Nats 1610 Midterm Review

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4 traits of muscular tissue

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Excitable – respond to stimuli Contractile – have the ability to shorten Extensible – have the ability to stretch Elastic – can return to their original length after being shortened or lengthened

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Muscular tissue is composed of...

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cells called MUSCLE FIBRES which contain the protein filaments actin and myosin. Fibres are arranged in parallel arrays. Contract in coordinated way.

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FUNCTIONS of Muscular Tissue

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Muscles convert chemical energy into mechanical energy

- Producing body movements: walking, heart beating, dancing,

- Stabilizing body position

- Regulating organ volume: sphincters - urinary, etc

- Moving substances within the body: pumping blood, moving food

-Producing heat: generated during muscle contractions

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Three types of muscular tissue + location

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Skeletal: Occurs in muscles attached to bones

Cardiac: Occurs in the wall of the heart Smooth: Occurs in walls of arteries, sphincter, stomach, intestines, urinary bladder

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Connective tissue wrappings of skeletal muscle

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Epimysium – covers the ENTIRE skeletal muscle

TENDON – cord-like “attachment” structure

Fascia – lies on the outside of the epimysium

Perimysium – around each FASCICLE (bundle) of muscle fibres (cells)

Endomysium – between muscle fibres (aerolar CT)

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SKELETAL MUSCLE

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ONE MUSCLE CELL contains many tiny myofibrils are composed of myofilaments (actin, myosin)

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Characteristics of skeletal muscles

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Usually Attached to bones

Muscle cells are called MUSCLE FIBRES - long, cylindrical cells bundled together

Striated (striped) – alternating light and dark bands

Under “voluntary” neural control

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Cause of skeletal muscle striations

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Striations due to orderly arrangement of MYOFIBRILS within muscle cell EACH MYOFIBRIL contains long protein MYOFILAMENTS (actin and myosin) Actin & myosin SLIDE past each other during contraction/relaxation cycles

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Cardiac muscle location and function

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Located in walls of heart, contract to create heartbeat.

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Cardiac muscle structure

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- branched myocytes and cardiocyte cells

- connected end to end by intercalated discs

- FUSED cell membranes that contain gap and other cell junctions - Allow electrical current flow (ions)

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CHARACTERISTICS of Cardiac Muscle

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-Striated with numerous mitochondria

- Usually only one centrally located nucleus per cell surrounded by light staining glycogen

-Some cells act as “pacemakers” – setting contraction rhythm

- Under involuntary neural control

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Smooth muscle location

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Found in walls of viscera (intestine, stomach, etc) and blood vessels

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Smooth muscle tissue structure

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- SPINDLE-SHAPED cells that Lack striations - Staggered arrangement – forming layers in which the thick middle portion of one cell is opposite the thin end of an adjacent cell - Contracts more SLOWLY than skeletal muscle - Can remain contracted for a LONGER time

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Smooth muscle tissue characteristics

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Located in walls of “hollow organs” - Non-striated - Single nucleus per cell - Cells tapered at both ends - Held together by tight junctions - Involuntary neural control

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THREE TYPES OF FILAMENTS in Smooth Muscle Cells

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1.Thick myosin filaments – longer than those in skeletal muscle

2. Thin actin filaments – contain tropomyosin but lack troponin (discussed later)

3. Intermediate filaments – do not directly participate in contraction and Form part of the cytoskeletal framework that SUPPORTS cell shape

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Nervous tissue structure

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Composed of nerve cells called NEURONS: Excitable cells that form communication lines in nervous system

Also consists of NEUROGLIA: A variety of different types of cells that protect & support neurons structurally & metabolically

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Nervous tissue location

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Central Nervous System (CNS) Brain & spinal cord Peripheral Nervous System (PNS)

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Function of nervous tissue

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Sensory input: Sensory neurons conduct impulses from sensory receptors to spinal cord & brain Integration of data: Brain “interprets” nerve impulses Motor output: Motor neurons conduct impulses away from brain & spinal cord to muscles & glands

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3 parts of neuron

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Dendrite: Cell extension that conducts signals TOWARD cell body

