Homeostasis and Feedback Loops

Homeostasis

• Homeostasis maintains a stable internal environment despite external changes.
• A stimulus (change) is detected by receptors, which convert it into a nerve impulse.
• The control center (brain/spinal cord) receives the impulse.
• A messenger communicates a message from the central nervous system to an effector.
• The effector receives the message and causes a response, resulting in a change in the body.
• Malfunctions in homeostatic mechanisms can lead to diseases like hyperglycemia/hypoglycemia (diabetes), or hypothermia/hyperthermia (heat stroke, pneumonia, etc.).

Temperature Feedback Loop

• In response to detecting cold, thermoreceptors in the skin send a signal to the hypothalamus (control center).
• The peripheral nervous system triggers shivering and vasoconstriction as a response, aiming to stabilize body temperature.
• In response to detecting heat, thermoreceptors in the skin send a signal to the hypothalamus (control center).
• The peripheral nervous system initiates panting, vasodilation, and sweating to cool the body down and restore stability.

Glucose Feedback Loop

• After a fall in blood glucose levels (BGL), sensor cells in the pancreas act are receptors.
• Alpha cells in the pancreas release glucagon.
• Glycogen converts to glucose as a response, increasing BGL to stability.
• After a rise in BGL, sensor cells in the pancreas act as receptors.
• Beta cells in the pancreas release insulin.
• The liver absorbs glucose from the blood as a response, decreasing BGL to stability.

Animal Adaptations for Homeostasis

• Animals exchange heat with the environment through conduction, convection, radiation, and evaporative cooling.
• Endotherms produce their own body heat via metabolism e.g. mammals and birds.
• Ectotherms obtain heat from the external environment e.g. fish, reptiles, invertebrates.
• Structural adaptations relate to an organism's size, shape, and body parts.
• Examples include kangaroos with a network of veins under thin forelimb skin and body proportions suited to climate.
• Physiological adaptations manage body works; like temperature regulation via vasoconstriction, vasodilation, sweating, and hormonal control of water levels.
• Behavioral adaptations alter behaviors, these include snakes seeking sun or shade, kangaroos licking forelimbs to promote evaporative cooling and penguins huddling for warmth.

Plant Adaptations for Water Balance

• Xerophytes are adapted to live in dry conditions with features to minimize water loss from transpiration.
• Tough cuticles of pigface are thick and waxy, so the surface reduces transpiration.
• Fine hairs of paper flowers create a humid environment around stomata, reducing water loss.
• Water storage in pigface allows leaves and stems have large vacuoles to store water.
• Pigface have extensive root systems that absorb and store large amounts of water.
• Rolled-up leaves like porcupine grass curl up when too much water is lost, creating a humid chamber for the stomata.
• Stomata is only on one side of the leaf so none are exposed when curled.
• Wattles lack leaves and have flattened stems (phyllodes) instead to allow photosynthesis but lack stomata, reducing transpiration.
• Angled branches and leaves of mulga trees angled down to direct water to the roots and minimize sun exposure.
• Transparent leaves of firewheel trees don’t absorb as much heat, slowing water loss.

Endocrine System

• Hormones are signalling molecules that regulate the activity of specific target cells, interacting with specific receptors.
• Endocrine glands typically release hormones directly into the circulatory system e.g. the pituitary gland.

Nervous System

• Sensory neurons receive information and send it to the central nervous system (CNS).
• Motor neurons relay signals from the CNS to muscles or glands.
• Interneurons connect sensory neurons to motor neurons within the CNS.
• Neurotransmitters (e.g., noradrenaline) are signaling molecules released by nerve cells that communicate electrical signals to chemical signals across a synapse.
• Presynaptic knobs contain vesicles that release neurotransmitters
• Impulses cannot travel across synapses.
• Neurotransmitters bind to receptors and stimulate dendrites to begin action potential in the next neuron.

Action Potentials (Nerve Impulses)

• Action potential involves a change in polarity on the inside of the neuron, compared to the outside, when the neuron is stimulated.
• Action potentials involve traveling electric current caused by ions moving through voltage-gated channels.
• Resting potential has a negative charge inside, relative to the outside of neurons
• Sodium ions sit outside, and potassium ions sit inside.
• In the steps:
  • The cell membrane of the neuron is stimulated, becoming permeable to sodium (Na+) ions, which enter.
  • Potassium (K+) ions move out, and the resting potential is restored.
  • The resulting depolarization adjacent to the initial action potential stimulates a new AP as Na+ ions enter, causing AP to continue moving along the neurone.
• The threshold is the minimum intensity of a stimulus needed to initiate a response.
• Intensity is recorded by the rate at which APs are generated.
• Stronger stimuli create more rapid firing and an increase in the number of cells responding.
• The frequency that changes causes different responses, while speed and strength of APs remain constant.

Infectious vs Non-Infectious Diseases

• A disease is any condition that impairs normal body functioning.
• Non-infectious diseases aren't about contagion. Non-infectious diseases can be passed on generationally e.g. germline mutations.
• Infectious diseases are caused by a pathogen.
• Contagious diseases are able to spread from person to person.
• E.g., Tetanus is infectious (soil bacteria) but not contagious.

Genetic Diseases

• Genetic diseases occur due to changes in DNA sequence, like mutation
• Haemophilia, a blood disorder due to the blood clotting gene, shows symptoms like frequent/uncontrollable/unexplained bleeding and is treatable with medication.

