Anatomy Flashcards
What is proprioception
The ability to sense stimuli with the body in regard to position, motion and equilibrium
List the components of the reflex arc
- Receptor
- Sensory
- Integration centre
- Motor neuron
- Effector
Where is the receptor found
It is at the site of stimulus action
What do sensory neurons do
They transmit afferent information to CNS
What is the integration centre
One or more synapses in the CNS
What does the motor neurone do
It conducts efferent impulses to the effector Organ
What is an effector
A muscle fibre or gland that responds to impulses
List the 5 conscious modalities
- Touch
- Auditory
- Sight
- Smell
- Taste
List the 5 subconscious modalities
- Pain
- Balance
- Body position
- Movement
What does sensory transduction require
Requires detection to changes in the environment (Stimuli)
What is sensory induction
Environmental signals being converted into electrochemical
How is a stimulus detected
Sensory receptors/ neurones detect changes in the environment
What is necessary to be able to detect a small stimulus
Amplification
What does localised depolarisation trigger
Triggers an action potion to propagate to the central nervous system via afferent fibres
What is the magnitude of receptor potential dependent on
Stimulus strength
How can sensory receptors be classified
- Location
- Function
- Fast or slow adapting
How do we classify sensory receptors by location
- Exteroceptors
- Interoreceptors
- Proprioceptors
Describe Exteroceptors
Sensitive to stimulus outside the body
Describe Interoreceptors
They respond to stimuli within body
Describe Proprioceptors
Advice the brain of body movements
How do we classify sensory receptors by function
- Mechanoreceptors
- Proprioceptors
- Thermoreceptors
- Chemoreceptors
- Noiciceptors
- photoreceptors
What do mechanoreceptors detect
Detect touch, pressure. vibration and stretch
What do Proprioceptors detect
Position
What do thermoreceptors detect
Detect temperature changes
What do photoreceptors detect
Detect light energy
What do chemoreceptors detect
Detect chemical stimuli
What do Nociceptors detect
Detect pain
What are fast adapting neurones
Their response declines rapidly with continuous stimulation
What is another name for fast adapting neurones
Phasic receptors
What are slow adapting neurones
They continue to respond as long as the stimulus is there
What is another name for slow adapting neurones
Tonic receptors
Give an example of a fast adapting neurone
Thermoreceptors
Give an example of a slow adapting neurone
Pain receptors
Where are mechanoreceptors found
Present under fingertips and respond to mechanical forces
What do mechanoreceptors cause
Membrane distortion in receptive endings opening ion channels
Name the different types of sensory receptors
- Free sensory endings
- Root hair plexus
- Merkel disks
- Pacinian corpuscles
- Ruffini corpuscles
- Messner’s corpuscles
- Krause’s End Bulbs:
Describe Free sensory endings
Unencapsulated free end sensory swelling with distal knob like swellings
WhIch location class can free sensory endings fall under
Exteroceptors,
interoreceptors,
proprioceptors
Which function class can sensory endings fall under
Nociceptors (pain),
chemoreceptors,
thermoreceptors
mechanoreceptor
Where are free sensory endings found
Most internal tissues (mostly in connective tissue)
Describe root hair plexus
Modified unencapsulated free nerve endings that entwine into hair follicles
WhIch location class can root hair plexus fall under
Exteroceptors
Which function class can root hair plexus fall under
Mechanoreceptors
Where are root hair plexus found
In and surrounding hair follicles
Describe merkel disks
Unencapsulated free nerve endings attaching to deep epidermis
WhIch location class can Merkel disks fall under
Exteroceptors
Which function class can Merkel disks fall under
Mechanoreceptors
Where are Merkel disks found
Base of epidermis and sweat ridges of fingertips
What is the function of Merkel disks
