1. CHAPTER 7
NERVOUS SYSTEM

2. ORGANS AND DIVISIONS OF THE NERVOUS SYSTEM
Central Nervous System (CNS):
Organs: Brain and spinal cord
Peripheral Nervous System (PNS):
Organs: All Nerves
Autonomic Nervous System (ANS):
Organs: Motor neurons

4. CELLS OF THE NERVOUS SYSTEM
2 Types of cells found in the nervous system:
1. NEURONS: nerve cells
Parts: cell body, dendrites and axon
3 types: sensory, motor and interneurons
2. GLIA: specialized connective tissue
Glia means glue. Holds the functioning neurons together to protect them.

5. NEURONS Also called efferent neurons.
Motor neurons transmit impulses away from the spinal cord and brain to muscle and glandular epithelial tissue.
Also called efferent neurons.
Interneurons conduct impulses form sensory neurons to motor neurons.
Also called central or connecting neurons.
Sensory neurons transmit impulses to the spinal cord and brain from all parts of the body
Also called afferent neurons.

6. AXON: is surrounded by segmented wrapping called myelin.
STRUCTURE OF NEURON
AXON: is surrounded by segmented wrapping called myelin.
- Myelin is a white, fatty substance by Schwann cells that wrap around some axons outside the CNS.
- These fibers are called myelinated fibers

8. GLIA Glia or neuroglia: They are special types of supporting cells
- Function: is to hold neurons together and protect them. - Vary in size and shape:
* Large cells look like stars: astrocytes
* Smaller cells are Microglia
* Oligodendrocytes: helps hold fibers together, produce the fatty myelin sheath that envelops nerve fibers in the brain and spinal cord

11. NERVES
Nerve is a group of peripheral nerve fibers (axons) bundled together like the strands of a cable.
Myelin is found on nerves and is white.
Nerves are called white matter of the PNS and also the CNS.
Unmyelinated axons and dendrites are called gray matter. (because of gray color)

12. WHITE AND GRAY MATTER

13. REFLEX ARC
Nerve impulses are conducted from receptors to effectors over neuron pathways known as Reflex arcs.
This results in a reflex. (a contracted muscle or secretion from a gland)
2 types of reflex arcs:
- two-neuron arcs: spinal cord and motor neuron
- three-neuron arcs: sensory neurons, interneurons and motor neurons

14. RECEPTORS Impulse conduction normally starts in the receptors.
Found at the beginning of the dendrites of sensory neurons
Located in the tendons, skin or mucous membranes.

16. MS (MULTIPLE Sclerosis) DAMAGE TO MYELIN
Hard lesions replace the destroyed Myelin
As the myelin is lost, nerve conduction is impaired
Causing weakness, loss in coordination, visual impairment, speech disturbances
No known cure, occurs most in women ages

17. Synapse
A microscopic space from the axon ending of one neuron to the dendrite of another neuron.
The nerve impulse stops, chemicals are sent across the gap, the impulse continues alone the dendrites.

18. Neurotransmitters Chemicals by which neurons communicate.
Specific neurotransmitters are released in specific pathways.
Some help us sleep, make us happy, make us more energetic, some inhibit pain

19. CNS (CENTRAL NERVOUS SYSTEM) Spinal Cord and Brain
4 Divisions of the brain:
Brainstem
Medulla Oblongata
Pons
Midbrain
Cerebellum
Diencephalon
Hypothalamus
Thalamus
Cerebrum

20.                       .

