Intro NS Flashcards
PSN
CRANIAL NERVES
SPINAL NERVES
CNS
BRAIN
SPINAL CORD
PNS
Somatic - sensory information to the CNS
Autonomic
1. Sympathetic
2.Parasympathetic
3. Enteric
General function of PNS
Conduct impulses to or away from the CNS
Generla function of CNS
Integrate & coordinate incoming and outgoing neural signals Carry higher mental functions
General function of Enteric
The enteric nervous system is considered a third autonomic division.
It consists of a neural plexus, lying within the walls of the gut, that is involved in controlling peristalsis and gastrointestinal secretions.
CNS
Weights ~ 400 g at birth, but by the end of the first 3 years of life, this weights triples, primarily due to the addition of myelin and growth of neuronal process
The adult brain weights ~ 1,400 g, ~2% of body weigh
Human mental capacities are related to the complexity of neuronal interconnections and the differential development of the different areas of the cerebral cortex with their unique higher cortical functions, not by the size!
Anatomic directions of the CNS
In the cerebral hemisphere (forebrain):
Anterior (Ventral) - toward the base of the brain * Posterior
(Dorsal) - toward the top of the brain
In the brainstem and spinal cord:
Anterior = Ventral
Posterior = Dorsal
Rostral - toward the anterior pole of the forebrain (frontal pole)
Caudal - toward the occipital pole or the inferior pole of the spinal cord or toward the “tail”
e.g. the midbrain is rostral to the pons but caudal to the thalamus
Anatomical Planes
Horizontal = Axial = Transverse sections
Sections perpendicular to the long axis of the person’s body
Sagittal sections passing through the midline = midsagittal
Parasagittal sections = sections that passes just off the midline
Types of Glial cells
Astrocytes - protoplasmic & fibrous
- BBB & homeostasis
Migroglia - support cell, immune system
Oligodentrocytes -
myelin production (Schwan cells)
NUEROGLIAL FUNTIONS (Glial cells or glia)
- Supporting and nourishing the neurons
- Not essential for processing information
- 10–50 times in CNS
- Separate and/or insulate neurons
- Some glial removes debris after injury or neuronal death
- Buffers the K+ ion concentration in the extracellular space
- During development, some cells guide migration of neurons and direct the outgrowth of axons * Some forms tight junctions with endothelial cells – Blood Brain Barrier
- Some cells have nutritive functions for nerve cells
CNS -glia cells
oligodendroglia
astrocytes
ependymal cells
microglia
protoplasmis astrocyte
fibrous astrocyte
oligodentrocyte
PNS
Schwann cell
In the PNS, neuroglia include satellite cells around the neurons in the spinal (posterior root) and autonomic ganglia and Schwann (neurolemma) cells.
Gray matter
Gray matter is found in the cortical layer (cortex) on the surface of the forebrain and cerebellum.
The gray matter of cerebral cortex is composed of neuron cell bodies of variable sizes and shapes intermixed with myelinated and unmyelinated fibers.
Gray matter can also be found in deep structures (forebrain, basal ganglia and limbic system).
Functional units
White matter – contains nerve axons.
Nuclei – a collection of of nerve cell bodies within the CNS
*In the PNS is called a
ganglion
Tract – a bundle of axons traveling from one area to another within the CNS. In the PNS axon bundles are called a nerve.
Tracts may descend or ascend connecting different regions in a vertical way that may decussate.
Horizontal connections are called commissures.
Corte coronal - brain
Cortex
White matter
Gray matter
Nuclei
Commussure
Tract
Brain
The cortex of each lobe IS:
thrown into folds, gyri, (singular, gyrus)
separated by grooves called sulci (singular, sulcus)
or deeper grooves called fissures.
Lobes of fissures in cerebral hemispheres
Longitudinal fissure
} separates the two hemispheres
Central sulcus of Roland
} separates the frontal and parietal lobes
Lateral or Sylvian fissure
} separates the temporal lobe from the frontal and the parietal lobes
Parietooccipital fissure
} visible on the medial surface of the brain, separates the occipital lobe from the parietal lobe
Brain protection
The brain is lined by the meninges and protected by the cranium
Sulcus within the cerebrum
Cingulate sulcus
Paracentral sulcus
Central sulcus (Roland)
Marginal sulcus
Parietooccipital sulcus
Calcarine sulcus
CNS: Brain
BRAIN PROPER
Forebrain
1.Telencephalon
Cerebral hemispheres
Deep structures
- Diencephalon
Thalamus
Hypothalamus
Epithalamus & Subthalamus
CNS: Brain
BRAIN STEM
-Midbrain
- Midbrain
-Hindbrain
- Metencephalon
Pons
Cerebellum - Medulla
Brain composition
The brain is made up of many specialized areas that work together:
Four (4) Lobes:
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
+ Brain Stem + Cerebellum
Cerebral lobes
integrate motor, sensory, autonomic, and intellectual processes
are organized along functional lines
The NS is constructed with bilateral symmetry.
For most sensory and motor functions, the left side of the brain functionally corresponds with the right side of the body.
Some higher cortical functions are represented more strongly in one hemisphere, however, in terms of gross anatomy, each hemisphere has a similar structure.
Central sulcus (Rolando)
Divides the pre central gyrus from the post central gyrus
Pre-central gyrus
primary motor cortex of contralateral voluntary movements
Post-central gyrus
primary somatic sensory cortex
(kinesthetic and tactile)
Homunculus
Cortical representation of how neurons are somatotopically organized and associated both, functionally and anatomically, with specific body parts.
