Name the 12 cranial nerves
olfactory optic oculomotor trochlear trigeminal abducens facial vestibulocochlear glossopharyngeal vagus accessory hypoglossal
Describe the functions of the optic nerve
- associated with sense of vision
- its a brain tract because it develops as an outgrowth of the brain
Describe the oculomotor nerve
- rasies eyelids
- moves eyes
- adjusts the amount of light entering
- focuses lenses
- moves the eyeball
- moves the eyeball by using 4 extrinsic muscles, inferior oblique, superior, inferior and medial rectus muscles
- parasympathetic motor fibers reach the spincter pupillae to cause the pupil to constrict
- cillary muscle controls lense shape
What functions can the oculomotor nerve do?
- raise eyelids
- adjusts the amount of light entering
- focuses lenses
- moves eyeballs
Name the 4 extrinsic muscles that work with the oculomotor
inferior oblique
superior rectus muscle
inferior rectus muscle
medial rectus muscle
Describe the glossopharyngeal nerve
- motor fibers transmit impulses to the pharynx muscles used in swallowing, and to the salivary glands
- innervate the tongue
-sensory fibers transmit impulses from the pharynx, tonsils, posterior tongue + cartoid arteries
Describe the vagus nerve
somatic motor fibers- transmit impulses to muscles used for speech and swallowing
- autonomic moor fibers transmit impulses to the heart, smooth muscles and thoracic and abdominal glands
- sensory fibers transmit impulses from the pharynx, larynx, esophagus, viscera of the thorax and abdomen
Reflexes can be either ____ or ____
inborn (intrinsic) or learned (acquired)
Describe inborn reflexes
- rapid
- predictable motor responses to stimuli
Describe learned reflexes
developed from repetition over time
Name the 5 essential components to a reflex arch
- receptor
- sensory neuron
- integration center
- motor neuron
- effector
Spinal reflexes can be either ___ or ___
somatic or autonomic
What do somatic spinal reflexes do?
activate skeletal muscle
What do autonomic (visceral) spinal reflexes do?
activate visceral effectors (smooth muscle, cardiac muscle and glands)
What are spinal reflexes
somatic reflexes controlled by the spinal cord, often without direct involvement of higher brain centers
If the spinal cord is transected what may happen as a result?
spinal shock
Why are tests of somatic reflexes carried out? What do they test?
nervous system functioning
Explain dual innervation of the ANS
- helps to balance the sympathetic + parasympathetic divisions
- via dual innervation the divisions counter balance each other keeping body systems functioning normally
- both divisions generally cause opposite effects on the same visceral organs
- cooperative dual innervations involve the fibers of both systems working together to produce a response
- dual innervations may also be antagonistic of complimentary
Describe the arrangement of sympathetic neurons + ganglia
- all preganglionic fibers arise from cell bodies of preganglionic neurons in the spinal cord T1-L2 (thoracolumbar)
- after leaving the spinal cord via the ventral root, preganglionic sympathetic fibers pass through a white ramus communicans to enter adjoining sympathetic trunk ganglion that forms part of the sympathetic trunk
- the sympathetic trunks consist of the sympathetic ganglia and fibers that run from one ganglion to another
- sympathetic fibers arise only from the thoracic and lumbar spinal cord segments
- once a preganglionic axon reaches a trunk ganglon, it can either synapse at the same level, higher, lower or in a distant collateral ganglion
Describe the arrangement of parasympathetic neurons + ganglia
- also called craniosacral division, preganglionic fibers emerge from opposite ends of the CNS
- The axons then synapse with postganglionic neurons in the terminal ganglia
- short postganglionic axons emerge from the terminal ganglia to synapse with nearby effector cells
Distinguish between sympathetic + parasympathetic divisions of the ANS
Sympathetic
- mobilises body during activity
- emergencies, excitement, exercise
- thorocolumbar origins
- short preganglionic fibers, long postganglionic fibers
- ganglia lie close to the spinal cord
parasympathetic
- promotes maintenance + conserves energy
- digestion, defecation + diuresis
- craniosacral origins
- long preganglionic fibers, short post ganglionic fibers
- ganglia are located in the visceral effector organs
The sympathetic and parasympathetic divisions of the ANS work together to do what?
balance homeostasis
