4a learing objectives

Question 1

Define homeostasis and list the types of bodily conditions that are regulated by homeostatic mechanisms; define endotherm and ectotherm.

Answer 1

Homeostasis - the ability of an organism to maintain its internal environment within narrow limits that allow optimal cell function.
Endotherm - produced most of their heat through metabolic reactions.
Ectotherm - derive most of their heat from the environment (reptiles, amphibians, invertebrates and most fish)

Question 2

Explain the roles of positive and negative feedback in maintaining a constant internal environment .

Answer 2

Positive - creates cycles of which changes amplify themselves.
Negative - which counteract the internal changes, this is the basis for homeostasis. There are three principles , Sensor, Control centre (hypothalamus) , Effector.

Question 3

Describe the organisation of the animal body into functional units of increasing size and complexity (i.e. cells, tissues, organs, organ systems).

Answer 3

Cells - fundamentals
Tissues - similar cell working together to perform single function
Organs - structures that compete complex functions and have two or more varying tissue types.
Organ system - groups of organs that are coordinated to each perform a specific task that is apart of a larger task

Question 4

List the major tissue systems in the animal body and the types of cells that comprise them: epithelial tissue, connective tissue, muscle tissue, and nerve tissue.

Answer 4

Epithelial tissue - line ducts and hollow organs as well and external surfaces. Made from simple epithelium (one cell thick) , stratified epithelium (more layers) , squamous cells (flat and thin) Cuboidal cells (cube shaped) Columnar cells (elongated)
Connective tissue - supports and aids in binding tissues. Loose connective tissue (fat) dense connective made from collagen fibres parallel (tendons, ligaments) specialised tissue (cartilage, bone, fat, blood, lymph)
Muscle tissue - can contract they are skeletal (voluntary) , cardiac (heart involuntary and made from intercalated discs) and smooth (not striped, involuntary)
Nerve tissue - neurons (dendrites, cell body, axon and terminals) and glial cells which support electrical insulate and protect neurons as well as regulate composition of interstitial fluid.

Question 5

Define the terms organ and organ system.

Answer 5

Organ - structures that compete complex functions and have two or more varying tissue types.
Organ system - groups of organs that are coordinated to each perform a specific task that is apart of a larger task

Question 6

List the four major methods by which cells communicate with each other (direct, synaptic, paracrine, endocrine) and the general mechanism by which endocrine hormones communicate with their target cells.

Answer 6

Direct - direct contact, ions flow from each cell by gap junctions (cardiac cells)
Synaptic - chemicals released by cells diffuse through extracellular fluid, transmits electrical signals to each cell (neurotransmitters) (nervous system)
Paracrine - chemicals released by cells diffuse through extracellular fluid, effects are short - local hormones (prostaglandins)
Endocrine - chemicals secreted through the bloodstream, (insulin)

Question 7

List the three major classes of vertebrate endocrine hormones and describe how these different hormone types affect changes in their target cells.

Answer 7

Steroid hormones - synthesised from cholesterol they are lipid soluble so they can diffuse through plasma membranes, they bind to receptor cells inside target cells. (testosterone, oestrogen, progesterone.)
Peptide hormones - chains of amino acids , which cannot diffuse through the bilayer, they must bind to receptors on the cell surface. (thyroxine, Melatonin.)
Amino acid derived hormones - made of amino acids they also bind to receptors on the cell surface. (growth hormone, Insulin, Leptin.)