Unit 2- Endocrine System

Question 1

Homeostasis

Answer 1

Homeostasis is the process by which the body maintains a stable internal enviornment.

All life has a maintance of homeostasis. They do it by: controlling water levels and mineral levels.

Even when the outside enviornment changes (hot, cold, stress, food, etc.), your body keeps things normal inside.

Question 2

Negative Feedback

Answer 2

The result of a process reduces that process.

So the body:
- moves back to normal
- restores balance
- brings the system towards stability

Question 3

Positive Feedback

Answer 3

The result of a process increases that process.

So the system:
- moves away from balance
- change becomes stronger and stronger

postive feedback=amplification system

Example: childbirth(uterine contractions), blood clotting, fever, milk production

Question 4

Thermoregulation

Answer 4

How your body keeps temperature at 37C

Question 5

Components of Thermoregulation

Answer 5

1. Stimulus - Changes in the temperature of our external environment can cause core body temperature to rise or fall
2. Receptors - Nerve endings in the skin and brain (hypothalamus) sense the
   external and internal body temperature respectively.
3. Control Centre - The hypothalamus (part of our brain) processes signals from the thermoreceptors and signals various effectors that are used to restore the core temperature to its set point (approximately 37°C).
4. Effectors - The following components are used to adjust our core temperature, compensating for the external environment and restoring our
   core temperature to its set point.
   -Skeletal Muscles
   -Smooth Muscle Surrounding
   -Blood Vessels
   -Thyroid Hormones
   -Pituitary
   -Adipose cells
   -Sweat Glands
   -Adrenaline
   -Piloerector Muscles
5. Effect - Our core body temperature is raised / lowered back to it’s set point of approximately 37°C.
   Pituitary release a TSH to tell the thyroid to release thyroxine
   which alters the basal metabolic rate
   -The adipose cells will adjust their cellular respiration rate
   -Blood vessels will constrict or dilate
   -Muscles will shiver to move more or not shiver to move less,
   increase or decrease ventilation rates
   - Hairs will stand up or lay flat
   - Sweat glands will produce more or less sweat

Question 6

Pineal Gland

Answer 6

The pineal gland is a tiny gland in the brain

It is located on the back (dorsal side) of the forebrain

It releases a hormone called melatonin

Question 7

Melatonin

Answer 7

Melatonin controls your body clock (your 24-hour daily cycle, also called the diurnal rhythm).

It helps with: sleep-wake cycle, body temperature, metabolism, pigmentation, menstrual cycle, and defense system.

Question 8

Pancreas

Answer 8

The pancreas is a composite gland, meaning it does two jobs:

Exocrine function → releases digestive enzymes

Endocrine function → releases hormones into the blood

The hormone part is called the Islets of Langerhans

Question 9

Islets of Langerhans

Answer 9

There are 1–2 million islets in the pancreas

They only make up 1–2% of the pancreas, but they are very important.

Two main cell types:

1. Alpha cells- release glucagon
2. Beta cells- release insulin

Question 10

Glucagon

Answer 10

It is a peptide hormone

It is used to raise blood sugar

It works mainly on the liver (hepatocytes) and:
1. Glycogenolsis- breaks glycogen into glucose
2. Glucaneogenesis- makes new glucose
3. Reduces glucose uptake by cells

Result:
- blood sugar increases (this is called hyperglycemia)

Question 11

Insulin

Answer 11

Insulin is a peptide hormone

Insulin lowers blood sugar

It works on:
1.Liver cells (hepatocytes)
2.Fat cells (adipocytes)

It:
- helps cells take in glucose
- hellps cells use glucose for energy
-Converts glucose into glycogen (storage form)- this process is called glycogenesis

Result:
- a decrease in blood sugar(hypoglycemia)

Question 12

Type 1 Diabetes

Answer 12

It is an autoimmune diease
The immune system destroys B cells in the pancreas. This results in no insulin being produced.
Mostly happens to children and young adults and can happen at any age.
Risk Factors: family history and age

Question 13

Type 2 Diabetes

Answer 13

Cells stop responding to insulin, this is called insulin resistance. This results in glucose staying in the blood, and cells aren’t able to absorb sugar properly.

Risk Factors:
- family history
- obesity
- no excercise

Prevention: healthy eating, excercise and an active lifestyle.

It can cause: eye damage, nerve damage, heart disease, kidney failure and slow wound healing.

