21. Liver Need to maintain 4-6 millimoles/L of sugar in blood Organs involved:Pancreas / adrenal glands (hormones)Liver1. LiverLiver is connected via hepatic portal vein to:StomachSpleenPancreasIntestines
3Liver (cont.) Liver has 4 functions for glucose: Removed by liver for energy in LiverRemoved 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
42. Pancreas Islets of Langerhans: Alpha cells: glucagon Beta Cells: insulinInsulin: (decrease blood sugar) from Beta cellsAccelerates transport of glucose from blood to cellsAccelerates ‘glycogenesis’ (glucose glycogen)Stimulates glucose fat (adipose tissue)Increases protein synthesis in some cellsGlucagon: (increase blood sugar) from Alpha CellsStimulates ‘glycogenolysis’ (glycogen glucose)Stimulates ‘gluconeogensis’ (fat/amino acid sugar molecules)Stimulates protein breakdown
53. Adrenal Glands 3 hormones: Cortex: glucocorticoids (eg cortisol) Medulla:adrenalineNoradrenalineGlucocorticoids (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
6Adrenal 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 liverAdrenaline/noradrenaline’s target organ is the liver and the muscles.
9Control of BreathingDiaphragm & intercostals require stimulation from nerves to contract. (unlike heart)Phrenic nerve (a spinal/cervical nerve from neck thorax) diaphragmIntercostal nerve (a spinal/thoracic nerve from neck thorax) Intercostal musclesControlled by respiratory centre in lower medulla2 regions: expiration & inspirationChemoreceptor’s (conc. of chemicals in plasma- specifically CO2, O2 , and H+):Aortic – in aortaCarotid bodies – in carotid (neck) arteryMedulla Oblongata
10Conc .of O2:Receptors in Medulla, Carotid, and aortic bodies.only a large change will have an effectConc. 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
11Conc. of H+:CO2 + H2O H2CO3 H+ + HCO3-As H+ increase, pH decreases, Aortic & Carotid bodies are stimulatedFaster response but not as sensitive as CO2Stretch Receptors:Stimulated when lungs inflateSend impulses to inspiratory neurons in Resp. Centre of Medulla & inspiration ceases, expiration beginsNot very sensitive, only a protective mech. to prevent overstretching
12Voluntary Control of Breathing Connectors from Cerebral Cortex to descending tracts in spinal cordProtective device stops us inhaling water, irritating gases etc.Hyperventilation: Rapid deep breathing, Increases O2, decreased CO2Dangerous as if done before swimming as: Can hold breath longer but not because of abundance of O2, but lack of CO2Exercise and Breathing rate:Depth & rate must increaseHeavy exercise can cause 10 – 20x more ventilationDue to fluctuations in O2, CO2 & H+ conc.
14Cardiac OutputHeart rate: number of times heart beats/minStroke volume: vol of blood forced from a ventricle/contractionCardiac Output: vol of blood leaving ventricle / minCardiac Output = Stroke vol x Heart rateVenus return: return of blood to heartBlood Pressure: Pressure of blood on vessel wallsInfluenced by: cardiac output & diameter of blood vessels
16Regulation of heart rate Specialised cells which initiate impulse in heart:Sinoatria node (SA node) – in right atriumCauses both atria to contractCan 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 ventriclesMay be stimulated by sympathetic NS (noradrenaline)
17Regulation of heart rate (cont.) Heart can be influenced by brain/CNS (Cardiovascular Regulating Centre) in Medulla Oblongata to SA node or AV nodeDetected by pressoreceptors: (baroreceptors) detect blood pressure
19Factors 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 vesselsAutonomic nervous systemOther factors:Age: Highest at birth, slows down towards old age Ave (70-80 bmp)Sex: females fasterEmotional state: strong emotions (anger, fear, anxiety) increase & depression, grief decrease.
21Blood FlowAmount of blood flowing through an organ or vessel (mL/min)Determined by:Cardiac outputDiameter of arterioles. Determined by:CNSHormones (adrenaline – vasodilator in muscle, vasoconstrictor everywhere else)CO2, lactic acid: Vasodilator, O2: Vasoconstrictore.g ExerciseOutput of heart may rise from 5L/min to 30L/min