Physiology is the investigation of the processes or functions of living things.
Why Study Physiology?
It provides an in-depth understanding of the human body and how it functions.
Organizational Levels of the Human Body
Chemical Level
Involves combinations of molecules.
Cell Level
Cells are the structural and functional units of the body.
They contain organelles, which are "little organs" performing specific functions.
Tissue Level
Tissues are comprised of similar types of cells.
There are four main types: epithelial, connective, muscle, and nervous.
Organ Level
Organs are composed of two or more types of tissues.
Organ System Level
Multiple organs work together to perform a common function.
There are 11 human body organ systems.
Organism Level
The organism is a whole, living being.
Characteristics of Life
Organisation: The interrelation of organizational levels to function.
Metabolism: Chemical reactions that maintain life. Involves the use of energy to perform functions.
Responsiveness: The ability to read internal or external changes and respond or adjust to stimuli. Control systems include the nervous and endocrine systems.
Reproduction: Creation of new cells.
Development: Changes over time, from fertilization to death. Includes differentiation, where immature cells change to mature, specialized cells.
Growth: Increase in cell size and/or number.
Cell Biology
Key components include the plasma membrane and the nucleus.
Cell Functions
Cell Metabolism and Energy Use
Chemical reactions within cells often involve energy transfer.
Synthesis of Molecules
Communication
Chemical and electrical communication between cells.
Reproduction and Inheritance
Cells contain DNA molecules, which carry an organism's genetic information.
Plasma Membrane
Functions:
Barrier separating intracellular fluid (ICF) from extracellular fluid (ECF).
Encloses cell contents.
Attaches cells to the extracellular area.
Enables communication.
Facilitates movement into and out of the cell.
Plasma Membrane Components
Membrane Lipids
Phospholipids form a lipid bilayer.
Cholesterol is also present.
Membrane Proteins
Integral membrane proteins
Peripheral membrane proteins
Plasma Membrane Movement
The plasma membrane is selectively permeable.
Nutrients need to move into the cell, and waste needs to move out.
Two types of movement:
Passive transport
Active transport
Passive Transport
Diffusion: Movement of solutes from high to low concentration (down a concentration gradient).
Osmosis: Diffusion of water to assist in equilibration; water moves from a less concentrated solution to a more concentrated solution.
Facilitated Diffusion
Active Transport
Uses energy to move molecules against a concentration gradient (from low to high).
Example: Sodium-potassium pump, which exchanges one molecule for another (sodium out and potassium in).
Secondary Active Transport
Vesicular Transport
Transport via formation or release of vesicles.
Endocytosis
Phagocytosis (“cell-eating”)
Pinocytosis (“cell-drinking”)
Receptor-mediated endocytosis
Exocytosis
Cytoplasm
Cytoplasm = Cytosol and Organelles
Cytosol = solution comprised of suspended and dissolved molecules
Cytoskeleton = holds organelles and nucleus in place and supports the cell
Nucleus
Components:
Nucleoplasm
Nuclear envelope
Nuclear pores
Chromosomes
Deoxyribonucleic acid (DNA) – structural and functional characteristics
Ribonucleic Acid (RNA)
Nucleolus
Ribosomes – site of protein synthesis.
Produce proteins used inside the cell and proteins secreted from the cell.
Endoplasmic Reticulum
Continuation of the nuclear envelope.
Rough Endoplasmic Reticulum: Has ribosomes attached.
Smooth Endoplasmic Reticulum: Absence of ribosomes.
