A & P Chapter 11 : Nervous System

Front 1

Functions of the Nervous System

Back 1

1. Sensory Input

2. Integration

3. Motor Output

Front 2

Sensory Input

Back 2

Information gathered by sensory receptors about internal and external changes

Front 3

Integration

Back 3

Interpretation of sensory input

Front 4

Motor Output

Back 4

Activation of effector organs (muscle and glands) produces a response

Front 5

Central nervous system
(CNS)

Back 5

- Brain and spinal cord

- Integration and command center

Front 6

Peripheral nervous system
(PNS)

Back 6

Paired spinal and cranial nerves carry messages to and from the CNS

Front 7

Sensory (afferent) division

Back 7

- Somatic afferent fibers----convey impulses from skin, skeletal muscles, and joints.
- Visceral afferent fibers----convey impulses from visceral organs
- Transmits impulses from sensory receptors towards CNS

Front 8

Motor (efferent) division

Back 8

Transmits impulses from CNS to effector organs

Front 9

Somatic nervous system

Back 9

- Part of motor division of PNS

- Conscious control of skeletal muscle

- Voluntary

Front 10

Autonomic nervous system

Back 10

- Part of motor division of PNS
- Visceral motor nerve fibers
- Regulates smooth muscle, cardiac muscle, and glands
- Sympathetic and Parasympathetic
- Involuntary

Front 11

Neurons

Back 11

- Excitable cells that transmit electrical signals
- Respond to adequate stimulus by generating an action potential (nerve impulse)
- Impulse is always the same regardless of stimulus

Front 12

Neuroglia (glia cells) ---supporting cells

Back 12

- Astrocytes (CNS)
- Microglia (CNS)
- Ependymal cells (CNS)
- Oligodendrocytes (CNS)
- Satellite cells (PNS)
- Schwann cells (PNS)

Front 13

Astrocytes

Back 13

- Most abundant, versatile, and highly branched glial cells.
- Cling to neurons, synaptic endings, and capillaries
- Support and brace neurons
- Helps determine capillary permeability
- Guides migration of young neurons
- Controls chemical environment
- Participates in information processing in the brain

Front 14

Microglia

Back 14

- Small ovoid cells with thorny processes

- Migrates toward injured neurons

- Phagocytize microorganisms and neuronal debris

Front 15

Ependymal Cell

Back 15

- Range in shape from squamous to columnar
- May be ciliated
- Line the central cavities of the brain and spinal column
- Separates the CNS interstitial fluid from the cerebrospinal fluid in the cavities

Front 16

Oligodendrocytes

Back 16

- Branched cells
- Processes wraps CNS nerve fibers, forming insulation myelin sheaths
- Very important
- Counterpart is the Schwann cell

Front 17

Satellite Cell

Back 17

Surrounds neuron cell bodies in the PNS

Front 18

Schwann Cell

Back 18

- Surrounds peripheral nerve fibers and forms myelin sheaths
- Vital to regeneration of damaged peripheral nerve fibers

Front 19

Clusters of cell bodies are called...

Back 19

- Nuclei in the CNS

- Ganglia in the PNS

Front 20

Dendrites

Back 20

- Short, tapering, and diffusely branched
- Receptive (input) region of a neuron
- Convey electrical signals towards the cell body as a graded potential
- Info comes in

Front 21

Axons: Function

Back 21

- Conducting region of a neuron

- Generates and transmits nerve impulses (action potential) away from the cell body

Front 22

Myelin

Back 22

- Segmented protein-lipoid sheaths around most long or large-diameter axons
- It protects and electrically insulates the axon
- It increases speed of nerve impulse transmission

Front 23

White matter

Back 23

Dense collection of myelinated fibers

Front 24

Gray matter

Back 24

Mostly neuron cell bodies and unmyelinated fibers

Front 25

Multipolar neuron

Back 25

- 1 axon and several dendrites
- Most abundant
- Motor neurons and interneurons

Front 26

Bipolar neuron

Back 26

- 1 axon and 1 dendrite
- Rare e.g., retinal neurons (eye)

Front 27

Unipolar neuron

Back 27

- Single, short process that has two branches
- Peripheral process--more distal branch, often associated with a sensory receptor
- Central process--branch entering the CNS

Front 28

Graded potential

Back 28

Incoming short-distance signals

Front 29

Action potential

Back 29

Long-distance signals of axons
- ex. muscles

Front 30

Depolarization

Back 30

- A reduction in membrane potential (towards zero)
- Inside of membrane becomes less negative than the resting potential
- Increases the probability of producing a nerve impulse
- No action potential
- Opens voltage-gated Na+ channels

Front 31

Repolarization

Back 31

- Na+ channel slow inactivation gates close
- Membrane permeability to Na+ declines to resting levels
- Slow voltage-sensitive K+ gates open
- K+ exits the cell and internal negativity is restored

Front 32

Hyperpolarization

Back 32

- An increase in membrane potential (away from zero)
- Inside of membrane becomes more negative than the resting potential
- Reduces the probability of producing a nerve impulse
- Opposite of depolarization
- Some K+ channels remain open, allowing excessive K+ efflux

Front 33

Refractory

Back 33

- Time from the opening of the Na+ channels until the resetting of the channels
- Ensures that each AP is an all-or-nothing event
- Enforces one-way transmission of nerve impulses

Front 34

Graded potential

Back 34

- Short-lived, localized changes in membrane
- Depolarization or Hyperpolarization
- Graded potential spreads as local currents change the membrane potential of adjacent regions
- Occur when a stimulus causes gated ion channels to open

Front 35

More on Graded potential

Back 35

- Magnitude varies directly with stimulus strength
- Decrease in magnitude with distance as ions flow and diffuse through leakage channels
- Short-distance signals

Front 36

Action potential

Back 36

- Brief reversal of membrane potential with a total amplitude of ~100 mV\
- Occurs in muscle cells and axons of neurons
- Does not decrease in magnitude over distance
- Principle means of long-distance neural communication
- Resting state, only leakage channels for Na+ and K+ are open. All gated channels are closed.

Front 37

The Synapse

Back 37

A junction that mediates information transfer from one neuron
- To another neuron, or
-To an effector cell

Front 38

Presynaptic neuron

Back 38

conducts impulses towards the synapse

Front 39

Postsynaptic neuron

Back 39

Transmits impulses away from the synapse

Front 40

Postsynaptic potential

Back 40

- Graded potential
- Strength determined by:
- Amount of neurotransmitter released
- Time the neurotransmitter is in the area
- Types of postsynaptic potentials
1. EPSP-- excitatory postsynaptic potentials
2. IPSP -- Inhibitory postsynaptic potentials