The CNS consists of the brain, the cranial nerves and the spinal cord.Ĭranial nerve -In humans, there are 12 cranial nerves. It consists of the medulla oblongata, the part responsible for cardiac and respiratory control, the midbrain, which is involved in basic, involuntary body functions, and the pons, where some cranial nerves originate.Ĭentral nervous system (CNS) -One of two major divisions of the nervous system. It is a complicated neural center with several neuronal pathways between the cerebrum, spinal cord, cerebellum, and motor and sensory functions of the head and neck. At the end of the axons, nerve impulses are transmitted to other nerve cells or to effector organs.īrachial plexus -A group of lower neck and upper back spinal nerves supplying the arm, forearm and hand.īrain stem -Lowest part of the brain that connects with the spinal cord. Neurons communicate with each other by transmitting signals from branches located at the end of their axons. Each neuron has one axon, which can be longer than a foot.
trochlear nerve, a motor nerve for eyeball muscle control.oculomotor nerve, a motor nerve for eyelid and eyeball muscle control.optic nerve, a sensory nerve for vision.olfactory nerve, a sensory nerve for the sense of smell.The nerves of the sensory-somatic system are: THE CRANIAL NERVES (12 PAIRS). This is called voluntary contraction of the skeletal muscles. When these nerves are stimulated, they cause the skeletal muscles to contract. The motor division, also called the efferent division, contains pathways that go from the brain stem and spinal cord to the lower motor neurons of the cranial and spinal nerves. These signals are conveyed to the cranial and spinal nerves. The sensory division, also called the afferent division, contains neurons that receive signals from the tendons, joints, skin, skeletal muscles, eyes, nose, ears and tongue, and many other tissues and organs. The somatic nervous system (SNS) consists of sensory and motor nerve divisions. The ANS is further divided by function into sympathetic and parasympathetic systems. The PNS is subdivided into the somatic nervous system (SNS) and the autonomic nervous system (ANS). The nervous system of the human body is divided into the central nervous system (CNS), consisting of the spinal cord and brain, and the peripheral nervous system (PNS), consisting of all the nerves that connect the CNS with organs, muscles, blood vessels and glands. There are two types of neurons found in the SNS: sensory neurons, which typically have long dendrites and short axons, and carry messages from sensory receptors to the CNS, and motor neurons, which have a long axon and short dendrites and transmit signals from the CNS to muscles or glands. Neurons are also the longest cells of the body, a single axon can be several feet long. The average adult brain contains about 100 billion neurons. Both axons and dendrites are surrounded by a white protective coating called the myelin sheath.
The dendrites receive information from other nearby cells and transmit the signals to the soma and the axon carries signals away from the neuron. NeuronsĪ neuron consists of a cell body, the soma, which contains the nucleus and surrounding cytoplasm, several short thread-like projections, called dendrites, and of one long filament, called the axon. Neurons transmit nerve signals and are surrounded by glial cells, that provide mechanical and physical support as well as electrical insulation between neurons. Description Nervous tissueĪll nervous tissue-including that of the SNS-consists of two main cell types: neurons and glial cells. Sensory nerves convey nerve impulses from the sense organs to the central nervous system (CNS), while motor nerves convey nerve impulses from the CNS to skeletal muscle effectors. It includes both sensory and motor nerves.
The SNS controls voluntary activities, such as movement of skeletal muscles. The somatic nervous system (SNS) is a division of the peripheral nervous system (PNS).
0 kommentar(er)