Environmental Diseases

• Environmental diseases are illnesses caused by various environmental factors
• Exposure to UV radiation, chemicals, or lifestyle factors can cause these.
• Lead poisoning affects the brain and nervous system, caused by prolonged exposure to lead-contaminated sources.
• Lead poisoning is treatable with medication to help remove lead from the body, developmental delays, abdominal pain, and neurological changes are symptoms.
• Environmental Disease prevention involves limiting exposure and using protective gear e.g. sunscreen.

Nutritional Diseases

• Nutritional deficiencies are a result of insufficient nutrient intake or the body's inability to absorb nutrients.
• Anaemia, caused by insufficient iron intake or absorption, leads to iron deficiency and slowed red blood cell production.
• Symptoms include fatigue, fainting, paleness, and poor circulation.
• Treatment is with iron supplementation, changes in diet, or iron infusions.

Cancers

• Cancer is a group of diseases like skin, breast, and lung diseases; Abnormal cells multiply and spread (metastasize).
• Cancer is not easily categorized since the causes are broad.
• Environmental exposures like smoking can cause lung cancer but can occur for non-smokers.
• Diseases like breast cancer has a genetic predisposition (BRCA1 & BRCA2) but may occur without genetic factors.

Environmental Disease: Melanoma

• Melanoma, the most lethal type of skin cancer, shows that UV radiation e.g. sunlight, age, sunburns and genetics, influence its cause.
• Those with fair skin are more prone to melanoma.
• Symptoms include tumours/growths, changes in existing moles e.g. getting darker or larger, swollen lymph nodes and changes in skin pigmentation.
• Treatments are surgery (removing melanoma and the surrounding cells), chemotherapy and radiotherapy.

Kwashiorkor

• Kwashiorkor originates from Ghana (older child gets sick when the next baby is born).
• Severe Protein Deficiency from a younger child (older child that doesn't drink breast milk) or any breast milk leads to a protein deficiency and, therefore, Kwashiorkor.

Patterns of Disease (Epidemiology)

• Epidemiology studies the causes, effects, and patterns of diseases in populations.
• Aids in the management, evaluation, and planning of services for prevention, control, and treatment of diseases.
• Data and indicators can be collected from sources like hospitals, insurance claims, GPs and health surveys.
  • Incidence = new cases of a disease in a population.
  • Prevalence = the proportion of affected individuals in a population (measure morbidity).
  • Mortality = number of deaths from the disease.
• Linking Smoking and cancer showed test groups the higher risk.

Treatment and Future Directions

• Treatment and cure depend on the disease type.
• Scurvy treatment is vitamin C.
• Screening and early diagnosis are useful in diseases with limited treatment options.
• CF has no successful treatment and focus on symptom reduction.
• CF and other diseases get resources spent on treatment and how contribute to bodily systems.

Epidemiology Questions

• Epidemiology is conducted to discover patterns that establish links between cause and effect and develop programs to prevent and control disease.
• Epidemiology helps understand who gets sick, why, and what the most effective treatment is.
• Epidemiology develops programs e.g. vaccination programs, identify people at risk and allocate money.

Types of Epidemiological Studies

• Descriptive studies tell the who, what, where, and when.
  • Generate hypotheses about causes of disease.
• Analytical studies test hypotheses and provide the why/how.
  • Determine the causes of diseases.
• Intervention studies tests effectiveness of treatments/campaigns.

Errors in Epidemiological Studies

• Random errors are unpredictable data variations; make a study less precise but don’t bias results, with differing groups.
• Homogeneous groups and statistics correct random errors.
• Systematic errors (bias) have consistently skewed stats.
• Study bias can stem from selection bias, volunteer bias, healthy worker bias and prevalence/incidence bias & requires representative demographics.
• Information bias errors can be by-way of misclassification bias, recall bias, loss to follow up bias and interviewer bias & relies on accuracy.

Benefits of Using Epidemiology

• It identifies causes (like smoking and lung cancer).
• Public health authorities use data to manage & plan strategies to treat and improve health.

Prevention & Evaluation of Anti-Smoking Campaigns

• It helps treat chronic conditions.
• Prevention encompases many activities with aims of, reducing liklihoods of disease for indiviuals, slowing the spread and reducing disability.
• Methods like Mammograms, sunscreen, the HIV PrEP and Nationtal Tobacoo strategy are considered "preventative actions".
• An example of preventive action; National Tabacco Strategy and educative campigns.

Genetic Engineering

• Involves artificial modifcatons of DNA.
• Exampels include , the Golden Rice, CRISPR cas9, pre-implantaton screeng (IVF) and, GE insulin

Gene therapy

• It involves techniques to treat or prevent diseases at the source by manipulating genes, modifying faulty genes.
• It only targets body cells, not passed onto offspring.
• It helps treat incurable conditions like haemophilia and cystic fibrosis (CF) by replacing faulty genea.
• Missing genes are placed in a modified virus & inhaled by the patient.

Disorders

• They are disturbances that impact the mind/body.
• They can be due to intrinsic issues (genetic), trauma, ageing or environmental actors.

Function and Structure of Ear.

• The eardrum is composed of three chambers and contains the nerves responsible for sending messeges to the brain.