Animal Coordination, Control, and Homeostasis

What is homeostasis?

Maintenance of a stable internal environment in the body despite fluctuations in internal and external conditions.

Why is homeostasis important ?

Ensure optimum conditions for enzymes and cellular processes in the body

What conditions in the body must be controlled by homeostasis?

• Temperature

• Blood glucose concentration

• Water levels

What is thermoregulation?

Maintenance of core body temperature.

What does the maintenance of an ideal body temperature depend on ?

A negative feedback system involving:

• Receptors

• Hypothalamus

• Effectors eg sweat glands

Where are temperature sensitive receptors located ?

• Skin - epidermis, dermis

• Hypothalamus

What is the function of receptors in the skin and in the hypothalamus ?

They detect changes in blood temperature and send information to the hypothalamus.

What is the function of the hypothalamus?

Acts as the thermoregulatory centre - coordinates information from the receptors and sends instructions to the effectors.

What is the function of the effectors?

Produce a response to counteract the change in blood temperature and return it to the set point.

What thermoregulatory responses occur when the temperature is too high?

• Sweating

• Vasodilation

What structure produces sweat?

Sweat glands found in the dermis layer?

How is sweat released from the skin?

Pores in the epidermis release sweat onto the skins surface which then evaporates.

How does sweating reduce body temperature?

Heat energy is used to evaporate sweat. Increased heat transfer from the skin to the environment decreases body temperature.

What thermoregulatory responses occur when body temperature is too low?

• Shivering

• Hair erector muscles contract

• Little to no sweat is produced

  
  

How does shivering increase body temperature?

Rapid contraction of skeletal muscles generates heat energy from respiration.

How does the contraction of hair erector muscles help to increase body temperature?

Hairs stand on end creating pockets of air between hairs and a layer of insulation.

What is osmoregulstion?

The maintenance of constant water levels in the body fluids of an organism.

Why is osmoregulation important ?

Prevents cells bursting or shrinking when water enters or leaves by osmosis.

Which organ is responsible for the maintenance of blood glucose concentrations?

Pancreas.

Which hormone is released when blood glucose concentration is too high?

Insulin and is secreted by the pancreas into the blood.

What is the role of insulin?

Causes liver and muscle cells to increase their uptake of glucose from the blood. Glucose is converted into glycogen which decreases blood glucose concentration.

Which hormone is released when blood glucose concentration is too low?

Glucagon and released by the pancreas into the bloodstream.

What is the role of glucagon?

Causes the breakdown of glycogen to glucose in the liver. Glucose is released into the blood which increases blood glucose concentration.

What are antagonistic hormones?

Have opposite effects which counteract one another eg insulin and glucagon.

How is control of blood concentration an example of negative feedback?

To control blood glucose concentration, insulin inhibits release of glucagon from the pancreas when blood sugar is normal or at high concentration.

What is diabetes?

Condition where the homeostatic control of blood glucose levels stop working.

Why are the symptoms of diabetes?

• Feeling very thirsty

• Feeling very tired

• Cuts/wounds healing slowly

What is the cause of type 1 diabetes?

The pancreas can’t produce enough insulin. It is congenital.

How is type 1 diabetes treated?

• Daily insulin injections

• Limiting intake of refined sugars

• Regular exercise

What is the cause of type 2 diabetes?

Person develops insulin resistance/doesn’t produce enough insulin. Can be due to obesity, family history, lack of history.

How is type 2 diabetes treated?

• Balanced diet

• Exercise

• Medication or insulin injections

How does exercise help to control diabetes?

Exercise increases respiration in muscle cells. Excess glucose is removed from the blood to produce energy in the form of ATP.

How is BMI calculated?

Mass(kg) / height(m)2

What is one function of the urinary system?

Removes impurities, toxic waste substances from the blood via excreting urine.

What structures are in the urinary system?

Kidneys, ureters, bladder, and urethra.

What is the function of the renal artery?

Supplies blood, containing impurities, to kidneys.

What is the function of the renal vein?

Drains blood from kidneys.

What is the function of the ureter?

Carried urine to bladder from kidneys.

What is the function if the urethra?

Released urine from the bladder out of the body.

What is the function of the kidneys?

• Removes toxic waste substances from the body

• Alters blood water levels

• Alters blood ion levels

  
  

What is urine?

Waste product of the kidney that contains urea, excess water and ions.

How is urea produced?

In the liver, urea is produced from the breakdown of excess amino acids.

What is a nephron?

Kidney contains over a million function units know as nephrons, their function is filtration and removal of waste.

What is the structure of a nephron?

Glomerulus, Bowmen’s capsule, tubules, and the collecting duct.

What is the glomerulus?

A ball of small blood vessels where blood is filtered via ultrafiltration.

What is the Bowmen’s capsule?

Structure surrounding the glomerulus to collect the filtrate.

What stages occur in the nephron?

• Filtration

• Selective reabsorption of glucose

• Reabsorption of water

Describe filtration in the kidneys.

Blood flows through the glomerulus under high pressure. Small molecules, water, and ions are filtered out of the blood and into the Bowmen’s capsule of the nephron.

Why do large molecules ( red blood cells, proteins ) remain in the blood?

Too large to fit through the pores in the capillary walls of the glomerulus.

Which substances are selectively reabsorbed from the nephron tubule?

• All sugars

• Some water

• Some ions

What happens to molecules not selectively reabsorbed?

Travel down the kidney tubule as urine is transported to the bladder via the ureter. Here they are stored and eventually excreted.

How is the concentration and volume of urine controlled ?

Secretion of ADH.

Where is ADH secreted from?

Stored and released from the pituitary glands.

How does ADH affect the reabsorption of water from the nephron?

ADH increases the permeability of the collecting ducts, enabling more water to be reabsorbed into the blood.

What is required to maintain the ideal water content of blood?

• Receptors in the hypothalamus

• Hypothalamus

• Effector eg pituitary gland

What occurs when low blood water concentration is detected?

• Receptors detect low blood water content and send information to the hypothalamus

• Pituitary gland increases ADH secretion

• ADH increasing collecting duct permeability so more water is reabsorbed into

• Blood water content increases, more concentrated urine is produced

What occurs when high blood water concentration is detected?

• Receptors detect high water blood content and send information to hypothalamus

• Pituitary gland secretes less ADH

• Collecting duct becomes less permeable do less water is reabsorbed

• Blood water content decreases, more dilute urine is produced

How can kidney failure be treated?

• Kidney dialysis

• Kidney transplant

What is kidney dialysis?

A machine artificially filters a patients blood, taking up the role of the kidney.

How does kidney dialysis work?

• Blood taken from vessel in arm

• Partially permeable barrier separates blood from dialysis fluid

• Urea, excess ions and water move out of the blood and into the dialysis fluid

• Large cells and proteins remain in the blood

What is the composition of dialysis fluid?

• Same concentrating of glucose and ions as in normal blood plasma

• No urea, so urea will diffuse out of the blood down its concentration gradient

What is the advantage of kidney transplants over dialysis?

Dialysis requires time consuming appointments whereas transplant means the kidney is replaced at once

What is a risk of kidney transplants?

Body rejecting the transplanted kidney.

What precaution are taken to reduce risk of kidney rejection?

• Tissue typing ensure that the transplanted organ is compatible with the recipient

• Immunosuppressant drugs help prevent the immune system from rejecting the organ