Introduction to CNS Anatomy Flashcards
What makes up the central nervous system?
Brain, spinal cord, retina, CN II
What makes up the peripheral nervous system?
- Spinal nerves and cranial nerves (except CN II)
- Autonomic nervous system (involuntary): visceral sensory, visceral motor and special sensory fibres
- Somatic nervous system (voluntary): somatic sensory and somatic motor fibres
Which system is fight or flight?
Sympathetic
Which system is rest and digest?
Parasympathetic
What do somatic sensory fibres do?
Transmission of sensory fibres from the skin, skeletal muscles, joints, & tendons to the CNS.
- touch
- pain
- temperature
- proprioception
What do somatic motor fibres do?
Transmission of motor fibres from the CNS to the skin, skeletal muscles, joints, & tendons.
- Controls voluntary actions of skeletal muscle.
Which system are sympathetic and parasympathetic systems a part of?
Autonomic nervous system
What do visceral sensory fibres do?
Transmission of sensory fibres from from smooth muscle, cardiac muscle and glands to the CNS.
What do visceral motor fibres do?
Transmission of motor fibres from the CNS to smooth muscle, cardiac muscle and glands.
- Motor orders to involuntary smooth muscle.
What do special sensory fibres do?
Sensory information related to special senses
What are the two main cell types in the nervous system?
Neurons (nerve cells)
Neuroglia (glial cells)
What parts make up a neuron?
A cell body, an axon and a dendrite
What are the different types of glial cells? (HINT: Oh what A MESS)
Oligodendrocytes - wrap around the axons of CNS neurons to provide electrical insulation called myelin sheaths. This allows the signal to move quickly enough for proper functioning. In many neurodegenerative diseases, the myelin sheaths are damaged.
Astrocytes - provide protection and support to neurons, exchanging nutrients and other important chemicals.
Microglia - like macrophagesin the blood, they surround and digest damaged or invading cells. They are considered the immune cells of the CNS.
Ependymal cells - line the empty cavities called ventricles in the brain and have access to nearby blood vessels. They filter some of the materials out of the vessels to manufacture CSF and then use their cilia to circulate it through the empty ventricles and into the rest of the CNS.
Satellite cells - provide nutrients and protection to neurons in the PNS. A satellite glial cell wraps itself around the neuron’s cell body. The cell body is a rounded section that contains the nucleus and other key organelles common to most somatic cells.
Schwann cells - wrap themselves around the axons of neurons in the PNS. The axon is the long, thin part of the neuron, along which the electrical signal passes. The Schwann cell forms a protective layer called the myelin sheath – this operates like the insulated coating on electrical wiring. Without it, the electrical signal can be disrupted, slowed or stopped altogether.
Which glial cells are in the central nervous system?
Oligodendrocytes
Astrocytes
Microglia
Ependymal cells
Obsessed Aunties Measure Eggs
Which glial cells are in the peripheral nervous system?
Satellite cells
Schwann cells
Describe the sensory (afferent) pathway.
Sensory signals - posterior/dorsal roots - dorsal horn of spinal cord - cerebral cortex - sensory parts of cortex.
Sensory signals: somatic sensory (sensations from somatic tissues), visceral sensory (sensations from organs and vessels), special visceral sensory (e.g. taste)
Describe the motor (efferent) pathway.
Motor signals - motor cortex - ventral horn - anterior/ventral roots - motor destination.
Motor destinations: somatic motor (skeletal muscle), branchiomotor (pharyngeal arch derived muscle), visceral/autonomic motor (organs and vessel)
When do the cranial neuropore and caudal neuropore close?
Cranial - day 25
Caudal - day 27
What supplement prevents 70% of neural tube defects?
Folic acid
What does failure of closing of the cranial neuropore result in?
Anencephaly - absence of a major portion of the brain, skull, and scalp that occurs during embryonic development.
Cranial = defect on head
What does failure of closing of the caudal neuropore result in?
Spina bifida - underdevelopment of lower spinal cord and nerve roots.
Caudal = defect on back
How is a neural tube formed?
The edges of the neural plate start to thicken and lift upward, forming the neural folds. The center of the neural plate remains grounded, allowing a U-shaped neural groove to form. This neural groove sets the boundary between the right and left sides of the embryo. The neural folds pinch in towards the midline of the embryo and fuse together to form the neural tube.
The adult brain develops from 3 primary brain vesicles to 5 secondary brain vesicles. What are these vesicles called?
(3 primary forms 5 secondary)
Prosencephalon forms telencephalon and diencephalon
Mesencephalon forms mesencephalon
Rhombencephalon forms metencephalon and myelencephalon
What part of the brain does the telenecephalon go onto become?
Cerebral hemispheres
What part of the brain does the diencephalon go onto become?
Thalamus/hypothalamus
What part of the brain does the mesencephalon go onto become?
Midbrain
What part of the brain does the metencephalon go onto become?
Cerebellum and pons
What part of the brain does the myelencephalon go onto become?
Medulla
Why is there a flexure between the longitudinal axis of forebrain and longitudinal axis of brainstem and spinal cord?
This flexure develops because of the upright position of humans. It helps the eyes to point forward. Without the flexure, our eyes would point to the ceiling.
What is a gyrus? What is a sulcus?
Gyrus: ridge.
Sulcus: groove.
What does the longitudinal fissure do?
Separate the 2 cerebral hemispheres.
What does the corpus callosum do?