Cell body (neurosoma): Contains most of the cytoplasm & nucleus Axon (nerve fibre): Cell extension that conducts nerve impulses (usually AWAY from cell body)

Long axons are covered by myelin sheath: Fatty substance

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Go back through L12 for other diagrams

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D

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What are NEUROGLIA

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various types of cells associated with neurons

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Types of NEUROGLIA

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Oligodendrocytes: Form myelin sheaths around nerve fibers in brain & spinal cord

Astrocytes: Provide nutrients to neurons from blood

Microglia: Become mobile during inflammation Phagocytize debris

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Over 90% of human body is composed of FOUR ELEMENTS

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Carbon ~ 18% Nitrogen ~ 3%

Oxygen ~ 65% Hydrogen ~ 10%

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Atoms

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ATOMS are the smallest units that have the properties of a given element

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Parts of an atom

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CENTRAL NUCLEUS, containing positively-charged protons (1) neutral neutrons (2)

ELECTRON CLOUD (electron shell), containing Negatively-charged electrons (3) Move rapidly around the nucleus

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Atom diagram

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ATOMIC NUMBER of an atom

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Number of protons in nucleus

All atoms of an element have the SAME atomic number Usually written as a subscript to lower left of atomic symbol

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What is the atomic weight & atomic # of carbon?

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Atomic #6

Atomic weight 12

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What is an ELECTRICALLY NEUTRAL Atom?

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Have the SAME number of protons and electrons

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ATOMIC WEIGHT of an atom

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Weight of protons plus neutrons n Protons & neutrons each = 1 atomic mass unit (amu) Electrons are light & have almost no mass Number of protons plus neutrons n Usually written as a superscript to upper left of atomic symbol

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Electron shells

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Electrons orbit around the atom nucleus inside various “SHELLS” around the nucleus

“Outermost” shell is the VALENCE shell

Atoms tend to LOSE, GAIN OR SHARE ELECTRONS until they are surrounded by 8 valence electrons

first shell, closest to nucleus, lowest energy: holds up to 2 electrons

second shell – holds up to 8 electrons

third shell – tends to hold up to 8 electrons

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Which 3 types of subatomic particles are atoms composed of (as studied in this course)?

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Protons

Neutrons

Electrons

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What is the atomic number of an atom – and how is it usually indicated?

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Number of protons in atom

Bottom left of chemical symbol

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What is the atomic weight of an atom – and how is it usually indicated?

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Number of protons + neutrons

Top left of chemical symbol

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How many electrons are there in an electrically neutral atom?

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Same amount of electrons and protons

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Isotopes

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When an element has same # of protons but different # of neutrons

isotopes have a DIFFERENT ATOMIC WEIGHT

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Radioactive isotopes

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Unstable nucleus spontaneously decays, giving off rays of different energy & subatomic particles Can be used as a tracer - carbon 14 dating, medical imaging… Radiation kills healthy cells & cancerous cells

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Molecules

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Groups of 2 or more atoms held together in a stable association

Some molecules are made up of only ONE ELEMENT - i.e., oxygen has 2 oxygen atoms

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Compounds

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Molecules made up of MORE THAN ONE TYPE OF ELEMENT

Ex) water H-2 O-1

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Chemical bonds

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Hold atoms together in molecules or compounds

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Chemical equation

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Reactants --> Products

Atoms are RE-ARRANGED, but NEVER LOST

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Example of chemical equations

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Phothosynthesis

6CO2 + 6H2O --> C6H12O6 + 6O2 6 carbon dioxide + 6 water --> 1 glucose + 6 oxygen

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What determines reactivity?

