The central nervous system- CNS Flashcards
Neuroglia
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.
Astrocytes
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.
Oligodendrocytes
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.
Microglia
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.
Schwann cells
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.
Synapses
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.
Neurones
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
Unipolar neurones
Neurones with only one axon.
The cell body is present in the ganglia close to the intervestrial foramen.
Example: primary sensory neurones.
Bipolar neurones
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.
Multipolar neurones
Neurones with one axon and multiple dendrons.
Seen in motor neurones and multiple neurones in the brain.
Compare myelinated axons from unmyelinated axons.
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.
Central nervous system
Composed of the brain and spinal cord:
Brain: forebrain, midbrain and hindbrain
Spinal cord: Enclosed in vertebrae. Segmented: - Cervical - Thoracic - Lumbar - Sacral
Brain
Composed of grey and white matter.
Grey= Cell bodies and synapses
White= myelinated axons
Divided into:
Midbrain
Hindbrain
Forebrain
Midbrain and hindbrain
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.
Cerebellum
Part of the hindbrain
Coordinates complex, fine motor control
Forebrain
Composed of:
- Cerebral hemisphere
- Thalamus
- Hypothalamus
The cerebral hemisphere is divided into 4 lobes: Parietal Frontal Occiptal Temporal
Cerebral hemisphere
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
Thalamus
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.
Hypothalamus
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
Spinal cord
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.
