Central Nervous System: Structure And Function Flashcards
Difference between sensory and motor division
Sensory division: afferent fibres transmit impulses from recepryors to cns
Motor division: efferent fibres transmit impulses from cns to effector organs
Structure of a neuron:
1.axon-carries action potential away from cell body
2.synapse: contact point between axon of one neuron and dendrite of another neuron
Exchange of sodium and potassium across cell membrane:
Maintained by sodium and potassium pump.
-Potassium tends to diffuse out of cell
-sodium and potassium pump 2k in 3 NA out
Describe action potential
1.occurs when a stimulus of sufficient strength depolarises the cell
2.repolarisation-returns to resting membrane potential
3.all or non
What is a neurotransmitter
Chemical messenger released from presynaptic membrane.
-binds to receptor on postsynaptic membrane
-causes depolarisation of post synaptic membrane
What are excitatory postsynaptic potentials
They can promote neural depolarisation in two ways:
1.temporal summation: rapid repetitive excitation from a single excitatory presynaptic neuron
2.spatial summation: summing ESPS from several different presynaptic neurons
What are the 3 joint proprioception
1.free nerve endings (touch, pressure)
2.Golgi type receptors (found in joint ligaments)
3.pacinian corpulces (tissues around joints)
What are the 2 muscle proprioceptors
1.muscle spindles
2.Golgi tendon organs
What is proprioception
The sense of the body’s position in spaces based on specialized receptors that reside in the muscle, tendons and joint
What are muscle spindles
Respond to changes in muscle length
What do muscle spindles consist of
1.Intrafusal fibres (run parallel to normal muscle fibres)
2.gamma motor neurons- stimulate intrafusal fibres to contract with extrafusal fibres
3.stretch reflex-stretch on muscle causes reflex contraction
What is the Golgi tendon organ
Monitors force development in muscle, prevents muscle damage during excessive force
Stimulation results in reflex relaxation of muscle.
What are muscle chemoreceptors
They are sensitive to changes in chemical environment surrounding a muscle
Inform cns about metabolic rate of muscular activity
Structure of a motor unit:
Motor neurons are located in the spinal cord, and are responsible for carrying neural messages from spinal cord to skeletal muscles
What is a motor unit
A motor neuron and all the fibres it innervates
What is innervation ratio
Number of muscle fibres innervated by a single motor neuron.
Low ration in muscles involved in fine motor control, higher in not.
What is the cerebellum
Implicated in control of movement and integration of sensory information
What is the brainstem
Role in cardio respiratory function, locomotion, muscle tone, posture, receiving info from special senses
Describe the midbrain
1.connects the pond and cerebral hemisphere
2.controls responses to sight, eye movement, pupil dilation, body movement and hearing
Describe the medulla oblongata
Involved in autonomic function, relaying signals between the brain and spinal cord and coordination of body movements
Describe the PONS
Involved in sleep and control of autonomic function.
What is spinal tuning
Refers to intrinsic neural networks within the spinal cord that refine voluntary movement after receiving messages from higher brain centres
What is the withdrawal reflex
Where a reflex contraction of skeletal muscles can occur in response to sensory input and is not dependant on the higher brain centres
What 3 neurons does the spinal cord contain
1.motor neurons
2.sensory neurons
3.interneurons
