NERVOUS SYSTEM
The Nervous system receives sensory input from the internal and external environment. It then integrates the input in the sensory centers of the brain and responds to the various stimuli with a motor output, which can be converted by the organs to some form of energy ie. movement, release of hormones, changes in heart rate. The response is not always conscious, for instance if you were climbing a mountain and the air became thinner, you would start breathing deeper and quicker. Was this response voluntary? Of course not, the nervous system assessed the situation and responded accordingly.
The Endocrine System
Some animals have a second response system, the endocrine syst ...view middle of the document...
Bilaterally symmetrical creatures have a defined head and tail region. Scientists believe bilateral symmetry has a lot to do with cephalisation (the development of a head with the majority of sensory organs at the front end of the organism). Flatworms have small clusters of bundled neurons (known as ganglia) throughout their body, forming a small brain.
The Vertebrate Nervous System
Vertebrates have a spinal cord as well as a more developed brain.The vertebrate nervous system is subdivided into many parts, the central nervous system, the peripheral nervous system, motor neuron pathways - of which there are two types - somatic (skeletal) and autonomic (glands, cardiac muscle, and smooth muscle). The autonomic nervous system is dived into two sections, the sympathetic and the parasympathetic systems.
The Brain
Bone-skull and vertebrae surround the CNS. Fluid and tissue insulate the brain and spinal cord. The brain is comprised
of three parts, the cerebrum which is the seat of consciousness, the cerebellum and the medulla oblongata, which are part of the unconscious brain. The medulla oblongata, the closest to the spinal cord, is involved with the regulation of breathing, heartbeat, vasoconstriction (blood pressure), and reflex centers for sneezing, coughing, vomiting, hiccupping and swallowing. The hypothalamus is the gland which regulates homeostasis. It has regulatory areas for hunger, thirst, body temperature, blood pressure and water balance and links the nervous system to the endocrine system. The thalamus serves as a relay to incoming nervous messages.
The cerebellum is the second largest part of the brain, after the cerebrum. Its functions are muscle coordination and maintaining normal muscle tone and posture, it also coordinates balance. In birds, reptiles and mammals, the cerebrum coordinates motor functions and sensory data. The cerebrum governs intelligence and reasoning, memory and learning.
The peripheral nervous system
The peripheral nervous system (PNS) connects the central nervous system (CNS) to the rest of the body through a series of nerves. Cranial nerves in the peripheral nervous system take impulses to and from the central nervous system. Spinal nerves take impulses to and from the spinal cord. Two main components of the peripheral nervous system are, the sensory (afferent) pathways that provide input from the body into the CNS and motor (efferent) pathways that carry signals to muscles and glands (effectors). The input that reaches the conscious level is what gives us a perception of our external environment.
The Somatic Nervous system
The somatic (skeletal) nervous system includes all nerves controlling the muscular system and external sensory receptors. External sense organs (including skin) are receptors. The reflex arc is an automatic, involuntary reaction to stimuli. When the doctor taps your knee with the "rubber hammer", he or she is testing your reflexes. This is an involuntary response to stimuli; ...
