BIO - MOD 8 (NON-INFECTIOUS DISEASE & DISORDERS)

what is homeostasis?

the process of keeping a stable internal environment (e.g. temperature, pH, water/salt balance, glucose levels)

what type of feedback mechanism does homeostasis use?

negative feedback, where the initial change causes the next change to be in the opposite direction

what are the three core components of a feedback loop?

1. receptor (detects change) 2. control centre (processes info) 3. effector (produces response)

what does a receptor do in a feedback loop?

detects a change (stimulus) in the internal or external environment

what does the control centre do in a feedback loop?

processes information from the receptor and sends instructions to the effector

what does an effector do in a feedback loop?

carries out the response that counteracts the change

what is an endotherm?

an organism that maintains a constant body temperature internally through metabolic activity (e.g. humans)

what is an ectotherm?

an organism that relies on the external environment to control its body temperature (e.g. lizards)

what detects changes in temperature?

thermoreceptors

what detects changes in pH or chemical concentration?

chemoreceptors

what detects changes in osmotic pressure?

osmoreceptors

what happens to blood vessels when body temperature increases?

they dilate (vasodilation) to bring blood closer to skin and release heat

what happens to blood vessels when body temperature decreases?

they constrict (vasoconstriction) to keep blood away from skin and conserve heat

what gland coordinates temperature regulation in the brain?

the hypothalamus

what hormone increases the rate of cellular metabolism to produce more heat?

thyroxine (T3 and T4), released after TSH from the pituitary stimulates the thyroid

what is piloerection?

when hair erector cells contract, making hair stand up to trap warm air and reduce heat loss

what is the optimum blood glucose range?

3.5-5 mmol/L

what hormone decreases blood glucose levels?

insulin, released by beta cells in the pancreas

what hormone increases blood glucose levels?

glucagon, released by alpha cells in the pancreas

what does insulin do to glucose in the liver?

stimulates liver cells to convert glucose into glycogen for storage

what does glucagon do to glycogen in the liver?

triggers the breakdown of glycogen into glucose, releasing it into the blood

what is glycogen?

a polysaccharide (large storage molecule) made of many glucose units, stored in the liver

what are the three types of adaptations that help endotherms maintain homeostasis?

behavioural, structural and physiological adaptations

give an example of a behavioural adaptation for temperature control.

moving to shade or sun, migrating, or drinking water

give an example of a structural adaptation for temperature control.

insulation (fur/feathers) or a compact body shape (low SA:V ratio)

give an example of a physiological adaptation for temperature control.

vasodilation/vasoconstriction, sweating, or changing metabolic rate

how does a red kangaroo cool down behaviourally?

licks its forearms so evaporating saliva removes heat, and stays inactive during the day

how does a red kangaroo cool down physiologically?

vasodilation near the skin, panting to lose heat through evaporation from the mouth/nose

what is the central nervous system (CNS)?

the brain and spinal cord, which coordinate information in the body

what is the peripheral nervous system (PNS)?

all the nerves in the body that are not part of the CNS; carries signals to and from the CNS

what type of signal does the nervous system use?

fast electrical impulses carried by neurons

what type of signal does the endocrine system use?

slower chemical signals (hormones) carried in the blood

what gland releases melatonin, and what does it do?

the pineal gland; affects circadian rhythm and reproductive development

what gland releases growth hormone, ADH and gonadotrophins?

the pituitary gland

what does ADH do?

increases water reabsorption in the kidneys

what gland releases thyroxin, and what does it do?

the thyroid gland; controls metabolic rate and glucose use in respiration

what gland releases adrenalin, and what does it do?

the adrenal gland; prepares the body for emergencies by raising heart rate, breathing rate and blood glucose

what does the thymus gland produce, and what does it do?

thymosin; promotes production and maturation of white blood cells

what part of a neuron contains the nucleus?

the cell body

what part of a neuron carries signals away from the cell body?

the axon

what part of a neuron receives signals from other neurons?

the dendrite

what is the myelin sheath?

a fatty insulating layer around some axons that speeds up signal transmission

what is saltatory conduction?

when a nerve impulse jumps between gaps (nodes of Ranvier) along a myelinated axon, making it faster

what direction does a sensory neuron carry signals?

from sensory receptors in the PNS towards the CNS

what direction does a motor neuron carry signals?

from the CNS to effectors (muscles/glands)

what is the role of an interneuron?

links sensory and motor neurons, carrying signals in both directions between them

what is an action potential?

a change in electrical charge across a neuron's membrane that happens once a stimulus reaches a threshold

what happens if a stimulus does not reach the threshold value?

no action potential (and no nerve impulse) is generated

what carries a signal across the synapse to the next neuron?

