Module 7 Flashcards
what is homeostasis
maintenance of a dynamic equilibrium of internal environment
Steps to homeostasis regulation (5)
- stimulus produces change
- Receptor detects change
- info sent along afferent pathways to control center
- info sent alon efferent pathways to effector
- Response of effector feeds back to stimulus and returns homeostasis
What is the efferent response of putting your hand on a hot surface
removing hand
two systems in internal communication for animals
nervous system
endocrine system
Endocrine system description (4 points)
- secretes hormones transmitted to target cells via blood or intestinal fluid
- causes changes in metabolic activities in specific cells
- action is relatively slow
- effects are relatively prolonged
Hormone break down rate
slow
Nervous system description (4 points)
- transmits neurochemical impulses via neurotransmitters
- causes muscular contractions or gland secretion
- Action is very rapid
- effects are relatively brief
What do afferent neurons do
take sensory information to brain
what do efferent neurons do
take response information to desired muscle/gland (effector)
3 basic components that make up the endocrine system
- endocrine gland/cells
- hormone
- target organ
example of a stress response pathway
adrenal cortex–> cortisol–> many targets
2 divisions of endocrine system
neuroendocrine system
peripheral endocrine system
what is the neuroendocrine system
examples?
neurosecretory neurons with nerve terminals that release hormones into the blood or extracellular fluid
-hypothalamus, pituitary
What is the peripheral endocrine system
examples?
non neural tissue with no direct links to the nervous system.
- adrenal gland, ovaries, testes, thyroid gland
anterior pituitary system type and pathway
2 hormone system
because anterior is not brain tissue, neurons cant get to it directly, hypothalamus secretes hormone into the blood to tell the anterior pituitary to secrete/ inhibit a secondary hormone
posterior pituitary system type and pathway
1 hormone system
signals from the brain come direct to posterior as it is brain tissue, hormone secreted/inhibited
common anterior pituitary hormones
FSH
LH
growth hormone
Common posterior pituitary hormones
oxytocin
ADH
Positive feedback mechanisms
keep producing hormone
Negative feedback mechanism
hormone feeds back to brain to stop production
pancreas-insulin-muscles-glucose decreases to stop insulin production
4 categories of hormone activity
- stimulate the making of new proteins
- activate or inactivate enzymes
- open or close cell membrane channels
- cause cells to secrete/release something
Hormone cell relationship
hormones change cell activity but dont make them do something completely new
Cushing’s syndrome
too much cortisol
prolonged hormone exposure in aquaculture can cause
sex reversal
Berthold’s experiment on endocrinology
observed castration of male chickens (reduced size and aggression)
had 2 testes, no testes, and single testes animals: single testes grew biggest testes
trasplated testes reestablished blood flow not nerves
allowed for saying that testes play a role in development and blood supply plays a role in communication
hormone classifications factors (3)
type of signalling (autocrine: cell produces hormone, paracrine: acts on same organ, endocrine:hormone travels to act)
chemical structure (protein peptide, amine, steriod)
solubility (water vs fat soluble)
Examples of steroid hormones
solubility
stress hormones (cortisol), sex hormones (estradiol and testosterone)
lipid soluble
Example of peptide hormone
insulin
example of amino acid hormone
thyroid hormone
how do cells know to respond to certain hormones
specific receptors on target cells, most have more than one type of receptor
Possible receptor locations
on the cell membrane
inside cell (cytosol or nucleus)
How do water soluble hormones move?
leave cell through exocytosis
can transport themselves through blood
must go through endocytosis to get back into cell
How do fat soluble hormones move?
