Lec 8- Nervous system org and reflexes

Question 1

Ascending Spinal Tract

Answer 1

Transmit to the brain signals derived from afferent input

Question 2

Descending Spinal Tract

Answer 2

Relay messages from the brain to efferent neurons.

Question 3

Pyramidal/corticospinal

Answer 3

Fibers originating from neuronal cell bodies known as pyramidal cells within the primary motor cortex descend directly without synaptic interruption to terminate on motor neurons in the spinal cord.

Question 4

Reticulospinal/extrapyramidal

Answer 4

Include synapses that involve regions of the brain.

Question 5

Ganglia

Answer 5

The nerve cells in the outermost layer of the retina whose axons form the optic nerve.

Question 6

Dorsal root

Answer 6

Sensory fibers.

Afferent fibers carrying incoming signals from peripheral receptors enter the spinal cord through the dorsal root.

Question 7

Ventral root

Answer 7

Motor fibers.

The cell bodies for the efferent neurons originate in the gray matter and send axons out through the ventral root.

Question 8

Nerve

Answer 8

A bundle of peripheral neuronal axons, some afferent and some efferent, enclosed by a connective tissue covering and following the same pathway.

Question 9

Spinal nerves

Answer 9

31 pairs (8 cervical, 12 thoracic, etc...) 
Bring info to the CNS.

Question 10

Cranial Nerve X = Vagus

Answer 10

Most branches of the vagus nerve supply organs in the thoracic and abdominal cavities.
Major nerve of the PNS.

Question 11

Peripheral nervous system (PNS)

Answer 11

Nerve fibers that carry information between the CNS and the body.

Question 12

Afferent

Answer 12

Sensory; carries input to CNS.

Question 13

Efferent

Answer 13

Motor; carries info to an effector organ.

Question 14

Transduce

Answer 14

to convert (something, such as energy or a message) into another form essentially sense organs transduce physical energy into a nervous signal.

Question 15

Modality

Answer 15

The energy form to which receptors respond such as light, heat, pressure, and chemical changes.

Question 16

Sensory receptors

Answer 16

An efferent neuron’s peripheral ending, which is specialized to respond to a particular stimulus in its environment.

Question 17

Chemoreceptor

Answer 17

A sensory receptor sensitive to specific chemicals.

Question 18

Photoreceptor

Answer 18

A sensory receptor responsive to light.

Question 19

Thermoreceptor

Answer 19

A sensory receptor responsive to heat and cold.

Question 20

Mechanoreceptor

Answer 20

A sensory receptor responsive to mechanical enegry; such as stretching or bending.

Question 21

Nociceptor

Answer 21

A pain receptor, sensitive to tissue damage.

Question 22

Proprioceptor

Answer 22

A sensory receptor responsive to body position and movement.

Question 23

Acuity

Answer 23

Discriminative ability, the ability to discern between two different points of stimulation

Question 24

Receptive field

Answer 24

The circumscribed region surrounding a sensory neuron within which the neuron responds to stimulus information

Question 25

Cutaneous receptors

Answer 25

The cutaneous receptors’ are the types of sensory receptor found in the dermis or epidermis. They are a part of the somatosensory system. Cutaneous receptors include cutaneous mechanoreceptors, nociceptors (pain) and thermoreceptors (temperature).

Question 26

Adequate stimulus

Answer 26

the specific stimulus or modality that a receptor is specialized to respond to.

Question 27

Tonic receptors

Answer 27

Do not adapt or adapt slowly.

Question 28

Phasic receptors

Answer 28

Rapidly adapting receptors.

Question 29

Generator potentials

Answer 29

stationary depolarization of a receptor that occurs in response to a stimulus and is graded according to its intensity and that results in an action potential when the appropriate threshold is reached

Question 30

Rods

Answer 30

The eye’s photoreceptors used for night vision.

Question 31

Cones

Answer 31

The eye’s photoreceptors used for color vision in the light.

Question 32

Fovea centralis

Answer 32

Exact center of the retina; region with the greatest acuity.

Question 33

Optic disk/Blind spot

Answer 33

Blind spot, lacks photoreceptors.

Route for passage of the optic nerve and blood vessels

Question 34

Accommodation

Answer 34

The ability to adjust the strength of the lens in the eye so that both near and far sources can be focused on the retina.

Question 35

Refelx arc

Answer 35

includes;

1. sensory receptor
2. afferent pathway
3. integrating center
4. efferent pathway
5. effector

Question 36

Golgi tendon organ

Answer 36

they can respond to changes in the muscle’s tension rather than to changes in its length.

Question 37

Muscle spindle apparatus

Answer 37

Muscle spindles are stretch receptors within the body of a muscle that primarily detect changes in the length of the muscle. They convey length information to the central nervous system via afferent nerve fibers.

Question 38

Intrafusal fibers

Answer 38

Lie within the spindle-shaped connective tissue capsules

Question 39

Extrafusal fibers

Answer 39

Ordinary muscle fibers

Question 40

Nuclear bag fiber

Answer 40

Sudden stretch.
A nuclear bag fiber is a type of intrafusal muscle fiber that lies in the center of a muscle spindle. Each has many nuclei concentrated in bags and they cause excitation of both the primary and secondary nerve fibers. There are two kinds of bag fibers based upon contraction speed and motor innervation.

Question 41

Nuclear chain fibers

Answer 41

Sustained stretch.

Question 42

Alpha motor neurons

Answer 42

Motor neurons that supply the extrafusal fibers

Question 43

Gamma motor neurons

Answer 43

The efferent neuron that innervates a muscle spindle’s intrafusal fibers.

Question 44

Coactivation

Answer 44

Simultaneous stimulation.

Takes the slack out of the spindle fibers as the whole muscle shortens.

Question 45

Monosynaptic stretch reflex

Answer 45

local negative feedback mechanism to resist any passive changes in muscle length so that optimal resting length is maintained.

Question 46

Reciprocal innervation

Answer 46

Stimulation of the nerve supply to one muscle and simultaneous inhibition of the nerves to antagonistic muscle.

Question 47

Crossed-extensor reflex

Answer 47

a reflex in which the contralateral limb compensates for loss of support when the ipsilateral limb withdraws from painful stimulus in a withdrawal reflex.