Lecture Test 6

• Nerve # 1
• Type: Sensory
• Function: Olfaction (smell)

• Nerve #2
• Type: Sensory
• Function: Vision (sight)

• Nerve #3
• Type: Motor
• Function: Moves eyeball & eyelid, focuses eye, pupil diameter (does sensation of eyeball proprioception.)

• Nerve #4
• Type: Motor
• Function: Moves eyeball (& sense of eyeball proprioception.)

• Nerve #5
• Type: Mixed (sesnory & motor)
• Function: Motor= muscles of mastication
• 3 sensory branches: 1.ophthslmic- touch from scalp to nose
• 2. maxillary- touch to nasal mucosa, upper palate
• 3. mandibular- touch to ant. 2/3 of tongue, teeth, chin

• Nerve #6
• Type: Motor
• Function: Move eyeball (& sense of eyeball proprioception.)

• Nerve #7
• Type: Mixed
• Function: Motor-muscles of facial expression
• Sensory= tastebuds of ant. 2/3 of toungue

• Nerve #8
• Type: Sensory
• Function: Hearing & equilibrium

• Nerve #9
• Type: Mixed
• Function: Motor=swallowing &salivation
• Sensory= taste of post. 1/3 of toungue

• Nerve #10
• Type: Mixed
• Function: Motor= viscera of thoracic & abdominal cavities
• Sensory= proprioception (sense of position/space) of truck

• Nerve #11
• Type: Motor
• Function: voluntary throat muscles for swallowing (proprioception)

• Nerve #12
• Type: Motor
• Function: moves tongue for speech (& sense of proprioception)

Enlarged area of spinal cord to accommodate additional nerves to upper limbs.

Enlarged area of spinal cord to accommodate additional nerves to lower limbs.

Nerves that exit the spinal cord at the sacrum.

piece of C.T. that holds the spinal cord to length.

hole in the center of the spinal cord through which CSF flows

contains somata of somatic & visceral sensory neurons (sensory nucles)

contains visceral motor nuclei

contains somatic motor nuclei

unmyelinated axons that cross the spinal cord.

myelinated axons that cross the spinal cord.

• contain myelinated axons that ascend or descend the spinal cord.
• **Neurons that share common origins & destinations travel through the same column.

contains axons of sensory neurons entering the spinal cord.

contains the somata of sensory neurons entering the spinal cord

contains axons of motor neurons exiting the spinal cord.

31 pairs, all are mixed (sensory & motor)

Covers the entire nerve

Divides the nerve into bundles called fascicles

surrounds individual axons within the fascicles

• All nerurons carrying sensory info. from the skin, muscles, and viscera of the back enter the spinal nerve through the dorsal ramus.
• Somatic Sensory Neurons synapse in the somatic sensory nucleus near edge of the posterior gray horn.
• Visceral sensory neurons synapse in the visceral sensory nucleus which lies deeper in the posterior gray horn.

• All neurons carrying sensory info. from the skin, muscles, and viscera of the front, sides, and limbs enter the spinal nerve through the ventral ramus.
• Somatic sensory neurons synapse in the somatic sensory nucleus near the edge of the posterior gray horn.
• Visceral sensory neurons synapse in the visceral sensory nucleus which lies deeper in the posterior gray horn.

All neurons from viscera of the thoracic and abdominopelvic cavities pass through an autonomic nerve then the white ramus of the rami communicantes and then into the spinal nerve, the dorsal root, and then into the visceral sensory nucleus.

• Made up of white (myelinated) and the gray (unmyelinated) rami.
• These branches carry visceral sensory info. from the thoracic and abdominopelvic cavities into the spinal cord.
• They also can carry visceral (autonomic) motor info. from the spinal cord to the viscera of the thoracic and abdominal cavities.

• Motor commands leaving the spinal cord & innervating viscera of the posterior body wall exit the visceral motor nucleus in the lateral gray horn through a myelinated preganglionic fiber.
• Passes through the white ramus & synapses on a ganglionic neruron in the autonomic ganglion.
• The ganglionic neuron will send its unmyelinated postganglionic fiber out the gray ramus and out the dorsal ramus.

• Motor commands leaving the spinal cord & innervating viscera of the anterior & lateral body wall or the limbs exit the visceral motor nucleus in the lateral gray horn through a myelinated preganglionic fiber.
• It then passes through the white ramus & synapses on a ganglionic neuron in the autonomic ganglion.
• The ganglionic neuron will send it's unmyelinated postganglionic fiber out of the gray ramus and out the ventral ramus.

• Motor commands leaving the spinal cord & innervating viscera of the thoracic cavity exit the visceral motor nucleus in the lateral gray horn through a myelinated preganglionic fiber.
• It then passes through the white ramus and then synapses on a ganglionic neuron in the autonomic ganglion.
• The ganglionic neuron will send its unmyelinated postganglionic fiber out the sympathetic nerve & synapses on a distant visceral oragn.

• Motor commands leaving the spinal cord & innervating viscera of the abdominopelvic cavity exit the visceral motor nucleus in the lateral gray horn through a myelinated preganglionic fiber.
• It then passes through the white ramus and then synapses on a ganglionic neuron in the intramural ganglion.
• The ganglionic neuron will send its unmyelinated postganglionic fiber into the visceral organ.

All motor neurons carryng somatic motor commands to the skin and muscles of the back leave the spinal nerve and exit through the dorsal ramus.

All motor neurons carrying somatic motor commands to the skin and muscles of the front, sides, and limbs leave the spinal nerve and exit through the ventral ramus.

