IB Bio - Human Physiology

the digestive tract

the digestive tract

complex tube that food goes through; has three roles: take in food, break down molecules and absorb nutrients, excrete waste

peristalsis

involuntary action by longitudinal and circular muslces to move bolus through GI tract

musoca

innermost layer of the SI lined with epithelium cells

submucosa

connective tissue between the mucosa and serosa that contains large veins and arteries which give rise to the capillary bed of the mucosa

serosa

the outermost layer of the SI consisting of connective tissue that is in contact with body cavities

enzymes produced by the pancreas

amylase, endopeptidase (trypsin), lipases and phospholipases

amylase produced by the pancreas…

breaks down starch into maltose

endopeptidase (trypsin) produced by the pancreas…

breaks down proteins into smaller polypeptides

lipases and phospholipases produced by the pancreas…

break down lipids and phospholipids to glucerol and fatty acids

enzymes produced by the SI

nucleases, maltase, lactase, exopeptidase, dipeptidase

nucleases…

break down DNA and RNA

maltase…

breaks down maltose into glucose

lactase…

breaks down lactose into galactose and glucose

exopeptidase...

removes a single amino acid from the end of the small polypeptides

dipeptidase…

breaks down a dipeptide into two amino acids

villi and microvilli

increase surface area of the SI and absorb monomers produced by the digestive process

monomers absorbed by the villi..

bases and phosphates from nucleic acids, fatty acids and glycerol, amino acids, monomeric carbohydrates (fructose, glucose, galactose)

simple diffusion

absorbs small, hydrophobic molecules and occurs mostly with the products of lipid digestion

facilitated diffusion

absorbs fructose, glucose and other hydrophilic monomers and are moved by protein channels; with concentration gradient

active transport

needed when concentrations are lower in the lumen; goes against concentration gradient; glucose, amino acids, and some mineral ions are transported this way; ATP required

pinocytosis

draws in small droplets of liquids surrounded by a small section of the phospholipid membrane; likely to occur with fat droplets in the SI

systolic

part of the heartbeat when the muscle is contracting

diastolic

part of the heartbeat when the muscle is relaxing; lower pressure than systolic

what assists in maintains blood pressure in arteries?

muscle and elastic fibres

tunica intima

• innermost layer of arteries and veins

• includes endothelium and lines the lumen of all vessels

tunica media

• middle coat that is mainly made of smooth (involuntary) muscle cells and elastic fibres arranged in roughly spiral layers

• thick in arteries

• thin in veins

tunica adventitia

• outermost coat

• tough layer consisting largely of loosely woven collagen fibres

• protect the blood vessel and anchor it to surrounding structures

vasoconstriction

when the arteries experience the highest pressure: systolic blood pressure, and the circular muscles surrounding the arteries resist the outward pressure and constrict

vasodilation

when the heart relaxes between beats, the pressure in the arteries is lowest: diastolic blood pressure, and the smooth muscles surrounding the arteries can also relax

arterioles

smaller arteries that branch off in the body to supply blood to organs, limbs, etc

stroke volume

the volume of blood pumped out of the left ventricle of the heart during each contraction (or heartbeat)

cardiac output

the volume of blood the heart pumps through the circulatory system in a minute

veins

blood vessels that transport blood back from the tissues of the body and return it to the atria of the heart

vein walls

the blood pressure is much lower than in arteries and they do not need thick walls with lots of muscle fibres

vein valves

periodic valves that close to prevent backflow

skeletal muscles

muscles squeeze that squeeze the veins like a pump by exerting pressure

composition of blood

• plasma (liquid portion)

• red blood cells

• white blood cells

• platelets (cell fragments)

plasma

carries dissolved substances such as proteins, hormones, carbon dioxide, glucose, and vitamins and minerals

