Human Physiology 100 TEST 1

Regulation of blood pressure- - Baroreceptor reflex

•Baroreceptors located in carotid sinus and aorta monitor the degree of stretch in blood vessels as blood flows through them.

•When blood pressure (BP) falls the baroreceptors are stretched less

•Impulse sent to the cardiovascular centre to increase cardiac output (CO) (via HR & SV) & vasoconstriction via sympathetic stimulus

Resulting in increased Blood Pressure

Positive Feedback Loop

The response of the effector increases change of the stimulus

Body is moved away from homeostasis

Normal range is lost

For speeding up processes

plasma membrane

Phospholipid bilayer: Intracellular, inside the cell

Extracellular: outside the cell

Regulates exchange with environment

Ions and nutrients into the cell

Release of wastes and cellular products outside the cell

Cellular communication

Structural Support

Anchors cells and tissues

Organelles

Specialised structures which perform specific functions for normal cell homeostasis

G protein coupled receptors (GPCRs)

Receptors that cross the membrane and specifically GPCRs have seven transmembrane domains.

Activation of the receptor, causes activation of a nearby G-protein, which subsequently regulates further signalling events and changes in cell function

Transmembrane receptors with linked enzymatic domains: example

Insulin receptor

Intracellular receptors

Found within cells. In either cytoplasm or the nucleus

when a molecule (ligand) binds to a receptor, the molecule-receptor complex binds the the DNA and alters the proteins (gene transcriptions). The effects of intracellular receptors tend to be slow.

Non-membranous: do not have a definite boundary or are an extension of the plasma membrane

cytoskeleton

microvilli

cilia

ribosomes

Cytoskleton

Provides structural framework for a cell

Movement of cellular structures and materials

Made of 3 types of filaments

•Microtubules (tubulin)

•Intermediate filaments (keratin)

•Microfilaments (actin)

Microvilli

•membrane extensions containing microfilaments

•increases surface area for absorption of extracellular materials

Endoplasmic Reticulum (ER)

network of membranous sheets and channels that extend throughout the cytoplasm.

Golgi Apparatus

characterised by stacks of flattened membranes containing chambers.

Skeletal Muscle Fibre

moves bone

Needs a large amount of energy and therefore has many mitochondria

Chain of amino acids

= polypeptide chain = functional protein

Organelles involved in protein synthesis

Nucleus, ribosomes, rough endoplasmic reticulum, Golgi apparatus, transport vesicles

Paring is due to

the shape of bases

Transcription

DNA is transcribed into messenger RNA (mRNA) in the nucleus.

mRNA is transported from the nucleus to ribosomes in the cytoplasm or associated with the RER

Translation

mRNA is translated into protein in the cytoplasm and at ribosomes.

Proteins destined for modification and transport enter the RER and become folded before being transported to the Golgi Apparatus for modification and packaging into secretory vesicles.

Cancer types: BENIGN

cells are contained (encapsulated)

generally not life threatening

Active transport

Requires the cell to use ATP

Isotonic

Solution is ISOTONIC if there is no flow of water between the cell and solution (same osmostic pressure.

Electrochemical gradient

Sum of chemical and electrical forces acting across the cell membrane

Unequal distribution of positive and negative charges across the plasma membrane

Neuron -70 mV

Cardiac Muscle Cell -90 mV

Contributing factors

•Differences in ion concentrations

•Differences in the permeability of the plasma membrane.

Types of tissues (four)

Epithelia tissue

connective tissue

muscle tissue

neural tissue

Functions and characteristics of epithelial tissue

cell polarity

intercellular connections

Functional regions of epithelia

Epithelial cells have several different specialized structures

microvilli which increase the surface area to transport substances

cilia in lungs which moves mucous toward the throat

no blood supply - avascular

Cell adhesion molecules (CAMS)

connects large areas of plasma membranes of adjacent cells

Connect basal surface of epithelium with the basement membrane

Desmosome

Desmosome

-connections that can resist twisting and stretching

-linking of two cells by CAM & proteoglycans to the cytoskeleton

-Strong connections and found in the superficial layers of our skin.

number of cells between the exposed surface and the basement membrane

simple

stratified

An organism is said to be at homeostasis when its internal environment:

• contains the optimum amount of chemicals

• has optimal temperature

• has optimal pressure for the survival of living cells

Cyclic components required for homeostasis

Receptor: sensor that monitors the physiological environment and signals a change.

Control Centre: processes the signal & sends instructions for a response to occur. Determines the level of change required.

Effector: carries out instructions sent by the control centre.

Negative Feedback Loop

The response of the effector reduces or stops the stimulus

Body is brought back into homeostasis

Normal range is achieved

Thermoregulation - Primary Organ Systems Involved

•Integumentary system

•Muscular System

•Cardiovascular system

•Nervous System

Regulation of blood sugar

When Blood sugar too high: increased insulin released from pancreas (liver removes blood glucose excess glucose stored as glycogen)

when too low: glucagon released from the pancreas (liver breaks down glycogen glucose into blood)

Ion channels:

Regulate the movement of ions across membranes e.g. nicotinic receptor activation.