A network of interwoven nerves that innervate a specific region of the body.

• Innervates muscles of the neck.
• Also contains the phrenic nerve which innervates the diaphragm.

• Innervates shoulder girdle and arm.
• The radial nerve controls extensor muscles and the ulnar nerve innervates the flexor muscles of the forearm.
• E.R.
• F.U.

• Innervates the pelvis.
• Includes the femoral nerve which innervates the skin of the inner thigh.

Innervates the leg. The sciatic nerve innervates some of the thigh and the lower leg. The sacral plexus includes the pudendal nerve which innervates the anal and urethral sphincters.

• Neural reflexes are automatic motor responses to specific stimuli that help maintain homeostasis and protect the body from physical damage.
• Reflexes are eventually processed in the brain, but are designed to bypass the brain in the short-term to protect the body.
• The pathway of a neural reflex is called a reflex arc.

• 1. Stimulus/Activation of Sensory Receptor-A receptor (intero- or exteroreceptor) detects a harmful stimulus.
• 2. Activation of Sensory Neuron-The receptor causes an action pot. in the sensory neuron which then passes the info. to the CNS through a sensory pathway.
• 3. Information Processing-In the CNS the sensory neuron synapses on motor neurons & stimulates them to threshold.
• 4. Activation of Motor Neuron-An action pot. in the motor neuron exits the ventral root towards an effector (muscle.)
• 5. Response at Effector-The motor neuron stimulates an effector (skeletal or smooth mus.) & the appropriate feedback (motor response) is exhibited.

Inborn reflexes such as suckling, blinking, & chewing.

Learned reflexes such as walking, balancing, riding a bike.

Reflexes involving cranial nerves like auditory and visual reflexes.

Reflexes involving spinal nerves like withdrawl reflexes.

Reflexes involving skeletal muscles that move the body.

Reflexes involving smooth or cardiac muscle (autonomic functions.)

• First Order Neuron- usually bipolar neurons & extend their axon through the dorsal root and the soma is in the dorsal root ganglion. They then synapse on the second order neuron in the appropriate sensory nucleus in the posterior gray horn.
• Second Order Neuron- soma in the posterior gray horn & extends it's axon up the spinal cord through an ascending tract, usually crossing over at some point, & synapsing on the third order neuron in the thalamus.
• Third Order Neuron- soma in the thalamus & extends it's axon through the cerebral nuclei and synapses on the cerebral cortex, usually in the primary sensory cortex.

All sensory tracts coursing through the spinal cord must go up or ascend the spinal cord toward the brain and are therefore called ascending tracts.

• Upper Motor Neuron- soma in the brain (cerebrum or cerebellum) (usually the primary motor cortex) & extends an axon down to the brain stem for cranial nerves, or down to the spinal cord to the anterior gray horn for spinal nerves.
• Lower Motor Neuron- soma in the anterior gray horn (or medulla for cranial nerves) and extends it's axon out the spinal nerve to the appropriate effector (muscle.)

Motor pathways begin in the brain, descend down the spinal cord to the appropriate level and then out to the peripheral effector, they are referred to as descending tracts.

• begin with the word spino-
• ex. spinothalamic tract

• end in the word -spinal
• ex. corticospinal

• Lateral & Anterior Spinothalamic Tracts- extend from various levels of the spinal cord & carry sensations of pain, temperature, and crude touch to the thalamus.
• Posterior & Anterior Spinocerebellar Tracts- extend from spinal cord and carry sensations for proprioception (sense of position/space) to the cerebellum.

• Lateral & Anterior Corticospinal Tracts- extend from the primary motor cortex through the brain stem and to the somatic motor nuclei of the anterior gray horns.
• Corticobulbar Tracts- extend from the primary motor cortex out the cranial nerves that control movement of the eyes, mandible, face, and some muscles of the neck and pharynx.
• Vestibulospinal Tracts- extend from the medulla to the anterior gray horns and regulate involuntary control of balance and muscle tone.
• Tectspinal Tracts- extend from the midbrain (tectum) & extend out specific cranial nerves for eye movement, as well as the anterior gray horns for head, neck, and arm movement for visual and auditory reflexes.

• entirely motor & controls conscious voluntary (skeletal) muscle movement.
• somatic motor neurons extend from the anterior gray horns to the skeletal muscle without synapsing on the way.

• entirely motor & controls subconscious visceral effectors (smooth muscle of the visceral organs like digestive and urinary systems, and cardiac muscle of the heart.)
• autonomic motor neurons extend from the lateral gray horns through a preganglionic fiber to an autonomic ganglion.
• At the autonomic ganglion they then synapse on another motor neuron (ganglionic neuron) that extends its postganglionic fiber from the ganglion to the effector (smooth or cardiac muscle.)

• FIGHT OR FLIGHT
• active during stress and exercise (or high levels of skeletal muscle activity) & increases heart rate, breathing rate, & blood flow to the brain, heart, & skeletal muscles.
• sympathetic preganglionic fibers are short, pass through the white ramus, & synapse near the spinal cord and release ACh.
• postganglionic fiber is very long & extends from the sympathetic ganglion to the effector where it releases norepinephrine (adrenalin.)

• REST AND DIGEST
• active during low stress (low levels of skeletal muscle activity) & decreases energy consumption.
• parasympathetic preganglionic fibers are long and release ACh at the ganglion.
• the ganglion is located in the wall of the visceral organ and is called an intramural ganglion.
• the postganglionic fiber is very short and extends from the intrmural ganglion to the effector where it releases ACh.