The Nervous System

1
The Nervous System

• Central Nervous System
• (CNS)

2
THE CENTRAL NERVOUS SYSTEM(BRAIN SPINAL CORD)

• The Brain
• The brain is one of the largest organs in the
  body
• Male brain is about 1600gm
• Female brain is about 1450gm
• (equivalent in terms of size/body wt)

3
The Brain

• The brain has 4 main areas
• Brain stem
• Diencephalon
• Cerebellum
• Cerebrum

4
The Brain Stem
5
1. The Brain Stem

• Consists of
• Medulla (Oblongata)
• connects brain and spinal cord
• contains reticular formation- responsible for
  arousal and consciousness
• filters out extraneous sensory
• input

6
The Brainstem

• Medulla cont.
• contains autonomic reflex centers essential for
  survival
• cardiac centre
• vasomotor centre
• respiratory centre

7
The Brainstem

• Pons (bridge)
• links cerebrum and medulla also brainstem
  cerebellum
• contains some respiratory centres
• Midbrain
• contains ascending descending tracts
• mediates auditory visual reflexes

8
2. Diencephalon

• consists of
• Thalamus
• principal relay station for sensory impulses

9
Diencephalon

• Hypothalamus
• control of homeostasis
• integration centre for Autonomic
• nervous System
• centre for emotional responses

10
Diencephalon

• Epithalamus
• contains Pineal gland - involved
• in Circadian rhythms (sleep/wake cycles)
• control of sexual functioning

11
3. Cerebellum

• Paired lobes posterior to brainstem
• Coordinates body movements, posture balance

12
4. The Cerebrum

• Enables awareness of self, sensation,
  communication, memory, understanding and movement.

13
The Cerebrum

• Structure
• 2 hemispheres divided by the longitudinal fissure
• further subdivided into 5 lobes
• frontal
• parietal
• temporal
• occipital
• insula

14
The Cerebrum

• consists of
• cortex (grey matter) forms outer covering,
  characterised by folds (gyri) and grooves (sulci)
  
• white matter internal structure

15
(No Transcript)
16
The Cerebrum

• Functionally
• sensory areas conscious perception of various
  sensations
• motor areas control of voluntary movements
• association areas integration of diverse
  information

17
Motor Areas of cerebral cortex

• 4 AREAS (in frontal lobe)
• (1)Primary motor cortex
• control of skeletal muscles
• (2)Pre-motor cortex
• motor skill patterns
• (3)Brocas area
• speech
• (4) Frontal eye field.
• eyeball movements

18
Motor Areas of cerebral cortex
19
Cerebral Cortex

• Primary (somatic) motor cortex
• Located in the pre-central gyrus.
• Allows us to control voluntary movements of our
  skeletal muscles.
• The entire body is mapped in the primary motor
  cortex (called a homunculus)

20
Primary Motor Cortex
21
Sensory areas of the cerebral cortex

• Several Areas
• 1)Primary somatosensory cortex (post central
  gyrus)
• 2)Somatosensory association area
• 3)Primary sensory and association areas for each
  of the special senses
• Function is conscious awareness of sensation.

22
Sensory areas of the cerebral cortex
23
Sensory areas of the cerebral cortex

• 1. Primary somatosensory cortex
• Located in the post-central gyrus.
• Receives info from somatic receptors in the skin
  and proprioceptors in muscles.
• Identifies body region stimulated (spatial
  discrimination or localisation)
• As with the primary motor cortex it is mapped.

24
Primary Somatosensory Cortex
25
Association areas

• Association areas communicate with other
  association areas to analyze and recognize
  sensory inputs in light of past experience.

26
Association areas
27
The Brain

• Other structures
• ventricles
• cerebrospinal fluid
• meninges
• Blood brain barrier
• cerebral blood supply Circle of Willis

28
Ventricles

• Fluid filled spaces in the brain
• Allow for production circulation of CSF
• Allow some compression
• Allow for brain growth

29
Cerebrospinal fluid (CFS)

• Watery substance originating from special
  capillary networks in the ventricles (choroid
  plesuses)
• Rich in glucose provides nutrients
• Body produces 500ml/day.

30
Hydrocephalus
31
Meninges

• Function cover protect the CNS Blood vessels
  and store (CSF).
• 3 layers
• Dura mater tough outer layer (C.T)
• Arachnoid layer web like extensions- houses
  major vessels
• Pia Mater closely hugs the brain

32
Meninges
33
Blood Brain Barrier

• Capillary Junction in brain. Made up of
  endothelial cells. Very selective re. what
  substances pass through to brain.

34
Cerebral Circulation

• The Circle of Willis
• Consists of
• A specialised set of arteries that circles the
  brain stem to ensure that blood flow is always
  maintained
• A form of inbuilt bypass (arterial anastamosis)

35
The Spinal Cord

• extends from foramen magnum to L2
• gives rise to 31 pairs of spinal nerves
• central H-shaped core of grey matter
• - surrounded by white matter

36
The Spinal Cord

• Anatomical Features
• conus medullaris
• cauda equina
• filum terminale
• cervical lumbar enlargements
• (for limb nerve supply)
• dorsal and ventral horns of grey matter

37
The Spinal Cord
38
Gray Matter Organization

• Dorsal half sensory roots.
• Ventral half motor roots.
• Dorsal and ventral roots fuse laterally to form
  spinal nerves.

39
(No Transcript)
40
The Spinal Cord

• Functions
• sensory motor innervation to
• entire body below the head
• two-way communication pathway between body and
  head
• major reflex centre

41

• Sensory and Motor Pathways
• Sensory (ascending) pathways from periphery to
  brain
• Spinocerebellar proprioception
• Dorsal Column fine touch proprioception
• Spinothalamic course touch, pain, temperature

42
Sensory Motor pathways

• Motor (descending) pathways from brain to
  periphery
• Corticospinal (Pyramidal) skilled, conscious
  movements
• Extrapyramidal subconscious or coarse movements