Explore the intricate structure of the CNS, including the brain and spinal cord. Gain insights into the major regions of the brain—cerebrum, cerebellum, and brainstem—and their respective functions.
Organisation of the central nervous system
11 August 2020 10:14
What is the Central Nervous System?
• The human central nervous system contains the brain and spinal cord.
• The peripheral nervous system consists of: sensory neurons, clusters of neurons called ganglia and nerves connecting them to each other and to the CNS.
Central Nervous System:
3 Parts of the Brain:
1) Cerebrum (top part)
2) Cerebral Hemispheres (Left and Right)
3) Brainstem (connects the cerebrum to the spinal cord)
The Brainstem composed of 3 subparts: (Midbrain, Pons, Medulla oblongata)
Cerebellum located on the front, near the brainstem.
The names of the brain structures are developed from the names of the embryo from which they originate. For example:
○ Forebrain (consists of 3 major parts: cerebrum, thalamus, hypothalamus, pituitary gland, limbic system and olfactory bulb) (Prosencephalon)
○ Midbrain (consists of various cranial nerve nuclei, tectum etc.)(Mesencephalon)
○ Hindbrain (consists of brainstem made of medulla, pons, cerebellum, cranial nerves) (Rhombencephalon)
○ Spinal cord
Peripheral Nervous System:
The peripheral nervous system refers to parts of the nervous system outside the brain and spinal cord. It includes:
○ 12 cranial nerves (primarily comes out of the brain/skull)
○ 31 spinal nerves and their roots and branches (comes from the spine and pass through the CNS and PNS)
○ 43 pairs of peripheral nerves (motor and sensory)
○ Neuromuscular junctions
The main function of the PNS is to connect the CNS to the limbs and organs, essentially serving as a relay between the brain and spinal cord and the rest of the body.
Neurons:
Afferent neurons- Axons carry information to the Central Nervous System from the peripheral.
Efferent neurons- Axons carry information from the Central nervous System to the peripheral.
○ Dendrites- Receives signals from other neurons
○ Cell body/ Soma - contains the nucleus and other structures common to living cells.
○ Axon - fibre which carries action potentials/ nerve impulses away from the cell body.
○ Myelin sheath - insulating layer made up of protein and fatty substances. Allows electrical impulses to transmit quickly and efficiently.
○ Node of Ranvier (saltatory conduction) - periodic gap in the myelin sheath on the axon of certain neurons that serves to facilitate the rapid conduction of nerve impulses
○ Schwann cell - myelinate the axons of the PNS.
○ Axon terminal - Conducts electrical signals to nerve synapse which then moves across synapse to another axon via neurotransmitters.
Central Nervous System Page 1
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