HOMEOSTASIS

Question 1

Define homeostasis.

Answer 1

The state of steady internal physical and chemical conditions maintained by living systems.

Question 2

What systems are used to maintain homeostasis and what are human examples of homeostasis?

Answer 2

Regulating:
- Body temperature
- pH levels
- Water and solute balance
- Blood glucose levels
- Blood oxygen levels
- Blood carbon dioxide levels

Nervous and endocrine body systems are responsible.

Question 3

Describe the stimulus response pathway.

Answer 3

• A stimulus is triggered by sensory receptors.
• These receptors pass a nervous message to a control center.
• The control center triggers a response by activating an effector.
• The effector removes the stimulus or initiates an action to negate the stimulus and restore the status quo.

Question 5

Define the 6 different types of chemical receptors.

Answer 5

Photoreceptors - detect light
Chemoreceptors - detect taste
Thermoreceptors - detect temperature
Baroreceptors - detect blood pressure
Osmoreceptors - detect osmolarity
Hair cells - detect sound (type of baroreceptor).

Question 6

Compare the action of the nervous and hormonal system.

Answer 6

Pathway:
- direct via nerve cells, whereas endocrine is indirect via the blood.

Message:
- nervous is electrochemical impulses whilst endocrine is chemical

Site of action:
- nervous is localized whereas endocrine is widespread

Speed:
- nervous is fast whereas endocrine is slow

Duration:
- nervous is short whereas endocrine is long (except for adrenaline).

Question 7

Define negative feedback.

Answer 7

A response where the system output is greater than the input from the stimulus, inhibiting the stimulus.

Question 8

How does homeostasis in humans rely on both the nervous and endocrine system?

Answer 8

• Receptors detect the stimulus, hormones are the response triggered by effectors to remove the status quo.

Question 9

What is an action potential?

Answer 9

A nerve impulse.

Question 10

Compare the structure of sensory, inter, and motor neurons.

Answer 10

Sensory neuron:
- small cell body along axon
- myelin sheath

Interneuron:
- reduced cell body near dendrites
- no myelin sheath

Motor neuron:
- large cell body near dendrites
- myelin sheath

Question 11

Compare the function of sensory, inter, and motor neurons.

Answer 11

Sensory neurons:
- Are part of the peripheral nervous system
- Carry action potentials from sensory receptor to the CNS

Interneurons:
- Are part of the central nervous system.
- Receive information from sensory neurons and pass action potentials to motor neurons.

Motor neurons:
- Part of the peripheral nervous system.
- Receive information from interneurons and pass rigger effectors.

Question 12

Difference between water soluble hormones and steroid hormones acting upon receptors.

Answer 12

• Water soluble hormones act upon receptors in the cell membrane.
• Steroid hormones act upon receptors in the cytoplasm.

Question 13

Differences between steroid hormones and water-soluble hormones.

Answer 13

Steroid hormones:
- Derived from cholesterol
- Are fat soluble
- Are associated with adrenal medulla or sex glands
- Hormones are ketones or alcohols.

Hormones derived from amino acids:
- Amine
- Peptide
- Protein/glyprotein

Question 14

Define a hormone.

Answer 14

• Chemicals secreted by endocrine glands located around the body.
• A chemical messenger

Question 15

Describe the difference between endotherms and ectotherms.

Answer 15

• Endotherms (humans) produce their own body temperature through metabolic processes.
• Ectotherms require heat from external sources.