homeostasis

Question 1

what is homeostasis?

Answer 1

it is the maintenance of a constant internal enviornment within a living organism

Question 2

what is the importance of homeostasis?

Answer 2

A stable internal environment allows an organism to be

independent of changes in the external environment.

Question 3

why do enzymes require an optimum body temperature?

Answer 3

if the temperature is below the optimum, enzymes becomes inactivated. if it is exceeds the optimum, it becomes denatured.

Question 4

why must tissue fliud be kept at constant pH and water potential?

Answer 4

if there are drastic changes in the pH, the enzyme activities and cellular reactions will be affected, harming the body. The composition of tissue fluid has to be
maintained as body cells will either shrink or burst in solutions with water potentials different from that in the cytoplasm.

Question 5

sequence in a homeostasis process?

Answer 5

stimulus> receptor> integrator> effector> response

Question 6

what is negative feedback?

Answer 6

self-regulatory mechanism which feedbacks to the receptor when the set-point/norm is reached. The new information received by the recpetor is transferred to the control center which prevents further corrective action by the effector. System is then fully restored to its original state

Question 7

which systems are involved in the coodination of a homeostatic response?

Answer 7

endocrine and nervous system

Question 8

what is the endocrine gland?

Answer 8

it is a specific type of gland which produces hormones

Question 9

what is a gland?

Answer 9

an organ which produces a secretion

Question 10

what is the difference between exocrine and endocrine glands?

Answer 10

• exocrine produces secretions which travel through ducts to where it is needed (enzymes, proteins..)
• endocrine produces secretions directly into the bloodstream.

Question 11

what is a hormone?

Answer 11

it is a specialised signal molecule that is secreted by endocrine glands. they are transported to target organs via bloodstream and bind to cells with receptors. it is destroyed in the liver and excreted by kidneys

Question 12

what types of hormones are there?

Answer 12

peptide hormone (made up of protein) and steroid hormone (made up of lipids)

Question 13

what role do hormones play in homeostasis?

Answer 13

response to a stimuli may be specific as only relevant effectors should be stimulated. there are specific receptors on target cells that have binding sites which are complementary to that of the hormone. hence, the specific action of a hormone ensures that only target cells are activated.

Question 14

what does insulin do?

Answer 14

1. increases permability of cell surface membrane of most body cells to glucose, increases uptake of glucose from bloodstream
2. increase oxidation of glucose into carbon dioxide and water during cellular respiration
3. increases synthesis of glycogen
4. increases synthesis of lipids from glucose in liver
5. increase synthesis of proteins from amino acids

Question 15

what happens when blood glucose concentration rises above the normal level?

Answer 15

1. stimulus: blood glucose concentration rises above the norm
2. Islets of Langerhans in pancreas is stimulated and secretes more insulin into the bloodstream to the liver and muscle cells
3. insulin increases the permability of cells to glucose so liver and muscles take in more glucose. Liver converts more glucose into glycogen.
4. concentration of blood glucose decreases and insulin production falls
5. concentration of blood glucose returns to normal

Question 16

what happens when blood glucose concentration drops below the normal level?

Answer 16

1. stimulus: blood glucose concentration falls below the norm
2. stimulates Islets of Langerhans in pancreas secretes more glucagon into the bloodstream and transported to the liver
3. glycogen in liver is converted to glucose which is released into the bloodstream
4. blood glucose concentration increases, and glucagon production decreases
5. blood glucose concentration returns to set-point

Question 17

what is osmoregualtion?

Answer 17

it is the homeostatic process by which by an organism controls the water content in their body

Question 18

what happens when water potential of blood increases above the norm?

Answer 18

1. stimulus: water potential of blood increases above set-point
2. Hypothalamus, which contains osmoreceptors, in the brain detects the increase and stimulates the pituitary glands to secrete less anti-diuretic hormones into the bloodstream
3. this decreases the permeability to water of the distal convoluted tubule and collecting duct less ADH are binded to their cells
4. less water is reabsorbed by these parts of the kidneys and more water is excreted, urine becomes more dilute
5. water potential of the blood decreases and negative feedback is sent to the hypothalamus
6. water potential returns to normal

Question 19

what does ADH do?

Answer 19

controls the constriction of blood vessels. more constricted> higher blood pressure

Question 20

what are the main parts of the skin?

Answer 20

1. epidermis
2. dermis
3. subcutaneous

Question 21

what is the epidermis and is it made of?

Answer 21

it is the outermost layer.

it consists of the cornified layer, granular layer and malpighian layer

Question 22

what is the cornified layer?

Answer 22

it forms the outermost surface of the skin and consists of dead dry cells with keratin deposits. Dead cells are continually shed from the skin surface

Question 23

what is the granular layer?

Answer 23

it is the middle layer of the epidermis. It consists of living cells moving upwards and these cells eventually dry up and die to form the cornified layer.

Question 24

what is the malpighian layer?

Answer 24

it is the innermost layer of the epidermis. it consists of actively-dividing cells which contains melanin

Question 25

where is the dermis?

Answer 25

it is found directly below the malpighian layer and its upper part is thrown into ridges/papillae

Question 26

what is in the dermis?

Answer 26

it has numerous blood capillaries supplying blood to the skin.
hairs are also embedded within the dermis. the malpighian layer sinks into the dermis to form a hair follicle

Question 27

what happens when blood vessels dilate and constrict?

Answer 27

when the blood vessels dilate, more blood flows to the skin surface (vasodilation). the opposite happens when the blood vessels constrict (vasoconstriction)

Question 28

what is hair papilla?

Answer 28

Hair papilla is found at the base of the hair follicle and consists of blood capillaries and nerves.

Question 29

what do hair erector muscles do?

Answer 29

Hair erector muscles contract and cause hairs to stand,

resulting in appearance of goose pimples.

Question 30

what are sebaceous glands?

Answer 30

they open into each hair follicle and produces sebum which lubricates the hair, keeps the skin soft and prevents microbial growth

Question 31

what is a sweat gland?

Answer 31

it is a coiled tube formed by the downgrowth of epidermis, it is richly surrounded by blood capillaries and secretes sweat whcih flows through the sweat duct and sweat pore to the skin surface

Question 32

what is the subcutaneous?

Answer 32

it contains adipose cells which store fats below the dermis

Question 33

how is heat lost by the body?

Answer 33

1. from the skin surface via conduction, convection and radiation
2. evaporation of sweat
3. expired air from the lungs
4. faeces and urine

Question 34

what happens when the body temperature increases?

Answer 34

1. stimulus: body temperature rises above norm
2. temperature receptors in the skin and hypothalamus detects the change
3. corrective mechanism is stimulated
4. increased heat loss and reduced heat production
5. body temperature decreases to norm

Question 35

what is the corrective mechanism that enables heat loss?

Answer 35

1. vasodilation of arterioles near the skin surface
   - arterioles dilate, shunt vessels constrict, more blood flows into capillaries near the skin, allowing heat to be lost through CCR.
2. more active sweat glands will increase sweat production, when more sweat is produced, more latent heat is removed from the body when sweat evaporates
3. reduce metabolic rate, rate of metabolic activites decrease, less heat produced by the body

Question 36

what is the corrective mechanism that prevents heat loss?

Answer 36

1. hair erector muscles contract, causing the hair to stand, trapping an insulating layer of warm air over the skin
2. increase metabolic rate, increase heat production
3. shivering is the reflex contraction of body muscles to generate body heat