Module 8.1 and 8.2 Flashcards
What is homeostasis
maintenance of constant internal conditions within narrow limits
Why is Homeostasis necessary
all organisms live in changing environments and need varying degrees of internal stability
enzymes and metabolism require specific conditions:
- pH
- Concentration of Substrate
- Temperature
Effect of Homeostasis not working
cellular damage -> causing disease and eventually death
why does homeostasis stop working
genetic disorders
poor nutrition
aging
Homeostasis examples
when a leaf wilts it reduces further water loss by closing its stomata
when human are dehydrated, urine output decreases and a sense of thirst is experienced
Mammals and birds have the ability to maintain their body temp at a constant level in spite of fluctuating external environmental temperatures a
Tolerance levels in humans
Body temp -> 36 - 37
Carbon dioxide -> 35-45 mmHg
Blood pH -> 75-95mg
Blood glucose levels -> 4-8 mmol
Water balance -> 4.7-5 L in an average human
Control of homeostasis
Endocrine and nervous system
Negative feedback loops
2 stages:
- detecting changes from the stable state
- Counteracting changes from the stable state
In a control system:
- a change (stimulus) occurs
- a receptor picks up the change
- receptor sends information to a control centre (e.g., hypothalamus)
- The control centre sends a signal to an effector (e.g., muscle or gland) to carry out a response
- This response returns the variable to the set value and original state is restored
Negative feedback loop example: Thermoregulation
Stimulus -> Temp too high
Receptor -> Thermoreceptor in the skin
Control centre -> hypothalamus
Effector -> sweat glands, vasodilation
Response -> decrease in body temperature
(refer to pg., 3 M8)
Hypothalamus: description and functions
- small area in brain located centrally
- control centre for regulation of many activities by the body to maintain homeostasis
- sends messages via neural pathways or by hormones to carry out a response
- Hypothalamus is the main link between the nervous system and endocrine system
Vasoconstriction and vasodilation
Vasoconstriction:
- constriction of blood vessels
- reduces heat loss from skin
Vasodilation
- dilation of blood vessels
- increases heat loss from skin
Physiological responses to cold
Piloerection:
- constriction of piloerector muscles around hair follicles -> goose insulation effect of hair -> thick fur traps layer of air
Shivering:
- hypothalamus initiates involuntary muscle movement to release heat
Non-shivering thermogenesis in brown fat:
- Increased cellular activity causes tissues to warm up
Increased metabolism:
- metabolic processes in internal organs release heat
Behavioural responses to cold
Seeking shelter
changing body shape
- decreasing surface area by curling up
Voluntary movement:
- increased movement of muscles releases heat
Change clothing
Physiological responses to Heat
Erector pili muscles
- relax and hairs lie flat
Sweating
- evaporative cooling takes energy from the body
Metabolism
- slowing rate of cellular respiration in internal organs
Behavioural responses to heat
Seeking Shelter
Changing body shape
- standing with legs/arms outstretched
Voluntary movement
- decreased to reduce release of heat
Bathing, swimming, splash body with water
- heat is lost by conduction to the water and then by evaporative cooling
Change clothing
Hyperglycaemia
too high blood glucose level
Hypoglycaemia
Too low blood glucose level
Negative feedback loop for glucose
High glucose:
o After an animal eats, its blood glucose rises
o Chemoreceptor in pancreas detect this rise
o Insulin released from beta cells in pancreas
o Insulin signals to liver to absorb glucose from the blood and convert it to glycogen, fats, or fatty acids for storage
o The blood glucose level is lowered
Low blood glucose:
o When an animal has not eaten, blood glucose levels lower.
o Pancreatic cells detect this drop
o Glucagon is released from alpha cells of the pancreas
o This stimulated the conversion of glycogen to glucose
o This raises blood glucose levels
Xerophyte adaptations
Adapted to dry conditions and conserve water
leaf rolling
leaf orientation -> many species of eucalypt have leaves hang vertically which reduces the amount of direct sunlight they receive, reducing transpiration
Mesophyte adaptations
- have stomata on the underside of leaf and at medium density
- stomata remain open as water supply constantly available
Not drought tolerant
Hydrophyte adaptations
Not all plants need to conserve water
- adaptations avoid tissue flooding:
- spongy mesophyll layers
no stomata on lower epidermis
higher number of stomata on upper surface to maximise water loss
Endocrine system
- Series of glands that produce hormones that regulate the activity of cells or organs
- hormones are transported via the circulatory system in animals and diffusion in extracellular fluid in plants
- Hormonal responses are slower and more indirect than nervous system, but effects last longer and target a wide variety of cells
Hormones
A diverse group of commands that act as intercellular messengers to regulate cell functions
target organs have specific receptors for hormones
A single hormone can trigger different responses in multiple target cells at the same time.