Frontal lobe
It is the emotional control center and home to personality and decision making abilities
- Primary motor cortex: descending cell bodies to the spinal cord that control voluntary movements
- Premotor cortex – regulates voluntary motor activity or behavior
- Broca’s area - production of written and spoken language, primarily in the dominant (typically left)
-Prefrontal association areas - emotion, motivation, personality, initiative, judgment, ability to concentrate, and social inhibitions
Prefrontal cortex
processing intellectual and emotional events
Parietal lobe
- process linguistic information
- Involved with other parts of the brain, such as the amygdala, to mediate the emotional response to language
Angular gyrus- Processing the meaning and semantics of words
Supramarginal gyrus – involve in determining their sound
Postcentral gyrus – primary somatosensory cortex
Primarily involved in initial cortical processing and perception of touch, pain and limb position (details will be discussed in the Somatosensory lecture) on both the lateral and medial aspects of the parietal lobe.
It is also involved in complex aspects of spatial orientation and perception, including self-perception.
Temporal lobe
Important for processing auditory information (Primary auditory cortex), language, and certain complex functions.
Superior temporal gyrus
process and interpret what we hear
Middle and Inferior gyrus complex visual functions
Anterior medial areas
involved in complex aspects of
learning, memory and emotion
Lesions in auditory cortex leads to difficulty in interpret or localize a sound in space, do not cause deafness
Occipital lobe
Primarily involved in processing visual information.
Visual association areas surround it and mediate the ability to see and recognize objects.
A lesion of the primary visual cortex leads to loss of visual input from the contralateral half of the visual field, details will be discussed later.
Insula (Island of Real)
A portion of neocortex covered by portions of frontal, parietal and temporal lobes.
Insular cortex receives nociceptive and viscerosensory input.
Spontaneous lesions in this area decrease or complete loss of the desire to continue addictive behaviors.
Limbic lobe
Composed of the:
* Cingulate gyrus
* Parahippocampal gyrus
* Uncus
* Subcallosal area
A ring of cortex in the frontal, parietal and temporal lobes that contributes to “this” lobe, however, it is NOT a true lobe.
Its function is complex, linked to circuits that modulates memory, learning and behavior.
Limbic structures
Amygdala
Hippocampus
Stria terminalis
*Interconnected and interacting structures that modulate emotional behaviors and play a role in learning and memory.
Basal Ganglia
- Caudate nucleus
- Lenticular nuclei
a. Putamen
b. Globus pallidus
Procedural learning relating to routine behaviors or “habits,” eye movements, and cognitive, emotional functions
Play a central role in a number of neurological conditions such as:
* Parkinson
* Obsessive Compulsive Behavior (OCD)
Core structures involved in the brain reward pathway
Ventral tegmental area (VTA)
* Nucleus accumbens
* Prefrontal cortex
* Amygdala
Other structures, such as the hypothalamus, modulate this circuit.
Diencephalon
Hypothalamus, thalamus, and epithalamus & sub thalamus
Bounded anteriorly by the anterior commissure, a fiber bundle containing many olfactory and temporal lobe fibers and posteriorly by the posterior commissure.
Hypothalamus
Structurally part of the diencephalon but functionally part of the limbic system.
Plays a role in coordinating and integrating endocrine, autonomic and homeostatic functions.
It regulates temperature, endocrine functions, feeding, drinking, emotional & sexual behaviors
Thalamus (The “gatekeeper” of the cortex)
A critical “station” that process all sensory information (except for olfaction) on its way to the cortex.
It is also involved in:
* processing motor information
* integrating higher order cognitive and emotional information
* regulating cortical activity
Brainstem: midbrain & hindbrain
The brainstem provides the conduit by which all ascending and descending information travel to the brain from the spinal cord and viceversa.
Brain ventricular system
The ventricles are cavities within each hemisphere that contains cerebrospinal fluid (CSF). CSF is an important source of electrolytes, but it also protects, supports the brain as well as serve as a conduit for neuroactive and metabolic products. We will discuss it in another lecture.
Lateran ventricules (interventricular foramen)
Third ventricle (cerebral aqueduct / Sylvius)
Fourth ventricle
The Spinal Cord
Major reflex center and conduction pathway
- Protected by the vertebrae, associate muscles and ligaments, spinal meninges and cerebrospinal fluid (CSF)
- Begins as a continuation of the medulla oblongata (medulla)
- ~ 42-45 cm long, occupies 2/3 of the vertebra canal
- Two enlargement sites:
- Cervical
- Lumbosacral
Curvatures of Vertebral Column
Curvatures:
Cervical - 2
Thoracic - 1
Lumbar -2
Sacral - 1
During fetal period - the vertebral column grows faster than the spinal cord
- At birth - the tip of the conus medullaris is at the level of L4–L5
- Postnatal life - the spinal cord is shorter than the vertebral column
- progressive obliquity of spinal nerve roots
- the length of nerve roots increases progressively
Spinal cord
Conus medullaris – terminal part, may terminate as high as T12 vertebra or as low as L3 vertebra.
Length of spinal cord:
* In embryo - occupies the whole length of the vertebral canal
* At birth - the tip of the conus medullaris is at the level of L4–L5
* In adult - approximately at the level of L2
Spinal cord injuries
Transection of the spinal cord results in loss of all sensation and voluntary movement inferior to the lesion.
Transection between the following levels will result in the indicated effects:
* C1–C3: no function below head level; a ventilator is required to maintain respiration.
- C4–C5: quadriplegia (no function of upper and lower limbs); respiration occurs.
- C6–C8: loss of lower limb function combined with a loss of hand and a variable amount of upper limb function; the individual may be able to self-feed or propel a wheelchair.
- T1–T9 paraplegia (paralysis of both lower limbs); the amount of trunk control varies with the height of the lesion.
- T10–L1: some thigh muscle function, which may allow walking with long leg braces.
- L2–L3: retention of most leg muscle function; short leg braces may be required for walking.
