Nervous Control of Muscular Movement Flashcards
Lecture 11
What is the Central Nervous System (CNS)?
The CNS consists of the brain and spinal cord. It controls everything the body does.
What is the Peripheral Nervous System (PNS)?
everything BUT the brain and spinal cord
Afferent Sensory Division (PNS)
The afferent sensory division carries information from the body (e.g., skin, muscles) to the brain and spinal cord.
Efferent division
The efferent division sends commands from the brain and spinal cord to the body. It includes the somatic (voluntary) and autonomic (involuntary) systems.
The Brain (Anatomy) (7 minutes)
What is the Cerebral Cortex?
What is the Spinal Cord?
The spinal cord is a bundle of nerves that runs from the brainstem to the lumbar vertebrae, carrying messages to and from the brain.
What are the Meninges?
layers of tissue that protect the brain and spinal cord, similar to saran wrap.
What are Nerves?
Bundles of axons in the PNS that transmit sensory and motor information between the CNS and the body.
Include 12 pairs of cranial nerves and 31 pairs of spinal nerves.
What is the Sympathetic Nervous System?
The sympathetic nervous system controls the “fight or flight” response during stressful situations.
What is the Parasympathetic Nervous System?
The parasympathetic nervous system handles “rest and digest” functions when the body is relaxed.
What is Somatic Nervous System?
The part of the PNS associated with voluntary control of body movements via skeletal muscles.
What is Autonomic Nervous System?
A component of the PNS that regulates involuntary physiological functions, including heart rate, digestion, and respiratory rate.
What two types of categories of nerve cells should you know?
The two types of nerve cells are neurons (which send signals) and neuroglia (which support neurons).
Neuroglia
Neuroglia are non-excitable cells that support and keep neurons alive in the CNS and PNS.
Neuron
The fundamental unit of the nervous system, responsible for receiving, processing, and transmitting information through electrical and chemical signals.
What is the Basic Structure of a Nerve Cell?
Cell Body (soma): Keeps the cell alive.
Axon: Sends signals.
Dendrites: Receive signals.
Myelin Sheath: Covers axons to make signals faster.
Nodes of Ranvier: Gaps in the myelin sheath.
What is Saltatory Conduction?
Saltatory conduction is when signals jump between gaps in the myelin sheath (Nodes of Ranvier), making them faster.
What is multiple Scelorosis
A disease characterized by the immune system attacking the myelin sheath of neurons, leading to disrupted neural communication. This leads to symptoms like fatigue, muscle weakness, and coordination problems.
What is a Synapse?
The junction between two neurons or a neuron and a target cell, where communication occurs via neurotransmitters.
What are interneurons?
Interneurons connect sensory (afferent) and motor (efferent) neurons. They can increase, decrease, or reverse signals.
Spinal Nerves
Thirty-one pairs of nerves arising from the spinal cord, responsible for motor and sensory functions.
What happens if you don’t get Action Potentials
Without action potentials, your body can’t send signals. For example, tetrodotoxin from pufferfish can block sodium channels, preventing signals.
What is a Nerve to Nerve Synapse?
where signals are passed between neurons through a synaptic cleft.
What can transmitter substances be?
Excitatory or Inhibitory
Add them up. Determine if you want to continue the signal. Positive means continue, negative means inhibit and stop (nothing happens)
What is Spatial Summation
occurs when signals from different places add up to trigger an action potential.
What is Temporal Summation
occurs when signals close together in time add up to trigger an action potential.
What is the Neuromuscular junction?
The synapse between a motor neuron and a skeletal muscle fiber, where nerve impulses are transmitted to initiate muscle contraction. The transmitter acetylcholine is released here.
What happens after acetylcholine is released?
After release, acetylcholine binds to receptors. It is then broken down to stop the muscle from staying contracted
How many Spinal nerves are there?
31 total.
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
What two regions is the spinal cord enlarged in?
The spinal cord is enlarged in the cervical region (for upper limbs) and lumbar region (for lower limbs).
What is a plexus?
A plexus is a network of converging and diverging nerves or blood vessels, like the brachial plexus.
what is grey matter?
The center of the spinal cord, made of nerve cell bodies.
what is white matter?**
Myelinated nerves surrounding the gray matter.
What is dorsal root?
Dorsal roots carries sensory information to the spinal cord.
What is ventral root?
