7.1 - Nervous system | Conjunto de Fichas

Pregunta	Respuesta
Three basic functions of NERVOUS TISSUE	- sensing changes with sensory receptors (fullness of stomach or sun on face) - interpreting & remembering those changes - reacting to those changes with effectors (muscular contractions & glandular secretions)
Ganglia: definition	small masses of nervous tissue, consisting primarily of neuron cell bodies
Ganglia: location	Outside of the brain & spinal cord
Enteric plexuses: definition	extensive network of neurons that help regulate the digestive system
Enteric plexuses: location	in the walls of organs of the gastrointestinal tract
Sensory receptor: definition	structure of the nervous system that monitors changes in the external or internal environment
somatic nervous system: sensory neuron functions	convey info to the CNS from: 1. somatic receptors in the HEAD, BODY WALL, and LIMBS 2. receptors for the special SENSES of vision, hearing, taste, and smell
somatic nervous system: motor neuron functions	conduct impulses from the CNS to the SKELETAL MUSCLES only. Can be consciously controlled. The action of this part of the PNS is VOLUNTARY.
Autonomic nervous system: Sensory neuron functions	convey info from autonomic sensory receptors, located primarily in visceral organs such as stomach and lungs, to the CNS
Autonomic nervous system: motor neuron functions	conduct nerve impulses from the CNS to smooth muscle, cardiac muscle, and glands.
What are the 2 branches of the motor part of the ANS?	The SYMPATHETIC division and the PARASYMPATHETIC division. With a few exceptions, effectors receive nerves from both divisions, and usually the 2 divisions have opposing actions. Eg. sympathetic increase heart rate; parasympathetic slow it down.
Sensory neurons of the ENS: functions	monitor chemical changes within the GI tract as well as the stretching of its walls
Enteric Nervous System: motor neuron functions	Govern: 1. contraction of GI tract smooth muscle to propel food through the GI tract 2. secretions of the GI tract organs such as acid from the stomach 3. activity of GI tract endocrine cells, which secrete hormones.
Peripheral Nervous System PNS: function	Connects CNS to muscles, glands & all sensory receptors
Explain the electrical excitability of neurons	The ability to respond to a stimulus and convert it into an action potential
Stimulus: definition	any change in the environment that is strong enough to initiate an action potential
Action potential (nerve impulse): definition	an electrical signal that travels along the surface of the membrane of a neuron
What generates an action potential?	The movement of ions such as sodium and potassium between interstitial fluid and the inside of a neuron
Nissl bodies: definition	Prominent clusters of rough endoplasmic reticulum surrounded by free ribosomes
Ribosomes: function	Protein synthesis
Nissl bodies: function	Synthesises proteins which are used: - to replace cellular components - as material for growth of neurons - to regenerate damaged axons in PNS
Neurofibrils	Bundles of intermediate filaments located in the cytoskeleton that provide the cell shape & support
Microtubules	Assist in moving materials between the cell body and axon
Lipofuscin	A pigment that occurs as clumps of yellowish brown granules in the cytoplasm of aging neurons. It is a product of lysosomes.
Dendrites	The receiving or input portions of a neuron. The plasma membranes of dendrites contain numerous receptor sites for binding chemical messengers from other cells.
Axon: function	Propagates nerve impulses toward: - another neuron - a muscle fiber - a gland cell
Axon hillock	Cone shaped elevation where the axon joins to the cell body.
Initial segment	The part of the axon closest to the axon hillock.
Axon contains:	Mitochondria, microtubules & neurofibrils Because rough ER is not present, protein synthesis does not occur in axon.
Synapse	The site of communication between two neurons or between a neuron and an effector cell
Slow axonal transport	Conveys new axoplasm in one direction only - from cell body towards axon terminals. Movement at 1-5mm per day.
Fast axonal transport	Uses proteins that function as "motors" to move organelles & materials along the surfaces of microtubules, in both directions, for use or for recycling. Movement is 200-400mm per day
Fast axonal transport & disease	Harmful agents such as tetanus toxin and the viruses that cause rabies, herpes & polio, all enter the neuron at the axon terminal and are moved to the cell body via fast axonal transport. More serious if wound is in head or neck due to shorter transit time.
Unipolar neurons: development	- Begin in the embryo as bipolar - During development, the dendrites & axon fuse together & become a single process
Unipolar neurons: Dendrites function	- sensory receptors that detect a sensory stimulus such as a touch, pressure, pain or thermal stimuli
Unipolar neurons: cell body location	In the ganglia of spinal & cranial nerves
Sensory (afferent) neurons	Transport sensory info from skin, muscles, joints, sense organs & viscera to the CNS
Motor (efferent) neurons	Send motor nerve impulses AWAY from the CNS, to muscles & glands in the PNS, via cranial or spinal nerves
Interneurons (association neurons)	Connect sensory neurons to motor neurons within the CNS - make up 90% of neurons in body
Myelination: definition	When axons are surrounded by a multilayered lipid & protein covering (myelin sheath)
Myelination: function	The sheath electrically insulates the axon & increases the speed of nerve impulse conduction.
Neurolemma: location	Found only around axons in the PNS
Neurolemma: function	When an axon is injured, the neurolemma aids regeneration by forming a regeneration tube that guides & stimulates regrowth of the axon
Location of cytoplasm & nucleus in schwann cells	Forms outermost layer of neurolemma (inner portion being the myelin sheath)
Gray matter contains...	- nerve cell bodies - dendrites - axon terminals - unmyelinated axons - neuroglia
White matter contains...	Myelinated processes (white in colour)
Gray matter locations	- H shaped inner core in the spinal cord, surrounded by white matter - thin outer shell covers the surface of the brain & also found in clusters called nuclei inside the CNS
White matter locations	- surrounds a H shaped inner core of gray matter in the spinal cord - inner core of the brain, surrounded by gray matter

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7.1 - Nervous system

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