Animal Physiology Flashcards
How are physiological processes moderated? How are homeostatic processes in general controlled?
Positive and negative feedback. Homeostatic processes are controlled by negative feedback specifically.
What are the components of a feedback loop and what are their jobs?
- Receptor (monitor) –> monitors a controlled condition
- Control center (coordinating center) –> determines next action
- Effector (regulator)
–> receives directions from the control center
–> produces a response that changes the controlled condition
What is homeostasis?
The property of a system that regulates its internal environment and tends to maintain a stable, constant condition. It keeps the system within a set range with the use of negative feedback loops.
What are the two categories that organisms fit into when it comes to responding to changes?
- Osmoregulator
- Osmoconformer
Explain an osmoregulator. Give an example of one.
–> Can regulate the solute concentration of their body fluids above or below that of their external environment
–> Can control the osmolarity of tissues within narrow limits
–> Changes in environment have no effect or cause minimal fluctuations in internal solute concentration
Possible answers below!
–> Humans
–> Birds
Explain an osmoconformer. Give an example of one.
–> Actively or passively maintain an internal environment that is isosmotic to external environment
–> Solute concentration of body fluid is same as external medium in which organisms live
–> Cannot regulate the solutes of their body fluids at a concentration different to external medium
Possible answers below!
–> Sea stars
–> Molluscs
–> Marine crabs
–> Jellyfish
What is the function of a negative feedback loop?
It’s employed to minimize the change in the internal environment and maintain a steady state.
What is the function of a positive feedback loop?
It is employed to reinforce change and move away from a steady state. e.g. oxytocin levels during birth.
What are aspects of internal regulation?
–> blood pH
–> carbon dioxide concentration
–> blood glucose concentration
–> body temperature
–> water balance (osmoregulation)
What do the hypothalamus and pituitary act to coordinate?
The nervous system and the endocrine system.
What is an example of positive feedback?
The pressure of a child on the uterus releases oxytocin, and this release stimulates contractions, which stimulates the release of more oxytocin until birth is completed.
Outline how the stimulus of “increase in internal body temperature” impacts the body
Sensor: detected by skin receptors
Coordinator: hypothalamus
Effector (regulator): sweating + vasodilation
Response:
–> Sweating - secretion from sweat glands; excess body heat is converted to vapor
–> Vasodilation - widening vessels allows more heat to be lost
Outline how the stimulus of “decrease in internal body temperature” impacts the body
Sensor: detected by skin receptors
Coordinator: hypothalamus
Effector (regulator): shivering + vasoconstriction + thyroxine + arrector pili muscles
Response:
–> Shivering - increases heat production
–> Vasoconstriction - narrowing vessels increases pressure of flow to skin
–> Thyroxine - released by thyroid to increase metabolic activity in cells
–> Arrector pili muscles - contraction raises skin hairs to trap heat
Explain positive feedback with regard to oxytocin during childbirth.
- Pressure of child on uterus releases contractions.
- Oxytocin release stimulates contractions.
- Contractions stimulate the release of more oxytocin.
- Birth is completed and oxytocin release stops.
Does the pancreas have exocrine or endocrine functions?
Both! As an exocrine gland (associated with the duct), it secretes enzymes that help with digestion. As an endocrine gland (ductless), it secretes hormones that regulate blood sugar levels.
What are islets of Langerhans?
Pancreatic pits responsible for the secretion of insulin and glucagon
Which cells release insulin and what does its release result in? When is it typically released?
–> Released from beta cells of the pancreas.
–> Cause a decrease in blood glucose concentration.
–> Released when blood glucose levels are high (e.g. after eating)
Which cells release glucagon and what does its release result in? When is it typically released?
–> Released from the alpha cells of the pancreas
–> Causes an increase in blood glucose concentration
–> Released when blood glucose levels are low (e.g. after exercise)
How does insulin decrease blood sugar concentration?
