Nervous system ppt.pptx

Human Anatomy and Physiology

1. THE NERVOUS SYSTEM Dr.P.Thirunagalinga Pandiyan M.Sc., (N) Ph.D.,(N) College of Nursing Madurai Medical College, Madurai. India.

2. THE NERVOUS SYSTEM

3. THE NERVOUS SYSTEM The human nervous system is divided into two parts : The Central Nervous System (CNS) The Peripheral Nervous System ( PNS)

4. NERVOUS SYSTEM The CNS includes the brain and the spinal cord The PNS comprises of all the nerves of the body associated with the CNS (brain and spinal cord). The nerve fibres of the PNS are of two types : (a) Afferent fibres - transmit impulses from tissues/organs to the CNS (b) Efferent fibres - transmit regulatory impulses from the CNS to the concerned peripheral tissues/organs.

5. THE NERVOUS SYSTEM The PNS is divided into two divisions called Somatic nervous system – Transmit impulse from the CNS to skeletal muscles Autonomic nervous system - Transmits impulses from the CNS to the involuntary organs and smooth muscles of the body .

6. THE NERVOUS SYSTEM The autonomic nervous system is further classified into Sympathetic nervous system – excitement and energy loss Parasympathetic nervous system – calmness and energy savers

7. NEURON Neurons (also called neurones or nerve cells) are the fundamental units of the brain and nervous system, the cells. It is responsible for receiving sensory input from the external world, for sending motor commands to our muscles, and for transforming and relaying the electrical signals at every step in between.

8. NEURON A neuron is a microscopic structure composed of three major parts, namely Cell Body Dendrites Axon The cell body contains cytoplasm with typical cell organelles and certain granular bodies called Nissl’s granules . Center there is nucleus Short fibers which branch repeatedly and project out of the cell body is dendrites

9. NEURON Each branch terminates as a bulb-like structure called synaptic knob or axon terminals It is covered by sheath called myelin sheath The gaps between two adjacent myelin sheaths are called nodes of Ranvier . The myelinated nerve fibres are enveloped with Schwann cell

10. CENTRAL NERVOUS SYSTEM The Brain The Spinal cord These organs work together to integrate and coordinate sensory and motor information for the purpose of controlling the various tissues, organs, and organ systems of the body. The central nervous system is responsible for higher neural functions, such as memory, learning, and emotion.

11. CENTRAL NERVOUS SYSTEM Brain is situated in the skull. It is continued as spinal cord in the vertebral canal through the foramen magnum Brain and spinal cord are surrounded by three layers of meninges called the outer dura mater, middle arachnoid mater and inner pia mater.

12. CENTRAL NERVOUS SYSTEM The space between arachnoid mater and pia mater is known as subarachnoid space. This space is filled with a fluid called cerebrospinal fluid. Brain and spinal cord are actually suspended in the cerebrospinal fluid.

13. Parts of Brain Brain consists of three major divisions: 1. Prosencephalon 2. Mesencephalon 3. Rhombencephalon

14. BRAIN Brain Weighs about nearly 1.3 kgs in adults 75 % water 20 % of oxygen Contains over 100 billion neurons Controls bodily functions and interactions with the outside world

15. BRAIN Four Parts: Cerebrum Diencephalons Brain stem Cerebellum

16. CEREBRUM Located above the cerebellum. Contains two hemispheres with an outer portion called the cerebral cortex. The two hemispheres are connected by a bridge of nerve fibers that relay information between the two hemispheres called the corpus callosum . The left and right lobes are each divided into four lobes or parts Frontal lobe Parietal lobe Temporal lobe Occipital lobe 

17. CEREBRUM Frontal lobe.   The largest lobe of the brain, located in the front of the head, the frontal lobe is involved in personality characteristics, decision-making and movement . Recognition of smell usually involves parts of the frontal lobe. The frontal lobe contains Broca’s area, which is associated with speech

18. CEREBRUM Parietal lobe.  The middle part of the brain, the parietal lobe helps a person identify objects and understand spatial relationships The parietal lobe is also involved in interpreting pain and touch in the body. The parietal lobe houses Wernicke’s area, which helps the brain understand spoken language.

19. CEREBRUM Occipital lobe The occipital lobe is the back part of the brain that is involved with vision. Temporal lobe  The sides of the brain, temporal lobes are involved in short-term memory, speech, musical rhythm and some degree of smell recognition.

