PNS Flashcards
What routes do nerve impulses follow through the nervous system?
The nerve impulses follow routes through the nervous system called nerve pathways.
What do the simplest nerve pathways consist of?
A little more than two neurons that communicate across a single synpase
What is a reflex?
A relatively simple motor response that does not involve a large number of interneurons
What is another word for interneurons?
Association neurons
What is one example of a monosynaptic reflex?
The patellar or knee jerk reflex
What is a monosynaptic reflex use?
Uses one sensory (afferent) and one motor (efferent) neuron
What are most reflexes?
Most reflexes are polysynaptic
What does polysynaptic mean?
polysynaptical means involving more than two neurons
What do most reflexes involve?
Most reflexes involve the activity of interneurons in the brain and spinal cord
What happens in more complicated reflexes?
IN more complicated reflexes, impulses may travel up, down, transversely in the spinal cord
What happens when there are more synapses in the reflex pathway?
There is a synaptical delay in neural transmission at the synapses, and more time is required to illicit the reflex
What are reflexes mediated over?
Reflexes are mediated over simple nerve pathways called reflex arcs
What are the 5 essential components of reflex arcs?
Receptor, sensory neuron, integration center, motor neuron and effector
What is the receptor?
The receptor is at the end of a sensory neuron
What does the receptor react to?
The receptor reacts to the stimulus
What does the sensory neuron do?
The sensory neuron conducts nerve impulses along an afferent pathway towards the CNS
What does the integration center consist of?
The integration center consists of one or more synapses in the CNS
What does the motor neuron do?
The motor neuron conducts a nerve impulse along an efferent pathway from the integration center to an effector
What does a effector respond to if it is a muscle fiber?
An effector responds to the efferent impulses by contracting
What does a effector respond to if it is a gland?
If the effector is a gland it responds to the efferent impulses by secreting a product
What can reflexes be categorized into?
Reflexes can be categorized into subdivisions of the PNS (autonomic or somantic)
What are autonomic reflexes not subject to?
Autonomic reflexes are not subject to conscious control
What are autonomic reflexes mediated by?
Autonomic reflexes are mediated by the autonomic division of the nervous system
What do autonomic reflexes involve?
Autonomic reflexes usually involve the activation of smooth muscle, cardiac muscle (involuntary muscle) and glands
Are involuntary reflexes fast?
Involuntary reflexes are very fast and travel in milliseconds
What is the fastest impulse a involuntary reflex can reach?
A involuntary reflex can reach 320 miles per hour
What do somatic reflexes involve?
Somatic reflexes involve the stimulation of skeletal muscle
What does the stimulation of the somatic reflex involve?
It involves the somatic or voluntary division of the nervous system
Would motor nerves above an injured area may be unaffected?
Yes motor nerves above an injured area may be unaffected, where as motor nerves at or below the damaged area may be unable to perform the usual reflex activities
What is hyperflexia?
An exaggerated response resulting from damaged or diseased motor areas in the CNS
What is hypoflexia?
Hypoflexia is an inhibited response resulting from degeneration of nerve pathways, voluntary motor control, and other factors
What is the patellar tendon reflex or knee jerk reflex an example of
A monosynaptic stretch
Which division of the autonomic nervous system was active during the pupillary reflex?
The parasympathetic division was activated
Where are single lens eyes found in?
Squids and Humans
What are the 3 layers of the eye?
Sclera, Choroid, Retina
Muscles attach to which layer of the eye?
The Sclera
What is the sclera?
The outermost layer of the eye
Why does the iris adjust the size of the pupil?
To adjust the amount of light entering the eye
What does the lens do?
bends or refracts light rays so the rays focus on the nerve cells of the retina (controls light)
What does fluid in the eye do?
helps maintain the eye shape and refract the light ray
The anterior fluid is called the
aqueous humor
the posterior fluid is called the
vitreous humor
What is the innermost layer of the eye?
The retina
What does the retina contain?
Rods and cones
What is the difference between rods and cones?
Cones sense color while rods sense light
What is the sclera?
It is the outer surface, tough, whitish layer of connective tissue. It is the most superifical.
What is at the front of the sclera?
The cornea
What is the cornea?
transparent section of sclera
what does the cornea do?
Allows light into the eye
why is the cornea transparent?
because it has to allow light
What does vitreous humor do?
Allows the eye to maintain shape
What is the vitreous humor behind it?
Behind lens (large)
What is aqueous humor?
In front of lens (smaller), helps to give eye its shape
What happens in the aqueous humor?
Circulation of essential materials such as ions, nutrients, amino acids and etc happens
What does the conjunctiva do?
Moisten, cleans, prevents drying out
What is glaucoma?
Damage of the optic nerve
Where is the choroid?
It is in the middle and below sclera
What does the choroid have?
Many different types of pigmented layers because of many different genes
What is the front of the eye?
Iris
What do Muscles within do?
regulate the size of the pupil (opening in the center)
what does the lens do?
makes image on the retina
where is the lens
toward front of the eye, held by ligaments
where is the retina?
on the back of the eye on top of the choroid and it is the 3rd layer
what does the retina have
it has photoreceptors
what is the retina concentrated on?
fovea (sweet spot)
where is the blind spot nearby in the retina
optic nerve
what do rods and cones send?
Rods and cones send action potentials to the brain
what are Rods
More sensitive to light, Detect shades of gray in dim light
what are cones
color, less sensitive to light, allow us to see color in bright light
Where does the sensory neuron transmit a danger signal through?
It transmits a danger signal through the dorsal root ganglion
What type of fibers do dorsal roots have?
Dorsal roots have afferent fibers
What does the interneuron do?
The interneuron in the spinal cord passes along the signal to a motor neuron that stimulates a muscle
What does the efferent division contain?
The efferent division contains the central root and motor neurons.
What does the afferent division contain?
It contains dorsal roots and sensory neurons
What does spinal nerves connect to?
The spinal nerves connect to the spinal cord by two bundles of nerve fibers called roots
What do the ventral roots contain
The ventral roots contain efferent motor fibers
What do the efferent motor fibers in the ventral root do?
They carry information away from the CNS
What do the afferent fibers in the dorsal root carry?
They carry sensory information from receptors to the CNS
How many pairs of spinal nerves are there?
There are 31 pairs of spinal nerves
How many cranial nerves are there?
12