The ventral root carries motor commands from the spinal cord.
What is the dorsal root ganglia? **
an enlargement that holds the cell bodies of sensory nerves
somatic sensory and autonomic efferent nuclei and somatic motor nuclei **
What is Spinal Cord Injury?
The result of trauma to the spinal cord but can also be associated with congenital or degenerative disease.
Transection of the spinal cord results in loss of all sensation and voluntary movement inferior to the point of damage
At what point is Spinal Cord Injury Fatal?
If the transection is above C4, the patient can die of respiratory failure
What is the difference between quadriplegia and paraplegia?
Quadriplegia: Paralysis of all four limbs (injury above C5).
Paraplegia: Paralysis of lower limbs (injury below cervical level).
What is the recovery potential for SCI?
Can neurons previously allocated to do X morph into being able to do Y?
In most cases, the injured neurons do not recover
What are propioceptors
Proprioceptors help you sense body position:
Muscle Spindles: Detect stretch.
Golgi Tendon Organs: Detect tension.
Joint Receptors: Detect angle and movement.
What are muscle spindles and their function?
Also known as intrafusal fibers. They are parallel to the regular muscle fibers (extrafusal fibers).
Gives you information of the degree of muscle stretch or changes in length.
When muscle is stretched, action potential frequency increase, when they’re relaxed the action potential is decreased.
How do muscle spindles activate alpha motor neurons?
Muscle spindles activate neurons through:
Tonic stretch (length).
Phasic stretch (speed).
Gamma system (adjusts sensitivity).
What is tonic stretch?
Responds to the final length of a muscle
What is phasic stretch?
Responds to how fast a muscle changes length
What is the gamma system?
it is when gamma efferent fibers innervate the contractile ends of the intrafusal fibers.
When alpha motor neurons activate, so do the gamma motor neurons. this is coactivation.
It provides the mechanism for maintaining the spindle at peak operation at any muscle length
They help maintain muscle spindle sensitivity
What is a stretch reflex?
when a skeletal muscle is stretched, a muscle spindle receptor is activated. The axon from this receptor structure will cause direct contraction of the muscle. A collateral of the muscle spindle fiber will also inhibit the motor neuron of the antagonist muscles. The reflex helps to maintain muscles at a constant length.
What is a reflex arc?*
A reflex arc is a neural pathway consisting of five components: receptor, sensory neuron, integration center, motor neuron, and effector. It is responsible for the automatic response of the body to a stimulus.
What is the golgi tendon organ?
it’s at the ends of the muscle in the tendon.
when a muscle contracts, the GTO stretches
it is in series with the muscle fibers
What is the function of Golgi Tendon organ?
The firing rate of GTO is very sensitive to changes in the tension of muscle.
1. The sensory information we get from GTO about the tension that muscles produce is very helpful in maintaining grip.
2. When it’s stimulated by excessive tension or stretch, it sends the sensory information to the Central Nervous System which causes the contracted muscle to relax (reflex inhibition). This will protect the muscle and its connective tissue from damage due to excessive loads.
What are Joint Receptors?
They give the CNS information about
- joint angle
- acceleration
- pressure
-pain
What is the primary motor cortex
Located near the frontal lobe of cerebral cortex.
each side of the brain controls the opposite side of the body
the primary motor neurons cross over in the pyramids of medulla.
What is the homunculus?
There are different sections that control certain areas of your body.
What is the corticospinal tract?
A collection of axons that travel between the cerebral cortex and the spinal cord, involved in voluntary motor control.
What is the pre-motor cortex?
A region of the frontal lobe involved in the planning and coordination of movements.
What is the somatosensory cortex?
A region of the brain that processes sensory input from the body, such as touch, temperature, and pain.
What is the cerebellum?
It is behind the brainstem
It is used to refine and smooth out movement.
It constantly integrates info from motor plans and feedback from the somatosensory cortex and compares where you are in space vs where you want to be and corrects it.
How does the cerebellum work?
it receives signals concerning motor output from the cortex and sensory information from:
- receptors in muscles, tendons, joints, and skin
- visual auditory and vestivular end organs
example: poor balance
- constantly correct because they don’t know where they are in space
What are symptoms of cerebellum damage?
Damage to the cerebellum can result in ataxia, characterized by a lack of coordination, balance issues, and difficulty with precise movements.
