Bio - Systems

Mechanoreceptors

respond to mechanical energy (pressure, touch, stretch, etc.)

Chemoreceptors

solute concentration and different kind of molecules

Electromagnetic receptor

Electromagnetic energy (visible light, electricity, magnetism)

Thermoreceptors

Hot and cold. Found in skin and anterior hypothalamus

Pain receptors

Extreme pressure or temperature

Steps of sensory pathway

Sensory reception, transduction, transmission, perception

Systems involved in locomotion

Joints, bones, muscles, nerves

Pivot joint - forearms at elbows, head from side to side

Hinge joint - restricts movement to single plane

movement in two planes, circumduction

Ball and socket joint - shoulder, rotation

Condyloid joint - wrists, knuckles, prevents axial rotation

Plane joint - shock absorbance, limited gliding

Synovial joints

capsules that surround the articulating surfaces of two bones

Joint capsule

Seals the joint space and provides stability by restricting the range of possible movements

Cartilage

Lines the bone surface to facilitate smoother movement, as well as absorbing shock and distributing load

Synovial fluid

Provides oxygen and nutrition to the cartilage, as well as lubrication (reduces friction)

Humerus

Bone between bicep and tricep, anchors muscle

Radius

Upper bone in forearm, acts as a forearm lever for biceps

Ulna

Bone underneath in forearm, acts as a forearm lever for triceps

Bicep

bends the forearm

Tricep

Straightens the forearm

Skeletal muscle

Voluntary movement of bones, fibres run in parallel tracts and are multinucleated and heavily striated

Smooth muscle

Lining of internal organs, involuntary constriction of these regions, fibres are not striated, have a spindle shape and each fibre contains a single central nucleus

Cardiac muscle

rhythmic contraction of the heart, fibres are branching, intercalated, lightly striated and have a single nucleus per fibre

Myofibrils

alternating fibers of myosin and actin

Thin filaments

actin

Thick filaments

myosin

A single contractile unit of Myofibril

Sarcomere

Z line

Holds actin filaments

M line

Holds myosin filaments

Tropomyosin

wraps around actin filaments

Troponin complex

a group of three regulatory proteins (Troponin C, I, and T), have a calcium binding site

Antigen

Part/fragment of a pathogen that is recognized by immune cells as foreign, eliciting an immune response

Antigen presenting cell

Any cell that is presenting/exposing a fragment of the pathogen (Antigen) on its surface

Major Histocompatibility Complex (MHC)

Protein complexes that an antigen presenting cell (above) uses to present/expose a fragment of the invading pathogen (Antigen) to Immune cells, thereby evoking further action by immune cells

Leukocyte

White blood cell. They carry out immune functions by removing/killing pathogens

Lymphocytes

leukocytes of Adaptive immune system (B and T cells)

Neutrophils

Most abundant phagocyte. Found in blood. Short-lived cells

Macrophage

Most effective phagocytes. In spleen/lymph nodes in order to screen. Long lived.

Eosinophils

Low phagocytic ability. Surround multicellular pathogens and release destructive enzymes

Dendric cells

Alert adaptive immune system (Professional APC).

Natural killer cells

Recognise and kill cancerous and viral infected cells. Release cytotoxic molecules.

Cytokines

Chemicals released by immune cells to alert other immune cells of an infection and activate them. Some cytokines prevent viral replication and more

Antibody

(Immunoglobulin): A Y protein produced and secreted by the B Lymphocytes. Antibody is a protein that binds to other proteins

How do immune cells recognize the pathogens?

Immune cells have special receptors (mainly on their surface) that recognizes strange/foreign/nonself molecules on the surface of pathogens

Humoral immune response

B lymphocyte and antibody production

Cell-mediated immune response

T lymphocytes

• Fight and kill pathogens

• Kill pathogen infected cells

• Help B lymphocytes to do their job too

Barrier defences

Skin, mucus, secretions, cilia, acidity in stomach, lysosomes in saliva

Hemocytes

Invertebrate immune cells

Mucociliary escalator

mucus and cillia

Foreign antigens

Unique lipopolysaccharide, double stranded RNA, CpG

Toll-Like Receptors (TLR)

Receptors often recognized as a feature of a pathogen

TLR3

Double stranded RNA

TLR5

FLagellin

TLR4

lipopolysaccharides

TLR9

CpG DNA

BCR - Receptors of B lymphocytes

ecognize and bind to an antigen without the help of an antigen presenting cell

What happens after a BCR recognizes and gets attached to an antigen?

