Neural control and movement

Question 1

Divisions of the nervous system

Answer 1

Central nervous system (CNS)
1) Brain
Newer more sophisticated regions are piled on top of older, more primitive regions
a) Forebrain
(i) Cerebrum constitutes about 80% of total
brain weight - cerebral cortex, basal nuclei
(ii) Diencephalon - thalamus, hypothalamus
b) Cerebellum
c) Brainstem - continuous with the spinal cord - medulla, pons, midbrain

2) spinal cord
- long cylinder of nerve tissue which extends down from the brain stem to the second lumbar vertebrae. 45 cm long and 2 cm in diameter. Protected by the vertebral column and associated ligaments and muscles, the spinal meninges and the cerebrospinal fluid.

Peripheral Nervous System (PNS)
consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves
1) afferent division
2) efferent division (somatic nervous system AND autonomic nervous system)
- sympathetic division
- parasympathetic division

Question 2

Afferent division

Answer 2

nerve fibres responsible for bringing sensory information back to the CNS

Question 3

Efferent division

Answer 3

Somatic nervous system
- nerve fibres that innervate skeletal muscle

Autonomic nervous system
- nerve fibres that innervate smooth muscle, cardiac muscle and glands
–> sympathetic (fight or flight) and parasympathetic (rest and digest)

Question 4

Neurologia

Answer 4

• comprised about 90% of cells in CNS
• occupy 1/2 of the volume of the brain

Question 5

Glial cells

Answer 5

there are 4 major types of glial cells that serve as connective tissue of the CNS which help support the neurons physically and metabolically

Question 6

Neuron

Answer 6

A nerve cell specialized to transmit electrical signals/ pass messages from one part of the body to another.

Consists of:
- cell body
- axon
- dendrites

Question 7

Cell body

Answer 7

soma, contains nucleus

Question 8

Axon

Answer 8

a long fiber that conducts impulses away from the cell body
can be known as “nerve fiber”

Question 9

Dendrites

Answer 9

Short projections from the cell body that transmits impulses toward the cell

Question 10

Myelin sheeth

Answer 10

discontinuous sheath around the axon, primarily composed of lipids and proteins
- myelinated nerve fibres have a much faster conduction velocity than unmyelinated fibers

Question 11

Nodes of ranvier

Answer 11

the spaces in between the segments of myelin sheath

Question 12

synapse

Answer 12

the connection of an axon of one nerve to the cell body or dendrites of another nerve

Question 13

Multiple sclerosis

Answer 13

Autoimmune disease where the body attacks myelin sheath
- break down in communication
- exposed nerves can be destroyed irreversibly
- fatigue

Question 14

Neurons can be divided into 3 functional classes

Answer 14

1. Afferent neurons: carry impulses from sensory receptors into spinal cord and brain
2. Efferent neurons: transmit impulses from CNS out to the effector organs - muscle (motor neurons, glands )
3. Inter neurons. Lie entirely in the CNS, they account for 99% of nerve cells

Question 15

Spinal nerve

Answer 15

• actually a nerve trunk
• it contains hundreds of afferent and efferent nerve fibers that are bound together w/ connective tissue sheaths

Question 16

Resting membrane potential

Answer 16

Due to selective permeability characteristics of nerve cell fiber, a high potential difference exist inside and outside of nerve fiber. A high concentration of sodium ions outside of the nerve membrane causes it to be electrically positive and on the inside of the nerve membrane electrically negative

Question 17

Action potential

Answer 17

An appropriate stimuli suddenly causes sodium ions to rush inside of the nerve —> reversal polarity
Once AP has started it spread along the entire length of the nerve fibre

Question 18

Tetrodotoxin

Answer 18

• blocks sodium channels
• prevent AP in nerve cells
• acts on CNS AND PNS
• death wishing 4-6 hours

Question 19

Nerve to nerve synapses

Answer 19

• nervous informations relays across synaptic cleft by means of a chemical substance transmitter
• transmitter substances can be other inhibitory or excitatory

Question 20

What are the impacts of different transmitter substances

Answer 20

They are additive
1. Spatial - when multiple different inputs from different regions add together
2. Temporal- when the same input happens overtime fast enough to add up enough to cause an action potential

