Organization of the CNS Flashcards
What happens in the 3rd, 4th, and 6th week of development in the human brain?
3rd week: brain starts as a neural tube
4th week: Anterior portion of neural tube begins to specialize into forebrain, midbrain and hindbrain, and spinal cord.
6th week: forebrain specializes into cerebrum and diencephalon and hindbrain specializes into pons and cerebellum, and medulla oblongata. Spinal cord and midbrain keep their shape.
What are brain ventricles?
Fluid filled cavities lined by ependymal cells that were remnants of the hollow tube from which the brain developed. Includes the two lateral ventricles and two descending ventricles.
What is the central canal?
Hollow tube in spinal cord that is continuous with ventricles and lined with ependymal cells.
What is the difference between white and gray matter?
White matter: myelinated axons that make up a large portion of the brain
Gray matter: unmyelinated somas, axon terminals and dendrites clustered into nuclei (CNS)/ganglia (PNS)/cerebral cortex (surface)
What protects the CNS?
- Bone: skull and vertebral column
- Meninges: three protective and nourishing membranes
- Cerebrospinal fluid (CSF)
- Blood brain barrier
What are the three layers of the meninges?
- Dura mater: thickest and intimately associated with veins and sinuses that drain blood from the brain
- Archanoid membrane: loosely tied to inner membrane and has a villus that projects into the sinus of the dura mater
- Pia mater: soft and delicate membrane that is intimately associated with the surface of the brain and spinal cord and are associated with arteries that supply blood to the brain.
What is meningitis?
Contagious bacterial, viral, or fungal infection of the meninges that cases swelling and pressure on the brain.
What are the three types of bleeding that traumatic head injures may cause?
- Epidural bleeding (between skull and dura)
- Subdural bleeding (between dura and arachnoid)
- Subarachnoid bleeding (between arachnoid membrane and pia mater)
What are the two types of protection the cerebrospinal fluid provides?
Physical protection: shock absorber, buoyant force to keep gravitational pressure off the brain.
Chemical protection: maintains solute concentrations in interstitial fluid surrounding neurons and removes waste
What is the choroid plexus?
Specialized region on the walls of ventricles that secretes cerebrospinal fluid into the vesicles and selectively pump sodium and other solutes from plasma into the ventricles to create osmotic gradient.
What is the subarachnoid space?
Space between the pia mater and the arachnoid membrane which is where the cerebrospinal fluid flows.
What are foramen?
The openings in the brain or skull that act as passageways for different structures of the nervous and circulatory system from one region to the other.
What is the arachnoid villi?
Fingerlike projections on the arachnoid membrane that allow cerebrospinal fluid to be reabsorbed into the blood.
What is the blood-brain barrier?
Functional barrier between interstitial fluid of the brain and the plasma characterized by the highly selective permeability of brain capillaries due to tight junctions
How does the blood-brain barrier form?
Induced by paracrine signals from pericytes (adjacent contractile cells) and astrocytes (feet surround the capillary)
How does the blood-brain barrier work?
Capillary endothelium uses selected membrane carriers and channels to move nutrients and other useful materials from the blood into the brain interstitial fluid, or waste from interstitial fluid to plasma. Any water-soluble molecule that is not transported in one of these carriers cannot cross the blood-brain barrier unless it is a small lipophilic/nonpolar molecules.
What is the spinal cord?
Major pathway between brain and skin, muscle, joints, and organs that contain neural networks responsible for locomotion.
How many pairs of spinal nerves are there in total, and what are the four levels it creates?
There are 31 pairs of spinal nerves in total that are separated into 4 levels: Cervical, thoracic, lumbar, and sacral (coccygeal)
What are cauda equina?
Thick elongated nerve roots that spinal nerves separate into after lumbar nerve 1-2
What is the difference between Dorsal and Ventral roots?
Dorsal: part of spinal nerve that joins the spinal cord to carry sensory (afferent) information to CNS
Ventral: part of spinal nerve that joins the spinal cord to carry motor (efferent) information to muscles and glands
What is the dorsal root ganglia?
Swellings found on the dorsal roots just before they enter the cord that contain cell bodies of sensory neurons.
What is found in the white matter of the spinal cord?
Dorsal ascending tracts that carry sensory info to the brain and ventral descending tracts that carry commands to motor neurons
What is found in the gray matter of the spinal cord?
- Somatic sensory nuclei: carry signals from temp, surface, vibration
- Visceral sensory nuclei: carry signals from the organs of the thoracic and abdominal cavities
- Autonomic efferent Nuclei
- Somatic Motor Nuclei
What is the brainstem?
Oldest and most primitive region of the brain consisting of the midbrain, pons and medulla.
What are cranial nerves?
Pairs of nerves branching from the brain (not spinal cord) that are sensory, motor or both in function. 10/12 pairs arise from the brain stem.
What is the Medulla’s structure and function?
