1. The Nervous System
Unit K

2. Central Nervous System
Communication and coordination system of the body
Seat of intellect and reasoning.
Consists of the brain, spinal cord, and nerves.

3. Neuron -Transmits a message from one cell to another
-Nerve cell
-Transmits a message from one cell to another
-Has a nucleus, cytoplasm, and cell membrane
Dendrites
Nerve cell processes that
carry impulse to cell body…may be one or more

4. Myelin Sheath Axon Myelin is a fatty substance that protects axon
speeds transmission along axon - Called neurilemma
Axon
-Carries impulses away from the cell body
-Only one on a neuron

5. NERVE IMPULSE A STIMULUS creates an IMPULSE.
Impulse to dendrite to axon to neurotransmitter to synapse.

6. SYNAPSE
A space between neurons, messages go from one cell to another.

7. SENSORY NEURONS (AFFERENT)
Emerge from the skin or sense organs.
Carry impulses to spinal cord and brain.

8. MOTOR NEURONS (EFFERENT)
Carry messages from brain and spinal cord to muscles and glands.

9. ASSOCIATIVE NEURONS (INTERNEURONS)
Carry impulses from sensory neurons to motor neurons.

10. NEUROGLIA
Cells that insulate, support and protect the neurons, nerve glue.

11. CENTRAL NERVOUS SYSTEM
Divisions of the Nervous System
CENTRAL NERVOUS SYSTEM
The brain and spinal cord

12. Autonomic Nervous System
Peripheral nerves and ganglia
Supplies heart muscle, smoother muscle and secretory glands
Involuntary i.e. automatic responses to injury like shock and increased heart rate

13. Peripheral Nervous System (PNS)
Cranial nerves and spinal nerves are part of the PNS

14. The Brain 3lb mass of soft nervous tissue 100 billion neurons
Protected by skull, 3 membranes called meninges, and cerebrospinal fluid (shock absorber)
Cerebrum

15. Adequate blood supply is needed, brain tissue will die in 4-8 mins without O2
Divided into 4 major parts: cerebrum, diencephalon (near midbrain), cerebellum, brain stem

17. Coverings of the Brain (MENINGES)
Meninges surrounds the brain and spinal cord

18. DURA MATER- outer brain covering, lines inside of skull, tough, fluid-containing - dense fibrous connective tissue
Layers = dura mater, subdural, arachnoid, subarachnoid, pia mater

19. Coverings cont’d Subdural space
is between the dura and arachnoid space
Next layer is the Arachnoid layer
- middle layer – resembles fine cob web

20. SUBARACHNOID SPACE- between arachnoid and pia mater, filled with CEREBROSPINAL FLUID which acts as a liquid shock absorber and as a source of nutrients for the brain

21. Coverings cont’d
PIA MATER
innermost layer of the meninges
covers the brain’s surface, comprised of blood vessels held together by connective tissue

23. Ventricles of the Brain
Brain contains four cavities filled with cerebrospinal fluid called CEREBRAL VENTRICLES.

24. Ventricles of the Brain (cont.)
CHOROID PLEXUS- network of blood vessels lining the ventricles which helps in the formation of cerebrospinal fluid.
CEREBROSPINAL FLUID
Forms inside ventricles of the brain.
Serves as a liquid shock absorber

25. BLOOD-BRAIN BARRIER- choroid plexus capillaries prevent substances (like drugs) from penetrating brain tissue – this makes infections, like meningitis, difficult to cure.
LUMBAR PUNCTURE- removal of CSF from spinal canal, needle puncture between 3rd and 4th lumbar vertebrae.

27. CEREBRUM Largest part of the brain
Divided into R and L hemispheres by deep groove
CONVULTIONS- elevated folds on the surface of the cerebrum, they increase the surface area of the brain

28. SULCI - fissure or grooves separating cerebral convolutions
Divided into four lobes – FRONTAL (voluntary muscle movement), PARIETAL, OCCIPITAL and TEMPORAL

29. CEREBRAL FUNCTION
Conscious thought, judgment, memory, reasoning, and will power.
- responsible for maintaining consciousness,
decision making, recalling information
and normal speech
These people were not
using their cerebrum.

30. Located between cerebrum and midbrain
DIENCEPHALON
Located between cerebrum and midbrain
Composed of THALAMUS and HYPOTHALAMUS

31. Vital functions of the hypothalamus:
1. Autonomic nervous control
2. Temperature control
3. Appetite control
4. Emotional state
5. Sleep control

32. CEREBELLUM
2nd largest part of brain
Composed of two hemispheres
below the cerebrum
Controls all body functions related to skeletal muscles, including:
Balance, walking
Muscle tone
Coordination of muscle movements

33. Controls all body functions related to skeletal muscles, including:
Balance, walking
Muscle tone
Coordination of muscle movements

34. BRAIN STEM Made up of PONS, MEDULLA and MIDBRAIN
Pons – in front of cerebellum, between midbrain and medulla – contains center that controls respiration
Midbrain – controls vision and hearing
Medulla oblongata – bulb-shaped structure between pons and spinal cord, inside the cranium above foramen magnum (opening in vertebral column)
- Responsible for:
1. Heart rate
2. Blood pressure
Click for picture…

