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Dentistry BDS 2 Sem 1 > Physiology > Flashcards

Physiology Flashcards

1
Q

What is syncope?

A

Syncope is the key feature is a transient loss of consciousness and common pathophysiologic mechanism that includes a cerebral hypoperfusion.

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2
Q

What are requirements for consciousness?

A
  1. Adequate perfusion of brain with oxygenated blood
  2. Adequate delivery of glucose
  3. Adequate neural activity
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3
Q

What are some of the causes of syncopal collapse?

A
  1. Situational - pain stress and other
  2. Reflex - vasovagal syncope
  3. Cardiac - arrhythmia and bradycardia
  4. Psychogenic - anxiety disorders, depressive disorders
  5. Metabolic/other - hypoglycemia
  6. Neurologic - seizures
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4
Q

What is the cause of reflex and neurally mediated syncope?

A

The transient shift in autonomy response tends to trigger vasodilation which reduces cardiac output. This cause a drop in blood pressure which reduces peripheral perfusion.

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5
Q

What is the cause of situational syncope?

A

Compression of the vena cava, reduced venous return reduced cardiac filling, reduced cardiac output and a decrease in blood pressure. This increase SNS output. When breathing is resumed – the venous system improves cardiac filing, above normal resulting in transient increase in blood pressure. This increases parasympathetic drive. Bradycardia occurs which reduces blood pressure hence decreased cerebral pefusion/syncope

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6
Q

What is the Non-syncopal TLOCs?

A

The term Transient Loss of Consciousness is sometimes used when the cause is either unrelated to cerebral hypoperfusion or is unknown

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7
Q

What is the cause of syncope in psychiatric disease?

A

Hyperventilation, leads to hypocapnia, causing a transient increase in cerebrovascular resistance coupled with simultaneous peripheral vasodilation

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8
Q

What is the relation between dizziness & TLOC in pregnancy?

A

Progesterone promotes vasodilation – systolic bp can decrease – increase the likelihood of orthostatic hypotension

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9
Q

What are the functions of insulin?

A
  1. Insulin promotes uptake of glucose into muscle and adipose tissue
  2. Insulin promotes fat and glycogen synthesis in the liver from acetyl CoA. Fat is sent to the adipose tissue for storage.
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10
Q

What is the mechanism of action of insulin?

A
  1. It binds to extracellular tyrosine kinase receptor
  2. Activation of protein kinase B occurs
  3. Cellular response leads to: anabolic pathway activation, catabolic pathway inactivation
  4. Modulation of gene expression
  5. Recruitment/translocation of insulin-regulatable transporters from cytoplasm to the cell membrane
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11
Q

What are the three types of movements humans can produce?

A
  1. Reflective - involuntary coordinated patterns of muscle contraction
  2. Rhythmic - repetitive rhythmic motor patterns e.g. chewing
  3. Voluntary contractions – actions generated by the cerebral cortex
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12
Q

What are the steps in a simple reflex arc?

A
  1. Receptors
  2. Sensory neuron
  3. Integraton centre
  4. Motor neuron
  5. Effector muscle
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13
Q

What are the two main sensory receptors in the muscles?

A
  1. Muscle spindle – capable of detecting changes in muscle length and rate of change in length
  2. Tendon organs – capable of detecting changes in muscle force
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14
Q

Explain the tendon tap reflex.

A
  1. The tendon in the knee is struck
  2. This cause the stretch of the quadriceps
  3. The stretch is detected by the muscle spindle
  4. The afferent signal is propagated to the spinal cord
  5. An efferent signal is send from the spinal cord to the effector muscle
  6. This causes muscle contraction
  7. Result - leg jerks forward
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15
Q

What is the main purpose of the golgi tendon organ?

A

It is to protect the muscle from injury due to sudden or excessive load. They reside on the junction between the muscle and the tendon and are able to used inhibition signals to protect the muscles

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16
Q

Explain the flexor withdrawal reflex?

A
  1. A painful stimulus is detected
  2. It travels via the afferent neuron to the spinal cord
  3. Excitation of flexor and inhibition of extensor muscles occur via efferent neurons
  4. Result - the limb is removed from the pain stimulus
17
Q

Explain the crossed extensor reflex.

A

During the flexor withdrawal reflex, a contralateral extensor needs to occur to create balance. This means inhibition of flexor and excitation of extensor will occur on the opposite side of the body.

18
Q

What is an interesting fact about muscle spindles and mastication?

A

Muscle spindles are mostly present in the jaw opening muscle and least present in the jaw closing muscles. This makes sure that chewing is regulated and you be able to chew through hard objects and your jaw does not bounce during jogging.

19
Q

What is an interesting fact about golgi tendon organs and mastication?