–> It stimulates glycogen synthesis in the liver (glycogenesis)
–> It promotes glucose uptake by the liver and adipose tissue
–> It increases the rate of glucose breakdown (increases cell respiration rates)
Cells become permeable to glucose.
How does glucagon increase blood sugar concentration?
–> Stimulates glycogen breakdown in the liver (glycogenolysis)
–> Promotes glucose release by the liver and adipose tissue
–> Decreases the rate of glucose breakdown by reducing cell respiration rates
Glucose is released into the blood.
Describe insulin function in normal physiology.
- (Bind) Insulin binds to insulin receptors.
- (Open) Triggers the opening of glucose transporters in fat and muscle cells.
- (Remove) Allows glucose removal from the bloodstream.
Describe insulin failure in type I diabetes.
- Insulin is not produced by the beta cells in the pancreas.
- Glucose is not removed from the bloodstream, causing diabetes.
Describe insulin failure in type II diabetes.
- Prolonged overproduction of insulin causes desensitization of insulin receptors.
- Glucose is not removed from the bloodstream, causing diabetes.
List elements of type I diabetes mellitus. What is the treatment for it?
–> Juvenile onset
–> Unable to produce insulin
–> Often due to autoimmune disorders or viral infections that damage beta-pancreatic cells
–> Treatment involves:
- Insulin injection
- Pancreatic transplants
List elements of type 2 diabetes mellitus.
–> Adult onset (insulin resistance)
–> Insulin produced by body is unable to respond to it
–> Insulin receptors are ineffective at the cellular level (can’t bind to its receptor on the cell membrane or leads to no response)
–> Treatments include
- Diet, exercise, lifestyle changes
- Prescription medications for glucose control and/or insulin injections
What is the function of endocrine glands?
They secrete hormones into the blood; the hormones travel through the blood and bind to the target tissue.
What does it mean for steroid hormones to be lipophilic? Give an example of a steroid hormone.
They can freely diffuse across the plasma membrane of a cell.
Examples:
- estrogen
- progesterone
- testosterone
What does it mean for peptide hormones to be hydophilic / lipophobic? Give an example of a peptide hormone.
They cannot freely cross the plasma membranes.
Examples:
- Insulin
- Glucagon
- Leptin
- ADH and oxytocin
What is leptin? What produces it? What is its function?
–> Leptin is a hormone that regulates fat stores within the body.
–> It is produced by adipose cells.
–> Leptin binds to receptors located within the hypothalamus to inhibit appetite and reduce food intake.
–> Circulating leptin levels provide a measure of the body’s energy reserves.
What results in human obesity? What was discovered when attempts were made to use leptin supplements as a treatment for obesity?
–> Human obesity is a result of desensitized leptin receptors.
–> Leptin treatment had no positive effects on human obesity
–> Increased leptin levels caused skin irritations and other minor side effects
What are two elements that can cause leptin resistance?
–> Mutations - can cause failure in function of leptin receptors
–> Age - leptin resistance can develop with age
What is melatonin? What produces it? What is its function?
–> Melatonin is a hormone produced within the brain in response to changes in light.
–> It is produced by the pineal gland.
–> Its function is to control circadian rhythms, which are the body’s physiological responses to the 24 hour day-night cycle.
–> It becomes entrained over time to anticipate the onset of night and day.
–> It promotes activity in nocturnal animals and sleep in diurnal animals.
What facilitates the secretion or lack thereof of melatonin?
Light exposure to the retina, which is relayed to the suprachiasmatic nucleus.
During light exposure, the SCN inhibits the pineal gland. During periods of darkness, there is no inhibition.
What are circadian rhythms driven by?
An internal (endogenous) circadian clock.
How is melatonin involved with jet lag?
–> Pineal gland continues to secrete melatonin according to the old time zone.
–> The sleep schedule is not synchronised with the new time zone.
–> Taking melatonin near the sleep time of the new time zone can help the body respond quicker to the new day-night schedule.
What is thyroxin? What produces it? What is its function?
–> Thyroxin is a hormone secreted in response to signals initially derived from the hypothalamus.
