Nervous System: Classification

Classification of Nervous System

1. Nervous –System: Classification Dr Neeta Gupta Associate Professor Certified Practitioner of EFT & REBT (London) & CBT (Scotland) T DAV PG College Dehradun

2. . Peripheral Nervous System Sense Organs Sensory Afferent Motor Efferent Autonomic Nervous System (Involuntary/Visceral) Somatic Nervous System (Voluntary) Effectors Which Control Skeletal Muscles Effectors Which Control Cardiac, Smooth Muscles and Glands Functions During Relaxation Sympathetic Nervous System Functions during an emergency Fight/ Flight Parasympathetic Nervous System

3. Cranial nerves and spinal nerves are two types of nerves of the peripheral nervous system. The key difference between cranial and spinal nerves is  that the cranial nerves come from the brain while the spinal nerves come from the spinal cord . Spinal nerves are those that emerge directly from segments of the spinal cord. Cranial nerve  transfers information between the brain and the other  parts of the body. Cranial nerves arise from the brain . The nerves Conduct impulses toward or away from the c entral nervous mechanism . In humans  12 pairs of the cranial nerves , are attached to the brain, and, as a rule, 31 pairs of the spinal nerves, are attached to the spinal cord.

4. The autonomic nervous system:  is also called the visceral nervous system because it controls smooth muscle, cardiac muscle, and glands, which make up the viscera of the body. ... These inputs elicit reflex responses through the efferent autonomic nerves.

5. Hypothalamus:  is located in the floor of the third ventricle and is the master control of the autonomic system. It plays a role in controlling behaviours such as hunger, thirst, sleep, and sexual response. It also regulates body temperature, blood pressure, emotions, and secretion of hormones. Thalamus : serves as a relay station for almost all information that comes and goes to the cortex. It plays a role in pain sensation, attention, alertness and memory . Limbic system:  is the center of our emotions, learning, and memory. Included in this system are the cingulate gyri, hypothalamus, amygdala (emotional reactions) and hippocampus (memory ). The septum is considered a part of the limbic system,  mediating the connection between the cortex and subcortical limbic nuclei .

6. Cerebrum:  is the largest part of the brain and is composed of right and left hemispheres. It performs higher functions like interpreting touch, vision and hearing, as well as speech, reasoning, emotions, learning, and fine control of movement. The cerebrum is divided into two halves: the right and left hemispheres .They are joined by a bundle of fibers called the corpus callosum that transmits messages from one side to the other. Each hemisphere controls the opposite side of the body. If a stroke occurs on the right side of the brain, your left arm or leg may be weak or paralyzed . The right hemisphere controls creativity, spatial ability, artistic, and musical skills. The left hemisphere is dominant in hand use and language in about 92% of people .

7. The cerebral hemispheres have distinct fissures, which divide the brain into lobes. Each hemisphere has 4 lobes: frontal, temporal, parietal, and occipital . Frontal lobe Personality, behavior, emotions Judgment, planning, problem solving Speech: speaking and writing ( Broca’s area) Body movement (motor strip) Intelligence, concentration, self awareness Parietal lobe Interprets language, words Sense of touch, pain, temperature (sensory strip) Interprets signals from vision, hearing, motor, sensory and memory Spatial and visual perception

8. Occipital lobe Interprets vision (color, light, movement) Temporal lobe Understanding language (Wernicke’s area) Hearing .

9. Midbrain , also called  mesencephalon , region of the developing  vertebrate   brain  that is composed of the tectum and tegmentum. The midbrain serves important functions in motor movement, particularly movements of the  eye , and in auditory and visual processing. It is located within the  brainstem  and between the two other developmental regions of the brain, the  forebrain  and the hindbrain ; compared with those regions, the midbrain is relatively small. The  tectum  (from Latin for “roof”) makes up the rear portion of the midbrain and is formed by two paired rounded swellings, the superior and inferior colliculi. The  superior colliculus  receives input from the  retina  and the  visual  cortex and participates in a variety of visual reflexes, particularly the tracking of objects in the visual field. The  inferior colliculus  receives both crossed and uncrossed auditory fibres and projects upon the medial geniculate body, the auditory relay nucleus of the  thalamus .

