Lecture 2

Question 1

Why do we need homeostasis?

Answer 1

Immediate survival
Health and well-being
Reproductive capability

Question 2

What happens when you intake too much salt?

Answer 2

Plasma osmolality increases
Water sucked out of cells
Person gets thirsty and drinks water to compensate
Plasma osmolality maintained but blood volume increases
BP increases

Question 3

What is feed-forward?

Answer 3

Anticipation of a change is detected by the body and a response is brought about that change before it can be detected by negative feedback sensors

Question 4

What are the types of negative feedback control centres?

Answer 4

Neuronal and hormonal

Question 5

What are the hypothalamus, pons and medulla are essential for?

Answer 5

Temperature control
BP control
Breathing control
Osmolality control

Question 6

What happens when temperature drops?

Answer 6

• Drop in temperature is sensed by hypothalamus
• Neurons along the afferent pathway send signals to somewhere else in the hypothalamus which compares with set point
• Hypothalamus then sends signals along the efferent pathway to the effectors (skin blood vessels and muscle)
• Shivering to lead to heat production and reduced blood flow to skin to prevent heat loss from the body

Question 7

What is below the hypothalamus?

Answer 7

Pons
Medulla
Anterior and posterior pituitary

Question 8

What are the tyrosine derrivatives?

Answer 8

Thyroxine (thyroid gland)
Adrenaline (adrenal gland)

Question 9

What hormones are derived from cholesterol?

Answer 9

Estradiol
Testosterone
Cortisol
Aldosterone

Question 10

What type of hormones have intracellular receptors?

Answer 10

Steroid and thyroid hormones
Long-lived, slow
Trigger gene transcription

Question 11

What type of hormones have extracellular receptors?

Answer 11

Peptides, proteins, glycoprotein, catecholamines
Fast, short-lived
Trigger secondary responses

Question 12

What is paracrine homeostatic control?

Answer 12

Negative feedback that occurs locally in a cell/tissue

Question 13

Give me an example of positive feedback?

Answer 13

• Progesterone and oestrogen balance is shifted during pregnancy
• This electrically excites the uterus, leading to uterine contraction
• As the foetus grows, it pushes pressure on the cervix
• Hypothalamus detects this pressure and causes oxytocin secretion from the pituitary gland
• Oxytocin further stimulates excitability of the uterus, this keeps happening until the baby is born

Question 14

What is the hormone released by the pituitary gland during pregnancy? (positive feedback)

Answer 14

Oxytocin