Homeostasis - Endocrine System

What is thermoregulation?

maintaining a relatively constant body temp for optimum enzyme activity

What is the human body temp?

37 C

What does the body getting too hot lead to?

. heat stroke and dehydration

. damage/denature enzymes

. can lead to death

What does the body getting too cold lead to?

. hypothermia

. slows down enzymes

. can lead to death

How is body temp monitored?

. by thermoregulatory centre in hypothalamus of brain

. contains temp receptors that are sensitive to blood temp

. skin also contains temp receptors and sends nervous impulses to the thermoregulatory centre

What happens to your blood vessels if you get too hot?

. blood vessels supplying skin capillaries dilate (vasodilation)

. so more blood flows closer to the surface

. more heat is lost by radiation which cools you down

What happens to your sweat glands if you get too hot?

. Sweat glands release more sweat

. so more sweat evaporates

. so more energy is transferred from the body to the surroundings which cools you down

What happens to your skeletal muscles if you get too hot?

no shivering / spontaneous contraction

What happens to your erector pili muscles if you get too hot?

relax causing hairs to lie flat

What happens to your blood vessels if you get too cold?

. blood vessels supplying skin capillaries constrict (vasoconstriction)

. so less blood flows closer to the surface

. so less heat is lost by radiation which warms you up

What happens to your sweat glands if you get too cold?

. sweat glands release less sweat

. so less sweat evaporates

. so less energy is transferred from the body to the surroundings

What happens to your skeletal muscles if you get too cold?

. Shivering - rapid, involuntary contractions of skeletal muscles

. increases the rate of respiration which generates heat (exothermic reaction)

What happens to your erector pili muscles if you get too cold?

contract causing hairs to stand up, creating an insulatory layer of warm air

What is the endocrine system composed of?

. endocrine glands which secrete chemicals called hormones directly into the bloodstream

. blood carries hormone to target organ where it produces an effect

How are the effects of the endocrine system different to those of the nervous system?

. slower (bloodstream travels slower than electrical impulses)

. act for longer

What does the pituitary gland do?

. Master endocrine gland

. Secretes several hormones into the blood in response to body conditions

. These hormones act on other glands to stimulate other hormones to be released to bring about effects

What is a target organ and how does a hormone affect it?

. hormone binds to receptor proteins on surface of target cells

. Triggers a response

What hormones are secreted by the pancreas and what is their effect on the body?

. glucagon and insulin

. controls the levels of glucose in the blood

What hormones are secreted by the thyroid gland and what is their effect on the body?

. thyroxine

. controls basal metabolic rate

What hormones are secreted by the ovaries and what is their effect on the body?

. oestrogen and progesterone

. controls development of female secondary sexual characteristics

. involved in the menstrual cycle

What hormones are secreted by the testes and what is their effect on the body?

. testosterone

. controls the development of the male secondary sexual characteristics

. involved in production of sperm

What hormones are secreted by the adrenal glands and what is their effect on the body?

. adrenaline

. prepares body for stressful situations

What hormones are secreted by the pituitary gland and what is their effect on the body?

. ADH - affects amount of urine produced by kidneys

. Growth Hormone - controls growth in children

. FSH - In women: stimulates ovaries to produce and release eggs. In men: stimulates the testes to make sperm and the male sex hormone testosterone

. TSH - stimulates thyroid gland

What is blood glucose conc monitored and controlled by?

pancreas

What happens if blood glucose levels get too high?

. Detected by pancreas

. Pancreas stimulated to release insulin into the blood

. Liver and muscle cells take up excess glucose and convert it into glycogen for storage

. Blood glucose levels decline to a set point; stimulus for insulin release diminishes and body returns to homeostasis

What happens if blood glucose levels get too low?

. Detected by pancreas

. Pancreas stimulated to release glucagon into the blood

. Liver and muscle cells convert glycogen into glucose

. Blood glucose levels rise to a set point; stimulus for glucagon release diminishes and body returns to homeostasis

What is type 1 diabetes?

. a disorder in which the pancreas fails to produce sufficient insulin

. characterised by uncontrolled high blood glucose levels

How is type 1 diabetes normally treated?

insulin injections

What is type 2 diabetes?

a disorder in which body cells no longer respond to insulin produced by the pancreas

What is a risk factor for type 2 diabetes (something that increases the chance of getting it) ?

