1. Introduction to the Nervous System Flashcards
The nervous system
a communication and control network that allows an organism to interact with its environment
General functions of nervous system
Sensory detection, information processing, and the expression of behaviour
Central nervous system (CNS)
Brain and spinal cord
Peripheral nervous system (PNS)
Afferent/sensory division and efferent/motor division
Afferent division
The sensory system, generates input to the CNS
Efferent division
Receives output from CNS, to the somatic nervous system and autonomous nervous system.
Somatic motor system
Efferent division of PNS that stimulates skeletal muscle activity
Autonomic nervous system
Efferent division of the PNS that includes the sympathetic division, parasympathetic division, and enteric nervous system.
Enteric nervous system stimulates…
Intestinal muscle wall, mucosa
Sympathetic division stimulates…
Smooth and cardiac muscle, glands
Parasympathetic division stimulates…
Smooth and cardiac muscle, glands
Components of the Nervous System
neurons, neuroglial cells, blood vessels, connective tissues
Soma
Factory of the neuron
Dendrite
Input transmission of neuron
Axon
Output transmission of neuron
Nissl bodies
A Nissl body is a large granular body found in neurons. These granules are of rough endoplasmic reticulum (RER) with rosettes of free ribosomes, and are the site of protein synthesis.
Predominate neuron shape in invertebrates
Unipolar
Predominate neuron shape in vertebrates
Multipolar
Bipolar neuron example
Dorsal root ganglia cells
Pseudounipolar neuron example
Retinal cells, olfactory epithelium cells (unmyelinated, no dendrites)
Multipolar neuron example
Interneurons, motor neurons
Traditional senses
Sight, hearing, smell, taste touch
Non-traditional senses
Nociception (tissue damage), equilibrioception (balance, coordinate movements), proprioception (know the body parts and positioning), and thermoception (temperature changes)
What do sensory receptors do?
Convert a stimulus into neuronal activity
What type of neurons constitute 90% of all neurons?
Interneurons
What type of neurons constitute 9% of all neurons?
Motor neurons
What type of neurons constitute 0.9% of all neurons?
Sensory neurons
Sensory neurons
Afferent neurons
Bipolar
Sense detection by sensory receptors on receptor cell, transmitted down myelinated axon
Motor neurons
Efferent neurons
Multipolar
Initial signal recieved by dendrites
Axon terminals act on muscles at neuromuscular synapse
Interneuron
Association neuron
Multipolar
Cell body, dendrites, axon terminals
Unmyelinated
Why does shingles (caused by herpes zoster) affect the skin after many years latency?
Reactivated herpes zoster is transported along the sensory axons to the skin.
What’s the consequence of interruption? Such as cancer drugs
Neurodegeneration
Fast axonal transport
Membrane-bound organelles and mitochondria
Slow axonal transport
Proteins
Anterograde axonal transport
From the soma toward the axonal terminals, kinesin
Retrograde axonal transport
From the axonal terminals toward the soma, dynein
Axonal transport depends on what? Describe the mechanism of this.
The movement of transport filaments. This requires energy supplied by glucose. Mitochondria controls the level of cations in the axoplasm by supplying ATP to the ion pumps. An important cation for axonal transport is Ca2+. Transport filaments move along the cytoskeleton (microtubules [M] or neurofilaments [NF]) by means of cross-bridges. Transported components attach to the transport filaments. CaBP, Ca2+-binding protein; NF, neurofilaments.
Role of supportive matrix of the CNS
Provides local environment suitable for neurons to function
What are the components of the local environment?
Neuroglia, CNS circulation, the blood-brain barrier (BBB), the cerebrospinal fluid (CSF)
What are the major roles of the supportive matrix in neurotransmission?
Taking up neurotransmitters; providing myeline sheaths
Neuroglia in the CNS
Astrocytes, oligodendroglia, microglia, ependymal cells
Astrocytes
Structural support, metabolic support; neurotransmiitter uptake and release; ion homeostasis; nervous system repair; synaptic plasticity.
Oligodendroglia
Myelination
Microglia
Immune defense
Ependymal cells
Production of the CSF
Neuroglia in the PNS
Satellite cells and Schwann cells
Satellite cells
Function similar to astrocytes
Schwann cells
Myelination (debris clearances, nerve regeneration). Can be myelinating or nonmyelinating.
Myelin
Ensures fast saltatory conduction of AP.
CNS: oligodendroglia, a single cell myelinates many axons
PNS: Schwann cells, a single cell myelinates only one axon
What cells can give rise to brain tumors in the adult brain?
Astrocytoma, oligodendroglioma, ependymoma.
In babies and infants: neuroblastomas.
Features of neurons
Post-mitotic
Dendrites and axons
Excitable
Functional units of nervous tissue
Features of neuroglia
Mitotic
No branches
Non-excitable
Supporting cells of nervous tissue
Why does the gray matter have a higher metabolic rate?
The gray matter contains soma which is the factory of the neuron.
