Chapter 7: The Nervous System

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1

Sensory Input

Gathering information

  • to monitor changes occurring inside & outside the body
  • changes = stimuli
2

Integration

To process and interpret sensory input and decide whether action is needed

3

Motor Output

  • A response to integrated stimuli
  • The response activates muscles or glands
4

Central Nervous System

(CNS)

Consists of organs that interpret incoming sensory info and issue instructions based on past experiences and current conditions

  • Brain
  • Spinal Cord
5

Peripheral Nervous System

(PNS)

Nerves extending from the brain and spinal cord.

  • Spinal nerves
  • Cranial nerves
  • Functions: Serve as a communication lines among sensory organs (brain & spinal cord) and glands or muscles.
6

Spinal Nerves

Carry impulses to and from the spinal cord

7

Cranial Nerves

Carry impulses to and from the brain

8

Sensory (afferent) Division

Nerve fiber that carry info to the central nervous system

9

Somatic Sensory Fibers

Carry info from the skin, skeletal muscles, and joints

10

Visceral Sensory Fibers

Carry info from visceral organs

11

Motor (efferent) Division

Nerve fibers that carry impulses away from the central nervous system

  • 2 Subdivisions
  • Somatic Nervous System
  • Autonomic Nervous System
12

Somatic Nervous System

  • Voluntary
  • Consciously controls skeletal muscles
13

Autonomic Nervous System

  • Involuntary
  • Automatically controls smooth and cardiac muscles and glands
  • Further divided into the sympathetic and parasympathetic nervous systems
14

Neuroglia

Nerve glue

Functions:

  • Support
  • Insulate
  • Protect Neurons
15

Astrocytes

(CNS Glial Cell)

Abundant, star-shaped cells

Functions:

  • Brace Neurons
  • From barrier between capillaries and neurons
  • Control the chemical environment of the brain
16

Microglia

(CNS Glial Cell)

Spider-like Phagocytes

Functions:

  • Dispose of debris
17

Ependymal Cells

(CNS Glial Cell)

Lines cavities of the brain and spinal cord. Cilia assist with circulation of cerebrospinal fluid.

18

Oligodendrocytes

(CNS Glial Cell)

Wrap around nerve fibers in the central nervous system

  • Produce myelin sheaths around axons
19

Satellite Cells

(PNS Glial Cell)

Protect neuron cell bodies

20

Schwann Cells

(PNS Glial Cell)

Form myelin sheath in the peripheral nervous system

  • Form around axons in a jelly-roll like fashion
21

Neurons

nerve cells, specialized to transmit messages

Major regions

  • Cell body
  • Processes
22

Cell Body

Nucleus and metabolic center of the cell

23

Processes

Fibers that extend from the cell body

24

Dendrites

Conduct impulses toward the cell body

  • Neurons may have hundreds
25

Axons

Conduct impulses away from the cell body

  • Neurons have only one, arising from the cell body at the hillock
  • End in terminals
26

Axon Terminals

Contain vesicles with neurotransmitters, and separated from each other by gaps

27

Synaptic Cleft

Gap between adjacent neurons

28

Synapse

Junction between nerves

29

Myelin Sheaths

Whitish, fatty material covering axons

30

Nodes of Ranvier

Gaps in myelin sheaths along the axon

31

Gray Matter

Cell bodies and unmyelinated fibers and cell bodies

In the brain: outer layer in the cerebral cortex; composed mostly of cell bodies.

32

Nuclei

Clusters of cell bodies within the white matter of the central nervous system

33

Ganglia

Collections of cell bodies outside the central nervous system

34

Tracts

Bundles of nerve fibers in the CNS

35

Nerves

Bundles of nerve fiber in the PNS

36

White Matter

Collections of myelinated fibers (tracts), fiber tracts deep to the gray matter

37

Sensory (afferent) Neurons

Carry impulses from the sensory receptors to the CNS

38

Cutaneous Sense Organs

Simpler types of sensory receptors in the skin

39

Proprioceptors

Detect stretch or tension

40

Motor (efferent) Neurons

Carry impulses from the central nervous system to viscera, muscles, or glands

41

Interneurons (association neurons)

Found in neural pathways in the CNS, connect sensory and motor neurons

42

Multipolar Neurons

Many extensions from the cell body

  • All motor and interneurons are multipolar
  • Most common structure
43

Bipolar Neurons

One axon and one dendrite

  • Located in special sense organs (nose and eye)
  • Rare in adults
44

Unipolar Neurons

Have a short single process leaving the cell body

  • Sensory neurons found in PNS ganglia
  • Conduct impulses both toward and away from the cell body
45

Polarized

There are fewer positive ions sitting on the inner face of the neuron's plasma membrane than on its outer face

46

Irritability

Ability to respond to a stimulus and convert it to a nerve pulse

47

Conductivity

Ability to transmit the impulse to other neurons, muscles, or glands

48

Resting Neurons

The plasma membrane at rest is polarized, as long as the inside is more negative then the outside the cell stays at rest.

49

Action Potential

Activates the neuron to initiate and transmit a long-distance signal

50

Reflexes

Rapid, predictable, and involuntary responses to a stimulus

  • occur over neural pathways called reflex arcs
51

Somatic Reflexes

Reflexes that stimulate the skeletal muscles.

  • Ex: pulling you hand away from a hot object
52

Autonomic

Regulate the activity of smooth muscles, the heart, and glands

  • Ex: Regulation of smooth muscles, heart and blood pressure, glands, digestive system.
53

Sensory Receptor

Reacts to a stimulus

54

Sensory Neuron

Carries messages to the integration center

55

Integration Center (CNS)

Process info and directs motor output

56

Motor Neuron

Carries message to an effector

57

Effector Organ

Is the muscles or gland to be stimulated

58

2-Neuron Reflex Arcs

Simplest type

  • Ex: Patellar (knee-jerk) reflexs
59

3-Neuron Reflex Arcs

Consists of 5 elements: receptors, sensory neuron, interneuron, motor neuron, and effector

  • Ex: flexor (withdrawal) reflex
60

Lobes

Divided by fissures (deep grooves)

61

Primary Motor Area

Sends impulses to skeletal muscles, located in frontal lobe