Khan Academy Flashcards
(32 cards)
How many cranial nerves are there? Spinal?
Cranial = 12 Spinal = 31
What are ganglia?
Collections of neuron somas
Nerves come in pairs of afferent and efferent nerves. What is the function of each of these nerves?
Afferent = carry sensory information to the CNS Efferent = carry motor information away from CNS
** to remember: think Exit Efferent
Afferent and efferent nerves in the spine are paired on either side of the spinal column, with one nerve anterior and one nerve posterior. Which nerve is which? (I.e are efferent nerves anterior or posterior?)
Efferent nerves are anterior, afferent nerves are posterior
** to remember: Exit through the front door
Efferent neurons are in front (anterior)
What are the components of a motor unit?
1) lower motor neuron
2) skeletal muscle cell(s) that the neuron synapses with (is in electrical contact with)
What is the name for a synapse in a motor unit?
Neuromuscular junction
Imagine a motor unit in the front of your leg and a motor unit in your fingers. How are these motor units similar? How are they different?
Similar:
- still consist of motor neuron in spine and muscle cells that it controls
Different:
- size of motor unit is related to function of skeletal muscle: the fingers have smaller muscles that perform intricate movements, whereas the quadriceps of your leg is a large muscle that perform much less intricate movements. Therefore, the motor units that enervate the hands are smaller (less skeletal muscle cells under the control of one neuron) than those that enervate the leg (more skeletal muscle cells under the control of one neuron)
There are several basic abnormalities that can occur to lower motor neurons. These abnormalities are called Lower Motor Neuron Symptoms (LMNS) (** think lemons). What are these symptoms?
1) weakness
2) atrophy (decreased muscle bulk)
3) hypotonia (decreased muscle tone, muscle tone is the resting tension in our muscles, if a person displays hypotonia then their muscles seem very relaxed when at rest and do not display much resistance to manipulation)
4) hyporeflexia = decreased muscle stretch reflexes, which are reflexes that happen if you rapidly stretch the muscle
5) Fasiculations = twitches that are constant and occur in an isolated area
What does somatosensation refer to?
Sensory information collected by the PNS
What are the 5 kinda of somatosensation? For each kind of sensation, what is the name of the reception associated with sensing the sensation?
1) position (mechanoreceptor)
2) vibration (mechanoreceptor)
3) touch (mechanoreceptor)
4) pain (nociceptor)
5) temperature (thermoreceptors)
What is a distinguishing feature of mechanoreceptors?
They tend to be closer to the surface of the skin and contain a bulbous structure at their free end.
How do the axons of mechanoreceptors compare to those of nociceptors and thermoreceptors?
The axons of mechnoreceptors are larger in diameter and have a thicker myelin shealth, which means they conduct action potentials more rapidly
Muscle Stretch Reflex (MSR)
1) What are the 2 basic parts of this reflex (and really any relfex)?
2) What is the characteristic feature of reflexes (general)?
3) In MSR, what side of the body are the signals on?
1) A stimulus (mallet) to the patellar tendon causes afferent somatosensory axon to send a signal to its soma near spinal cord, which creates an excitatory state. Then, efferent neuron, with soma in spinal cord, responds to excited state by sending signal to its axon to contract quadriceps. This results in production of a moment about the knee joint, which results in kicking of the lower leg.
2) They are involuntary action, do not require involvement of the cerebrum.
3) Afferent signal and efferent response are on the same side of the body.
What is a major difference between the way that efferent sympathetic and parasympathetic neurons synapse?
Efferent sympathetic NS neurons have soma in spinal cord, then have short axon that synapses on a nearby ganglia, which then has long axons that synapse on the tissue.
Efferent parasympathetic NS neurons have soma in the spinal cord and long axons that travel all the way to other neurons in/near the tissue. Once at the tissue, the axon synapses with the soma of another neuron, which has an axon in the tissue.
What are the targets of the autonomic nervous system?
Glands
Smooth muscle
Efferent neurons
Cardiac muscle
What is grey matter? White matter?
Grey matter contains somas
White matter contains myelinated axons
In the spinal cord, where is grey matter concentrated? White matter?
In the spinal cord, grey matter is concentrated in the center of the cord in an ‘H’ or butterfly shape. White matter surrounds the grey matter.
In the brain, where is grey matter? White matter?
Grey matter is mostly on the outer surface of the brain (there are some bodies of grey matter in the brain called nuclei, such as the septal nuclei). White matter is mostly in the middle of the brain.
This is opposite of the spinal cord.
Where are upper motor neurons contained? What do they synapse on?
They are in the grey matter of the brain, their axons travel through the white matter of the brain and synapse on the lower motor neurons
Describe the corticospinal tract
UMN Soma in the left hemisphere have axons that travel down through the brain, cross the midbrain, pons and medulla and synapse on LMN somas on the right side of the spinal cord
What is a major difference between the way that efferent sympathetic and parasympathetic neurons synapse?
Efferent sympathetic NS neurons have soma in spinal cord, then have short axon that synapses on a nearby ganglia, which then has long axons that synapse on the tissue.
Efferent parasympathetic NS neurons have soma in the spinal cord and long axons that travel all the way to other neurons in/near the tissue. Once at the tissue, the axon synapses with the soma of another neuron, which has an axon in the tissue.
What are the targets of the autonomic nervous system?
Glands
Smooth muscle
Efferent neurons
Cardiac muscle
What is grey matter? White matter?
Grey matter contains somas
White matter contains myelinated axons
In the spinal cord, where is grey matter concentrated? White matter?
In the spinal cord, grey matter is concentrated in the center of the cord in an ‘H’ or butterfly shape. White matter surrounds the grey matter.
