05/31/2023 Notes Flashcards
What are nerves?
A cable-like bundle of parallel axons that can be seen with the naked eye
What are sensory nerves?
Nerves that convey sensory information to the CNS; all axons travel unidirectionally
What are motor nerves?
Nerves that convey motor information to the muscles/glands; all axons travel unidirectionally
What are mixed nerves?
A combination of sensory and motor nerves that travel in opposing directions
When does nervous tissue begin to develop?
3rd week of embryo development
How does nervous tissue develop?
Formation of the neural groove which eventually fuses into the neural tube; the opening near the head (cranial) forms the brain while the opening towards the buttocks (caudal) forms the spinal cord
Is brain size correlated with intelligence? What determines intelligence?
No, active synapses determine intelligence
What is the typical size of the human brain?
1300 cc; 3 lbs
What are the four major regions of the brain?
Cerebrum, cerebellum, brainstem, and diencephalon
How many lobes are located in each hemisphere of the cerebrum?
5
What are gyri?
Folds located on the surface of the brain
What are sulci?
Shallow depressions located between gyri
What 5 regions of the brain will have developed by the 5th week of development?
Telencephalon (headend), diencephalon (through the brain), mesencephalon (midbrain), metencephalon (afterbrain), and myelencephalon (medulla and brain)
What does the telencephalon form?
Cerebrum
What brain region forms the hypothalamus, epithalamus, and thalamus?
Diencephalon
What is the mesencephalon?
Region that forms a short section of the brainstem between the diencephalon and pons
What brain region forms the pons and cerebellum?
Metencephalon
What does the myelencephalon form?
Medulla oblongata
Why does the telencephalon folds its surface and develops sulci and gyri?
Determines the boundaries of the brain’s cavities and are needed to fit the entire brain in the cranial cavity
What does the fetal brain resemble at birth?
An adult brain
What two tissues exist in the brain and spinal cord?
White and gray matter
What composes gray matter?
Motor neurons, dendrites, branching axon terminals, and unmyelinated neurons
What gives white matter a white color?
Myelin in myelinated neurons
What is the cortex?
Outer, superficial layer of gray matter that covers most of the adult brain
What is the medulla?
An inner layer of white matter that is found deep to the cortex
Sudden decelerations can cause the gray and white matter to do what?
Shear at the intersurface
In the spinal cord, the arrangement of gray and white matter is _____.
Reversed
What three things support and protect the delicate brain?
Cranium, meninges, and cerebrospinal fluid
What do the three layers of the meninges do?
Separates the soft tissue of the brain from the cranium, enclose and protect blood vessels that supply the brain, as well as contain and circulate CSF
What are the three layers of the meninges starting from the innermost layer?
Pia Mater, Arachnoid Mater, and Dura Mater
What is the pia mater?
The innermost layer of the meninges that is highly vascularized and adheres tightly to the brain and follows the contour of the brain
What is the arachnoid mater?
The middle layer of the meninges that contains a delicate web of elastic fibers and collagen that resemble a spiders web
What is the subarachnoid space?
Extensions of the archnoid travel through the subarachnoid space to reach the pia mater
What is the subdural space?
A potential space that exists between the arachnoid mater and dura mater
What is the dura mater?
Outermost layer of the meninges that is composed of the meningeal layer and periosteal layer
Where are the meningeal and periosteal layers not connected?
Dural venous spaces
Where do the dural venous spaces brain blood?
From the brain to internal jugular veins
What is the epidural space? (brain)
A potential space that separates the dura mater from the skull and contains blood vessels that nourish the meninges and bones of the cranium
How does the epidural space fill up with fluid/blood?
When a person succumbs to disease or trauma
What are cranial dural septa?
Spots where the meningeal layer of the dura mater extends into the cranial cavity through flat partitions (septa) that separate parts of the brain and provides stabilization and support for the brain
What are the four cranial dural septa?
Falx cerebri, tentorium cerebelli, falx cerebelli, and the diaphragma sellae
What does the falx cerebri do?
Extension of the dura mater that extends into the longitudinal fissure between the left and right cerebral hemispheres
What are the anterior and posterior attachments of the falx cerebri?
Anterior: christa gali
Posterior: superior portion of the tentorium cerebelli
What is the tentorium cerebelli?
Separates the. occipital and temporal lobes from the cerebellum; contains the tentorial notch and has dural venous veins
What is the tentorial notch?
Small gap that allows the passage of the brainstem
What is the falx cerebelli?
Separation between the left and right cerebelli hemispheres with a tiny dural venous vein
What is the diaphragma sellae?
Forms a roof over the sella turcica and creates a small opening that allows the passage of the stalk connecting the pituitary gland to the hypothalamus
What are the four brain ventricles?
Right lateral ventricle, left lateral ventricle, third ventricle, and fourth ventricle
Where are brain ventricles derived from?
Lumen of the neural tube
What separates the lateral ventricles?
Septum Pellucidum
Where are the brain ventricles located?
Lateral ventricles (cerebrum), third ventricle (diencephalon), fourth ventricle (between the pons and cerebellum)
What is cerebrospinal fluid (CSF)?
A clear, colorless fluid that circulates within the ventricles and subarachnoid spaces that bathes exposed surfaces of the CNS
What are the functions of CSF?
Provide buoyancy to reduce weight of the brain by 95%, protects the brain from sudden movements, and provides environmental stability by transporting nutrients and removing wastes
Why does CSF removal result in headaches?
Loss of buoyancy increases the weight of the brain
Where is waste from CSF and excess CSF put?
Secreted into venous circulation
What forms CSF?
Choroid plexus in each brain ventricle
How much CSF is produced each day?
500 mL
How much CSF is in the subarachnoid space in a healthy individual?
100-160 mL
What are arachnoid villi?
Fingerlike extensions of the arachnoid mater that project through the dura mater and into dural venous sinuses
Summarize the pathway of CSF.
Produced by choroid plexus in the ventricles –> flows through brain ventricles and enters the subarachnoid space and central canal –> drains back into the blood by arachnoid villi that empty into dural venous sinuses
What protects the nervous tissue from blood circulation?
Blood-brain barrier
Where do astrocytes NOT reduce capillary permeability? (3 areas)
Choroid plexus - CSF
Hypothalamus AND Pineal Gland - Hormones
Selective permeability of the BBB does what?
Prevent hazardous material from diffusing into nervous tissue (usually lipid-soluable compounds are able to diffuse); This may make medications difficult to administer!
