Homeostasis and Control Systems

Question 1

Definition of homeostasis

Answer 1

maintainance of a dynamic constancy in internal environment of the body

Question 2

Equilibrium

Answer 2

particular variable is not changing and no input of energy needed to maintain constancy

Question 3

Steady state

Answer 3

particular variable is not changing, but energy must be added continuously to maintain constant condition

Question 4

Characteristics of homeostasis

Answer 4

• continuous process
• various systems contribute and may collaborate with each other

Question 5

Homeostatic responses

Answer 5

can be local or systemic

Question 6

Meaning of reflex

Answer 6

a cycle of events that is specific, involuntary, unpremeditated and unlearned built-in response mechanism to stimulus

Question 7

Components of reflex arc

Answer 7

stimulus
receptor
integrating centre
effector
response

Question 8

Stimulus

Answer 8

detectable change in controlled condition

Question 9

Receptor

Answer 9

part of cells that respond to changes in controlled condition and sends input to integrating centre

Question 10

Afferent pathway

Answer 10

between receptor and integrating centre

Question 11

Integrating centre (brain)

Answer 11

receives signals from receptors and decide on appropriate responses

Question 12

Effector organs

Answer 12

cells or tissues whose activity constitute to overall response of system

Question 13

Nervous reflexes effectors

Answer 13

muscle, glands, some adipose tissue

Question 14

Endocrine reflexes effectors

Answer 14

amy cells that have proper signal receptor

Question 15

Efferent pathway

Answer 15

between brain and effector

Question 16

Negative feedback system

Answer 16

• increase or decreasecin variable being regulated
• opposite to direction of original changes
• stabilize the physiological variable to maintain homeostasis

Question 17

Regulation of blood glucose

Answer 17

• simple endocrine reflex (no afferent pathway)
• receptor : glucose transporter
• high blood glucose : B-cell secretes insulin and store glucose in muscle and adipocytes
• low blood glucose : a-cell secretes glucagon and store glucose in glycogen form in liver

Question 18

Regulation of blood pressure

Answer 18

receptor : baroreceptors
effector : heart

Question 19

Positive feedback system

Answer 19

• reinforces stimulus (make it go higher)
• non homeostatic

Question 20

Control of uterine contractions

Answer 20

release of oxytocin by brain causes the cervix to contracts more forcefully until baby is out

Question 21

Blood clotting

Answer 21

• when damage to blood, prothrombin change to thrombin
• thrombin catalyzes conversion fibrinogen to fibrin
• form a meshwork running in all direction and entrapping blood cells, platelets, plasma

Question 22

Processes related to homeostasis

Answer 22

acclimatization
biological rhythms
local homeostatic responses

Question 23

Acclimatization

Answer 23

ability of physiological system to adapt to extreme stress in a given sets of environmental condition

Question 24

Circadian rhythms

Answer 24

• daily biological rhythms, cycles once every 24 hours
• “anticipatory” component to predictable environmental variable

Question 25

Local homeostatic responses

Answer 25

a cell or tissue senses a change in its immediate vicinity and responds to counteract changes

Question 26

Homeostatic imbalances

Answer 26

moderate : disorder / disease severe : death

Question 27

Disorder

Answer 27

abnormality of functions

Question 28

Disease

Answer 28

illness characterized by recognisablevset of signs and symptoms

Question 29

Signs

Answer 29

can observe anatomically

Question 30

Symptoms

Answer 30

subjective changes not apparent to observer

Question 31

Necrosis

Answer 31

disruption in plasma membrane

Question 32

Apoptosis

Answer 32

cell proliferation = cell death

Question 33

Abnormal inhibition of apoptosis

Answer 33

cause cancer

Question 34

Excessive rate of apoptosis

Answer 34

cause oesteoporosis (degenerative bone disease)

Question 35

Cellular communicationsp in homeostatic systems

Answer 35

local communication long distance communication chemical signals target cells signal transduction

Question 36

Neural communication

Answer 36

combination of electrical and chemical signals

Question 37

Endocrine communication

Answer 37

involved hormones (chemical signals that are secreted into interstitial fluids)

Question 38

Local communication

Answer 38

autocrines : acts upon cells that secreted it paracrine : secreted hormones that acts on neighbouring cells

Question 39

Eicosanoids

Answer 39

- derived from polyunsaturated fatty acids (arachidonic acid) in plasma membrane phospholipids - acts as second messenger - pathway : cyclooxygenase > cyclic endoperoxides, prostaglandins, tromboxanes - other pathway : lipooxygenase > leukotrienes (certain types of white blood cells)