Aka medulla oblongata;
structure: transition from spinal cord into brain proper and contains neuronal clusters
function: clusters control heart/blood vessel function, respiration and many digestive functions
What is the Pons structure and function?
Structure: Bulbous protrusion above medulla and below midbrain
Function: relay station between cerebellum and cerebrum. Regulates muscle reflexes involved in equilibrium (balance) and posture.
What is the midbrain structure and function?
Structure: Small area between lower brainstem (pons and medulla) and diencephalon.
Function: relay for visual and auditory info (in terms of balance), governs movement of eyes, gives rise to groups of modulatory neurons
What is Reticular formation structure and function?
Structure: Interconnected groups of neurons in midbrain and medulla
Functions: receives and integrates sensory input that plays a critical role in wakefulness and attention and gives rise to modulatory neurons
What are modulatory neurons?
Special neurons in midbrain and reticular formation that send neuromodulators (neurotransmitters) to bind to GPCR to initiate second messenger signalling and create subtle, long lasting changes.
What is the cerebellum’s functions?
- Processes sensory info from muscles, joints, vestibular system, and eyes.
- Integrate position and movement of body with the intent to move body.
- Maintains balance and controls eye movements
- Enhances muscle tone and plans, initiates and coordinates voluntary activity
- Stores procedurals important for motor learning
What is the diencephalon?
Between brain stem and cerebrum, composed of hypothalamus and thalamus and acts as the primary integration centre.
What is the thalamus?
Part of diencephalon that receives information from almost every area of the CNS and sends info to the same areas. Includes sensory/motor info, emotional info, and arousal.
What is the hypothalamus?
Part of diencephalon most involved in directly regulating internal environment, including:
- body temp
- thirst/urine output
- food intake
- anterior pituitary hormone secretion
- produces neuroendocrines vasopressin + oxytocin
- Uterine contractions and milk ejection
- major ANS coordinating center
- emotional and behavioural patterns
What is the cerebrum structure?
Largest, newest, most distinct part of the brain composed of two hemispheres connected at corpus callosum. Includes cortex, white matter, basal ganglia, and limbic system.
What is the cerebral cortex?
Highest most complex integrating area of the brain that plays a key role in most sophisticated neural functions. Includes gray matter with sulci (furrows) and gyri (convolution) to be used as landmarks.
What are the five major lobes of the cerebral cortex?
- Frontal: skeletal muscle movement and executive functions (thinking)
- Parietal: touch, taste, temperature
- occipital: vision/visual processing
- Temporal: hearing
- Insular: taste/smell, interoception
What is cerebral lateralization?
Left brain-right brain dominance that occurs
because functional specialization is not symmetrical across the cerebral cortex.
What functions occur on the right and left side of the brain (typically)?
Left: Language and verbal skills, writing, mathematical calculation
Right: spatial recognition, face recognition, emotion processing, artistic functions
How does language processing occur?
Input from the visual cortex (reading) or auditory cortex (listening) goes to Wernicke’s area and then broca’s area. After processing in broca’s area, information travels to motor cortex to initiate spoken or written action
What is aphasia?
Inability to comprehend or formulate language due to damage to Wernicke’s area (recptive aphasia) or broca’s area (expressive aphasia)
what is the difference between damage to Wernicke’s area and broca’s area?
Wernicke’s area: difficulty understanding spoken or visual language (receptive aphasia), nonsensical speech because of trouble connecting words with meaning (Jargon aphasia)
Broca’s area: Difficulty expressing complex ideas, distorted words, difficulty interpreting words or sentences with several elements.
What is basal ganglia structure and function?
Structure: region of cell bodies (ganglia) that form a complex circuit between motor cortex, premotor cortex, cerebellum, thalamus, and other areas
Function: control of cognitive ability and movement.
What is parkinson’s disease?
Loss of dopaminergic neurons (neuromodulatory neurons) in basal ganglia. Causes tremors, loss of ability to move, and cognitive deficits.
Huntington’s disease: loss of cholinergic neurons (neuromodulatory neurons) in basal ganglia that would have activated dopaminergic neurons. Causes uncontrollable movements, loss of coordination, dementia.
What is the limbic system?
Structure: Oldest part of the cerebrum including amygdala, hippocampus, and cingulate gyrus. It is strongly connected with the diencephalon and parts of the midbrain.
Function: Links higher cognitive functions and primitive emotional responses such as fear, aggression, reward, social and sexual behaviour.
What do each part of the limbic system play a role in?
Amygdala: emotion and memory
Hippocampus: learning and memory
Cingulate gyrus: emotion
How does the Limbic System Pathway work?
- Sensory stimuli from sensory neurons reach cerebral cortex
- Cerebral cortex integrates signal and synapses with Limbic system
- Limbic system creates emotion. Emotion moves to Cerebral cortex to create awareness of emotion, as well as to hypothalamus and brain stem.
- Hypothalamus and brain stem initiate voluntary and unconscious motor responses, autonomic responses, endocrine responses, and immune responses.
