hormones & homeostasis

Question 1

define hormone

Answer 1

a chemical substance, produced by a gland
and carried by the blood,
which alters the activity of
one or more specific target organs

Question 2

What are the glands that produce hormones called?

Answer 2

Endocrine glands; they make up the endocrine syste.

Question 3

What gland secretes the following hormones?
Adrenaline, Insulin, Glucagon, Testosterone, Oestrogen

Answer 3

Adrenal gland
* Adrenaline

Pancreas
* Insulin
* Glucagon

Testis
* Testosterone

Ovary
* Oestrogen

Question 4

Define adrenaline and its effects

Answer 4

• Hormone secreted by the 2 adrenal glands, which prepares body for fight or flight situations.

Effects:
* Increased breathing rate (allows more oxygen into body)
* Increased heart rate (to deliver more oxygen around body)
* Increased pupil diameter (allows more light to enter eye)

Causes heart muscles to contract more frequently w more force, so heart rate increases.
This increases the blood flow to muscles, so cells receive more oxygen & glucose for increased respiration.
* Increased breathing rate & oxygen -> increased supply of oxygen & glucose (breakdown of glycogen stores to release glucose) to cells -> increases metabolic activity.

Question 5

Compare between nervous & endocrine system

Answer 5

Nervous system
* made up neurones
* info transmitted in the form of electrical impulses
* impulses transmitted along neurones
* impulses travel very quickly; action is very fast
* effect of a nerve impulse lasts for very short time

Endocrine system
* made up of glands
* info transmitted in the form of chemicals called hormones
* chemicals carried in the blood plasma
* chemicals travel more slowly, action is slower.
* effect of hormone may last onger

Question 6

define homeostasis

Answer 6

the maintenance of a constant internal environment.

Question 7

1. How homeostatic control is achieved?
2. What’s negative feedback?

Answer 7

1. Negative feedback mechanism
   Keep internal environment within narrow limits around a set point.
2. Body’s response to internal conditions deviate from the ideal set point.
   Body returns conditions to the setpoint.

Question 8

Control of blood glucose concentration is by?

Answer 8

Hormones secreted by the pancreas.

Question 9

What happens when blood glucose conc high?

Answer 9

• Pancreas secretes insulin
  causing -
• Liver absorbs glucose
  liver can use it in respiration, breaking it down to CO2+H2O
  to make insoluble glycogen, stored in liver.

Question 10

What happens when blood glucose conc low?

Answer 10

• Pancreas secretes glucagon
• Glycogen in liver converted to glucose & released into blood, blood glucose conc increases.

Question 11

What do the 2 glands in pancreas produce?

Answer 11

One of them is with a duct which makes pancreatic juice, flows along duodenum.
Scattered throughout pancreas are islet cells; they make the hormones insulin & glucagon.

Question 12

symptoms of type 1 diabetes

Answer 12

fatigue, thirst, increased urination, blurred vision, heart & breathing increases, slow wound healing, weight loss

Question 13

treatment for type 1 diabetes

Answer 13

Diet & lifestyle
* Healthy eating, monitoring carbohydrates, avoiding sugary drinks, foods.
* Regular meals
* Regular blood glucose tests (using a sensor, testing urine for glucose, using dipstick)

Insulin injections
* Insulin injections, just before a meal or after a meal.

Question 14

advantages of controlling body temp

Answer 14

enzymes work efficiently at 37c
metabolic rates kept constant
animals can be active in cold weather.

Question 15

structure & function of human skin
(top layer of skin, sweat glands, arterioles, hair, receptors, fat cells)

Answer 15

Top layer of skin
* covered w layer of dead cells

sweat glands
* secretes sweat which evaporates from top of skin to reduce body temp

arterioles (small artery)
* bring oxygenated blood to skin, divide to form capillaries which take blood just below skin surface, before joining together to form venules.

hair
* hair erector muslces attached to it, when it contracts, pulls hair up straight. traps air.

receptors
* temp receptors - detects change in temp, impulses sent along sensory neurones to CNS.
* pressure receptors - sensitive to pressure.

fat tissue
* helps insulate body against heat loss, acts as energy reserve.

Question 16

define hypothalamus
role of hypothalamus
role of receptors in surface of skin
role of receptors in hypothalamus

Answer 16

• part of brain; controls body temp
• coordinates activities of parts of the body that can help temp of blood at set point.
• contains temp temp receptors ; temp below/above 37; sends electrical immpulses through neurones to part of body which have function of regulating body temp.

hypothalamus -> temp receptors detect sense temp of blood
surface of skin -> temp receptors sense temp of environment around us.

Question 17

what happens when body temp low?

Answer 17

Hairs stand up
* Hair erector muscles contract, hairs stand up. traps insulating layer of air near surface of skin; prevents heat loss.

Shivering
* muscles contract in spasms; makes body shiver. more heat produced from increased respiration.

Vasoconstriction
* narrowing of arterioles, caused by the contraction of the muscle in their walls.
* little blood flows in surface capillaries.
* blood flows through deep lying capillaries instead; beneath fatty tissue, blood doesn’t lose so much heat to the air.

Question 18

what happens when body temp too high

Answer 18

Hairs lie flat
* Hair erector muscles relax, allows heat to leave skin through radiation into air.

Sweat production increased
* sweat glands secrete more sweat. water in it evaporates, taking heat from skin with it, thus cooling body.

Vasodilation
* Widening of arterioles, caused by the relaxation of the muscle in their walls.
* arterioles dilated. blood flood flows through capillaries near surface of skin, bringing more blood so the gland can secrete more sweat.
* heat is readily lost from blood into air,