Lecture 24- The Peripheral Nervous Sytem

Question 1

What is the PNS?

Answer 1

Peripheral nervous system
All neural structures outside the brain and spinal cord

Sensory receptors
Peripheral nerves
Efferent motor endings

Question 2

Sensory receptors

Answer 2

Specialized receptors that respond to changes in environment called stimuli

Question 3

Non encapsulated dendritic endings

Answer 3

Free nerve endings that detect temp., pain, itch, light touch or are located at base of hair follicles.

Question 4

Encapsulated dendritic endings

Answer 4

Consist of dendrite enclosed in a connective tissue capsule and detect discriminatory touch,initial, continuous and deep pressure and stretch of muscle , tendons and joint. Capsules

Question 5

What can graded receptor potentials trigger?

Answer 5

Action potentials that travel along the axon to the CNS

Question 6

Mechanoreceptors

Answer 6

Stimulated by mechanical force, such as touch,pressure, vibration and stretch

Question 7

Thermoreceptors

Answer 7

Detect changes in temperature

Question 8

Photoreceptors

Answer 8

Detect light

Generally in the eyes

Question 9

Chemoreceptors

Answer 9

Stimulated by chemicals such as odours,tastes or chemical components of body fluids

Question 10

Nolcireceptors

Answer 10

Respond to painful stimuli

Question 11

Where exteroceptors located?

Answer 11

Near the body surface

And detect stimuli from outside body- touch, pressure, pain

Question 12

Where are interceptors located?

Answer 12

Associated with internal organs and vessels

Monitor chemical changes, stretch or temperature

Question 13

Where are proprioreceptors located?

Answer 13

Within skeletal muscles, joints and associated connective tissues

Relay information about body movements

Question 14

Sensation

Answer 14

Awareness of changes in internal and external environment

Question 15

Perception

Answer 15

The conscious interpretation of sensation stimuli

Question 16

First order sensory neurons

Answer 16

Carry impulses from receptors

Question 17

Second order neurons

Answer 17

Transmit to the cerebellum

Question 18

Third order neurons

Answer 18

Carry impulses to postfrontal gyrus

Question 19

Perception of Pain

Answer 19

Protects body from damage

Stimulate by extremes of pressure and temperature as well as chemicals releases from damaged tissues

Question 20

Pain threshold

Answer 20

Stimulus intensity at which we begin to perceive pain

Same for most people

Question 21

Pain tolerance

Answer 21

Genetically determined trait with learned aspects that varies from person to person

Perceived pain can be affected by environment

Question 22

Visceral pain

Answer 22

Results from stimulation of receptors within internL organs from stimuli such as extreme stretch, ischemia, chemical irritation and muscle spasms

Question 23

What does visceral pain travel along?

Answer 23

The same fibre tracts as somatic pain impulses, giving rise to reffered pain

Question 24

Reffered pain

Answer 24

Pain that feels as though it is located in an area different from the affected body region

Question 25

Mixed nerves

Answer 25

Contain both sensory and motor fibres

Most nerves are mixed nerves

Question 26

Sensory/ afferent nerves

Answer 26

Carry impulses only toward CNS

Question 27

Motor/ efferent nerves

Answer 27

Carry impulses away from CNS

Question 28

Endoneurium

Answer 28

Thin layer of loose connective tissue Around each axon

Around axon

Question 29

Perineurium

Answer 29

Connective tissue wrapping that bundles groups of fibres into fascicles

Around fascicle

Question 30

Epimeurium

Answer 30

Bundles all fascicles into a nerve

Around nerve

Question 31

Nerve plexus

Answer 31

Interlacing networks formed by all vertebral brances EXCEPT T2 - T12

Question 32

What is in each nerve plexus? And what does it do?

Answer 32

Fibres crisscross so each branch contain fibres from multiple spinal nerves

Each limb muscle is innervated by more than one spinal nerve and damage to one does NOT cause paralysis

Question 33

Dermatomes

Answer 33

Areas of skin innervated by cutaneous branches of single spinal nerve

Most overlap so destruction of single spinal nerve will NOT cause complete numbness

Question 34

What forms neuromuscular junctions?

Answer 34

Terminals of somatic motor fibres that innervate voluntary muscles

Release acetylcholine

Question 35

What forms synapses en passant?

Answer 35

Junctions between autonomic motor endings and visceral effectors

Release acetylcholine or epinephrine

Question 36

Varicosities… what are they? What do they do?

Answer 36

Bulge of neurotransmitter

Autonomic nerve fibres that innervate most smooth muscle

These contractions tend to be slower than skeletal

Vesicles release neurotransmitter into synaptic cleft

Question 37

Ganglia

Answer 37

Collection of neuron cell bodies associated with nerves in PNS

Question 38

Do damaged CNS nerve fibres regenerate?

Answer 38

Almost ever.

Question 39

Do PNS nerve fibres regenerate?

Answer 39

If cell body remains intact, yes

Question 40

What cell help regeneration of PNS axons?

Answer 40

Schwann cells

Question 41

What cells in CNS do not supporter regrowth of axons?

Answer 41

Oligodendrocytes

Question 42

Chromatolysis

Answer 42

Breakdown of nissl bodies after nerve damage

Question 43

Wallerian degeneration

Answer 43

Breakdown of the distal portion. Of axon and myelin sheath

Question 44

How fast do nerves with regeneration tube grow?

Answer 44

A rate of 1mm per day