Biology revision Heart and immune system
Cardiac cycle
Diastole is when the Atria and the ventricles are relaxed
Blood is flowing from the Vena Cava and the Pulmonary vein into
the atria
Blood is also trickling into the ventricles
The pressure is higher in the atria therefore the bi and
tricuspid valves are open
Atrial systole is when the atria contracts
The pressure is higher and again the tri and bicuspid valves are
open
Blood flows into the ventricles
The atria relax atrial diastole
Ventricular systole is when the ventricles contract
Pressure in the ventricles rises
The tri and bicuspid valves close
Pressure in the ventricle is now higher than in the arteries
The semi lunar valves open and blood flows into the arteries
The ventricles will now relax ventricular diastole
The semi lunar valves close and the heart returns to a state of
diastole
Body right hand side
Left Lungs
The heart is myogenic = it does not need nerve muscles in order
to contract
However there is a region which initiates it
The sinoatrial nodes sends a wave of excitation then the atrium
contracts
The Atrioventricular node sends a
The delay is roughly 0.1 seconds (very short)
This atria will not contract until the ventricle relaxes
Vagus nerve slows the heart coming form the medulla of the
CNS
The accelerator nerve has noradrenaline
If your respiration goes up then your c02 levels will rise a
little and this will be detected by chemoreceptors
Pick up tiny c02 changes in the blood and in response send
signals to the medulla, if raised levels of c02 then the signal
will be sent to the cardiac nerve (cranial nerve) then to the Sino
atrial causes it to produces waves of excitation at a faster rate
therefore the heart rate rises
Why c02 levels fall the medulla sends the signal to the vagus
nerve then it goes to the sinoatrial node and the waves are slowed
so the heart rate slows.
Artery structure
Capillary
IMMUNOLOGY
Neutrophils type of phagocyte
You know its a neutrophil because it has a lobed nucleus:
Monocytes
Macrophages . They patrol the body for invading bad stuff !
Lymphocytes (white blood cell):
B lymphocytes (antibodies)
T lymphocytes (T-helper cells) (cause more b lymphocytes to be
produced)
How to stop bacteria and other pathogens from getting in
Skin
Tears
Mucus membranes vagina, nose, lungs
Cilia in lungs
Earwax
However when they do get in
First there is a non-specific response to the infection
This includes phagocytes (neutrophils and macrophages) detect
self from non-self and complete phagocytosis (will engulf it)
This is an immediate response sometimes this is a sufficient
response
However .
B lymphocytes are constantly circulating in the blood
There are specific b lymphocytes for specific anti gens
ANTIGEN
The correct B l is selected which has the complementary receptor
site
T-helper cells help with mitotic proliferation and many clones
of the antibody are made
Agglutination is when the antigens are bonded together to
prevent them from spreading so it is easier for phagocytes to
ingest them
A macrophage will engulf a bacterial cell and then express the
antigen of the bacteria on its surface so T-helper cells can
respond
HIV infects helper T cells so B cells become inactive