Negative feedback
Negative feedback makes sure that, as levels return to Normal, corrective mechanisms are scaled down. It’s when the body maintains conditions within particular limits. The body will do this by opposing a change that deviates from the normal.
Core temperature rises.
Core temperature fails.
1) Blood glucose levels: The amount of glucose in your blood is carefully controlled. Again, this uses the hormonal system. The hormones responsible for regulating blood glucose are produced in the pancreas in particular areas called islets of Langerhans.
- Roles of the pancreas and liver
The pancreas is a small gland, located close to the stomach. The pancreas has two main functions. It contains clusters of cells that secrete the pancreatic endocrine hormones and into the bloodstream in order to regulate . In addition, the pancreas plays an important role in food digestion, secreting enzymes that break down fat, starch and proteins in the small intestine.
When glucose levels in the bloodstream get high e.g. after eating, the pancreatic beta cells secrete insulin. This insulin stimulates cells in the body to get the passing glucose, which leads it’s in blood glucose levels to go low. The insulin also instructs the liver to grab glucose and convert it into the glucose-reserve known as glycogen. Equally, when glucose levels in the bloodstream fall below a set point, alpha cells in the pancreas release the hormone Glucagon which tells the liver to re-convert glycogen back to glucose and release it into the bloodstream.
Glucagon promotes the breakdown of glycogen in the liver and the release of glucose into the blood, increasing blood glucose levels.
- Roles of the hormones Insulin and Glucagon
Insulin is a hormone produced in the pancreas that lowers our blood’s glucose levels; it’s released into the blood as soon as the body detects that blood sugar levels have raised above its optimal level.
It is an efficient hormone that runs the body’s fuel storage systems. If there is excess sugar or fat in the blood insulin will signal the body to store it in the body’s fat cells. Insulin also tells these cells not to release their stored fat, making that fat unavailable for use by the body as energy.
Glucagon is a naturally occurring hormone that is produced in the pancreas. The main function of Glucagon is to react to a situation where there is a low level of present. The release of Glucagon into the bloodstream helps to restore blood levels back to a point that is considered acceptable for the general function of the body.
People with some forms of may be at risk to a sudden drop in blood , leading to a crisis situation. The drop may be a reaction to the introduction of too much into the bloodstream.
2) Body temperature:
A) Production of heat by the body, e.g. metabolic processes. Process respiration.
“Normal” human body temperature is 37 C it can change due to fever or something but is mostly stable at this measurement. Body temperature can be taken by placing a clinical thermometer in sites that detect the temperature of the core. Heat is produced inside the body as a by product of metabolic reactions. Heat production occurs throughout the body and is especially high in working muscles. It is often mentioned that the liver is a particular source of heat. Since body heat is a by-product of metabolism, the amount of heat produced depends on the metabolic rate.
B) Loss of heat by the body- Radiation, conduction, convection, evaporation:
For anything to maintain a stable body temperature it is important that heat loss is equal to heat gain. Heat can be gained or lost in 4 different ways:
Radiation: This is the energy that travels through air/space in the form of particles or waves. It is the loss of heat into the surroundings.
Conduction: This involves the transfer of heat between two objects that in contact with each other. Heat is always conducted from a region of higher temperature to a region of lower temperature.
Convection: This is when you warm up the layer of air next your skin and it moves upwards to be replaced by colder air from the ground.
Evaporation: When liquid water is converted into water vapour it requires heat energy to do so.
C) Role of the hypothalamus: The receptors for temperature both heat and cold are located in the peripheral skin and around internal organs. These are specially adapted cells with nerve fibres that run up the spinal cord to the temperature control centre in the hypothalamus of the brain. It sends nerve impulses to muscles, sweat glands and skin blood vessels to cause changes that counteract the external changes.
- Roles of the nervous system-sympathetic and parasympathetic:
The parasympathetic has so important role in the thermoregulation although it helps the unstriated muscle coats of the skin arterioles to relax, but it controls both sweat glands and the calibre of the arterioles.
- Structure and general function of the skin:
Structure: The skin is divided into 2 layers. The outer is the epidermis and the dermis is underneath. The one forming the boundary between both is called Malpighian layer. These cells make the protein keratin and once they have been pushed up into the epidermis they flatten, dry up and die because they have no blood supply that can get to them. The dermis is much thicker than the epidermis and contains many different structures such as nerve endings, hair follicles and blood vessels.
Function: It detects stimuli using cells that are sensitive to heat, cold. Touch, pressure and pain. It prevents excessive water loss or gain. It plays a role in thermoregulation by adjusting heat loss and it prevents entry of micro-organisms. It also secretes hair, fingernails, and toenails.