can easily cross cell membranes
need a transport protein to move through blood
Agonists
artificial hormone made to replicate a responce
antagonists
artificial substance that blockks hormone receptors to limit responces
impact of environmental chemicals on endocrine system
can act as antagonists or agonists and disrupt the system
crucial consideration when making agonists and antagonists
must have similar structure to fit the receptor
definition of sex levels
G chromosomal sex
G gonadal sex
G hormonal sex
P morphological sex
P behavioural sex
~gender identity
sex determination
the natural events in which an individual becomes male or female
Genetic sex determination
determined at fertilization by combination of genes
Environmental sex determination
determined after fertilization by temperature, population, size ect
Mammal genetic sex determination letter and ratio
1:1
Female: XX
Male: XY
bird, snake, butterfly, fish, and some amphibian sex determination letters and ratio
1:1
Female: ZW
Male: ZZ
Factors impacting environmental sex determination and examples
chance (how sea sponge lands on sea floor)
availability of resources (parasitic worm nutrient availability)
Social (clownfish hierarchy)
Temperature
Specific gene on Y chromosome that determines sex
sex determining region (SRY gene)
SRY gene regulates…
many genes that play into testes formation
sex differentiation
What produces hormones in the ovarian follicle
granulosa and theca cells produce estradiol to release into blood
what produces sex hormone in males
Leydig cells produce testosterone and releases into blood
Freemartinism
infertile female twin with masculinized behaviour and non functioning ovaries
how does the female twin get male hormone
amniotic fluid contains hormones at some points of development and migrates to female twin
Freemartin characteristics
- small ovaries that don’t produce estradiol
- male like characteristics
- infertile
- abnormal sex organs
- brain is masculinized
what is stress
an environmental change that disrupts homeostasis and threatens the animal
what is a stress response
physiological and behavioural responses that reestablish homeostasis
Acute stress
fight or flight
recovery follows quickly
chronic stress
constant and repeated
impairs immune/general health
2 stress systems in animals
sympathetic adrenal medullary system (SAM) short term
Hypothalamic pituitary adrenal system (HPA) chronic
How does the SAM work
brain perceives stressor
signals sent to adrenal gland to release adrenaline (epinephrine)
How does the HAP work
hypothalamus releases hormone in response to chronic stress
pituitary signalled to release hormone
adrenal signalled to produce cortisol
adrenal gland located…
on top of the kidney
adrenal gland setup
outer cortex layer
inner medulla
stress response pathway
- perceive the stimuli
- autonomic response (adrenaline/epinephrine release, inhibit unnecessary functions)
- endocrine response (cortisol release, glucose production, protein breakdown
- exhaustion
physiological responses to stress
catecholamines (adrenaline/epinephrine)
cortisol
Behavioural responses to stress
active (fight or flight)
passive (hiding, abnormal behaviour ect)
Behavioural stress response examples
vocalization
restlessness
isolation
Physiological stress responses
examples
high HR and BP
low reproductive hormones
Performance stress response examples
low milk yield
low body condition
low fertility
Immune stress response examples
lower white blood cells
higher disease
2 ways to measure stress in animals
behavioral assessment
hormonal analysis
behavioural assessment points
species specific behaviours
learned behaviours
dependent on many factors
how hormone measurements are indicators of stress
stress secretes hormone into blood stream and can move to other tissues
measuring cortisol through blood
gold standard
measures total (free and bound)
stressful and invasive process-may increase stress hormone in blood
measuring corisol through saliva
can detect cortisol level changes within seconds-minutes
done by collecting drool with absorbent material
less invasive
benefits of measuring cortisol through feces
useful for livestock and marine as you dont have to catch the animal
not as accurate for wildlife as you dont know how recent the sample is
measuring cortisol through urine
only free cortisol is measured as bound is filtered by kidney
sampling needs to be consistent due to circadian patterns
can be difficult to collect
measuring cortisol through hair
can provide timeline of stress
stable sample unlike other methods (dont need to freeze or test right away)
Toxicology
the study of adverse effects of toxicants on living things
Toxicant
any agent capable of producing adverse effects on living things
factors influencing toxicity
life stage at exposure
route of exposure
length of exposure
most susceptible life stage to toxicants
why
development (embryo and early infancy)
often irreversible effects
differentiation of organs and cell types is happening
what does route of toxicant exposure change
the dose
exposure is what is taken in, dose is what gets to the organ
ingestion is the most hazardous as it is direct route to the liver
why is it important to know species differences in response to toxicants
- diagnosis
-treatment
-drug development
examples of where selective toxicity is a benefit
antibiotics (killing what’s wanted not eveything)
Reasons for species variability to toxicants
route of exposure (water vs air, fish vs bird)
organ system differences or capacities
species size
why is toxicity testing done
to determine the maximum safe dose tolerance
history of toxicity testing
began in early 20th century
follows standardized guidelines to ensure global results can be compared
alternatives to using animals for toxicity testing
simulators
in vitro cells/tissues
advantages to live toxicity testing
higher accuracy
effects on each organ can be measured
can measure behavioural changes
disadvantages to live toxicity testing
species specificity
ethic concerns
animals bred as lab models are inbred and can have altered results
high money and resource requirement
advantages to in vitro toxicity testing
cell type specific
non invasive
less variability
disadvantage to in vitro toxicity testing
mass miss biological variabilities
