Human Systems Flashcards
Exotherms
Gain or lose heat from the external environment
Homeostasis
The maintenance of a constant internal environment in an organism
Endotherms
Generate their own heat from metabolic reactions
Role of excretory system in homeostasis?
- regulates body temp.
- controls osmosis (salt and water conc.)
- controls concentration of body fluids
- removes waste products of metabolism from the body
Give the precise location of the kidneys?
Just below the diaphragm in the small of the back
Sensory neurons
Takes messages from the sense organs
to the cns
Motor neurons
Take messages from the cns to the effectors causing them to respond
Interneurons
Are found in the cns and take messages between sensory and motor neurons
Receptor
Is a cell/tissue that detects a stimulus
Dendrites
Are fibres that carry impulses toward the cell body
Axons
Carry impulses away from the cell body
Schwann cells
Are located along the length of neurons. They make the myelin sheath
The myelin sheath
Is a fat-rich membrane that insulated electrical impulses
The cell body
Has a nucleus and organelles. It forms dendrites, axons and neurotransmitter chemicals
A ganglion
Is a group of cell bodies located outside the cns
Neurotransmitter chemicals
Carry impulses from one nerve cell to another
A neuron
Is a nerve cell
A synapse
Is a region where two neurons come into close contact
A synaptic cleft
Is the tiny gap between two neurons at a synapse
The threshold
The minimum stimulus needed to cause an impulse to be carried
The ‘all or nothing law’
States that if a threshold is reached then an impulse is carried, but if a threshold is not reached no impulse is carried
The refractory period
Is a short timespan after a neuron has carried an impulse during which a stimulus fails to cause a response
The speed at which an electrical impulse is carried depends on….
- the presence or absence of the myelin sheath
- the diameter of the dendrite or axon (larger diameter faster)
A reflex action
An automatic, involuntary response to a stimulus
A reflex arc
Is made up of the neurons forming the pathway taken by nerve impulses. The functional unto of the nervous system
Glands
Are structures that secrete substances
Exocrine glands
Release their products into ducts or tubes e.g salivary glands and gastric glands
An endocrine gland
Is a ductless gland that produces hormones that are released directly into the bloodstream
Why do endocrine glands need a rich blood supply?
Because they secrete hormones into tissue fluid then pass into the bloodstream
A hormone
Is a chemical messenger produced by an endocrine gland and carried by the bloodstream to another part of the body where it has a specific effect
Growth Hormone (GH)
Produced in the pituitary gland. Causes cells to absorb amino acids and form proteins which causes growth. In particular it causes elongation of the bones of the skeleton
The hypothalamus secretes hormones that…
Control the pituitary in response to messages from the brain (i.e links endocrine and nervous system). Also produces anti-diuretic hormone ADH, which controls osmoregulation in the kidneys
The thyroid gland
Produces thyroxine which controls all metabolism
The pancreas exocrine function?
Islets of Lamgerhans produce insulin. Causes cells to absorb glucose from blood for respiration
What is meant by feedback in relation to hormone action?
When the level of a hormone in the blood controls the production of another hormone/ more of itself
Plasma proteins
Antibodies and clotting proteins
Role of plasma
Transport dissolved materials e.g glucose, amino acids, hormones
Role of erythrocytes
Transport oxygen
Role of leukocytes
Defend and fight against infection
Phagocytes
White blood cells that digest bacteria
Role of thrombocytes
Clot blood. Reduces loss of blood and prevents entry of microorganisms
How is a clot produced?
When damaged body cells produce chemicals that stimulate platelets to form a clot
Role of lymphocytes
To make antibodies
Open circulatory system
Heart pumps blood into open-ended vessels. Blood leaves vessels + flows around all cells e.g insects
Closed circulatory system
Blood remains in continuous system of blood vessels. Materials are exchanged between the blood and cells thought the thin walls of the smallest blood vessels
Difference between veins and arteries
Veins have thinner middle layer (involuntary muscle) therefore a larger lumen
Function of collagen in blood vessels…
Prevents walls from over-expansion
Blood pressure
The force blood exerts against the wall of a blood vessel
Valves
Control the direction of blood flow
Give the precise location if the heart
Between the two lungs slightly to the left hand side of the thorax and just above the diaphragm
Pulmonary circuit
Heart ➡️ Lungs ➡️ Heart
Systemic Circuit
Heart ➡️ Body ➡️ Heart
A portal system
Is a blood pathway that begins and ends with capillaries e.g hepatic portal vein connects stomach and intestines to the liver
Pacemaker
A small bundle of specialised tissue that controls heartbeat
Diastole
Her heart chambers relax
Systole
When the heart chambers contract
A pulse
Is the alternate expansion and contraction of the arteries
Human dental formula
2( i 2/2, c1/1, pm 2/2, m 3/3)
The function of the lymphatic system
Forms a link between different parts of blood
