Cells and Tissues of the Nervous System Flashcards
Describe the divisions of the nervous system
CNS - brain and spinal cord and PNS - cranial and spinal nerves
PNS - sensory and motor division
Motor - somatic motor and autonomic (sympathetic and parasympathetic)
What are the 2 types of cells in nervous system?
Neurons and Glial cells
Describe neuron cells
Structural and functional unit
Excitable cells
Impulses carried as action potentials
High metabolic rate (a lot of glucose used, long living and amitotic
Describe glial cells
Non-excitable supporting cells
Much smaller than neurons
What is a typical neuron structure?
Multiple dendrites and one axon
Impulses transmit by action potential travel in one direction from cell body to synaptic terminal
Describe structures in neurons
Nucleus is loose chromatin and prominent
Mitochondria, rER (nissl bodies) and diffuse golgi apparatus
Cytoplasm in the cell body is perikaryon and axon is axoplasm
What are the 3 types of neurons?
Multipolar, bipolar and psuedounipolar
What neurons are multipolar?
Interneurons
Motor neurons
What neurons are bipolar?
Olfactory mucosa
Retinal nerve fibres
What neurons are pseudounipolar?
Sensory neurons
Where does cell body of multipolar neurons lie?
Within brain and spinal cord
What is the function of a myelin sheath?
Increase conduction speed in axons by saltatory conduction
Is formed by schwann cells in PNS and oligodendrocytes in CNS
What happens to myelin sheath in multiple sclerosis?
Patchy loss/scarring of myelin sheath (demyelination) which causes abnormal nerve conduction on affected axons
What is the difference between grey and white matter?
White - myelinated axons
Grey - neuronal cell bodies
What are ascending and descending tracts?
Ascending - tracts are sensory and go up to spinal cord
Descending - spinal cord to periphery
Tracts are bindles of axons carrying specific info into specific part of brain or periphery
What is the difference between dorsal and ventral root?
Dorsal - sensory
Ventral - motor
What is a nucleus in the hemisphere?
Collection of grey matter inside cerebral hemisphere
What is a collection of neuronal cell bodies in the CNS called?
Ganglion
What are some different types of glial cells?
In CNS - astrocytes, oligodendrocytes, phagocytes and ependymal cells
In PNS - Schwann cells and satellite cells
What are astrocytes?
Have end feet which surround synapses and capillaries
Help in K+ buffering
What are phagocytes function?
Phagocytosis and scar tissue formation
What is the function of ependymal cells?
Line ventricles and central canal of spinal cord
What is the function of satellite cells?
Surround neural cell bodies
Describe the blood brain barrier
Protective mechanism that helps maintain a stable environment for brain and prevents harmful amino acids and ion present in bloodstream and blood cells entering the brain
What are the layers of the blood brain barrier?
Endothelium with tight junctions
Thick basal lamina
Foot processes of astrocytes
What is allowed in and out of blood brain barrier?
Lipid soluble molecules, O2 and H2O can diffuse
Water soluble molecules (glucose and aa) are pump mediated
Where is the BBB not present?
Centriventricular organs
Parts of hypothalamus, posterior pituitary
Describe the basic topography of the brain
Cerebrum, Cerebellum, Brainstem and diencephalon
Brainstem - midbrain, pons and medulla. Has vital centres and pathway of fibre tracts
What can be seen on dura mater covering brain?
Emissary vein in superior sagittal sinus
Branches of middle meningeal vasculature
What are the folds of dura mater?
Falx cerebri - separates hemisphere
Tentorium cerebelli - separates cerebellum hemispheres
What are the ventricles of the brain?
Lateral ventricle - C shaped and lie in cerebral hemispheres
3rd ventricle - connected by interventricular foramen, in cavity within diencephalon
Cerebral aqueduct in midbrain
4th ventricle in hindbrain
Where is the 4th ventricle?
Between pons and medulla (in front) and cerebellum at back
Describe the meninges of the CNS
Dura, arachnoid and pia mater
Pia mater is vascularised and dips into folds
Subarachnoid space contains CSF
Subdural space is potential space which is traversed by blood vessels penetrating into CNS
Describe the CSF
Fluid inside cavity of brain (the ventricles) and central canal of spinal cord
Responsible for maintenance of intracranial pressure
Between pia and arachnoid mater
Where is CSF present?
Inside ventricles
Between pia and arachnoid space
Where is CSF formed?
By choroid plexus in each ventricle
Where is CSF absorbed?
By arachnoid villi into sagittal sinus (venous channel in brain)
How does CSF circulate?
Leaves ventricular system through 3 holes at roof of 4th ventricle
Circulates through subarachnoid space
Reabsorbed into superior sagittal sinus through arachnoid villi
