B5 science notes

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cord. 4.) A relay with a motor neurone neurone synapses 5.) A motor neurone Carries an impulse to the effector contract and pull the foot up simulated by motor neurones. and away Neurones the Reflex Are of Receptor Cells - Axon Cell Body Myelin Sheath Cell Body Replex Arc Sensory Neurones -Sensory from Sense These are branching off - Schwann Cells - Relay CNS and connects -They Axon at one end with Nodes of Ranvier at neurones carry impulses to CNS. Relay Neurones organs long and have the middle a cell body the ax of neurones are found inside the axon and motor neurones. Sensory are short and have a small cell body. dendrites branching off many it Dendrite - Axon Motor Neurones -Motor neurons carry impulses from the CNS to effector (muscle or glands) -They one are long and have a large cell body end with long dendrites branching off Synapses •Neurones never called synapses. Synaptic junctions are Small and electrical impulses can very them ● Vesicles Containing Neurotransmitters Synaptic Clept Reflex Arc not cross •In a replex arc, there are synapses relay neurones, and the relay and motor neurones. •Chemicals called neurotransmitters are released into the Synaptic cleft and diffuse across it (down the concentration gradient). Key: ●= Sensory Neurone = Relay Neurone ●= Motor Neurone touch, they are seperated by Juctions (gaps) continued stimulation Presynaptic Membrane Postsynaptic Membrane Neurotransmitter Receptor Molecules •Synapses •This is the only affect the nervous system. between the the sensory and •The electrical impulse travels along the first axon. •When an electrical impulse arrives at the end the of on the presynaptic neurone, neurotransmitters are released from vesicles •Neurotransmitters diffuse across the synaptic gap and bind with receptor molecules on the postynamic membrane. •This stimulates the 2nd neurone to that travels down the 2nd axon. Neurotransmitter generate an electrical_impulse are then destroyed or recycled to prevent ensure that impulses only travel in one direction only place in the body where drugs. can act to axon Synapses 2 Neurotransmitters in Vessicles ready for next impulse. membrane. 5.) This triggers neurone. an Reflex Arc 6.) Neurotransmitters impulse is sent. Presynaptic Neurone Synaptic Cleft Ostsynaptic Neurone Presynaptic Neurone -Post Synaptic Neurone 1.) An impulse arrives at the end the of presynaptic 2.) Vesicles move towards and fuse with the presynaptic membrane. This releases neurotransmitter into the synaptic cleft. 3.) The neurotransmitters diffuse across the synaptic cleft. 4.) Neurotransmitters attatch to receptor on the postsynaptic impulse which travels along the postsynaptic are recycled or destroyed 6 4 neurone once an Reaction Time •Reaction time is the time taken to respond to a stimulus. •Reaction time can be affected by factors such as age, stress or use of drugs (such as caffeine) •You could investigate the effect of background consumtion of caffiene on how quickly noise or person catches 0 a ruler. are •In the ruler drop experiment there. variables that should be considered in this -The person catching the ruler using their dominant hand. -Dropping the same ruler orientated in the same direction. •Reaction time can also be recorded in milleseconds which is more accurate than seconds. many control experiment such as: The Brain •The brain alongside the spinal cord is part of our CNS. •The brain is made billions of and interconnected neurones of is responsible for controlling complex behaviours •Within the brain are diffrent regions that out diffrent carry functions. Structure Scientists have discovered that diffrent regions of the brain seem to be responsible for controlling diffrent functions. These include: The cerebral cortex - This is the outerlayer of the brain. which is divided into two hemispheres. It is responsible for order process memory, consciousness and personality. The cerebellum - This is under the cerebral cortex. It is responsible for balance, muscle coordination and movement. The medulla-This region controls unconcious activities such as heart rate and breathing. Cerebral Cortex Hypothalamus- Pituitary Gland- such as intelligence, Cerebellum -Spinal Cord Medulla The Brain Mapping Regions of the Brain Neuroscientists have been able to the the map regions of brain to particular functions, by studying patients with brain damage, electrically stimulating