5. The Central nervous system

Question 1

What is the CNS made of?

Answer 1

The brain and spinal cord

Question 2

What three structures protect the spinal cord?

Answer 2

Bones
Meninges
Cerebrospinal fluid

Question 3

How does bone protect the CNS?

Answer 3

bone is the outermost protective layer

Brain is protected by the cranium and the spinal cord runs through a hole in the vertebrae (vertebral column)

Question 4

What are meninges?

Answer 4

connective tissue membranes that cover the entire CNS

Question 5

What are the three layers of meninges?

Answer 5

Outer layer- tough and fibrous, sticking closely to the bones of the skull but less so to the inside of the vertebral canal
Middle layer- loose mesh of fibres
Inner layer- highly delicate, containing many blood vessels, sticking closely to the surface of the brain and spinal cord

Question 6

What is CSF?

Answer 6

it occupies the space between the middle and inner meninges layer
Circulates the cavities in the brain and vertebral canal
It is clear with a few cells and some glucose, protein, urea and salts

Question 7

How does the CSF protect the CNS?

Answer 7

it acts as a shock absorber, also supporting the brain
It is formed from the blood, circulating around and through the CNS, eventually reentering the blood capillaries
During circulation, it takes nutrients of the brain and spina cord and carries away their wastes

Question 8

What are the three functions of CSF?

Answer 8

Protection, support and transport

Question 9

What is the cerebrum?

Answer 9

Largest part of the brain, consisting of an outer surface of grey matter (cerebral cortex), an inner layer of white matter and then a deep layer of grey matter (basal ganglia)

Question 10

How many neurons does the cortex contain in the CNS?

Answer 10

70% of all the neurons in the CNS

Question 11

How is the brain divided in terms of sulci and fissures?

Answer 11

The convultions of the brain are separated by shallow downfolds (sulci) and deep downfolds (fissures)

Question 12

What is the deepest fissure in the brain?

Answer 12

The longitudinal fissure, this separates the left and right cerebral hemispheres

Question 13

Where do the two hemispheres join in the brain?

Answer 13

at the corpus callosum which is an area of white matter consisting of transverse fibres

Question 14

Are all sulci different in each person?

Answer 14

Yes, to a degree, there are fairly constant sulci which can subdivide the hemisphere into 4 lobes, frontal, temporal, occipital and parietal

Question 15

What is the fifth lobe in the cerebrum?

Answer 15

The insula, which if found deep inside the cerebrum

Question 16

What are the functions of the cerebrum?

Answer 16

Mental activities (thinking, reasoning, learning, memory, intelligence, sense of responsibility)
Perception of senses
Initiation and control of muscle coordination

Question 17

How do scientists investigate the functions of the cortex?

Answer 17

• studying brain waves detected in electrodes placed on the scalp recorded as an electroencephalogram
• electrically stimulating areas and observed responses
• examining changes in cerebral blood flow during physical and mental activity
• observing effects on people from brain damage or disease
• experimenting on other mammals

Question 18

Where are the key functional areas of the cortex?

Answer 18

Sensory area: interpret impulses from other receptors
Motor areas: controls muscular movements
Association areas: concerned with intellectual and emotional processes

Question 19

What functions are controlled in each hemisphere of the brain?

Answer 19

In right handed people- the right frontal lobe, left occipital lobe and left parietal lobe is wider
Specialised functions occur often only in one hemisphere
Language ability is controlled by the left
Musical and artistic ability is controlled by the right

Question 20

What is a key feature of the cerebrum?

Answer 20

Memory- activity is linked to association areas of the brain
Memories aren’t stored in individual cells but are pathways of nerve cells
When a memory is stored, new links are made between neurons and existing links are modified

Question 21

What is white matter?

Answer 21

between the cortex and basal ganglia
Is composed of bundles of myelinated nerve fibres
Inside the CNS these bundles are called tracts
Outside the CNS they are called nerves

Question 22

What are the three kinds of tracts that occur in the white matter?

Answer 22

1. Tracts that connect areas of the cortex within the same hemisphere
2. Tracts that carry impulses between left and right hemisphere
3. Those that connect the cortex to other parts of the CNS

Question 23

What is basal ganglia?

Answer 23

The masses of grey matter inside each hemisphere consisting of groups of nerve cell bdies associated with control of skeletal muscles

Question 24

What is the corpus callsoum?

Answer 24

A wide band of nerve fibres that lie underneath the cerebrum at the base of the longitudinal fissure
Nerve fibres cross from one cerebral hemisphere to another, allowing two sides of the cerebrum to communicate

Question 25

What is the cerebellum?

Answer 25

It lies at the rear of the cerebrum
Is the second largest part of the brain
Its surface folds into a series of parallel ridges
The outer layer is grey matter and the inside is white matter than branches that branch to all parts of the cerebellum

Question 26

What are key functions of the cerebellum?

Answer 26

Controls posture, balance and fine motor skills

All functions are unconscious and as such, impulses don’t originate in the cerebellum

Question 27

Where does the cerebellum receive information from?

Answer 27

Sensory information- from the inner ear (posture and balance)
Stretch receptors- in the skeletal muscles

Question 28

What would happen if we didn’t have the cerebellum?

Answer 28

We would still be able to move, however movements would be spasmodic and uncontrolled

Question 29

What does the hypothalamus regulate?

Answer 29

ANS, regulating heart beat, blood pressure, digestive secretion, alimentary movements, pupil diameter
Body temperature
Food and water intake
Patterns of waking and sleeping
Urinary actions
Emotional responses
Secretions of hormones and coordination of the endocrine system

Question 30

What is the medulla oblongata?

Answer 30

A continuation of the spinal cord, around 3cm long
Many nerve fibres pass through the medulla
Also serves a role in automatically adjusting body functions

Question 31

What does the medulla oblongata contain?

Answer 31

The cardiac centre to regulate the rate and force of the heartbeat
The respiratory centre which controls rate and depth of breathing
Vasomotor centre which regulates the diameter of blood vessels
Contains areas that regulate various reflexes (swallowing, sneezing, coughing and vomiting)
All centres of medulla oblongata are controlled by high centres in the brain (esp. hypothalamus)

Question 32

What is the spinal cord?

Answer 32

A structure that extends from the foramen magnum (opening at base of skull) to the second lumbar vertebrae (wait level)

Question 33

What is different in the meningeal layers of the spine?

Answer 33

The outermost layer isn’t joined to the bone, instead there is space for fat, connective tissue and blood vessels which serve as padding around the cord and allow it to bend

Question 34

What is the difference between white a grey matter?

Answer 34

White is myelinated and grey is nerve cell bodies that are unmyelinated

Question 35

What is different about the white and grey matter in the brain and spine?

Answer 35

unlike the brain, the grey matter is in the centre of the spinal cord and is surrounded by white matter

Question 36

What is the central canal?

Answer 36

The centre of the grey matter in the spine which runs the length of the spinal cord and contains cerebrospinal fluid

Question 37

What are ascending tracts in the spinal cord?

Answer 37

They are sensory axons that carry impulses towards the brain

Question 38

What are descending tracts?

Answer 38

Motor axons that conduct impulses away from the brain

Question 39

What are the key functions of the spinal cord?

Answer 39

Carry sensory impulses to the brain
Motor impulses away from the brain
Integrate certain reflexes
Structure/support for the body