Obesity

What are common treatments for Type 2 diabetes?

a controlled diet and exercise regime

What is it called when a person has too much glucose in their blood?

hyperglycemia

What is it called when a person has too little glucose in their blood?

hypoglycemia

Why is there too little sugar in the blood if a person with diabetes exercises more than usual?

. Exercise increases rate of respiration

. Muscles use more glucose from the blood to release energy

Why is sugar recommended instead of starchy foods for hypoglycemia?

. sugar = soluble

. so absorbed quickly into bloodstream

. starch has to be digested so slower

Explain, using insulin as an example, what is meant by negative feedback.

. Higher blood sugar level = increased secretion of insulin

. Effect of insulin is to lower blood sugar levels

. Which in turn reduces rate of insulin secretion

. Overall result is to keep fluctuations in sugar levels to a minimum

What are salts also known as?

mineral ions

How do ions and water enter the body?

When you eat and drink

What are 3 ways in which water may be lost from the body?

. via the lungs during exhalation

. from the skin in sweat

. removed via the kidneys in urine

What are 2 ways in which ions may be lost from the body?

. from the skin in sweat

. removed via the kidneys in urine

What are 2 ways in which urea may be lost from the body?

. from the skin in sweat

. removed via the kidneys in urine

Which of the ways of losing water, ions, and urea do we have no control over?

loss by:

. lungs

. skin

Which organs are responsible for controlling the water and salt balance of the body?

kidneys

What happens in the kidneys?

. Glucose, mineral ions, urea, and water all move out of blood and into millions of tubules

. Blood cells and large proteins are too large to leave blood - they don't go into tubules

. All of glucose is reabsorbed back into blood by diffusion and active transport

. No urea is reabsorbed

. Amount of water and dissolved mineral ions that are reabsorbed depends on what your body needs. This is called selective reabsorption

. Unwanted substances (urine) leave kidneys through ureter

How is urea made in the body?

. Digestion of proteins from the diet results in excess amino acids which need to be excreted safely

. In liver these amino acids are deaminated to form ammonia

. Ammonia is toxic so is immediately converted to urea for safe excretion

Why must urea be removed from the blood?

it's poisonous so will cause extensive damage to cells if levels build up

What happens if we have the wrong water balance in the blood?

Body cells lose or gain too much water by osmosis and don't function efficiently

How does the negative feedback system to control water balance work? Use example water conc in blood being too low.

. Water balance controlled by hormone ADH which acts on kidney tubules

. Receptor cells in hypothalamus detect changes to conc of solutes in blood plasma

. When blood is too concentrated more ADH is released by the pituitary gland

. Makes kidney tubules more permeable which allows more water to be reabsorbed during selective reabsoption

. Results in small volume of very concentrated urine

. Concentration of solutes in blood returns to normal levels

. Controlled by negative feedback

How does the negative feedback system to control water balance work? Use example water conc in blood being too high.

. Water balance controlled by hormone ADH which acts on kidney tubules

. Receptor cells in hypothalamus detect changes to conc of solutes in blood plasma

. When water conc of blood is too low, less ADH is released by the pituitary gland

. Makes kidney tubules less permeable which allows less water to be reabsorbed during selective reabsoption

. Results in large volume of dilute urine

. Concentration of solutes in blood returns to normal levels

. Controlled by negative feedback

What are the 2 ways kidney failure may be treated?

. Dialysis

. Kidney transplant

How does dialysis work?

. Arterial blood leaves arm

. Blood thinners added to prevent clotting

. Passed between semi-permeable walls with moving dialysis fluid on the other side

. Dialysis fluid is low in urea, sugar and ion conc is same as in blood

. Excess salt and urea moves out of blood by diffusion through partially permeable membrane along a conc gradient

. No net movement of sugar and other substances needed by the body

. Clean blood flows through bubble trap to get rid of bubbles

. Returns to a vein in the arm

Advantages of dialysis

. Greatly reduced levels of urea

. No change in overall blood glucose levels

. Correct water and ion balance is maintained or restored

Disadvantages of dialysis

. Expensive

. Needs to be connected to a machine for several hours several times a week

. Patients must follow a very rigid diet to avoid complications

. Only works for a limited time for a patient