Nervous System

• It is considered as the command center of the body.

  Nervous System
• It is mainly composed of the brain, the spinal cord, and the nerves.
• There are three main or primary functions of the nervous system these are: Sensory, Integrative, and Motor.
• Sensory Function detects both internal and external stimuli by sensory receptors.
• Integrative Function of the nervous system is responsible for processing, analyzing, and responding to sensory information.
• Motor Function comes after the integration of the information, the nervous system sends a motor response to stimulate effectors (muscles and glands) that allows or is responsible for both voluntary and involuntary movements.
• 1. Maintaining homeostasis
  2. Receiving sensory input (External and internal stimuli or the ability to respond to stimuli)
  3. Integrating information (processing sensory input and initiating responses)
  4. Controlling muscles and glands (contraction of muscles through the stimulation of the nervous system)
  5. Establishing and maintaining mental activity (consciousness, thinking, memory, emotions)
• The nervous system has two major divisions: (a.) The Central Nervous System (CNS) and (b.) The Peripheral Nervous System (PNS)
• The central nervous system consists of the brain and the spinal cord.
• This can also be referred to as the key decision maker since it processes different sensory information, it is the source of thoughts, emotions, memories, and stimulation of most muscles to contract and for glands to secrete. It is also Involved in receiving information from the body, processing and sending information or response to the body.

  Central Nervous System
• The Peripheral nervous system consists of the nerves (cranial nerves and spinal nerves), Ganglia, and Sensory receptors.
• It can also be referred to as the messenger since it detects the stimuli in and around the body and sends it to the CNS and then communicates messages or responses from the CNS to the body.

  Peripheral Nervous System
• The peripheral nervous system has two primary divisions namely: the sensory division and the motor division.
• The sensory division is also known as the afferent division (afferent = toward) since it transmits electrical signals or conveys input INTO the CNS from the sensory receptors of the body
• The motor division is also known as the efferent division (efferent = away) since it transmits electrical signals or conveys output FROM the CNS to effector organs or muscles and glands.
• The motor division is divided into two branches: (1) the somatic nervous system and (2) the autonomic nervous system.
• The Somatic Nervous System (SNS) is the voluntary or conscious division of the motor division. It involves the conveying of output from the CNS to the skeletal muscles causing the decision to move the skeletal muscles, since the motor responses are controlled consciously and voluntarily.
• The Autonomic Nervous System (ANS) involves the involuntary or unconscious division of the motor division. It conveys the output of the CNS to smooth muscle, cardiac muscle, and glands.
• The autonomic nervous system is then divided or composed of three branches: (1) the sympathetic division and (2) the parasympathetic division, these branches help in regulating functions throughout the body.
• The sympathetic division, also called the “fight-or-flight” division since it helps and prepares the body in physical activities, exercise, or emergency actions.
• The parasympathetic division, also called the “rest-and-digest” division because it helps and regulates the resting functions.
• The enteric nervous system is vital in regulating motility and secretion and it consists of neuronal networks within the way of the digestive tract.
• The two cell types that make up the nervous system, neurons and glial cells, work together to monitor the body’s environment and make changes when needed.
• Neurons or nerve cells, are the primary functional cells of the nervous system responsible for transmitting electrical signals.
• Neurons consist of 3 main different parts.
• Also known as perikaryon or soma, the cell body is the core section of the neuron. It contains a nucleus surrounded by cytoplasm that includes typical cellular organelles such as lysosomes, mitochondria, and a Golgi complex.
• An axon is a long, tail-like structure. It joins the cell body at a specialized junction called the axon hillock.
• The cell body contains genetic information, maintains the neuron’s structure, and provides energy to drive activities.
• In most neurons, a single axon arises from a cone-shaped area of the neuron cell body called the axon hillock.
• Many axons remain as a single structure, but others branch to form collateral axons, or side branches.
• The cytoplasm of an axon is called the axoplasm
• The plasma membrane of an axon is called the axolemma
• Dendrites are fibrous roots that branch out from the cell body.
• Like antennae, dendrites receive and process signals from the axons of other neurons.
• Neurons can have more than one set of dendrites, known as dendritic trees.
• Based on the number of dendrites, there are four major structural categories: (1) multipolar, (2) bipolar, (3) pseudo-unipolar, and (4) anaxonic.
• Multipolar neurons (multi, many) have many dendrites and a single axon.
• Motor neurons of the PNS and most of the neurons within the CNS are multipolar
• Multipolar neurons (multi, many) have many dendrites and a single axon. The dendrites vary in number and in their degree of branching.
• Bipolar neurons (bi, two) have two processes: one dendrite and one axon. The dendrite is often specialized to receive the stimulus, and the axon conducts action potentials. Bipolar neurons are located in some sensory organs, such as in the retina of the eye and in the nasal cavity.