20. CEREBRUM – FUNCTIONS The cerebrum (front of brain) comprises gray matter (the cerebral cortex) and white matter at its center. It is covered with ridges (gyri) and folds (sulci).  The largest part of the brain, the cerebrum initiates and coordinates movement and regulates temperature. Other areas of the cerebrum enable speech, judgment, thinking and reasoning, problem-solving, emotions and learning. Other functions relate to vision, hearing, touch and other senses.

21. DIENCEPHALON The deep portion of the brain containing: • Thalamus Hypothalamus Epithalamus

22. BRAINSTEM The brainstem (middle of brain) connects the cerebrum with the spinal cord. The brainstem includes The Midbrain The Pons The Medulla

23. BRAINSTEM Midbrain : Involved with visual reflexes Pons : • Located between the midbrain and the medulla oblongata. It Controls certain respiratory functions Medulla Oblongata: Contains centers that regulate heart and lung functioning, swallowing, coughing, vomiting and sneezing

24. CEREBELLUM Area that coordinates musculoskeletal movement to maintain posture, balance, and muscle tone. Inferior to the occipital lobes of the cerebrum.Posterior to the pons and medulla oblongata .

25. Deeper Structures Within the Brain Pituitary Gland Sometimes called the “master gland,” the pituitary gland is a pea-sized structure found deep in the brain behind the bridge of the nose . Thalamus The primary function of the thalamus is to relay motor and sensory signals to the cerebral cortex. It also regulates sleep, alertness, and wakefulness. Hypothalamus The hypothalamus is located above the pituitary gland and sends it chemical messages that control its function. It regulates body temperature, synchronizes sleep patterns, controls hunger and thirst 

26. Deeper Structures Within the Brain Amygdala Small, almond-shaped structures, an amygdala is located under each half (hemisphere) of the brain. Included in the limbic system, the amygdalae regulate emotion and memory and are associated with the brain’s reward system, stress, and the “fight or flight” response when someone perceives a threat. Hippocampus A curved seahorse-shaped organ on the underside of each temporal lobe. It supports memory, learning, navigation and perception of space

27. Deeper Structures Within the Brain Pineal Gland The pineal gland is located deep in the brain and attached by a stalk to the top of the third ventricle. The pineal gland responds to light and dark and secretes melatonin, which regulates circadian rhythms and the sleep-wake cycle.

28. Blood Supply to the Brain Two sets of blood vessels supply blood and oxygen to the brain: the  vertebral arteries  and the  carotid arteries. The external carotid arteries extend up the sides of neck and The internal carotid arteries branch into the skull and circulate blood to the front part of the brain. The vertebral arteries follow the spinal column into the skull, where they join together at the brainstem and form the  basilar artery , which supplies blood to the rear portions of the brain. The  circle of Willis , a loop of blood vessels near the bottom of the brain that connects major arteries, circulates blood from the front of the brain to the back and helps the arterial systems communicate with one another.

29. Circle of willis

30. SPINAL CORD Situation and Extent Spinal cord lies loosely in the vertebral canal. It extends from foramen magnum to the lower border of first lumbar vertebra below.

31. SPINAL CORD Coverings Spinal cord is covered by sheaths called meninges, which are membranous in nature. Meninges are dura mater , pia mater and arachnoid mater.

32. SPINAL CORD Shape and Length Spinal cord is cylindrical in shape. Length of the spinal cord is about 45 cm in males and about 43 cm in females

33. SPINAL CORD Segments 1. Cervical segments/Cervical spinal nerves = 8 2. Thoracic segments/Thoracic spinal nerves = 12 3. Lumbar segments/Lumbar spinal nerves = 5 4. Sacral segments/Sacral spinal nerves = 5 5. Coccygeal segment/Coccygeal spinal nerves = 1 Total = 31

34. SPINAL CORD Spinal Nerves Segments of spinal cord correspond to 31 pairs of spinal nerves in a symmetrical manner.

35. PERIPHERAL NERVOUS SYSTEM Peripheral Nervous System Consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves 

36. CRANIAL NERVES – 12 PAIRS

37. SPINAL NERVES  1. Cervical segments/Cervical spinal nerves = 8 2. Thoracic segments/Thoracic spinal nerves = 12 3. Lumbar segments/Lumbar spinal nerves = 5 4. Sacral segments/Sacral spinal nerves = 5 5. Coccygeal segment/Coccygeal spinal nerves = 1 Total = 31