Functions of Blood

Cells are continously adding waste products, secretions and metabolites to blood whil taking from it vital nutrients, oxygen, hormones and other substances.
Overall, blood performs the following functions:
1.
Transports oxygen from the lungs to body tissues and transports the waste products of cellular metabolism and nutrients, hormones and enzymes.
2.
Regulates blood clotting, body temperature, acid-base balance, water and electrolytes.
3.
Protects against harmful organisms through white cells and antibodies.

CENTRAL NERVOUS SYSTEM

-The central nervous system is divided in two parts: the brain and the spinal cord.

Ear

The ear is the organ that detects sound. The vertebrate ear shows a common biology from fish to humans, with variations in structure according to order and species. It not only acts as a receiver for sound, but plays a major role in the sense of balance and body position. The ear is part of the auditory system.

Eye

Eyes are organs that detect light, and send signals along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system.

The simplest "eyes", such as those in unicellular organism, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms.

Nervous system and the senses

Central nervous system

The central nervous system is the part of the nervous system that functions to coordinate the activity of all parts of the bodies of multicellular organisms.

It contains the majority of the nervous system and consists of the brain and the spinal cord.

Peripheral Nervous system

Together with the peripheral nervous system it has a fundamental role in the control of behavior.

The neurons can be functionally divide in three ways:
- Sensory (afferent) -> Carry information INTO the central nervous system from sense organs of motor. (efferent) -> Carry information away from the nervous system (for muscle control).
- Cranial -> Connects the brain with the periphery or spinal - connects he spinal cord with the periphery.
- Somatic -> Connects the skin or musclewith the central nervous system or visceral - connects the internal organs with the central nervous system.