neurotransmitters released from the axon terminal

how do guard cells open a stoma?

when full of water they become turgid, stretching and pulling apart to open the stoma

how do guard cells close a stoma?

when water levels are low they become flaccid, closing the stoma to reduce water loss

name a plant adaptation that reduces water loss through leaf orientation.

angling leaves away from the sun (e.g. eucalyptus leaves hang vertically)

why do succulents have fleshy leaves/stems?

to store water so they can survive in dry environments

what is the waxy cuticle for?

a waterproof layer on leaves that prevents water loss by evaporation

what causes a genetic disease?

a gene or chromosomal mutation, from inheritance or exposure to a mutagen

what is a single gene abnormality?

a disease caused by one abnormal or mutated gene (e.g. cystic fibrosis)

what is a chromosomal abnormality?

a change in chromosome number or structure, often from non-disjunction (e.g. Down syndrome)

what gene is mutated in cystic fibrosis?

the CFTR gene on chromosome 7

what causes down syndrome?

trisomy 21, an extra copy of chromosome 21 from non-disjunction during meiosis

what are the three main causes of environmentally-caused disease?

lifestyle, physical factors, and chemical exposure

what lifestyle factors cause coronary heart disease?

physical inactivity, smoking, poor diet and high alcohol consumption, causing plaque build-up in arteries

what causes malignant melanoma?

excessive UV radiation damaging the DNA of melanocytes, causing uncontrolled cell growth

what chemical exposure causes lung damage like asbestosis?

inhaling asbestos fibres, which lodge in the lungs and cause inflammation/scarring

what is malnutrition?

an imbalance in diet, caused by either under-nutrition or over-nutrition

what causes iron deficiency anaemia?

not enough iron in the diet, leading to reduced haemoglobin and oxygen transport

what causes obesity?

consuming more kilojoules than the body expends, leading to fat accumulation

what is cancer?

a disease where abnormal cells grow and divide in an uncontrolled way

what genes are damaged to cause cancer?

proto-oncogenes and tumour suppressor genes

what does the brca1 gene normally do?

codes for proteins that help repair DNA and limit cell division (tumour suppressor)

what happens when BRCA1 is mutated?

DNA repair is impaired, allowing excessive cell division and tumour formation

what is incidence?

the number of new cases of a disease in a population over a set period of time

what is prevalence?

the total number of existing cases of a disease in a population at a given time

what is a mortality rate?

the number of deaths from a disease in a population over a set period of time

what is epidemiology?

the study of the patterns, causes and effects of disease in populations

why are epidemiological studies useful?

they help identify risk factors, causes, and trends to guide disease prevention and treatment

what is a risk factor?

something linked to a higher chance of getting a disease, but not necessarily a direct cause

what are the two main types of hearing loss?

conductive hearing loss and sensorineural hearing loss

what causes conductive hearing loss?

a problem in the outer or middle ear that blocks sound vibrations from reaching the inner ear

what causes sensorineural hearing loss?

damage to the inner ear, cochlea hair cells, or auditory nerve

what part of the ear collects sound waves?

the pinna

what part of the ear vibrates when sound waves arrive?

the eardrum (tympanic membrane)

what do the ossicles do?

amplify vibrations in the middle ear and pass them to the inner ear via the oval window

what structure in the cochlea converts vibrations into nerve impulses?

the organ of corti (tiny hair cells)

what detects head movement for balance?

the semicircular canals

what does a cochlear implant do?

replaces the function of damaged hair cells, sending electrical signals directly to the auditory nerve

what does a bone conduction implant do?

bypasses the outer/middle ear by sending sound vibrations through the skull bone to the cochlea

what does a hearing aid do?

amplifies sound vibrations so a partly-functioning ear can detect them better

what is the main function of the kidney?

removes nitrogenous waste and balances water/salt levels in the blood (osmoregulation)

what is the functional unit of the kidney?

the nephron

what happens during filtration in the kidney?

small molecules pass from the glomerulus into the Bowman's capsule, while large molecules stay in the blood

what happens during reabsorption in the kidney?

useful substances (glucose, amino acids, water) move from the tubules back into the blood

what happens during secretion in the kidney?

toxic substances like urea are moved from the blood into the kidney tubules to be excreted

what can cause loss of kidney function?

diabetes, high blood pressure, or recurrent kidney infections damaging the nephrons

what is dialysis?

a technology that filters the blood to remove waste and excess water when the kidneys can't

what is haemodialysis?

filtering blood outside the body using a machine and a dialyser, usually done a few times a week at a clinic

what is peritoneal dialysis?

using the lining of the abdomen (peritoneum) as a natural filter to clean the blood