Central Nervous System

Definition of Vetrebrate Nervous System

Constellation of neurons & glia cells, organised into functional neural circuits. Enable neural control of physiology & behaviour

2 anatomical divisions of NS in animals and what they contain

• CNS (brain & spinal cord)

• PNS (Autonomic NS, Enteric NS, Somatic [motor] NS)

Glia function

• Modulates neuronal signalling

• insulates neuron processes

• provides immune function for CNS

Microglia function

• Mobile

• 1st major Immune Defense Mechanism (Clean up cell debris)

Astrocytes function

support function for CNS neurons, protect BBB, regulates NTs & regulates neuronal activity.

Oligodendrocytes

Forms myelin sheath around neuronal axons in CNS
- Can myelinate ~40 axons

Ependymal Cells

• Specialised ciliated epithelial cells (found in ventricles) & Central Canal of Spinal cord.

• Produces CSF

• Has microvilli to help circulate CSF around CNS.

How does the CNS develop initially

Anterior end of the neural tube folds and swells, creating 3 major brain divisions

The brain subdivision & areas of Forebrain (Prosencephalon)

• Telencephalon contains the cerebral cortex (Sensory, motor function), Limbic System (Emotion system), Hippocampus (Memory & Learning) & Basal Ganglia (motor control).

• Diencephalon contains hypothalamus (Circadian Clock) & thalamus (Major sensory relay).

The brain subdivision & areas of Midbrain (Mesencephalon)

Mesencephalon contains Superior (Visual Integration) & Inferior Colliculus

(Audio Integration).

The brain subdivision & areas of Hindbrain

• Metencephalon contains Cerebellum (Motor Coordination) & Pons (Descending motor control).

• Myelencephalon contains Medulla Oblongata (Autonomic & Respiratory Control)

Grey Matter & Location

Clump/Lots of cell bodies, distributed in the CNS

White matter

Lots of myelinated axons.

Nucleus & Ganglion difference

N => Collection of neuron cell bodies in CNS.

G=> Collection of neuron cell bodies in PNS.

Nerve & Tract Difference

T => Bundles of axons in the CNS

N => Bundles of axons in PNS

What nerves & neurons does the PNS consist of

Cranial Nerves (Connect CNS to brain), contain Afferent only.

Spinal Nerves (Connects PNS to spinal cord) contain both afferent & efferent.

How do sensory neurons pass through the spinal cord?

Sensory info enters spinal cord through dorsal root (Afferent neuron axons) , passes into the dorsal horn, and enters CNS.

How do motor neurons leave through the spinal cord?

motor info leaves via the ventral horn and into the ventral root, into the spinal nerve and to the effector,

Whats in the Efferent Division of the PNS

Somatic NS, ANS

What does Somatic (motor) NS do

efferent innervation to striated muscles (voluntary control).

• Uses ONE neurone to connect CNS with effector

What does Autonomous NS do

Efferent innervation to tissues (viscera)

• Uses TWO neurones (‘chained ’) to connect CNS to effector.

1st is Preganglionic Neuron, 2nd is Postganglionic Neuron

3 divisions the ANS is split into

ENS, Sympathetic & Parasympathetic.

Whats the ENS?

an involuntary NS, with 2 nerve plexuses (Myenteric, Submucosal Plexus). involved in regulating GastroIntestinal Activity.

Function of myenteric Plexus

Regulates motor activity

Function of Submucosal Plexus

Regulates Secretomotor activity

Where in the CNS do Sympathetic & Parasympathetic Neurones Leave at

Sym → (T1 to L2)

Para→ (S2 to S4)

Difference between Sympathetic & Para preganglionic Neurons

Symp → Relative short axons, make up sympathetic chain which lies near vertebral column.

Para → Long axons, autonomic ganglia are located close to target organ

What makes the Sympathetic chain

Sympathetic autonomic ganglia.

What NT do sympathetic & Parasympathetic Preganglionic neurones use

Acetylcholine

What NT do sympathetic Postganglionic neurones use

Most use Noreadrenalne/Noreprinephrine, some use ACh (e.g sweat glands), some release Co-transmitter (ATP, dopamine, neuronpeptides)

What NT do Parasympathetic Preganglionic neurones use

Most use ACh, some use NA instead, some relese Co-transmitters