The Nervous System

1. The Nervous System By: Kaylen Bunch & Kenzie Murphy

2. Major Structures • Central Nervous System (CNS): • Brain & Spinal Cord • Peripheral Nervous System (PNS): • Network of nerves & Neural tissues • Major Function: Sends signals threw the brain and spinal cord to the rest of the body.

3. Neurons • Specialized conductors of impulses that enable the body to interact with it's internal and external environments.

4. Neurons • Neuroglia: supporting tissue • Axon: long slender projection of a nerve cell that conduct impulses away from the cell body. • Dendrites: Are short & unsheathed, & transmit impulses to the cell body.

5. Neurons

6. Neurons • Motor Neurons: Contractions in muscles & secretions from glands & organs. • Sensory Neurons: Attached to sensory receptors & transmit impulses to CNS. • Interneurons: Mediate impulses between sensory & motor neurons.

7. Nerve Fibers • A single elongated process. • PNS fibers: Wrapped by sheaths containing Schwann cells, so damage is reversible, • CNS fibers: No Schwann cells, so permanent damage.

8. Nerves: a bundle of nerve fibers that connect to various parts of the body • Afferent: Conducting to the CNS • Efferent: Conducting to muscles, organs, & glands. • Mixed: Mixture of afferent and efferent.

10. Nerve Impulse • All or None Principle: No transmission occurs until the stimulus reaches a minimum strength then a maximum impulse is produced. • Synapse: A specialized knoblike branch ending. • Neurotransmitter: chemical agent helper.

11. Central Nervous System (CNS)

12. CNS: Central Nervous System • Brain and Spinal Cord • Divided into white and gray matter. • Spinal Cord’s gray matter is in a “H” shape.

13. Brain • The nervous tissue consists of millions of nerve cells & fibers • Male- 1380g. or 3.04lbs. • Female- 1250g. or 2.75lbs. • Function: • Receives information from the body • Interprets it • Gives a response to it • Helps perform vital operations

14. Brain (Meninges) • 3 membranes that enclose the brain. • Meninges support blood vessels and contain cerebrospinal fluid. • Pia mater - inner layer • Arachnoid – middle layer • Dura mater – outer layer

16. Cerebrum • Description: Divided by the longitudinal fissure into 2 cerebral hemispheres. • Function: Contains nerve centers that govern all sensory and motor activity. • They are joined by large fiber tracts that allow information to pass between them.

17. Left Right

18. Cerebrum • The surface of each hemisphere is arranged in folds creating bulges(convolution) & shallow furrows( sulcus). • Cerebral Cortex: The surface of each hemisphere, composed of gray, unmyelinated cell bodies. • Divided into lobes to identify certain locations.

19. Cerebrum Lobes • Frontal: Major motor area, site for personality, & speech. • Parietal: Contains centers for sensory input from all parts of the body & is the site for the interpretation of language. • Temporal: Contains centers for hearing, smell, & language input. • Occipital: Primary sensory area for vision.

22. Cerebellum • Occupies a place in the back of the skull, is oval shaped & divided into lobes by deep fissures. Is also connected to every part of the CNS. • Function: Coordination of voluntary & involuntary complex patterns of movement & adjusts muscles to automatically maintain posture.

23. Cerebellum

24. Diencephalon • Thalamus: Relay center for all sensory & motor impulses being transmitted to the sensory & motor areas. • Hypothalamus: Regulates autonomic nervous activity & contains neurosecretions used to control metabolic activities.

26. Brainstem • Contains centers that process visual, auditory, & sensory data & relay information to & from the cerebrum. • Midbrain: below cerebrum & above pons. • Contains 4 small masses of grey cells that are associated with visual reflexes & sense of hearing.

27. Brainstem • Pons: broad band of white matter • Contains fiber tracts linking the cerebellum & medulla to higher cortical areas. • Plays a role in somatic & visceral motor control.

28. Brainstem • Medulla Oblongata: Connects the pons & the rest of the brain to the spinal cord. • Acts as the cardiac, respiratory, & vasomotor control centers. • Controls • Breathing • Swallowing • Coughing • Sneezing • Vomiting • Heartbeat • Arterial blood pressure

30. Spinal Cord • Adult cord is about 44 cm. long. • Function: • Conduct sensory impulses to the brain • Conduct motor impulses from the brain • Reflex center for impulses entering & leaving spinal cord without involvement of the brain.

31. Spinal Cord • Conus Medullaris: Between 12th thoracic & 1st lumbar vertebra. The cord becomes conically tapered. • Filum Terminale: terminal thread of fibrous tissue extends from the conus medullaris to 2nd sacral vertebra.

32. Spinal Cord • Cauda Equina: (horses tail) terminal portion that forms the nerve fibers that are the lumbar, sacral, & coccygeal spinal nerves.

34. Cerebrospinal Fluid • Colorless fluid produced by the choroid plexuses within the ventricles of the brain. • Circulates through the ventricles, central canal, & subarachnoid space. Is removed by the arachnoid villi. • Adult 120 – 150mL. • Cushions the brain & spinal cord from shocks that could cause injury.

35. PNS: Peripheral Nervous System Central Nervous System • Network of nerves branching throughout the body from the brain & spinal cord. • 12 pairs of cranial nerves attach to the brain. • 31 pairs of spinal nerves connected to the spinal cord. Peripheral Nervous System

36. Cranial Nerves • Attached to the brain. Arranged symmetrically, 12 to each side of the brain. • Function: Provide sensory input, motor control, or a combination of these functions.

41. Spinal Nerves • 31 pairs along the length of the spinal cord & from the vertebral canal. • Each nerve is divided into 2 roots. • Dorsal/Sensory roots: composed of afferent fibers carrying impulses to the cord • Ventral Roots: contain motor fibers carrying efferent impulses to muscles & organs

42. Spinal Nerves • Cervical: 8 pairs • Thoracic: 12 pairs • Lumbar: 5 pairs • Sacral: 5 pairs • Coccygeal: 1 pair

43. ANS: Autonomic Nervous System • A part of the PNS. • Controls involuntary bodily functions: • Sweating • Secretion of glands • Heart • Arterial blood pressure • Smooth muscle tissue

44. ANS: Autonomic Nervous System • Composed of efferent fibers from certain cranial & spinal nerves that are divided into the: • Sympathetic Division • Parasympathetic Division • The 2 divisions counteract each other to keep the body in a state of homeostasis.

45. Sympathetic Division • Since sympathetic fibers synapse with cell bodies in the sympathetic ganglia, they produce widespread innervation when activated. • This is called the fight-or-flight response. • This division also causes the release of epinephrine (adrenaline), causing an adrenaline rush.

46. Fight-or-Flight Response • During this a person experiences:

47. Parasympathetic Division • Works to conserve energy and innervate the digestive system. • When activated it: • Stimulates salivary & digestive gland • Decreases metabolic rate • Slows heart rate • Reduces blood pressure • Allows material through intestines & absorption of nutrients by blood

50. Alzheimer’s Disease (AD) • Loss of memory & other cognitive functions. • Involves the parts of the brain that control thought, memory,& language. • Begins after age 60, and risk goes up with age. • Not a normal part of aging.