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The number & arrangement of their electrons

UNFILLED VALENCE SHELLS make atoms likely to react i.e., hydrogen, carbon, oxygen, and nitrogen all have vacancies in their outer shells All are “reactive”

↳ Atoms w full valence Shell usually do not bond

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Chemical bonds

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The union between the electrons of neighbouring atoms is called a CHEMICAL BOND

Chemical Bonds form in attempts to STABILIZE the outer shells of the interacting atoms to “fill” their outer shells

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THREE important bonds in biological molecules

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1. Ionic bond 2. Covalent bond 3. Hydrogen bond

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IONIC BONDS

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formed by the ATTRACTION of oppositely charged ions

1. One atom loses electrons & becomes a positively charged ion 2. And another atom gains these electrons & becomes a negatively charged ion 3. Charge differences ATTRACT the 2 ions to each other

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Covalent bonds

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form when atoms SHARE a pair of valence electrons

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Physical and chemical properties of water

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1. The capacity to dissolve or repel substances 2. Cohesion and Adhesion 3. Temperature-stabilizing effects 4. Always in flux – transporting materials 5. In A LIQUID STATE over wide range of temperature – from 0°C to 100°C

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Polar covalent bonds

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form when atoms DON’T share electrons EQUALLY – which is what happens in a water molecule

L14- slide 12

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HYDROGEN BONDS

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FORM by the ATTRACTION BETWEEN (1) a hydrogen atom of a positively charged end of one polar molecule AND (2) the negatively charged end of ANOTHER polar molecule

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Why do the electrons in a molecule of water tend to spend more time near the oxygen atom?

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Oxygen has more protons (electromagnetive attracts electrons )

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Describe how a hydrogen bond forms.

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FORM by the ATTRACTION BETWEEN (1) a hydrogen atom of a positively charged end of one polar molecule AND (2) the negatively charged end of ANOTHER polar molecule

Ex) the negative charged O atom of polar molecule links w positive H atom

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What causes liquid water to be “liquid”?

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Hydrogen Bonding in Liquid Water -molecules held loosely – bonds keep changing (in flux) - water “flows” (leaving no spaces)

water FLOWS as a unit Due to water molecules ‘clinging’ to each other…

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Water properties

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→ Water is LIQUID at room and body temperature

→ Water is a SOLVENT for other polar molecules

→Water is COHESIVE and ADHESIVE

→ Water TEMPERATURE rises and falls SLOWLY

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water Cohesion

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COHESION makes water molecules PULL on each other as they CLING to each other

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Water ADHESION

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ADHESION makes water molecules ADHERE to other surfaces

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Cohesion

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Adhesion

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water path through tree

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diagrams

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Surface tension

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→ Cohesion also creates SURFACE TENSION at a water-air interface → Water molecules at the surface Are MORE STRONGLY attracted to each other than to the air above → The water molecules prefer to be attached to other water molecules (due to hydrogen bonding) rather than to evaporate → Thus, water molecules “CLING” TIGHTLY to each other at air interface → Creating surface tension

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Water TEMPERATURE

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→ Changes slowly

→ a great deal of heat is required to raise it’s temperature because H-bonds can “absorb” a lot of energy before they break apart

→Water molecules prefer to bond to other water molecules rather than to evaporate Thus – water HOLDS heat, causing it’s temperature to drop or rise slowly

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Benefits of Water temp

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→ Water PROTECTS organisms from rapid temperature changes

↳High percentage of ‘body water’ in organisms e.g., 150 lb human is 100 lbs water (~67% body weight) Resist changes in body temperature + Keeps relatively stable internal environment

→ Water in blood helps to DISTRIBUTE heat throughout body Heat is picked up from muscles where it’s generated

→Water EVAPORATING from a surface carries away heat, cooling the surface Body heat is evaporated as sweat - cooling body and preventing over-heating

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Frozen water

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→ LESS DENSE than liquid water as particles more slower+ farther apart at low temp

→ floats due to low density Surface layers insulate liquid water below it and' provide walking Surface for land animals

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?

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Water molecules can DISSOCIATE (break down) to form n Hydrogen ions (H+) and hydroxyl ions (OH- ) n These in turn can then re-bind to form water n Question: Why do H+ and OH- have the charges that they do? H – O – H H+ + OH- n The amount of H+ in the body is precisely regulated n by homeostatic mechanisms n Slight changes in H+ can cause severe illness by disrupting chemical reactions in the body (H+ are very reactive – trying to get back an electron) n H+ contribute to acidity – the more H+ the more acid a solution is

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Acids

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Anything that can donate hydrogen ions (H+) [protons] ↳ i.e. because releases high concentrations of H+ ↳ Acids INCREASE H+ concentration in solution

