Homeostasis

Question 1

Define Homeostasis

Answer 1

The ability of the body to maintain a stable environment despite changes in external conditions, it can control everything from glucose level, PH, temperature

Question 2

Name the four main receptors in the body

Answer 2

• Barorecepters
• Chemoreceptors
• Stretchreceptors
• Thermoreceptors

Question 3

What do they do and where are Baroreceptors found

Answer 3

They are found in the carotid sinus and in the aortic arch, the function is to detect pressure changes in the aortic wall and provide a fast response to blood pressure

Question 4

What do they do and where are Chemoreceptors found

Answer 4

• There are two types of chemoreceptor the aeortic one detects changes in blood oxygen and carbon dioxide but not PH.
• carotid body detects all three parts,
• Medulla oblongata

Question 5

What do they do and where are Stretchreceptors found

Answer 5

Are responsible for the distention of various organs and muscles and are neurologically linked to the medulla oblongota in the brain stem. Examples are in the arm and leg muscles, tendons and heart

Question 6

What do they do and where are Thermoreceptors found

Answer 6

Specialised nerve cells that are able to detect changes in temperature, they are found throughout the skin.

Question 7

Three stages there must be to keep homeostasis (feedback loop)

Answer 7

• Receptor
• Control Centre
• Effector

Question 8

Explain what cardiac output is

Answer 8

Cardiac output: The amount of blood the heart pumps through the circulatory system in a minute. The amount of blood put out by the left ventricle of the heart in one contraction is called the stroke volume. The stroke volume and the heart rate determine the cardiac output.

Question 9

Whats the calculation for Cardiac output

Answer 9

CO = STROKE VOLUME X HR

Question 10

Define peripheral resistance

Answer 10

Peripheral resistance is the resistance of the arteries to blood flow. As the arteries constrict, the resistance increases and as they dilate, resistance decreases. Peripheral resistance is determined by three factors: Autonomic activity: sympathetic activity constricts peripheral arteries.

Question 11

Equation for BP

Answer 11

BP = Cardiac output x Peripheral Resistance

Question 12

How is Homeostasis maintained in relation to Acidosis/Alkolosis

Answer 12

When the body senses that the number of ion’s in the system is pushing the blood towards a more acidic PH, this is picked up by the chemoreceptors, it picks up the HR so that the circulatory system can clear them through to the Lungs, thus expelling them through a increase in respiration and the expelling of CO2.

Question 13

How is homeostasis maintained in relation to Hypo/Hyperhermia

Answer 13

Your body heats up and is picked up by thermoreceptors in the skin, they send a signal to the hypothalamus in the brain to cool the body down.
First thing it does is sends a message to dilate the blood vessels, it does this so more warm blood is flowing near the skin so that heat can be lost, its why we looked flushed when hot.
Second thing it does is release sweat which through the process of convection cools the skin.
The opposite is what happens when we are to cold.

Question 14

How is homeostasis maintained in relation to hypo/hyperglyceamia

Answer 14

High blood sugar is picked up by the pancreas to release insulin, The liver converts any excess glucose into glycogen thus blood sugar goes up.

Question 15

Define the oxygen dissociation curve

Answer 15

The oxygen-haemoglobin dissociation curve is a graph that compares the % of haemoglobin saturated with oxygen on the y-axis to the partial pressure of oxygen in the blood on the x-axis (mmHg). It is a useful tool for understanding how oxygen is transported to the tissues of the body from the lungs.
In areas where the partial pressure of oxygen in the blood is high (i.e. in the capillaries of the lungs), almost all of the haemoglobin will become saturated with oxygen. In areas where the partial pressure of oxygen is low (i.e. in the capillaries supplying the tissues of the body), the haemoglobin will release it’s oxygen and thereby supply the cells of the tissue with oxygen for respiration.

Question 16

Explain what a right shift or left shift in the oxygen dissociation curve means

Answer 16

If the curve shifts to the right it means that the haemoglobin has decreased affinity for oxygen. In general, factors that decrease haemoglobin’s oxygen affinity are those physiological states where body tissues require more oxygen e.g. during exercise. While exercising, temperature, carbon dioxide levels and lactic acid levels increase and all these changes cause right shift.

Left shift occurs under opposite conditions to right shift, and is where the haemoglobin has increased affinity for oxygen and won’t release it as readily.

Question 17

What does Afferent mean

Answer 17

Carries nerve impulse towards the CNS from the receptor

Question 18

What does Efferent mean

Answer 18

Carries nerve impulses from the CNS to the effectors

Question 19

Define a negative feedback mechanism

Answer 19

Almost all homeostasis control mechanisms are negative, they change the variable back to its original state or ideal value.

Question 20

Define positive feedback mechanisms

Answer 20

In a positive feedback to original effect of the stimulus is increased to keep on getting the same response i.e. child birth and the release of oxytocin

Question 21

What hormones are used and how do they effect blood pressure

Answer 21

• The renin-angiotensin-aldosterone system (RAAS) is a hormone system that regulates blood pressure and water (fluid) balance .
• It starts with angiotensin II, which acts to stabilize blood pressure and volume.
• Renin is secreted by the liver and reacts with A2, converting it to angiotensin I.
• After renin facilitates the production of angiotensis I, angiotensin converting enzyme (ACE) then converts angiotensin I to angiotensin II. Angiotensin II raises blood pressure by constricting blood vessels.
• This, in turn, stimulates the renal tubules to reabsorb more sodium. Angiotensin II also triggers the release of anti-diuretic hormone (ADH) from the hypothalamus, leading to water retention in the kidneys.
• It acts directly on the nephrons, decreasing glomerular filtration rate. Thus, via the RAAS, the kidneys control blood pressure and volume directly.
• Medically, blood pressure can be controlled by drugs that inhibit ACE (called ACE inhibitors).

Question 22

How is Homeostasis maintained in relation to tachycardia and bradycardia, and hypo/hypertension

Answer 22

• Baroreceptors in the aortic and carotid boys detect a change in the pressure
• They send a signal via the vagus nerve unto the medulla oblongata from the aorta and via the glassopharyngel nerve in the carotid.
• A decision is made in the cardiac control centre and if the BP is to high a efferent message is sent back down the vagus nerve by the parasympathetic fibres to the SA node
• Then a chemical is released which slows or spends up the rate of which the SA node fires,
• If the heart rate is to low a efferent signal is sent via the cardiac nerve by sympathetic fibres to the SA node which stimulate it to speed up.
• In relation to High/low BP, if the BP is high once the HR slows it reduces cardiac output thus reducing BP, the opposite for Low blood pressure

Question 23

Why is it harder for newborns to regulate temperature

Answer 23

• They have a large body surface area compared with their weight. Their body heat is lost more rapidly when exposed to cold weather conditions.
• Their ability to regulate body temperatures is not well-developed. They are not able to shiver (which warms a person up).
• They don’t have much fat under their skin (which keeps them warm).

Question 24

Why is it harder for older people to regulate there temperature

Answer 24

• Most body heat is generated as a by-product of metabolism. As age increases muscle activity decreases as does the number of functioning cells of the primary organs
• the skin becomes thinner and subcutaneous fat diminishes
• Receptor density and sensitivity decrease with age. Therefore the elderly have a delayed response to the cold or hot. Due to this loss of receptors or decrease in their sensitivity, the body’s temperature control centers (hypothalamus and brain stem) are slow or ineffective in their response to the temperature changes