in humans
The Badjao can stay underwater longer because they have bigger spleen
Improved functioning of an already existing homeostatic system based on an environmental stress
Reversible
acclimatization
acclimatization example
Stopping for a while when going up Mount Everest to make the body acclimatize to the cold environment and high altitude
Many body functions are rhythmical changes
Biological Rhythms
Biological Rhythm that Cycles approximately once every 24h
Light can greatly affect
The lowering of the internal body temperature coincides with the time of lights off (10 PM - 6 AM)
Circadian rhythm
Add an anticipatory component to homeostatic control system and in effect are a feed-forward system operating without detectors
Biological Rhythms and Homeostasis
example Biological Rhythms and Homeostasis working together
Lunch time = salivates, stomach gurgles
are corrective responses
negative-feedback homeostatic responses
enable homeostatic mechanisms to be utilized immediately and automatically by activating them at times when a challenge is likely to occur
Biological rhythms
example of Biological rhythms enable homeostatic mechanisms to be utilized immediately example
Fight or flight response
How do biological rhythms relate to homeostasis?
They add an anticipatory component to homeostatic control systems.
What is heatstroke?
A condition resulting from prolonged exposure to high temperatures, leading to failure of the body’s temperature regulation.
What are the two major divisions of the nervous system?
Central Nervous System (CNS) and Peripheral Nervous System (PNS).
What are the main cell types in the nervous system?
Neurons and glial cells.
What are the types of glial cells in the CNS?
Astrocytes, microglia, ependymal cells, and oligodendrocytes.
What are the functional classes of neurons?
Interneurons, afferent neurons, and efferent neurons.
