Biology - Chapter 11-15 - Excretion, Homeostasis, Nervous system, Eye and Hormones

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  • 1. Chapter 11: ExcretionExcretion – Process by which toxic materials and metabolic wastes are removed from the body of anorganism. Egestion – removal of undigested material from the alimentary canal = NOT EXCRETION.Accumulation of nitrogenous and other compounds in an organism is harmful to the organism.Excretory organs – Skin, kidney and lungs URINE FORMATION 1. Ultrafiltration – mechanical filtration of different solutes (waste, nutrients) in the blood plasma, except red and white blood cells that takes place due to a high hydrostatic blood pressure produced by the difference in diameter between the afferent and efferent arteriole, in each glomerulus, through a selectively permeable membrane. For ultrafiltration to occur, there must be a high hydrostatic blood pressure formed because the afferent arteriole has a larger diameter than the efferent arteriole. A partially permeable membrane (aka. basement membrane) must be present as it acts as a filter and only allows small molecules to pass through.
  • 2. 2. Selective reabsorption – process whereby useful materials are taken back into the blood stream by osmosis (water), diffusion and active transport (glucose, amino acids) Region Processes - Most of the mineral salts and all of the glucose and amino acids reabsorbed by First convoluted tubule diffusion and active transport. - Most of the water is reabsorbed by osmosis. Loop of Henle - Remaining water is reabsorbed by osmosis. - Remaining water is reabsorbed by osmosis. Second convoluted tubule - Mineral salts (eg. Na+) is reabsorbed by diffusion and active transport. Collecting duct - Remaining water is reabsorbed by osmosis. Excess water, excess salts and metabolic waste products (eg. urea, uric acid and creatinine) pass out of the collecting duct into renal pelvis as a mixture called urine. OSMOREGULATION WITH ANTI-DIURETIC HORMONE (ADH)
  • 3. Dialysis1. Kidney failure is fatal as the body is not able to remove waste materials such as urea and other toxic chemicals.2. Patients suffering from kidney failure can use a kidney dialysis machine to remove urea as well as balance their salt concentration.3. Blood is drawn from an artery in the patient’s arm and flows through a narrow tubing throught the dialysis machine and is soon returned to a vein in the patient’s arm. Characteristic of dialysis How it helps? Allows only small solutes such as urea, excess salts and Partially permeable water to diffuse out from the blood while RBCs and tubing WBCs remain in the blood. Increases surface area to volume ratio to increase the Long, narrow and coiled rate of diffusion. tubing Ensures that these substances do not diffuse into the dialysis fluid when the blood plasma has a higher Same concentration of concentration of these substances. essential substances as normal blood plasma Allows these substances to diffuse into the blood when the blood plasma has a lower concentration of these substances. Ensures a steep concentration gradient which increases No metabolic waste in the rate of diffusion of waste products to be diffused supplied dialysis fluid out into the dialysis fluid. Direction of blood flow is Maintains the concentration gradient at all sections of opposite to direction of the dialysis machine to increase rate of diffusion. flow of dialysis fluid Treatment is 2-3 times a Allows sufficient time for the waste products to be week for a few hours removed from the blood.
