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Nervous System P.2 Eyvette Villalobos - Coggle Diagram
Nervous System P.2 Eyvette Villalobos
Major functions of the nervous system
Motor function: nerve impulses(CNS) are conducted along motor neurons to effectors
Sensory function; information travels from receptors to sensory neurons, which transport information into the CNS
Integrative function; coordination of sensory information in the CNS, procession of this information is the basis for decision-making
Major divisions and subdivisions of the nervous system
Central nervous system (CNS); consists of the brain and the spinal cord. responsible for integration of information and decision making
Peripheral nervous system (PNS); consist of the cranial and spinal nerves which connects the CNS to the rest of the body
Somatic nervous system; controls voluntary skeletal muscles
Autonomic nervous system; controls involuntary effectors (smooth and cardiac muscles and glands)
Tissues
A neuron contains a cell body, tubular cytoplasm-filled dendrites, and a tubular, cytoplasm-filled axon
The cell body (soma) contains major organelles including nucleus
Dendrites conduct impulses toward the cell body; they are short and branching, and they provide the receptive surface for communication with other neurons
The axon conducts impulses away from the cell body; it arises from a thickening extending from the cell body, called the axon hillock
Classification of neurons
Interneurons
Multipolar neurons lying within the CNS that form links with other neurons
Motor (efferent) neurons
Multipolar neurons that conduct impulses from the CNS to peripheral effectors (muscles or glands)
Sensory (afferent) neurons
conduct impulses from peripheral receptors to the CNS: usually unipolar, although some are bipolar
Multipolar neurons
Have many dendrites and one axon arising from their cell bodies: most neurons with cell bodies in CNS (interneurons and motor neurons) are multipolar
Bipolar neurons
Have 2 processes extending from the cell body, a dendrite and an axon; found in some of the special senses, such as the eyes, nose and ears
Unipolar neurons
Have onyl 1 process extending from the cell body; outside the cell body, it soon splits into 2 parts that function as 1 axon; the peripheral process has dendrites near a peripheral body part, and the central process runs into the CNS; the cell bodies are found in ganglia outside the CNS; these are sensory neurons
Connective Tissue Coverings
Epineurium: Outer covering of a nerve
Perineurium: covering around fascicles (bundles) of nerve fibers
Endoneurium: covering around individual nerve fibers (axons)
Major parts and functions of the brain
Surrounded by 3 membranes called meninges that lie between the skull bones; the meninges consist of the dura mater, arachnoid mater, and pia mater
Dura mater: outermost layer of meninges and its very thick
Arachnoid mate; the middle layer of meninges
Pia mater; the innermost layer of the meninges
Major parts and functions of the spinal cord
The spinal cord is surround by 3 membranes called meninges that lie between the vertebrae and the soft CNS tissues
The meninges consist of the dura mater, arachnoid mater, and pia mater
The spinal cord begins at the base of the brain, the spinal cord begins at the base of the brain, the spinal cord consists of 31 segments, each of which connects to a pair of spinal nerves
functions
Transmit impulses to and from the brain and to house spinal reflexes
Ascending tracts carry sensory information to the brain; descending tracts carry motor information from brain to muscles or glans
Action potential & the Nerve Impulse
An excitatory stimulus opens chemically-gated Na+ channels
Na+ ions flow into cell due to concentration gradient causing inside of neuron to become less negative
Threshold stimulis potential changes from -70 to -55 mV
Upon reaching threshold potential voltage-gated Na+ channels open changing charge to about +30 mV this is called an action potential
Cranial nerves
Twelve pairs of cranial nerves arise from the underside of the brain, the first pair arises from the cerebrum, and the second pair from the thalamus, but most arise from the brainstem. The 12 pairs are designated by number and name from superior to inferior
1.) Olfactory; sensory fibers conduct impulses associated with the sense of smell
2.) Optic: sensory, fibers conduct impulses associated with the sense of vision
3.) Oculomotor: primarily motor, motor fibers conduct impulses to muscles that raise eyelids, move eyes, and adjust the amount of light entering the eyes and focuses the lenses.
4.) Trochlear: primarily motor, motor fibers conduct impulses to muscles that move the eyes
5.) Trigeminal: mixed, had 3 subdivisions, opthamalic decision, maxillary division, mandibular division
6.) Abducens: primarily motor, motor fibers conduct impulses to muscles that move the eyes
7.) Facial: mixed, sensory fibers conduct impulses associated with taste receptors of the anterior tongue motor fibers conduct impulses to muscle of facial expressions, tear glands and salivary glands
8.) Vestibulochlear: sensory, is divided into 2 subdivisions, the vestibular branch and the cochlear branch
9.) Glossopharyngeal: mixed, sensory fibers conduct impulses from the pharync, tonsils, posterior tongue and carotid aritieris
10.)Vagus: Mixed, somatic motor fibers conduct impulses to muscles associated with speech and swallowing
11.) Accessory: primarily motor, divided into the cranial and spinal branch. Motor fibers conduct impulses to muscle of the soft palate
12.) Hypoglossal: primarily motor, motor fibers conduct impulses to muscles that move the tongue
Spinal nerves
31 pairs of spinal nerves arise from the spinal cord; all except the first pair are mixed nerves; 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves and 1 pair of coccygeal nerves
The main branches of spinal nerves, except in the thoracic region, from networks called plexuses
Cervical plexuses (C1-C4); lie on either side of the neck; supply muscles and skin of the neck; include the phrenic nerves, which control the diaphragm
Brachial plexuses (C5-T1): arise from lower cervical and upper thoracic nerves which supply muscle and skin of arms forearms and hands; lead into the upper limbs; include the musculocutaneous, ulnar, median, radial, and axillary nerve
Lumbosacral Plexuses (L1-S4); arise from the lower spinal cord: supply muscles and skin of the lower abdomen, external genitalia, buttocks and legs
Neurotransmitters
chemical messenger that convey messages through space. They send electrical impulses from a neuron to another cell. Neurotransmitters are released in response to the nerve impulse
Compare & contrast the autonomic nervous system
Autonomic nervous system helps maintain homeostasis, responds to emotional stress and prepares the body for strenuous activity
The autonomic NS portions of the PNS that functions constantly and independently without concious effot
The ANS controls visceral motor functions of smooth muscle, cardiac muscle and glands
Sympathetic division: active in conditions of stress or emergency
Parasympathetic division: active under normal, restful conditions
Reflex arc (major parts & functions)
A sensory receptor that detects changes
A sensory neuron, that detects changes
A sensory neuron, that carries the information from a receptor toward the CNS
An interneuron in the CNS
A motor neuron that carries a command to effectors
an effector that responds to the change
Reflec arcs provide the basis for involuntary actions called reflexes