Gray matter
Soma and dendrites (axons, glial cells, capillaries)
White matter
Axons (glial cells, capillaries)
Diencephalon
The thalamus and hypothalamus
Cerebrum
Frontal lobe, temporal lobe, parietal lobe, occipital lobe
Brain stem
Midbrain, pons, medulla
Location of medulla
The rostral extension of the spinal cord (lowest)
Location of pons
Rostral to the medulla (just above the medulla)
Location of midbrain
Rostral to the pons
Ten cranial nerves functions
Eye movement Head movement Facial expression Swallowing Taste Hearing Sensory Motor Autonomic functions of viscera (glands, digestion, heartrate)
Functions of the brain stem in general
Autonomic centers and relay nuclei
Function of medulla
Breathing, blood pressure, swallowing, coughing, vomiting
Function of pons
Balance and posture, breathing
Function of midbrain
Micturition (urinary reflex), eye movements, auditory and visual systems
Cerebellum location
Between the cortex and the spinal cord, attached to the brain stem and lies dorsal (behind) to the pons and medulla
Cerebellum functions
Coordination of movement, maintenance of posture and balance
Thalamus and hypothalamus location
Between the cerebral hemispheres and the brain stem, so called diencephalon (“between brain”)
Functions of the thalamus
Processes sensory information going to the cerebral cortex and motor information coming from the cerebral cortex to the brain stem and spinal cord
Functions of the hypothalamus
Regulates body temperature, food intake, and water balance, and controls the hormone secretions of the pituitary gland (anterior pituitary hormones, antidiuretic hormone, oxytocin)
Cerebrum location
The anterior (front) portion of the brain Divided into left and right hemispheres connect by the corpus callosum The cerebral hemispheres consist of the cerebral cortex (grey matter), an underlying white matter, and three deep nuclei (basal ganglia, hippocampus, amygdala)
Cerebrum functions
Perception, higher motor functions, cognition, memory, emotion
Gyrus vs Sulcus
A gyrus is a ridge on the cortex, a sulcus is a groove
Fissure
A fissure is a larger furrow than a sulcus, that divides the brain into hermispheres
Sylvian/lateral fissure
separates the frontal and parietal lobes of the brain from the temporal lobe.
Transverse fissure
Horizontal fissure found between the cerebrum and the cerebellum
Longitudinal fissure
Separates hemispheres
Three areas of cerebral cortex
motor areas, sensory areas, and association areas
Functions of cerebral cortex
Receives and processes sensory information and integrates motor functions
Relative size of areas of cerebral cortex
Sensory and motor areas make up ~1/5 of the cortex, and the association cortex makes up most of the cortical surface.
Roles of cerebral cortex parts
Sensory and motor areas are directly involved in sensory or motor processing. The association cortex analyzes the incoming information and translates it into something meaningful (perception)
Motor cortex location
Frontal lobe
Auditory cortex location
Temporal lobe
Sensory cortex location
Parietal lobe
Visual cortex location
Occipital lobe
Olfactory and gustatory cortex location
Frontal lobe
Neuron v ganglion
A group of neurons in the CNS and in the PNS, respectively
Location of basal ganglia
Base of forebrain
Location of hippocampus
In the temporal lobe
Location of amygdala
In the temporal lobe
Function of basal ganglia
Movement (parkinsons, huntingtons)
Function of hippocampus
Memory
Function of amygdala
Emotion
Ventricles
In the brain: two lateral ventricles, the third ventricle, and the fourth ventricle
Foramina
Interventricular foramina and cerebral aquaduct
Cerebrospinal fluid (CSF)
Liquid that fills and circulates within the ventricular system of the brain
Produced by the choroid plexus
CSF sampling: lumbar puncture (lumbar cistern)
Functions of ventricular system and CSF
Distribute nutritive materials to and removes wastes from nervous tissue; protection of the brain
Hydrocephalus
An abnormal accumulation of CSF in the ventricles
Why brain infections are difficult to treat?
Antibodies too big to cross the BBB
Why can radiologists exploit brain tumors by introducing substance into the circulation?
Brain tumors cause the disruption of the BBB, which leads to leakage of radiolabelled substance into the region occupied by the brain tumor
How is the BBB formed
By capillary endothelial cells, which are connected by tight junctions, and astrocytes.
What can cross the BBB
The BBB only allows the passage of water, some gases (oxygen, carbon dioxide), and some ions by passive diffusion; a few water-soluble substances (glucose and amino acids) by active transport; lipid-soluble substances.
What are the functions of the BBB
Protect the brain from bacterial infections, and damage by neurotoxic molecules (neurotoxins).
Location of spinal cord
The most caudal portion of the CNS; extend from the base of the skull to the first lumbar vertebra; lies within the bony vertebral column.
31 pairs of spinal nerves: cervical (8), thoracic (12), lumbar (5), sacral (5), coccygeal (1)
Functions of spinal cord
Contain both afferent and efferent nerves
Ascending pathways: carry sensory information from the periphery to higher levels of the CNS
Descending pathways: carry motor information from higher levels of the CNS to various organs
The “information highway of the body“ to connect the various organs of body to the brain.
Reflex arc
The simplest type of neural circuit, e.g. “withdrawal flex”
Nocioceptors detect pain, propagates through dorsal root to interneurons, which feedback to motor neurons through the ventral root, to act at neuromuscular junction and pul away.
Degeneration
Chromatolysis, wallerian degeneration
Regeneration
In the PNS, not CNS
Axon growth
Trophic factors (NGF, neurotrophin, CNF)
