Chapter 13 Flashcards
What are motor endings?
An element of the PNS that active effectors by releasing neurotransmitters
What do motor endings do?
Make something happen
What are the 4 steps of excitation
1.) Movement of Na+ and K+ across a membrane
2.) The muscle cell depolarizes
3.) The excitation triggers an action potential
4.) The muscle contracts
What level does innervation of skeletal muscle take place at
The neuromuscular junction
What neurotransmitter gets released in innervation of skeletal muscle
ACh
What is simpler and slower: Autonomic motor endings and visceral effectors or somatic junctions
Autonomic motor endings and visceral effectors
What do branches in visceral muscles and glands form
synapses “en passant” (in passing) through varicosities
How do neurotransmitters in visceral muscles and glands act
Indirectly through second messenger systems
What are the neurotransmitters involved in visceral muscles and glands
ACh and norepinephrine
What are the 3 motor control levels in skeletal muscle (lowest to highest)
Segmental, projection, precommand
What does the segmental level control
Reflexes and spinal cord circuits
What are central pattern generators (CPGs)
Segmental circuits that activate networks of ventral horn neurons to stimulate specific groups of muscle
What does the projection level do
Sends information to the lower motor neurons and lets higher levels know what is happening
What anatomy is a part of the projection level
Precentral gyrus, cortex, brain stem
What is the cortex in charge of on the projection level of motor control
Initiates direct systems, voluntary movement, through upper motor neurons
What is the brain stem in charge of on the projection level of motor control
Oversees indirect systems, reflexes and CPG activity, through motor areas
What anatomy is a part of the precommand level
Cerebellum and basal nuclei
What is the job of the precommand level
Control the outputs of the cortex and brain stem
What does the precommand level do for activity
Determines if activity will start or stop
What does the cerebellum do on the precommand level of motor control
1.) Acts on motor pathways through projection areas in the brain stem
2.) Acts on motor cortex through the thalamus
What does the basal nuceli do on the precommand level of motor control
Acts to inhibit motor centers
What are reflexes
a rapid, predictable, involuntary motor response to a given stimulus
What are the two categories of reflexes
Autonomic and somatic
What are autonomic reflexes
Reflexes that involve smooth muscle, cardiac muscle, and glands
Examples of autonomic reflexes
sweat, increase in heart rate, salivation
What are somatic reflexes
reflexes that involve skeletal muscle that are quick
Examples of somatic reflexes
shiver, knee jerk, cough, muscle strech
What does a reflex arc describe
how actions happen
What are the steps to a reflex arc
1.) receptor picks up a stimulus
2.) sensory neurons carry info to the CNS in action potentials
3.) Integrate synapse in the CNS
4.) Motor neuron carries AP away from the CNS
5.) An effector gives a response
What is the muscle stretch reflex used for
to make sure that a muscle stays at the same length
Why do alpha and motor neurons stimulate together
So the muscle spindle responds at various muscle lengths
Intrafusal muscle fibers
skeletal muscle cells inside the spindle
What does sensory neuron type 1 do
respond to stretch and speed
What does sensory neuron type 2 do
respond to stretch degree/amount
What are the events of the muscle stretch reflex
1.) The muscle stretch activates the spindle, increasing AP’s to the CNS through the sensory neuron
2.) Sensory neurons synapse with alpha motor neurons of the stretched muscle
3.) Inhibitory interneuron inhibits the alpha motor neuron of the antagonist muscle
4.) The stretched muscle contracts and the antagonist muscle relaxes
Withdrawl reflex (somatic)
Pull away from painful stimuli
Crossed extensor reflex (somatic)
One side reflexes and the other side extends
Golgi tendon organ reflex (somatic)
Acs to inhibit a muscle from pulling too hard on a tendon
Superficial spinal reflexes (somatic)
Elicited by gentle cutaneous stimulation
Digestive system reflex (autonomic)
stretch the stomach, causes the colon to move
Cardiovascular system reflex (autonomic)
hr, bp, vessel flow
Integument system reflex (autonomic)
sweat, goosebumps
Eyes reflex (autonomic)
the pupil moves in response to light
Urinary system reflex (autonomic)
bladder contracts
Reproductive system reflex (autonomic)
child birth, orgasm
Why test reflexes?
1.) function of nerves, sensory and motor
2.) function of CNS at various levels
3.) degree of stimulation/inhibition of motor areas from the brain
What does the muscle spindle respond to
length
What does the tension organ respond to
tension
