University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

58

Pages:

3
Author:

Mariam A. A.

Nervous system principles Nervous system ● Cells, tissues and organs that control the body’s response to internal and external stimuli ● Consists of the brain, spinal cord, nerves, ganglia and parts of the receptor and effector organs Function ● Receive signals from external stimuli (input) ● Integrate information for meaning ● Effect a response (output) ● Maintain homeostasis Nervous system principles 1. Behaviour is regulated by an input and output sequence 2. Sensory and motor pathways are separate throughout the nervous system 3. Multiple levels of function - putting things together to make an overall picture 4. Organised in parallel and series - Parallel (example) - one pathway spatial awareness, another pathway for the object and they don't intermix - Series - draws from both of the parallel of give you an overall picture 5. Most pathways cross into the opposite side of the brain (contralateral) 6. Excitation and inhibition needs to be regulated because they affect one’s behaviour 7. Symmetry and asymmetry in brain anatomy and function 8. Some functions are very specific to a region while other functions are widely distributed Components Neurons ● Involved in cellular communication ● Have axon ● Transmit electrical signals Glial cells ● No axon ● Provide support for th neurons ● Maintain homeostasis ● More glial cells than neurons Astrocytes - Structural support and nutrients Homeostasis Connect blood vessels to neurons = blood brain barrier (protection for neurons from anything that might escape the blood vessels) Nutrients for neurons and replenishing neurotransmitters Microglia - Mobile and phagocytic Respond to infection Protect neurons from damage Oligodendrocytes - Form myelin sheath (speed up action potential) Only in the CNS Ependymal cells - Lines CNS fluid cavities Produce and circulate cerebrospinal fluid Satellite cells (only in the PNS) - Like the PNS astrocyte Structure and nutrients to neuron Schwann cells (only in the PNS) - Like the PNS oligodendrocyte Produce myelin sheath Cover a single axon only (whereas oligodendrocytes can cover up to 50) Central nervous system ● Grey matter (40%) - Contains neuron cell bodies, dendrites and glial cells ● White matter (60%) - Myelin that surrounds nerve axons (looks white because the myelin is surrounded by fatty tissue) - Spinal cord → white matter is on the outside so it’s easier for the nerves join on the outside and run into the brain The brain is opposite to the spinal cord → info from one part of the grey matter will travel through the white matter to get to the other side (see red star) CNS Protection ● Brain is protected by the skull ● Spinal cord is protected by the vertebral column ● CNS has 3 layers of fibrous tissue called meninges ○ Dura mater (tough outer layer) ○ Arachnoid (middle suspension layer that allows the brain to float) ○ Pia (delicate inner layer which is connected to the brain tissue) ● Divide the brain ○ Dura mater fold in on themselves to create separations of the brain (hemispheres and compartments) ○ Separation of the cortex and cerebellum ○ Dura mater have gaps that have venous sinuses (gap between the dura and bone and fill with deoxygenated blood) - like a vein without walls ○ Stabilises the brain