Question 14

Thyroid Gland

Answer 14

The thyroid is made of:
Follicles (round structures)
Stromal tissue (support tissue)

Each follicle has:
Follicular cells
A hollow center (cavity)

Question 15

Hormones made by follicular cells

Answer 15

Thyroxine (T₄ / tetraiodothyronine)

Triiodothyronine (T₃)

and Iodine is required to make these hormones

Question 15

What thyroid hormones do:

Answer 15

They control metabolism (how your body uses energy)

They help regulate:
🔥 Basal metabolic rate (BMR) → how fast your body works at rest
🩸 Red blood cell production
🍞 Carbohydrate metabolism
🥩 Protein metabolism
🧈 Fat metabolism
💧 Water balance
⚡ Electrolyte balance

Question 16

Extra thyroid hormone:

Answer 16

The thyroid also makes:

Thyrocalcitonin (TCT)

→ a protein hormone
→ controls blood calcium levels

Question 17

Parathyroid Glands

Answer 17

📍 Location
Humans have 4 parathyroid glands
Located behind the thyroid gland
Two on each thyroid lobe

Hormone made:
Parathyroid hormone (PTH)
→ peptide hormone

Question 18

What controls PTH release?

Answer 18

Blood calcium levels (Ca²⁺)

Question 19

What PTH does

Answer 19

PTH increases calcium in the blood

How?

🦴 Bone resorption
→ calcium released from bones into blood

🚰 Kidneys reabsorb calcium
→ less calcium lost in urine

🍽️ More calcium absorbed from food

This results in:
- blood calcium increasing (hypercalcemia)

Question 20

Thymus Gland

Answer 20

it is located above the heart, near the aorta, behind the chest bone and on the dorsal side of the heart.

Function: controlling the immune system

Hormones made: Thymosins (peptide hormones)

Question 21

ADRENAL GLANDS

Answer 21

You have 2 adrenal glands
One on top of each kidney

Each adrenal gland has 2 parts:

🔴 Inner part → Adrenal medulla
🔵 Outer part → Adrenal cortex

Question 21

Function of Thymosins

Answer 21

• Help develop T-lymphocytes (T-cells)
  T-cells give cell-mediated immunity- they fight infected cells directly
• Help with antibody production. This gives humoral immunity.

Question 22

Adrenal medulla

Answer 22

Hormones:
1.Adrenaline
2.Noradrenaline (norepinephrine) called catecholamines

They are released during stress, danger, emergencies, they are called fight or flight hormones.

Question 23

Function of Adrenaline and Noradrenaline

Answer 23

They prepare the body to survive danger: Pupils dilate Heart rate increases Breathing rate increases Heart pumps stronger Alertness increases Sweating Hair stands (piloerection) Glycogen → glucose (↑ blood sugar) Fat breakdown Protein breakdown

Question 24

ADRENAL CORTEX

Answer 24

It produces corticosteroids: 1. Glucocorticoids (controlled by hypothalamus and pituary) Example: Cortisol (Hydrocortisone): - controls energy use - regulates: fats, proteins, carbs - miantains blood pressure - supports heart function Corticosterone - controls immune response - reduces inflammation 2. Mineralocorticoids (controlled by kidneys) Example: Aldosterone: -keeps sodium in the body -works in: kidneys, sweat glands, salivary glands, and colon It controls water balance, salt balance and blood pressure.

Question 25

Cell Signalling

Answer 25

Cells need to communicate with each other to do things like grow, respond to the environment, or reproduce. Chemical signalling is one way they “talk” using molecules.

Question 26

Yeast Mating Example of Cell Signalling

Answer 26

Yeast cells need to find a partner to reproduce. One yeast sends out a chemical signal called a mating factor. The other yeast senses it and grows protrusions toward the sender. Once they touch, mating can happen.

Question 27

Ligands

Answer 27

A molecule (like a key) that binds to a receptor (lock) on a cell to trigger a response.

Question 28

Receptor

Answer 28

Proteins on or inside cells that detect ligands.

Question 29

Two ways for cells to recieve signals

Answer 29

1. Cell surface (transmembrane) receptors: On the cell membrane. Detect water-loving molecules (like proteins or peptide hormones). 2. Intracellular receptors: Inside the cell (cytoplasm or nucleus). Detect small, fat-loving molecules (like steroid hormones).

Question 30

Quorum Sensing (Bacteria Example)

Answer 30

Bacteria can “count” how many are nearby using chemical signals called autoinducers. When many bacteria are present, they turn on genes together. Example: Vibrio fischeri bacteria light up in a squid’s body when enough bacteria are present.

Question 31

Intracellular Receptors (Inside the cell)- How Signalling Works

Answer 31

Small molecules (like testosterone) enter the cell. They bind to a receptor inside the cell → forms hormone-receptor complex. This complex moves to the nucleus, attaches to DNA, and turns on genes → makes proteins → changes the cell. Example: Testosterone binds → activates genes → muscle growth.

Question 32

Transmembrane Receptors (On the cell surface)- How Signalling Works

Answer 32

Large or water-loving molecules (like peptide hormones) cannot enter the cell. They bind to a receptor on the cell surface → triggers a chain reaction inside called a signal cascade using second messengers like cAMP or Ca²⁺. Example: Epinephrine (adrenaline) binds → liver cells break down glycogen to release glucose.