B9: Animal physiology 4

Question 1

what is the endocrine system

Answer 1

uses hormones
to respond to changes in the environment
or changes inside the body.
It is made up of endocrine glands.

Endocrine glands produce and secrete specific hormones directly into the blood.

Question 2

what are hormones

Answer 2

chemicals
carried in the blood plasma
to other parts of the body
so are relatively slow to act.

Question 3

hormones have a ….

Answer 3

long lasting effect

Question 4

what are target structures

Answer 4

Each hormone only affects particular cells in particular organs.

Question 5

pituitary gland
hormone
role

Answer 5

many

some stimulate other glands to relase hormones

Question 6

thyroid
hormone
role

Answer 6

thyroxine

metabolic rate, heart rate, temp

Question 7

adrenal gland
hormone
role

Answer 7

adrenaline

prepares fight or flight response

Question 8

pancreas
hormone
role

Answer 8

insulin, glucagon

regulates blood sugar

Question 9

ovary
hormone
role

Answer 9

oestrogen, progesterone

helps regulate menstrual cycle

Question 10

negative feeback- thyroxine

Answer 10

level of thyroxine in the blood is monitored by the hypothalamus, a gland close to the pituitary gland.

thyroxine in the blood is higher than the normal range, the release of TSH by the pituitary gland is inhibited.

Less thyroxine is released from the thyroid gland.

The level of thyroxine in the blood falls to within the normal range.

When thyroxine in the blood is lower than the normal range, TSH is released by the pituitary gland.

The thyroid gland is stimulated to release more thyroxine.

The level of thyroxine in the blood rises to within the normal range.

Question 11

adrenaline release process

Answer 11

stimulus 
brain
nerve impulses
adrenal gland stimulated to secrete adrenaline
-stimulates liver to break down glucagon
-increases breathing rate + heart rate 
-stimulates more blood flw to muscles 
increased o2 + glucose supply to brains + muscles cells

Question 12

Regulation of the menstrual cycle

Answer 12

FSH is produced by the pituitary gland
+acts on target structures in the ovaries.
FSH stimulates an ovary:
- to develop a follicle containing an egg (ovum maturation)
- to produce oestrogen.

Oestrogen is produced by the ovaries
- stimulates the uterus lining to thicken.

LH is produced by the pituitary gland and acts on target structures in the ovary
- stimulates the mature follicle to release the egg/ovum (ovulation) in the middle of the cycle (around day 14).

Progesterone is secreted by the empty follicle in the ovary (the yellow body or corpus luteum)
- maintains the lining of the uterus during the second half of the cycle so that a fertilised egg may implant.

Oestrogen and progesterone inhibit the production of LH and FSH.

Decreasing progesterone levels cause the thickened uterus lining to break down and be discharged (menstruation).

Question 13

Use of hormones in contraception

Answer 13

Oestrogen and progesterone prevent ovulation.

These hormones, taken every day, keeps their blood levels high.

High levels of oestrogen and progesterone inhibit FSH production and egg/ovum maturation.

Ovulation cannot take place.

Question 14

Problems with the combined oral contraceptive pill:

Answer 14

not 100% effective
side effects are possible (mainly due to oestrogen) – headaches, nausea, irregular menstrual bleeding, fluid retention
no protection from sexually transmitted diseases (STDs)
relies on remembering to take it daily.

Question 15

skin patch

Answer 15

contains oestrogen and progesterone (same as the combined pill)
- a small patch stuck to the skin – changed each week.

Question 16

implant

Answer 16

inserted under the skin of the arm

• releases a continuous amount of progesterone
• lasts for up to three years.

Question 17

injection

Answer 17

contains progesterone

- each dose lasts 2 to 3 months

Question 18

intrauterine devices

Answer 18

prevent the implantation of an embryo

- plastic IUDs – release progesterone.

Question 19

barrier methods – stop the sperm from reaching an egg

Answer 19

condoms – worn over the penis to prevent sperm from entering the vagina – the only contraceptive device that protects against sexually transmitted diseases

• diaphragm – a shallow plastic cup that fits over the cervix and is used with a spermicide
• spermicide – a substance introduced into the vagina to kill sperm or make them inactive – more effective when used with a diaphragm.

Question 20

surgical methods – permanent sterilisation

Answer 20

• female: oviducts that connect the ovaries to the uterus
• male: sperm duct between the testis and the penis
• very small chance of the structures reconnecting.

Question 21

natural methods

Answer 21

• avoiding sexual intercourse when an egg may be in the oviduct (most fertile time) – not very effective
• abstinence – no sexual intercourse – 100% effective.