It ensures that the cerebral hemispheres can communicate and send signals to each other.
What do the pre-central and post-central gyrus contain?
Pre-central gyrus - primary motor cortex
Post central gyrus - primary somatosensory cortex
What are the calcarine sulcus and cingulate gyrus?
Calcarine sulcus: separates occipital lobe into lingual gyrus and cuneus.
Cingulate gyrus: processes emotions and regulates behaviour.
What are the functions of the:
Primary motor cortex
Pre-motor cortex
Pre-frontal cortex
Primary auditory cortex
Primary somatosensory cortex
Primary visual cortex
In general, the left and right side of the brain look after the opposite side of the body. However, what are some things which are side specific?
Left: speech, writing, language.
Right: spatial perception, facial recognition.
What do the somatosensory and motor homunculi look like?
What are the basal ganglia?
A collection of subcortical nuclei deep to cerebral hemispheres.
The structures generally included in the basal ganglia are the caudate nucleus, putamen, and globus pallidus in the cerebrum, the substantia nigra in the midbrain, and the subthalamic nucleus in the diencephalon.
What is Broca’s area involved in?
Production/motor planning involved in speech.
A lesion in this area may result in a patient knowing what they want to say but not being able to speak the words.
What is Wernicke’s area involved in?
Understanding/interpreting heard, spoken and written word.
What are association, commisural and projection fibres and what do they connect?
Association fibers connect the various cortical regions within each hemisphere.
Commissural fibers connect the corresponding regions of the two hemispheres.
Projection fibers connect the cortex and lower parts of the brain.
What are the 12 cranial nerves?
OH - Olfactory - I
OH - Optic - II
OH - Oculomotor - III
TO - Trochlear - IV
TOUCH - Trigeminal - V
AND - Abducens - VI
FEEL - Facial -VII
VIRGIN - Vestibulocochlear - VIII
GIRLS’ - Glossopharyngeal - IX
VAGINAS - Vagus - X
AND - Accessory - XI
HYMENS - Hypoglossal - XII
What are the 3 regions of the brainstem?
Midbrain
Pons
Medulla
What connects the two cerebellar hemispheres?
The vermis
How can tonsils on the posterior lobe of the brain compress the medulla?
Tonsils are susceptible to increases in intracranial pressures. This can cause the tonsils to descend/herniate through the foramen magnum and compress the medulla.
What is the Circle of Willis? Which arteries form the circular shape? Draw it out.
Anastomotic system of arteries that supplies the brain.
2 anterior cerebral arteries which are joined together by an anterior communicating artery, and then 2 internal carotid arteries and 2 posterior cerebral arteries joined together by 2 posterior communicating arteries.
Draw out which parts of the brain are supplied by the anterior, middle and posterior cerebral arteries?
What are the functions of the meninges?
- Protect your CNS (central nervous system) from trauma injury to your brain, such as a blow to your head by acting as a shock absorber.
- They anchor your CNS and keep your brain from moving around within your skull.
What are the layers of meninges?
Periosteal layer of Dura
Meningeal layer of Dura
Arachnoid mater
Pia mater
What are the meningeal spaces?
Spaces separating the layers of meninges. You can haemorrhage into/around these layers.
Extradural (above dura)
Subdural (between dura and arachnoid)
Subarachnoid (between arachnoid and pia)
What are the dural venous sinuses? Where is it located?
Normally the 2 layers of dura (periosteal and meningeal) are pressed together, except for where there are dural venous sinuses running between them and separating them.
Blood from the CNS drains into the dural venous sinuses and then into the internal jugular veins.
The meningeal layer of dura mater folds inwards upon itself to form 4 dural reflections. What are they called? What do they do?
- Falx cerebri – projects downwards to separate the right and left cerebral hemispheres.
- Tentorium cerebelli – separates the occipital lobes from the cerebellum. It contains a space anteromedially for passage of the midbrain – the tentorial notch.
- Falx cerebelli – separates the right and left cerebellar hemispheres.
- Diaphagma sellae – covers the hypophysial fossa of the sphenoid bone. It contains a small opening for passage of the stalk of the pituitary gland.
Dural reflections help to stabilise and support CNS structures.
How many dural venous sinuses are there? What are they called? Where do they drain?
There are 11 dural venous sinuses.
Sphenoparietal sinuses - drains into cavernous sinuses
Cavernous sinuses - drains into superior and inferior petrosal sinuses
Superior sagittal sinus - typically becomes right transverse sinus or confluence of sinuses
Inferior sagittal sinus - drains into straight sinus
Straight sinus - typically becomes left transverse sinus or confluence of sinuses
Occipital sinus - drains into confluence of sinuses
Confluence of sinuses - drains into right and left transverse sinuses
Superior petrosal sinus - drains into transverse sinuses
Transverse sinuses - drains into sigmoid sinus
Inferior petrosal sinus - drains into internal jugular vein
Sigmoid sinuses - drains into internal jugular vein
What can obstruction of the ventricular system in the brain result in?
It can restrict the flow of CSF and lead to hydrocephalus - a build up of CSF in ventricular spaces
What is the ventricular system of the brain? What makes up the ventricular system?
The ventricular system is responsible for the production, transport and removal of cerebrospinal fluid, which bathes the central nervous system.
2 lateral ventricles, the third ventricle, the cerebral aqueduct, and the fourth ventricle.
The lateral ventricles drain into a centrally located third ventricle which drains into the fourth ventricle which drains into the central canal.