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Bases

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Anything that can accept hydrogen ions (H+) → i.e., because releases high concentrations of OH- → these then can bind to more H+ → Thus, bases DECREASE H+ concentration in solution

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PH scale

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Measures concentration of H+ & indicates how acidic something is n The more H+, the more acidic the solution

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Buffers

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Biological systems function within a very narrow range of pH ↳ Help keep the pH within normal limits by → Taking up excess H+ when concentrations increase →Adding H+ when concentrations decrease → Various buffering systems in body maintain correct body pH levels

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Carbonic acid- bicarbonate buffering system

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keeps human blood at PH of 7.4

→ If H+ levels in blood DECREASE, MORE carbonic acid will dissociate to release MORE H+ into the blood

→If H+ levels in blood INCREASE, they combine with bicarbonate ions to re-form MORE carbonic acid, thus removing MORE H+ from the blood

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Epidermis

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→ outer layer of skin made from epithelial cells: Keratinized stratified Squamous Epithelium

→4-5 Major layers

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Dermis

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→ deeper layer of Skin, below epidermis

→ made from loose regular connective tissue

→ collagen + Elastic fibres, Small blood Vessles + nerves

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Subcutaneous layer

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→ deep to dermis

→ made from adispose+ loose connective tissue

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Go over Epithelial + Connective tissue

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PoWerpoint + prev. flash cards

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5 layers of Epidermal cells (deepest to Superficial)

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→ Stratum Basale (youngest)

→ Stratum Spinosum

→ Stratum Granulesum

→ Stratum Lucidum

→ Stratum Corneum (oldest)

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*

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4 types of cells in Epidermis

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→ Keratinocytes

→ Langerhans Cells+ Granstein Cells

→ Merkel celts

→ melanocytes

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Keratinocytes

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→ most numerous Cell type in Epidermis

→ tightly held together by cell junctions w many desmosomes

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Langerhans Cells

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→ Participate in immune response

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Langerhans cells

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→ Participate in immune response

→ Easily damaged by uV light

↳ Granstein Cells also participate in immune responses- not as susceptible to uv not yet understood

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Merkel cells

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→ least numerous

→ located in deepest layer of epidermis

→ function in sensation of light touch

→ associated with sensory neurons

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Melanocytes

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→ Produce melanin (Skin pigment)

→Extend cell processes (extensions) between keratinocytes to distribute melanin – via MELANOSOMES

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Melanin

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→ Synthesized and stored in malanosomes (organelle in melanocytes)

→ absorb damaging uV light

→ Melanin clusters – form protective “veils” over nucleus – protect DNA

tanning→ increase melanin in keratinocytes at skin surface

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L 16 review

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For proper flash cards

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Difference in skin Colour

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All skin colours have the SAME NUMBERS of melanocytes, but 1. AMOUNT of melanin produced differs 2. PROPORTIONS of each differ (yellow vs black) 3. The extent of DISPERSAL differs

Other factors

↳CAROTENE in dermis + HAEMOGLOBIN in blood of the capillaries in dermis

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Freckles and Age Spots

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Non-cancerous melanin PATCHES

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Tanning

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→ ACCUMULATION of melanin at skin surface → body’s attempt to DEFEND itself against UV damage

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What is a melanosome?

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Cell vesicle inside a melanocyte that contains melanin

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What amino acid is turned into melanin?

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Tyrosine

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vitamin D

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Vit-D is an essential STEROID HORMONE needed for: 1. Normal phosphorus & calcium homeostasis 2. AND, for proper development and maintenance of bone

↳Sunlight helps the formation of Vit-D

↳ Vit-D is used to create the HORMONE that AIDS in CALCIUM ABSORPTION

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Tanning

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INCREASED skin exposure to sunlight – melanin production increases – more melanosomes delivered to keratinocytes

GENETICS DETERMINE base skin colour AND how much it can tan

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Prolonged Exposure to Sun

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ACCELERATES skin aging n Affects fibres in connective tissue – how?

Skin becomes leathery, sags, & wrinkles

UV also DAMAGES Langerhans cells

skin more prone to infection – why?