nerves Flashcards
the nervous system is formed of
- central nervous system
- peripheral nervous system
- autonomic nervous system
The nerve cell includes
- the cell body: containing the nucleus
- processes 1. axon: single long process which carries the nerve impulse away from the cell body — outside the CNS the axons run in groups forming nerves 2. dendrites: short multiples processes that carry the impulse towards the cell body
synapse
site where impulses pass from one neuron to another by the contact of one of the axon of one and the dendrites of another
The CNS
brain and spinal cord
- protected by bones, fluid, and meninges
- the brain is protected by skull whereas the spinal cord is protected by the vertebrae column
- the fluid is called cerebrospinal fluid
- the meninges are covering membrane are the pia, archanoid, and dura matter (subarchanoid [has fluid] and subdura between the layers respectively)
subdivisions of the brain
- cerebrum — consists of two cerebral hemispheres and the diencephalon (thalamus and hypothalamus)
- brain stem — consists of midbrain, pons, medulla oblongata
- cerebellum — consists of two cerebellar hemispheres
cross section of the brain
- outer gray matter: dark areas mainly on the surface of the cerebrum (cerebral cortex) — contains cell bodies of nerve cells
- inner white matter: light areas in the center of cerebrum, it contains axons of nerve cells (nerve fibers) — the fibers run inside the CNS as bundles or tracts
spinal cord
downward continuation of the medulla oblongata at the foramen magnum. it has central narrow cavity called the central canal. divided into cervical, thoracic, lumbar, sarcal, and coccygeal segments.
cross section of spinal cord
- outer layer of white matter: contains ascending fibers (sensory tracts) that carry sensations to the brain and descending fibers (motor tracts) that carry higher motor orders to the brain
- inner layer of gray matter: neurons in H-shaped area — two anterior limbs are termed true anterior horns (motor) and two posterior limbs are the posterior horns (sensory) — the horizontal connecting region is known as the grey commissure through runs the central canal — lateral horn is for autonomic nervous system
peripheral nervous system
cranial (12 pairs and sensory gangalia) and spinal nerves (31 pairs and dorsal foot gangalia)
Cranial nerves
- olfactory
- optic
- oculomotor
- trochlear
- trigemenial
- abducent
- fascial
- vestibulo-cochlear
- glossopharyngeal
- vagus
- accessory
- hypoglossal
spinal nerves
31 pairs — 8 cervical, 12 thoracic, 5 lumbar, 5 sarcal, 1 coccygeal
(study structure of spinal nerve)
autonomic nervous system
- control of involuntary functions of smooth muscles, heart and glands. they are antagonistic and work to maintain homeostasis
two sets of neurons for ANS
- preganglionic neurons — they carry impulses from the cns to the ganglia outside the cns
- postganglionic neurons — they carry impulses from the gangalia to smooth muscles and glands
they connect by making synapses
sympathetic fibers
- pregangolionic fibers— arise from neurons of the lateral horns of the grey matter of the spinal cord of all thoracic segments and first lumbar segments
- postgangolionic fibers are the axons of cell bodies of the sympathetic ganglia. the fibers leave the gangalia as grey rami communicate to be distributed to their target organs
the parasympathetic system
- preganglionic fibers: they arise form cns at two sites 1-cranial nerves 10, 9, 7,3 2- (2,3,4th sarcal)
- parasympathetic ganglia; they are found close to the parts to be intervatted
- postganglionic fibers: axons of cell bodies leave the ganglia to their target organs
