Lab 11 - Nervous system: Nervous Tissue and spinal cord Flashcards
what is the nervous system?
An intricate and complicated network of tissues that regulates all body processes
what is the function of the nervous system?
it receives sensory information, integrates that information, and initiates reactive measures. these functions revolve around the maintenance of homeostasis.
what is homeostasis?
the ability of the body to maintain a controlled and stable internal environment by responding to internal and external stimuli.
Structurally, what are the two major divisions of the human nervous system?
Central and Peripheral nervous system (CNS & PNS)
what makes up the CNS
the brain and spinal cord
what makes up the PNS
cranial and spinal nerves, ganglia and sensory receptors
how do the PNS and CNS work together?
the CNS processes the information received by the sensory receptors of the PNS, and the CNS controls the actions of all parts of the body and is also the site of thoughts, emotions, and memory
what are the two types of cells found in the nervous system?
neurons and neuroglia
what are neurons?
neurons, or nerve cells form the functional portion of the system. They are highly specialized of impulse conduction and are responsible for all the special attributes associated with the nervous system; thinking, controlling muscle activity and regulating glands
what are the three classes of neurons based on FUNCTION?
sensory (afferent), Interneuron (association neuron), and motor (efferent)
what are sensory (afferent) neurons?
conducts the impulse from the sensory receptor to the CNS
what are Interneurons (association neurons)?
integrates information from the sensory neurons and passes the stimulus to motor neurons
what are Motor (efferent) neurons?
conducts the impulse from the central nervous system to an effector, usually a muscle or gland
what are dendrites?
nerve fibers projecting from the cell body of a neuron that receive input from a neuron
what are cell bodies?
contains the nucleus surrounded by cytoplasm w/ cellular organelles including nissl bodies (free ribosomes & RER), lysosomes, mitochondria; they integrate information from dendrites and other synaptic inputs
what are the parts to an axon?
axon hillock, axon collateral, axon terminal, and synaptic end bulbs/varicosities
what is an axon hillock?
cone-shaped elevation that joins the axon to the body; info from dendrites & cell body are collected and conducted through axon hillock
what is an axon collateral?
side branches along the length of an axon; provide modulation & regulation of cell firing pattern & represent a feedback system for the neural activity
what is an axon terminal?
axons and collaterals divide into fine processes; sites where synapses with other neurons are found, and neurotransmitters are stored here to communicate with other neurons via synapses
what are synaptic end bulbs/varicosities?
tips of some axon terminals swell into bulb shaped structures (synaptic end bulbs) or string of swollen bumps (varicosities)
what are schwann cells?
type of neuroglia in the PNS that myelinates a single axon; participaes in axon regeneration
what is the myelin sheath?
multilayered lipid and protein covering surrounding axons; electrically insulates the axon of a neuron and increases speed of nerve impulse connection
what is neurolemma?
outer nucleated cytoplasmic layer that encloses that myelin sheath and ONLY FOUND IN AXONS IN THE PNS; forms regeneration tube that guides and stimulates the growth of an injured axons
what are myelin sheath gaps or nodes of ranvier?
specialized regions in between axons that are unmyelinated; facilitates rapid conduction of nerve impulses
what are the three classes of neurons based on STRUCTURE
multipolar, bipolar, unipolar neurons
what are multipolar neurons?
several dendrites and one axon; neuron type that dominates the CNS
what are bipolar neurons?
have one dendrite and one axon and are found in the retina of the eye, inner ear, and the nasal epithelium; located in PNS
what are unipolar neurons?
have a fused axon and dendrite that emerge from the cell body as one unit. the dendrites of these neurons form many of the other sensory receptors in the PNS, but is located in the CNS
what are the functions of neuroglia (neuroglial cells)?
providing structural support for neurons, forming myelin sheaths around axons, engulfing microorganisms and cell debris, and forming cerebrospinal fluid. also prevents some substances from entering the central nervous system
what are astrocytes?
found in the CNS, most numerous and largest, star-shaped cells with many processes (protoplasmic and fibrous); contain microfilaments to support neurons, blood brain barrier, secrete chemicals to regulate growth in embryo, migration & interconnection among neurons in the brain, maintain appropriate chemical environment for the generation of nerve impulses, and role in memory & learning by influencing the formation of neural synapses
what are oligodendrocytes?
found in the CNS, resembles astrocytes, but are smaller w/ less processes; the processes are responsible for forming and maintaining myelin sheath around CNS axons
what is microglia?
found in the CNS, small cell w/ slender processes that give numerous spine like projections; functions as phagocytes; remove cellular debris formed during normal development of the nervous system and phagocytize microbes & damaged nervous tissue
what are ependymal cells?
located in the CNS, cuboidal to columnar cells arranged in a single layer that have microvilli & cilia that line the ventricles of the brain and central canal of the spinal cord; produce monitor and assist in circulation of cerebrospinal fluid, and form the blood cerebrospinal fluid barrier
what are schwann cells?
found in the PNS, type of neuroglia in the PNS that myelinates a single PNS axon; participates in axon regeneration
what are satellite cells?
found in the PNS, flat cells that surround cell bodies of neurons of PNS ganglia; structural support, regulate the exchanges of materials between neuronal cell bodies and interstitial fluid
what is white matter?
bundles of axons that make up the white matter carry sensory information to the brain and motor information back to the peripheral nervous system.
what is gray matter?
contains cell bodies and axons of interneurons.
what is the function of the spinal cord?
impulse propagation from the peripheral nervous system to the brain and from the brain to the various effectors in the body
what are spinal meninges?