Gather information regarding pressure and texture of touch
Describe Pacinian corpuscles
Single nerve cell surrounded by 60 layers of Schwann cells
WhIch location class can Pacinian corpuscles fall under
Exteroceptors, interoreceptors & some proprioceptors
Which function class cam Pacinian corpuscles fall under
Mechanoreceptors
Where are Pacinian corpuscles found
Dermis and subcutaneous layers of skin (fingers, soles, genitalia, nipples)
What is the function od Pacinian corpuscles
Sensitivity to pressure pain and stretch
Describe Ruffini’s corpuscles
Spray of branching nerve endings enclosed by a capsule
WhIch location class can Ruffini’s corpuscles fall under
Exteroceptors & proprioceptors
Which function class can Ruffini’s corpuscles fall under
Mechanoreceptors
Slow adapting
Where are Ruffini’s corpuscles found
Deep in dermis, hypodermic and joint capsules
What is the function of Ruffini’s corpuscles
Sensitivity to skin stretch
Also contributes to tactile learning of finger position
Describe Messner’s corpuscles
Small receptors surrounded by Schwann cells
Which location class do Messner’s corpuscles fall under
Exteroceptors
Which function class do Messner’s corpuscles fall under
Mechanoreceptors
Where are Messner’s corpuscles found
Dermal papillae of hairless skin, lips, nipples, genitals, fingertips and eyelids
What is is the function of Messner’s corpuscles
Sensitive to light touch
Describe Krause’s End Bulb
Dendrite like endings surrounded by stem cells
Which location class can Krause’s End Bulb fall under
Exteroceptors
Which function class can Krause’s End Bulb fall under
Mechanoreceptors
Where can Krause’s End Bulb be found
Connective tissue of mucosa and hairless skin near body opening
What is the function of Krause’s End Bulb
They detect low few vibration and changes in texture
Which receptors detect a gentle stroke on the back of the hand
Root hair and Merkel cells (mechanoreceptors)
If you place your hand on a hot stove which receptors are stimulated
Mainly free nerve endings (temp/ noiciceptice)
What is proprioception
it gives us a sense of where our limbs are in space
Name the different types of proprioception
- Muscle spindles
- Golgi tendon
- Joint receptor
Why is proprioception important in dentistry
- Importance for extensive mobility of the TMJ
- Maintenance of proper mandibular position during mastication and speech
- Implicated in certain pain syndromes
- Involved in jaw reflex mechanisms
Which function group do muscle spindles fall under
Mechanoreceptors
Where are muscle spindles found
Skeletal muscles
Describe muscle spindles
Stretch receptors inside spindles sensitise to muscle length
How do muscle spindles work
- Intrafusal fibres within the muscle spindles, detect muscle stretch & initiate reflex
- They send impulses to spinal cord via 1a sensory afferent fibres
- They inhibit motor neurone activity to the muscles
- When muscle contracts muscle spindles shorten and switch off
Where are Golgi tendon organs found
Muscle tendons
Describe Golgi tendon organs
Stretch receptor inside tenons enclosed in layered capsule surrounded by axons
How do Golgi tendons work?
- Stretch receptors detect tension and initiate reflex
- Activated by muscle tension, not length
- Both spindles and Golgi tendons organs active when muscle is passively stretched
- Spindle switches off it muscle back to original length but tension still activated Golgi tendon organs
- Reflex initiates muscle to relax, removing stimulation
Name the 3 divisions of the trigeminal nerve
- Ophthalmic
- Maxillary
- Mandibular
The ophthalmic nerve carries sensory information from where?
- Scalp
- Forehead
- Upper eyelid
- Conjunctiva
- Cornea,
- Tip of nose
- Nasal mucosa,
- frontal sinuses
- parts of the meninges
The maxillary nerve carries sensory information from where?
- Lower eyelid and cheek,
- nares & upper lip,
3, upper teeth and gums - Nasal mucosa,
- palate & roof of the pharynx,
- maxillary,
- ethmoid & sphenoid sinuses
The mandibular nerve carries sensory information from where?