10. The  tegmentum  is located in front of the tectum. It consists of fibre tracts and three regions distinguished by their colour—the red nucleus , that is involved in the coordination of sensorimotor information. T he periaqueductal gray , and the substantia nigra . A smaller number of fibres synapse on large cells in caudal regions of the red nucleus; those give rise to the crossed fibres of the rubrospinal tract, which runs to the  spinal cord  and is influenced by the motor cortex . The  substantia nigra  is a large pigmented cluster of neurons that consists of two parts, the pars reticulata  and the pars compacta.

11. Hindbrain: Pons – The primary role of the pons is to serve as a bridge between various parts of the nervous system, including the cerebellum and cerebrum. Medulla – The primary role of the medulla is regulating our involuntary life sustaining functions such as  breathing, swallowing and heart rate . Cerebellum It has several functions. The most important ones include  balance, motoric activities, walking, standing, and coordination of voluntary movements . It also coordinates muscular activity and speech. It also coordinates eye movements, thus heavily impacting our vision.

12. Spinal Cord; The spinal cord is a long, fragile tubelike structure that begins at the end of the brain stem and continues down almost to the bottom of the spine. The spinal cord consists of bundles of nerve axons forming pathways that carry incoming and outgoing messages between the  brain  and the rest of the body.  Like the brain, the spinal cord is covered by three layers of tissue (meninges). The spinal cord and meninges are contained in the spinal canal, which runs through the center of the spine. .

13. In most adults, the spine is composed of 33 individual back bones (vertebrae). Just as the skull protects the brain, vertebrae protect the spinal cord. The vertebrae are separated by disks made of cartilage, which act as cushions, reducing the forces on the spine generated by movements such as walking and jumping. The vertebrae and disks of cartilage extend the length of the spine and together form the vertebral column, also called the spinal column.

14. What is the dorsal & Ventral root of the spinal cord? Each spinal nerve has two roots, a dorsal or posterior (meaning “toward the back”) one and a ventral or anterior (meaning “toward the front”) one. The dorsal root is  sensory and the ventral root motor ; the first cervical nerve may lack the dorsal root. Oval swellings, the spinal ganglia, characterize the dorsal roots . What happens if the dorsal root is damaged? If the dorsal root of a spinal nerve were severed it would  lead to numbness in certain areas  of the body . What happens if the ventral root is damaged? If the ventral root of a spinal nerve was severely damaged or cut,  it would cut off the pathway of motor information from the spinal cord to the spinal nerve . Therefore, whatever effectors that spinal nerve controlled would no longer work; it would be paralyzed .

15. The Dorsal Horn: The neurons of the dorsal horns receive sensory information that enters the spinal cord via the dorsal roots of the spinal nerves . The dorsal horn functions as  an intermediary processing center  for this information, comprising a complex network of excitatory and inhibitory interneurons as well as projection neurons that transmit the processed somatosensory information from the spinal cord to the brain . The ventral horns contains  the cell bodies of motor neurons that send axons via the ventral roots of the spinal nerves to terminate on striated muscles . ... The lateral columns include axons that travel from the cerebral cortex to contact spinal motor neurons.

16. Mechanism of Simple Reflex Spinal Reflexes are very simlpe and automatic behaviour that occur without conscious, voluntary action of the brain. When you are exposed to flame, receptor cells in your fingertips respond to the flame, sending neural impulses racing along sensory neurons, through a dorsal root and into the spinal cord. Impulses travel to interneurons and go right back out of the spinal cord (through ventral root) on motor neurons to your arms and hand where muscles are stimulated to contract and your hand jerks back from the flame. So this is the simple relex impulse.

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