Download Organization of NS and the neuron File

The Central Nervous System
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The structural and functional centre for entire nervous system
Consists of the brain and spinal cord
Made up of:
1. Grey Matter (mostly cell bodies, dendrites and short unmyelinated axons).
Found on outside areas of brain and H-shaped part of spinal cord
2. White Matter (myelinated axons)
Found in outer area of spinal cord and inner regions of brain
The Spinal Cord
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A column of nerve tissue that extends out of skull and downward through a canal within
a backbone
Vital communication link between brain and PNS
Primary reflex centre
Protected by vertebrae, meninges and cerebrospinal fluid
Sensory nerves enter spinal cord via Dorsal root and motor nerves leave through ventral
root
The Brain
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Maintains homeostasis; centre for intelligence, consciousness and emotions
Protected by:
1. The skull
2. Meninges (3-layers of connective tissue)
3. Cerebrospinal fluid (located b/w middle and inner layers of meninges; acts as a
cushion as well as nourishes the brain)
Meningitis is caused by bacterial or viral infection of outer membrane. Symptoms include
fever, vomiting, intense headache, stiff neck and possible rash. Left untreated can cause
death. Meningitis is diagnosed by sampling the cerebrospinal fluid.
The Brain
(made up of 3 regions)
forebrain
midbrain
hindbrain
FOREBRAIN
Region
Cerebrum
Thalamus
Hypothalamus
Olfactory
Bulbs
Info/ Function
 Largest part of forebrain
 Coordinates sensory and motor functions
 Memory, abstract thought, reasoning, personality, intellect
 Divided into left(verbal, logic, mathematical skills) and
right(visual/spatial awareness- creativity) hemispheres
 2 hemispheres connected by a nerve tract called corpus
callosum
Surface of cerebrum (outer layer) is known as cerebral cortex. It is
made of grey matter and contains many folds [called fissures]
(increases S.A.)
Each hemisphere is divided into 4 lobes:
a. Frontal Lobe
Motor areas control movement of voluntary muscles
association areas are linked to intellectual activities and
personality
b. Temporal
sensory: vision and hearing
Association areas linked to memory and interpretation
of sensory info
c. Parietal
sensory: touch and temperature
 Association areas linked to emotions and interpreting
speech
d. Occipital
sensory: vision
association areas interpret visual info
 Relay station for sensory impulses to cerebrum;
coordinating station for sensory signals
 Helps maintain body’s internal equilibrium
 Coordinates nerve and hormone functions
 Processes info about smell
Hindbrain
Cerebellum
Pons
Medulla Oblongata
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Unconscious coordination of
movement, balance and muscle tone
‘bridge’
Relay centre b/w cerebrum and both
halves of cerebellum
Connects forebrain and spinal cord
Connects brain and spinal cord
Connection b/w PNS and CNS
Controls involuntary muscle action
Coordinating centre for autonomic
system (breathing, heart rate)
Midbrain
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Relay centre for some ear and eye reflexes
Relays visual and auditory info b/w hindbrain and forebrain
The Peripheral Nervous System
2 divisions: sensory-somatic and autonomic
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Sensory-Somatic System
Brings info about external environment to CNS and sends info back to skeletal muscles
Voluntary
Composed of 12 cranial nerve and 31 pairs of spinal nerves
2. Autonomic Nervous System
 Involuntary control of smooth muscle, cardiac muscle, internal organs and glands
 Brings info about body’s internal environment to CNS and carries signals back to
regulate internal environment
The ANS uses 2 groups of motor neurons to stimulate target effectors
a. Preganglionic neurons (CNS  ganglion)
b. Postganglionic neurons (ganglion  target organ, muscle, gland)
Autonomic System further divides into
1. Sympathetic nervous system
2. Parasympathetic nervous system
Sympathetic
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Prepares body for stress, ‘fight or flight’ (increase heart rate, inhibit digestion, release of
adrenaline)
Nerves originate from middle of spinal cord
Short preganglionic nerves (release acetylcholine)
Longer postganglionic nerves (release norephinephrine)
Parasympathetic
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brings back body to a normal state (slows heart rate, promotes digestion, BP decreases)
nerves originate from lower back(tailbone) and brain
long preganglionic nerves (release acetylcholine)
shorter postganglionic nerves(release acetylcholine and nitric oxide)
IMPORTANT CRANIAL Nerve: vagus (wandering) nerve  regulates many internal
organs