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