The central nervous system- CNS

Question 1

Neuroglia

Answer 1

Cells that form connective tissue in the nervous system, usually providing structural support and protection for neurones.

Includes:
Astrocytes
Oligodendrocytes
Schwann cells
Microglia

Neuroglia accounts for most of the nervous system, compared to neurones.

Question 2

Astrocytes

Answer 2

Neuroglia cells present in the CNS.

• Provides structural support for neurones.
• Supplies neurones with nutrients like glucose and lactate.
• Helps to remove excess K+ from neurones.
• Involved in repair of axons.

Question 3

Oligodendrocytes

Answer 3

Neuroglia cells in the CNS.

• Responsible for the production and maintenance of the myelin sheath in myelinated axons.
• One oligodendrocyte can form myelin sheaths on multiples neurones.

Question 4

Microglia

Answer 4

Neuroglia cells of the CNS.

• Specialised macrophage that gives immunological protection.
• Releases H2O2, making it cytotoxic to pathogenic cells.
• Can also promote repair of axons.

Question 5

Schwann cells

Answer 5

Neuroglia cells of the PNS.

• Responsible for producing myelin sheath.
• One schwann cell is only able to provide myelin for one neurone.
• Also involved in the regeneration of axons.

Question 6

Synapses

Answer 6

The structure that allows communication between neurones.

Can be chemical or electrical.

Chemical: uses neurotransmitters to send signals and involves the opening of Ca2+ channels.

Electrical: Neurones require contact depending signalling which allow direct flow of ions.

Question 7

Neurones

Answer 7

Nerve cells of the nervous system that carry information.

Can be:
Unipolar
Bipolar
Multipolar

Afferent: carries information to the CNS- sensory.
Efferent: carries information away from the CNS to effect organs- motor

Question 8

Unipolar neurones

Answer 8

Neurones with only one axon.

The cell body is present in the ganglia close to the intervestrial foramen.

Example: primary sensory neurones.

Question 9

Bipolar neurones

Answer 9

Neurones with an axon and dendron.

Dendron carries signal to the cell body whilst axon carries the signal away from the cell body.

Example: specialised sensory neurones that detect pain, touch.
Those found in the retina.

Question 10

Multipolar neurones

Answer 10

Neurones with one axon and multiple dendrons.

Seen in motor neurones and multiple neurones in the brain.

Question 11

Compare myelinated axons from unmyelinated axons.

Answer 11

Myelinated: Much more rapid conduction of signals due to saltatory conduction.
Can conduct signals up to 120 m/s

Unmyelinated: Much slower conduction due to propagated signal across the axon
Can only conduct signals up to 1.5 m/5

• Seen in pain fibres.

Question 12

Central nervous system

Answer 12

Composed of the brain and spinal cord:

Brain: forebrain, midbrain and hindbrain

Spinal cord: Enclosed in vertebrae.
Segmented:
- Cervical
- Thoracic
- Lumbar
- Sacral

Question 13

Brain

Answer 13

Composed of grey and white matter.
Grey= Cell bodies and synapses
White= myelinated axons

Divided into:
Midbrain
Hindbrain
Forebrain

Question 14

Midbrain and hindbrain

Answer 14

Forms the brainstem

Contains:
Pons (hindbrain)
Cerebellum (hindbrain)
Tectum (mid)
Cerebral peduncle (mid)
Medulla oblongata (hind)

Function:

• Connects cerebral cortex to the spinal cord.
• Controls respiratory and cardiovascular functions.

Question 15

Cerebellum

Answer 15

Part of the hindbrain

Coordinates complex, fine motor control

Question 16

Forebrain

Answer 16

Composed of:

• Cerebral hemisphere
• Thalamus
• Hypothalamus

The cerebral hemisphere is divided into 4 lobes:
Parietal
Frontal
Occiptal
Temporal

Question 17

Cerebral hemisphere

Answer 17

Part of the forebrain divided into 4 lobes, responsible for processing sensory information:

Parietal: contains somatosensory cortex

Frontal: Involved in the primary motor cortex and cognition.

Temporal: Contains olfaction and auditory cortices.

Occipital: Contains visual cortex.

The whole hemispheres is composed of:
Cerebrum
Cerebral cortex- grey matter that is highly folded and responsible for 80% of cognition

Question 18

Thalamus

Answer 18

Part of the forebrain:

Relays sensory information from the brain stem into all lobes in the brain.

HOWEVER, it does not relay sensory information regarding smell.

Question 19

Hypothalamus

Answer 19

Part of the forebrain, inferior to the thalamus:

Involved in homeostasis of various process using the autonomic nervous system

Also involved in endocrine functions: secreting hormones

Question 20

Spinal cord

Answer 20

Bundle of nervous tissue enclosed in the vertebral column. Responsible for motor and sensory functions

Composed of grey matter in the inner core: neuronal cell bodies
White matter outer layer: Myelinated axons.

Starts at C1 and stops at L1.
Divided into regions:
Cervical: C1- C8. C8 stops below C7. Nerves are above its associated vertebrae in C1-C7, then below in the rest.

Thoracic: T1-T12

Lumbar: L1-L5

Sacral: S1-S5

1 coccygeal nerve.

Contains dorsal end (posterior)- sensory neurones enter
Ventral end (anterior)- motor neurones exit.