21. BRAINSTEM - extension of the spinal cord
* Medulla Oblongata: largest part of the brainstem.
- extension of the spinal cord
- Location: lies below the pons and the midbrain
- Functions: reflex center (control heartbeat, respiration and blood vessel diameter)

24. DIENCEPHALON Hypothalamus:
- Structure: consists mainly of the posterior pituitary gland, pituitary stalk and gray matter.
- Function: Acts as the major center for
controlling the ANS. (function of internal
organs)
- Controls hormone secretion
- Centers for controlling appetite, wakefullness and pleasure

26. DIENCEPHALON THALAMUS:
- Structure: dumbbell shaped mass of gray matter in each cerebral hemisphere
- Function: relays sensory impulses to cerebral cortex
- Produces emotions of pleasantness and unpleasantness associated with sensation

28. CEREBELLUM Second largest part of the brain
Structure: Lies under the occipital lobe of the cerebrum
- composed of gray matter in outer layer and white matter in the inner layer
Function: helps control muscle contractions to produce coordinated movements.
Also, maintain balance, move smoothly and sustain normal posture

30. CEREBRUM Largest part of the brain
Structure: Structures: Series of ridges and grooves
-Ridges are called convolutions or Gyri
-Grooves are called Sulci (deepest sulci are called fissures)
-Divided into two halves- Hemispheres
-Hemispheres connected by the Corpus callosum

33. CEREBRUM HEMISPHERES: Divided into lobes
Lobes are named after bones that lie over them.

34. CEREBRUM Function: mental process of all types
Sensations
Consciousness
Thinking
Memory
Willed Movements
Page 177, second paragraph

35. Cerebrum Specific areas have specific functions
Temporal lobe’s auditory areas interpret incoming nervous signals as specific sounds
Visual area of the occipital lobe helps you understand and identify images
If a specific part of the brain is damaged, for example the Primary Taste Area, you would not be able to taste things.

36. __________CEREBRUM

37. SPINAL CORD Structure: Outer part composed of white matter
- Interior part composed of gray matter
Function: center of all spinal cord reflexes
- sensory tracts conduct impulses to the brain.
- motor tracts conducts impulses from the brain

38. Cutting the Cord
Completely severing the spinal cord produces a loss of sensation for all areas below the cut, called anesthesia.
It also produces a loss of the ability to make voluntary movements, called paralysis.

40. Peripheral Nervous System (PNS) Cranial and Spinal Nerves
Connect the Brain and Spinal Cord to Peripheral structures like skin and muscles.
Cranial Nerves:
- 12 pairs of cranial nerves
- Functions vary
- see diagram on page 187 and chart on 188 for function and location (you will need to know number, name, function)

43. SPINAL NERVES
Structure: contain dendrites of sensory neurons and axons of motor neurons
Function: conduct impulses necessary for sensations and voluntary movements
Dermatones: skin areas that are supplied by a single spinal nerve

45. Autonomic Nervous System (ANS)
Structure: Consists of motor neurons that conduct impulses from spinal cord or brainstem to:
1. Cardiac Muscle tissue
2. Smooth muscle tissue
3. Glandular epithelial tissue
Function: regulate involuntary functions
- heartbeat, contractions of the stomach and intestines and secretions by glands

46. 2 Divisions of ANS 1. Sympathetic nervous system:
-Structure: dendrites and cell bodies located in gray matter of the thoracic and upper lumbar segments of the spinal cord
-Function: serves as the emergency or stress system during strenuous exercise and strong emotions (hate, anger, fear or anxiety)
- controls the “ fight or flight” response

47. 2 Divisions of ANS 2. Parasympathetic Nervous System:
Structure: Neurons are located in gray matter of the brainstem and sacral segments of the spinal cord.
Function: dominates control of many visceral effectors under normal everyday conditions (bladder, intestines, lung)

49. Autonomic Neurotransmitters
Each division of the ANS signals its effectors with a different neurotransmitter.
This is how an organ can tell which division is stimulating it.
Ex. The heart responds to acetylcholine from the parasympathetic division by slowing down. If norepinephrine, from the sympathetic division, is present, the heart speeds up.

50. ANS as a Whole
Regulates the body’s autonomic functions in ways that maintain HOMEOSTASIS
Many visceral effectors are effected by both sympathetic and parasympathetic divisions.