Rough Endoplasmic Reticulum (RER

•Lipid and protein synthesis

•Folds polypeptides into proteins

•Packages newly synthesised

Mitochondria

double membrane bound organelles.

The inner membrane folds to form cristae which enclose important metabolic enzymes.

Macrophage

cells that fight disease

engulf bacteria which are then degraded and thus inactivated

many lysosomes within the cell to digest bacteria it engulfs

Adenine -

thymine

Guanine -

Cytosine

Gene

A section of DNA which has the instructions for one protein e.g. the sequence of amino acids

3 types of RNA involved in protein synthesis

Messenger RNA: mRNA

Transfer RNA: tRNA

Ribosomal RNA: rRNA

Two general types of cells

Somatic cells: non sex cells, divide via MITOSIS

Sex cells: sperm or oocyte MEIOSIS

APOPTOSIS

programmed cell death

activation of "suicide genes"

DNA fragmentation

Ingestion of dying cell by phagocytes

Cancer or tumour

abnormal cell division and growth e.g. uncontrolled cell division

Why is the plasma membrane is described as semi-permeable.

Cells differ in their permeability depending on what proteins are associated with the membrane.

Facilitated diffusion - protein channels

Passive transport through a protein channel

•ions such as sodium and potassium

•leak channels

Net movement of molecules toward a lower concentration

Osmolarity/Osmotic concentration

The total solute concentration of all solutes in an aqueous solution.

Osmoles per litre (Osmol/L)

Osmole is the number of moles of ions that contribute to a solution's osmotic pressure

Normal plasma (intracellular environment) approximates 285 mosmol/L

hypotonic

Solution is HYPOTONIC if water moves into the cell via osmosis.

epithelia

layers of cells covering external or internal surfaces

glands

Structures that produce secretions

functions of epithelial tissue

protection, absorption, filtration, secretion

-provide physical protection

-control's permeability - any substance that leaves or enters your body must cross an epithelium

-Provide sensation (large supply of sensory receptors and nerves)

-Produce specialised secretions (glandular epithelium/glands)

How does the body maintain/regulate homeostasis?

Intrinsic/autoregulation - Automatic response within a cell, tissue, or organ to some environmental change

Extrinsic regulation - Responses controlled by the nervous and endocrine systems

Cytosol

Fluid component of the cytoplasm-intracellular fluid

Contains ions, proteins and lipids

Chemical reactions take place

Receptors

proteins which interact with molecules (ligands) to cause a biological response within the cell

receptors are often the targets of drugs

there are four different types of receptor in the body

(ion channels, G protein coupled receptors, receptors w linked enzymatic domains, intracellular receptors)

Transmembrane receptors with linked enzymatic domains

Molecules (ligand) bind to the receptor which leads to the activation of the intracellular enzymatic domain

The effects related to the activation of this receptor tend to be slow (take hours) to occur

Transmembrane receptors with linked enzymatic domains

Receptor tyrosine kinases (RTKs) have an extracellular molecule (ligand) binding domain and an intracellular domain with tyrosine kinase activity.

When the signalling molecule binds to one receptor it causes its association with a second receptor (dimerization)

Membraneous: enclosed by a membrane to afford a specific function

nucleus

endoplasmic reticulum

golgi apparatus

lysosome

mitochondrion

Cilia

•Long extensions of the plasma membrane containing microtubules

•Motile cilia move materials over cell surfaces and a primary cilium can act as a sensor.

Nucleus

membrane bound, fluid structure that contains enzymes, proteins and genetic material (DNA/chromatin) which together control cellular function

Smooth Endoplasmic Reticulum

•makes lipids and steroid hormones

•detoxifies drugs and alcohol

Lysosomes

contain enzymes that digest material and are considered the major degradative compartment of the cell.

Proteosomes

contain protein degrading enzymes called proteases which breakdown and recycle damaged or normal intracellular proteins.

Proteins are tagged with a molecule called ubiquitin which signals for protein removal from the cell.

Fibroblast

connective tissue cells involved in connecting body parts

produce the protein collagen which is integral to the physiology of skin

Abundant rough ER and Golgi apparatus to make and secrete proteins for collagen fiber formation

Neurons

cells involved in the processing and communication of information in the nervous system

produce a significant amount of protein so have many nucleoli

long microtubules to allow the movement of material from the axon terminal to the cell body.

protein sysnthesis

GENE ACTIVATION, TRANSCRIPTION, TRANSLATION, PROCESSING, FOLDING

uracil

Swaps w thymine in RNA

Gene activation

Every gene has a "start" and "stop" signal to control protein synthesis

The gene is kept inactive by being tightly coiled and bound to histones i.e. the start signal is 'hidden'.

Gene activation requires the DNA to be uncoiled to expose the sites required to start the process of making protein i.e. transcription.