Starts at the pyloric sphincter and ends at the jejunum
Entry point of ducts from the Liver and Pancreas
The surface area and thus absorption capability is greatly increased by the presence of circular folds, villi and microvilli
Jejunum (2.5 m)
Similar in structure to the duodenum
Becoming smaller
Major site of absorption
Ileum (3.5 m)
Smaller in;
Diameter
Wall thickness
Number of folds and microvilli
Less absorption
Ileocacal sphincter and valve
one way valve flow to the large intestine
Small Intestine Secretions
Mucus, electrolytes and water
Lubricates and protects the wall from acidic chyme
Keeps the chyme in liquid form to assist with continued digestion
Hormones
Cholecystokinin and Secretin
Decreases gastric secretions
Stimulates liver and pancreas secretions
Pancreas and liver secretions enter into the duodenum and assist with digestion
Enzymes
Disaccharidases and Peptidases
Assist with the breakdown of food
Segmental and peristaltic contractions mix and move chyme in the small intestine
Liver
Largest gland in the body
Second largest organ
Situated in the upper right quadrant of the abdomen
Has two lobes a right and left separated by a ligament
The porta on the inferior surface is an opening (gate) which allows the following to enter and ex Liver
Hepatic Artery
Carries oxygenated blood from the heart to the liver
Hepatic portal vein
Carries nutrient rich, deoxygenated blood from the small intestine to the liver
Carries bile from the liver to the Gallbladder and Duodenum
Bile
Bile is produced by the Hepatocytes
From the hepatic cords bile is collected by the bile canaliculus
Flow towards the hepatic triad and exits via the hepatic ducts
Liver Functions
BileProduction:
Bile enters duodenum and neutralizes and dilutes stomach acid as a low pH renders the effectiveness of pancreatic enzymes
Contains bile salts which emulsifies lipids
Lipids are hydrophobic
Therefore, they clump together
Bile helps break that clump apart
Enzymes can then breakdown lipids
Bile Contains NO digestive enzymes
Stimuli
parasympathetic stimulations, secretin secretion, bile salts (positive feedback)
Secretion continues until the duodenum e
Storage
Sugar (as glycogen), lipids, vitamins
Storage fluctuates depending on the bodies needs
Inter-conversion of Nutrients
The correct nutrients are not always present in the required amounts thus the liver can convert nutrients to others if need be
Detoxification
By-products produced during metabolism and ingested toxins are further broken down thus altered to less harmful toxins in the liv
Alcohol – Liver is the primary organ which breaks down alcohol
Synthesis of Molecules
Plasma proteins and clotting factors
Gallbladder
On the inferior surface of the liver
Three layers;
Inner mucosa folded into rugae which expand
Muscularis layer of smooth muscle which contracts and assists with expelling bile
Outer serousa
Acts as a storage site for Bile secreted from the liver
Water and electrolytes are absorbed = concentrated substance
Stimuli
secreted in response to cholecystokinin
Pancreas
Exocrine role
secretes substances that exit onto a surface or through a duct
Pancreatic Juice
Aqueous component
Most important part of the aqueous component is the bicarbonate ions
Neutralizes stomach Chyme
Stops pepsinogen working
Creates a suitable environment for pancreatic juice to function
Enzyme component
Proteolytic pancreatic enzymes – digest proteins
Secreted in their inactive form to prevent digestion of the pancreas where they are produced
Trypsin
activates the secretion of other proteolytic enzymes
Chymotrypsin
Carboxypeptidase
Pancreatic amylase
Continues the work of salivary amylase - the break down of carbohydrates
Pancreatic lipase
Breaks down lipids
Regulation of Pancreatic Secretions
Chyme entering the duodenum causes release of:
Secretin
which stimulates secretion of the aqueous component
Cholecystokinin
stimulates the enzyme component of pa
Parasympathetic stimulation causes the release of pancreatic juice particularly during the ceph
Hepatic ducts (left and right) exit liver e common hepatic duct and cystic duct (which exits the common bile ducte hepatopancreatic ampulla (common bile duct + pancreatic duct meet)e con duodenum (small intestine) through the major duodenal papilla
Summary of Digestive Hormones
Gastrin
Stimulated by distension of stomach and the bolus entering the stomach
Increases gastric secretions
Secretin
Stimulated by chyme entering the duodenum
Decreases gastric secretions
Stimulates pancreas to secrete pancreatic juice
Stimulates bile secretion from liver
Cholecystokinin
S ente
D secre
S secre
S from
Digestive Enzymes
Amylase
Break down Carbohydrates
Lipase
Break down Lipids
Protease
Break down Proteins
What affects enzyme function?
Temperature
pH
Typically enzyme names end in (suffix is) “ase”
Cardiovascular System Functions
Blood
From the heart to the tissues and back to the heart again
Exchange nutrients, waste products and gases with tissues
Nutrients and Oxygen move from the vessels to the tissues
Waste products and Carbon dioxide move from the tissue to the vessel
Transport substances
Hormones, enzymes, nutrients, gasses, waste products are all transported in blood
Assists with regulation of blood pressure
Heart and blood vessels work together
Directs blood flow to tissue
In order to maintain homeostasis the circulatory system can direct to tissues in need
The Circulations
Systemic Circulation:
Heart (Left ventricle) a body tissues
Pulmonary Circulation:
Heart (Right Ventricle) a lungs (alveolus)
Coronary Circulation:
Myocardium
Cardiovascular Components
Heart
Blood Vessels
Arteries
Capillaries
Veins
Blood
Functions as a dynamic tissue:
Transport: of substances from one area of the body to another
Immunity: body’s defence against disease
Haemostasis: processes to stop bleeding
Homeostasis: process of maintaining a stable internal environment
Transport of regulatory molecules
Regulation of pH
Maintenance of body temperature
Immunity
Total blood volume 4-6 L (depending on body size)
Components of Blood
Plasma
Composed of water with some dissolved solutes including proteins, lipids (fats), carbohydrates, amino acids, vitamins, minerals hormones, wastes, gases and electrolytes