LO 5
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In order to function, most tissue, structures, and organs have ___________, a supply of nerves to the body part.
innervation
What are the 2 types of nerves?
• Afferent (sensory) • Efforent (motor)
Describe resting potential
• The plasma membrane of a neuron(like all other cells) has an unequal distribution of ions and electric charges between the two sides of the membrane. • The fluid outside of the membrane has a positive charge; the fluid inside has a negative charge. • This charge difference is a resting potential and is measured in millivolts.
Describe an action potential
• The rapid depolarization of the cell membrane results in an action potential, which then causes the propagation of the nerve impulse along the membrane. • An action potential is a temporary reversal of the electric potential along the membrane for a brief period (less than a millisecond).
After passage of the action potential, there is a brief period—the __________—during which the membrane cannot be stimulated.
refractory period
Describe anasthesia
• Anesthesia is the loss of feeling or sensation resulting from the use of certain drugs or gases that serve as inhibitory neurotransmitters. • Many local anesthetic agents such as lidocaine, as used in dentistry, mimic inhibitory neurotransmitters by decreasing sensory neurons’ ability to generate an action potential, thus producing localized anesthesia.
What are the 3 layers of the meninges?
• Dura mater - outermost membrane (surrounds and supports the large venous channels (dural sinuses) carrying blood from the brain toward the heart such as the cavernous sinus in the head.) • Arachnoid mater - middle layer (underneath is the subarachnoid space that contains the cerebrospinal fluid) • Pia mater - innermost membrane (delicate and highly vascularized)
What are the major divisions of the brain?
• Cerebrum - largest; two hemispheres • Cerebellum - 2nd largest • Brainstem - divisions: medulla, pons& midbrain • Diencephalon: includes the thalamus (central relay point for incoming nerve impulses) and hypothalamus (regulates homeostasis - hunger, thirst, body temp., water balance, BP)
The ___________ is closest to the spinal cord
medulla
The ___________ connects the medulla with the cerebellum and with higher brain centers
pons
The ___________ includes relay stations for hearing, vision, and motor pathways.
midbrain
The __________ runs along the dorsal side of the body and links the brain to the rest of the body.
spinal cord
The efferent division of the PNS is divided into ____________
• the somatic nervous system: includes all nerves controlling the muscular system and external sensory receptors. (is also part of the afferent) • autonomic nervous system.
Autonomic fibers are _________ nerves
efferent
The autonomic nervous system always occur in two nerve chains, describe this.
The first nerve carries autonomic fibers to a ganglion, where they terminate near the cell bodies of the second nerve.
All twelve paired cranial nerves are connected to the brain at its base and pass through the skull by way of __________ or __________.
• fissures • foramina
Describe the olfactory nerve (I)
• Afferent nerve • Transmits smell from the nasal mucosa to the brain • Enters the skull through the perforations in the cribriform plate of the ethmoid bone to join the olfactory bulb in the brain.
Describe the optic nerve (II)
• Afferent nerve • Transmits sight from the retina of the eye to the brain • Enters the skull through the optic canal of the sphenoid bone on its way from the retina
Describe the oculomotor nerve (III)
• Efferent nerve • Eye muscles that move the eyeball. • Lies in the cavernous sinus and exits the skull through the superior orbital fissure of the sphenoid bone.
Describe the trochlear nerve (IV)
• Efferent nerve • One eye muscle • Runs in the cavernous sinus and exits the skull through the superior orbital fissure of the sphenoid bone.
Describe the trigeminal nerve (V)
• Efferent: muscles of mastication & other cranial muscles • Afferent: face & head skin, teeth, oral cavity, most general sensation of the tongue • Has 2 roots: sensory and motor. • The sensory root of the trigeminal nerve has three nerve divisions: ophthalmic, maxillary, and mandibular. It is the largest.
Describe the functions of each division of the trigeminal nerve (V)
• The ophthalmic nerve (division) provides sensation to the upper face and scalp. • The maxillary and mandibular nerves (divisions) provide sensation to the middle and lower face, respectively. • Each of the three nerves or divisions of the sensory root of the trigeminal nerve enters the skull in one of three different locations in the sphenoid bone.
The ophthalmic nerve or division of the trigeminal nerve enters through the _________.
superior orbital fissure
The maxillary nerve or division of the trigeminal nerve enters by way of the ___________.
foramen rotundum