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Biology Module 8 > Module 8.1 and 8.2 > Flashcards

Module 8.1 and 8.2 Flashcards

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1
Q

What is homeostasis

A

maintenance of constant internal conditions within narrow limits

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2
Q

Why is Homeostasis necessary

A

all organisms live in changing environments and need varying degrees of internal stability

enzymes and metabolism require specific conditions:
- pH
- Concentration of Substrate
- Temperature

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3
Q

Effect of Homeostasis not working

A

cellular damage -> causing disease and eventually death

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4
Q

why does homeostasis stop working

A

genetic disorders
poor nutrition
aging

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5
Q

Homeostasis examples

A

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

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6
Q

Tolerance levels in humans

A

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

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7
Q

Control of homeostasis

A

Endocrine and nervous system

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8
Q

Negative feedback loops

A

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

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9
Q

Negative feedback loop example: Thermoregulation

A

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)

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10
Q

Hypothalamus: description and functions

A
  • 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
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11
Q

Vasoconstriction and vasodilation

A

Vasoconstriction:
- constriction of blood vessels
- reduces heat loss from skin

Vasodilation
- dilation of blood vessels
- increases heat loss from skin

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12
Q

Physiological responses to cold

A

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

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13
Q

Behavioural responses to cold

A

Seeking shelter

changing body shape
- decreasing surface area by curling up

Voluntary movement:
- increased movement of muscles releases heat

Change clothing

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14
Q

Physiological responses to Heat

A

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

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15
Q

Behavioural responses to heat

A

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

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16
Q

Hyperglycaemia

A

too high blood glucose level

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17
Q

Hypoglycaemia

A

Too low blood glucose level

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18
Q

Negative feedback loop for glucose

A

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

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19
Q

Xerophyte adaptations

A

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

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20
Q

Mesophyte adaptations

A
  • have stomata on the underside of leaf and at medium density
  • stomata remain open as water supply constantly available

Not drought tolerant

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21
Q

Hydrophyte adaptations

A

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

22
Q

Endocrine system

A
  • 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
23
Q

Hormones

A

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.

24
Q

Endocrine glands: pituitary gland

A
  • ‘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
25
Q

Nervous system

A

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
26
Q

Central nervous system

A

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)

27
Q

Peripheral nervous system

A
  • 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

28
Q

Neurons

A

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

29
Q

Types of neurons

A

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

30
Q

importance of myelin sheath

A

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

31
Q

What is an arc reflex

A

Involuntary response to a stimulus

32
Q

How does nerve impulse travel from neuron to neuron

A

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

33
Q

impact of THC (cannabis) on neural transmitters

A

low doses inhibit release of glutamate in amygdala

high doses inhibit GABA neurons, glutamate builds up, activating amygdala

34
Q

monogenic diseases

A

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

35
Q

Chromosomal abnormalities

A

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

36
Q

Nutritional diseases

A

caused by a lack of, or too many nutrients

Nutrients:
- minerals
- vitamins
- animo acids
- fatty acids

37
Q

Cancerous diseases

A

a group of diseases that involve unregulated and uncontrolled cell growth and division

cancerous cells are undifferentiated (lack of specific function

38
Q

Metastasis

A

when cancerous cells that spread to other tissues of the body

39
Q

Cause of cancers

A
  • 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

40
Q

Effect of cancer

A

leads to growth of malignant tumours

primary tumour cells can travel via the blood or lymph to new organs to form a secondary tumour

41
Q

Start of cancers

A

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

42
Q

Sarcoma

A

Forms in muscle or connective tissue

43
Q

Types of cancer

A

Sarcoma

carcinoma

lymphoma and myeloma

leukemia

central nervous system cancers

44
Q

Carcinoma

A

Forms in epithelial tissue: skin or tissue that lines internal organs

45
Q

Lymphoma and myeloma

A

Forms in the lymphatic system and plasma cells

46
Q

Leukaemia

A

forms in bone marrow (blood producing cells)

47
Q

Central nervous system cancers

A

Brain or spinal cord nerves

48
Q

Cancer treatments

A

Surgery

Chemotherapy
- uses chemicals

Radiation:
- uses photons to treat a focal area of cancer

49
Q

envirnmental diseases

A

immune system incorrectly reacts to antigens that are normally harmless e.g., pollen, peanuts

50
Q

Cause of environmental diseases

A

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

51
Q

UV radiation skin cancer types

A

Basal cell Carcinoma

Squamous Cell Carcinoma

Melanoma (most malignant)

52
Q

Effect of exposure to chemicals

A

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

Biology Module 8 (2 decks)

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