Nervous System PDF

Nervous System & Sense Organ Presented by- Rohit Kumar Pal ❑ What is nervous system? The nervous system is a complex collection of nerves and specialized cells known as neurons that transmit signals between different parts of the body. It is essentially the body's elect...

Nervous System & Sense Organ Presented by- Rohit Kumar Pal ❑ What is nervous system? The nervous system is a complex collection of nerves and specialized cells known as neurons that transmit signals between different parts of the body. It is essentially the body's electrical wiring. Types of nervous system  Different type of nerves ❑ There are different types of nerves, according to the action they perform. I. Sensory Nerves – These send messages to the brain from all the sensory organs. II. Motor Nerves – They carry messages from the brain to the muscles in the body. III. Mixed Nerves – They carry the sensory and motor nerves. They help in conducting the incoming sensory information and also the outgoing information to the muscle cells. ❑ Based on which part the nerves connect to the Central Nervous System, they are classified as: I. Cranial Nerves (12 pairs) – They start from the brain and carry messages from the brain to the rest of the body. Certain nerves are sensory nerves while some are mixed nerves. II. Spinal Nerves (31 pairs)– These nerves originate from the Spinal Cord. They carry messages to and from the central nervous system. They consist of mixed nerves.  Special facts ❑Neuron or nerve cell is the structural & functional unit of nervous system ❑Neuron generally remains in the Go phase of the cell cycle ❑In neuron, centrosome is inactive. Hence, it can not divide. ❑Neuron is considered as longest cell of human body. ❑The length of neuron may varies upto 1 meter. ❑In which animal basic nervous system is observed?- Hydra ❑Neurons are generally considered as oldest cell of human body. ❑Largest nerve of human body- sciatic nerve ❑Longest cranial nerve- Vagus nerve ❑Smallest cranial nerve- Trochlear nerve Sciatic nerve & pain Types of Cranial nerves Spinal nerves Neurons Myelinated & non- myelinated nerve ❑Sometimes, the axon contain a insulating layer which is called myelin sheath. Myelin sheath helps in quick and efficient transmission of nerve impulse. Axon without myelin sheath is considered as non- myelinated nerve. ❑Junctions between myelin sheath is called Node of Ranvier. (Helps in jumping/dancing/saltatory conduction) ❑A special cellular structure Schwann cell is also covers myelin sheath where from myelin sheath is produced. ❑Speed of conduction is more fast & rapid in myelinated nerves. Difference at a glance Types of neuron based on processes Synapse(The junction) Synaptic Junction Detail of Synapse Various neurotransmitters Neuroglial cells ❑They are special cells of nervous system that are able to divide and protect the neurons. ❑They are divided into three types- 1) Astrocytes- Supply nutrition between blood capillaries & neurons 2) Microglia- Engulfs foreign bodies & bacteria 3) Oligodendroglia- They forms myelin sheath 4) Ependymal cells- These cell lines the CSF filled ventricles of brain & spinal cord 5) Schwann cells - produce the myelin sheath in the PNS. The myelin sheath protects and insulates axons, maintains their micro- environment, and enables them to regenerate and re-establish connection with receptors or effectors. Enables saltatory conduction. Neurosecretory cells What is gray & white matter? Brain ventricles Human Brain cerebellum  Function of different parts of brain ❑ Cerebrum The cerebrum is the largest part of the brain. It consists of the cerebral cortex and other subcortical structures. It is composed of two cerebral hemispheres that are joined together by heavy, dense bands of fibre called the corpus callosum. The cerebrum is further divided into four sections or lobes: Frontal lobe: It is associated with parts of speech, planning, reasoning, problem-solving and movements. Parietal lobe: Help in movements, the perception of stimuli and orientation. Occipital lobe: It is related to visual processing. Temporal lobe: This region is related to perception and recognition of memory, auditory stimuli, and speech. ❑ Cerebrum Function The cerebrum is responsible for thinking, intelligence, consciousness and memory. It is also responsible for interpreting touch, hearing and vision. Function of different lobes of brain  Thalamus and Hypothalamus ❑ The thalamus is a small structure, located right above the brain stem responsible for relaying sensory information from the sense organ. It is also responsible for transmitting motor information for movement and coordination. ❑ The hypothalamus is a small and essential part of the brain, located precisely below the thalamus. It is considered the primary region of the brain, as it is involved in the following functions: Receives impulses Regulates body temperature (Thermostat) Controls the mood and emotions Controls the sense of taste and smell Synthesizes the body’s essential hormones Coordinates the messages from the autonomous nervous system  Mid and Hind Brain ❑ The midbrain connects the forebrain and the hindbrain. It is associated with motor control, vision, hearing, temperature regulation, alertness. ❑ Hindbrain 1) It is the control centre for visceral function. 2) The hindbrain has three parts, namely – medulla oblongata, pons and cerebellum. 3) The cerebellum (largest part of hindbrain) is responsible for maintaining equilibrium. 4) Medulla oblongata acts as centre for involuntary actions like heart rate, breathing, blood pressure, sleep and waking up, sweating etc.