The cell life cycle

I: Interphase

G1: Normal cell functions plus growth, duplication of organelles and protein synthesis

S: DNA replication

G2: Protein synthesis

M Phase: Mitosis and Cytokinesis

Mitosis (somatic division)

3 STAGES

DNA REPLICATION

MITOSIS

CYTOKINESIS

parent cell divides into two identical daughter cells each with 46 chromosomes (23 pairs)

Mitosis

Divides duplicated DNA into two sets of chromosomes

DNA coils tightly into chromatids

Chromatids connect at a centromere

Protein complex around centromere is kinetochore

Mitosis & Cytokinesis

1.Prophase: chromosomes are visible, centrioles move to opposite side of cell, nuclear envelope disapperas, spindle fibres extend and attach to chromosomes

2.Metaphase: chromosomes align themselves along the metaphase plate; equidistant from poles

3.Anaphase: centromere splits; two sister chromatids move to the opposite sides of cell

4.Telophase: nuclear envelope forms, chromosomes change to chromatin, final location of nucleus at opposite ends of cell

5.Cytokinesis: splitting of the cytoplasm with the formation of two identical cells.

cell death

APOPTOSIS and NECROSIS

NECROSIS

Cell is injured

Cellular contents flows into interstitial fluid

Inflammatory response is initiated

Cell Differentiation

All cells carry complete DNA instructions for all body functions

Cells specialize or differentiate to form tissues (e.g. liver cells, fat cells, and neurons)

By turning off all genes not needed by that cell

Differentiation depends on which genes are active and which are inactive

Cancer types: MALIGNANT

cells are no longer contained

cells can also travel to other organs and tissues

Passive

Does not require the input of physiological energy (ATP)

3 main transport processes:

Diffusion: passive

Carrier: passive or active

Vesicular: active

Diffusion

DIFFUSION IS A FUNCTION OF THE CONCENTRATION GRADIENT AS SOLUTES MOVE FROM A HIGH CONCENTRATION TO A LOW CONCENTRATION.

Passive process that results from the random motion and collisions of ions and molecules.

Over time the molecules will eventually become evenly distributed.

Important in body fluids as it eliminates a local concentration gradient.

Factors that affect the rate of diffusion

Distance - the shorter the distance the faster the rate of diffusion

Molecule size - the smaller the molecule the faster the rate of diffusion

Temperature - the higher the temperature the faster the rate of diffsuion

Concentration gradient - the steeper the gradient the faster diffusion

Electrical force

Simple diffusion

Lipid soluble molecules moving from a region of high concentration to low concentration

•Alcohols

•Fatty acids,

•Steroids

•Gases e.g. O2

Facilitated diffusion - carrier proteins

Ions or organic substrates bind to an integral membrane protein which changes shape to allow the molecule to cross the membrane.

Net movement of molecules toward a lower concentration

Osmosis

Net Movement of Water Molecules Across a Semi permeable Membrane to a Higher Solute Concentration

Water moves through channels called aquaporins

Hypertonic

Solution is HYPERTONIC if the water moves out of the cell via osmosis.

Membrane/Transmembrane Potential

In normal conditions:

The inside of the plasma membrane is slightly negative with respect to the outside of the cell

slight excess of positive (+ve) charges outside the cell

slight excess of negative (-ve) charges and proteins inside the cell.

The separation of charge across the membrane creates a potential difference which is called the membrane/transmembrane potential

Resting membrane potential is the potential of an undisturbed cell.

Secondary Active transport

Important for the absorption of glucose and amino acids in digestion

Moves a specific substrate down its gradient: 2 sodium ions bind, then glucose is transported into the cell followed by active transport of sodium ions out of the cell

Vesicular Transport

Vesicular transport is vital for all mammalian cells

Endocytosis

Movement of material INTO the cell

•receptor mediated endocytosis

•pinocytosis

•phagocytosis

Exocytosis

Movement of material OUT OF the cell

mportant in the nervous system for communication between brain cells: release of neurotransmitter.

Classification of epithelial tissue

simple epithelial tissue

stratified epithelial tissue

Types of glands

endocrine glands

exocrine glands

Characteristics of epithelia

Made of cells which are held tightly together to form an effective barrier

Two functional regions:

the apical (top) surface which is exposed to the internal or external environment

basal (bottom) surface which is attached to a basement membrane

basement membrane is a specialized form of extracellular matrix

Maintaining the Integrity of Epithelia

1. Intercellular connections

2. Attachment to the basement membrane

3. Epithelial maintenance and repair

Cell Junctions

specialized areas of plasma membrane that attach cells together or

-Gap junctions

-Tight junctions

- Desmosomes

Tight junction

-prevents movement of water and solutes between cells between cells

-when an epithelium lines a tube (digestive tract) the apical surface is exposed to inside the tube.

-protects basal surface from contents of lumen (enzymes, acids, wastes)

Attachment to the basement membrane

hemidesmosomes attach a cell to the extracellular filaments in the basement membrane

basement membrane also acts as a filter for substances diffusing between the adjacent tissues and the epithelium

Maintenance and repair

epithelial cells have a short life due to exposure to digestive enzymes, acids, pathogenic bacteria and abrasion

Maintains structure over time due to the division of stem cells which are located near the basement membrane which offers protection.

Classification of epithelia: SHAPE TYPES (3)

squamos

cuboidal

columnar

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