Chapter 6 - CNS Flashcards
What organs makeup the CNS?
brain and spinal cord
What percent of CNS cells are neurons?
10%
What cells makeup the 90% of CNS?
neuroglia (white;fat)
What is the fluid that supports the CNS
cerebral spinal fluid (CSF)
What are fibers?
axons from multiple nuclei running in parallel; aka nerve tracts or white matter
What are the two layers directly underneath the skin?
Aponeurosis and Periosteum
What is the aponeurosis layer?
collagen cells for protection
What is the Periosteum layer?
vascular tissue
What are the three layers of the Meninges?
Dura mater, Arachnoid mater, Pia mater
What is the space between the dura mater and arachnoid mater?
Subdural space
What is the space called between the arachnoid mater and the pia mater?
Subarachnoid space
What is the layer directly beneath the Pia mater?
Cerebral Cortex
Dura Mater
thick, strong connective tissue layer
Arachnoid Mater
thin, transparent fibrous membrane
Pia Mater
Delicate connective tissue layer
Hemorrhage/Hematoma
Physical trauma to the brain leading to bleeding within the spaces between the maters of the meninges
Subarachnoid hemorrhage
bleeding between the arachnoid and pia maters
Subdural hematoma
tearing of veins between dura and arachnoid maters
Epidural hematoma
collection of blood between dura mater and surrounding bone
What are the functions of CSF?
- Homeostatic regulation of ions and nutrients in extracellular environment
- Support and cushioning of the brain and spinal cord with buoyant forces
- Chemical and immunological buffering of the fluid surrounding neurons and glia
CSF moves through the brain through:
ventricles
What produces CSF?
choroid plexus and ependymal cells within ventricles
How is CSF stored?
stored in ventricles
Blood Supply to the brain pathway:
Internal carotid artery/Vertebral artery => Anterior portion of brain/Posterior portion of the brain => Circle of Willis (connection)
What are the safeguards in the CNS to maintain blood flow?
- Circle of Willis allows blood supplying anterior and posterior portions of brain to overlap, ensuring that if one path is blocked the other one can still supply blood to CNS.
- Anterior cerebral artery connects BOTH carotid arteries, allowing blood flow if one is blocked.
- Formation of the Basilar artery from the two vertebral arteries and spinal arteries again allow blood flow if one is blocked.
What is a stroke?
interrupted blood flow to the brain has caused neuronal death
What are the different types of stroke?
Ischemic (reduced blood flow; greater survivorship)
Hemorrhagic (bleeding)
What are the risk factors of having a stroke?
Elevated blood pressure, smoking, obesity, elevated blood cholesterol, diabetes, or heart problems.
What are the types of neuroglia cells?
Oligodendrocytes, Astrocytes, Ependymal cells, and Microglia.
Oligodendrocytes
axonal physical support, create myelin sheath surrounding neurons in CNS, aid in conductance of axonal action potentials, metabolic support to neurons
Astrocytes
star-shaped cells, multiple functions including neurotransmitter secretion/absorption, 3D structure of the brain, glycogenesis, fluid regulation, release of ATP, repair.
* A LOSS of astrocytes in the CNS leads to OVER-excitability of neurons and an OVERPRODUCTION might lead to a DECREASE in neuron activity.
Ependymal cells
epithelial cells that line the brain ventricles, produce CSF, site of cells involved in neuro-regeneration, apical surface covered in cilia and microvilli (reabsorption)
Microglia
resident macrophages, first line of defense for active immune system in CNS; responsible for: removal of damaged neurons/neuroglia and infectious agents, recognition of infectious agents and action as antigen-presenting cells, prevention of inflammation within cells by rapid removal of infectious agents. Consume foreign material by phagocytosis (glitter cell)
What are the main functions of the CNS?
- Receiving and processing external sensory information
- Integrating information from a wide range of sources: processing it, acting on it, or storing it in memory.
- Sending signals that control the main functions of body tissues
- Consciousness perception of senses, language, reason, memory, emotion, etc. (all emergent properties)
Reflex arc
- smallest, simplest neuronal circuit
- action potential does not travel to the brain for processing; i.e. the response is MUCH faster.
- basic components: sensory (afferent) neuron, motor (efferent) neuron, and target (organs/muscles)
- can be monosynaptic (CANNOT be modified) or poly-synaptic (CAN be modified; minim. of 3 cells)
- autonomic reflexes affect glands, smooth muscle, and cardiac muscle; somatic reflexes affect skeletal muscles and organs
Spinal Cord
- Long, thin, tubular bundle of neurons
- Carries info to/from the brain
- Encased in vertebrae and meninges
- divided into different segments that correspond w/ overlying vertebrae
What is white matter organized into?
Funiculi (columns): dorsal, lateral, and ventral
What are funiculi organized into?
nerve tracts
Dorsal Ramus
supplies the muscles of the back, and delivers sensory information from the back to the CNS
Ventral Ramus
carries sensory information to and from the other parts of the body
Ventral root
motor (efferent) axons
Dorsal root
sensory (afferent) axons (contains the dorsal root ganglion which makes it easily recognizable)
Gyri
elevated ridges or hills on the brain
Sulci
Small grooves or valleys on brain
Fissures
Deep grooves or canyons
Within the brain, neuronal cell bodies are organized into _______________, while axonal projections are organized into _____________.
grey matter; white matter.