- The lower lip,
2, lower teeth & gums, - chin & jaw (except angle of mandible)
- Parts of the external ear
Name a dental disease involved in proprioceptors
Dental distress syndrome
What is dental distress syndrome
Dysfunction in occlusion causing disturbances throughout the body
What is dental distress syndrome caused by
- Loss of one or more teeth
- Loss of vertical dimension
- Excessive tooth wear (due to bruxism)
- An underdeveloped upper jaw
- Osteoarthritis of TMJ
- Whiplash injury
What can malocclusion cause
Faulty perception of trigeminal nerve
Can lead to altered blood supply and neural feedback to the brain
Talk though a reflex arc
- Receptor detects the stimulus
- Sensory neurone transmits afferent info into the CNS
- Synapsing occurrs in the CNS at the integration centre
- Motor neurone conducts efferent impulses to the effector organ
What is present along the CNS
Enlargements where synapsing occurs
Name the 2 different types of enlargements
- Cervical
2. Lumbosacral
What do cervical enlargements supply
Forelimbs
What do lumbosacral enlargements supply
Hindlimbs
where is grey matter found
dorsal Horn
ventral horn
lateral horn
What happens at the dorsal horn
Sensory relay neurones enter
What happens at the ventral horn
Motor neurones leave
What happen sat the lateral horn
At intermediolateral nucleus, preganglionic sympathetic neurones are found
Where is white matter found
Dorsal column
Lateral column
Ventral column
What is the dorsal column
Path for ascending axons carrying somatosensory info from dorsal horn to brain
What is the Lateral column
Path for ascending & descending axons innervating inter & motor neurons
What is the Ventral column
Path for ascending & descending axons
What do ascending axons do
They convey information about pain and thermal sensation
What do descending axons do
They control muscles & posture
Name the 3 different types of reflex pathways
Monosynaptic
Disynaptic
Polysynaptic
Describe the monosynaptic reflex
Sensory neurones axon synapses directly with motor neurone
Describe the Disynaptic reflex
Single interneuron receives sensory input & synapses with motor neurone
Describe the Polysynaptic reflex
Reflex pathway involves 2 or more interneurons
What are muscles made up of
extrafusal and intrafusal fibres
Describe extrafusal fibres
They make the bulk of muscle and generate tension when contracting
Describe intrafusal fibres
They are specialised fibres embedded within muscle
These detect the amount of change in length of the muscle
Name the 2 types of motor neurones
Alpha and gamma
Which neurones innervate extrafusal fibres
Alpha motor neurones
Which neurones innervate intrafusal fibres
Gamma motor neurones
Where do alpha motor neurones receive their input
From 3 pathways:
From spinal interneurons
From upper motor neurons in the brain
Sensory input from muscle spindles
List the basic features of a reflex
- Rapid
- Can be simple
- Can involve interneurones in complex processing
- Are a response to dance
Talk through the stretch reflex
- A muscle is stretched
- Intrafusal fibres are stretches, this activates them
- Intrafusal fibres send afferent impulses along sensory neurone to the spinal cord
- The sensory neurone synapses with efferent motor neurone in ventral horn
- Motor neurone sends signals to the extrafusal fibres causing them to contract
- This contraction of extrafusal has 2 jobs: To protect the muscle from overstretching and To shorten the intrafusal fibre, thereby reducing the frequency of signals
What are the 2 jobs of the extrafusal fibres when they contract
- To protect the muscle from overstretching
2. To shorten the intrafusal fibre, thereby reducing the frequency of signals
List soem bleeding associated with dentistry
- Tooth extractions
- Surgery
- Trauma
What is the effect of blood loss
- Patient distress
- Blood in tissues (busing & infection) – older pt.’s bruise will migrate downward (gravity)
- Blood in stomach can cause vomiting
- Blood in airway can cause obstruction
Lost blood from vessels (hypovolemia)
What can hypovolemia lead to
- Shock
- Reduced oxygen carrying capacity
- Reduced protein in blood/ clotting factors
- Reduced platelets
What is Haemostasis
Blood clotting
How is haemostasis achieved
Vascular spasms
Platelet plug formation
How is the platelet plug formed
- Platelet gets activated and adhere to exposed collagen/VWF
- Platelet release reaction releases thromboxane A2 causes platelets to become activated
- Platelets aggregate (sticky) – stick to each other, collagen and fibrin strands
How does aspirin work
Aspirin irreversibly binds to platelets this inactivates platelet COX (cyclooxygenase) enzymes needed for thromboxane A2 aggregation
How does clopidogrel work
Clopidogrel binds to P2Y12 receptor irreversibly and prevents ADP mediated aggregation
How long does it take platelets to renew
10 days
Which patents are filet to be on clopidogrel drugs
Patients with
- Vascular disease
- Thromboembolic disease
- Stroke patients
- Peripheral vascular disease
- in which platelet aggregations are likely to form within the vascular system
Should we stop patients taking aspirin before treatment
no
How can we test bleeding function
- INR
- Platelet count
- Activated partial thromboplastin time
State a noraml platelet count
200 – 400 * 10^9 / L
How does warfarin work
Prevents the action of vitamin K and prevents carboxylation of clotting factor precursors
What is vitamin k produced by
Gut bacteria
Why is vitamin K important
is required for the production of factors, II, VII, IX & X
Which parent are most Likely to be taking warfarin
- People with atrial fibrillation
- People with heart valve abnormalities or replacement
- Thromboembolic diseases
- Some other cardiac & vascular abnormalities
What INR is safe
More than 4