Lecture 15 - CNS 1 Flashcards
What are the two major parts of the nervous system?
- Central nervous system (CNS)
o Brain and spinal cord - Peripheral nervous system (PNS)
o Afferent (carries signal TO the CNS)
Sensory neurons
o Efferent (carries signal FROM the CNS)
Somatic (motor neuron to skeletal muscle)
Autonomic (innervates smooth muscle, cardiac muscle and glands) - Sympathetic and parasympathetic
- Rest and digest
- Fight or flight
What is the function of the brain in the CNS?
- Receives 20% of cardiac output
o Dependent on oxygen for energy
o Dependent on glucose for function
Precursors for neurotransmitter synthesis
Generation of action potentials - Blood flow stops brain
o Brain function stops in seconds
o Neurons die in minutes - Limited regenerative capacity
What is the function of the spinal cord in the CNS
- Primary pathway for communication between periphery and the brain
- Connected to brain through brain stem
What are the common CNS injuries?
- Prion disease: fatal familial insomnia. Selective loss of thalamic nuclei causing hormone irregularities. Disrupts sleep-wake cycles
- Spinal cord injury (SCI): SCIs occur when the spinal cord is damaged, either through trauma or disease. This can result in loss of sensation and movement below the site of the injury
- Multiple sclerosis (MS): MS is a chronic autoimmune disease that affects the CNS. It causes inflammation and damage to the myelin sheath, which is the protective covering around nerve fibres in the brain and spinal cord. This can result in a range of neurological symptoms, including weakness, numbness, and difficulty with balance and coordination.
- Parkinson’s disease: Parkinson’s disease is a progressive neurological disorder that affects movement. It occurs when the neurons in the brain that produce dopamine, a neurotransmitter that helps control movement, are damaged or destroyed. Selective neuronal loss in substantia nigra-affecting motor function
- Alzheimer’s disease: Alzheimer’s disease is a progressive neurological disorder that affects memory, thinking, and behaviour. It occurs when abnormal protein deposits form in the brain and cause damage to brain cells. Involves selective loss of neurons in the hippocampus, frontal, parietal, temporal lobes.
What are the components of the brain?
- Grey matter
o Cell bodies
o Glia
o Blood vessels - White matter
o Myelinated axons
o Glia
o Blood vessels
What is the structure and function of neurons?
- ORIGIN: Neuroectoderm
- Terminally differentiated
o Permanent tissue
o Cells cannot divide - Receives and transmits electrical impulses
- Made up of the neuronal cell body, axon and dendrites
- Cell body
o Nucleus
o Nissl substance (ER)
Specialised structure found in the cell bodies of neurons in the nervous system. It is made up of ribosomes and endoplasmic reticulum, which are involved in protein synthesis.
o Neurofibrils - Dendrites RECEIVE
- Axons TRANSMIT
What are the types of neurons?
- Sensory
- Autonomic
- Motor
- Interneurons
What are the types of arrangements that neurons can form?
- Commissural tracts: axons that connect the two hemispheres of the brain
o Allows for interhemispheric communication
o Most prominent commissural tract in the brain is the corpus callosum. Corpus callosum: connects the left and right hemispheres of the brain. - Association tracts: connects regions within the same hemisphere
o Can be short-range or long-range
o Short-range association fibres connect adjacent cortical areas within a single lobe, while long-range association fibres connect more distant cortical areas in different lobes. - Projection tracts: connects each region to other parts of the brain or spinal cord
o Allows for communication between the brain and the rest of the body
o These tracts are responsible for carrying motor signals from the brain to the spinal cord and sensory signals from the spinal cord to the brain.
o They also play a role in regulating reflexes and other involuntary movements.
What is the difference between nuclei and ganglia?
**Ganglia = neurons with a common function
***Nuclei = neurons with a common target
How does the skull and vertebral column protect the brain from injury?
o Protects brain from mechanical forces
The skull’s tough and rigid structure acts as a barrier, shielding the brain from external physical trauma and absorbing impact forces that could otherwise damage the delicate neural tissue.
The vertebral column’s bony structure provides structural support and helps to distribute the weight of the upper body, while also allowing for movement and flexibility.
Tissues in the vertebral column help to stabilize the bones and absorb shock during physical activity, reducing the risk of injury to the brain and spinal cord.
How do the meninges protect the brain from injury?
Helps to cushion and protect the brain
o Dura mater: fused with skull and restricts brain movement
o Arachnoid mater: CSF and blood vessels
o Pia mater: adheres to surfaces of the brain + connected to choroid plexuses (ventricles)
How does the CSF protect the brain from injury?
o Formed by ependymal cells of the choroid plexus of ventricle cavities
o Enters subarachnoid space, flows between meningeal layers of brains and spinal cord, reabsorbed into the blood
o Shock-absorbing
o Contributes to interstitial fluid composition
o Removes excess fluid in the CNS – occurring between pia mater and blood vessels
How does the blood brain barrier, glial cells and neural plasticity help protect the brain from injury?
- Blood brain barrier (BBB)
o Prevents harmful substances from entering the brain - Glia cells
o Specialised cells that provide support and protect to the neurons. They help repair damage and remove harmful substances from the brain - Neural plasticity
o The brain has the ability to reorganise and adapt in response to injury, allowing it to compensate for damage and continue functioning
What is the blood brain barrier and what is it made of and their roles?
- Endothelial cells:
o Unlike other blood vessels in the body, the endothelial cells in the BBB are tightly packed together and are connected by specialized junctions that prevent most substances from passing through. - Tight junctions
- Basement membrane:
o The basement membrane is composed of several types of proteins, including laminin, collagen, and fibronectin. These proteins help to provide structural support and stability to the endothelial cells, which in turn helps to prevent the passage of harmful substances into the brain. - Pericytes
o Adjacent to endothelial cells, share a common basement membrane
o Contributes to microvascular stability
o Releases growth factors + angiogenic molecules
Microvascular permeability, remodelling, angiogenesis
o Part of the smooth muscle cell lineage
Contractile properties allow for blood flow to be regulated - Astrocytes
- Microglia
What are the roles of the BBB?
- Maintains chemical composition of the interstitial space
- Limits entry of plasma components, RBC and leukocytes
- Precludes free exchange of solutes
- Allows diffusion of small lipid molecules
- Regulates active transport and carrier-mediated transport
- Protects brain from:
o Foreign substances
o Physiological substances in the systemic circulation
o Drastic environmental fluctuations - Required for the function of
o Neural circuits
o Synaptic transmission
o Synaptic remodelling
o Angiogenesis
o Neurogenesis
If BBB is compromised (due to pathology) it generates neurotoxic products
