Neuro Physio Flashcards
What is Facilitation?
the enhancement of the response of a neuron to a stimulus following prior stimulation.
“the response is dependent on the frequency of stimulation and on neuromuscular facilitation”
Uni and bidirectional synapses?
The chemical synapse (most of the synapses in humans and all in cns ) is unidirectional (pulses are transmitted from the sending neuron to the receiving neuron) and only the electrical synapses are bidirectional through gap junctions. ( very few in cns mostly in smooth and cardiac muscles.
what are ionotropic and metabotropic receptors?
ionotropic receptors are typically ligand-gated ion channels, through which ions pass in response to a neurotransmitter (directly gate ion channels ), metabotropic receptors require G proteins and second messengers to indirectly modulate ionic activity in neurons.
inhibitory effect of acetylcholine?
some peripheral parasympathetic nerve endings i.e by vagus nerve in heart
Causes of synapse fatigue
spatial and temporal summation
Spatial summation occurs when stimuli are applied at the same time, but in different areas, with a cumulative effect upon membrane potential.
he effects of impulses received at the same place can add up if the impulses are received in close temporal succession. Thus, the neuron may fire when multiple impulses are received, even if each impulse on its own would not be sufficient to cause firing.
labeled line principle
Specificity of nerve fibres to transmit only one modality.
Max receptor potential amplitude?
100 mv
Rapidly aadapting/phasic/movement receptos?
PC adapts rapidly by either fluid redistribution or accomodation of tip of nerve fibre. some hair cells adapt within seconds and Meissner’s corpuscles. all the mechanoreceptors except a few adapt almost completely ( longest can take upto 2 days to adapt. )
Slowly adapting receptors/ tonic receptors?
Merkel’s discs and Ruffini endings, receptors of macula in vestibular apparatus, pain receptors, baroreceptors of arterial tree, chemoreceptors of carotid and aortic bodies and joint capsules and muscle spindle receptors
nerve fibres type of golgi tendon organs
group 1b also k/a alpha type A fibres
nerve fibres type of temp, pain and pricking pain
group 3 or delta type A
nerve fibres type of most discrete cutaneous tactile receptors and from flower spray nding of muscle spindles
group 2 also k/a beta and gamma type A
nerve fibres type of unmyelinated fibres carrying pain, temp, itch and crude touch sensations
group 4 also k/a type C fibers
nerve fibres type of annnulospiral endings of muscles spindles
group 1a also k/a alpha type A fibres
Amplifying divergence is characteristic of?
Corticospinal pathway supplying skeletal muscles
Reverberatory/Oscillatory circuit?
caused by positive feedback within the neuronal circuit that feeds back to re-excite the input of the same circuit hence prolong the signal also results in rhythmical signals that last for life
continual discharge caused by intrinsic neuronal excitabilty specially occur in neurons of?
Cerebellum and most of the interneurons of spinal cord
continuous touch receptors are?
EXPANDED TIP TACTILE RECEPTORS (MERKEL’S DISC GROUPED TOGETHER INTO DOME RECEPTOR innervated by a single large mylinated A-beta fibre ) also present on hairy parts of skin which DO NOT HAVE meissner corpuscles
Ruffinis ending receptors are present?
(DEEPER LAYERS OF SKIN) (HEAVY
PROLONGED TOUCH & PRESSURE) JOINT ROTATION. adapt slowly
Synaptic Delay?
SYNAPTIC DELAY
1. Transmission of impulse from pre to post synaptic Neuron time is required in process of Discharge of Neurotransmitter by pre synaptic membrane
2. Diffusion of Neurotransmitter in post synaptic membrane
- Action of Neurotransmitter on membrane receptor
- Action of receptor to increase membrane permeability
- Inward diffusion of Na to achieve threshold for AP
- Synaptic delay is about 0.5 milli seconds
Causes of synaptic Fatigue?
Exhaustion of neurotransmitter
- Progressive inactivation of post syn memb receptors
- Slow development of abnormal ionic concentration inside post synaptic neuron
Muscle sensory receptors?
Muscle Spindle: Detects length of the muscle & rate of change of length.
• Golgi Tendon Organ: Transmit information about tendon tension & rate of change of tension.
• These proprioceptors provide functional status
What are Ant Motor Neuron?
Larger neurons located in the anterior horns of the spinal cord.
■ They give rise to the nerve fibers that leave the cord by way of the anterior roots & directly innervate the skeletal muscle fibers.
■ They are of two types:
■ Alpha Motor Neurons
■ Gamma Motor neurons
Alpha Motor Unit innervate?
Stimulation of single alpha motor neurons excites group of muscle fibers known as MOTOR UNIT.
Renshaw cells and their role?
Each alpha neuron gives off collateral before it leaves the spinal gray matter which makes synaptic contact with a small cell present in ventral horn called Renshaw cell
■ These Renshaw cells are inhibitory cells that cause inhibition of surrounding motor neurons to sharpen or focus its signals. This phenomenon is known as Recurrent Inhibition or Lateral inhibition by Renshaw Cells
Primary ending of sensory innervation of muscle spindle?
They are present in central receptor area of the spindle
Type 1a fiber
These fibers make direct connection with α motor neurons innervating the same as well as synergistic muscle.
These endings are stimulated by sustained stretch of the muscle as well as brief stretch as by tapping over the muscle’s tendon called Tonic and Phasic stretch reflex respectively.
velocity of transmission: 70 to 120 m/sec
Secondary ending of sensory innervation of muscle spindle?
■ These give rise to group II fibers; 8 micrometers in diameter
■ These are relatively slow conducting
■ These nerve fibers make connections with the α motor neurons of the muscle from which they arise
■ These are best stimulated by sustained stretch called Tonic stretch reflex
■ Discharge frequency is related to length of the fibers
Static response of muscle
spindle:
■ Response of both the primary & secondary endings.
■ When the muscle is stretched slowly, sensory endings continue to transmit signals for several minutes. This is called static response of the muscle spindle.
Static response of muscle
spindle:
■ Response of both the primary & secondary endings.
■ When the muscle is stretched slowly, sensory endings continue to transmit signals for several minutes. This is called static response of the muscle spindle.
Dynamic response of muscle
spindle:
■ Response of the primary ending but not the secondary ending.
■ The primary ending is stimulated strongly when there is sudden change in length of the spindle.
■ Thus primary ending detects the rapid rate of change in spindle length.
Static and dynamic gamma fibres
■ Gamma motor nerve fibers control intensity of static & dynamic response.
■ Gamma dynamic fibers excites mainly nuclear bag intrafusal fibers.
■ Gamma static fibers excite nuclear chain fibers.
■ The simplest manifestation of muscle spindle is muscle stretch reflex.
Stretch Relfex
How a stretch reflex works:
– Stretch activates the muscle spindle
– Group II sensory neurons synapse directly with motor neurons in the spinal cord
– motor neurons cause the stretched muscle to contract
■ All stretch reflexes are monosynaptic and ipsilateral
low frequency vibrations stimulate?
Meisnner corpuscles which are slow adapting than PC
cold receptors?
TYPE A DELTA FIBERS (20 M/SEC)
Define Amorphosynthesis
A medical condition where the patient is unaware of somatic sensations from one side of the body, usually a sign of lesion in the left parietal lobe ( somatosensory association area )
Warm receptors
TYPE C (0.4 -2 M/SEC)