  • 4. Chapter 12: HomeostasisHomeostasis is the maintenance of a constant internal environment.4 basic principles of homeostasis:1. Stimulus – change in the internal environment2. Receptor – detects the stimulus3. Corrective mechanism – reverses effects of stimulus4. Negative feedback – provides information to receptor to stop corrective mechanis,Structure of mammalian skin REGULATING HEAT IN THE BODY
  • 5. Chapter 13: Nervous System1. Central nervous system (CNS) consists of brain and spinal cord, Peripheral nervous system (PNS) consists of cranial nerves and spinal nerves.2. CNS does not come in direct contact with external environment. PNS comes in direct contact with external environment. direction of nerve impulse direction of nerve impulse Neurone part Form and function Contains nucleus and much of cytoplasm; most Cell body of the metabolic activity of the cell occurs here Axon Transmits impulses away from the cell body Dendrons Transmits impulses towards the cell body Dendrites Terminal branches on axons and dendrons Layer of fatty substance that encloses the nerve Myelin sheath fibre and insulates axon Neurilemma Thin membrane surrounding myelin sheath Motor end plate (applicable to motor neuron) Junction between dendrite and muscle fibre Regions where myelin sheath is absent allow Nodes of Ranvier nerve impulses to jump from node to node, increasing the speed of nerve transmission
  • 6. Path of a nerve impulse STIMULUS causes RECEPTOR to create impulse… Step 1: Sensory neuron at receptor  Step 2: Sensory neurons in nerves  Step 3: Sensory neuron at dorsal root ganglion  Step 4: SAME sensory neuron in dorsal root  Step 5: SYNAPSE with relay neuron in grey matter in spinal cord (neurotransmitters released)  Step 6: Brain (processes information)  Step 7: Relay neuron in grey matter in spinal cord  Step 8: Motor neuron in ventral root  Step 9: Motor neuron in nerves  Step 10: Effector… EFFECTOR causes RESPONSE3. The nervous system serves to coordinate and regulate bodily functions.4. A reflex is an immediate response to a specific stimulus without conscious control.5. A reflex arc is the shortest pathway by which nerve impulses travel from the receptor to the effector in a reflex action.6. Receptors and effectors – i. Knee jerk reflex: Sensory receptor in patellar tendon, Upper thigh muscle ii. Hand on hot object reflex: Thermoreceptors in skin, Biceps
  • 7. Chapter 14: The Human EyeExternal eye part Form and function Frontal transparent dome-shaped part of the Cornea eye. Refracts most of the light, providing most of the eye’s focusing power. Thin transparent epidermal layer that covers Conjunctiva anterior surface of the eye. Coloured part of eye controls the light levels Iris inside the eye. Embedded with tiny muscles that dilate and constrict the pupil size. Pupil Round opening in the centre of eye. Protects the cornea from mechanical damage, can be partly closed (aka. squinting) which Eyelid prevents excessive light from entering the eye. Blinking spreads tears and wipes the dust particles off the cornea. Eyelashes Helps shield eye from dust particles. Secretes tears which washes dust particles away, keeps cornea moist for atm oxygen to Tear gland dissolve and diffuse and lubricates conjunctiva to reduce friction during blinking. Tough, white outer covering of the ball, Sclera continuous with cornea, protects from mechanical damage. Contains blood vessels that nourish the eye tissue, pigmented black to prevent internal Choroid reflection, connected to ciliary body and edges of optic nerve, it is between sclera and retina.
  • 8. Innermost layer of eye which contains photoreceptors (ie. rods and cones) which Retina receive light and converts it into nerve impulses that travel along optic nerve. A transparent, circular and biconvex structure Lens which is elastic and changes its shape and thickness to refract light into retina. A tissue attaching the edge of the lens to theSuspensory ligaments ciliary body. A thickened region at the front end of the Ciliary body choroid which contains ciliary muscles that control curvature or thickness of lens. Space between lens and cornea, filled with aqueous humor, a transparent, watery fluid that Aqueous chamber keeps the front of the eyeball firm and helps to refract light into the pupil. Space behind the lens, filled with vitreous humor, a transparent, jelly-like substance that Vitreous chamber keeps eyeball firm and helps refract light onto the retina. Small yellow depression in the retina which is situated directly behind the lens. This is where Fovea images are normally focused. It has the greatest concentration of cones but has no rods. This allows detailed colour vision in bright light. A nerve that transmits nerve impulses to the Optic nerve brain when the photoreceptors in the retina is stimulated. The region where the optic nerve leaves the Blind spot eye. It does not contain any rods or nerves hence it is not sensitive to light. Allow us to see in dim light, but only in black and white as they contain visual purple, Rods formation of visual purple needs Vit A, more sensitive to light than cones. Allow us to see colours in bright light, three types of cones: red, blue and green, each cone Cones contains a different pigment that absorbs light of different wavelengths, do not work well in dim light.
