Nervous System Structure Flashcards
Glial cells
Aka neuralgia
Cells that support neuronal function
Capable of cellular division and healing in traumatic injury
Often responsible for brain cancer
Form myelin, maintain homeostasis, support and protect neurons in CNS and PNS
Types of glial cells
Microglia Ependymal cells Satellite cells Astrocytes Oligodendrocytes Schwann cells
Microglia
CNS’s macrophages, arriving from white blood cells called monocytes
Phagocytose microbes and cellular debris
Ependymal cells
Epithelial cells that line the space containing the cerebrospinal fluid
Connected through tight junctions and form the blood-cerebrospinal fluid barrier
Use cilia to circulate cerebrospinal fluid
Satellite cells
Support the ganglia, which are groups of cell bodies in PNS
Serve support function, supply nutrients to surrounding cells, control micro environment. Similar role to Schwann cells of CNS
Astrocytes
Star-shaped neuralgia in CNS that give physical support to neurons and help maintain the mineral and nutrient balance in interstitial space
Oligodendrocytes
Have processes that wrap many times around axons in CNS to form myelin sheaths
Can extend its processes to wrap around up to 50 axons in CNS
Similar to Schwann cells in PNS
Schwann cells
Wrap entire cell bodies around axons as myelin sheaths for conduction
Myelinating and non-myelinating Schwann cells
Non-myelinating involved in maintenance of axons and crucial for neuronal survival
White matter
Areas of nervous system that are composed of myelinated axons of neurons
Grey matter
Bundles of cell bodies of neurons
Nodes of Ranvier
Gaps between myelinated areas on axons through which an action potential slightly slows as it passes
Saltatory conduction
Action potentials jump from one node of Ranvier to the next, appearing to jump over myelinated areas, while in reality are just moving very fast through myelinated areas
Myelin insulates the axons and reduces capacitance of membrane, allowing faster conduction
Three functions of neurons
- Sensory (afferent): receive signals from receptor cell that interacts with environments and transfers signal to other neurons, brain filters 99% of sensory information, located more dorsally
- Inter neurons: transfer signals from neuron to neuron, 90% of neurons in human body
- Motor (efferent): carry signals to muscle or gland (called effector), located more ventrally
Nerves
Bundles of neuron processes, this includes axons and dendrites
Known as tracts in CNS
Reflex
Quick response to a stimulus that occurs without direction from CNS
Can require or not require interneuron
Negative feedback loop: stretch reflex senses stretching and motor neuron responds in opposite way to stretch change and flexes the muscle to return to normal length
Information sent to CNS and reflexes can be modulated by CNS
Functions of CNS
Integrates nervous signals between sensory and motor neurons
Functions of PNS
Handles sensory and motor functions of nervous system
Divided into somatic nervous system and autonomic nervous system
Somatic nervous system
Part of PNS which serves to primarily respond to external stimuli
Sensory neuron cel bodies are located in dorsal root ganglion
Motor neurons inner gate skeletal muscle (voluntary movement) and cell bodies located in ventral horns of spinal cord, release acetylcholine to effectors
Autonomic Nervous System (ANS)
Coordinates involuntary response to environment, altering processes within body to produce most adaptive physiological state and behavior
Sensory: receives signals primarily from viscera (organs in ventral body cavity)
Motor: conducts signals to smooth muscle, cardiac muscle, and glands
* sympathetic
* parasympathetic
Sympathetic nervous system
“Fight or flight” responses
Increases heart rate and stroke volume
Constructs blood vessels around digestive and excretory organs
Signals originate in neurons whose cell bodies are in the spinal cord. Cell bodies of postganglionic neurons lie far from effectors (within paravertebral ganglion) for coordinated strong response
Parasympathetic nervous system
“Rest and Digest”
Decreases heart rate and increases digestive and excretory activity
Signals originate in neurons whose cell bodies are found in the spinal cord and brain. Cell bodies of postganglionic neurons lie inside or near their effectors
What neurotransmitters does the ANS use?
All preganglionic neurons in ANS use acetylcholine with nicotinic (cholinergic) receptors across the synapse
All postganglionic neurons in parasympathetic branch use acetylcholine and muscarinic receptors at the effectors (cholinergic)
Postganglionic neurons in sympathetic nervous system use norepinephrine or epinephrine (noradrenaline and adrenaline) with adrenergic receptors at the effectors
Spinal cord
Acts as a bridge between peripheral nervous system and brain, conveying sensory and motor signals
Possesses limited integration functions such as walking reflexes, leg stiffening, and limb withdrawal from pain
Lower brain
Earlier stage of evolutionary development
Brainstem, cerebellum, and diencephalon
Integrates unconscious activities such as respiratory system, arterial pressure, salivation, emotions, and reaction to pain and pleasure
Brainstem
Controls basic involuntary functions necessary for survival
Consists of medulla, pons, and midbrain
Medulla: regulation of cardiovascular and respiratory systems, monitor CO2 in blood
Pons: coordinates communication between motor cortex and cerebellum, facilitating transfer of motor commands
Midbrain: relay station for auditory and visual signals
Cerebellum
Involved in coordination and planning of movement
Receives and processes sensory, motor, and vestibular input
Diencephalon
Consists of thalamus and hypothalamus
Thalamus: control center, or waystation because it processes almost all sensory info before reaching higher cortical centers. Receives motor commands from cortical areas on the way to spinal cord
Hypothalamus: maintains homeostasis in multiple systems such as temperature and water balance.
Hypothalamus and pituitary gland form major site of interaction between nervous and endocrine systems
Higher brain
Consists of Cerebrum (cerebral cortex)
Most recently evolved portion incapable of functioning without lower brain
Controls consciousness, memory, cognition, planning, and emotion
Main endpoint for a majority of neuronal input
Influences our perception of the world and what we process
Frontal lobe
Higher level executive functions such as planning and impulse inhibition
Includes motor cortex which controls voluntary movements
Map of specific sets of neurons to control certain body parts
Parietal lobe
Contains somatosensory cortex
- maps the body’s sensation of touch
- sensitivity depending on area devoted to area of body
Occipital Lobe
Where visual information is processed
Temporal lobe
Processing of olfactory and auditory information
Hippocampus and amygdala
Central to function of limbic system, which is primarily concerned with memory and emotion
Corpus callosum
Connects two hemispheres of the brain
Lateralization of cortical functions
Lateralized functions take place in one hemisphere or the other
Production and comprehension of language located in two areas in left brain
Categories of the types of methods used for studying the brain
Lesion studies
Imaging
Electrical activity
Sensory receptors
Used to bring information into the nervous system from the outside in the form of touch, sight, smell, and hearing
Transduct external or internal stimuli to electrical signals that can be conveyed to the CNS via sensory neurons
Each type has own neural pathway and termination point in CNS, resulting in various sensation
Types of sensory receptors
Mechanoreceptors: touch Thermoreceptors: temperature Nociceptors: pain (more extreme stimuli) Electromagnetic receptors: light Chemoreceptors: taste, smell, blood chemistry
Sensory information involved in somatosensory system
Sensations of touch, temperature and pain
Uses mechanoreceptors, thermoreceptors, and nociceptors
Sensory adaptation
Stimulus that occurs repeatedly at same intensity level evokes fewer and fewer action potentials in sensory receptors
Nervous system filtering of less important information
Phasic receptors
Sensory receptors that adapt very quickly and specialize in the perception of changes in stimuli
Tonic receptors
Sensory receptors that react more slowly