Question 21

Neuromuscular junction

Answer 21

Nerve to muscle synapse
The chemical transmitter substance: acetylcholine

Question 22

The spinal cord is enlarged in two regions for innervation of the limbs

Answer 22

1. Cervical enlargement which extends from C4 through T1 segments of the spinal cord
2. Lumbosacral enlargement which extends from T11 through L1 segments of the spinal cord

Question 23

Structure of spinal nerves

Answer 23

8-Cervical
12-thoracic
5-lumbar
5-sacral
1-coccygeal

Question 24

Plexus

Answer 24

A network of diverging and converging nerve fibers and blood vessels

Question 25

Brain and spinal cord are composed of…

Answer 25

White and grey matter

Question 26

Grey matter

Answer 26

The nerve cell body lie and constitute the grey matter

Question 27

White matter

Answer 27

Interconnecting tracts of nerve fibers form white matter

Question 28

What kind of fibres do the following have a) dorsal roots b) ventral roots

Answer 28

a) afferent (sensory) fibres that carry information from the periphery to the brain and spinal cord b) efferent (motor) fibers to the skeletal muscle

Question 29

Where are the cell bodies of the motor axon making up the ventral roots located?

Answer 29

located in the ventral gray horns of the spinal cord

Question 30

Where are the cell bodies of the sensory axons making up the dorsal roots located

Answer 30

located outside of the spina cord in the spinal ganglia

Question 31

Ganglion

Answer 31

a collection of nerve cell bodies located outside the CNS

Question 32

Spinal cord injury

Answer 32

most often due to trauma to the spinal cord, but can be associated with congenital and degenerative disease.

Question 33

Transection

Answer 33

transection is complete cut of the spinal cord that results in loss of sensation and voluntary movement inferior to the point of damage

Question 34

If the cord is transected superior to C5

Answer 34

patient is quadriplegic

Question 35

What transection will cause the patient may cause the patient to die or have respiratory failure

Answer 35

if the transection is above C4

Question 36

A patient is paraplegic is the transection occurs where

Answer 36

if the transection occurs below the cervical segment of the spinal cord

Question 37

ischemia

Answer 37

a deficiency of blood supply to the spinal cord cause by fractures, dislocations, atherosclerosis --> can lead to muscle weakness and paralysis

Question 38

proprioceptors

Answer 38

conduct sensory information to the CNS from muscles, tendons, ligaments and joints

Question 39

kinesthetic sense

Answer 39

gives information about the location of parts of our body in relation to their environment

Question 40

Muscle spindles

Answer 40

several modified muscle fibres, 4-10 millimeters in length, contained in a capsule with a sensory nerve spiralling down its center.

Question 41

Spindle fibers

Answer 41

lie parallel to the regular muscle fibers

Question 42

Function of muscle fibres

Answer 42

send information to the CNS regarding the degree of muscle stretch - activation of the exact number of motor units to overcome a given resistance - with increasing degree of stretch of the muscle spindles, frequency of impulse transmission up the afferent neuron to the spinal cord progressively increases

Question 43

3 ways that the muscle spindles can activate the alpha motor neurone to cause the muscle to contract

Answer 43

1. Tonic stretch - concerned with the final length of the muscle 2. phasic stretch - spindle responds to the velocity of the change of length 3. Gamma system - gamma efferent fibers innervate the contractile ends of intrafusal fibers (when alpha motor neurone are activated so are gamma motor neuron)

Question 44

Stretch reflex

Answer 44

patellar tendon tap

Question 45

Golgi tendon organ (GTO)

Answer 45

Location: encapsulated in the tendon fibers near the junction of the muscle and the tendon fibers - approx 1 millimetre long and 0.1 millimetre in diameter - in series with muscle fibers rather than parallel as are the spindle fibers - when muscle contracts GTO is stretched

Question 46

The function of GTO

Answer 46

The firing rate of GTO is very sensitive to changes in tension of the muscle - sensory input about the tension produced by the muscle is used in a variety of different motor acts such as maintaining a stable grip on an object - when stimulated by excessive tension or stretch--> sensory information is sent to the CNS-->causes the contracted muscle to relax

Question 47

Joint receptors

Answer 47

supply information to the CNS regarding joint angle, acceleration of the joint, pain, and pressure

Question 48

Control of motor functions

Answer 48

the cerebral cortex and cerebellum are the main center employed in learning new motor skills. These areas of the brain initiate voluntary control of movement patterns