RBC

contain hemoglobin proteins to transport oxygen

WBC

part of the immune system and help to defend the body from disease

platelets

help blood clot

capillary network

connection between arteries and veins

venules

small veins

William Harvey

discovered that blood circulates around the body with the heart acting like a pump; he also found out about valves in veins and that the blood leaves the body via arteries and returns via veins

double circulatory system

that is the blood flows through the heart twice before it is distributed to tissues

pulmonary circulation

the circulation of blood from the heart to the lungs and back

systemic circulation

the circulation of blood from the heart to the body tissues and back

sinoatrial node

a group of specialised muscle cells in the wall of the right atrium that fires at regular intervals to cause the heart to beat with a rhythm

atrioventricular node

recieves signals from the SA node relayed via the bundle of His located in the interventricular septum to the top of each ventricle

purkinje fibres

fibres that spread signals to the ventricles

cardiac accelerator nerve

the nerve that stimulates the heart to beat faster

vagus nerve

the nerve that reduces the heart rate

epinephrine

increases the heart rate by stimulating the SA node to emit electrical signals at a faster rate as well as by increasing the conduction speed of impulses generated by both the SA and AV nodes

atheromas

fatty deposits caused by high blood concentrations of low density lipoprotein (LDL) in the arterial walls next to the endothelial cells

thrombosis

the forming of a clot in the blood vessel that can block the blood vessel entirely

primary defense

non-specific defence that prevents the entry of organisms and viruses that cause disease

skin pores

for sweating, hair follicles and sebaceous glands that produce oils (called sebum) to keep the skin supple and at a slightly lower pH

mucous membrane

membranes that produce a sticky mucus that contains glycoproteins and lysozymes, enzymes that attack bacterial cell walls

blood clotting

1. exposure to collagen (fibrous protein)

2. collagen exposure attracted platelets to the site

3. platelets get activated and change shape

4. platelets cross link – activation of ADP: binds to receptors, induces aggregation, and recruits further platelets to the site

5. snowball effect (positive feedback): accumulation of platelets; chemicals release -> platelet activation = amplification 

6. thrombin turns fribinogen to firbrin fibres 

7. fibrin form a mesh that catches platelets and RBC to form a clot

leukocytes

white blood cells

macrophages

phagocytes; non-specific; moving by a process called amoeboid motion, these cells engulf a pathogen that has entered the body and is found in the lymph nodes or the blood, and once inside the phagocyte, enzymes secreted by the lysosome will digest the pathogen

pathogen

a disease-causing virus or microorganism

antigen

any molecule that enters the body and triggers an immune response

lymphocyte

the type of white blood cell responsible for specific immune responses

B lymphocyte

recognize antigens through antibody receptors on its surface, they then divide and some become plasma cells and some become memory cells

plasma cells

can bind to the antigen, which allows phagocytes to recognise and then destroy the pathogen, and can bind to proteins in the coat of a virus, which will prevent the virus from entering other (human) cells

memory cells

long-lived pool of cells capable of responding quickly to the same antigen in case you encounter it again

T helper cells

activate B cells

HIV

a retrovirus that infects and stops T helper cells; it has RNA as its genetic material

antibiotics

any substance produced by a microorganism (usually fungi) that block processes that occur in prokaryotic cells but not in eukaryotic cells

antibiotic resistance

if a mutation causing resistance to an antibiotic occurs in a bacterium, after several generations a strain of bacteria will evolve with genes that confer resistance to that antibiotic

ventilation

actively moving air into and out of lungs in order to bring fresh air into the alveoli and get rid of stale air

properties that aid in diffusion

• thin membrane

• large surface area

• concentration gradient

• permeability

• moisture

oxygen concentrations

high in alveoli, lower in blood

carbon dioxide concentrations

high in blood, lower in alveoli

type i pneumocytes

extremely thin alveolar cells that are adapted to carry out gas exchange; flat and thin to increase surface area

type ii pneumocytes

secrete a solution containing surfactant, a water-based solution containing phospho-lipoproteins

inspiration

• external intercostals contract

• internal intercostals relax

• diaphragm contracts

• high volume, low pressure

expiration

• external intercostals relax

• internal intercostals contract

• diaphragm relaxes

• low volume, high pressure

external intercostals

can only lift ribs and move them out

internal intercostals

can only move ribs down and in