Endocrine glands: pituitary gland
- ‘Master gland’ of endocrine system
- works with hypothalamus to ensure homeostasis
- several pituitary hormones act to regulate the secretion of hormones from other glands (e.g., thyroid, testes)
- anterior section secretes hormone that controls growth
- posterior section secretes antidiuretic hormone (ADH) which helps to regulate the concentration of water in the body
Nervous system
Works with endocrine system to respond to changes and regulate internal environment
- contains millions of neurons which transmit messages via electrical impulses
- more direct than hormonal response
- control by nerves is usually rapid, short in duration and precisely located
- central nervous system and peripheral nervous system
Central nervous system
The brain and spinal cord act as a control centre and coordinates for all the organism’s responses
It receives information from receptor cells, interprets the information and initiates a response
contains:
- relay neurons (interneurons)
Peripheral nervous system
- consists of a system of nerves that branch throughout the organism to and from receptors and effectors
- receptor cells receive images and sounds from stimuli and send them to the brain by nerve impulses in neurons
Composed of:
- cranial nerves
- spinal nerves
- peripheral nerves
Contains:
- sensory neurons
- motor neurons
Neurons
Specialised cells with structures that enable rapid transmission of information between cells
- collection of neurons is called a nerve
consist of three main parts:
- the dendrite -> receives information and conveys it to cell body
- the cell body -> houses the nucleus
- The axon -> projection of the cell that carries electrical impulse down its length toward axon terminal and synapse
Types of neurons
Sensory neurons:
- have dendrites in receptor organs and axons in CNS
Interneurons:
- found in CNS and connect sensory neurons to motor neurons
Motor neurons:
- have dendrites in the CNS and axons at effector organs, e.g., muscles, glands
importance of myelin sheath
Allows information to jump down the neuron -> more efficient
when myelin sheath is damaged, nerve impulses slow or stop completely -> causes neurological disorders
MS (multiple sclerosis) attacks Schwann cells which produce and maintain myelin
What is an arc reflex
Involuntary response to a stimulus
How does nerve impulse travel from neuron to neuron
nervous impulse is electrochemical:
- electrical impulse is also known as action potential and occurs along cell membrane, mostly along axon
- chemical transfer of an impulse occurs in junction between two neurons: the synapse. In this junction chemicals called neurotransmitters ‘translate’ the electrical impulse message in a chemical message between cells
impact of THC (cannabis) on neural transmitters
low doses inhibit release of glutamate in amygdala
high doses inhibit GABA neurons, glutamate builds up, activating amygdala
monogenic diseases
causes by a mutation in a single gene
inherited from parents
defective gene can occur in one of the sex-chromosomes = ‘sex-linked’ disease
example: cystic fibrosis, albinism
Chromosomal abnormalities
caused by changes in chromosomes
Aneuploidy:
- incorrect number of chromosomes (e.g., monosomy (only 1 instead of 2) or trisomy (an extra chromosome))
Deletion:
- addition or altered section of a chromosome
Translocation:
- section of chromosome moves to join another different chromosome
Examples: Down syndrome
Nutritional diseases
caused by a lack of, or too many nutrients
Nutrients:
- minerals
- vitamins
- animo acids
- fatty acids
Cancerous diseases
a group of diseases that involve unregulated and uncontrolled cell growth and division
cancerous cells are undifferentiated (lack of specific function
Metastasis
when cancerous cells that spread to other tissues of the body
Cause of cancers
- genetic mutations in cells that increase the rate of cell division and/or suppression of apoptosis
Risk factors:
- tobacco smoking
- alcohol consumption
- diet
- obesity
- radiation
- exposure to other carcinogens
Effect of cancer
leads to growth of malignant tumours
primary tumour cells can travel via the blood or lymph to new organs to form a secondary tumour
Start of cancers
mutation occurs in a gene that controls cell cycle:
DNA repair gene:
- code for proteins that remove replace damaged regions of DNA
Proto-oncogene:
- code for proteins that stimulate cell growth and mitosis.
- if mutated it is called an oncogene -> causes uncontrolled mitosis and prevents cells death
Tumour suppressor gene:
- code for proteins that stop cells growth and mitosis -> they induce cell death.
- if mutate, cell death is not regulated
Sarcoma
Forms in muscle or connective tissue
Types of cancer
Sarcoma
carcinoma
lymphoma and myeloma
leukemia
central nervous system cancers
Carcinoma
Forms in epithelial tissue: skin or tissue that lines internal organs
Lymphoma and myeloma
Forms in the lymphatic system and plasma cells
Leukaemia
forms in bone marrow (blood producing cells)
Central nervous system cancers
Brain or spinal cord nerves
Cancer treatments
Surgery
Chemotherapy
- uses chemicals
Radiation:
- uses photons to treat a focal area of cancer
envirnmental diseases
immune system incorrectly reacts to antigens that are normally harmless e.g., pollen, peanuts
Cause of environmental diseases
Immunoglobin E is produced by plasma in response to allergen
immunoglobin E binds to receptors on mast cells
The allergen binds to a pair of adjacent immunoglobin molecules and trigger a cascade of cellular signals that cause the mast cells to release histamine
Histamine causes an inflammatory response
UV radiation skin cancer types
Basal cell Carcinoma
Squamous Cell Carcinoma
Melanoma (most malignant)
Effect of exposure to chemicals
Mutagens:
- cause irreversible and heritable mutations in DNA e.g., hydrocarbons
teratogens:
- Causes developmental errors in the foetus leading to birth defects. E.g., warfarin (anticoagulant)
Carcinogen:
- proven to cause cancer e.g., asbestos
Poisons:
- cause illness or death when consumes in small quantities or accumulated in the body e.g., lead, alcohol, drugs
Endocrine disruptors:
- interfere with endocrine system (hormones) causing tumours, birth defects or developmental disorders e.g., dioxin, pesticides
