Download CNS

Central Nervous System
CNS
• Communication and control centre of body
• Brain and spinal cord
Nerve Cells
• Neuron- basic structural and functional unit of
nervous system
• Vary in size and shape
• All consist of dendrite, cell body and axon
CNS- Cell Body
• Contains nucleus and cytoplasm
• Cytoplasm similar to other cells
CNS- Dendrites
• Short extensions of cytoplasm
• Carry nerve impulse INTO cell body
CNS- Axon
•
•
•
•
Long extension from cell body
Usually carry impulse away from cell body
Length highly varied
Most myelinated- covered by fatty material
called myelin
CNS
• Interneurons- brain and spinal cord
• Many branches able to send and receive
messages from adjacent neurons
• Grey Matter- nerve cell bodies and
unmyelinated fibres
• White matter- myelinated fibres
Generalised Neuron
Protecting the CNS
• Bone
• Meninges
• CSF- protection, support and trasnport
Brain- Cerebrum
• Biggest part of brain
• Cerebral cortex- Outer surface of grey matter,
2- 4 mm thick
• Below cortex is basal ganglia
• Right and left hemisphere
• Highly convoluted
Brain- Cerebrum
Brain- Cerebrum
• 4 lobes- frontal, temporal, occipital and
parietal
Brain- Cerebrum
• Tract- bundles of nerve fibers
• Connect various areas of cortex within the
same hemisphere
• Carry impulses between the left and right
hemisphere
• Connect cortex to other parts of brain or
spinal cord
Brain- Cerebrum: Function
• Cortex- thinking, reasoning, learning, memory,
intelligence, sense of responsible, perception
of senses, initiation and control of voluntary
muscle contractions.
Brain- Cerebrum: Function
• Sensory- interpret impulses from receptors
• Motor- control muscular movement
• Association- intellectual and emotional areas
Brain- Cerebellum
•
•
•
•
•
Under rear part of cerebrum
2nd largest part of brain
Folded into parallel ridges
Outer- grey
Inner- white- branches to all parts of
cerebellum
Brain- Cerebellum: Function
• Posture, balance, coordination
• Receives info from inner ear and stretch
receptors in skeletal muscles
• Unconsciously controls us- jerky without it
Hypothalamus
• Middle of brain
• Mostly concerned with homoestasis
Brain- Hypothalamus: Function
• Regulation of
– ANS- HR, BP, secretion of digestive juices,
alimentary canal, pupil dialation
– Body temp
– Food and water intake
– Patterns of walking and sleeping
– Conc urinary bladder
– Emotional responses
– HORMONES!!
Brain- Medulla Oblongata
• Continuation of spinal cord
• 3cm long
• Extends just above point where spinal cord
enters scull
• ‘Highway for nerves’
Brain- Medulla Oblongata: function
•
•
•
•
•
Cardiac centre
Respiratory centre
Vasomotor center
Swallowing, sneezing, coughing and vomiting
Controlled by higher centers in brain
Spinal Cord
• Roughly cylindrical
• Foramen magnum to L2
• Heavily protected
– Vertebral canal
– Meningies
• Outer layer not connected to bone rather space filled
with fat, connective tissue and blood serving as
padding for when spine is bent
Spinal Cord
• Grey and white matter opposite configuration
to brain
Spinal Cord
• Central Canal- CSF
• Ascending and Descending Tracts
– Bundles of myelinated nerve fibre
Structure
Function
Cerebral cortex
Higher order functions such as thinking,
reasoning, memory, learning, conscious
awareness of surroundings
Cerebellum
Coordination of fine contraction so
muscles resulting in smooth movements
and the maintenance of posture and
balance
Hypothalamus
Homeostasis. Regulation of hear, digestive
system, appetite, thirst, metabolism, body
temp, response to fear or anger
Medulla oblongata
Under influence of the hypothalamus
regulates the hear, breathing and
diameter of blood vessels
Spinal Cord
Provides a pathway for communication
between muscles and gland and the
brain. Integration of automatic, protective
reflexes
Control of Movement
• Cerebral Cortex
– Motor Association Area of Brain initiates intention
to move
– Neurons make up program for sequence and
intensity of contractions
– Program then sent to Primary motor area (primary
motor cortex)
– Impulses then sent to lower centres in brain and
spinal cord- result being contraction
Motor Homunculus
Homunculus
“A diagram of the body that shows the relative
size of parts of the cortex devoted to control
of different muscles.”
Cross overs
Cerebellum
• Receive nerve impulses from cerebrum
through upper motor neurons
• Also receives information from eyes, ears and
stretch receptors
• Smoothes contractions
• Learning of motor skills
• Maintain Balance