Homeostasis Flashcards
Homeostasis
regulation of conditions inside the body to maintain a stable internal environment in response to both internal and external conditions.
Negative Feedback
The response eradicates/reduces the stimulus
Positive Feedback
The response intensifies the stimulus e.g. childbirth
Stimulus
A change in the environment
Receptor
Detects change in environment
Modulator
Interprets the message and initiates a response
Effector
Muscle or gland that carries out the response
Feedback
Change in original stimulus
Conduction
Transfer of heat through contact
Convection
Liquid or gas rises from the skin
Radiation
Transfer of heat through electromagnetic radiation
Evaporation
Transfer of heat as liquid moves into a gas phase
Physiological Response to cold
- Piloerection
- Shivering
- Thyroxine (metabolic rate)
- Adrenal Medulla (cellular respiration)
- Behavioural
- Vasoconstriction
Physiological Response to Heat
- Pilorelaxation
- Sweating
- Thyroxine (metabolic rate)
- Behavioural
- Vasodilation
Role of the Liver in blood glucose regulation
Converts glucose into glycogen and glycogen into glucose (blood passes through the hepatic portal vein)
Four Options:
- Can be removed from the bloodstream and stored as glycogen in the liver
- Can continue circulating, fueling other body cells
- Can be removed to fuel the liver
- Excess glucose is converted into fat
Liver glycogen can then be released or used for the liver’s activities
Role of the pancreas; Alpha Cells
Secretes Glucagon (raises blood sugar)
Three ways:
- Stimulates Glycogenolysis (breakdown of glycogen into glucose)
- Stimulates Gluconeogenesis (production of glucose from amino acids, fats)
- Promotes protein breakdown, freeing amino acids for gluconeogenesis
Role of pancreas; Beta Cells
Produces Insulin (lowers blood sugar)
Four Ways:
- Promotes the uptake of glucose into cells
- Increases rate of glycogenesis (production of glycogen from glucose)
- Increases the rate of fat production from glucose
- Promotes protein synthesis (decreasing gluconeogenesis)
Role of Adrenal Glands; Adrenal Cortex
Stimulated by Adrenocorticotrophic Hormones and release Cortisol, which regulates carbohydrate metabolism, stimulating glycogenolysis and increasing gluconeogenesis
Role of Adrenal Glands; Adrenal Medulla
Stimulated by the sympathetic nervous system, secreting Adrenaline and Noradrenaline, which increases cellular metabolism and therefore blood sugar levels.
Urine Formation
Filtration (Renal Corpusle)
Selective Reabsorption (PCT, LH, DCT)
Tubular Secretion (PCT, DCT)
- Only water loss source that can be regulated
NEPHRON IS EFFECTOR
Reabsorption of Water
60-70% of water reabsorption occurs in the PCT
30-40% is selective reabsorbed in the LH, DCT, CD
Reabsorption in DCT is active transport
Osmoreceptors
Located in thirst centre of the Hypothalamus
- If blood volume decreases than osmotic pressure is raised
- If blood volume increases than osmotic pressure is reduced
Role of ADH
Thirst centre in hypothalamus stimulates the release of ADH from the posterior pituitary gland.
ADH targets the DCT and CT increasing their permeability causing more water to be absorbed in the blood plasma.
Role of Aldosterone
Promotes reabsorption of sodium from the urine
Dehydration
Increased osmotic pressure
Triggers thirst reflex and individual drinks water which is then absorbed.
Diaphragm
COntrolled by the phrenic nerve
Intercostals
Controlled by the intercostal nerves
Expiratory centre in the Medulla Oblongata
COntrols breathing out
Sends impulses to the Internal intecostals
Inspiratory centre in the Medulla Oblongata
Controls breathing in
Sends impulses to the diaphragm and external intercostals
Central Chemoreceptors
In the medulla oblongata
Control CO2 concentrations, and ph of blood plasma and cerebrospinal fluid
Delayed response
More sensitive
Responsible for the majority of control of breathing
Peripheral Chemoreceptors
In aortic and carotid bodies
Measures changes in ph (hydrogen ion concentration and CO2 and o2 in blood plasma
Responds quicker due to location
Responds largely to hydrogen ion and co2 levels with breathing rate
Hyperventilation
Rapid and deep breathing where the body provides more oxygen and removes more carbon dioxide than neccessary. As the breathing reflex responds to CO2, the person may require o2 levels before co2 levels rise to the point where the body stimulates the breathing reflex
Cardiac output
Heart rate x stroke volume
Determines the amount of blood ejected from the heart per minute
- Determines the blood pressure (with diameter of blood vessels)
Regulation of heartbeat
Sinoatrial Node
- pacemaker and initiates heartbeat in the right wall of the right atrium
Atrioventricular Node
- regulates beating of ventricles
Pressoreceptors
Found in the aorta, right atrium, and right carotid artery
Cardiac Centre
In medulla oblongata
connects to SV and AV through sympathetic and parasympathetic nerve fibres
