Week 3 - Central Nervous System Flashcards
Whats the anatomical division of the CNS
Brain and Spinal Cord
Whats the anatomical division of the PNS
Neurons outside the CNS
Whats the sensory division
Afferent fibers transmit impulses from receptors to the CNS
Whats the motor division
Efferent fibers transmit impulses from CNS to effector organs
What are the roles of axons
Carries electrical message (action potentials) away from the cell body.
Covered by Schwann cells
Whats the role of Schwann cells
Form discontinuous myelin sheath along the length of axon
Whats the role of the synapse
Contact point between axon of one neuron and dendrite of another
Whats the regular resting potential in a cell
-70 mv
What impacts the magnitude of resting membrane potential
(ON SHEET)
Permeability of plasma membrane to ions
Difference in ion concentrations across the membrane
Explain the exchange of sodium and potassium at the cell membrane
(ON SHEET)
Its maintained by the sodium potassium pump. Potassium tends to diffuse out of the cell so to overcome this the pump transports 3 sodium ions out and 2 potassium ions in. By using energy from ATP which helps aid muscle contraction
When does an action potential occur
Occurs when a stimulus of sufficient strength depolarizes the cell. This opens Na+ channels so Na+ diffuses into the cell making the inside become more positive
What is repolarization
The return to resting membrane potential. K+ leaves the cell rapidly and Na+ channels close
What is the all or none law
Once a nerve impulse is initiated, it will travel the length of a neuron
Whats the role of sodium channels
Lets sodium enter the cell to make the cell more positively charged helping increase action potential
Whats the role of Excitatory postsynaptic potentials (EPSP)
To promote neural depolarization in 2 ways
What are the 2 ways that EPSP can promote depolarization
(ON SHEET)
Temporal summation - rapid, repetitive excitation from a single excitatory presynaptic neuron.
Spatial summation - summing EPSPs from several different presynaptic neurons
Whats the effect of Inhibitory postsynaptic potentials (IPSP)
Causes hyperpolarization (more negative resting membrane potential)
Whats the effect of neurons with more negative membrane potential
The more negative the membrane potential the more able they are to resist depolarization
What are proprioceptors
Sensors that provide information about joint angle, muscle length and muscle tension which is integrated to give information about the position of the limb in space
Whats the role of muscle spindles
Respond to changes in muscle length
What are muscle spindles made up of
Infusal fibers - run parallel to normal muscle fibers (extrafusal fibers)
Gamma motor neurons - Stimulate intrafusal fibers to contract with extrafusal fibers (by alpha motor neuron)
How do muscle spindles work with the stretch reflex
Stretch on muscle causes reflex contraction. Knee-jerk reflex
Explain how muscle spindles work in relation to muscle contraction
- Muscle spindles detect stretch of the muscle
- Sensory neurons conduct action potential to the spinal cord
- Sensory neurons synapse with alpha motor neurons
- Stimulation of the alpha motor neurons causes the muscle to contract and resist being stretched
Whats the function of muscle spindles
Assist in the regulation of movement and maintain posture
Whats the role of the golgi tendon organ
Monitor force development in muscle. Prevents muscle damage during excessive force generation
Whats the effect of stimulation of the golgi tendon organ
results in reflex relaxation of the muscle. Inhibitory neurons send inhibitory postsynaptic potentials (IPSPs) to muscle alpha motor neurons
What can link to voluntarily being able to oppose Golgi Tendon Inhibition
(ON SHEET)
gains in strength with training due to
increased tendon stiffness
Explain the process of how golgi tendons cause muscle relaxation
(ON SHEET)
- Golgi tendon detect tension applied to a tendon.
- Sensory neurons conduct action potentials to spinal cord
- Sensory neurons synapse with inhibitory interneurons that synapse with alpha motor neurons
- Inhibition of the alpha motor neurons causes muscle relaxation, relieving the tension applied to the tendon.
Whats the role of muscle chemoreceptors
(ON SHEET)
Muscle chemoreceptors are sensitive to changes in the chemical environment surrounding a muscle.
They also inform the CNS about metabolic rate of muscular activity - this is important for the regulation of cardiovascular and pulmonary responses
Whats the role of motor neurons
Located within
spinal cord.
- Responsible for carrying neural
messages from spinal cord to
skeletal muscles
Whats the innervation ratio
Number of muscle fiberss innervated by a single motor neuron.
Whats the low ratio of an innervation ratio
Low ratio is involved with fine motor control. For example 23/1 in extraocular muscles
Whats the high innervation ratio
In muscles that don’t require fine motor control. For example 1000/1 or greater in large limb muscle
How are more motor units recruited
More muscle fibers are recruited by activating motor units
Whats the size principal of motor unit recruitement
Smallest motor units are recruited first during exercise
What are the different types of motor units
(ON SHEET)
Type S - Slow or Type I (smallest)
Type FR - fast, fatigue resistant or type II A (intermediate)
Type FF - fast, fatigable or type II X (largest)
Whats the recruitment pattern during incremental exercise
Type S -> Type FR -> Type FF
What are the key components of the brain
(ON SHEET)
Cerebrum or cerebral cortex
Cerebellum
Brainstem
Whats the role of the cerebrum/cerebral cortex
(ON SHEET)
- Organisation of complex movement
- Storage of learned experiences
- Reception of sensory information
Whats the role of the cerebellum
(ON SHEET)
Implicated in the control of movement and integration of sensory information
Whats the role of the brainstem
(ON SHEET)
Role of cardiorespiratory function, locomotion, muscle tone, posture, receiving information from special senses
Explain the role of the midbrain within the brainstem
Connects the pons and cerebral hemispheres.
Whats the function of the midbrain in the brain stem
(ON SHEET)
controlling responses to sight, eye
movement,pupildilation,body movementand hearing
Whats the role of the medulla oblangata
(ON SHEET)
involved in control of autonomic function,relaying signals
between the brain and spinal cord and coordination of body
movements
Whats the role of pons
(ON SHEET)
Involved in sleep and the control of autonomic function
Relays sensory information between the cerebrum and
cerebellum
What are the 3 types of neurons within the spinal cord
Motor neurons
Sensory neurons
interneurons
Explain the withdrawal reflex
Occurs via a reflex arc, whereby a reflex contraction of skeletal muscles can occur in response to sensory input and isnt dependent on the activation of higher brain centres
Whats the role of the motor cortex
(ON SHEET)
Receives input from variety of brain areas including basal nuclei, cerebellum and thalamus
Whats the role of spinal mechanisms
(ON SHEET)
Result in the refinement of motor control
Why is it important to get feedback from proprioceptors
Allows for further modification in motor control