–> It’s secreted by the thyroid gland.
–> It increases the basal metabolic rate by stimulating carbohydrate/lipid metabolism via the oxidation of glucose / fatty acids
–> It helps to control body temperature through its production of heat.
Name two effects of thyroxine.
Eight possible answers below!
–> Increased rate of utilization of foods for energy
–> Increased breathing rate to obtain oxygen / get rid of carbon dioxide
–> Increased rate of protein synthesis / catabolism
–> Increased number/size of mitochondria in body cells
–> Increased growth rate of children/adolescents
–> Growth/development of brain during fetal life / first years of post-natal life
–> Enhanced carbohydrate metabolism
–> Enhanced fat metabolism
Explain thyroxine deficiency. What are two symptoms of it?
Producing thyroxine requires four atoms of iodine. When iodine is not available in enough amounts to produce sufficient thyroxine, a goitre is developed (enlargement of the thyroid gland).
Five possible answers below!
–> Fatigue
–> Depression
–> Forgetfulness
–> Feeling cold
–> Constipation
–> Impaired brain development (in young children)
Explain negative feedback, and give an example of it.
–> A response that is the reverse of the change detected
–> a change is detected by a receptor and an effector is activated to induce an opposite effect, promoting equilibrium
Examples:
–> thermoregulation (if body temp changes, mechanisms to restore normal levels)
–> blood sugar regulation (insulin lowers high blood glucose, glucagon raises low blood glucose)
–> osmoregulation (ADH secreted to retain water when dehydrated, release inhibited when hydrated)
Explain positive feedback, and give an example of it.
–> A response that reinforces the change detected
–> A change is detected by a receptor and an effector is activated to induce the same effect, promoting further change
–> Change is amplified by feedback loop until the stimulus is removed
Examples:
–> Childbirth (stretching of uterine walls cause contractions that further stretch walls until birthing occurs)
–> Lactation (child feeding stimulates milk production which causes further feeding until baby stops feeding)
–> Ovulation (dominant follicle releases oestrogen which stimulates LH and FSH release to promote further follicular growth)
–> Blood clotting (platelets release clotting factors that cause more platelets to aggregate at the site of injury)
Name and describe the function of the eight different parts of the male reproductive system.
–> vas deferens (sperm duct) - carries sperm to penis during ejaculation
–> prostate gland - contributes alkaline fluid to the ejaculate, which helps to nourish the sperm.
–> urethra - delivers semen during ejaculation and urine during excretion
–> penis / erectile muscle - become erect to penetrate vagina during sexual intercourse, deliver sperm to top of vagina
–> seminal vesicle - produce fructose that provides sperm with a source of energy that helps with the sperm with a source of energy and helps with sperm motility
–> epididymis - functions in the transport and storage of the sperm cells that are produced in the testes
–> testis - produces millions of sperm every day, as well as testosterone
–> scrotum - protects and holds testes outside of the body to maintain an optimum temperature for sperm production
What does the male luteinizing hormone (LH) do? How is it secreted and released?
–> it promotes the production of testosterone by the interstitial cells
–> at puberty, the hypothalamus secretes the gonadotropin-releasing hormone (GnRH) which activates the pituitary gland to secrete/release FSH and LH
What are the two male sex hormones and where are they produced?
–> Androsterone and testosterone
–> They are produced in the interstitial cells (Leydig) of the testes
What does testosterone stimulate?
Spermatogenesis, the process by which spermatogonia divide and differentiate into mature sperm cells.
What is the effect of testosterone on the body during puberty?
- Pre-natal development of genitalia
- Development of male secondary sexual characteristics e.g.
–> Development of facial/body hair
–> Growth of larynx causes the lowering of voice
–> Strengthening of muscles
How does the Y chromosome factor into male development?
–> It includes a gene called the SRY gene
–> The SRY gene codes for a testis-determining factor (TDF) that causes embryonic gonads to form into testes
–> The testes secrete testosterone which causes the male genitalia to develop