35. SPINAL CORD
Begins at foramen magnum and continues down to 2nd lumbar vertebrae
White and soft, in spinal canal
Surrounded by cerebrospinal fluid
FUNCTIONS AS:
Reflex center
Conduction pathway to and from the brain
Injury to spinal cord = difficulty with movement (paraplegia – paralysis of legs) and problems breathing

36. Peripheral Nervous System
All of the nerves outside the central nervous system
NERVES
Contains sensory and motor nerves (afferent and efferent)

37. Cranial Nerves 12 pairs Begin in the brain
Designated by number and name

38. Mnemonic for the 12 cranial nerves
Old
Olympus’
Towering
Top A
Finn
And
German
Vault
Hop
Mnemonic for the
12 cranial nerves

39. SPINAL NERVES
Originate at spinal cord and go through openings in vertebrae
31 pairs of spinal nerves
All are mixed (afferent and motor) nerves
Named in relation to their location on the spinal cord

40. AUTONOMIC NERVOUS SYSTEM
Regulates activities of visceral organs (i.e. beating of heart)
Not subject to conscious control
SYMPATHETIC NERVOUS SYSTEM- the “fight or flight” system- when the body perceives danger, SNS sends message to adrenal medulla (above kidney) to secrete adrenaline - heartbeat increases, resp rate increases, etc

41. Parasympathetic Nervous system counters SNS – decreases heart rate, decreases respiratory rate, etc
REFLEX
Unconscious and involuntary
In a simple reflex, only a sensory nerve and motor nerve involved – example “knee-jerk” reflex

42. Disorders of the Nervous System
MENINGITIS
Inflammation of the lining of the brain and spinal cord
May be bacterial or viral
Symptoms- headache, fever and stiff neck, nausea and vomiting
In severe form, may lead to paralysis, coma and death
If bacterial, may be treated with antibiotics
Dx by removing csf with a needle = lumbar puncture

43. EPILEPSY
Seizure disorder of the brain, characterized by recurring and excessive discharge from neurons
Seizures believed to be result of spontaneous, uncontrolled electrical activity of neurons
Cause – Uncertain
Victim may have hallucinations and seizures
Grand mal – severe, convulsive seizure
Petit mal - milder

44. CEREBRAL PALSY
Disturbance in voluntary muscular action due to brain damage.
May be due to birth injury or abnormal brain development
Spastic Quadriplegia- spastic paralysis in all four limbs.
Sx- head rolling, grimacing,
difficult speech and swallowing
No impairments of intellect.

45. POLIOMYELITIS DEMENTIA
Viral disease of nerve pathways of spinal cord- causing progressive muscle weakness leading to paralysis
Almost eradicated in USA (vaccine)
DEMENTIA
Loss of 2 areas of complex behavior, such as languages, memory, visual and spatial abilities, or judgment
Interferes with person’s daily life.

46. HYDROCEPHALUS
Increased volume of cerebrospinal fluid within ventricles of the brain.
Usually, blockage in 3rd and 4th ventricle
Enlargement of the head, usually noticed at birth.
Bypass or shunt performed to relieve pressure.

47. Abnormal fibers build up creating tangles
ALZHEIMER’S DISEASE
Progressive disease that begins with problems remembering – characterized by early senility, confusion, and loss of recognition of persons
Nerve endings in cortex of brain degenerate and block signals that pass between nerve cells
Abnormal fibers build up creating tangles

48. Cause – Unknown
1st stage (2-4 yrs) involves confusion, short-term memory loss, anxiety, poor judgment
2nd stage (2-10 yrs) increase in memory loss, logic problems, and loss of social skills
3rd stage (1-3 yrs) inability to recognize oneself, weight loss, seizures, mood swings and aphasia

49. PARKINSON’S DISEASE
Symps - tremors, shuffling gait, pill-rolling, and muscular rigidity.
Decrease in neurotransmitter dopamine
RX- L-dopa and other drugs to treat symptoms.

50. Chronic inflammatory disease of CNS - autoimmune
MULTIPLE SCLEROSIS (MS)
Chronic inflammatory disease of CNS - autoimmune
Immune cells attack myelin sheath of axon-myelin sheath destroyed, leaving scar tissue on nerve cells…transmission of nerve impulses blocked.

51. Cause- UNKNOWN
Sx- weakness of extremities, numbness, double vision, nystagmus, speech problems, loss of coordination, possible paralysis.
Typically strikes young adults age 20-40, mostly women
Rx- Avonex- slows progression

52. Cerebral Vascular Accident
Stroke or CVA
Interruption of blood and O2 to the brain – blockage of blood to the brain
Tissue death
Third leading cause of death in USA
PARALYSIS- loss of power of motion or sensation
HEMIPLEGIA- paralysis on one side of the body
Symptoms →

53. Risk Factors
Smoking
Hypertension
Heart disease
Family history
Causes of CVA
90% caused by blood clots
Clots lodge in carotid arteries, blocking the flow of blood to the brain
10% caused by ruptured blood vessels in the brain

54. SYMPTOMS Hemiplegia on the opposite side of the body
Sudden, severe headache
Dizziness
Sudden loss of vision in one eye
Aphasia
Dysphasia
Coma
Possible death