Chapter 9: Homeostasis Flashcards
1
Q
What is homeostasis
A
- it is the maintenance of a constant internal environment
2
Q
Why does the body need to regulate body temoerature
A
- enzymes can only work within a certain range of temperatures
- if the body’s temperature is higher than the specific temperature, the enzymes will denature
- if too low, the enzymes will be inactive
3
Q
Why does the body need to regulate water potential in blood?
A
- if water potential in blood is higher than cell, then water will move to cells
- cells will expand, swell and burst
- if water potential in blood is lower then cells, water will move out of cell.
- cell will shrink and crenate and die
4
Q
Why does the body need to regulate blood glucose concentration
A
- cells in body need glucose to undergo cellular respiration and release energy to perform their vital activities
- it is dangerous if blood glucose levels drop below normal levels for too long
5
Q
Negative feedback loop
A
- stimulus in body (change in internal environment)
- receptors detect stimulus
- nerve impulses are sent to control centre
- corrective mechanism occurs
- condition returns to normal
6
Q
What is negative feedback
A
- the sequence of events that take place in the body to restore the system back to its original state
7
Q
What happens when water potential in blood rises above normal
A
- water potential in blood increase due to large intake of water
- hypothalamus stimulated
- less ADH released by pituitary gland into bloodstream
- less ADH transported to kidneys
- cells in walls of collecting duct becomes less permeable to water
- less water reabsorbed into blood stream
- more water excreted
- urine more diluted
- more urine is produced
8
Q
What happens when water potential in blood drops below normal
A
- water potential in blood drops due to sweat/dehydration
- hypothalamus stimulated
- more ADH is released by the pituitary gland into blood stream
- more ADH transported to kidneys
- cells in walls of collecting duct becomes more permeable to water
- more water reabsorbed into the blood stream
- less water excreted
- urine is more concentrated
- less urine produced
9
Q
Hormone
A
- a chemical substance produced in minute quantities by an endocrine gland. it is transported in the bloodstream to target organs where it exerts its effects
10
Q
How do hormones control human body
A
- hormones can influence the growth, development & activity of an organism
- they are chemical messengers that help the various parts of the body to respond, develop and work tgt smoothly
- they are produced by endocrinologists glands & secreted directly into the bloodstream
- glands with ducts are called exocrine gland
- the pancreas is both an endocrine and exocrine gland
11
Q
Endocrine gland (ductless glands)
A
Hypothalamus: regulates secretion of some hormones
Pituitary gland: plays important role as a “controller”. it secretes a number of hormones, which control the secretion of hormones of several other endocrine glands. is is known for being the “master gland”. It also secretes ADH
Pancreas: Islets of Langerhans in pancreas secrete insulin and glucagon
Ovary: secretes oestrogen and progestrone
Testis: secretes testosterone
12
Q
What happens when normal amount of insulin is secreted
A
- it decreases blood glucose concentration
- makes cell surface membranes more permeable to glucose, allowing more glucose to diffuse into the liver and muscle cells
- stimulates liver and muscle cells to convert excess glucose into glycogen for storage
- increases use of glucose for respiration
13
Q
What happens when lack of insuline is secreted
A
- increases blood concentration
- glucose cannot be stored or utilised by tissue cells
- hence blood concentration rises, some glucose is last in urine
- gives rise to diabetes
- muscle cells have no reserve of glycogen, body grows weak and continuously lose weight
14
Q
What happens when too much insuline is secreted
A
- abnormal decrease in blood glucose concentration
- low blood glucose concentration results in condition called shock
- seizures or fits, collapsing or passing out may follow
15
Q
Effects of glucagon
A
- islets of langerhans increase secretion of glucagon when concentration of blood glucose is below normal
- main target organ is liver
- increases blood glucose concentration
- stimulates conversion of glycogen into glucose
- stimulates conversion of fats and amino acids into glucose
16
Q
What happens when blood glucose concentration is above normal
A
- blood glucose concentration rises above normal
- islets of langerhans in pancreas are stimulated
- islets of langerhans secretes more insulin into blood stream
- blood transports insulin to the liver and muscles
- insulin increases permeability of cell membrane to glucose
- glucose is absorbed more readily by cell
- insulin increases rate of respiration
- insulin causes the live and muscles to covert excess glucose to glycogen, which is stored tin liver & muscles
- blood glucose concentration decreases
- provides negative feedback to receptor to reduce insulin production
17
Q
What happens when blood glucose concentration falls below normal
A
- blood glucose concentration falls below normal
- islets of langerhans in pancreas are stimulated