Fibers
carry information within and between hemispheres
Association fibers
connect areas of cerebral cortex within ONE hemisphere
Commissural fibers
connect one cerebral hemisphere to the other
Projection fibers
connect the cerebrum with other parts of the CNS and spinal cord
Three parts of the brainstem?
medulla oblongata, pons, midbrain
Medulla Oblongata
relay station for ascending afferent and descending efferent motor tracts between the spinal cord and the brain.
- cardioacceleratory and inhibitory centers that alter heart rate
Pons
- relay station from medulla to higher cortical structures of the brain
- has a bridge-like structure to connect different parts of the brain
Midbrain
nerve pathway of the cerebral hemisphere and contains auditory and visual centers as well as the nuclei for the oculomotor, trochlear, and trigeminal cranial nerves, and the tectum.
Nuclei components within the Medulla Oblongata
- reticular process
- respiratory nuclei
- vasomotor nuclei
- cardiac nuclei
- coughing, gagging, swallowing, vomiting nuclei
- nuclei involved in conscious regulation of skeletal muscle contraction
- nuclei involved in balance, coordination, modulation of sound
- nuclei of trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal nerves
Nuclei components of Pons
- pontine nuclei
- trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal nerves
Nuclei components within Midbrain
- auditory and visual centers
- nuclei of oculomotor, trochlear, trigeminal cranial nerves
- corpora nuclei
- tegmentum
- cerebral peduncles
- substantia nigra
12 cranial nerves
- Olfactory
- Optic
- Oculomotor
- Trochlear
- Trigeminal
- Abducens
- Facial
- Vestibulocochlear
- Glossopharyngeal
- Vagus
- Accessory
- Hypoglossal
Parts of cerebellum
Arbor Vitae, Flocculonodular lobe, Vermis, Lateral hemishperes
Arbor Vitae
white matter of the cerebellum
Flocculonodular Lobe
control of balance and eye movements
Vermis
posture, locomotion, fine motor coordination
Lateral Hemispheres
planning, practicing, learning complex movements
Parts of Diencephalon
Thalamus, Subthalamus, Epithalamus, Hypothalamus
Thalamus
largest part; receives input from most sensory neurons in the body
Subthalamus
motor functions
Epithalamus
emotional and visceral responses to odors; biological clock
Hypothalamus
major endocrine tissue; homeostatically regulates many important physiological processes.
Cerebral Cortex
- where complex information processing occurs
- anatomically divided into 6 layers
- differences in function between hemispheres (hemispheric lateralization)
- essentially a layer of nervous tissue on top of cerebrum and divided into left/right hemispheres
Seat of human consciousness is in the:
cerebral cortex
Precentral gyrus
primary motor cortex (M1)
Postcentral gyrus
primary somatosensory cortex (S1)
Properties of circuits
- developed during fetal and neonatal growth
- found in brain/spinal cord and part of reflex arcs
- maintained by use and display plasticity
Different types of circuits
- simple
- complex
- divergent
- convergent
- rhythm
- parallel after discharge
Neuroplasticity
- constantly changing synaptic connections in response to internal/external influences on a millisecond time scale.
Schwann cells
- Myelinate PNS neuron axons
- Repair of damage to PNS axons, regeneration of axonal connections which does NOT occur in CNS
SImple Circuits
Formed when the cell communicates solely with another cell, which is UNCOMMON in CNS
Complex Circuits
formed when there are multiple connections within neurons, common in CNS
Divergent Circuits
Distributes info from one cell onto multiple cells. Can closely coordinate movement of large amounts of tissue, at the loss of regulating individual tissue parts.
ex. Skeletal
Convergent Circuits
formed when multiple synaptic junctions are made between many neurons and a single neuron. Lose the ability to identify the precise source of incoming information but gain an increased sensitivity because the output of many cells is focused on just a few cells. COMMON in CNS.
Rhythm Circuits
underlie activities like breathing, walking, etc. Chain of interconnected neurons, each cell stimulates the next one with a (+) feedback mech. Only turned off when a cell becomes exhausted/inhibited by an outside source. Central-pattern generating (CPG) circuits.
Parallel after discharge circuits
single neuron can send inhibitory or stimulatory signals to diff. chains of neurons that all send input into a single cell. allows final neuron to receive complex inputs from diff. circuits of other neurons. Underlies mathematical thinking.
What is the order a compound must go through to move from plasma to CSF
Capillary endothelium => basal lamina => pericyte => astrocyte
Blood Brain Barrier (BBB)
- interface between plasma and CSF
- highly selective endothelial semipermeable border that prevents solutes from circulating blood non-selectively moving into the CSF
- protects brain from blood-borne infections, drugs, and toxins
- maintained by neurons, neuroglia, pericytes, and capillary endothelium (neurovascular unit)
Lateral Ventricles are separated by thin:
Septa Pellucida
CSF production is under the regulation of the ___________ system.
autonomic
