BIOL10002 Lecture Notes - Lecture 10: Cell Signaling, Adipocyte, Connective Tissue
Lecture 10: Tissues & homeostasis
Tissue types:
● Multicellular animals are composed of four tissue types and most organs contain one or more types of tissues e.g. small intestine
● Organs are organized into functional physiological systems
Tissue: cellular level between cells & a complete organ, an ensemble of similar cells & their ECM from the same origin, carry out a specific function
Histology: the study of tissues and organs at the cellular (microscopic) level
Organ: a part of an organism which is typically self-contained & has a specific vital function, composed of multiple tissue types
Types of cells: cells arranged in organs, organs composed of tissues: 4
tissue types
● fat cell
● neuron
● macrophage
● smooth muscle cell
● glial cells
1. Epithelial tissues
densely packed and tightly connected; create boundaries between the
internal and external environment and between compartments
line blood vessels, various tubules and ducts
first defence against disease
functions:
● creates barriers and regulates transport across those barriers
● may be involved in secretion and absorption
● may be involved in smell and taste
types:
● squamous (flattened)
● columar (tightly packed, can have cilia, polarized (either end
of that cell is different), can have absorptive/secretory
function
● cuboidal
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2. Muscle tissues generate force and movement
Most abundant tissue in body
Contain long filaments of myosin and actin - allow muscles to contract
and exert force
3 types of muscle tissue:
skeletal muscle (attached to bone): regular arrangement of actin and
myosin filaments result in striped (striated) appearance; under voluntary
control
cardiac muscle (heart): involuntary control; branched cells form strong
structural meshwork responsible for beating and contracting heart
smooth muscle (forms the outer walls of hollow internal organs e.g.
stomach, bladder, blood vessels): lack of striated appearance;
gastrointestinal tract (motility), blood vessels (relaxation and
contraction); involuntary control
3. Connective tissue includes blood, bone and fat
Loose cells (fibroblast or stroma) embedded in an extracellular matrix
Collagen: most common, long fibres that are strong and resistant to
stretch, provide structural strength to organ e.g. bone, skin
Elastin: long fibres that can be stretched then recoil; abundant in tissues
that can be regularly stretched, e.g. lungs, arteries
Bone: collagen fibres hardened by calcium phosphate, provide strong,
rigid connective tissue to bones
Adipose tissue cells: form loose connective tissue
● white: store lipids/energy; cushions organs and for insulation
● brown: heat
Blood: cells floating in plasma (what remains when red and white blood
cells are removed); 55% of blood liquid volume is plasma; connective
tissue but not a net; is a matrix
Cartilage: chondrocytes secrete ECM rich in collagen and elastin which
makes cartilage firm and flexible
Connective tissue of the small intestine: interstitial fluid: between the
cells: the body’s internal stable environment makes complex
Extracellular matrix (ECM) considered a scaffold or meshwork that
provides structure for the connective tissue cell; called ECM because
the proteins in the matrix are secreted by cells outside of cell;
composition and properties of ECM are different in different connective
tissues (e.g. elastin, collagen)
Extracellular fluid is the fluid found in interstitial fluid, plasma and
lymph
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multicellular animals possible; intracellular fluid exchanges with
interstitial fluid
Amoeba: a unicellular organism; living in pond water; can fulfil its needs
by exchange across its cellular membrane and its external environment
4. Nervous tissue: includes neurons and glial cells
Two basic cell types:
● Neurons: many shapes and sizes; encode information as
electrical signals, communicate with other cells via secretion
of neurotransmitters
● Glial cells (glia): do not conduct electrical signals; provide
support and protection to neurons e.g. create a barrier that
protects brain from chemicals in blood
Homeostasis: the maintenance of stable conditions in the internal environment
● An internal environment makes multicellular animals possible but they require a stable internal environment
● Physiological regulation achieves homeostasis of the internal environment: requires control and regulation in response to changes in both
the external and internal environments
● The regulatory systems controlling the activities of organs and organ systems: nervous and endocrine system
● Normal values of vitamins/minerals etc. = set points or limits; too high or too low: critical values
● Regulation:
○ negative feedback: tells the regulatory system to reduce or reverse a process
○ positive feedback: tells the regulatory system to amplify or increase a response beyond the setpoint
Regulating body temperature: illustrates homeostasis: animals control body temperature by altering rates of heat gain and heat loss; control centre
in the brain (hypothalamus) regulates mammalian body temperature; important due to: heat cramps, heat exhaustion, heat stroke, hyperthermia
(elevated body temperature) usually caused by undertaking exercise during extreme heat of lack of fluid intake
● body temperature needs to stay between 37-37.2 degrees; too high→protein denaturation; animals are temperature sensitive
● endotherms: regulate body temperature by producing heat or active mechanisms of heat loss e.g. mouse; gaining or losing heat
○ metabolism: all energy reactions in the body are inefficient and produce heat as a by-product e.g. transfer of energy; food
molecules to ATP or ATP to work; some energy lost as heat
○ radiation
○ evaporation: releases heat of water from body surfaces or breathing
○ convection
○ conduction
○ blood flow to skin is another way to reduce body heat; heat loss to environment
● ectotherms: body temperature determined mainly by external sources of heat e.g. lizards
● BMR: basal metabolic rate: the amount of daily energy consumed by humans and other animals at rest
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Document Summary
Multicellular animals are composed of four tissue types and most organs contain one or more types of tissues e. g. small intestine. Organs are organized into functional physiological systems. Tissue: cellular level between cells & a complete organ, an ensemble of similar cells & their ecm from the same origin, carry out a specific function. Histology: the study of tissues and organs at the cellular (microscopic) level. Organ: a part of an organism which is typically self-contained & has a specific vital function, composed of multiple tissue types. Types of cells: cells arranged in organs, organs composed of tissues: 4 tissue types fat cell. May be involved in secretion and absorption. May be involved in smell and taste types: squamous (flattened) columar (tightly packed, can have cilia, polarized (either end of that cell is different), can have absorptive/secretory function cuboidal: muscle tissues generate force and movement. Contain long filaments of myosin and actin - allow muscles to contract and exert force.
