CNS: structure and function - week 3 Flashcards
what are the 3 main functions of the CNS?
control of internal environment
voluntary control of movement
Spinal cord reflexes
what are the 4 divisions of the nervous system ?
CNS- brain + spinal cord
Peripheral NS - neurons outside the CNS
sensory division - afferent fibres transmit impulses from receptors to CNS
motor devision - efferent fibres transmit impulses from CNS to effector organs
what are the 2 elements of the input sensory NS in functional organisation?
somatic sensory - consciously perceived
visceral sensory - not conscious
what is an axon ?
carries electrical message(AP) away form cell body
what are Schwann cells ?
form myelin sheath over length of axon
what is a synapse ?
contact points between axon of one neuron and dendrite of another neuron
the greater the__ of the axon, the greater the __ of neural transmission
diameter
speed
what is a dendrite?
sends input from synapse to the axon
what are the nodes of ranvier ?
propagation of signal/impulse along axon
the inside of cell have a __ charge at rest (__)
negative
polarised
what determines the magnitude of resting membrane potential ? (2)
permeability of plasma membrane to ions
difference in ion concentrations across membrane
at rest __ channels are closed and __ channels are open.
this causes a _ membrane potential
sodium
potassium
negative
how is a negative membrane potential maintained ?
sodium-potassium pump
what is a sodium-potassium pump ?
moves 2K+ in and 3 NA+ out
uses ATP to maintain environment
what is an action potential?(2)
occurs when stimulus of sufficient strength depolarises the cell
opens Na+ channels to make cell positive charge
(depolarisation)
what is repolarisation ? (2)
return to resting membrane potential
K+ leaves cells rapidly
Na+ channels close
what is the all or none law?
one nerve impulse initiated it travels length of neuron
(doesn’t stop)
what is a neurotransmitter ?
chemical messenger released from presynaptic membrane
binds to receptors on post synaptic membrane
causes depolarisation of postsynaptic membrane
what is excitatory postsynaptic potentials (EPSP)?
help achieve depolarisation
how do EPSPs achieve depolarisation ? (2)
temporal summation
spatial summation
what is temporal summation ?
rapid repetitive excitation from a single excitatory presynaptic neuron
what is spatial summation ?
summing EPSPs from several different presynaptic neurons
what are inhibitory post synaptic potentials (IPSP) ?(2)
cause hyperpolarisation (more neg resting potential)
a more neg membrane potential resist depolarisation
what are the joint proprioceptors ? (3)
free nerve endings - touch/pressure
Golgi type receptors - ligaments
pacinian corpuscles - tissues around joints/skin
what are the muscle proprioceptors/ mechanoreceptors ? (2)
muscle spindles
Golgi tendon organs
what is another sensory info/reflex other than muscle proprioceptors?
muscle chemoreceptors
what is proprioception ?
the boy’s sense of position based on specialised receptors that reside in the muscles, tendons and joints
what are proprioceptors ?
sensors that provide info about joint angle, muscle length, and muscle tension which is integrated to give info about position of limb
what are muscle spindles ? (3/4)
respond to changes in the muscle length
intrafusal fibers - run parallel to normal fibres
gamma motor neurons - stimulate intrafusal fibres to contract with extrafusal
(muscle spindle loses so spindle reflex makes it taught again)
what is the stretch reflex ?
stretch on muscle causing reflex contraction
how does the muscle spindle work ?
muscle spindles detect __ of muscle
___ neuron conduct action potentials to ____ ____
___ neurons synapse with ___ ___ neurons
stimulation of the ____ ____ neurons causes the muscle to contract and _____ being stretched
stretch
sensory
spinal cord
sensory
alpha motor
alpha motor
resist
what does the gogli organ tendon do ? (2)
monitors force development in muscle - prevents damage during excessive force generation
stimulation results in reflex relaxation of muscle - inhibitory neurons send inhibitory post synaptic potentials to muscle alpha motor neurons
how does the Golgi tendon organ work ?
gogli organ tendons detect ___ applied to a ___
___ neurons conduct APs to the spinal cord
____ neurons synapse with____interneurons that synapse with ___ ___ neurons
_____ of ___ ____ neuron cause muscle _____, relieving the tension applied to tendon
tension
tendon
sensory
sensory
inhibitory
alpha motor
inhibition
alpha motor
relaxation
what are muscle chemoreceptors ?
sensitive to changes in the chemical environment surrounding a muscle
what is a motor unit ?
motor neuron and all the muscle fibres it innervates
if there’s a low ratio of muscle fibres to motor neuron what does this mean?
allows fine motor control
if there’s a high ratio of muscle fibres to motor neurons what doe this mean ?
greater/gross motor control
what happens in terms of motor unit recruitment in terms of force needed ?
if more force is needed , more motor units are recruited
what is the size principle in terms of motor unit recruitment?
smaller motor units are recruited first during exercise
what are the 3 types of motor units ?
Type S - slow type 1 fibres
type FR- type 2a fast fatigue resistant
type FF - type 2x fast fatigable
what is role of cerebrum ? (3)
organisations of movement
storage of learned experiences
reception of sensory info
what is role of cerebellum ?
control of movement and integration of sensory info
what is the role of the brainstem ? (3)
Cardiorespiratory function
locomotion
muscle tone
posture
receive info from special senses
what are the functions of the midbrain in the brainstem ? (1 but gave 3)
body movement - most important
control responses to sight, eye movement and pupil dilation
hearing
what is the role of the medulla oblongata in the brain stem ?
coordination of body movement - important
relay signals between brain and spinal cord
what is the role of Pons in the brainstem ?
relay of sensory info between cerebrum and cerebellum
what is spinal tuning ?
intrinsic neural networks in the spinal cord that refine voluntary movement after reviewing messages from higher brain centres
what is the withdrawal reflex ?
via reflex arc
contraction or muscles in response to sensory input - doesn’t need higher brain centres