  • 9. PUPIL REFLEXAccommodation/ Focusing1. Focusing on a distant object (ie. more than 7 metres) STEP 1: Ciliary muscles relax, pulling on suspensory ligaments. (Chicken rice plates) STEP 2: Suspensory ligaments become taut, pulling on edge of lens. STEP 3: Lens becomes thinner and less convex, increasing its focal length. STEP 4: Light rays from the distant object are sharply focused on the retina STEP 5: Photoreceptors in the retina are stimulated. STEP 6: Nerve impulses produced are transmitted by the optic nerve to the brain.2. Focusing on a near object (ie. less than 7 metres) STEP 1: Ciliary muscles contract, relaxes pull on suspensory ligaments. (Cheesy chicken rice) STEP 2: Suspensory ligaments slacken, relaxing pull on edge of lens. STEP 3: Lens becomes thicker and more convex, decreasing its focal length. STEP 4: Light rays from the near object are sharply focused on the retina STEP 5: Photoreceptors in the retina are stimulated. STEP 6: Nerve impulses produced are transmitted by the optic nerve to the brain.
  • 10. Chapter 15: HormonesA hormone is a chemical substance, produced by a gland, carried by the blood, which alters the activityof one or more specific target organs and is then broken down by the liver.Exocrine glands pour their secretions out of the body via ducts or tube.(eg. salivary gland, sweat gland)Endocrine glands secrete their hormones into the bloodstream, has no ducts or tube.(eg. pituitary gland, adrenal gland)Pancreas is an exocrine and an endocrine gland as: 1. Secretes pancreatic juice carried away by pancreatic duct to duodenum. 2. Islets of Langerhans secrete insulin and glucagon (hormones) into bloodstreamEndocrine glands:Pituitary gland (ADH as well as master gland), hypothalamus (regulates secretion of some pituitaryhormones), thyroid gland (thyroxine), ovaries (progesterone and oestrogen), testes (testosterone),adrenal gland (adrenaline), pancreas (insulin and glucagon) Hormone Effects 1. Increases blood glucose level by speeding up breakdown of glycogen to glucose which is then transported to the heart and skeletal muscles. 2. Increases metabolic rate and increases energy released in tissue respiration. 3. Increases rate of heartbeat and causes a rise in blood pressure so that oxygen and glucose are transported faster to the muscles. Adrenaline 4. Increases the rate and depth of ventilation. 5. Constricts arterioles in skin causing paleness, thus channeling more blood to muscles. 6. Increases rate of blood coagulation. 7. Causes pupil to dilate to enhance vision. 8. Contracts hair muscles, producing ‘goose bumps’. Lack: 1. Diabetes mellitus (refer to later part of notes) 2. Body becomes weak and continously loses Insulin weight as muscle cells have no store of glycogen. 3. Oxidises fats into ketones to produce energy, ketones removed in urine.
  • 11. Normal: Decreases blood glucose concentration by: i. increasing permeability of cells to take up glucose ii. stimulating liver and muscle cells Insulin to convert glucose to glycogen iii. increase oxidation of glucose in tissue respiration Over: Abnormal decrease in blood glucose concentration. Shock, coma and death may follow. Increases blood glucose level by i. Converting glycogen to glucose Glucagon ii. Converting fats and amino acids to glucose iii. Converting lactic acid to glucose REGULATION OF BLOOD GLUCOSE LEVELS Type 1 diabetes Type 2 diabetesOther names Juvenile, early-onset diabetes Late-onset diabetesSigns Persistently high blood glucose level, presence of glucose in urine, slow healing of wounds.
  • 12. Treatment Insulin injections, diet of sugary Insulin injections, regulation of foods (eg. glucose sweets) carbohydrates, metformin tablets, exercise. Nervous system Hormonal systemInvolve nerve impulses (electrical signals) Involves hormones (chemical substances)Impulses transmitted by neurons Hormones transported in bloodUsually quick responses Usually slow responsesResponses are short-lived Responses may be short- or long-livedMay be voluntary or involuntary Always involuntaryUsually localised Tend to affect more than one target organ