Week 10

Question 1

pns- afferent division

Answer 1

conveys information from the sensors in the periphery to the cns

Question 1

spinal cord

Answer 1

long cylinder of nerve tissue which extends down from the brainstem to the second lumbar vertebrae

Question 2

pns- efferent division

Answer 2

somatic nervous system- nerve fibres innervate skeletal muscle
autonomic nervous system- nerve fibers innervate smooth and cardiac muscle and glands
- sympathetic and parasympathetic

Question 3

neuroglia

Answer 3

non excitable
physical and biochemical support for neurons
occupy about half of the volume of the brain
four major types of glial cels serve as the connective tissue of the cns and as such help support the neurons both physically and metabolically

Question 4

neuron

Answer 4

• excitable
• carry electrical signals
  neuron is specialized to transmit electrical signals
  cell body
  axon
  dendrites

Question 5

mylin sheath

Answer 5

discontinuos sheath around the axon
composed of lipid and protein
nodes of ranvier: spaces between the segments of myelin sheath
- salutary conduction

Question 6

salutary conduction

Answer 6

signal leaps from node to node
mylenaited nerve fibres have much faster conduction velocities than unmyleniated fibres

Question 7

multiple sclerosis

Answer 7

autoimmune disease- body attacks myelin sheath within cns
break down in communication
exposed nerves can be destroyed irreversibly
fatigue, vision changes, numbness, loss of coordination, muscle weakness, cognitive dysfunction

Question 8

synapse

Answer 8

the region where a neuron meets its target cell
chemical synapse: electrical signal converted to chemical signal for transmission to post synaptic cell

Question 9

neuron structure

Answer 9

afferent neurons: carry impulses from the sensory receptors into spinal cord or brain
efferent neurons: transit impulses from the cns out of the effector organs- muscles and glands
interneurons: lie entirely within the cns. they account for 99% of all nerve cells

Question 10

resting membrane potential

Answer 10

due to selective permeability characteristics of the nerve cell membrane a potential difference exists between the inside and outside

Question 11

action potential

Answer 11

high concentration of positive sodium ions on the outside of the membrane causes it be electrically positive, while the inside is electrically negative, this causes sodium ions to rush to the inside of the nerve and reverses polarity

Question 12

tetrodotoxtin

Answer 12

acts on the cns and pns
blocks sodium channels
prevents action potential
symptoms of poisoning: paresthesia in mouth then extremities
weakness, lack of coordination, paralysis, cyanosis
death within 4-6 hours

Question 13

nerve to nerve synapses

Answer 13

nervous information is relayed across the synaptic cleft by means of a chemical transmitter substance

Question 14

neural muscular junction

Answer 14

consists of axon terminals, motor end plates on the muscle membrane and schwas cell sheaths

Question 15

spinal cord

Answer 15

The spinal cord is enlarged in two regions for innervation of the limbs:
a) The cervical enlargement which extends from the C4 through T1 segments of the spinal cord
b) The lumbosacral enlargement which extends from the T11 through L1 segments
of the spinal cord

Question 16

plexus

Answer 16

a network on converging and diverging nerve fibres or blood vessels

Question 17

dorsal roots

Answer 17

contain afferent fibres that carry information from the periphery to the spinal cord and brain

Question 18

ventral roots

Answer 18

contain efferent fibers to the skeletal fibres

Question 19

ganglion

Answer 19

collection of nerve cell bodies located outside the cns

Question 20

spinal cord injury

Answer 20

transection (complete cut) of the spinal cord results in loss of all sensation and voluntary movement inferior to the point of damage

Question 21

risk hanson

Answer 21

goal is to create an inclusive world where people with disabilities can reach their full potential

Question 22

proprioceptors

Answer 22

Conduct sensory information to the CNS from muscles, tendons, ligaments, and joints kinesthetic sense
* Kinesthetic sense: gives information about the location of parts of our body in relation to their environment.