diffrents parts and using MAI scanning techniques •Patients with brain damage can be studied to see what effect it has on them physically, capabilities their personality -Phineas Gage large metal destroyed, rod A rail road construction worker who survived a going through his head - his frontal left lobe was his personality and temperment changed drastically. Tiny electrodes can be pushed into diffrent parts of the brain, liny jolts of electricity stimulate these regions and effects can be or • Mri scans are a very important diagnostic tools used to study the brain and other regions of the body using magnetic fields and the effect these have on protons in the water molecules the body of - Functional MRIs can produce images of diffrent regions the brain that are active during diffrent activities like listening to music or recalling memory of The Eye function • The eye is a sense organ containing receptor sensitive to light intensity and colour. • Receptors an electrical impulse in a Sensory neurone. •The eye contains two types of receptor cell: rod cells, are sensitive to light intensity and cone cells which are sensitive to diffrent wavelenghs of visible light which are groups of specialised cells that can generate Cornea Iris Lens Retina Structure of •The purpose of eye is to recieve the light and focus it onto the retina at the back of eye •The retina is where the rod and cone cells are located Structure function Transparent lens that retracts light as it enters Controls how much light enters the pupil Transparent discs that can change shape Contains light receptar calls Optic Nerve Pupil the Eye the Sensory neurone Hole that allows light to enter the eye that carries impulses to the brain Suspensory Ligament Cornea Iris Pupil Lens Ciliary Muscle -Sclera -Retina -Fovea Optic Nerve The Eye The Pupils Reflex •This is carried out to protect the retina. from damage in bright light and protect object in dim light. not us from seeing •The replex action is controlled by 2 groups of muscle; the radial muscle and the Circular muscles into the •In dim light, the pupil dilates, in order to allow as much light eye as possible •In bright light, the pupil constricts, in order to prevent too much. light entering and damaging the retina. the eye Circular Stimulus Radial Muscle Muscle Dark light Contracted Relaxed Bright light Relaxed Contracted Wide Narrow Amount of More Less near focus on •The ciliary muscles contract •The suspensory ligaments loosen The lens is then thicker and refracts light Near Object 2 Suspensory Ligaments Slacken 2 The Eye Suspensory Ligaments Contract thin objects 1 Ciliary Muscle Contracts focus on distant objects •The ciliary muscles relax •The suspensory ligaments • Lens is pulled thin and only slightly refracts light. are pulled tight Lens becomes fatter Cilliary Muscle Relaxes 3 Lens becomes Thinner 3 The Eye the eye are myopia (short- sightedness) and hyperopia (long-sightedness) in which rays of light do not the retina focus on • Generally, these defects are treated with glasses Myopia Defect of •Two common defects of the Lens is too thick and Curved eye Eyeball is too elongated Image is in focus in front of the retina Image is brought into focus behind the retina -Eyeball is too short Hyperopia 10 Concave lens corrects rays 。 they focus on the retina So Image on retina Image on retina -Convex lens refracts light rays Control of Body Temperature Monitoring of body temprature •The human body needs to maintain a temprature that enzymes work best at (37°c). •Process such as respiration releases energy body loses heat to its surroundings energy • Body temprature is monitored and controlled thermoregulatory centre in the brain •The thermoregulatory centre contains receptors sensitive to the temperature of the blood •The skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre. Muscle Capillaries Sweat gland - Arteriole Sweat pore Muscles - Hair free nerve endings (Sensitive) -Epidermis -Dermis -Sensory fatty tissue neurone as heat; and the by the Control of Body Temperature High temperature •If body temperature is too high, blood vessels dilate and sweat is produced •Both of these mechanisms cause a tranfer of energy from skin to the enviroment, cooling the body down Low temperature • If body temprature is too low, blood vessels constrict, sweating stops and skelatal musdes contract (shiver) •These mechanisms reduce heat loss to the surroundings. Homeostasis • Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes •Homeostasis maintains optimal conditions for enzyme and all cell function for enzyme action •In the human body these include control of: -Blood glucose concentration -Body temperature -Water levels Control Homeostasis of is • Maintaining controlled conditions within the body under involountary control. • This means that the brain stem and spinal cord are involve nervous involved in maintaining homeostasis. •These automatic control systems or chemical responses systems may responses • All control systems include: -Cells called receptor, which detects stimuli -Coordination centres that receive and process information from receptors · Effectors which bring responses which restore optimum levels. Endocrine System function •The human endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream. •The blood carries the hormone around the body, and when it reaches a target cell/organ it produces an effect "Compared to nervous system the effects of hormones. are slower but they acted for longer. Structure Pituitary gland -A 'master gland' :- A 'master gland' making hormones such as •Pancreas-Produces insulin which regulates the blood glucose level • Thyroid - Produces thyroxine which controls metabolic rate and affects growth. • Adrenal glands-Produces adrenaline. •Ovaries (female)-Produces oestrogen" •Testes (male)-Produces testosterone Hypothalam Phuitary Gland -Cerebral Carter Medalla Thyroid -Speel Cand Gland- Pancreas. Testes- Xx A or -Pituitary Gland -Adrenal Glands -Ovaries Endocrine System Pituitary Gland Pituitary gland which secretes several hormones into the blood in response to body conditions. •These hormones in turn act on other glands to simulate other hormones R Pancreatic Gland Cells Blood Capillary A -Liver -Pancreas Dost D.D Receptor AAAADA ΔΔΔ Andr -Hormone Control of Control of blood glucose • Blood glucose concentration is monitored and controlled by the pancreas and is an endocrine gland and plays a vital role in digestion. blood glucose concentration •Blood glucose concentration must be kept within a range, so it's another example of homeostasis. narrow Eating foods containing carbohydrate results in an increase of glucose into the blood stream • If the blood glucose concentration is too high, the pancreas produces the hormone -A too high level of glucose in the blood body losing water by osmosis Insulin stimulates cells to take in stream. in the blood can lead to cells of glucose from the blood the of blood glucose concentration Diabetes the cells of the Type One Diabetes -A disorder in which the pancreas fails to produce sufficient insulin to control blood glucose levels. Scientists think this is result of a person's own immune system destroying pancreas that make insulin during development. Type Two Diabetes - Body cells no longer responds to insulin produced by the pancreas - the person cells are resistant to it and don't should. still makes insulin but their respond as well as they C Control Cause Treatment Type One Inability of pancreas produce insulin to Monitoring blood glucose levels and injecting insulin through out the day Type Two Cells the body ressistant to insulin of become Maintain a low-carbohydrated diet and regular to reduce need exercise for insulin Water Loss in the Body • Maintaining water levels in the body is vital to prevent the body. of occuring to cells too much water by gain or harmful changes •If body cells lose they do not function efficiently. - Too much water in the blood results in cells swelling as water moves into them, this has a diluting effect and can lead to cell lysis (bursting) -Too little water in the blood (or too high an ion concentration) and the cells lose water by osmosis, this has a dehydrating effect and can lead to cell death There two are Sources of -Water produced as a result -Water in the diet •The cytoplasm of the blood plasm. • Water is lost Organ Excretes carbon Lungs dioxide water in aerobic of the body; Explanation The lungs excrete carbon dioxide during exhalation osmosis all cells is largely composed of water, as is the body in the following ways: from -Water leaves the body via the lungs during exhalation -Water, ions and urea lost are from the skin in sweat. • However, the lungs and skin have no control over how much water, ion or urea is is lost via exhalation or sweating. The Kidney excrete water, sallts Excess water, Kidneys Salls and wrea and urea by producing urine respiration -Lungs Liver -Kidney