SL Biology - Topic 6: Human Physiology

digestion

digestion

the process in which relatively large, insoluble molecules are broken down into smaller, soluble molecules that can be absorbed

alimentary canal

the channel or passage through which food flows through the body, starting at the mouth and ending at the anus

accessory organs

produce substances that are needed for digestion to occur, such as enzymes and bile

peristalsis

a series of muscle contractions in the walls of the esophagus or small intestine that pass like a wave along the alimentary canal to force a bolus of food along

circular muscles and peristalsis

contract to reduce the diameter of the lumen preventing food from moving backwards towards the mouth

longitudinal muscles and peristalsis

contract to reduce the length of the lumen section to force food forwards

enzymes found in the pancreas

amylase, lipase, phospholipase and protease

acinar cells

specialized gland cells in clusters at the end of ducts within the pancreas which produce and secrete enzymes

islets of Langerhans

pancreatic cells which produce the hormones glucagon and insulin

absorption

the movement of digested food molecules, vitamins and mineral ions from the digestive system into the blood and lymph

arteries

thick walled structures which transport blood away from the heart at high pressure

arterioles

branch off from arteries forming narrower blood vessels to transport blood into capillaries

capillaries

one cell thick structures with a small diameter which provide the exchange surface in the tissues of the body through a network of vessels

veins

structures with a wide diameter and valves which transport blood towards the heart at low pressure

venules

connect the capillaries to the veins with few or no elastic fibers and a large lumen

the heart

a hollow. muscular organ located in the chest cavity

septum

a wall of muscular tissue which separates the left and right sides of the heart

atrioventricular valve

valve separating the atria and ventricles

semi-lunar valve

valve separating the ventricles and arteries which leave the heart

pulmonary valve

valve separating the right ventricle and the pulmonary artery

aortic valve

valve separating the left ventricle and the aorta

the vena cava and the pulmonary vein

two blood vessels bringing blood to the heart

the pulmonary artery and the aorta

two blood vessels taking blood away from the heart

systole

the contraction of the heart

diastole

the relaxation of the heart

atrial systole

the period when the atria are contracting, forcing blood from the atria into the ventricles

ventricular systole

the period when the ventricles are contracting, and blood is forced from the ventricles into the pulmonary artery and aorta

sinoatrial node (SAN)

a group of cells in the wall of the right atrium which initiate the heart beat

the cardiac cycle

the series of events that take place in one heartbeat controlled by electrical signals which are initiated in the sinoatrial node

thrombin

an enzyme which catalyzes the conversion of the soluble protein fibrinogen into fibrin

phagocytes

white blood cells which are produced continuously in the bone marrow and are responsible for removing dead cells and invasive microorganisms

antigens

protein molecules on the cell membranes of pathogens

lymphocytes

white blood cells which clone themselves to produce plasma cells which are capable of mass antibody production.

memory cells

cells which remain in the blood for long periods of time to give immunity as they can rapidly produce antibodies after secondary infection as they activate and divide to produce plasma cells

antibiotics

drugs which inhibit the growth of microorganisms as they block specific processes that occur in prokaryotic cells

ventilation

the replacement of older air in the lungs with fresh air from the body’s external environment

Type I pneumocytes

extremely thin alveolar cells which make up the majority of the alveolar epithelium adapted to maximize the rate of gas exchange

Type II pneumocytes

rounded cells which secrete a solution that coats the epithelium of the alveoli which contains pulmonary surfactant which reduces surface tension

trachea

a tube which carries air through the nose and mouth to the lungs, supported by rings of cartilage which allows it to move and flex within the body.

inspiration

the process of breathing in which causes the volume of the chest to increase and the air pressure to decrease

expiration

the process of breathing out caused by the recoil of the lungs after they have been stretched by inspiration as the volume of the chest decreases and pressure increases

neurons

nerve cells which pass along electric impulses to coordinate and regulate body functions

schwann cells

cells which wrap themselves around the axon forming a structure known as a myelin sheath which has a high electrical resistance

saltatory conduction

the process of electrical impulses jumping from one node to the next, greatly speeding up the rate of transmission along myelinated neurons

an impulse

a momentary reversal in the electric potential difference across the neuron cell surface membrane

-70mV

the membrane potential within a resting neuron

polarized neuron

a neuron at it’s resting potential

depolarized neuron

the reversal of the electric potential difference across the neuron membrane

+40mV

the charge at which an action potential has been generated

repolarization

the movement of potassium ions out of the axon causing the inside of the axon to become negatively charged again

hyperpolarization

the short period during which the membrane potential is more negative than the resting potential

refractory period

the period during which the membrane is hyperpolarized

synapses

the structure formed at the end of two neurons along with the synaptic cleft

synaptic cleft

the small gap between where two neurons meet

acetylcholine

a key neurotransmitter used throughout the nervous system produced in the presynaptic neuron

neonicotinoids

synthetic compounds similar to nicotine that are commonly found in pesticides which block synaptic transmission at cholinergic synapses in insects

hormone

a chemical substance produced by an endocrine gland and carried by the blood

pancreas

an organ found in the abdomen of mammals which functions as both an endocrine and exocrine gland

exocrine function of the pancreas

the production of digestive enzymes to be delivered to the small intestine

endocrine function of the pancreas

the productions of the hormones glucagon and insulin

leptin

a hormone secreted by fat storage cells known as adipose cells which targets cells in the hypothalamus that are responsible for controlling appetite

melatonin

the hormone which is secreted by the pineal gland in response to darkness

SRY gene

the gene which determines that the embryonic gonads will develop into testes

the menstrual cycle

the series of changes that take place in the female body leading up to and following the release of an egg from the ovaries

corpus luteum

a follicle after it releases the egg at ovulation and becoming empty

FSH

follicle stimulating hormone produced in the pituitary gland

LH

Luteinizing hormone produced in the pituitary gland

Oestrogen

produced by the egg follicle and the corpus luteum after ovulation

Progesterone

produced by the corpus luteum