Week 1 - Control of the Internal Environment: Homeostasis, Exercise & Adaptation

Question 1

Homeostasis

Answer 1

maintenance of a constant and “normal” internal environment

“It is the process by which we adapt and adjust to changes in our environment to maintain our functional integrity.”

Question 2

Hormesis

Answer 2

refers to a biological process in which low-to-moderate doses of a potentially harmful stress results in a beneficial adaptive effect

Question 3

Define steady state exercise and explain how it differs to homeostasis.

Answer 3

where physiological variables are unchanged (HR, VO2, Bp) but this doesn’t necessarily mean “normal”

its the balance between demands placed on the body and the body’s response to those demands

Question 4

What are the two biological control systems of the body?

Answer 4

1) Intracellular control systems: protein breakdown/synthesis, energy production, maintenance of stored nutrients (fats and carbs)

2) Organ systems: pulmonary and circulatory systems, replenish oxygen and remove carbon dioxide

Question 5

What are the 3 general components of a biological control system?

Answer 5

Receptor, control center, and effector.

Question 6

Describe the principles that underlie physiological control of variables.

Answer 6

Peripheral receptors/ sensors
- detect changes in the internal conditions of the body (peripheral organs and tissues) and send this afferent information to the brain ‘centres’ which processes and integrates this - (compares present value with desired value)

Control center
- send efferent information to effector organs/tissues either through nerves or hormones (or both) to negate (negative feedback) or to amplify (positive feedback) the change.

Effectors
- bring the internal environment back to normal (negative feedback) or amplify the changes (positive feedback).

Question 7

What are the two classes of biological control systems?

Answer 7

Negative and positive feedback

Question 8

Define negative feedback and provide an example.

Answer 8

where the response reverse the initial disturbance in homeostasis and restores normal values

Example: respiratory systems control of C02 concentration in extracellular fluid (blood)
- Increase in extracellular C02 triggers a receptor/sensor
- Sends afferent information to respiratory control center
- Respiratory muscle activated to increase breathing
- C02 concentration returns to normal

Other examples: blood pressure, heart rate, body temperature

Question 9

Positive feedback

Answer 9

Biological responses amplifies the original stimulus (change)

Example: Childbirth
- Initiation of childbirth stimulates receptors in cervix and sends message to the brain to release oxytocin from pituitary gland
- Oxytocin promotes increased uterine contractions

Other example: clotting of blood after cutting yourself

Question 10

What is the “Gain” of a biological control system?

Answer 10

the degree to which a control system maintains homeostasis - pulmonary and CV systems have large gains (thus more capable of maintaining homeostasis)

Question 11

Explain the regulation of body temperature in response to exercise.
What happens to effector organs/tissues if core body temperature drops?

Answer 11

Body temperature rises as exercise generates heat from working skeletal muscles.
Thermoreceptors detect this change in internal environment of the body and will send afferent information to the hypothalamus (control center).
The hypothalamus sends efferent information to effector organs and tissues which causes the increase in heat loss mechanisms (dilation of blood vessels and activating sweat gland secretion).
This negative feedback response limits the increase in core body temperature and creates a steady state where heat gain from exercise and heat loss is balanced.

If core body temperature drops, effectors constrict blood vessels and sweat glands are inactive.

Question 12

Adaptation

Answer 12

refers to a change in the structure and function of the cell or organ system (often in response to exercise) that results in an improved ability to maintain homeostasis during physiologically stressful conditions (exercise)

Question 13

Acclimation

Answer 13

adaption to environmental stresses (e.g. heat or hypoxic stress), which results in an improved function of existing homeostatic systems

Question 14

Define Hormesis.

What model can explain exercise-induced hormesis?

Answer 14

is the process in which a low-to-moderate dose of potentially harmful stress results in a beneficial adaptive response on the cell or organ system

Exercise-induced hormesis refers to the Inverted U shape model where there is an optimal intensity and duration of exercise stress to induce the greatest beneficial adaptive response - this varies between biological systems (CV, skeletal muscle) and people

Question 15

5 different types of cell signaling pathways

Answer 15

Intracrine signaling
Juxtracrine signaling
Autocrine signaling
Paracrine signaling
Endocrine signaling

Question 16

Define “Cell signaling” and explain why its important?

Answer 16

communication between cells using chemical messengers
this coordinates cellular activities and is important for maintaining homeostasis

Question 17

1) Chemical messengers inside cell triggers response
2) Chemical messengers passed between two connected cells
3) Chemical messengers acts on the same cell
4) Chemical messengers act on nearby cells
5) Chemical messengers (that are hormones) released into the blood and affect cells with specific receptors to the hormone

Paracrine, Endocrine, Intracrine, Juxtracrine, Autocrine

Answer 17

1) Intracrine
2) Juxtacrine
3) Autocrine
4) Paracrine
5) Endocrine

Question 18

What part of the body monitors our body temperature?

Answer 18

The Hypothalamus (temperature centre located here)

Question 19

Match the systems and the description explaining how they contribute during exercise

Systems: Blood, Renal, CNS, Integumentary, Musculo-skeletal, Respiratory, Cardiovascular, Endocrine, Alimentary

Supports circulation control and regulates metabolism.

Provides 02 and removes C02.

Provides movement under CNS control.

Pumps the blood through the circulation.

Water and nutrient intake.

Involved in heat loss from the body.

Controls Musculo-skeletal system, circulation and body temperature.

Conserves water; contributes to maintenance of body pH.

Carries gases, nutrients and waste products.

Answer 19

Endocrine: Supports circulation control and regulates metabolism.

Respiratory: Provides 02 and removes C02.

Musculo-skeletal: Provides movement under CNS control.

CV: Pumps the blood through the circulation.

Alimentary: Water and nutrient intake.

Integumentary: Involved in heat loss from the body.

CNS: Controls Musculo-skeletal system, circulation and body temperature.

Renal: Conserves water; contributes to maintenance of body pH.

Blood: Carries gases, nutrients and waste products.

Question 20

How do feedforward loops differ to regulatory feedback loops?

Answer 20

Feedforward loop results in physiological responses in anticipation of a change in a variable whereas regulatory feedback loops act to reduce (negative) or increase (positive) an actual change in a variable.