- islets of langerhans secretes more glucagon into blood stream
- blood transports glucagon to liver and muscles
- glucagon causes the conversion of glycogen back to glucose
- from liver, glucose enters the bloodstream
- blood glucose concentration increases
- provides negative feedback to receptor to reduce glucagon production
18
Q
What is diabetes mellitus
A
- a disease in which the body is unable to control its blood glucose concentration in order for it to remain within normal limits
- blood glucose concentration can rise to a level that exceeds kidney’s ability to complete reabsorb all the glucose
- glucose that is not reabsorbed is excreted via urine
- type 1 diabetes develops early in a person’s life where the islets of langerhans are unable to produce are secrete enough insuline. it is inherited
- type 2 occurs later in life and develops when the target cells no longer respond well to insulin
19
Q
Signs of diabetes
A
- persistently high blood glucose levels
- presence of glucose in urine
- healing of wounds is slow and difficult
- frequent urination
- weight loss
- thirst
20
Q
How can diabetes be treated
A
- diabetics have to measure their blood glucose concentrations and test their urine regularly
- they must also watch their diet, making sure that they do not take in too much carbohydrates
- people with type 1 diabetes have to inject insulin regularly into the fat tissue under the skin
- if they use too much insulin, exercise too much or eat too little, their blood glucose concentration can drop too low and they may go into a coma
- they need to be ready with a supply of sugary foods
- they should also take medication that increases uptake of glucose from blood stream into cells
21
Q
Risk factors of type 2 diabetes
A
- when liver and muscle cells do not respond well to insulin
- risk factors include obesity, age, family history, blood lipid levels (if you have high levels of bad cholesterol & low levels of good cholesterol), and sedentary lifestyle
22
Q
How to avoid type 2 diabetes
A
- eat healthily
- engage in more active physical activity
- avoid being inactive for long periods of time
- maintain a healthy body weight based on age and height
23
Q
Structures in skin involved in temperature reulation
A
- Arteriole
- Blood capillaries
- Hair follicle
- Hair
- Hair erector muscle
- Sweat gland
- sweat duct
- sweat pore
- nerve endings (thermoreceptors)
- adipose tissues
24
Q
Blood vessels under skin surface
A
- dilatation and constriction of arterioles are caused by the contraction and relaxation of muscles in arteriole walls
- contraction and dilation of arterioles help regulate body temperature
- when arterioles vasodilation, more blood is sent to the blood capillaries in the skin. the skin becomes red because of the numerous blood vessels in the skin dialate
- vasoconstriction of arterioles reduces amount of blood flowing through capillaries in skin & cause us to be pale
25
Q
Sweat glands
A
- secreted sweat flows through sweat duct to sweat pore that opens at skin surface
- secreted sweat consist of water, dissolved salts and small amounts of urea
- sweat is secreted continuously & amount of sweat produced varies on extreme internal environmental conditions
- sweat helps regulate body temperature
26
Q
Sensory receptors
A
- enables body to detect changes in envrionment
- nerve ending in skin is sense receptors
- enables you to sense pain, pressure & temperature changes in external environment
- thermorecptors detect temperature changes
27
Q
How does the body gain heat
A
- heat is released within body as result of metabolic activities like cellular respiration
- high levels of cellular respiration take place in muscles and liver. large amounts of heat is released in these organs and distributed to the rest of the body via bloodstream
- can also gain heat through vigorous muscular activities, consumption of hot food and being in warm environments
28
Q
How does the body lose heat
A
- through the skin
- by evaporation of water in sweat at the surface of the skin
- in faeces and urine
- in the air that is exhaled
- amount of blood flowing through skin capillaries affects heat loss through the skin surface
29
Q
What happens when body temperature rises above normal?
A
- thermoreceptors in skin are stimulated. impulses are transmitted to the hypothalamus
- arterioles in skin vasodilate, allowing more blood to flow through blood capillaries in skin, so more heat is lost through skin
- sweat glands become more active and produces more sweat. as more water in sweat evaporates from surface of skin, more heat is lost from body
- metabolic rate decreases, reducing amount of heat released
- body temp decreases
- body temp returns to normal
30
Q
What happens when body temperature drops below normal?
A
- thermoreceptors in skin are stimulated. impulses are sent to hypothalamus
- arterioles in skin vasoconstrict, allowing less blood to flow through blood capillaries in skin
- sweat glands become less active and will secrete less sweat. since less sweat evaporate from surface of skin, less heat is lost from the body
- metabolic rate increases and increases amount of heat
- if above is not enough, shivering occurs, increasing amount of heat released
