1. BLOOD SUGAR REGULATION
homeostasis

2. 1. Liver Need to maintain 4-6 millimoles/L of sugar in blood
Organs involved:
Pancreas / adrenal glands (hormones)
Liver
1. Liver
Liver is connected via hepatic portal vein to:
Stomach
Spleen
Pancreas
Intestines

3. Liver (cont.) Liver has 4 functions for glucose:
Removed by liver for energy in Liver
Removed by liver or muscles & converted to glycogen (for storage)
Circulated in blood to be available for body cells to use (as energy)
Excess is converted into fat (long-term storage)
Body stores approx 500g glycogen (100g in liver, remainder in muscles)
Glycogenesis: glucose glycogen (influenced by insulin – from pancreas)
Glycogenolysis: glycogen  glucose (influenced by glucagon – from pancreas)
Glycogen in Liver: enough reserves for 6hrs, after that need to start converting fat

4. 2. Pancreas Islets of Langerhans: Alpha cells: glucagon
Beta Cells: insulin
Insulin: (decrease blood sugar) from Beta cells
Accelerates transport of glucose from blood to cells
Accelerates ‘glycogenesis’ (glucose glycogen)
Stimulates glucose  fat (adipose tissue)
Increases protein synthesis in some cells
Glucagon: (increase blood sugar) from Alpha Cells
Stimulates ‘glycogenolysis’ (glycogen  glucose)
Stimulates ‘gluconeogensis’ (fat/amino acid  sugar molecules)
Stimulates protein breakdown

5. 3. Adrenal Glands 3 hormones: Cortex: glucocorticoids (eg cortisol)
Medulla:
adrenaline
Noradrenaline
Glucocorticoids (increase blood sugar)
Stimulated from anterior pituitary (ACTH)
Stimulate glycogenolysis (glycogen  glucose)
Increases rate by which amino acids are removed by cells & transported to liver for gluconeogenesis (fat/amino acids  glucose)
Promotes mobilisation of fatty acids from adipose to allow fat  glucose

6. Adrenal Glands (cont.)
Adrenalin / Noradrenaline: (increase blood sugar)
Stimulates glycogen (in muscle cells)  lactic acid  glucose (in liver)
Stimulates glycogenolysis
*Note:
glucagon’s target organ is the liver
Adrenaline/noradrenaline’s target organ is the liver and the muscles.

8. Gas concentrations
homeostasis

9. Control of Breathing
Diaphragm & intercostals require stimulation from nerves to contract. (unlike heart)
Phrenic nerve (a spinal/cervical nerve from neck  thorax)  diaphragm
Intercostal nerve (a spinal/thoracic nerve from neck  thorax)  Intercostal muscles
Controlled by respiratory centre in lower medulla
2 regions: expiration & inspiration
Chemoreceptor’s (conc. of chemicals in plasma- specifically CO2, O2 , and H+):
Aortic – in aorta
Carotid bodies – in carotid (neck) artery
Medulla Oblongata

10. Conc .of O2:
Receptors in Medulla, Carotid, and aortic bodies.
only a large change will have an effect
Conc. of CO2:
small change results in a large response but chemoreceptors are only located in medulla (70-80% of breathing rate changes are a consequence of CO2 change detection)
Takes several minutes for response

11. Conc. of H+:
CO2 + H2O H2CO3  H+ + HCO3-
As H+ increase, pH decreases, Aortic & Carotid bodies are stimulated
Faster response but not as sensitive as CO2
Stretch Receptors:
Stimulated when lungs inflate
Send impulses to inspiratory neurons in Resp. Centre of Medulla & inspiration ceases, expiration begins
Not very sensitive, only a protective mech. to prevent overstretching

12. Voluntary Control of Breathing
Connectors from Cerebral Cortex to descending tracts in spinal cord
Protective device  stops us inhaling water, irritating gases etc.
Hyperventilation: Rapid deep breathing, Increases O2, decreased CO2
Dangerous as if done before swimming as: Can hold breath longer but not because of abundance of O2, but lack of CO2
Exercise and Breathing rate:
Depth & rate must increase
Heavy exercise can cause 10 – 20x more ventilation
Due to fluctuations in O2, CO2 & H+ conc.

13. Blood Pressure/ heart rate
homeostasis

14. Cardiac Output
Heart rate: number of times heart beats/min
Stroke volume: vol of blood forced from a ventricle/contraction
Cardiac Output: vol of blood leaving ventricle / min
Cardiac Output = Stroke vol x Heart rate
Venus return: return of blood to heart
Blood Pressure: Pressure of blood on vessel walls
Influenced by: cardiac output & diameter of blood vessels

16. Regulation of heart rate
Specialised cells which initiate impulse in heart:
Sinoatria node (SA node) – in right atrium
Causes both atria to contract
Can be influenced by sympathetic (noradrenaline) and parasympathetic NS (acetylcholine)
Atrioventricular node (AV node) -in septum between two atria (near AV valves)
After being stimulated by Av node, conducting fibres from Av node pass impulse to both ventricles
May be stimulated by sympathetic NS (noradrenaline)

17. Regulation of heart rate (cont.)
Heart can be influenced by brain/CNS (Cardiovascular Regulating Centre) in Medulla Oblongata  to SA node or AV node
Detected by pressoreceptors: (baroreceptors) detect blood pressure

19. Factors influencing stroke Volume
Length of diastole: period of relaxation between contractions. (time to fill up)
Venus return: contraction of the muscle fibres of the heart is more forceful when fibres are stretched (elasticity) influenced by activity of skeletal muscles, respiratory movements, tone of vein walls, reduced friction in vessels
Autonomic nervous system
Other factors:
Age: Highest at birth, slows down towards old age Ave (70-80 bmp)
Sex: females faster
Emotional state: strong emotions (anger, fear, anxiety) increase & depression, grief decrease.

21. Blood Flow
Amount of blood flowing through an organ or vessel (mL/min)
Determined by:
Cardiac output
Diameter of arterioles. Determined by:
CNS
Hormones (adrenaline – vasodilator in muscle, vasoconstrictor everywhere else)
CO2, lactic acid: Vasodilator, O2: Vasoconstrictor
e.g Exercise
Output of heart may rise from 5L/min to 30L/min