Question 23

muscle spindles

Answer 23

change in length

Question 24

golgi tendon organ

Answer 24

change in tension

Question 25

joint receptors

Answer 25

change in angle

Question 26

muscle spindles

Answer 26

Structure - several modified muscle fibers,
– four to 10 millimetres in length,
– containedinacapsule,
– with sensory nerve spiralling around its center.

Question 27

muscle spindles function

Answer 27

send info to the cns regarding the degree of muscle stretch
- activation of the exact number of motor units to overcome a given resistance

Question 28

tonic stretch

Answer 28

concerned with the final length of the muscle fibres

Question 29

phasic stretch

Answer 29

spindle responds to the velocity of the change of length

Question 30

gamma system

Answer 30

gamma efferent fibers innerverate the contractile ends of the intrafusal fibres
When the alpha motor neurons are activated, the gamma motor neurons are also activated (coactivation).
– Gamma system provides the mechanism for maintaining the spindle at peak operation at all muscle lengths.
– They help maintain muscle spindle sensitivity

Question 31

stretch reflex

Answer 31

Muscle spindles are distributed throughout the muscle. Their density varies with the degree of control required by a given muscle.

Question 32

five functional components of stretch reflex

Answer 32

Receptor (muscle spindle)
* Afferent (sensory) neuron
* Integrating Centre (spinal cord)
* Efferent (motor) neuron (both alpha and gamma) * Effector (muscle contraction)

Question 33

golgi tendon organs location

Answer 33

encapsulated in tendon fibres near the junction of the muscle and tendon fibres
they are in a series with muscle fibres rather than in parallel as are muscle spindles
when a muscle contracts the GTO is stretched

Question 34

gto functions

Answer 34

the firing rate is sensitive to changes in tension of the muscle
sensory input about the tension produced by muscles is a useful for a variety of motor acts such as maintaining a steady grip on an object
when stimulated by excessive tension send sensory information to the cns which causes contracted muscle to relax

Question 35

joint receptors

Answer 35

supply information to the cns concerning joint angle, acceleration of joint, pressure, pain

Question 36

control of motor functions

Answer 36

cerebral cortex and cerebellum are the main centres employed in learning new motor skills , voluntary control of movement patterns

Question 37

primary motor cortex

Answer 37

ocated at the rear of the frontal lobe of the cerebral cortex.
* Stimulation of different areas of the primary motor cortex brings
about movement in different, specific areas of the body.
* Contains the motor homunculus. However, no coordinated movement can be elicited.

Question 38

cerebral cortex

Answer 38

Corticospinal tract
* long axons which carry impulses from the primary motor cortex
where their cell bodies are located directly to lower motorneurons in spinal cord spinal nerves
* The corticospinal system primarily mediates performance of fine, discrete, voluntary movements of the hands and fingers.

Question 39

premotor cortex

Answer 39

One of the three higher areas that command the primary motor cortex.
* Located on the lateral surface of each cerebral hemisphere in front of the primary motor cortex.

Question 40

somatosensory cortex

Answer 40

The site for initial processing of pressure, touch, heat pain and proprioceptive input
* Located in the anterior section of the parietal lobe, immediately behind the central sulcus.
* Each region within the somatosensory cortex receives sensory input from a specific area of the body.

Question 41

cerebellum

Answer 41

It functions by means of intricate feedback circuits to monitor and coordinate other areas of the brain involved in motor control.
* It receives signals concerning motor output from the cortex and sensory information from:
* receptors in muscles, tendons, joints and skin,
* visual, auditory and vestibular end organs

Question 42

cerebellum function

Answer 42

Function - the major comparing, evaluating, and integrating center for
* postural adjustments, – locomotion,
– maintenance of equilibrium,
– perceptions of speed of body movement,
– and general motor coordination.
* Damage to the cerebellum results in impaired motor control.

Question 43

symptoms of cerebellum damage

Answer 43

They cannot perform movements smoothly
* They walk awkwardly with their feet well apart. They have such difficulty maintaining their balance that their gait appears drunken.
* They cannot start or stop movements quickly or easily
* They cannot easily combine the movements of several joints into a single, smooth, coordinated motion. To move the arm, they must first move the shoulder, then the elbow, and finally the wrist.