Anatomy - Week 2 Overview Of Nervous System

Question 1

What is the definition of the nervous system?

Answer 1

The nervous system is a highly complex and specialised system that reacts to both external and internal stimuli and then directs the body to respond in the appropriate manner

Question 2

What are the 3 main components of the nervous system?

Answer 2

Sensory (receiving/input)
Integrative (deciding/process)
Motor (reacting/output)

Question 3

What is the sensory function of the nervous system?

Answer 3

(Receiving) - sensory receptors gather information by detecting changes inside and outside the body. They monitor external environmental factors such as light and sound as well as temperature, blood pressure, oxygen concentration and other conditions of the body’s internal environment. This sensory information is carried to the spinal cord and Brain bye father spinal and cranial nerve

Question 4

What is the integrative function? (Intermediate)

Answer 4

(Processing) - sensory receptors v=convert their information into nerve impulses, which are transmitted to the central nervous system via peripheral nerves. The information is analysed, processed and decisions made for the appropriate responses.

Question 5

What is the motor function? (Action)

Answer 5

(Reacting)- once sensory information is integrated, the nervous system may elect an appropriate response. Neutrons carry impulses from the CNS through the peripheral nervous system to responsive structures known as effectors. Effectors include muscles that contract and glands that secrete in response to nerve stimulation

Question 6

What is the central nervous system?

Answer 6

Includes the brain which is encased in the skull and the spinal cord contained within the vertebral canal. The CNS contains around 100billion neurones in the brain.
It has a sensory component which processes many kinds of different incoming sensory information at a conscious and/ or unconscious level. It has a motor component from which outgoing signals originate and an association components which connects and coordinates the various CNS centres.

Question 7

What is the peripheral nervous system?

Answer 7

The PNS comprises all the nerve fibres and cell bodies outside of the CNS that conduct impulses to or away from it. PNS consists of the 12 pairs of cranial nerves and 31 pairs of spinal nerves. Each pair connects the spinal cord with a specific region of the body.

Question 8

What’s the positions of the 31 pairs of spinal nerves?

Answer 8

8 cervical 
12 thoracic 
5 lumbar 
5 sacral 
1 coccygeal

Question 9

What is a Neuron?

Answer 9

It is the basic functional unit of the nervous system. They are specialised cells which react to stimuli and convert them into an electrical signal (action potential) neurons have a cell body, dendrites and an axon.

Question 10

What is a dendrite?

Answer 10

Dentrites are the receiving portions of the neuron. They are highly branched, providing receptive surfaces with which they interface with processes from other neurons to permit communication. (Although a neuron may have several dendrites, it will only have one axon.

Question 11

What is an axon?

Answer 11

The axon conduct nerve impulses away from the cell body towards the synaptic knob (axon terminals) where the signal is passed to the adjoining cells

Question 12

What is a peripheral nerve?

Answer 12

Is a bundle of myelinated axons that travel outside of the CNS

Question 13

What is gray matter?

Answer 13

Is a number of cell bodies that are grouped together, which appear gray. Gray matter is found in the central region of the spinal cord surrounding the central canal, on the surfaces of the cerebral and cerebellar hemispheres and scattered throughout the CNS as nuclei

Question 14

What is white matter?

Answer 14

Is called due to the presence of myelin. Myelin has a shiny white appearance and imparts this colour to grouped bundles of myelinated.

Question 15

What is a tract?

Answer 15

It is a group of myelinated axons that travel together within the CNS share a common origin, destination and function. They run entirely within the brain and spinal cord

Question 16

What is a nucleus?

Answer 16

It is a group of neuronal cell bodies located in the same area and sharing the same function within the CNS

Question 17

What is ganglia? ‘

Answer 17

They are a group of neuronal cell bodies, however they are found outside the CNS as a discrete swelling

Question 18

What are afferent fibres?

Answer 18

They are axons that carry impulses (signals) towards the CNS. These are usually sensory to ascending fibres.

Question 19

What are efferent fibres?

Answer 19

Are axons that carry impulses away from the CNS. These are usually motor or descending fibres.

