Presentation on theme: "BLOOD SUGAR REGULATION homeostasis. Need to maintain 4-6 millimoles/L of sugar in blood Organs involved: Pancreas / adrenal glands (hormones) Liver 1."— Presentation transcript:
BLOOD SUGAR REGULATION homeostasis
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
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
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
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
Adrenal Glands (cont.) Adrenalin / Noradrenaline: (increase blood sugar) Stimulates glycogen (in muscle cells) lactic acid glucose (in liver) Stimulates glycogenolysis *Note: glucagons target organ is the liver Adrenaline/noradrenalines target organ is the liver and the muscles.
Gas concentrations homeostasis
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 Chemoreceptors (conc. of chemicals in plasma- specifically CO 2, O 2, and H + ): o Aortic – in aorta o Carotid bodies – in carotid (neck) artery o Medulla Oblongata
Conc.of O 2 : Receptors in Medulla, Carotid, and aortic bodies. only a large change will have an effect Conc. of CO 2 : small change results in a large response but chemoreceptors are only located in medulla (70-80% of breathing rate changes are a consequence of CO 2 change detection) Takes several minutes for response
Conc. of H + : CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - As H + increase, pH decreases, Aortic & Carotid bodies are stimulated Faster response but not as sensitive as CO 2 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
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 O 2, decreased CO 2 Dangerous as if done before swimming as: Can hold breath longer but not because of abundance of O 2, but lack of CO 2 Exercise and Breathing rate: Depth & rate must increase Heavy exercise can cause 10 – 20x more ventilation Due to fluctuations in O 2, CO 2 & H + conc.
Blood Pressure/ heart rate homeostasis
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
Regulation of heart rate - Specialised cells which initiate impulse in heart: o Sinoatria node (SA node) – in right atrium Causes both atria to contract Can be influenced by sympathetic (noradrenaline) and parasympathetic NS (acetylcholine) o 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)
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
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 ( bmp) - Sex: females faster - Emotional state: strong emotions (anger, fear, anxiety) increase & depression, grief decrease.
Blood Flow - Amount of blood flowing through an organ or vessel (mL/min) - Determined by: o Cardiac output o Diameter of arterioles. Determined by: CNS Hormones (adrenaline – vasodilator in muscle, vasoconstrictor everywhere else) CO 2, lactic acid : Vasodilator, O 2: Vasoconstrictor e.g Exercise - Output of heart may rise from 5L/min to 30L/min