Three layers of connective tissue protect and cushion the spinal cord in the vertebral column and are continuous with the cranial meninges that enclose the brain.
what are the three layers of connective tissue in the spinal meninges?
dura, arachnoid, and pia mater
what is dura mater?
The superficial layer is composed of dense irregular connective tissue and is the toughest and most protective layer of the meninges.
what is the arachnoid mater?
The middle layer is composed of collagen and elastic fibers.
what is the subdural space?
Between the dura mater and arachnoid mater is the subdural space which is filled with interstitial fluid
what is the pia mater?
The deepest layer of the meninges adheres to the spinal cord. This layer contains many blood vessels that nourish the tissues of the underlying spinal cord
what is the subarachnoid space?
The space between the arachnoid and the pia mater is called the subarachnoid space and is filled with cerebrospinal fluid
what is the epidural space?
the cavity between the bone of the vertebral column and the dura mater, and is filled with fat and other connective tissues
what is the anterior horn of the spinal cord?
contain somatic motor nuclei; provide nerve impulses for contraction of skeletal muscles
what is the posterior horn of the spinal cord?
contain axons of incoming sensory neurons , cell bodies & axons of interneurons
what are spinal nerves?
paths of communication btw spinal cord & specific regions of the body, 31 pairs w/ each pair arising from a spinal segment
what is the central canal of the spinal cord?
spaces in the spinal cord filled w/ cerebrospinal fluid; protect & nourish the brain & spinal cord
what are nerve roots?
are two bundles of axons connecting each spinal nerve to a segment of the cord by even smaller axons (rootlets)
what is the anterior root of the spinal cord?
contain axons of motor neurons; conduct nerve impulses from CNS to effectors (muscles & glands)
what is the posterior root in the spinal cord?
contain ONLY sensory axons; conduct nerve impulses from sensory receptors in skin, muscles & internal organs into CNS
what is ganglia in the spinal cord?
posterior root swelling, containing cell bodies of sensory neurons
what is the anterior median fissure in the spinal cord
wide groove on the anterior (ventral) side
what is the posterior median sulcus on the spinal cord?
narrow fissure on the posterior ( dorsal ) side
what is the filum terminale in the spinal cord?
arises from Conus medullaris extension of the pia mater that extends inferiorly & infuses w/ arachnoid, and dura mater; anchors spinal cord to coccyx
what is a nerve?
a bundle of axons from multiple neurons
where do spinal nerves emerge from?
from the spinal cord as two distinct roots; anterior and posterior roots
what are mixed nerves?
nerves that have both sensory and motor functions
what is the anterior rami?
After leaving the spinal column, the anterior spinal nerves divide into several branches
what is a plexus?
The anterior rami, except for those of the thoracic spinal nerves, often form a complex network of motor nerves. These nerve networks contain axons from neighboring spinal nerves and innervate specific areas of the body
what is a reflex?
rapid, automatic sequences of actions that occur in response to a stimulus
what is a reflex arc?
the route an impulse takes to produce a reflex action.
what are the components to a reflex arc?
the sensory receptor, a sensory neuron, an integrating center, a motor neuron and the effector.
what is an autonomic or visceral reflex?
A reflex that results in secretion by a gland or in the contraction of smooth or cardiac muscle. Reflexes mediated through the autonomic nervous system regulate body functions such as digestion, elimination, blood pressure, salivation and sweating
what are somatic reflexes?
a type of reflex which results in the contraction of skeletal muscles
what is a reflex action?
rapid, autonomic sequences of actions that occur in response to a stimulus → pupil of eye constricts when light stimulates eye
what is a receptor?
distal end of a sensory neuron (dendrite) or an associated sensory structure that responds to a specific stimulus by producing a graded potential (generator potential)
→ growth factor receptor
what is a sensory neuron?
nerve impulses propagate from the sensory receptor along the axon of the sensory neuron to the axon terminals, relay neurons send nerve impulses to the area of the brain that allows conscious awareness of the reflex that occurred → sensory neurons on fingertips (feel hot surface)
what is the integrating center?
single synapse between a sensory neuron & motor neuron with the CNS
↳ y synapse= monosynaptic reflex arc
↳ 2 or more synapses= polysynaptic reflex arc
→hypothalamus (in brain) signals an effector
what is a motor neuron?
impulses triggered by the integrating center propagate out of the CNS along a motor neuron to the part of the body that will respond
→ motor neurons in spinal cord connect to muscles, glands & organs
what is an effector?
the part of the body that responds to the motor nerve impulse
↳ the action = reflex
↳ smooth , cardiac or gland = autonomic reflex
↳ Skeletal = somatic reflex
→ muscles ( when contracting)