A

They are present in the muscles of mastication – but their role is unclear!

20
Q

Explain the periodontal reflexes (sharp tap).

A
  1. Periodontal mechanoreceptors sense a hard tap on the tooth
  2. An afferent excitatory signal is send
  3. An inhibitory efferent signal is sent to the closer muscle
  4. Result - the jaw will not close
21
Q

Explain the periodontal reflexes (smooth tap).

A
  1. Periodontal mechanoreceptors sense a smooth tap on the tooth
  2. An afferent excitatory signal is send
  3. An excitatory signal is send to the closer muscles
  4. Result - the jaw closes to keep the food in
22
Q

What is proprioception?

A

It is the awareness of the sense of position of body segments in space, whereas kinaesthesia is the sense of movement.

23
Q

What are the 4 types of primary afferent axons and what are their function?

A
  1. A-alpha – thickest – at proprioceptors of skeletal muscles
  2. A-beta – thicker – at mechanoreceptors of skin
  3. A-delta – thick – used at the receptors that detect pain and temperature
  4. C - thin – use at the receptors that detect temperature, pain and itch
24
Q

What is a sensory unit?

A

It is a single primary axon with it’s correlating sensory units

25
Q

In terms of coding of sensory stimuli, what are the three things we must know?

A
  1. Modality - type of stimulus
  2. Intensity - how big the stimulus is
  3. Location - where the stimulus is
26
Q

Which of the skin receptors have large receptor fields?

A

Deep receptors have large receptor fields – such receptors are pacinian corpuscle and ruffini end organs

Superficial receptors have smaller receptor field – such receptors are merkel discs and meissnes corpuscles

27
Q

What are the more important receptors for proprioception?

A

The deep receptors with large sensory fields as they are able to be activated during joint movements

28
Q

What is important to understand in regards to proprioception and receptor cooperation?

A

The best outcomes in terms of proprioception occur when all receptor can contribute

29
Q

How does the proprioceptive information carried to the appropriate processing center in the brain?

A

Proprioceptive information is carried to the somatosensory cortex mainly via dorsal column-medial lemniscal pathway. This means that a primary afferent exon carries the information to and up the spinal cord, then synapsis occurs and the secondary axon carries the information through the opposite side to the thalamus. At the thalamus another synapses occurs and the tertiary axon carries the information to the somatosensory cortex

30
Q

What is a 2 point discrimination?

A

It is a process where 2 different stimuli are presented on the surface of the skin and are move closer and closer together until the individual can longer differentiate the two points, rather they think that the point is one. 2 point discrimination varies largely throughout the body.

31
Q

What is the relationship between the proprioception and the teeth?

A

Each tooth has a large number of periodontal mechanoreceptors. This mechanoreceptors are able to sense and signal when certain pressures are applied on the teeth. Which means the proprioception in regards to the jaws can occur as well as reception of objects between the teeth. The proprioception in the jaws is very very sensitive.

32
Q

What is the difference between the proprioception between people with and without dentures?

A

People with dentures usually lack the periodontal mechanoreceptors meaning they have an altered sensation of objects in the mouth. Also they, dentures usually cover oral mucosa, which further impairs the perception of intra oral forces. Furthermore, considerable motor learning may be required to adapt to use of dentures for speech and mastication

33
Q

What is a motor unit?

A

It is the functional unit of the muscle that signals for muscle activation. It has a variable area of action depending on the size of the single motor unit and the amount. Large motor units on large muscles are able to effect large muscle while small motor units can affect the eyes.

34
Q

What are the three types of motor units?

A
  1. Slow twitch (type I) - are slow twitch, low force and fatigue resistant – mostly present in masseter muscle for example – tbh in nearly all muscle of mastication
  2. Fast twitch-fatigue resistant (type II a) - are fast twitch, moderate force, fatigue resistant
  3. Fast twitch (type II b) - are fast twitch, high force, fast fatigue
35
Q

What are the two ways we can increase force in the muscle?

A
  1. Recruitment - involvement of new motor neurons

2. Rate of coding – increase in frequency of action potential discharge

36
Q

What is the hierarchy of motor control?

A
  1. Highest level – planning – development of strategies and motor plans to achieve the goal – cortical association areas, basal ganglia, cerebellum
  2. Middle level – commanding – integration of signals from higher areas to deliver specific commands – motor cortex and brainstem descending pathways
  3. Lowest level – execution – integration of sensory afferent and descending pathways – spinal interneurons and motoneurons
37
Q

What is mastication?

A

It is a rhythmic activation of jaw muscles in a highly coordinated manner. It requires constant conscious effort and monitoring not required.

Dentistry BDS 2 Sem 1 (15 decks)

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