Peripheral Nervous System Flashcards
(23 cards)
What are Peripheral nerves?
Bundles of nerve axons lying outside the CNS
Anatomically what is the PNS
The cranial nerves from the Brainstem, spinal nerves, sensory ganglia, and sensory receptors
What are the primary functions of the PNS
Convert stimuli into appropriate signals, convey that sensory signal to the CNS, convey motor signals from the CNS to appropriate organs, convert the motor signal to a chemical signal at target tissues
Peripheral nervous system is divided into what systems
Somatic and autonomic
What does the somatic division do
Primarily deals with external environment of the body, sensory axons innervate skin, joins, muscle, and motor axons innervate skeletal muscle
What does the autonomic division do?
Primarily deals with the body’s internal environment, motor and sensory neurons that innervate smooth muscle, exocrine glands, and other viscera
(Things that are behind our level of consciousness)
(Sense pH, secretion of enzymes, etc.)
Sensory neurons are responsible for what?
They carry information from the body to the spinal cord or brain stem — then to the cerebellum for interpretation OR form a reflex arc in the spinal cord. Sensory information includes body position and balance, touch, pain, temperature, and the special senses of taste, hearing, vision and smell
What do motor neurons do?
They carry the responses to the sensory signals back to the body. In the spinal cord, motor neurons axons form bundles known as motor tracts. The motor neurons regulate voluntary movements and muscle control
What is a motor unit
The motor neuron and the muscle that it innervates
What are upper motor neurons
Confined to the CNS, initiate voluntary movement, maintain muscle tone, regulate posture/stance
What are Lower motor neurons
Exits the CNS, connects the CNS to the effector organ, transmits UMN signals to effector organs
What are the clinical signs of a LMN disease
Hypoflexia or arefelxia, weakness, hypotonia or atonia, neurogenic atrophy
Neurogenic atrophy
Background tone of nerves don’t work, nerves shrink down and muscle shrinks
Jobs of UMN
- Initiate voluntary motor activity: gait generation
- Maintain muscle tone to counter gravity and to establish posture
- Provide a solid base upon which movement can occur
Diseased UMN symptoms
Ataxia, spasticity (messed up tone), paresis, hyperreflexia, loss of conscious proprioception
Where would the deficit be if the injury was in the cervical spinal cord?
Same side
Where would the deficit be if the injury was in the brain?
Opposite side
What is sensory transduction
Converting environmental signals into neural signals
How do mechanoreceptors work?
Pressure applied cause compression and membrane transforms and the channels open
What are the proprioceptors
Muscle spindles, golgi tendon organs, and joint receptors
General proprioceptive ataxia
A loss of awareness of where the limbs are in space. Often occurs with UML lesions. Loss of postural and placing reactions. Typical damage of spinal cord
Vestibular ataxia
A loss of balance reflected in a head tilt, and a tendency to learn, drift, fall or roll to one side and nystagmus. Ataxia relative to gravity
Cerebellar ataxia
Reflects the inability to modulate the gait generating systems in the brain stem
- Abnormalities in stride
- Head tremors, truncal sway
- Base wide stance