• That B cell is now activated and goes through multiple rounds of division

• In the process refines its receptor for better binding to the same antigen

• During the same process this expanding clone of B cell makes and remakes antibodies for the same antigen

• Finally, majority of this B cell clone will differentiate/become so called Plasma cells.

Plasma cells

make and release the antibodies they were making to the pathogen.

Memory cells

already there and “remember” the pathogen and its antigen

Major Histocompatibility Complexes (MHC).

There are proteins in cells that bring the antigen to the surface and present it.

MHC of normal body cells

Class I MHC

MHC of immune cells

Class ll MHC

Class I MHC presenting antigen

T cell that binds to it through its T cell receptor releases chemicals that kill the presenting cell

Class ll MHC presenting antigen

T cell that binds to it through its T cell receptor gets activated and goes on to either differentiate into an effector T cell (to kill the pathogens or pathogen infected cells that it might encounter in the future) or help activate other Immune cells such as a B lymphocyte (B cell).

Helper T cell

Gets activated when an antigen presenting cell has presented the antigen to Helper T cells by their MHC-antigen complex. It activates both B Lymphocytes and Cytotoxic T cells by releasing cytokines

CD4

Accessory protein of Helper T cells. Can only enable T cell receptor to associate with MHC II class

Cytotoxic T cell

Gets activated when an antigen presenting cell has presented the antigen to the Helper T cell by their MHC-antigen complex. Its role is killing the infected host cells.

Chemicals released by cytotoxic T cells

(perforin and Granzymes). Perforins assemble on the membrane of the infected cells, creating a hole through which granzymes enter and destroy the infected cell.

Structure of B cell receptor

Two identical heavy chains linked by several disulfide bridges

Structure of T cell receptor

One alpha chain and one beta chain linked by disulfide bridge

Viral neutralization

Antibodies produced against a spike protein of the virus’s, simply bind to that spike protein. These spike proteins on the virus are now ‘‘masked’’ and are longer at disposition of the virus to infect any other cell, since they are covered by antibodies! This simply neutralizes the virus and is a good short term protection against infection.

Opsonization

The presence of antibodies on their surface acts like a flag to other immune cells and enables other phagocytes to eat up the pathogen in question with ease. This process of marking a pathogen for phagocytosis is called Opsonization.

Complement system

Collection of proteins that are ever present in your bloodstream. Binding of an antibody to the antigen on the surface of a pathogen, activates the complement system by recruiting the complement proteins to the surface of the pathogen. Activated complement proteins assemble, making a membrane attack complex culminating in formation of a pore/hole on the membrane of a pathogen. A cell with an opening on its membrane that cannot be controlled by the cell itself is a dead cell.

Function of lymphatic system

screen the interstitial fluid

Glycogen

Polysaccharide, stored in the liver and muscles. Can be hydrolyzed and turned to glucose

Negative feedback loop of stomach

• Stomach is very acidic

• The sudden presence of acidity in the duodenum provokes some endocrine cells (S cells) to secrete Secretin

• Secretin reaches Pancreas through blood and makes it release Bicarbonate into intestines, raising the pH to normal levels

Positive feedback loop of breastfeeding

• Suckling of a mother’s nipple produces a stimulus

• The stimulus travels through sensory neurons to hypothalamus, which releases Oxytocin in the posterior pituitary.

• From posterior pituitary, Oxytocin enters blood and provokes mammary glands to make milk.

Hypothalamus

Hormones released from the posterior pituitary and hormones that regulate the anterior pituitary

Pituitary gland

Oxytocin, Antidiuretic hormone (ADH), GH, Prolactin, Follicle-Stimulating hormone, LH, Thyroid-stimulating hormone, Adrenocorticotropic hormone

Oxytocin

Stimulates contraction of uterus and mammary glands

Antidiuretic hormone

Promotes retention of H2O by kidneys

Prolactin

Stimulates milk production and secretion

LH

stimulates ovaries and testes

Thyroid gland

T3, T4, Calcitonin

T3 and T4

Maintains metabolic processes

Calcitonin

Lowers blood calcium levels

Parathyroid glands

Parathyroid hormone

Parathyroid hormone

Raises blood calcium levels

Pancreas

Insulin and Glucagon

Adrenal medulla

Epinephrine, norephrine

Adrenal cortex

Glucocorticoids, mineralcorticoids

Ephinephrine and norepinephrine

Raises blood glucose levels, increases metabolic activities, constricts certain blood vessels

Glucocorticoids

Raise blood glucose levels

Mineralocorticoids

Promotes reabsorption of Na and excretion of K in kidneys

Normal blood glucose levels

90mg/100ml

Beta cells

make insulin

alpha cells

make glucagon

Islets of Langerhans

Cluster of cells in pancreas