F) Roles of the skin in control of the body temperature- roles of arterioles and sweat glands.
Arterioles: When a person has high body temperature the arterioles are widened and because of this blood flows through very easily allowing the blood to go through to all parts of the body however if a person has low body temperature it means their arterioles have reduced in size therefore it is harder for the blood to get all around the body.
Sweat glands: If someone has high body temperature it means they are more likely to sweat but if their body temperature is low then they may still sweat but not as much as they would if they are feeling hot. When a person sweats it evaporates in to the air.
G) Effects of shivering:
In the scientific language shivering is called Rhythmic involuntary contractions of the skeletal muscles. It is a very effective way to generate heat so that we can warm up our bodies by doing any type of exercise like jumping, swinging arms or just by rubbing our bodies with our hands.
H) Implications of surface area to volume ratios-for example in the care of babies:
Babies have a larger surface area to volume ratio than adults and cannot effect changes to gain or lose heat for themselves. This means they are at risk of getting illnesses like hypothermia or hyperthermia. Babies do not sweat much and do not shiver. Therefore it is important that in cold weather you wrap up babies well.
I) Fever: This is a type of hyperthermia and is usually caused because of an infection other types may be heat stroke and heat exhaustion. If a person has fever they usually feel cold and look pale due to narrowing down of the arteries. Shivering is also most common. It is not until the new set point has been reached that sweating and other heat loss mechanisms begin.
3) Heart rate:
- Role of internal receptors:
Baroreceptors are sensors located in the blood vessels in the human body. They are the internal receptors in the heart rate. Their job is to detect changes in blood pressure and are found in the walls in the aorta and part of the carotid arteries that deliver the blood to the head and the neck. When someone is known of having high blood pressure it is when these arteries indicate that extra blood has been pumped out by the ventricles as a result of extra blood entering the right side of the heart.
B) Role of the autonomic nervous system- sympathetic and parasympathetic nerve supply:
The heart is controlled by the autonomic nervous system which has 2 branches one named sympathetic nervous system and the parasympathetic nervous system. These 2 systems act like an accelerator and brake on the heart. When the body id undergoing fear, stress or is doing any type of muscular work then the sympathetic nervous system is active. It increases each heartbeat in strength and in heart rate.
The parasympathetic nervous system is active when the body is at peace, or resting and contentment. This system calms down the heart output. The main parasympathetic nerve is called the vagus nerve and this is cut off the heart starts to beat faster.
The sympathetic nervous system is boosted by the hormone adrenaline, this works when someone is frightened or doing something that is scary however they are challenging themselves to do it. Its nerves are the cardiac cycle.
C) Role of cardiac centre and sinoatrial node
Two important centres for control of the heart rate are located in the medulla of the brain. This is the lowest part located just above the spinal cord and is often called the brain stem. The cardio-inhibitory centre is responsible for the origins of the parasympathetic fibres of the vagus nerve which reaches the sinoatrial node while the sympathetic fibres go down through the spinal cord from the vasometer centre.
D Effects of increased Body temperature and adrenaline on heart rate
Circulating adrenaline is a hormone from the adrenaline gland which is released during a time of fear, stress, exertion etc. The sinoatrial node starts to beat faster which boosts the effect of the sympathetic nervous system.
The heart rate starts to increase when the thermo receptors indicate a rise in body temperature to the brain which causes the hypothalamus to activate the sympathetic nervous system.
4) Breathing rate:
A) Role of internal receptors
Internal receptors can be stretch receptors in muscles and tissues that relay nervous impulses to the brain about the status of ventilation from the degree of stretch of muscles and other tissue. The intercostal muscles are the site of many stretch receptors.
B) Role of the autonomic nervous system- sympathetic and parasympathetic nerve supply:
Most internal organs have a dual autonomic supply. Like I explained earlier sympathetic always causes contraction and parasympathetic causes relaxation of muscles. However it can be different in this situation. In the case of bronchial muscle it is opposite, the sympathetic nerve allows it to relax and parasympathetic causes contraction which makes the bronchi narrower. Most of these fibres run in the vague nerve in serving the heart.
C) Role of the respiratory centre, diaphragm and intercostal muscles:
In the upper part of the brain called cerebral cortex voluntary control for breathing takes place. The involuntary centre is known as the respiratory centre is in the medulla and the area just above is known as the pons, these are both at the base of the brain.
The internal receptors send information to each of the centres regarding the state of ventilation. There are two groups of nerve cells known as the inspiratory and expiratory centres and when one is active the other one is deactivated. It clearly shows that the inspiratory centre is actively sending nerve impulses to the nerve to the diaphragm, the phrenit nerve and the thoracic nerves are sending impulses to the intercostal muscles to make contraction take place which results to ispiration.
