The frontalis, orbicularis oris, laris oculi, buccinators and zygomaticus are muscles that are responsible for showing facial expressions such as surprise, anger, fear, disgust, amongst other emotions.
The temporalis and the masseter muscle are responsible for chewing movements.
The sterncleidomastoid and trapezius are neck muscles and can be associated with the throat.
The principal organs that comprise the nervous system are the brain, spinal cord, nerves and ganglia. These organs also consist of various tissues including nerve, blood and connective tissue. All together the organs and various tissues carry out the activities of the ...view middle of the document...
The brain and spinal cord are the organs of the central nervous system. Because they are so vitally important, the brain and spinal cord, located in the dorsal body cavity, are encased in bone for protection. The brain is in the cranial vault and the spinal cord is in the vertebral canal of the vertebral column. In addition to bone, the central nervous system is surrounded by connective tissue membranes, called meninges and by cerebrospinal fluid.
The brain is divided into the cerebrum, diencephalon, brain stem and cerebellum.
The largest portion of the brain is the cerebrum which is divided into two cerebral hemispheres. The two hemispheres are two separate entities.
The diencephalon is centrally located and is nearly surrounded by the cerebral hemispheres. The thalamus, which makes up about 80% of the diencephalon, consists of two oval masses of grey matter that serve as relay stations for sensory impulses, except for the sense of smell, going to the cerebral cortex.
The cerebellum is the second largest portion of the brain. Three bundles of myelinated nerve fibres, called cerebellar peduncles, form communication pathways between the cerebellum and other parts of the central nervous system.
The spinal cord extends from the base of the skull to the level of the fist lumbar vertebra and like the brain, it is surrounded by bone, meniges and cerebrospinal fluid. The spinal cord is divided into 31 segments and each segment gives rise to a pair of spinal nerves.
The spinal cord as two main functions. The first is serving as a conduction pathway for impulses going to and from the brain. The second is serving as a reflex centre. The reflex arc is the functional unit of the nervous system. Many reflexes are mediated in the spinal cord without going to the higher brain centres as they are responses to stimuli and do not require conscious thought and require more quickly than reactions that require thought process.
The second of the two subdivisions is the peripheral nervous system. The organs that make up this system are the nerves and ganglia. Nerves are bundles of nerve fibres and ganglia are collections of nerve cells outside the central nervous system.
The peripheral nervous system is further divided into a sensory division which transmits impulses from the peripheral organs to the central nervous system and a motor division which transmits impulses from the central nervous system out to the peripheral organs to cause an affect or action.
The peripheral nervous system consists of the nerves that branch out from the brain and spinal cord and it is these nerves that form the communication network between the central nervous system and the body parts. The peripheral nervous system is further subdivided into the somatic nervous system and the autonomic nervous system. The somatic nervous system consists of nerves that go to the skin and muscles and is involved in conscious activities. The autonomic nervous...