nervous system. some interesting facts 85 billion (85,000,000,000) neurons in the human brain. 3,000...

Nervous System

Some Interesting Facts

• 85 billion (85,000,000,000) neurons in the human brain.

• 3,000 years one cell/second • 1 neuron cell body = 10 microns wide

85,000,000,000 neurons = 850 km

• If you use a basketball (diameter = ~24 cm) as the cell body, then your axon would have to be 240,000 cm (2.4 kilometers)

in length!

► A baby's brain is a mystery.

► The mystery begins in the womb -- only four weeks into gestation the first brain cells, the neurons, are already forming at an astonishing rate: 250,000 every minute.

► Billions of neurons will form links with billions of other neurons and eventually there will be trillions and trillions of connections between cells.

► Every cell is precisely in its place, every link between neurons carefully organized. Nothing is random, nothing by chance.

CNS Development

Functions of the Nervous System1. Sensory input

· changes = stimuli

2. Integration· processing

3. Motor output· response to stimuli

(The response activates muscles or glands)

Neuron

Slide 7.10

· Extensions outside the cell body· Dendrites –

toward the cell body

· Axons –away from the cell body

Figure 7.4a

Neurons

Figure 12.2b

Glial Cells

Anatomy of the Nervous System

Slide 7.2

· Central nervous system (CNS)· Brain

· Spinal cord

· Peripheral nervous system (PNS)· Nerve outside the brain and spinal cord

Central nervous system (CNS)– Brain– Spinal cord

CNS is protected by• Bone • Meninges• CSF

Bone

Meninges

CSF

Spinal cord

CSF ?

LP?

Structure of spinal cord

• Roots dorsal, ventral

• Hornsanterior, posterior, lateral

• Columnsanterior, posterior, lateral

Dorsal

Ventral

WhiteMatter

GrayMatter

CentralCanal

Spinal Cord

Gray Matter

Dorsal

Lateral

Ventral

Horns

vv

• Root dorsal, ventral

• Nerve

• Ramus/Brunchanterior, posterior

Dorsal

Ventral

WhiteMatter

Spinal Cord White Matter

Ascending (Sensory)

Figure 16.1

touch & conscious proprioception

pain & temperature

unconscious proprioception

Descending (motor)

Muscle movement

Muscle balance

Brain