Question 20

What are sulci?

Answer 20

They are depressions or grooves between the ridges of the cerebral hemispheres

Question 21

What are gyri?

Answer 21

They are folds or ridges that can be seen in the folding appearance of the cerebral hemisphere.

Question 22

What are the three different kinds of tracts (or bundle of axons), which connect one part of the brain to another within the white matter?

Answer 22

1. Association fibres
2. Commissural fibres
3. Projection fibres

Question 23

What are association fibres?

Answer 23

They interconnect areas of the Cortex within one hemisphere (they stay on the same side of the brain)

1. Short association fibres connect areas in adjacent gyri. They can cross one or two sulci example eg arcuate fibres
2. Long association fibres can also be referred to as fasciculi. Example eg superior longitudinal fasciculus.

Question 24

What are commissural fibres?

Answer 24

They are fibres that cross the midline to connect areas of the cortex in one hemisphere with the same areas in the opposite hemisphere, connecting similar functional areas to enable coordination of the activity between the two hemisphere ie. corpus Callosum.

Question 25

What are projection fibres?

Answer 25

They are nerve fibres connecting cerebral cortex with other centres in brain or spinal cord. They travel to or from the Cortex or descend to spinal cord ie. they come from all parts of the cortex in the corona radiata and converge into a compact bundle called the internal capsule. The names of these fibres always follow the pattern of where they originate and where they end.

Question 26

Describe and explain what cranial nerves are?

Answer 26

There are 12 pairs of cranial nerves. They are the nerves that emerge directly from the brain (including the brain stem), in contrast to spinal nerves (which emerge from segments of the spinal cord).
They are identified either by numbers indicating their order (olfactory nerve CN1) or the general distribution of their fibres (facial nerve CNV11)
Most cranial nerves are mixed nerves (both sensory and motor) but some of those associated with the special senses such as smell vision and hearing and balance have only sensory.

Question 27

Where does the spinal cord exit the skull?

Answer 27

Through the foramen magnum

Question 28

What’s along the course of the spinal cord?

Answer 28

31 pairs of mixed spinal nerves which arise anteriorly and posteriorly as spinal rootlets.
The rootlets coming from the spinal cord join to form the spinal nerves proper and arise from each side of the spinal cord and exit the vertebrae as 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal

Question 29

What happens due to the fact that the spinal cord is not as long as the vertebral column? (typically end at the inferior border of l1)

Answer 29

The lower lumbar and sacral nerve roots must travel down and exit the intervertebral foramina at their respective vertebral level. The nerve roots descending past the termination of the spinal cord resemble a horses tail and are referred to as the cauda equina.

Question 30

What is the Filum terminale?

Answer 30

It is a thin strand of fibrous tissue (modification of pia mater) that extends from conus medullaris to pierce caudal end of Dural at S2 vertebral level.

Question 31

What is the structure of spinal nerves?

Answer 31

Each spinal nerve is formed from combination of nerve fibres from its posterior and anterior roots.

Question 32

What is the posterior root?

Answer 32

The afferent sensory root and carries sensory information to the brain

Question 33

What is the anterior root?

Answer 33

The efferent motor root and carries motor root and carries motor information from the brain. The spinal nerve emerges from the spinal column through an opening (intervertebral foramen) between adjacent vertbrae.

Question 34

Outside the the vertebral column, what does the nerve branch into?

Answer 34

1. The posterior ramus

2. Anterior ramus

Question 35

What is the posterior ramus?

Answer 35

It’s contains nerves that serve the posterior portions of the trunk to and from the skin and muscles of the back.

Question 36

What is the anterior ramus?

Answer 36

It contains nerves that serve the remaining anterior parts of the trunk and the upper and lower limbs

Question 37

What is a reflex arc?

Answer 37

It is an involuntary response to a specific stimulus. Nerve impulses follow nerve pathways as they travel through the nervous system, which include only a few neurons constitutes a reflex arc. Skeletal muscle is regarded as under voluntary control. Many reflexes occur in which sensory stimuli automatically produce motor response.